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 <meta property="article:published_time" content="2020-08-19T14:33:24.000Z">
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diff --git a/2020/08/27/Linux-frequently-used-commands/index.html b/2020/08/27/Linux-frequently-used-commands/index.html
index d27fb035..b867bb4b 100644
--- a/2020/08/27/Linux-frequently-used-commands/index.html
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-          <span class="site-state-item-count">48</span>
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   <div class="powered-by">由 <a href="https://hexo.io/" rel="noopener" target="_blank">Hexo</a> & <a href="https://theme-next.js.org/" rel="noopener" target="_blank">NexT.Gemini</a> 强力驱动
diff --git a/2020/09/04/MySQL-frequently-used-commands/index.html b/2020/09/04/MySQL-frequently-used-commands/index.html
index 94596739..600a9570 100644
--- a/2020/09/04/MySQL-frequently-used-commands/index.html
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-          <span class="site-state-item-count">48</span>
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diff --git a/2023/05/27/how-to-install-clash-on-ubuntu/index.html b/2023/05/27/how-to-install-clash-on-ubuntu/index.html
index 2622a0bf..5356d58d 100644
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 <meta property="og:description" content="本文记录了如何在 Ubuntu 上安装 Clash，以供各类程序在必要的时候使用代理。有些时候我们面对特定资源会遇到下载速度极其缓慢甚至无法下载的情况，像是使用 Github，下载 k8s 相关镜像，还有访问特定网站等等。也许有些 Dirty Hack 的方式可以短暂地绕开限制，比如修改 hosts 文件，但这并不总是见效。也许添加国内的镜像仓库地址可以满足很多人的需求，但是说不准就会遇到镜像更新">
 <meta property="og:locale" content="zh_CN">
 <meta property="article:published_time" content="2023-05-27T08:07:01.000Z">
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+<meta property="article:modified_time" content="2024-04-23T18:42:37.599Z">
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-<meta property="article:tag" content="clash">
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@@ -156,7 +156,7 @@
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-          <span class="site-state-item-count">48</span>
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-      <time title="修改时间：2024-04-10 22:49:47" itemprop="dateModified" datetime="2024-04-10T22:49:47+08:00">2024-04-10</time>
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@@ -317,8 +317,8 @@ <h3 id="设置-Clash-开机自动启动"><a href="#设置-Clash-开机自动启
 
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           <div class="post-tags">
-              <a href="/tags/clash/" rel="tag"># clash</a>
               <a href="/tags/proxy/" rel="tag"># proxy</a>
+              <a href="/tags/clash/" rel="tag"># clash</a>
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@@ -363,13 +363,13 @@ <h3 id="设置-Clash-开机自动启动"><a href="#设置-Clash-开机自动启
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-    <span title="站点阅读时长">6:56</span>
+    <span title="站点阅读时长">7:09</span>
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   <div class="powered-by">由 <a href="https://hexo.io/" rel="noopener" target="_blank">Hexo</a> & <a href="https://theme-next.js.org/" rel="noopener" target="_blank">NexT.Gemini</a> 强力驱动
diff --git a/2023/06/07/how-to-setup-OpenVPN-connect-client-on-iOS-and-macOS/index.html b/2023/06/07/how-to-setup-OpenVPN-connect-client-on-iOS-and-macOS/index.html
index 5238b1cb..21ddba26 100644
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@@ -27,10 +27,10 @@
 <meta property="og:description" content="本文记录了如何在 iOS 和 macOS 上安装和配置 OpenVPN 客户端，主要介绍如何编写客户端配置文件 client.ovpn 并导入。">
 <meta property="og:locale" content="zh_CN">
 <meta property="article:published_time" content="2023-06-07T09:04:23.000Z">
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-<meta property="article:tag" content="proxy">
 <meta property="article:tag" content="openvpn">
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@@ -156,7 +156,7 @@
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         <a href="/archives/">
-          <span class="site-state-item-count">48</span>
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       <span class="post-meta-item-text">更新于</span>
-      <time title="修改时间：2024-04-10 22:49:47" itemprop="dateModified" datetime="2024-04-10T22:49:47+08:00">2024-04-10</time>
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@@ -325,8 +325,8 @@ <h2 id="参考文章"><a href="#参考文章" class="headerlink" title="参考
 
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           <div class="post-tags">
-              <a href="/tags/proxy/" rel="tag"># proxy</a>
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+              <a href="/tags/proxy/" rel="tag"># proxy</a>
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   <div class="powered-by">由 <a href="https://hexo.io/" rel="noopener" target="_blank">Hexo</a> & <a href="https://theme-next.js.org/" rel="noopener" target="_blank">NexT.Gemini</a> 强力驱动
diff --git a/2023/06/07/how-to-setup-OpenVPN-server-on-windows-10/index.html b/2023/06/07/how-to-setup-OpenVPN-server-on-windows-10/index.html
index 006e3150..b4ae7ee1 100644
--- a/2023/06/07/how-to-setup-OpenVPN-server-on-windows-10/index.html
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 <meta property="og:description" content="本文记录了如何在 Windows 10 上安装和配置 OpenVPN 服务端。">
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 <meta property="article:published_time" content="2023-06-07T07:18:02.000Z">
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+<meta property="article:modified_time" content="2024-04-23T18:42:37.599Z">
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-<meta property="article:tag" content="proxy">
 <meta property="article:tag" content="openvpn">
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       <div class="site-state-item site-state-posts">
         <a href="/archives/">
-          <span class="site-state-item-count">48</span>
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       <span class="post-meta-item-text">更新于</span>
-      <time title="修改时间：2024-04-10 22:49:47" itemprop="dateModified" datetime="2024-04-10T22:49:47+08:00">2024-04-10</time>
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@@ -308,8 +308,8 @@ <h2 id="参考链接"><a href="#参考链接" class="headerlink" title="参考
 
     <footer class="post-footer">
           <div class="post-tags">
-              <a href="/tags/proxy/" rel="tag"># proxy</a>
               <a href="/tags/openvpn/" rel="tag"># openvpn</a>
+              <a href="/tags/proxy/" rel="tag"># proxy</a>
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   <div class="powered-by">由 <a href="https://hexo.io/" rel="noopener" target="_blank">Hexo</a> & <a href="https://theme-next.js.org/" rel="noopener" target="_blank">NexT.Gemini</a> 强力驱动
diff --git a/2023/06/07/how-to-use-OpenVPN-to-access-home-network/index.html b/2023/06/07/how-to-use-OpenVPN-to-access-home-network/index.html
index 7df4bf23..9df060c4 100644
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-          <span class="site-state-item-count">48</span>
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       <span class="post-meta-item-text">更新于</span>
-      <time title="修改时间：2024-04-10 22:49:47" itemprop="dateModified" datetime="2024-04-10T22:49:47+08:00">2024-04-10</time>
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@@ -334,8 +334,8 @@ <h2 id="参考链接"><a href="#参考链接" class="headerlink" title="参考
 
     <footer class="post-footer">
           <div class="post-tags">
-              <a href="/tags/proxy/" rel="tag"># proxy</a>
               <a href="/tags/openvpn/" rel="tag"># openvpn</a>
+              <a href="/tags/proxy/" rel="tag"># proxy</a>
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@@ -380,13 +380,13 @@ <h2 id="参考链接"><a href="#参考链接" class="headerlink" title="参考
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   <div class="powered-by">由 <a href="https://hexo.io/" rel="noopener" target="_blank">Hexo</a> & <a href="https://theme-next.js.org/" rel="noopener" target="_blank">NexT.Gemini</a> 强力驱动
diff --git a/2023/06/13/how-to-configure-proxy-for-terminal-docker-and-container/index.html b/2023/06/13/how-to-configure-proxy-for-terminal-docker-and-container/index.html
index 1afaa4a6..b01d2737 100644
--- a/2023/06/13/how-to-configure-proxy-for-terminal-docker-and-container/index.html
+++ b/2023/06/13/how-to-configure-proxy-for-terminal-docker-and-container/index.html
@@ -27,7 +27,7 @@
 <meta property="og:description" content="在 Ubuntu 上安装 Clash 后，Clash 通过监听本地的 7890 端口，提供代理服务。但是不同程序设置代理的方式不尽相同，并不是启动了 Clash 以及在某一处设置后，整个系统发出的 HTTP 请求都能经过代理。本文将介绍如何为终端、docker 和容器添加代理。 为终端设置代理有时候，我们需要在终端通过执行命令的方式访问网络和下载资源，比如使用 wget 和 curl。 设置 Sh">
 <meta property="og:locale" content="zh_CN">
 <meta property="article:published_time" content="2023-06-13T14:56:11.000Z">
-<meta property="article:modified_time" content="2024-04-10T14:49:47.851Z">
+<meta property="article:modified_time" content="2024-04-23T18:42:37.599Z">
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 <meta property="article:tag" content="docker">
 <meta property="article:tag" content="proxy">
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@@ -362,13 +362,13 @@ <h2 id="参考链接"><a href="#参考链接" class="headerlink" title="参考
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+    <span title="站点阅读时长">7:09</span>
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index 507282d7..ec615af6 100644
--- a/2023/06/23/how-to-install-Minikube-on-Ubuntu-20-04/index.html
+++ b/2023/06/23/how-to-install-Minikube-on-Ubuntu-20-04/index.html
@@ -27,7 +27,7 @@
 <meta property="og:description" content="环境搭建安装 Ubuntu 20.04使用 Vmware Workstation 通过 ubuntu-20.04.6-live-server-amd64.iso 安装。需要满足条件如下：  2 个或更多 CPU（2 CPU）。 2GB 可用内存（4GB）。 20GB 可用磁盘空间（30GB）。 网络连接 容器或虚拟机管理器（Docker）。  安装 Docker参考官方文档：Install Doc">
 <meta property="og:locale" content="zh_CN">
 <meta property="article:published_time" content="2023-06-23T13:04:20.000Z">
-<meta property="article:modified_time" content="2024-04-10T14:49:47.851Z">
+<meta property="article:modified_time" content="2024-04-23T18:42:37.599Z">
 <meta property="article:author" content="Moralok">
 <meta property="article:tag" content="minikube">
 <meta property="article:tag" content="k8s">
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-          <span class="site-state-item-count">48</span>
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@@ -372,13 +372,13 @@ <h2 id="参考链接"><a href="#参考链接" class="headerlink" title="参考
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+    <span title="站点阅读时长">7:09</span>
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   <div class="powered-by">由 <a href="https://hexo.io/" rel="noopener" target="_blank">Hexo</a> & <a href="https://theme-next.js.org/" rel="noopener" target="_blank">NexT.Gemini</a> 强力驱动
diff --git a/2023/06/24/Ubuntu-server-20-04-not-all-disk-space-was-allocated-after-installation/index.html b/2023/06/24/Ubuntu-server-20-04-not-all-disk-space-was-allocated-after-installation/index.html
index 1eb2cda9..c5266ff9 100644
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+++ b/2023/06/24/Ubuntu-server-20-04-not-all-disk-space-was-allocated-after-installation/index.html
@@ -27,7 +27,7 @@
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 <meta property="og:locale" content="zh_CN">
 <meta property="article:published_time" content="2023-06-24T16:04:43.000Z">
-<meta property="article:modified_time" content="2024-04-10T14:49:47.851Z">
+<meta property="article:modified_time" content="2024-04-23T18:42:37.599Z">
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 <meta property="article:tag" content="linux">
 <meta property="article:tag" content="ubuntu">
@@ -156,7 +156,7 @@
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         <a href="/archives/">
-          <span class="site-state-item-count">48</span>
+          <span class="site-state-item-count">49</span>
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-      <time title="修改时间：2024-04-10 22:49:47" itemprop="dateModified" datetime="2024-04-10T22:49:47+08:00">2024-04-10</time>
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@@ -333,13 +333,13 @@ <h2 id="参考链接"><a href="#参考链接" class="headerlink" title="参考
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   <div class="powered-by">由 <a href="https://hexo.io/" rel="noopener" target="_blank">Hexo</a> & <a href="https://theme-next.js.org/" rel="noopener" target="_blank">NexT.Gemini</a> 强力驱动
diff --git a/2023/06/28/how-to-use-ssh-to-connect-github-and-server/index.html b/2023/06/28/how-to-use-ssh-to-connect-github-and-server/index.html
index 6c245f9e..3e6e92e0 100644
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@@ -27,7 +27,7 @@
 <meta property="og:description" content="本文介绍了如何使用 SSH 连接 Github 和免密登录服务器作为备忘笔记，主要在新建虚拟机或重装云服务器系统时使用。">
 <meta property="og:locale" content="zh_CN">
 <meta property="article:published_time" content="2023-06-28T20:36:35.000Z">
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+<meta property="article:modified_time" content="2024-04-23T18:42:37.599Z">
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 <meta property="article:tag" content="ssh">
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@@ -155,7 +155,7 @@
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-          <span class="site-state-item-count">48</span>
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-      <time title="修改时间：2024-04-10 22:49:47" itemprop="dateModified" datetime="2024-04-10T22:49:47+08:00">2024-04-10</time>
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@@ -364,13 +364,13 @@ <h2 id="参考链接"><a href="#参考链接" class="headerlink" title="参考
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-    <span title="站点阅读时长">6:56</span>
+    <span title="站点阅读时长">7:09</span>
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 </div>
   <div class="powered-by">由 <a href="https://hexo.io/" rel="noopener" target="_blank">Hexo</a> & <a href="https://theme-next.js.org/" rel="noopener" target="_blank">NexT.Gemini</a> 强力驱动
diff --git a/2023/06/29/tmux-frequently-used-commands/index.html b/2023/06/29/tmux-frequently-used-commands/index.html
index cd85e5cd..6bbfe1af 100644
--- a/2023/06/29/tmux-frequently-used-commands/index.html
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 <meta property="og:description" content="本文记录了 Tmux 常用命令和快捷键作为备忘笔记（好容易忘啊 Orz）。">
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 <meta property="article:published_time" content="2023-06-29T10:44:44.000Z">
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-          <span class="site-state-item-count">48</span>
+          <span class="site-state-item-count">49</span>
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@@ -388,13 +388,13 @@ <h2 id="参考链接"><a href="#参考链接" class="headerlink" title="参考
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   <div class="powered-by">由 <a href="https://hexo.io/" rel="noopener" target="_blank">Hexo</a> & <a href="https://theme-next.js.org/" rel="noopener" target="_blank">NexT.Gemini</a> 强力驱动
diff --git a/2023/07/13/Java-class-loader-source-code-analysis/index.html b/2023/07/13/Java-class-loader-source-code-analysis/index.html
index 9ff072c6..0c19d2df 100644
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@@ -27,7 +27,7 @@
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 <meta property="og:locale" content="zh_CN">
 <meta property="article:published_time" content="2023-07-13T20:08:11.000Z">
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+<meta property="article:modified_time" content="2024-04-23T18:42:37.599Z">
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-          <span class="site-state-item-count">48</span>
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+    <span title="站点阅读时长">7:09</span>
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   <div class="powered-by">由 <a href="https://hexo.io/" rel="noopener" target="_blank">Hexo</a> & <a href="https://theme-next.js.org/" rel="noopener" target="_blank">NexT.Gemini</a> 强力驱动
diff --git a/2023/08/04/Spring-application-context-refresh-process/index.html b/2023/08/04/Spring-application-context-refresh-process/index.html
index b33fff3e..e65b593c 100644
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-<meta property="article:modified_time" content="2024-04-10T14:49:47.851Z">
+<meta property="article:modified_time" content="2024-04-23T18:42:37.599Z">
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 <meta property="article:tag" content="java">
 <meta property="article:tag" content="spring">
@@ -159,7 +159,7 @@
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         <a href="/archives/">
-          <span class="site-state-item-count">48</span>
+          <span class="site-state-item-count">49</span>
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-    <span title="站点阅读时长">6:56</span>
+    <span title="站点阅读时长">7:09</span>
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   <div class="powered-by">由 <a href="https://hexo.io/" rel="noopener" target="_blank">Hexo</a> & <a href="https://theme-next.js.org/" rel="noopener" target="_blank">NexT.Gemini</a> 强力驱动
diff --git a/2023/08/10/how-does-Spring-load-beans/index.html b/2023/08/10/how-does-Spring-load-beans/index.html
index 886ef770..d6e272c6 100644
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   <div class="powered-by">由 <a href="https://hexo.io/" rel="noopener" target="_blank">Hexo</a> & <a href="https://theme-next.js.org/" rel="noopener" target="_blank">NexT.Gemini</a> 强力驱动
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index e70e22cc..22d683ef 100644
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diff --git a/2023/12/06/custom-starter-and-auto-configuration-in-Spring-Boot/index.html b/2023/12/06/custom-starter-and-auto-configuration-in-Spring-Boot/index.html
index 70903d6c..1a78c0c8 100644
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diff --git a/2023/12/06/how-does-Spring-Boot-SPI-works/index.html b/2023/12/06/how-does-Spring-Boot-SPI-works/index.html
index 769aaeaa..0344188d 100644
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   <div class="powered-by">由 <a href="https://hexo.io/" rel="noopener" target="_blank">Hexo</a> & <a href="https://theme-next.js.org/" rel="noopener" target="_blank">NexT.Gemini</a> 强力驱动
diff --git a/2023/12/07/use-and-analysis-of-PropertySource-annotation-in-Spring/index.html b/2023/12/07/use-and-analysis-of-PropertySource-annotation-in-Spring/index.html
index db45033f..59915ca7 100644
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 <meta property="article:published_time" content="2023-12-07T03:55:49.000Z">
-<meta property="article:modified_time" content="2024-04-10T14:49:47.883Z">
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 <meta property="article:tag" content="spring">
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-          <span class="site-state-item-count">48</span>
+          <span class="site-state-item-count">49</span>
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@@ -382,13 +382,13 @@ <h3 id="添加属性源到-Environment"><a href="#添加属性源到-Environment
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-    <span title="站点阅读时长">6:56</span>
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   <div class="powered-by">由 <a href="https://hexo.io/" rel="noopener" target="_blank">Hexo</a> & <a href="https://theme-next.js.org/" rel="noopener" target="_blank">NexT.Gemini</a> 强力驱动
diff --git a/2023/12/08/source-code-analysis-of-AutowiredAnnotationBeanPostProcessor-in-Spring/index.html b/2023/12/08/source-code-analysis-of-AutowiredAnnotationBeanPostProcessor-in-Spring/index.html
index 622f5f11..5cf66f66 100644
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+++ b/2023/12/08/source-code-analysis-of-AutowiredAnnotationBeanPostProcessor-in-Spring/index.html
@@ -27,7 +27,7 @@
 <meta property="og:description" content="在 Spring 中，AutowiredAnnotationBeanPostProcessor 是一个非常重要的后处理器，它可以自动装配标注注解的字段和方法，默认使用 @Autowired 和 @Value 注解，可以支持 JSR-330 的 @Inject 注解。本文通过分析源码介绍它的调用时机和工作原理。">
 <meta property="og:locale" content="zh_CN">
 <meta property="article:published_time" content="2023-12-08T04:00:30.000Z">
-<meta property="article:modified_time" content="2024-04-10T14:49:47.883Z">
+<meta property="article:modified_time" content="2024-04-23T18:42:37.627Z">
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 <meta property="article:tag" content="spring">
@@ -156,7 +156,7 @@
   <nav class="site-state">
       <div class="site-state-item site-state-posts">
         <a href="/archives/">
-          <span class="site-state-item-count">48</span>
+          <span class="site-state-item-count">49</span>
           <span class="site-state-item-name">日志</span>
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@@ -230,7 +230,7 @@ <h1 class="post-title" itemprop="name headline">
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@@ -425,13 +425,13 @@ <h4 id="检测配置成员"><a href="#检测配置成员" class="headerlink" tit
     <span class="post-meta-item-icon">
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-    <span title="站点阅读时长">6:56</span>
+    <span title="站点阅读时长">7:09</span>
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   <div class="powered-by">由 <a href="https://hexo.io/" rel="noopener" target="_blank">Hexo</a> & <a href="https://theme-next.js.org/" rel="noopener" target="_blank">NexT.Gemini</a> 强力驱动
diff --git a/2023/12/10/is-it-necessary-to-use-ConfigurationProperties-with-EnableConfigurationProperties/index.html b/2023/12/10/is-it-necessary-to-use-ConfigurationProperties-with-EnableConfigurationProperties/index.html
index f98953f9..8841d724 100644
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@@ -27,7 +27,7 @@
 <meta property="og:description" content="@ConfigurationProperties 和 @EnableConfigurationProperties 是 Spring Boot 中常用的注解，提供了方便和强大的外部化配置支持。尽管它们常常一起出现，但是它们真的必须一起使用吗？Spring Boot 的灵活性常常让我们忽略配置背后产生的作用究竟是什么？本文将从源码角度出发分析两个注解的作用时机和工作原理。">
 <meta property="og:locale" content="zh_CN">
 <meta property="article:published_time" content="2023-12-10T03:41:00.000Z">
-<meta property="article:modified_time" content="2024-04-10T14:49:47.883Z">
+<meta property="article:modified_time" content="2024-04-23T18:42:37.627Z">
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 <meta property="article:tag" content="java">
 <meta property="article:tag" content="spring">
@@ -157,7 +157,7 @@
   <nav class="site-state">
       <div class="site-state-item site-state-posts">
         <a href="/archives/">
-          <span class="site-state-item-count">48</span>
+          <span class="site-state-item-count">49</span>
           <span class="site-state-item-name">日志</span>
         </a>
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@@ -231,7 +231,7 @@ <h1 class="post-title" itemprop="name headline">
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-      <time title="修改时间：2024-04-10 22:49:47" itemprop="dateModified" datetime="2024-04-10T22:49:47+08:00">2024-04-10</time>
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@@ -370,13 +370,13 @@ <h2 id="总结"><a href="#总结" class="headerlink" title="总结"></a>总结</
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   <div class="powered-by">由 <a href="https://hexo.io/" rel="noopener" target="_blank">Hexo</a> & <a href="https://theme-next.js.org/" rel="noopener" target="_blank">NexT.Gemini</a> 强力驱动
diff --git a/2023/12/11/the-truth-about-override-of-ComponentScan-basePackages/index.html b/2023/12/11/the-truth-about-override-of-ComponentScan-basePackages/index.html
index 572f2123..bd01eaad 100644
--- a/2023/12/11/the-truth-about-override-of-ComponentScan-basePackages/index.html
+++ b/2023/12/11/the-truth-about-override-of-ComponentScan-basePackages/index.html
@@ -27,7 +27,7 @@
 <meta property="og:description" content="@ComponentScan 注解是 Spring 中很常用的注解，用于扫描并加载指定类路径下的 Bean，而 Spring Boot 为了便捷使用 @SpringBootApplication 组合注解集成了 @ComponentScan 的能力。也许你听说过使用后者会覆盖前者中关于包扫描的设置，但你是否质疑过这个“不合常理”的结论？是否好奇过为什么它们不像其他注解在嵌套使用时可以同时生效？又是">
 <meta property="og:locale" content="zh_CN">
 <meta property="article:published_time" content="2023-12-11T02:11:22.000Z">
-<meta property="article:modified_time" content="2024-04-10T14:49:47.883Z">
+<meta property="article:modified_time" content="2024-04-23T18:42:37.627Z">
 <meta property="article:author" content="Moralok">
 <meta property="article:tag" content="java">
 <meta property="article:tag" content="spring">
@@ -157,7 +157,7 @@
   <nav class="site-state">
       <div class="site-state-item site-state-posts">
         <a href="/archives/">
-          <span class="site-state-item-count">48</span>
+          <span class="site-state-item-count">49</span>
           <span class="site-state-item-name">日志</span>
         </a>
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@@ -231,7 +231,7 @@ <h1 class="post-title" itemprop="name headline">
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@@ -425,13 +425,13 @@ <h2 id="总结"><a href="#总结" class="headerlink" title="总结"></a>总结</
     <span class="post-meta-item-icon">
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-    <span title="站点阅读时长">6:56</span>
+    <span title="站点阅读时长">7:09</span>
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   <div class="powered-by">由 <a href="https://hexo.io/" rel="noopener" target="_blank">Hexo</a> & <a href="https://theme-next.js.org/" rel="noopener" target="_blank">NexT.Gemini</a> 强力驱动
diff --git a/2023/12/13/how-to-grant-when-MySQL-started-with-skip-name-resolve-mode/index.html b/2023/12/13/how-to-grant-when-MySQL-started-with-skip-name-resolve-mode/index.html
index 63ff79d1..798f3fc3 100644
--- a/2023/12/13/how-to-grant-when-MySQL-started-with-skip-name-resolve-mode/index.html
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@@ -27,7 +27,7 @@
 <meta property="og:description" content="本文介绍了 MySQL 中 skip-name-resolve 参数对连接的优化作用，随之而来的权限表仅可使用 IP 的限制，以及如何在无法提前确定 IP 的情况下使用 grant 命令搭配通配符 % 进行授权。">
 <meta property="og:locale" content="zh_CN">
 <meta property="article:published_time" content="2023-12-13T04:16:17.000Z">
-<meta property="article:modified_time" content="2024-04-10T14:49:47.883Z">
+<meta property="article:modified_time" content="2024-04-23T18:42:37.627Z">
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 <meta name="twitter:card" content="summary">
@@ -155,7 +155,7 @@
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 <meta property="article:tag" content="linux">
 <meta property="article:tag" content="vim">
@@ -156,7 +156,7 @@
   <nav class="site-state">
       <div class="site-state-item site-state-posts">
         <a href="/archives/">
-          <span class="site-state-item-count">48</span>
+          <span class="site-state-item-count">49</span>
           <span class="site-state-item-name">日志</span>
         </a>
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@@ -230,7 +230,7 @@ <h1 class="post-title" itemprop="name headline">
         <i class="far fa-calendar-check"></i>
       </span>
       <span class="post-meta-item-text">更新于</span>
-      <time title="修改时间：2024-04-10 22:49:47" itemprop="dateModified" datetime="2024-04-10T22:49:47+08:00">2024-04-10</time>
+      <time title="修改时间：2024-04-24 02:42:37" itemprop="dateModified" datetime="2024-04-24T02:42:37+08:00">2024-04-24</time>
     </span>
 
   
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     <span class="post-meta-item-icon">
       <i class="fa fa-chart-line"></i>
     </span>
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+    <span title="站点总字数">129k</span>
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-    <span title="站点阅读时长">6:56</span>
+    <span title="站点阅读时长">7:09</span>
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   <div class="powered-by">由 <a href="https://hexo.io/" rel="noopener" target="_blank">Hexo</a> & <a href="https://theme-next.js.org/" rel="noopener" target="_blank">NexT.Gemini</a> 强力驱动
diff --git a/2024/01/30/installation-and-use-of-k3s/index.html b/2024/01/30/installation-and-use-of-k3s/index.html
index d53092c3..eab4980a 100644
--- a/2024/01/30/installation-and-use-of-k3s/index.html
+++ b/2024/01/30/installation-and-use-of-k3s/index.html
@@ -27,7 +27,7 @@
 <meta property="og:description" content="本文记录了 k3s 的安装和使用，相较于 minikube，前者是一个完全兼容的 Kubernetes 发行版，安装和使用的体验更佳。">
 <meta property="og:locale" content="zh_CN">
 <meta property="article:published_time" content="2024-01-30T11:45:23.000Z">
-<meta property="article:modified_time" content="2024-04-10T14:49:47.895Z">
+<meta property="article:modified_time" content="2024-04-23T18:42:37.635Z">
 <meta property="article:author" content="Moralok">
 <meta property="article:tag" content="k8s">
 <meta property="article:tag" content="k3s">
@@ -143,7 +143,7 @@
       <div class="sidebar-panel-container">
         <!--noindex-->
         <div class="post-toc-wrap sidebar-panel">
-            <div class="post-toc animated"><ol class="nav"><li class="nav-item nav-level-2"><a class="nav-link" href="#%E5%AE%89%E8%A3%85"><span class="nav-number">1.</span> <span class="nav-text">安装</span></a><ol class="nav-child"><li class="nav-item nav-level-3"><a class="nav-link" href="#%E6%AD%A5%E9%AA%A4"><span class="nav-number">1.1.</span> <span class="nav-text">步骤</span></a></li><li class="nav-item nav-level-3"><a class="nav-link" href="#%E9%85%8D%E7%BD%AE%E6%96%87%E4%BB%B6%E6%9D%83%E9%99%90%E9%97%AE%E9%A2%98"><span class="nav-number">1.2.</span> <span class="nav-text">配置文件权限问题</span></a><ol class="nav-child"><li class="nav-item nav-level-4"><a class="nav-link" href="#%E4%BF%AE%E6%94%B9%E5%90%AF%E5%8A%A8%E5%8F%82%E6%95%B0"><span class="nav-number">1.2.1.</span> <span class="nav-text">修改启动参数</span></a></li><li class="nav-item nav-level-4"><a class="nav-link" href="#%E4%BF%AE%E6%94%B9%E7%8E%AF%E5%A2%83%E5%8F%98%E9%87%8F"><span class="nav-number">1.2.2.</span> <span class="nav-text">修改环境变量</span></a></li><li class="nav-item nav-level-4"><a class="nav-link" href="#%E4%BF%AE%E6%94%B9%E9%85%8D%E7%BD%AE%E6%96%87%E4%BB%B6%E8%B7%AF%E5%BE%84"><span class="nav-number">1.2.3.</span> <span class="nav-text">修改配置文件路径</span></a></li></ol></li><li class="nav-item nav-level-3"><a class="nav-link" href="#%E9%85%8D%E7%BD%AE%E4%BB%A3%E7%90%86"><span class="nav-number">1.3.</span> <span class="nav-text">配置代理</span></a></li></ol></li><li class="nav-item nav-level-2"><a class="nav-link" href="#%E4%BD%BF%E7%94%A8"><span class="nav-number">2.</span> <span class="nav-text">使用</span></a><ol class="nav-child"><li class="nav-item nav-level-3"><a class="nav-link" href="#%E5%88%9B%E5%BB%BA-Deployment"><span class="nav-number">2.1.</span> <span class="nav-text">创建 Deployment</span></a></li><li class="nav-item nav-level-3"><a class="nav-link" href="#%E5%88%9B%E5%BB%BA-Service"><span class="nav-number">2.2.</span> <span class="nav-text">创建 Service</span></a></li><li class="nav-item nav-level-3"><a class="nav-link" href="#%E6%B8%85%E7%90%86"><span class="nav-number">2.3.</span> <span class="nav-text">清理</span></a></li></ol></li><li class="nav-item nav-level-2"><a class="nav-link" href="#%E5%8F%82%E8%80%83%E6%96%87%E7%AB%A0"><span class="nav-number">3.</span> <span class="nav-text">参考文章</span></a></li></ol></div>
+            <div class="post-toc animated"><ol class="nav"><li class="nav-item nav-level-2"><a class="nav-link" href="#%E5%AE%89%E8%A3%85"><span class="nav-number">1.</span> <span class="nav-text">安装</span></a><ol class="nav-child"><li class="nav-item nav-level-3"><a class="nav-link" href="#%E6%AD%A5%E9%AA%A4"><span class="nav-number">1.1.</span> <span class="nav-text">步骤</span></a></li><li class="nav-item nav-level-3"><a class="nav-link" href="#%E9%85%8D%E7%BD%AE%E6%96%87%E4%BB%B6%E6%9D%83%E9%99%90%E9%97%AE%E9%A2%98"><span class="nav-number">1.2.</span> <span class="nav-text">配置文件权限问题</span></a><ol class="nav-child"><li class="nav-item nav-level-4"><a class="nav-link" href="#%E4%BF%AE%E6%94%B9%E5%90%AF%E5%8A%A8%E5%8F%82%E6%95%B0"><span class="nav-number">1.2.1.</span> <span class="nav-text">修改启动参数</span></a></li><li class="nav-item nav-level-4"><a class="nav-link" href="#%E4%BF%AE%E6%94%B9%E7%8E%AF%E5%A2%83%E5%8F%98%E9%87%8F"><span class="nav-number">1.2.2.</span> <span class="nav-text">修改环境变量</span></a></li><li class="nav-item nav-level-4"><a class="nav-link" href="#%E4%BF%AE%E6%94%B9%E9%85%8D%E7%BD%AE%E6%96%87%E4%BB%B6%E8%B7%AF%E5%BE%84"><span class="nav-number">1.2.3.</span> <span class="nav-text">修改配置文件路径</span></a></li></ol></li><li class="nav-item nav-level-3"><a class="nav-link" href="#%E9%85%8D%E7%BD%AE%E4%BB%A3%E7%90%86"><span class="nav-number">1.3.</span> <span class="nav-text">配置代理</span></a></li></ol></li><li class="nav-item nav-level-2"><a class="nav-link" href="#%E4%BD%BF%E7%94%A8"><span class="nav-number">2.</span> <span class="nav-text">使用</span></a><ol class="nav-child"><li class="nav-item nav-level-3"><a class="nav-link" href="#%E5%88%9B%E5%BB%BA-Deployment"><span class="nav-number">2.1.</span> <span class="nav-text">创建 Deployment</span></a></li><li class="nav-item nav-level-3"><a class="nav-link" href="#%E5%88%9B%E5%BB%BA-Service"><span class="nav-number">2.2.</span> <span class="nav-text">创建 Service</span></a></li><li class="nav-item nav-level-3"><a class="nav-link" href="#%E6%B8%85%E7%90%86"><span class="nav-number">2.3.</span> <span class="nav-text">清理</span></a></li></ol></li><li class="nav-item nav-level-2"><a class="nav-link" href="#%E5%8D%B8%E8%BD%BD"><span class="nav-number">3.</span> <span class="nav-text">卸载</span></a></li><li class="nav-item nav-level-2"><a class="nav-link" href="#%E5%8F%82%E8%80%83%E6%96%87%E7%AB%A0"><span class="nav-number">4.</span> <span class="nav-text">参考文章</span></a></li></ol></div>
         </div>
         <!--/noindex-->
 
@@ -156,7 +156,7 @@
   <nav class="site-state">
       <div class="site-state-item site-state-posts">
         <a href="/archives/">
-          <span class="site-state-item-count">48</span>
+          <span class="site-state-item-count">49</span>
           <span class="site-state-item-name">日志</span>
         </a>
       </div>
@@ -230,7 +230,7 @@ <h1 class="post-title" itemprop="name headline">
         <i class="far fa-calendar-check"></i>
       </span>
       <span class="post-meta-item-text">更新于</span>
-      <time title="修改时间：2024-04-10 22:49:47" itemprop="dateModified" datetime="2024-04-10T22:49:47+08:00">2024-04-10</time>
+      <time title="修改时间：2024-04-24 02:42:37" itemprop="dateModified" datetime="2024-04-24T02:42:37+08:00">2024-04-24</time>
     </span>
 
   
@@ -328,6 +328,9 @@ <h3 id="清理"><a href="#清理" class="headerlink" title="清理"></a>清理</
 <li>删除 <code>Service</code>：<figure class="highlight shell"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">kubectl delete service hello-node</span><br></pre></td></tr></table></figure></li>
 <li>删除 <code>Deployment</code>：<figure class="highlight shell"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">kubectl delete deployment hello-node</span><br></pre></td></tr></table></figure></li>
 </ol>
+<h2 id="卸载"><a href="#卸载" class="headerlink" title="卸载"></a>卸载</h2><ol>
+<li>从 server 节点卸载 k3s<figure class="highlight plaintext"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">/usr/local/bin/k3s-uninstall.sh</span><br></pre></td></tr></table></figure></li>
+</ol>
 <h2 id="参考文章"><a href="#参考文章" class="headerlink" title="参考文章"></a>参考文章</h2><ul>
 <li><a target="_blank" rel="noopener" href="https://docs.k3s.io/zh/quick-start">快速入门指南</a></li>
 <li><a target="_blank" rel="noopener" href="https://docs.k3s.io/zh/cli/server#%E7%AE%A1%E7%90%86-kubeconfig-%E9%80%89%E9%A1%B9">管理 Kubeconfig 选项</a></li>
@@ -359,6 +362,9 @@ <h2 id="参考文章"><a href="#参考文章" class="headerlink" title="参考
                 </a>
             </div>
             <div class="post-nav-item">
+                <a href="/2024/03/11/representating-and-manipulating-information/" rel="next" title="信息的表示和处理">
+                  信息的表示和处理 <i class="fa fa-angle-right"></i>
+                </a>
             </div>
           </div>
     </footer>
@@ -389,13 +395,13 @@ <h2 id="参考文章"><a href="#参考文章" class="headerlink" title="参考
     <span class="post-meta-item-icon">
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+    <span title="站点总字数">129k</span>
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     <span class="post-meta-item-icon">
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-    <span title="站点阅读时长">6:56</span>
+    <span title="站点阅读时长">7:09</span>
   </span>
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   <div class="powered-by">由 <a href="https://hexo.io/" rel="noopener" target="_blank">Hexo</a> & <a href="https://theme-next.js.org/" rel="noopener" target="_blank">NexT.Gemini</a> 强力驱动
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+            <div class="post-toc animated"><ol class="nav"><li class="nav-item nav-level-2"><a class="nav-link" href="#%E4%BF%A1%E6%81%AF%E5%AD%98%E5%82%A8"><span class="nav-number">1.</span> <span class="nav-text">信息存储</span></a><ol class="nav-child"><li class="nav-item nav-level-3"><a class="nav-link" href="#%E5%8D%81%E5%85%AD%E8%BF%9B%E5%88%B6%E8%A1%A8%E7%A4%BA%E6%B3%95"><span class="nav-number">1.1.</span> <span class="nav-text">十六进制表示法</span></a></li><li class="nav-item nav-level-3"><a class="nav-link" href="#%E5%AD%97%E6%95%B0%E6%8D%AE%E5%A4%A7%E5%B0%8F"><span class="nav-number">1.2.</span> <span class="nav-text">字数据大小</span></a></li><li class="nav-item nav-level-3"><a class="nav-link" href="#%E5%AF%BB%E5%9D%80%E5%92%8C%E5%AD%97%E8%8A%82%E9%A1%BA%E5%BA%8F"><span class="nav-number">1.3.</span> <span class="nav-text">寻址和字节顺序</span></a></li><li class="nav-item nav-level-3"><a class="nav-link" href="#%E8%A1%A8%E7%A4%BA%E5%AD%97%E7%AC%A6%E4%B8%B2"><span class="nav-number">1.4.</span> <span class="nav-text">表示字符串</span></a></li><li class="nav-item nav-level-3"><a class="nav-link" href="#%E8%A1%A8%E7%A4%BA%E4%BB%A3%E7%A0%81"><span class="nav-number">1.5.</span> <span class="nav-text">表示代码</span></a></li><li class="nav-item nav-level-3"><a class="nav-link" href="#%E5%B8%83%E5%B0%94%E4%BB%A3%E6%95%B0%E7%AE%80%E4%BB%8B"><span class="nav-number">1.6.</span> <span class="nav-text">布尔代数简介</span></a></li><li class="nav-item nav-level-3"><a class="nav-link" href="#C%E8%AF%AD%E8%A8%80%E4%B8%AD%E7%9A%84%E5%B8%83%E5%B0%94%E8%BF%90%E7%AE%97"><span class="nav-number">1.7.</span> <span class="nav-text">C语言中的布尔运算</span></a></li><li class="nav-item nav-level-3"><a class="nav-link" href="#C%E8%AF%AD%E8%A8%80%E4%B8%AD%E7%9A%84%E7%A7%BB%E4%BD%8D%E8%BF%90%E7%AE%97"><span class="nav-number">1.8.</span> <span class="nav-text">C语言中的移位运算</span></a></li></ol></li><li class="nav-item nav-level-2"><a class="nav-link" href="#%E6%95%B4%E6%95%B0%E8%A1%A8%E7%A4%BA"><span class="nav-number">2.</span> <span class="nav-text">整数表示</span></a><ol class="nav-child"><li class="nav-item nav-level-3"><a class="nav-link" href="#%E6%95%B4%E5%9E%8B%E6%95%B0%E6%8D%AE%E7%B1%BB%E5%9E%8B"><span class="nav-number">2.1.</span> <span class="nav-text">整型数据类型</span></a></li><li class="nav-item nav-level-3"><a class="nav-link" href="#%E6%97%A0%E7%AC%A6%E5%8F%B7%E6%95%B0%E7%9A%84%E7%BC%96%E7%A0%81"><span class="nav-number">2.2.</span> <span class="nav-text">无符号数的编码</span></a></li></ol></li><li class="nav-item nav-level-2"><a class="nav-link" href="#%E5%8F%82%E8%80%83%E6%96%87%E7%AB%A0"><span class="nav-number">3.</span> <span class="nav-text">参考文章</span></a></li></ol></div>
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+    <span id="/2024/03/11/representating-and-manipulating-information/" class="post-meta-item leancloud_visitors" data-flag-title="信息的表示和处理" title="阅读次数">
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+      <span class="post-meta-item-text">本文字数：</span>
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+      <span class="post-meta-item-text">阅读时长 &asymp;</span>
+      <span>14 分钟</span>
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+</div>
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+      </header>
+
+    
+    
+    
+    <div class="post-body" itemprop="articleBody"><p>(0 &amp; 1) + interpretation = everything.</p>
+<span id="more"></span>
+
+<p>现代计算机存储和处理的信息以<strong>二值信号</strong>表示。二值信号能够<strong>很容易地被表示、存储和传输</strong>。当把位（bit）组合在一起，再加上某种解释（interpretation），即赋予不同的可能位模式以含义，我们就<strong>能够表示任何有限集合的元素</strong>。</p>
+<blockquote>
+<p>“很容易地被表示、存储和传输” =&gt; 高低电压。</p>
+</blockquote>
+<p>通过研究数字的实际表示，我们能够了解<strong>可以表示的值的范围</strong>和<strong>不同算术运算的属性</strong>。为了使编写的程序能在全部数值范围内正确工作，而且具有跨越不同机器、操作系统和编译器组合的可移植性，了解这种属性是非常重要的。大量计算机的安全漏洞都是由于计算机算术运算的微妙细节引发的。在早期，当人们碰巧触发了程序漏洞，只会给人们带来一些不便，但是现在，有众多的黑客企图利用他们能找到的任何漏洞，不经过授权就进入他人的系统。这就要求<strong>程序员有更多的责任和义务，去了解他们的程序如何工作，以及如何被迫产生不良的行为</strong>。</p>
+<blockquote>
+<p>研究的目的。<br>不仅仅需要正向地去了解如何让程序正确地工作，也要反向地去了解如何迫使程序产生不良的行为，这可以更好地帮助理解底层的工作原理。</p>
+</blockquote>
+<p>从编码的基本定义开始，然后得出一些属性，例如可表示的数字的范围、它们的位级表示以及算术运算的属性。<strong>从这样一个抽象的观点来分析是很重要的</strong>，因为程序员需要对计算机运算与更为人熟悉的整数和实数运算之间的关系有清晰的理解。</p>
+<blockquote>
+<p>不仅仅需要了解当前的设计是怎么样的，还要了解为什么这样设计，分开看待具体和抽象。</p>
+</blockquote>
+<h2 id="信息存储"><a href="#信息存储" class="headerlink" title="信息存储"></a>信息存储</h2><p>大多数计算机使用8位的块，或者称为<strong>字节（byte），作为最小的可寻址的内存单位</strong>，而不是访问内存中单独的位。机器级程序将内存视为一个非常大的字节数组，称为<strong>虚拟内存</strong>（virtual memory）。内存的每个字节都由一个唯一的数字来标识，称为它的<strong>地址</strong>（address），所有可能地址的集合就称为<strong>虚拟地址空间</strong>（virtual address space）。</p>
+<p>编译器和运行时系统将存储器空间划分为更可管理的单元，来存放不同的<strong>程序对象</strong>（program object），即程序数据、指令和控制信息。每个程序对象可以简单地视为一个字节块，而程序本身就是一个字节序列。</p>
+<blockquote>
+<p>也许是因为无处不在的局部性原理，在计算机中，很多时候“最小”指向的是一个“连续的块”而非“不可分割的点”。<br>“非常大的字节数组” =&gt; 非常重要的一种视角。</p>
+</blockquote>
+<h3 id="十六进制表示法"><a href="#十六进制表示法" class="headerlink" title="十六进制表示法"></a>十六进制表示法</h3><p>一个字节由8位组成。二进制表示法太冗长，而十进制表示法与位模式的互相转化很麻烦，替代的方法是，以16为基数，或者叫做<strong>十六进制</strong>（hexadecimal，简写为 hex）数，来表示位模式。</p>
+<table>
+<thead>
+<tr>
+<th>十进制</th>
+<th>0</th>
+<th>1</th>
+<th>2</th>
+<th>3</th>
+<th>4</th>
+<th>5</th>
+<th>6</th>
+<th>7</th>
+<th>8</th>
+<th>9</th>
+<th>10</th>
+<th>11</th>
+<th>12</th>
+<th>13</th>
+<th>14</th>
+<th>15</th>
+</tr>
+</thead>
+<tbody><tr>
+<td>十六进制</td>
+<td>0</td>
+<td>1</td>
+<td>2</td>
+<td>3</td>
+<td>4</td>
+<td>5</td>
+<td>6</td>
+<td>7</td>
+<td>8</td>
+<td>9</td>
+<td>A</td>
+<td>B</td>
+<td>C</td>
+<td>D</td>
+<td>E</td>
+<td>F</td>
+</tr>
+<tr>
+<td>二进制</td>
+<td>0000</td>
+<td>0001</td>
+<td>0010</td>
+<td>0011</td>
+<td>0100</td>
+<td>0101</td>
+<td>0110</td>
+<td>0111</td>
+<td>1000</td>
+<td>1001</td>
+<td>1010</td>
+<td>1011</td>
+<td>1100</td>
+<td>1101</td>
+<td>1110</td>
+<td>1111</td>
+</tr>
+</tbody></table>
+<blockquote>
+<p>十六进制 =&gt; 优秀的替代品。</p>
+</blockquote>
+<h3 id="字数据大小"><a href="#字数据大小" class="headerlink" title="字数据大小"></a>字数据大小</h3><p>每台计算机都有一个<strong>字长</strong>（word size），指明指针数据的标称大小（nominal size）。因为虚拟地址是以这样的一个字来编码的，所以<strong>字长决定的最重要的系统参数就是虚拟地址空间的最大大小</strong>。对于一个字长为w位的机器而言，虚拟地址的范围为0~2^w-1，程序最多访问2^w个字节。32位字长限制虚拟地址空间为4GB，64位字长限制虚拟地址空间为16EB。<br>大多数64位机器也可以运行为32位机器编译的程序，这是一种向后兼容。“32位机器”和“64位机器”区别在于该程序是如何编译的，而不是其运行的机器类型。</p>
+<blockquote>
+<p>字长和虚拟地址空间的最大大小不能完全一概而论。字长是指处理器一次能够处理的二进制数据位数，通常<strong>地址总线</strong>的位数与之保持一致，以保证一次性读取完整的数据并充分发挥寻址能力。但是现代计算机可能采用不同的位数以实现更高的性能和灵活性。</p>
+</blockquote>
+<p>基本C语言数据类型的典型大小（以字节为单位），分配的字节数受程序是如何编译的影响而变化。</p>
+<blockquote>
+<p>字长也会影响数据类型的典型大小。数据总线的位数通常也与字长保持一致，即使读取char类型的数据，CPU也是一次性读取64位的数据再提取8位（这时候小端法似乎更自然）。</p>
+</blockquote>
+<table>
+<thead>
+<tr>
+<th>有符号</th>
+<th>无符号</th>
+<th>32位</th>
+<th>64位</th>
+</tr>
+</thead>
+<tbody><tr>
+<td>[signed] char</td>
+<td>unsigned char</td>
+<td>1</td>
+<td>1</td>
+</tr>
+<tr>
+<td>short</td>
+<td>unsigned short</td>
+<td>2</td>
+<td>2</td>
+</tr>
+<tr>
+<td>int</td>
+<td>unsigned int</td>
+<td>4</td>
+<td>4</td>
+</tr>
+<tr>
+<td>long</td>
+<td>unsigned long</td>
+<td>4</td>
+<td>8</td>
+</tr>
+<tr>
+<td>int32_t</td>
+<td>uint32_t</td>
+<td>4</td>
+<td>4</td>
+</tr>
+<tr>
+<td>int64_t</td>
+<td>uint64_t</td>
+<td>8</td>
+<td>8</td>
+</tr>
+<tr>
+<td>char *</td>
+<td></td>
+<td>4</td>
+<td>8</td>
+</tr>
+<tr>
+<td>float</td>
+<td></td>
+<td>4</td>
+<td>4</td>
+</tr>
+<tr>
+<td>double</td>
+<td></td>
+<td>8</td>
+<td>8</td>
+</tr>
+</tbody></table>
+<p><strong>程序员应该力图使他们的程序在不同的机器和编译器上可移植</strong>。可移植性的一个方面就是使程序对不同数据类型的确切大小不敏感。</p>
+<blockquote>
+<p>字长、地址总线、数据总线 =&gt; 处理器一次能够处理的二进制位数、虚拟地址空间的最大大小、数据的最大大小。</p>
+</blockquote>
+<h3 id="寻址和字节顺序"><a href="#寻址和字节顺序" class="headerlink" title="寻址和字节顺序"></a>寻址和字节顺序</h3><p>对于<strong>跨越多字节的程序对象</strong>，我们必须建立两个规则：<strong>这个对象的地址是什么，以及在内存中如何排列这些字节</strong>。</p>
+<ul>
+<li>在几乎所有的机器上，多字节对象都被存储为连续的字节序列，对象的地址为所使用的字节中最小的地址。</li>
+<li>排列表示一个对象的字节有两个通用的规则。最低有效字节在最前面的方式，称为<strong>小端法</strong>（little endian）；最高有效字节在最前面的方式，称为<strong>大端法</strong>（big endian）。大多数 Intel 兼容机都只用小端模式；IBM 和 Oracle 的大多数机器按大端模式操作，个人计算机使用小端法；许多比较新的微处理器使用双端法（bi-endian），比如移动电话上的 ARM 微处理器，但是最常见的 Android 和 iOS 只能运行于小端模式。</li>
+</ul>
+<p><strong>选择何种字节顺序没有技术上的理由</strong>。只要选择了一种规则并且始终如一地坚持，对于哪种字节排序的选择都是任意的。</p>
+<blockquote>
+<p>和《格列佛游记》中的情节类似，争论仍然存在。</p>
+</blockquote>
+<p>对于大多数应用程序员来说，其机器所使用的字节顺序是完全不可见（透明）的。<strong>不过有时候，字节顺序会成为问题</strong>。</p>
+<ol>
+<li>在不同类型的机器之间通过网络传送二进制数据时，网络应用程序的代码编写必须遵守已建立的关于字节顺序的规则。</li>
+<li>当检查机器级程序，阅读表示整数数据的字节序列时字节顺序也很重要。</li>
+<li>当编写规避正常的类型系统的程序时，比如使用强制类型转换来访问和打印不同程序对象的字节表示。</li>
+</ol>
+<h3 id="表示字符串"><a href="#表示字符串" class="headerlink" title="表示字符串"></a>表示字符串</h3><p>C语言中字符串被编码为一个以null（其值为 0）字符结尾的字符数组。每个字符都由某个标准编码来表示，最常见的是 ASCII 字符码。字符串在使用 ASCII 码作为字符码的任何系统上都将得到相同的结果，与字节顺序和字大小规则无关。因而，<strong>文本数据比二进制数据具有更强的平台独立性</strong>。</p>
+<p>可以通过执行命令 <code>man ascii</code> 来得到一张 ASCII 字符码的表。</p>
+<p>文字编码的 <strong>Unicode 标准</strong>：<br>ASCII 字符集适合于编码英语文档，但是在表达一些特殊字符方面并没有太多办法，它完全不适合编码希腊语、俄语和中文等语言的文档。基本编码，称为 Unicode 的“统一字符集”，使用32位来表示字符，每个字符要占用4个字节。不过有一些替代编码，常见的字符只需要1个或2个字节，而不太常用的字符需要多一些的字节数。特别地，UTF-8 表示将每个字符编码为一个字节序列，兼容标准 ASCII。</p>
+<blockquote>
+<p>数字和符号，一一对应。</p>
+</blockquote>
+<h3 id="表示代码"><a href="#表示代码" class="headerlink" title="表示代码"></a>表示代码</h3><p>不同的机器类型使用不同的且不兼容的指令和编码方式。即使是完全一样的进程，运行在不同的操作系统上也会有不同的编码规则，因此二进制代码是不兼容的。二进制代码很少能在不同机器和操作系统组合之间移植。</p>
+<p>计算机系统的一个基本概念就是，<strong>从机器的角度来看，程序仅仅只是字节序列</strong>。机器没有关于原始源程序的任何信息，除了可能有些用来帮助调试的辅助表以外。</p>
+<h3 id="布尔代数简介"><a href="#布尔代数简介" class="headerlink" title="布尔代数简介"></a>布尔代数简介</h3><p>二进制值是计算机编码、存储和操作信息的核心，所以围绕数值 0 和 1 的研究已经演化出了丰富的数学知识体系，称为布尔代数（Boolean algebra）。</p>
+<p>最简单的布尔代数是在二元集合 <code>{0, 1}</code> 基础上的定义。二进制值 1 和 0 表示逻辑值 TRUE 或者 FALSE，而运算符<code>~</code>、<code>&amp;</code>、<code>|</code>和<code>^</code>分别表示逻辑运算 NOT、AND、OR 和 EXCLUSIVE-OR。</p>
+<p>布尔运算可以扩展到位向量的运算。</p>
+<p>布尔运算<code>&amp;</code>对<code>|</code>具有分配律；<code>|</code>对<code>&amp;</code>具有分配律。<br>布尔环：<code>a^a=0</code>，<code>(a^b)^a=b</code>。</p>
+<p><strong>位向量一个很有用的应用就是表示有限集合</strong>。</p>
+<h3 id="C语言中的布尔运算"><a href="#C语言中的布尔运算" class="headerlink" title="C语言中的布尔运算"></a>C语言中的布尔运算</h3><p>C语言的一个很有用的特性就是它支持按位布尔运算。<br>确定一个位级表达式的结果最好的方法，就是将十六进制的参数扩展成二进制表示并执行二进制运算，然后再转换回十六进制。</p>
+<h3 id="C语言中的移位运算"><a href="#C语言中的移位运算" class="headerlink" title="C语言中的移位运算"></a>C语言中的移位运算</h3><p>C语言还提供了一组移位运算，向左（<code>&lt;&lt;</code>）或者向右（<code>&gt;&gt;</code>）移动位模式。移位量应该是一个0~w-1之间的值。移位运算是从左至右可结合的。<br>右移运算 <code>x&gt;&gt;k</code> 的行为有点微妙。一般而言，机器支持两种形式的右移：逻辑右移和算术右移。逻辑右移在左端补k个0，算术右移是在左端补k个最高有效位的值。这种做法看上去可能有点奇特，但是它<strong>对有符号整数数据的运算非常有用</strong>。</p>
+<p>C语言标准并没有明确定义对于有符号数应该使用哪种类型的位移，这意味着可能会遇到可移植性问题。实际上，几乎所有的编译器/机器都对有符号数使用算术位移，对于无符号数使用逻辑右移。<br>与C相比，Java对于如何右移有明确的定义。<code>&gt;&gt;</code> 表示算术右移，<code>&gt;&gt;&gt;</code> 表示逻辑右移。</p>
+<p>对于一个由w位组成的数据类型，C语言标准很小心地规避了说明当移动k≥w位时应该如何做。在许多机器上，实际上位移量是通过<code>k mod w</code>得到的。</p>
+<p><strong>加减法的优先级比位移运算高</strong>。</p>
+<blockquote>
+<p>应该通过使用括号避免容易引起困扰的代码。</p>
+</blockquote>
+<h2 id="整数表示"><a href="#整数表示" class="headerlink" title="整数表示"></a>整数表示</h2><h3 id="整型数据类型"><a href="#整型数据类型" class="headerlink" title="整型数据类型"></a>整型数据类型</h3><p>C语言支持多种整型数据类型——表示有限范围的整数。</p>
+<table>
+<thead>
+<tr>
+<th>C数据类型</th>
+<th>32位</th>
+<th>64位</th>
+</tr>
+</thead>
+<tbody><tr>
+<td>[signed] char</td>
+<td>-128~127</td>
+<td></td>
+</tr>
+<tr>
+<td>unsigned char</td>
+<td>0~255</td>
+<td></td>
+</tr>
+<tr>
+<td>short</td>
+<td>-32 768~32 767</td>
+<td></td>
+</tr>
+<tr>
+<td>unsigned short</td>
+<td>0~65 535</td>
+<td></td>
+</tr>
+<tr>
+<td>int</td>
+<td>-2 147 483 648~2 147 483 647</td>
+<td></td>
+</tr>
+<tr>
+<td>unsigned int</td>
+<td>0~4 294 967 295</td>
+<td></td>
+</tr>
+<tr>
+<td>long</td>
+<td>-2 147 483 648~2 147 483 647</td>
+<td>-9 223 372 036 854 775 808~9 223 372 036 854 775 807</td>
+</tr>
+<tr>
+<td>unsigned long</td>
+<td>0~4 294 967 295</td>
+<td>0~18 446 744 073 709 551 615</td>
+</tr>
+<tr>
+<td>int32_t</td>
+<td>-2 147 483 648~2 147 483 647</td>
+<td></td>
+</tr>
+<tr>
+<td>uint32_t</td>
+<td>0~4 294 967 295</td>
+<td></td>
+</tr>
+<tr>
+<td>int64_t</td>
+<td>-9 223 372 036 854 775 808~9 223 372 036 854 775 807</td>
+<td></td>
+</tr>
+<tr>
+<td>uint64_t</td>
+<td>0~18 446 744 073 709 551 615</td>
+<td></td>
+</tr>
+</tbody></table>
+<p>取值范围并不对称，负数的范围比正数的范围大1。<br>C语言标准定义了每种数据类型必须<strong>能够表示的最小的取值范围</strong>，且char、short、int、long等类型的正数和负数的取值范围是对称的。</p>
+<blockquote>
+<p>将标准和具体实现以及字长分开看待（32位机器也可以支持64位表示的整数数据类型）。</p>
+</blockquote>
+<h3 id="无符号数的编码"><a href="#无符号数的编码" class="headerlink" title="无符号数的编码"></a>无符号数的编码</h3><p>假设有一个整数数据类型有 w 位。将位向量写成 <mjx-container class="MathJax" jax="SVG"><svg style="vertical-align: -0.025ex;" xmlns="http://www.w3.org/2000/svg" width="1.294ex" height="1.937ex" role="img" focusable="false" viewBox="0 -845 572 856"><g stroke="currentColor" fill="currentColor" stroke-width="0" transform="scale(1,-1)"><g data-mml-node="math"><g data-mml-node="TeXAtom" data-mjx-texclass="ORD"><g data-mml-node="mover"><g data-mml-node="mi"><path data-c="1D465" d="M52 289Q59 331 106 386T222 442Q257 442 286 424T329 379Q371 442 430 442Q467 442 494 420T522 361Q522 332 508 314T481 292T458 288Q439 288 427 299T415 328Q415 374 465 391Q454 404 425 404Q412 404 406 402Q368 386 350 336Q290 115 290 78Q290 50 306 38T341 26Q378 26 414 59T463 140Q466 150 469 151T485 153H489Q504 153 504 145Q504 144 502 134Q486 77 440 33T333 -11Q263 -11 227 52Q186 -10 133 -10H127Q78 -10 57 16T35 71Q35 103 54 123T99 143Q142 143 142 101Q142 81 130 66T107 46T94 41L91 40Q91 39 97 36T113 29T132 26Q168 26 194 71Q203 87 217 139T245 247T261 313Q266 340 266 352Q266 380 251 392T217 404Q177 404 142 372T93 290Q91 281 88 280T72 278H58Q52 284 52 289Z"></path></g><g data-mml-node="mo" transform="translate(313.8,31) translate(-250 0)"><path data-c="20D7" d="M377 694Q377 702 382 708T397 714Q404 714 409 709Q414 705 419 690Q429 653 460 633Q471 626 471 615Q471 606 468 603T454 594Q411 572 379 531Q377 529 374 525T369 519T364 517T357 516Q350 516 344 521T337 536Q337 555 384 595H213L42 596Q29 605 29 615Q29 622 42 635H401Q377 673 377 694Z"></path></g></g></g></g></g></svg></mjx-container>，或者写成 <mjx-container class="MathJax" jax="SVG"><svg style="vertical-align: -0.566ex;" xmlns="http://www.w3.org/2000/svg" width="18.93ex" height="2.262ex" role="img" focusable="false" viewBox="0 -750 8367.2 1000"><g stroke="currentColor" fill="currentColor" stroke-width="0" transform="scale(1,-1)"><g data-mml-node="math"><g data-mml-node="mrow"><g data-mml-node="mo"><path data-c="5B" d="M118 -250V750H255V710H158V-210H255V-250H118Z"></path></g><g data-mml-node="msub" transform="translate(278,0)"><g data-mml-node="mi"><path data-c="1D465" d="M52 289Q59 331 106 386T222 442Q257 442 286 424T329 379Q371 442 430 442Q467 442 494 420T522 361Q522 332 508 314T481 292T458 288Q439 288 427 299T415 328Q415 374 465 391Q454 404 425 404Q412 404 406 402Q368 386 350 336Q290 115 290 78Q290 50 306 38T341 26Q378 26 414 59T463 140Q466 150 469 151T485 153H489Q504 153 504 145Q504 144 502 134Q486 77 440 33T333 -11Q263 -11 227 52Q186 -10 133 -10H127Q78 -10 57 16T35 71Q35 103 54 123T99 143Q142 143 142 101Q142 81 130 66T107 46T94 41L91 40Q91 39 97 36T113 29T132 26Q168 26 194 71Q203 87 217 139T245 247T261 313Q266 340 266 352Q266 380 251 392T217 404Q177 404 142 372T93 290Q91 281 88 280T72 278H58Q52 284 52 289Z"></path></g><g data-mml-node="TeXAtom" transform="translate(605,-150) scale(0.707)" data-mjx-texclass="ORD"><g data-mml-node="mi"><path data-c="1D464" d="M580 385Q580 406 599 424T641 443Q659 443 674 425T690 368Q690 339 671 253Q656 197 644 161T609 80T554 12T482 -11Q438 -11 404 5T355 48Q354 47 352 44Q311 -11 252 -11Q226 -11 202 -5T155 14T118 53T104 116Q104 170 138 262T173 379Q173 380 173 381Q173 390 173 393T169 400T158 404H154Q131 404 112 385T82 344T65 302T57 280Q55 278 41 278H27Q21 284 21 287Q21 293 29 315T52 366T96 418T161 441Q204 441 227 416T250 358Q250 340 217 250T184 111Q184 65 205 46T258 26Q301 26 334 87L339 96V119Q339 122 339 128T340 136T341 143T342 152T345 165T348 182T354 206T362 238T373 281Q402 395 406 404Q419 431 449 431Q468 431 475 421T483 402Q483 389 454 274T422 142Q420 131 420 107V100Q420 85 423 71T442 42T487 26Q558 26 600 148Q609 171 620 213T632 273Q632 306 619 325T593 357T580 385Z"></path></g><g data-mml-node="mo" transform="translate(716,0)"><path data-c="2212" d="M84 237T84 250T98 270H679Q694 262 694 250T679 230H98Q84 237 84 250Z"></path></g><g data-mml-node="mn" transform="translate(1494,0)"><path data-c="31" d="M213 578L200 573Q186 568 160 563T102 556H83V602H102Q149 604 189 617T245 641T273 663Q275 666 285 666Q294 666 302 660V361L303 61Q310 54 315 52T339 48T401 46H427V0H416Q395 3 257 3Q121 3 100 0H88V46H114Q136 46 152 46T177 47T193 50T201 52T207 57T213 61V578Z"></path></g></g></g><g data-mml-node="mo" transform="translate(2343,0)"><path data-c="2C" d="M78 35T78 60T94 103T137 121Q165 121 187 96T210 8Q210 -27 201 -60T180 -117T154 -158T130 -185T117 -194Q113 -194 104 -185T95 -172Q95 -168 106 -156T131 -126T157 -76T173 -3V9L172 8Q170 7 167 6T161 3T152 1T140 0Q113 0 96 17Z"></path></g><g data-mml-node="msub" transform="translate(2787.6,0)"><g data-mml-node="mi"><path data-c="1D465" d="M52 289Q59 331 106 386T222 442Q257 442 286 424T329 379Q371 442 430 442Q467 442 494 420T522 361Q522 332 508 314T481 292T458 288Q439 288 427 299T415 328Q415 374 465 391Q454 404 425 404Q412 404 406 402Q368 386 350 336Q290 115 290 78Q290 50 306 38T341 26Q378 26 414 59T463 140Q466 150 469 151T485 153H489Q504 153 504 145Q504 144 502 134Q486 77 440 33T333 -11Q263 -11 227 52Q186 -10 133 -10H127Q78 -10 57 16T35 71Q35 103 54 123T99 143Q142 143 142 101Q142 81 130 66T107 46T94 41L91 40Q91 39 97 36T113 29T132 26Q168 26 194 71Q203 87 217 139T245 247T261 313Q266 340 266 352Q266 380 251 392T217 404Q177 404 142 372T93 290Q91 281 88 280T72 278H58Q52 284 52 289Z"></path></g><g data-mml-node="TeXAtom" transform="translate(605,-150) scale(0.707)" data-mjx-texclass="ORD"><g data-mml-node="mi"><path data-c="1D464" d="M580 385Q580 406 599 424T641 443Q659 443 674 425T690 368Q690 339 671 253Q656 197 644 161T609 80T554 12T482 -11Q438 -11 404 5T355 48Q354 47 352 44Q311 -11 252 -11Q226 -11 202 -5T155 14T118 53T104 116Q104 170 138 262T173 379Q173 380 173 381Q173 390 173 393T169 400T158 404H154Q131 404 112 385T82 344T65 302T57 280Q55 278 41 278H27Q21 284 21 287Q21 293 29 315T52 366T96 418T161 441Q204 441 227 416T250 358Q250 340 217 250T184 111Q184 65 205 46T258 26Q301 26 334 87L339 96V119Q339 122 339 128T340 136T341 143T342 152T345 165T348 182T354 206T362 238T373 281Q402 395 406 404Q419 431 449 431Q468 431 475 421T483 402Q483 389 454 274T422 142Q420 131 420 107V100Q420 85 423 71T442 42T487 26Q558 26 600 148Q609 171 620 213T632 273Q632 306 619 325T593 357T580 385Z"></path></g><g data-mml-node="mo" transform="translate(716,0)"><path data-c="2212" d="M84 237T84 250T98 270H679Q694 262 694 250T679 230H98Q84 237 84 250Z"></path></g><g data-mml-node="mn" transform="translate(1494,0)"><path data-c="32" d="M109 429Q82 429 66 447T50 491Q50 562 103 614T235 666Q326 666 387 610T449 465Q449 422 429 383T381 315T301 241Q265 210 201 149L142 93L218 92Q375 92 385 97Q392 99 409 186V189H449V186Q448 183 436 95T421 3V0H50V19V31Q50 38 56 46T86 81Q115 113 136 137Q145 147 170 174T204 211T233 244T261 278T284 308T305 340T320 369T333 401T340 431T343 464Q343 527 309 573T212 619Q179 619 154 602T119 569T109 550Q109 549 114 549Q132 549 151 535T170 489Q170 464 154 447T109 429Z"></path></g></g></g><g data-mml-node="mo" transform="translate(4852.6,0)"><path data-c="2C" d="M78 35T78 60T94 103T137 121Q165 121 187 96T210 8Q210 -27 201 -60T180 -117T154 -158T130 -185T117 -194Q113 -194 104 -185T95 -172Q95 -168 106 -156T131 -126T157 -76T173 -3V9L172 8Q170 7 167 6T161 3T152 1T140 0Q113 0 96 17Z"></path></g><g data-mml-node="mo" transform="translate(5297.3,0)"><path data-c="2026" d="M78 60Q78 84 95 102T138 120Q162 120 180 104T199 61Q199 36 182 18T139 0T96 17T78 60ZM525 60Q525 84 542 102T585 120Q609 120 627 104T646 61Q646 36 629 18T586 0T543 17T525 60ZM972 60Q972 84 989 102T1032 120Q1056 120 1074 104T1093 61Q1093 36 1076 18T1033 0T990 17T972 60Z"></path></g><g data-mml-node="mo" transform="translate(6635.9,0)"><path data-c="2C" d="M78 35T78 60T94 103T137 121Q165 121 187 96T210 8Q210 -27 201 -60T180 -117T154 -158T130 -185T117 -194Q113 -194 104 -185T95 -172Q95 -168 106 -156T131 -126T157 -76T173 -3V9L172 8Q170 7 167 6T161 3T152 1T140 0Q113 0 96 17Z"></path></g><g data-mml-node="msub" transform="translate(7080.6,0)"><g data-mml-node="mi"><path data-c="1D465" d="M52 289Q59 331 106 386T222 442Q257 442 286 424T329 379Q371 442 430 442Q467 442 494 420T522 361Q522 332 508 314T481 292T458 288Q439 288 427 299T415 328Q415 374 465 391Q454 404 425 404Q412 404 406 402Q368 386 350 336Q290 115 290 78Q290 50 306 38T341 26Q378 26 414 59T463 140Q466 150 469 151T485 153H489Q504 153 504 145Q504 144 502 134Q486 77 440 33T333 -11Q263 -11 227 52Q186 -10 133 -10H127Q78 -10 57 16T35 71Q35 103 54 123T99 143Q142 143 142 101Q142 81 130 66T107 46T94 41L91 40Q91 39 97 36T113 29T132 26Q168 26 194 71Q203 87 217 139T245 247T261 313Q266 340 266 352Q266 380 251 392T217 404Q177 404 142 372T93 290Q91 281 88 280T72 278H58Q52 284 52 289Z"></path></g><g data-mml-node="mn" transform="translate(605,-150) scale(0.707)"><path data-c="30" d="M96 585Q152 666 249 666Q297 666 345 640T423 548Q460 465 460 320Q460 165 417 83Q397 41 362 16T301 -15T250 -22Q224 -22 198 -16T137 16T82 83Q39 165 39 320Q39 494 96 585ZM321 597Q291 629 250 629Q208 629 178 597Q153 571 145 525T137 333Q137 175 145 125T181 46Q209 16 250 16Q290 16 318 46Q347 76 354 130T362 333Q362 478 354 524T321 597Z"></path></g></g><g data-mml-node="mo" transform="translate(8089.2,0)"><path data-c="5D" d="M22 710V750H159V-250H22V-210H119V710H22Z"></path></g></g></g></g></svg></mjx-container> 。</p>
+<p><strong>原理</strong>：无符号数编码的定义</p>
+<p><mjx-container class="MathJax" jax="SVG" display="true"><svg style="vertical-align: -2.819ex;" xmlns="http://www.w3.org/2000/svg" width="19.157ex" height="6.712ex" role="img" focusable="false" viewBox="0 -1720.9 8467.2 2966.8"><g stroke="currentColor" fill="currentColor" stroke-width="0" transform="scale(1,-1)"><g data-mml-node="math"><g data-mml-node="mi"><path data-c="1D435" d="M231 637Q204 637 199 638T194 649Q194 676 205 682Q206 683 335 683Q594 683 608 681Q671 671 713 636T756 544Q756 480 698 429T565 360L555 357Q619 348 660 311T702 219Q702 146 630 78T453 1Q446 0 242 0Q42 0 39 2Q35 5 35 10Q35 17 37 24Q42 43 47 45Q51 46 62 46H68Q95 46 128 49Q142 52 147 61Q150 65 219 339T288 628Q288 635 231 637ZM649 544Q649 574 634 600T585 634Q578 636 493 637Q473 637 451 637T416 636H403Q388 635 384 626Q382 622 352 506Q352 503 351 500L320 374H401Q482 374 494 376Q554 386 601 434T649 544ZM595 229Q595 273 572 302T512 336Q506 337 429 337Q311 337 310 336Q310 334 293 263T258 122L240 52Q240 48 252 48T333 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+<p>映射的范围</p>
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+<p><strong>原理</strong>：无符号数编码的唯一性</p>
+<p>函数 <mjx-container class="MathJax" jax="SVG"><svg style="vertical-align: -0.357ex;" xmlns="http://www.w3.org/2000/svg" width="5.727ex" height="1.902ex" role="img" focusable="false" viewBox="0 -683 2531.3 840.8"><g stroke="currentColor" fill="currentColor" stroke-width="0" transform="scale(1,-1)"><g data-mml-node="math"><g data-mml-node="mi"><path data-c="1D435" d="M231 637Q204 637 199 638T194 649Q194 676 205 682Q206 683 335 683Q594 683 608 681Q671 671 713 636T756 544Q756 480 698 429T565 360L555 357Q619 348 660 311T702 219Q702 146 630 78T453 1Q446 0 242 0Q42 0 39 2Q35 5 35 10Q35 17 37 24Q42 43 47 45Q51 46 62 46H68Q95 46 128 49Q142 52 147 61Q150 65 219 339T288 628Q288 635 231 637ZM649 544Q649 574 634 600T585 634Q578 636 493 637Q473 637 451 637T416 636H403Q388 635 384 626Q382 622 352 506Q352 503 351 500L320 374H401Q482 374 494 376Q554 386 601 434T649 544ZM595 229Q595 273 572 302T512 336Q506 337 429 337Q311 337 310 336Q310 334 293 263T258 122L240 52Q240 48 252 48T333 46Q422 46 429 47Q491 54 543 105T595 229Z"></path></g><g data-mml-node="mn" transform="translate(759,0)"><path data-c="32" d="M109 429Q82 429 66 447T50 491Q50 562 103 614T235 666Q326 666 387 610T449 465Q449 422 429 383T381 315T301 241Q265 210 201 149L142 93L218 92Q375 92 385 97Q392 99 409 186V189H449V186Q448 183 436 95T421 3V0H50V19V31Q50 38 56 46T86 81Q115 113 136 137Q145 147 170 174T204 211T233 244T261 278T284 308T305 340T320 369T333 401T340 431T343 464Q343 527 309 573T212 619Q179 619 154 602T119 569T109 550Q109 549 114 549Q132 549 151 535T170 489Q170 464 154 447T109 429Z"></path></g><g data-mml-node="msub" transform="translate(1259,0)"><g data-mml-node="mi"><path data-c="1D448" d="M107 637Q73 637 71 641Q70 643 70 649Q70 673 81 682Q83 683 98 683Q139 681 234 681Q268 681 297 681T342 682T362 682Q378 682 378 672Q378 670 376 658Q371 641 366 638H364Q362 638 359 638T352 638T343 637T334 637Q295 636 284 634T266 623Q265 621 238 518T184 302T154 169Q152 155 152 140Q152 86 183 55T269 24Q336 24 403 69T501 205L552 406Q599 598 599 606Q599 633 535 637Q511 637 511 648Q511 650 513 660Q517 676 519 679T529 683Q532 683 561 682T645 680Q696 680 723 681T752 682Q767 682 767 672Q767 650 759 642Q756 637 737 637Q666 633 648 597Q646 592 598 404Q557 235 548 205Q515 105 433 42T263 -22Q171 -22 116 34T60 167V183Q60 201 115 421Q164 622 164 628Q164 635 107 637Z"></path></g><g data-mml-node="TeXAtom" transform="translate(716,-150) scale(0.707)" data-mjx-texclass="ORD"><g data-mml-node="mi"><path data-c="1D464" d="M580 385Q580 406 599 424T641 443Q659 443 674 425T690 368Q690 339 671 253Q656 197 644 161T609 80T554 12T482 -11Q438 -11 404 5T355 48Q354 47 352 44Q311 -11 252 -11Q226 -11 202 -5T155 14T118 53T104 116Q104 170 138 262T173 379Q173 380 173 381Q173 390 173 393T169 400T158 404H154Q131 404 112 385T82 344T65 302T57 280Q55 278 41 278H27Q21 284 21 287Q21 293 29 315T52 366T96 418T161 441Q204 441 227 416T250 358Q250 340 217 250T184 111Q184 65 205 46T258 26Q301 26 334 87L339 96V119Q339 122 339 128T340 136T341 143T342 152T345 165T348 182T354 206T362 238T373 281Q402 395 406 404Q419 431 449 431Q468 431 475 421T483 402Q483 389 454 274T422 142Q420 131 420 107V100Q420 85 423 71T442 42T487 26Q558 26 600 148Q609 171 620 213T632 273Q632 306 619 325T593 357T580 385Z"></path></g></g></g></g></g></svg></mjx-container> 是一个双射。</p>
+<p><strong>原理</strong>：补码编码的定义</p>
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+<p>最高有效位 <mjx-container class="MathJax" jax="SVG"><svg style="vertical-align: -0.471ex;" xmlns="http://www.w3.org/2000/svg" width="4.672ex" height="1.471ex" role="img" focusable="false" viewBox="0 -442 2065 650"><g stroke="currentColor" fill="currentColor" stroke-width="0" transform="scale(1,-1)"><g data-mml-node="math"><g data-mml-node="msub"><g data-mml-node="mi"><path data-c="1D465" d="M52 289Q59 331 106 386T222 442Q257 442 286 424T329 379Q371 442 430 442Q467 442 494 420T522 361Q522 332 508 314T481 292T458 288Q439 288 427 299T415 328Q415 374 465 391Q454 404 425 404Q412 404 406 402Q368 386 350 336Q290 115 290 78Q290 50 306 38T341 26Q378 26 414 59T463 140Q466 150 469 151T485 153H489Q504 153 504 145Q504 144 502 134Q486 77 440 33T333 -11Q263 -11 227 52Q186 -10 133 -10H127Q78 -10 57 16T35 71Q35 103 54 123T99 143Q142 143 142 101Q142 81 130 66T107 46T94 41L91 40Q91 39 97 36T113 29T132 26Q168 26 194 71Q203 87 217 139T245 247T261 313Q266 340 266 352Q266 380 251 392T217 404Q177 404 142 372T93 290Q91 281 88 280T72 278H58Q52 284 52 289Z"></path></g><g data-mml-node="TeXAtom" transform="translate(605,-150) scale(0.707)" data-mjx-texclass="ORD"><g data-mml-node="mi"><path data-c="1D464" d="M580 385Q580 406 599 424T641 443Q659 443 674 425T690 368Q690 339 671 253Q656 197 644 161T609 80T554 12T482 -11Q438 -11 404 5T355 48Q354 47 352 44Q311 -11 252 -11Q226 -11 202 -5T155 14T118 53T104 116Q104 170 138 262T173 379Q173 380 173 381Q173 390 173 393T169 400T158 404H154Q131 404 112 385T82 344T65 302T57 280Q55 278 41 278H27Q21 284 21 287Q21 293 29 315T52 366T96 418T161 441Q204 441 227 416T250 358Q250 340 217 250T184 111Q184 65 205 46T258 26Q301 26 334 87L339 96V119Q339 122 339 128T340 136T341 143T342 152T345 165T348 182T354 206T362 238T373 281Q402 395 406 404Q419 431 449 431Q468 431 475 421T483 402Q483 389 454 274T422 142Q420 131 420 107V100Q420 85 423 71T442 42T487 26Q558 26 600 148Q609 171 620 213T632 273Q632 306 619 325T593 357T580 385Z"></path></g><g data-mml-node="mo" transform="translate(716,0)"><path data-c="2212" d="M84 237T84 250T98 270H679Q694 262 694 250T679 230H98Q84 237 84 250Z"></path></g><g data-mml-node="mn" transform="translate(1494,0)"><path data-c="31" d="M213 578L200 573Q186 568 160 563T102 556H83V602H102Q149 604 189 617T245 641T273 663Q275 666 285 666Q294 666 302 660V361L303 61Q310 54 315 52T339 48T401 46H427V0H416Q395 3 257 3Q121 3 100 0H88V46H114Q136 46 152 46T177 47T193 50T201 52T207 57T213 61V578Z"></path></g></g></g></g></g></svg></mjx-container> 称为符号位，权重为 <mjx-container class="MathJax" jax="SVG"><svg style="vertical-align: -0.186ex;" xmlns="http://www.w3.org/2000/svg" width="6.269ex" height="2.072ex" role="img" focusable="false" viewBox="0 -833.9 2771 915.9"><g stroke="currentColor" fill="currentColor" stroke-width="0" transform="scale(1,-1)"><g data-mml-node="math"><g data-mml-node="mo"><path data-c="2212" d="M84 237T84 250T98 270H679Q694 262 694 250T679 230H98Q84 237 84 250Z"></path></g><g data-mml-node="msup" transform="translate(778,0)"><g data-mml-node="mn"><path data-c="32" d="M109 429Q82 429 66 447T50 491Q50 562 103 614T235 666Q326 666 387 610T449 465Q449 422 429 383T381 315T301 241Q265 210 201 149L142 93L218 92Q375 92 385 97Q392 99 409 186V189H449V186Q448 183 436 95T421 3V0H50V19V31Q50 38 56 46T86 81Q115 113 136 137Q145 147 170 174T204 211T233 244T261 278T284 308T305 340T320 369T333 401T340 431T343 464Q343 527 309 573T212 619Q179 619 154 602T119 569T109 550Q109 549 114 549Q132 549 151 535T170 489Q170 464 154 447T109 429Z"></path></g><g data-mml-node="TeXAtom" transform="translate(533,363) scale(0.707)" data-mjx-texclass="ORD"><g data-mml-node="mi"><path data-c="1D464" d="M580 385Q580 406 599 424T641 443Q659 443 674 425T690 368Q690 339 671 253Q656 197 644 161T609 80T554 12T482 -11Q438 -11 404 5T355 48Q354 47 352 44Q311 -11 252 -11Q226 -11 202 -5T155 14T118 53T104 116Q104 170 138 262T173 379Q173 380 173 381Q173 390 173 393T169 400T158 404H154Q131 404 112 385T82 344T65 302T57 280Q55 278 41 278H27Q21 284 21 287Q21 293 29 315T52 366T96 418T161 441Q204 441 227 416T250 358Q250 340 217 250T184 111Q184 65 205 46T258 26Q301 26 334 87L339 96V119Q339 122 339 128T340 136T341 143T342 152T345 165T348 182T354 206T362 238T373 281Q402 395 406 404Q419 431 449 431Q468 431 475 421T483 402Q483 389 454 274T422 142Q420 131 420 107V100Q420 85 423 71T442 42T487 26Q558 26 600 148Q609 171 620 213T632 273Q632 306 619 325T593 357T580 385Z"></path></g><g data-mml-node="mo" transform="translate(716,0)"><path data-c="2212" d="M84 237T84 250T98 270H679Q694 262 694 250T679 230H98Q84 237 84 250Z"></path></g><g data-mml-node="mn" transform="translate(1494,0)"><path data-c="31" d="M213 578L200 573Q186 568 160 563T102 556H83V602H102Q149 604 189 617T245 641T273 663Q275 666 285 666Q294 666 302 660V361L303 61Q310 54 315 52T339 48T401 46H427V0H416Q395 3 257 3Q121 3 100 0H88V46H114Q136 46 152 46T177 47T193 50T201 52T207 57T213 61V578Z"></path></g></g></g></g></g></svg></mjx-container>，符号位被设置为 1 时，表示值为负，当设置为 0 时，值为非负。</p>
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869 0Q864 0 828 1T736 2Q675 2 644 2T609 1Q592 1 592 11Q592 13 594 25Q598 41 602 43T625 46Q652 46 685 49Q699 52 704 61Q706 65 742 207T813 490T848 631L654 322Q458 10 453 5Q451 4 449 3Q444 0 433 0Q418 0 415 7Q413 11 374 317L335 624L267 354Q200 88 200 79Q206 46 272 46H282Q288 41 289 37T286 19Q282 3 278 1Q274 0 267 0Q265 0 255 0T221 1T157 2Q127 2 95 1T58 0Q43 0 39 2T35 11Q35 13 38 25T43 40Q45 46 65 46Q135 46 154 86Q158 92 223 354T289 629Z"></path></g><g data-mml-node="mi" transform="translate(15627.6,0)"><path data-c="1D44E" d="M33 157Q33 258 109 349T280 441Q331 441 370 392Q386 422 416 422Q429 422 439 414T449 394Q449 381 412 234T374 68Q374 43 381 35T402 26Q411 27 422 35Q443 55 463 131Q469 151 473 152Q475 153 483 153H487Q506 153 506 144Q506 138 501 117T481 63T449 13Q436 0 417 -8Q409 -10 393 -10Q359 -10 336 5T306 36L300 51Q299 52 296 50Q294 48 292 46Q233 -10 172 -10Q117 -10 75 30T33 157ZM351 328Q351 334 346 350T323 385T277 405Q242 405 210 374T160 293Q131 214 119 129Q119 126 119 118T118 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368Q690 339 671 253Q656 197 644 161T609 80T554 12T482 -11Q438 -11 404 5T355 48Q354 47 352 44Q311 -11 252 -11Q226 -11 202 -5T155 14T118 53T104 116Q104 170 138 262T173 379Q173 380 173 381Q173 390 173 393T169 400T158 404H154Q131 404 112 385T82 344T65 302T57 280Q55 278 41 278H27Q21 284 21 287Q21 293 29 315T52 366T96 418T161 441Q204 441 227 416T250 358Q250 340 217 250T184 111Q184 65 205 46T258 26Q301 26 334 87L339 96V119Q339 122 339 128T340 136T341 143T342 152T345 165T348 182T354 206T362 238T373 281Q402 395 406 404Q419 431 449 431Q468 431 475 421T483 402Q483 389 454 274T422 142Q420 131 420 107V100Q420 85 423 71T442 42T487 26Q558 26 600 148Q609 171 620 213T632 273Q632 306 619 325T593 357T580 385Z"></path></g></g><g data-mml-node="mo" transform="translate(17317.9,0)"><path data-c="7D" d="M65 731Q65 745 68 747T88 750Q171 750 216 725T279 670Q288 649 289 635T291 501Q292 362 293 357Q306 312 345 291T417 269Q428 269 431 266T434 250T431 234T417 231Q380 231 345 210T298 157Q293 143 292 121T291 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+<p><strong>原理</strong>：补码编码的唯一性</p>
+<p>函数 <mjx-container class="MathJax" jax="SVG"><svg style="vertical-align: -0.357ex;" xmlns="http://www.w3.org/2000/svg" width="5.503ex" height="1.902ex" role="img" focusable="false" viewBox="0 -683 2432.3 840.8"><g stroke="currentColor" fill="currentColor" stroke-width="0" transform="scale(1,-1)"><g data-mml-node="math"><g data-mml-node="mi"><path data-c="1D435" d="M231 637Q204 637 199 638T194 649Q194 676 205 682Q206 683 335 683Q594 683 608 681Q671 671 713 636T756 544Q756 480 698 429T565 360L555 357Q619 348 660 311T702 219Q702 146 630 78T453 1Q446 0 242 0Q42 0 39 2Q35 5 35 10Q35 17 37 24Q42 43 47 45Q51 46 62 46H68Q95 46 128 49Q142 52 147 61Q150 65 219 339T288 628Q288 635 231 637ZM649 544Q649 574 634 600T585 634Q578 636 493 637Q473 637 451 637T416 636H403Q388 635 384 626Q382 622 352 506Q352 503 351 500L320 374H401Q482 374 494 376Q554 386 601 434T649 544ZM595 229Q595 273 572 302T512 336Q506 337 429 337Q311 337 310 336Q310 334 293 263T258 122L240 52Q240 48 252 48T333 46Q422 46 429 47Q491 54 543 105T595 229Z"></path></g><g data-mml-node="mn" transform="translate(759,0)"><path data-c="32" d="M109 429Q82 429 66 447T50 491Q50 562 103 614T235 666Q326 666 387 610T449 465Q449 422 429 383T381 315T301 241Q265 210 201 149L142 93L218 92Q375 92 385 97Q392 99 409 186V189H449V186Q448 183 436 95T421 3V0H50V19V31Q50 38 56 46T86 81Q115 113 136 137Q145 147 170 174T204 211T233 244T261 278T284 308T305 340T320 369T333 401T340 431T343 464Q343 527 309 573T212 619Q179 619 154 602T119 569T109 550Q109 549 114 549Q132 549 151 535T170 489Q170 464 154 447T109 429Z"></path></g><g data-mml-node="msub" transform="translate(1259,0)"><g data-mml-node="mi"><path data-c="1D447" d="M40 437Q21 437 21 445Q21 450 37 501T71 602L88 651Q93 669 101 677H569H659Q691 677 697 676T704 667Q704 661 687 553T668 444Q668 437 649 437Q640 437 637 437T631 442L629 445Q629 451 635 490T641 551Q641 586 628 604T573 629Q568 630 515 631Q469 631 457 630T439 622Q438 621 368 343T298 60Q298 48 386 46Q418 46 427 45T436 36Q436 31 433 22Q429 4 424 1L422 0Q419 0 415 0Q410 0 363 1T228 2Q99 2 64 0H49Q43 6 43 9T45 27Q49 40 55 46H83H94Q174 46 189 55Q190 56 191 56Q196 59 201 76T241 233Q258 301 269 344Q339 619 339 625Q339 630 310 630H279Q212 630 191 624Q146 614 121 583T67 467Q60 445 57 441T43 437H40Z"></path></g><g data-mml-node="TeXAtom" transform="translate(617,-150) scale(0.707)" data-mjx-texclass="ORD"><g data-mml-node="mi"><path data-c="1D464" d="M580 385Q580 406 599 424T641 443Q659 443 674 425T690 368Q690 339 671 253Q656 197 644 161T609 80T554 12T482 -11Q438 -11 404 5T355 48Q354 47 352 44Q311 -11 252 -11Q226 -11 202 -5T155 14T118 53T104 116Q104 170 138 262T173 379Q173 380 173 381Q173 390 173 393T169 400T158 404H154Q131 404 112 385T82 344T65 302T57 280Q55 278 41 278H27Q21 284 21 287Q21 293 29 315T52 366T96 418T161 441Q204 441 227 416T250 358Q250 340 217 250T184 111Q184 65 205 46T258 26Q301 26 334 87L339 96V119Q339 122 339 128T340 136T341 143T342 152T345 165T348 182T354 206T362 238T373 281Q402 395 406 404Q419 431 449 431Q468 431 475 421T483 402Q483 389 454 274T422 142Q420 131 420 107V100Q420 85 423 71T442 42T487 26Q558 26 600 148Q609 171 620 213T632 273Q632 306 619 325T593 357T580 385Z"></path></g></g></g></g></g></svg></mjx-container> 是一个双射。</p>
+<p>观察特殊值</p>
+<table>
+<thead>
+<tr>
+<th>数</th>
+<th>w=8</th>
+</tr>
+</thead>
+<tbody><tr>
+<td><mjx-container class="MathJax" jax="SVG"><svg style="vertical-align: -0.357ex;" xmlns="http://www.w3.org/2000/svg" width="7.937ex" height="1.902ex" role="img" focusable="false" viewBox="0 -683 3508.3 840.8"><g stroke="currentColor" fill="currentColor" stroke-width="0" transform="scale(1,-1)"><g data-mml-node="math"><g data-mml-node="mi"><path data-c="1D448" d="M107 637Q73 637 71 641Q70 643 70 649Q70 673 81 682Q83 683 98 683Q139 681 234 681Q268 681 297 681T342 682T362 682Q378 682 378 672Q378 670 376 658Q371 641 366 638H364Q362 638 359 638T352 638T343 637T334 637Q295 636 284 634T266 623Q265 621 238 518T184 302T154 169Q152 155 152 140Q152 86 183 55T269 24Q336 24 403 69T501 205L552 406Q599 598 599 606Q599 633 535 637Q511 637 511 648Q511 650 513 660Q517 676 519 679T529 683Q532 683 561 682T645 680Q696 680 723 681T752 682Q767 682 767 672Q767 650 759 642Q756 637 737 637Q666 633 648 597Q646 592 598 404Q557 235 548 205Q515 105 433 42T263 -22Q171 -22 116 34T60 167V183Q60 201 115 421Q164 622 164 628Q164 635 107 637Z"></path></g><g data-mml-node="mi" transform="translate(767,0)"><path data-c="1D440" d="M289 629Q289 635 232 637Q208 637 201 638T194 648Q194 649 196 659Q197 662 198 666T199 671T201 676T203 679T207 681T212 683T220 683T232 684Q238 684 262 684T307 683Q386 683 398 683T414 678Q415 674 451 396L487 117L510 154Q534 190 574 254T662 394Q837 673 839 675Q840 676 842 678T846 681L852 683H948Q965 683 988 683T1017 684Q1051 684 1051 673Q1051 668 1048 656T1045 643Q1041 637 1008 637Q968 636 957 634T939 623Q936 618 867 340T797 59Q797 55 798 54T805 50T822 48T855 46H886Q892 37 892 35Q892 19 885 5Q880 0 869 0Q864 0 828 1T736 2Q675 2 644 2T609 1Q592 1 592 11Q592 13 594 25Q598 41 602 43T625 46Q652 46 685 49Q699 52 704 61Q706 65 742 207T813 490T848 631L654 322Q458 10 453 5Q451 4 449 3Q444 0 433 0Q418 0 415 7Q413 11 374 317L335 624L267 354Q200 88 200 79Q206 46 272 46H282Q288 41 289 37T286 19Q282 3 278 1Q274 0 267 0Q265 0 255 0T221 1T157 2Q127 2 95 1T58 0Q43 0 39 2T35 11Q35 13 38 25T43 40Q45 46 65 46Q135 46 154 86Q158 92 223 354T289 629Z"></path></g><g data-mml-node="mi" transform="translate(1818,0)"><path data-c="1D44E" d="M33 157Q33 258 109 349T280 441Q331 441 370 392Q386 422 416 422Q429 422 439 414T449 394Q449 381 412 234T374 68Q374 43 381 35T402 26Q411 27 422 35Q443 55 463 131Q469 151 473 152Q475 153 483 153H487Q506 153 506 144Q506 138 501 117T481 63T449 13Q436 0 417 -8Q409 -10 393 -10Q359 -10 336 5T306 36L300 51Q299 52 296 50Q294 48 292 46Q233 -10 172 -10Q117 -10 75 30T33 157ZM351 328Q351 334 346 350T323 385T277 405Q242 405 210 374T160 293Q131 214 119 129Q119 126 119 118T118 106Q118 61 136 44T179 26Q217 26 254 59T298 110Q300 114 325 217T351 328Z"></path></g><g data-mml-node="msub" transform="translate(2347,0)"><g data-mml-node="mi"><path data-c="1D465" d="M52 289Q59 331 106 386T222 442Q257 442 286 424T329 379Q371 442 430 442Q467 442 494 420T522 361Q522 332 508 314T481 292T458 288Q439 288 427 299T415 328Q415 374 465 391Q454 404 425 404Q412 404 406 402Q368 386 350 336Q290 115 290 78Q290 50 306 38T341 26Q378 26 414 59T463 140Q466 150 469 151T485 153H489Q504 153 504 145Q504 144 502 134Q486 77 440 33T333 -11Q263 -11 227 52Q186 -10 133 -10H127Q78 -10 57 16T35 71Q35 103 54 123T99 143Q142 143 142 101Q142 81 130 66T107 46T94 41L91 40Q91 39 97 36T113 29T132 26Q168 26 194 71Q203 87 217 139T245 247T261 313Q266 340 266 352Q266 380 251 392T217 404Q177 404 142 372T93 290Q91 281 88 280T72 278H58Q52 284 52 289Z"></path></g><g data-mml-node="mi" transform="translate(605,-150) scale(0.707)"><path data-c="1D464" d="M580 385Q580 406 599 424T641 443Q659 443 674 425T690 368Q690 339 671 253Q656 197 644 161T609 80T554 12T482 -11Q438 -11 404 5T355 48Q354 47 352 44Q311 -11 252 -11Q226 -11 202 -5T155 14T118 53T104 116Q104 170 138 262T173 379Q173 380 173 381Q173 390 173 393T169 400T158 404H154Q131 404 112 385T82 344T65 302T57 280Q55 278 41 278H27Q21 284 21 287Q21 293 29 315T52 366T96 418T161 441Q204 441 227 416T250 358Q250 340 217 250T184 111Q184 65 205 46T258 26Q301 26 334 87L339 96V119Q339 122 339 128T340 136T341 143T342 152T345 165T348 182T354 206T362 238T373 281Q402 395 406 404Q419 431 449 431Q468 431 475 421T483 402Q483 389 454 274T422 142Q420 131 420 107V100Q420 85 423 71T442 42T487 26Q558 26 600 148Q609 171 620 213T632 273Q632 306 619 325T593 357T580 385Z"></path></g></g></g></g></svg></mjx-container></td>
+<td>11111111</td>
+</tr>
+<tr>
+<td><mjx-container class="MathJax" jax="SVG"><svg style="vertical-align: -0.357ex;" xmlns="http://www.w3.org/2000/svg" width="7.442ex" height="1.902ex" role="img" focusable="false" viewBox="0 -683 3289.3 840.8"><g stroke="currentColor" fill="currentColor" stroke-width="0" transform="scale(1,-1)"><g data-mml-node="math"><g data-mml-node="mi"><path data-c="1D447" d="M40 437Q21 437 21 445Q21 450 37 501T71 602L88 651Q93 669 101 677H569H659Q691 677 697 676T704 667Q704 661 687 553T668 444Q668 437 649 437Q640 437 637 437T631 442L629 445Q629 451 635 490T641 551Q641 586 628 604T573 629Q568 630 515 631Q469 631 457 630T439 622Q438 621 368 343T298 60Q298 48 386 46Q418 46 427 45T436 36Q436 31 433 22Q429 4 424 1L422 0Q419 0 415 0Q410 0 363 1T228 2Q99 2 64 0H49Q43 6 43 9T45 27Q49 40 55 46H83H94Q174 46 189 55Q190 56 191 56Q196 59 201 76T241 233Q258 301 269 344Q339 619 339 625Q339 630 310 630H279Q212 630 191 624Q146 614 121 583T67 467Q60 445 57 441T43 437H40Z"></path></g><g data-mml-node="mi" transform="translate(704,0)"><path data-c="1D440" d="M289 629Q289 635 232 637Q208 637 201 638T194 648Q194 649 196 659Q197 662 198 666T199 671T201 676T203 679T207 681T212 683T220 683T232 684Q238 684 262 684T307 683Q386 683 398 683T414 678Q415 674 451 396L487 117L510 154Q534 190 574 254T662 394Q837 673 839 675Q840 676 842 678T846 681L852 683H948Q965 683 988 683T1017 684Q1051 684 1051 673Q1051 668 1048 656T1045 643Q1041 637 1008 637Q968 636 957 634T939 623Q936 618 867 340T797 59Q797 55 798 54T805 50T822 48T855 46H886Q892 37 892 35Q892 19 885 5Q880 0 869 0Q864 0 828 1T736 2Q675 2 644 2T609 1Q592 1 592 11Q592 13 594 25Q598 41 602 43T625 46Q652 46 685 49Q699 52 704 61Q706 65 742 207T813 490T848 631L654 322Q458 10 453 5Q451 4 449 3Q444 0 433 0Q418 0 415 7Q413 11 374 317L335 624L267 354Q200 88 200 79Q206 46 272 46H282Q288 41 289 37T286 19Q282 3 278 1Q274 0 267 0Q265 0 255 0T221 1T157 2Q127 2 95 1T58 0Q43 0 39 2T35 11Q35 13 38 25T43 40Q45 46 65 46Q135 46 154 86Q158 92 223 354T289 629Z"></path></g><g data-mml-node="mi" transform="translate(1755,0)"><path data-c="1D456" d="M184 600Q184 624 203 642T247 661Q265 661 277 649T290 619Q290 596 270 577T226 557Q211 557 198 567T184 600ZM21 287Q21 295 30 318T54 369T98 420T158 442Q197 442 223 419T250 357Q250 340 236 301T196 196T154 83Q149 61 149 51Q149 26 166 26Q175 26 185 29T208 43T235 78T260 137Q263 149 265 151T282 153Q302 153 302 143Q302 135 293 112T268 61T223 11T161 -11Q129 -11 102 10T74 74Q74 91 79 106T122 220Q160 321 166 341T173 380Q173 404 156 404H154Q124 404 99 371T61 287Q60 286 59 284T58 281T56 279T53 278T49 278T41 278H27Q21 284 21 287Z"></path></g><g data-mml-node="msub" transform="translate(2100,0)"><g data-mml-node="mi"><path data-c="1D45B" d="M21 287Q22 293 24 303T36 341T56 388T89 425T135 442Q171 442 195 424T225 390T231 369Q231 367 232 367L243 378Q304 442 382 442Q436 442 469 415T503 336T465 179T427 52Q427 26 444 26Q450 26 453 27Q482 32 505 65T540 145Q542 153 560 153Q580 153 580 145Q580 144 576 130Q568 101 554 73T508 17T439 -10Q392 -10 371 17T350 73Q350 92 386 193T423 345Q423 404 379 404H374Q288 404 229 303L222 291L189 157Q156 26 151 16Q138 -11 108 -11Q95 -11 87 -5T76 7T74 17Q74 30 112 180T152 343Q153 348 153 366Q153 405 129 405Q91 405 66 305Q60 285 60 284Q58 278 41 278H27Q21 284 21 287Z"></path></g><g data-mml-node="mi" transform="translate(633,-150) scale(0.707)"><path data-c="1D464" d="M580 385Q580 406 599 424T641 443Q659 443 674 425T690 368Q690 339 671 253Q656 197 644 161T609 80T554 12T482 -11Q438 -11 404 5T355 48Q354 47 352 44Q311 -11 252 -11Q226 -11 202 -5T155 14T118 53T104 116Q104 170 138 262T173 379Q173 380 173 381Q173 390 173 393T169 400T158 404H154Q131 404 112 385T82 344T65 302T57 280Q55 278 41 278H27Q21 284 21 287Q21 293 29 315T52 366T96 418T161 441Q204 441 227 416T250 358Q250 340 217 250T184 111Q184 65 205 46T258 26Q301 26 334 87L339 96V119Q339 122 339 128T340 136T341 143T342 152T345 165T348 182T354 206T362 238T373 281Q402 395 406 404Q419 431 449 431Q468 431 475 421T483 402Q483 389 454 274T422 142Q420 131 420 107V100Q420 85 423 71T442 42T487 26Q558 26 600 148Q609 171 620 213T632 273Q632 306 619 325T593 357T580 385Z"></path></g></g></g></g></svg></mjx-container></td>
+<td>10000000</td>
+</tr>
+<tr>
+<td><mjx-container class="MathJax" jax="SVG"><svg style="vertical-align: -0.357ex;" xmlns="http://www.w3.org/2000/svg" width="7.795ex" height="1.902ex" role="img" focusable="false" viewBox="0 -683 3445.3 840.8"><g stroke="currentColor" fill="currentColor" stroke-width="0" transform="scale(1,-1)"><g data-mml-node="math"><g data-mml-node="mi"><path data-c="1D447" d="M40 437Q21 437 21 445Q21 450 37 501T71 602L88 651Q93 669 101 677H569H659Q691 677 697 676T704 667Q704 661 687 553T668 444Q668 437 649 437Q640 437 637 437T631 442L629 445Q629 451 635 490T641 551Q641 586 628 604T573 629Q568 630 515 631Q469 631 457 630T439 622Q438 621 368 343T298 60Q298 48 386 46Q418 46 427 45T436 36Q436 31 433 22Q429 4 424 1L422 0Q419 0 415 0Q410 0 363 1T228 2Q99 2 64 0H49Q43 6 43 9T45 27Q49 40 55 46H83H94Q174 46 189 55Q190 56 191 56Q196 59 201 76T241 233Q258 301 269 344Q339 619 339 625Q339 630 310 630H279Q212 630 191 624Q146 614 121 583T67 467Q60 445 57 441T43 437H40Z"></path></g><g data-mml-node="mi" transform="translate(704,0)"><path data-c="1D440" d="M289 629Q289 635 232 637Q208 637 201 638T194 648Q194 649 196 659Q197 662 198 666T199 671T201 676T203 679T207 681T212 683T220 683T232 684Q238 684 262 684T307 683Q386 683 398 683T414 678Q415 674 451 396L487 117L510 154Q534 190 574 254T662 394Q837 673 839 675Q840 676 842 678T846 681L852 683H948Q965 683 988 683T1017 684Q1051 684 1051 673Q1051 668 1048 656T1045 643Q1041 637 1008 637Q968 636 957 634T939 623Q936 618 867 340T797 59Q797 55 798 54T805 50T822 48T855 46H886Q892 37 892 35Q892 19 885 5Q880 0 869 0Q864 0 828 1T736 2Q675 2 644 2T609 1Q592 1 592 11Q592 13 594 25Q598 41 602 43T625 46Q652 46 685 49Q699 52 704 61Q706 65 742 207T813 490T848 631L654 322Q458 10 453 5Q451 4 449 3Q444 0 433 0Q418 0 415 7Q413 11 374 317L335 624L267 354Q200 88 200 79Q206 46 272 46H282Q288 41 289 37T286 19Q282 3 278 1Q274 0 267 0Q265 0 255 0T221 1T157 2Q127 2 95 1T58 0Q43 0 39 2T35 11Q35 13 38 25T43 40Q45 46 65 46Q135 46 154 86Q158 92 223 354T289 629Z"></path></g><g data-mml-node="mi" transform="translate(1755,0)"><path data-c="1D44E" d="M33 157Q33 258 109 349T280 441Q331 441 370 392Q386 422 416 422Q429 422 439 414T449 394Q449 381 412 234T374 68Q374 43 381 35T402 26Q411 27 422 35Q443 55 463 131Q469 151 473 152Q475 153 483 153H487Q506 153 506 144Q506 138 501 117T481 63T449 13Q436 0 417 -8Q409 -10 393 -10Q359 -10 336 5T306 36L300 51Q299 52 296 50Q294 48 292 46Q233 -10 172 -10Q117 -10 75 30T33 157ZM351 328Q351 334 346 350T323 385T277 405Q242 405 210 374T160 293Q131 214 119 129Q119 126 119 118T118 106Q118 61 136 44T179 26Q217 26 254 59T298 110Q300 114 325 217T351 328Z"></path></g><g data-mml-node="msub" transform="translate(2284,0)"><g data-mml-node="mi"><path data-c="1D465" d="M52 289Q59 331 106 386T222 442Q257 442 286 424T329 379Q371 442 430 442Q467 442 494 420T522 361Q522 332 508 314T481 292T458 288Q439 288 427 299T415 328Q415 374 465 391Q454 404 425 404Q412 404 406 402Q368 386 350 336Q290 115 290 78Q290 50 306 38T341 26Q378 26 414 59T463 140Q466 150 469 151T485 153H489Q504 153 504 145Q504 144 502 134Q486 77 440 33T333 -11Q263 -11 227 52Q186 -10 133 -10H127Q78 -10 57 16T35 71Q35 103 54 123T99 143Q142 143 142 101Q142 81 130 66T107 46T94 41L91 40Q91 39 97 36T113 29T132 26Q168 26 194 71Q203 87 217 139T245 247T261 313Q266 340 266 352Q266 380 251 392T217 404Q177 404 142 372T93 290Q91 281 88 280T72 278H58Q52 284 52 289Z"></path></g><g data-mml-node="mi" transform="translate(605,-150) scale(0.707)"><path data-c="1D464" d="M580 385Q580 406 599 424T641 443Q659 443 674 425T690 368Q690 339 671 253Q656 197 644 161T609 80T554 12T482 -11Q438 -11 404 5T355 48Q354 47 352 44Q311 -11 252 -11Q226 -11 202 -5T155 14T118 53T104 116Q104 170 138 262T173 379Q173 380 173 381Q173 390 173 393T169 400T158 404H154Q131 404 112 385T82 344T65 302T57 280Q55 278 41 278H27Q21 284 21 287Q21 293 29 315T52 366T96 418T161 441Q204 441 227 416T250 358Q250 340 217 250T184 111Q184 65 205 46T258 26Q301 26 334 87L339 96V119Q339 122 339 128T340 136T341 143T342 152T345 165T348 182T354 206T362 238T373 281Q402 395 406 404Q419 431 449 431Q468 431 475 421T483 402Q483 389 454 274T422 142Q420 131 420 107V100Q420 85 423 71T442 42T487 26Q558 26 600 148Q609 171 620 213T632 273Q632 306 619 325T593 357T580 385Z"></path></g></g></g></g></svg></mjx-container></td>
+<td>01111111</td>
+</tr>
+<tr>
+<td>-1</td>
+<td>11111111</td>
+</tr>
+<tr>
+<td>0</td>
+<td>00000000</td>
+</tr>
+</tbody></table>
+<ol>
+<li>补码的范围不对称<br><mjx-container class="MathJax" jax="SVG" display="true"><svg style="vertical-align: -0.564ex;" xmlns="http://www.w3.org/2000/svg" width="24.666ex" height="2.26ex" role="img" focusable="false" viewBox="0 -749.5 10902.6 999"><g stroke="currentColor" fill="currentColor" stroke-width="0" transform="scale(1,-1)"><g data-mml-node="math"><g data-mml-node="mo" transform="translate(0 -0.5)"><path data-c="7C" d="M139 -249H137Q125 -249 119 -235V251L120 737Q130 750 139 750Q152 750 159 735V-235Q151 -249 141 -249H139Z"></path></g><g data-mml-node="mi" transform="translate(278,0)"><path data-c="1D447" d="M40 437Q21 437 21 445Q21 450 37 501T71 602L88 651Q93 669 101 677H569H659Q691 677 697 676T704 667Q704 661 687 553T668 444Q668 437 649 437Q640 437 637 437T631 442L629 445Q629 451 635 490T641 551Q641 586 628 604T573 629Q568 630 515 631Q469 631 457 630T439 622Q438 621 368 343T298 60Q298 48 386 46Q418 46 427 45T436 36Q436 31 433 22Q429 4 424 1L422 0Q419 0 415 0Q410 0 363 1T228 2Q99 2 64 0H49Q43 6 43 9T45 27Q49 40 55 46H83H94Q174 46 189 55Q190 56 191 56Q196 59 201 76T241 233Q258 301 269 344Q339 619 339 625Q339 630 310 630H279Q212 630 191 624Q146 614 121 583T67 467Q60 445 57 441T43 437H40Z"></path></g><g data-mml-node="mi" transform="translate(982,0)"><path data-c="1D440" d="M289 629Q289 635 232 637Q208 637 201 638T194 648Q194 649 196 659Q197 662 198 666T199 671T201 676T203 679T207 681T212 683T220 683T232 684Q238 684 262 684T307 683Q386 683 398 683T414 678Q415 674 451 396L487 117L510 154Q534 190 574 254T662 394Q837 673 839 675Q840 676 842 678T846 681L852 683H948Q965 683 988 683T1017 684Q1051 684 1051 673Q1051 668 1048 656T1045 643Q1041 637 1008 637Q968 636 957 634T939 623Q936 618 867 340T797 59Q797 55 798 54T805 50T822 48T855 46H886Q892 37 892 35Q892 19 885 5Q880 0 869 0Q864 0 828 1T736 2Q675 2 644 2T609 1Q592 1 592 11Q592 13 594 25Q598 41 602 43T625 46Q652 46 685 49Q699 52 704 61Q706 65 742 207T813 490T848 631L654 322Q458 10 453 5Q451 4 449 3Q444 0 433 0Q418 0 415 7Q413 11 374 317L335 624L267 354Q200 88 200 79Q206 46 272 46H282Q288 41 289 37T286 19Q282 3 278 1Q274 0 267 0Q265 0 255 0T221 1T157 2Q127 2 95 1T58 0Q43 0 39 2T35 11Q35 13 38 25T43 40Q45 46 65 46Q135 46 154 86Q158 92 223 354T289 629Z"></path></g><g data-mml-node="mi" transform="translate(2033,0)"><path data-c="1D456" d="M184 600Q184 624 203 642T247 661Q265 661 277 649T290 619Q290 596 270 577T226 557Q211 557 198 567T184 600ZM21 287Q21 295 30 318T54 369T98 420T158 442Q197 442 223 419T250 357Q250 340 236 301T196 196T154 83Q149 61 149 51Q149 26 166 26Q175 26 185 29T208 43T235 78T260 137Q263 149 265 151T282 153Q302 153 302 143Q302 135 293 112T268 61T223 11T161 -11Q129 -11 102 10T74 74Q74 91 79 106T122 220Q160 321 166 341T173 380Q173 404 156 404H154Q124 404 99 371T61 287Q60 286 59 284T58 281T56 279T53 278T49 278T41 278H27Q21 284 21 287Z"></path></g><g data-mml-node="msub" transform="translate(2378,0)"><g data-mml-node="mi"><path data-c="1D45B" d="M21 287Q22 293 24 303T36 341T56 388T89 425T135 442Q171 442 195 424T225 390T231 369Q231 367 232 367L243 378Q304 442 382 442Q436 442 469 415T503 336T465 179T427 52Q427 26 444 26Q450 26 453 27Q482 32 505 65T540 145Q542 153 560 153Q580 153 580 145Q580 144 576 130Q568 101 554 73T508 17T439 -10Q392 -10 371 17T350 73Q350 92 386 193T423 345Q423 404 379 404H374Q288 404 229 303L222 291L189 157Q156 26 151 16Q138 -11 108 -11Q95 -11 87 -5T76 7T74 17Q74 30 112 180T152 343Q153 348 153 366Q153 405 129 405Q91 405 66 305Q60 285 60 284Q58 278 41 278H27Q21 284 21 287Z"></path></g><g data-mml-node="mi" transform="translate(633,-150) scale(0.707)"><path data-c="1D464" d="M580 385Q580 406 599 424T641 443Q659 443 674 425T690 368Q690 339 671 253Q656 197 644 161T609 80T554 12T482 -11Q438 -11 404 5T355 48Q354 47 352 44Q311 -11 252 -11Q226 -11 202 -5T155 14T118 53T104 116Q104 170 138 262T173 379Q173 380 173 381Q173 390 173 393T169 400T158 404H154Q131 404 112 385T82 344T65 302T57 280Q55 278 41 278H27Q21 284 21 287Q21 293 29 315T52 366T96 418T161 441Q204 441 227 416T250 358Q250 340 217 250T184 111Q184 65 205 46T258 26Q301 26 334 87L339 96V119Q339 122 339 128T340 136T341 143T342 152T345 165T348 182T354 206T362 238T373 281Q402 395 406 404Q419 431 449 431Q468 431 475 421T483 402Q483 389 454 274T422 142Q420 131 420 107V100Q420 85 423 71T442 42T487 26Q558 26 600 148Q609 171 620 213T632 273Q632 306 619 325T593 357T580 385Z"></path></g></g><g data-mml-node="mo" transform="translate(3567.3,0) translate(0 -0.5)"><path data-c="7C" d="M139 -249H137Q125 -249 119 -235V251L120 737Q130 750 139 750Q152 750 159 735V-235Q151 -249 141 -249H139Z"></path></g><g data-mml-node="mo" transform="translate(4123.1,0)"><path data-c="3D" d="M56 347Q56 360 70 367H707Q722 359 722 347Q722 336 708 328L390 327H72Q56 332 56 347ZM56 153Q56 168 72 173H708Q722 163 722 153Q722 140 707 133H70Q56 140 56 153Z"></path></g><g data-mml-node="mo" transform="translate(5178.8,0) translate(0 -0.5)"><path data-c="7C" d="M139 -249H137Q125 -249 119 -235V251L120 737Q130 750 139 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678Q415 674 451 396L487 117L510 154Q534 190 574 254T662 394Q837 673 839 675Q840 676 842 678T846 681L852 683H948Q965 683 988 683T1017 684Q1051 684 1051 673Q1051 668 1048 656T1045 643Q1041 637 1008 637Q968 636 957 634T939 623Q936 618 867 340T797 59Q797 55 798 54T805 50T822 48T855 46H886Q892 37 892 35Q892 19 885 5Q880 0 869 0Q864 0 828 1T736 2Q675 2 644 2T609 1Q592 1 592 11Q592 13 594 25Q598 41 602 43T625 46Q652 46 685 49Q699 52 704 61Q706 65 742 207T813 490T848 631L654 322Q458 10 453 5Q451 4 449 3Q444 0 433 0Q418 0 415 7Q413 11 374 317L335 624L267 354Q200 88 200 79Q206 46 272 46H282Q288 41 289 37T286 19Q282 3 278 1Q274 0 267 0Q265 0 255 0T221 1T157 2Q127 2 95 1T58 0Q43 0 39 2T35 11Q35 13 38 25T43 40Q45 46 65 46Q135 46 154 86Q158 92 223 354T289 629Z"></path></g><g data-mml-node="mi" transform="translate(7211.8,0)"><path data-c="1D44E" d="M33 157Q33 258 109 349T280 441Q331 441 370 392Q386 422 416 422Q429 422 439 414T449 394Q449 381 412 234T374 68Q374 43 381 35T402 26Q411 27 422 35Q443 55 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+<li>最大的无符号数值比补码的最大值的两倍大1<br><mjx-container class="MathJax" jax="SVG" display="true"><svg style="vertical-align: -0.357ex;" xmlns="http://www.w3.org/2000/svg" width="23.386ex" height="1.902ex" role="img" focusable="false" viewBox="0 -683 10336.6 840.8"><g stroke="currentColor" fill="currentColor" stroke-width="0" transform="scale(1,-1)"><g data-mml-node="math"><g data-mml-node="mi"><path data-c="1D448" d="M107 637Q73 637 71 641Q70 643 70 649Q70 673 81 682Q83 683 98 683Q139 681 234 681Q268 681 297 681T342 682T362 682Q378 682 378 672Q378 670 376 658Q371 641 366 638H364Q362 638 359 638T352 638T343 637T334 637Q295 636 284 634T266 623Q265 621 238 518T184 302T154 169Q152 155 152 140Q152 86 183 55T269 24Q336 24 403 69T501 205L552 406Q599 598 599 606Q599 633 535 637Q511 637 511 648Q511 650 513 660Q517 676 519 679T529 683Q532 683 561 682T645 680Q696 680 723 681T752 682Q767 682 767 672Q767 650 759 642Q756 637 737 637Q666 633 648 597Q646 592 598 404Q557 235 548 205Q515 105 433 42T263 -22Q171 -22 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678Q415 674 451 396L487 117L510 154Q534 190 574 254T662 394Q837 673 839 675Q840 676 842 678T846 681L852 683H948Q965 683 988 683T1017 684Q1051 684 1051 673Q1051 668 1048 656T1045 643Q1041 637 1008 637Q968 636 957 634T939 623Q936 618 867 340T797 59Q797 55 798 54T805 50T822 48T855 46H886Q892 37 892 35Q892 19 885 5Q880 0 869 0Q864 0 828 1T736 2Q675 2 644 2T609 1Q592 1 592 11Q592 13 594 25Q598 41 602 43T625 46Q652 46 685 49Q699 52 704 61Q706 65 742 207T813 490T848 631L654 322Q458 10 453 5Q451 4 449 3Q444 0 433 0Q418 0 415 7Q413 11 374 317L335 624L267 354Q200 88 200 79Q206 46 272 46H282Q288 41 289 37T286 19Q282 3 278 1Q274 0 267 0Q265 0 255 0T221 1T157 2Q127 2 95 1T58 0Q43 0 39 2T35 11Q35 13 38 25T43 40Q45 46 65 46Q135 46 154 86Q158 92 223 354T289 629Z"></path></g><g data-mml-node="mi" transform="translate(6923.8,0)"><path data-c="1D44E" d="M33 157Q33 258 109 349T280 441Q331 441 370 392Q386 422 416 422Q429 422 439 414T449 394Q449 381 412 234T374 68Q374 43 381 35T402 26Q411 27 422 35Q443 55 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385Z"></path></g></g><g data-mml-node="mo" transform="translate(8836.4,0)"><path data-c="2B" d="M56 237T56 250T70 270H369V420L370 570Q380 583 389 583Q402 583 409 568V270H707Q722 262 722 250T707 230H409V-68Q401 -82 391 -82H389H387Q375 -82 369 -68V230H70Q56 237 56 250Z"></path></g><g data-mml-node="mn" transform="translate(9836.6,0)"><path data-c="31" d="M213 578L200 573Q186 568 160 563T102 556H83V602H102Q149 604 189 617T245 641T273 663Q275 666 285 666Q294 666 302 660V361L303 61Q310 54 315 52T339 48T401 46H427V0H416Q395 3 257 3Q121 3 100 0H88V46H114Q136 46 152 46T177 47T193 50T201 52T207 57T213 61V578Z"></path></g></g></g></svg></mjx-container></li>
+</ol>
+<p>C语言标准并没有要求要用补码形式来表示有符号整数，但是几乎所有的机器都是这么做的。关于整数数据类型的取值范围和表示，Java标准是非常明确的。</p>
+<blockquote>
+<p>数学角度解释和推导</p>
+</blockquote>
+<p>有符号数的其他表示方法</p>
+<ul>
+<li><strong>反码</strong>（Ones’s Complement）：除了最高有效位的权重是 <mjx-container class="MathJax" jax="SVG"><svg style="vertical-align: -0.791ex;" xmlns="http://www.w3.org/2000/svg" width="12.616ex" height="2.713ex" role="img" focusable="false" viewBox="0 -849.5 5576.1 1199"><g stroke="currentColor" fill="currentColor" stroke-width="0" transform="scale(1,-1)"><g data-mml-node="math"><g data-mml-node="mo"><path data-c="2212" d="M84 237T84 250T98 270H679Q694 262 694 250T679 230H98Q84 237 84 250Z"></path></g><g data-mml-node="mrow" transform="translate(944.7,0)"><g data-mml-node="mo" transform="translate(0 -0.5)"><path data-c="28" d="M152 251Q152 646 388 850H416Q422 844 422 841Q422 837 403 816T357 753T302 649T255 482T236 250Q236 124 255 19T301 -147T356 -251T403 -315T422 -340Q422 -343 416 -349H388Q359 -325 332 -296T271 -213T212 -97T170 56T152 251Z"></path></g><g data-mml-node="msup" transform="translate(458,0)"><g data-mml-node="mn"><path data-c="32" d="M109 429Q82 429 66 447T50 491Q50 562 103 614T235 666Q326 666 387 610T449 465Q449 422 429 383T381 315T301 241Q265 210 201 149L142 93L218 92Q375 92 385 97Q392 99 409 186V189H449V186Q448 183 436 95T421 3V0H50V19V31Q50 38 56 46T86 81Q115 113 136 137Q145 147 170 174T204 211T233 244T261 278T284 308T305 340T320 369T333 401T340 431T343 464Q343 527 309 573T212 619Q179 619 154 602T119 569T109 550Q109 549 114 549Q132 549 151 535T170 489Q170 464 154 447T109 429Z"></path></g><g data-mml-node="TeXAtom" transform="translate(533,363) scale(0.707)" data-mjx-texclass="ORD"><g data-mml-node="mi"><path data-c="1D464" d="M580 385Q580 406 599 424T641 443Q659 443 674 425T690 368Q690 339 671 253Q656 197 644 161T609 80T554 12T482 -11Q438 -11 404 5T355 48Q354 47 352 44Q311 -11 252 -11Q226 -11 202 -5T155 14T118 53T104 116Q104 170 138 262T173 379Q173 380 173 381Q173 390 173 393T169 400T158 404H154Q131 404 112 385T82 344T65 302T57 280Q55 278 41 278H27Q21 284 21 287Q21 293 29 315T52 366T96 418T161 441Q204 441 227 416T250 358Q250 340 217 250T184 111Q184 65 205 46T258 26Q301 26 334 87L339 96V119Q339 122 339 128T340 136T341 143T342 152T345 165T348 182T354 206T362 238T373 281Q402 395 406 404Q419 431 449 431Q468 431 475 421T483 402Q483 389 454 274T422 142Q420 131 420 107V100Q420 85 423 71T442 42T487 26Q558 26 600 148Q609 171 620 213T632 273Q632 306 619 325T593 357T580 385Z"></path></g><g data-mml-node="mo" transform="translate(716,0)"><path data-c="2212" d="M84 237T84 250T98 270H679Q694 262 694 250T679 230H98Q84 237 84 250Z"></path></g><g data-mml-node="mn" transform="translate(1494,0)"><path data-c="31" d="M213 578L200 573Q186 568 160 563T102 556H83V602H102Q149 604 189 617T245 641T273 663Q275 666 285 666Q294 666 302 660V361L303 61Q310 54 315 52T339 48T401 46H427V0H416Q395 3 257 3Q121 3 100 0H88V46H114Q136 46 152 46T177 47T193 50T201 52T207 57T213 61V578Z"></path></g></g></g><g data-mml-node="mo" transform="translate(2673.2,0)"><path data-c="2212" d="M84 237T84 250T98 270H679Q694 262 694 250T679 230H98Q84 237 84 250Z"></path></g><g data-mml-node="mn" transform="translate(3673.4,0)"><path data-c="31" d="M213 578L200 573Q186 568 160 563T102 556H83V602H102Q149 604 189 617T245 641T273 663Q275 666 285 666Q294 666 302 660V361L303 61Q310 54 315 52T339 48T401 46H427V0H416Q395 3 257 3Q121 3 100 0H88V46H114Q136 46 152 46T177 47T193 50T201 52T207 57T213 61V578Z"></path></g><g data-mml-node="mo" transform="translate(4173.4,0) translate(0 -0.5)"><path data-c="29" d="M305 251Q305 -145 69 -349H56Q43 -349 39 -347T35 -338Q37 -333 60 -307T108 -239T160 -136T204 27T221 250T204 473T160 636T108 740T60 807T35 839Q35 850 50 850H56H69Q197 743 256 566Q305 425 305 251Z"></path></g></g></g></g></svg></mjx-container> 而不是 <mjx-container class="MathJax" jax="SVG"><svg style="vertical-align: -0.186ex;" xmlns="http://www.w3.org/2000/svg" width="6.269ex" height="2.072ex" role="img" focusable="false" viewBox="0 -833.9 2771 915.9"><g stroke="currentColor" fill="currentColor" stroke-width="0" transform="scale(1,-1)"><g data-mml-node="math"><g data-mml-node="mo"><path data-c="2212" d="M84 237T84 250T98 270H679Q694 262 694 250T679 230H98Q84 237 84 250Z"></path></g><g data-mml-node="msup" transform="translate(778,0)"><g data-mml-node="mn"><path data-c="32" d="M109 429Q82 429 66 447T50 491Q50 562 103 614T235 666Q326 666 387 610T449 465Q449 422 429 383T381 315T301 241Q265 210 201 149L142 93L218 92Q375 92 385 97Q392 99 409 186V189H449V186Q448 183 436 95T421 3V0H50V19V31Q50 38 56 46T86 81Q115 113 136 137Q145 147 170 174T204 211T233 244T261 278T284 308T305 340T320 369T333 401T340 431T343 464Q343 527 309 573T212 619Q179 619 154 602T119 569T109 550Q109 549 114 549Q132 549 151 535T170 489Q170 464 154 447T109 429Z"></path></g><g data-mml-node="TeXAtom" transform="translate(533,363) scale(0.707)" data-mjx-texclass="ORD"><g data-mml-node="mi"><path data-c="1D464" d="M580 385Q580 406 599 424T641 443Q659 443 674 425T690 368Q690 339 671 253Q656 197 644 161T609 80T554 12T482 -11Q438 -11 404 5T355 48Q354 47 352 44Q311 -11 252 -11Q226 -11 202 -5T155 14T118 53T104 116Q104 170 138 262T173 379Q173 380 173 381Q173 390 173 393T169 400T158 404H154Q131 404 112 385T82 344T65 302T57 280Q55 278 41 278H27Q21 284 21 287Q21 293 29 315T52 366T96 418T161 441Q204 441 227 416T250 358Q250 340 217 250T184 111Q184 65 205 46T258 26Q301 26 334 87L339 96V119Q339 122 339 128T340 136T341 143T342 152T345 165T348 182T354 206T362 238T373 281Q402 395 406 404Q419 431 449 431Q468 431 475 421T483 402Q483 389 454 274T422 142Q420 131 420 107V100Q420 85 423 71T442 42T487 26Q558 26 600 148Q609 171 620 213T632 273Q632 306 619 325T593 357T580 385Z"></path></g><g data-mml-node="mo" transform="translate(716,0)"><path data-c="2212" d="M84 237T84 250T98 270H679Q694 262 694 250T679 230H98Q84 237 84 250Z"></path></g><g data-mml-node="mn" transform="translate(1494,0)"><path data-c="31" d="M213 578L200 573Q186 568 160 563T102 556H83V602H102Q149 604 189 617T245 641T273 663Q275 666 285 666Q294 666 302 660V361L303 61Q310 54 315 52T339 48T401 46H427V0H416Q395 3 257 3Q121 3 100 0H88V46H114Q136 46 152 46T177 47T193 50T201 52T207 57T213 61V578Z"></path></g></g></g></g></g></svg></mjx-container>，它和补码是一样的：<br><mjx-container class="MathJax" jax="SVG" display="true"><svg style="vertical-align: -2.819ex;" xmlns="http://www.w3.org/2000/svg" width="40.019ex" height="6.712ex" role="img" focusable="false" viewBox="0 -1720.9 17688.5 2966.8"><g stroke="currentColor" fill="currentColor" stroke-width="0" transform="scale(1,-1)"><g data-mml-node="math"><g data-mml-node="mi"><path data-c="1D435" d="M231 637Q204 637 199 638T194 649Q194 676 205 682Q206 683 335 683Q594 683 608 681Q671 671 713 636T756 544Q756 480 698 429T565 360L555 357Q619 348 660 311T702 219Q702 146 630 78T453 1Q446 0 242 0Q42 0 39 2Q35 5 35 10Q35 17 37 24Q42 43 47 45Q51 46 62 46H68Q95 46 128 49Q142 52 147 61Q150 65 219 339T288 628Q288 635 231 637ZM649 544Q649 574 634 600T585 634Q578 636 493 637Q473 637 451 637T416 636H403Q388 635 384 626Q382 622 352 506Q352 503 351 500L320 374H401Q482 374 494 376Q554 386 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+<li><strong>原码</strong>（Sign-Magnitude）：最高有效位是符号位，用来确定剩下的位应该取负权还是正权：<br><mjx-container class="MathJax" jax="SVG" display="true"><svg style="vertical-align: -2.827ex;" xmlns="http://www.w3.org/2000/svg" width="31.982ex" height="6.785ex" role="img" focusable="false" viewBox="0 -1749.5 14136.1 2999"><g stroke="currentColor" fill="currentColor" stroke-width="0" transform="scale(1,-1)"><g data-mml-node="math"><g data-mml-node="mi"><path data-c="1D435" d="M231 637Q204 637 199 638T194 649Q194 676 205 682Q206 683 335 683Q594 683 608 681Q671 671 713 636T756 544Q756 480 698 429T565 360L555 357Q619 348 660 311T702 219Q702 146 630 78T453 1Q446 0 242 0Q42 0 39 2Q35 5 35 10Q35 17 37 24Q42 43 47 45Q51 46 62 46H68Q95 46 128 49Q142 52 147 61Q150 65 219 339T288 628Q288 635 231 637ZM649 544Q649 574 634 600T585 634Q578 636 493 637Q473 637 451 637T416 636H403Q388 635 384 626Q382 622 352 506Q352 503 351 500L320 374H401Q482 374 494 376Q554 386 601 434T649 544ZM595 229Q595 273 572 302T512 336Q506 337 429 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578L200 573Q186 568 160 563T102 556H83V602H102Q149 604 189 617T245 641T273 663Q275 666 285 666Q294 666 302 660V361L303 61Q310 54 315 52T339 48T401 46H427V0H416Q395 3 257 3Q121 3 100 0H88V46H114Q136 46 152 46T177 47T193 50T201 52T207 57T213 61V578Z"></path></g></g></g></g></g><g data-mml-node="mo" transform="translate(8715.3,0)"><path data-c="B7" d="M78 250Q78 274 95 292T138 310Q162 310 180 294T199 251Q199 226 182 208T139 190T96 207T78 250Z"></path></g><g data-mml-node="mrow" transform="translate(9215.6,0)"><g data-mml-node="mo" transform="translate(0 -0.5)"><path data-c="28" d="M758 -1237T758 -1240T752 -1249H736Q718 -1249 717 -1248Q711 -1245 672 -1199Q237 -706 237 251T672 1700Q697 1730 716 1749Q718 1750 735 1750H752Q758 1744 758 1741Q758 1737 740 1713T689 1644T619 1537T540 1380T463 1176Q348 802 348 251Q348 -242 441 -599T744 -1218Q758 -1237 758 -1240Z"></path></g><g data-mml-node="munderover" transform="translate(792,0)"><g data-mml-node="mo"><path data-c="2211" d="M60 948Q63 950 665 950H1267L1325 815Q1384 677 1388 669H1348L1341 683Q1320 724 1285 761Q1235 809 1174 838T1033 881T882 898T699 902H574H543H251L259 891Q722 258 724 252Q725 250 724 246Q721 243 460 -56L196 -356Q196 -357 407 -357Q459 -357 548 -357T676 -358Q812 -358 896 -353T1063 -332T1204 -283T1307 -196Q1328 -170 1348 -124H1388Q1388 -125 1381 -145T1356 -210T1325 -294L1267 -449L666 -450Q64 -450 61 -448Q55 -446 55 -439Q55 -437 57 -433L590 177Q590 178 557 222T452 366T322 544L56 909L55 924Q55 945 60 948Z"></path></g><g data-mml-node="TeXAtom" transform="translate(148.2,-1087.9) scale(0.707)" data-mjx-texclass="ORD"><g data-mml-node="mi"><path data-c="1D456" d="M184 600Q184 624 203 642T247 661Q265 661 277 649T290 619Q290 596 270 577T226 557Q211 557 198 567T184 600ZM21 287Q21 295 30 318T54 369T98 420T158 442Q197 442 223 419T250 357Q250 340 236 301T196 196T154 83Q149 61 149 51Q149 26 166 26Q175 26 185 29T208 43T235 78T260 137Q263 149 265 151T282 153Q302 153 302 143Q302 135 293 112T268 61T223 11T161 -11Q129 -11 102 10T74 74Q74 91 79 106T122 220Q160 321 166 341T173 380Q173 404 156 404H154Q124 404 99 371T61 287Q60 286 59 284T58 281T56 279T53 278T49 278T41 278H27Q21 284 21 287Z"></path></g><g data-mml-node="mo" transform="translate(345,0)"><path data-c="3D" d="M56 347Q56 360 70 367H707Q722 359 722 347Q722 336 708 328L390 327H72Q56 332 56 347ZM56 153Q56 168 72 173H708Q722 163 722 153Q722 140 707 133H70Q56 140 56 153Z"></path></g><g data-mml-node="mn" transform="translate(1123,0)"><path data-c="30" d="M96 585Q152 666 249 666Q297 666 345 640T423 548Q460 465 460 320Q460 165 417 83Q397 41 362 16T301 -15T250 -22Q224 -22 198 -16T137 16T82 83Q39 165 39 320Q39 494 96 585ZM321 597Q291 629 250 629Q208 629 178 597Q153 571 145 525T137 333Q137 175 145 125T181 46Q209 16 250 16Q290 16 318 46Q347 76 354 130T362 333Q362 478 354 524T321 597Z"></path></g></g><g data-mml-node="TeXAtom" transform="translate(17,1150) scale(0.707)" data-mjx-texclass="ORD"><g data-mml-node="mi"><path data-c="1D464" d="M580 385Q580 406 599 424T641 443Q659 443 674 425T690 368Q690 339 671 253Q656 197 644 161T609 80T554 12T482 -11Q438 -11 404 5T355 48Q354 47 352 44Q311 -11 252 -11Q226 -11 202 -5T155 14T118 53T104 116Q104 170 138 262T173 379Q173 380 173 381Q173 390 173 393T169 400T158 404H154Q131 404 112 385T82 344T65 302T57 280Q55 278 41 278H27Q21 284 21 287Q21 293 29 315T52 366T96 418T161 441Q204 441 227 416T250 358Q250 340 217 250T184 111Q184 65 205 46T258 26Q301 26 334 87L339 96V119Q339 122 339 128T340 136T341 143T342 152T345 165T348 182T354 206T362 238T373 281Q402 395 406 404Q419 431 449 431Q468 431 475 421T483 402Q483 389 454 274T422 142Q420 131 420 107V100Q420 85 423 71T442 42T487 26Q558 26 600 148Q609 171 620 213T632 273Q632 306 619 325T593 357T580 385Z"></path></g><g data-mml-node="mo" transform="translate(716,0)"><path data-c="2212" d="M84 237T84 250T98 270H679Q694 262 694 250T679 230H98Q84 237 84 250Z"></path></g><g data-mml-node="mn" transform="translate(1494,0)"><path data-c="32" d="M109 429Q82 429 66 447T50 491Q50 562 103 614T235 666Q326 666 387 610T449 465Q449 422 429 383T381 315T301 241Q265 210 201 149L142 93L218 92Q375 92 385 97Q392 99 409 186V189H449V186Q448 183 436 95T421 3V0H50V19V31Q50 38 56 46T86 81Q115 113 136 137Q145 147 170 174T204 211T233 244T261 278T284 308T305 340T320 369T333 401T340 431T343 464Q343 527 309 573T212 619Q179 619 154 602T119 569T109 550Q109 549 114 549Q132 549 151 535T170 489Q170 464 154 447T109 429Z"></path></g></g></g><g data-mml-node="msub" transform="translate(2402.7,0)"><g data-mml-node="mi"><path data-c="1D465" d="M52 289Q59 331 106 386T222 442Q257 442 286 424T329 379Q371 442 430 442Q467 442 494 420T522 361Q522 332 508 314T481 292T458 288Q439 288 427 299T415 328Q415 374 465 391Q454 404 425 404Q412 404 406 402Q368 386 350 336Q290 115 290 78Q290 50 306 38T341 26Q378 26 414 59T463 140Q466 150 469 151T485 153H489Q504 153 504 145Q504 144 502 134Q486 77 440 33T333 -11Q263 -11 227 52Q186 -10 133 -10H127Q78 -10 57 16T35 71Q35 103 54 123T99 143Q142 143 142 101Q142 81 130 66T107 46T94 41L91 40Q91 39 97 36T113 29T132 26Q168 26 194 71Q203 87 217 139T245 247T261 313Q266 340 266 352Q266 380 251 392T217 404Q177 404 142 372T93 290Q91 281 88 280T72 278H58Q52 284 52 289Z"></path></g><g data-mml-node="TeXAtom" transform="translate(605,-150) scale(0.707)" data-mjx-texclass="ORD"><g data-mml-node="mi"><path data-c="1D456" d="M184 600Q184 624 203 642T247 661Q265 661 277 649T290 619Q290 596 270 577T226 557Q211 557 198 567T184 600ZM21 287Q21 295 30 318T54 369T98 420T158 442Q197 442 223 419T250 357Q250 340 236 301T196 196T154 83Q149 61 149 51Q149 26 166 26Q175 26 185 29T208 43T235 78T260 137Q263 149 265 151T282 153Q302 153 302 143Q302 135 293 112T268 61T223 11T161 -11Q129 -11 102 10T74 74Q74 91 79 106T122 220Q160 321 166 341T173 380Q173 404 156 404H154Q124 404 99 371T61 287Q60 286 59 284T58 281T56 279T53 278T49 278T41 278H27Q21 284 21 287Z"></path></g></g></g><g data-mml-node="msup" transform="translate(3301.6,0)"><g data-mml-node="mn"><path data-c="32" d="M109 429Q82 429 66 447T50 491Q50 562 103 614T235 666Q326 666 387 610T449 465Q449 422 429 383T381 315T301 241Q265 210 201 149L142 93L218 92Q375 92 385 97Q392 99 409 186V189H449V186Q448 183 436 95T421 3V0H50V19V31Q50 38 56 46T86 81Q115 113 136 137Q145 147 170 174T204 211T233 244T261 278T284 308T305 340T320 369T333 401T340 431T343 464Q343 527 309 573T212 619Q179 619 154 602T119 569T109 550Q109 549 114 549Q132 549 151 535T170 489Q170 464 154 447T109 429Z"></path></g><g data-mml-node="mi" transform="translate(533,413) scale(0.707)"><path data-c="1D456" d="M184 600Q184 624 203 642T247 661Q265 661 277 649T290 619Q290 596 270 577T226 557Q211 557 198 567T184 600ZM21 287Q21 295 30 318T54 369T98 420T158 442Q197 442 223 419T250 357Q250 340 236 301T196 196T154 83Q149 61 149 51Q149 26 166 26Q175 26 185 29T208 43T235 78T260 137Q263 149 265 151T282 153Q302 153 302 143Q302 135 293 112T268 61T223 11T161 -11Q129 -11 102 10T74 74Q74 91 79 106T122 220Q160 321 166 341T173 380Q173 404 156 404H154Q124 404 99 371T61 287Q60 286 59 284T58 281T56 279T53 278T49 278T41 278H27Q21 284 21 287Z"></path></g></g><g data-mml-node="mo" transform="translate(4128.6,0) translate(0 -0.5)"><path data-c="29" d="M33 1741Q33 1750 51 1750H60H65Q73 1750 81 1743T119 1700Q554 1207 554 251Q554 -707 119 -1199Q76 -1250 66 -1250Q65 -1250 62 -1250T56 -1249Q55 -1249 53 -1249T49 -1250Q33 -1250 33 -1239Q33 -1236 50 -1214T98 -1150T163 -1052T238 -910T311 -727Q443 -335 443 251Q443 402 436 532T405 831T339 1142T224 1438T50 1716Q33 1737 33 1741Z"></path></g></g></g></g></svg></mjx-container></li>
+</ul>
+<p>这两种表示方法都有一个奇怪的属性，就是对于数字 0 有两种不同的编码方式，把 [00…0] 都是解释为 +0，而值 -0 在原码中表示为 [10…0]，在反码中表示为 [11…1]。虽然过去生产过基于反码表示的机器，但是几乎所有的现代机器都使用补码。在浮点数中仍有使用原码编码。</p>
+<blockquote>
+<p>尽管在实际应用中已经存在胜出者，但是了解其他有符号数的表示方式仍有助于理解编码本身。</p>
+</blockquote>
+<p>补码（Two’s Complement）：对于非负数 x，我们用 <mjx-container class="MathJax" jax="SVG"><svg style="vertical-align: -0.186ex;" xmlns="http://www.w3.org/2000/svg" width="6.524ex" height="1.715ex" role="img" focusable="false" viewBox="0 -676.2 2883.7 758.2"><g stroke="currentColor" fill="currentColor" stroke-width="0" transform="scale(1,-1)"><g data-mml-node="math"><g data-mml-node="msup"><g data-mml-node="mn"><path data-c="32" d="M109 429Q82 429 66 447T50 491Q50 562 103 614T235 666Q326 666 387 610T449 465Q449 422 429 383T381 315T301 241Q265 210 201 149L142 93L218 92Q375 92 385 97Q392 99 409 186V189H449V186Q448 183 436 95T421 3V0H50V19V31Q50 38 56 46T86 81Q115 113 136 137Q145 147 170 174T204 211T233 244T261 278T284 308T305 340T320 369T333 401T340 431T343 464Q343 527 309 573T212 619Q179 619 154 602T119 569T109 550Q109 549 114 549Q132 549 151 535T170 489Q170 464 154 447T109 429Z"></path></g><g data-mml-node="mi" transform="translate(533,363) scale(0.707)"><path data-c="1D464" d="M580 385Q580 406 599 424T641 443Q659 443 674 425T690 368Q690 339 671 253Q656 197 644 161T609 80T554 12T482 -11Q438 -11 404 5T355 48Q354 47 352 44Q311 -11 252 -11Q226 -11 202 -5T155 14T118 53T104 116Q104 170 138 262T173 379Q173 380 173 381Q173 390 173 393T169 400T158 404H154Q131 404 112 385T82 344T65 302T57 280Q55 278 41 278H27Q21 284 21 287Q21 293 29 315T52 366T96 418T161 441Q204 441 227 416T250 358Q250 340 217 250T184 111Q184 65 205 46T258 26Q301 26 334 87L339 96V119Q339 122 339 128T340 136T341 143T342 152T345 165T348 182T354 206T362 238T373 281Q402 395 406 404Q419 431 449 431Q468 431 475 421T483 402Q483 389 454 274T422 142Q420 131 420 107V100Q420 85 423 71T442 42T487 26Q558 26 600 148Q609 171 620 213T632 273Q632 306 619 325T593 357T580 385Z"></path></g></g><g data-mml-node="mo" transform="translate(1311.5,0)"><path data-c="2212" d="M84 237T84 250T98 270H679Q694 262 694 250T679 230H98Q84 237 84 250Z"></path></g><g data-mml-node="mi" transform="translate(2311.7,0)"><path data-c="1D465" d="M52 289Q59 331 106 386T222 442Q257 442 286 424T329 379Q371 442 430 442Q467 442 494 420T522 361Q522 332 508 314T481 292T458 288Q439 288 427 299T415 328Q415 374 465 391Q454 404 425 404Q412 404 406 402Q368 386 350 336Q290 115 290 78Q290 50 306 38T341 26Q378 26 414 59T463 140Q466 150 469 151T485 153H489Q504 153 504 145Q504 144 502 134Q486 77 440 33T333 -11Q263 -11 227 52Q186 -10 133 -10H127Q78 -10 57 16T35 71Q35 103 54 123T99 143Q142 143 142 101Q142 81 130 66T107 46T94 41L91 40Q91 39 97 36T113 29T132 26Q168 26 194 71Q203 87 217 139T245 247T261 313Q266 340 266 352Q266 380 251 392T217 404Q177 404 142 372T93 290Q91 281 88 280T72 278H58Q52 284 52 289Z"></path></g></g></g></svg></mjx-container> 来计算 -x 的 w 位表示。<br>反码（Ones’ Complement）用 <mjx-container class="MathJax" jax="SVG"><svg style="vertical-align: -0.566ex;" xmlns="http://www.w3.org/2000/svg" width="13.248ex" height="2.262ex" role="img" focusable="false" viewBox="0 -750 5855.8 1000"><g stroke="currentColor" fill="currentColor" stroke-width="0" transform="scale(1,-1)"><g data-mml-node="math"><g data-mml-node="mrow"><g data-mml-node="mo"><path data-c="5B" d="M118 -250V750H255V710H158V-210H255V-250H118Z"></path></g><g data-mml-node="mn" transform="translate(278,0)"><path data-c="31" d="M213 578L200 573Q186 568 160 563T102 556H83V602H102Q149 604 189 617T245 641T273 663Q275 666 285 666Q294 666 302 660V361L303 61Q310 54 315 52T339 48T401 46H427V0H416Q395 3 257 3Q121 3 100 0H88V46H114Q136 46 152 46T177 47T193 50T201 52T207 57T213 61V578Z"></path><path data-c="31" d="M213 578L200 573Q186 568 160 563T102 556H83V602H102Q149 604 189 617T245 641T273 663Q275 666 285 666Q294 666 302 660V361L303 61Q310 54 315 52T339 48T401 46H427V0H416Q395 3 257 3Q121 3 100 0H88V46H114Q136 46 152 46T177 47T193 50T201 52T207 57T213 61V578Z" transform="translate(500,0)"></path><path data-c="31" d="M213 578L200 573Q186 568 160 563T102 556H83V602H102Q149 604 189 617T245 641T273 663Q275 666 285 666Q294 666 302 660V361L303 61Q310 54 315 52T339 48T401 46H427V0H416Q395 3 257 3Q121 3 100 0H88V46H114Q136 46 152 46T177 47T193 50T201 52T207 57T213 61V578Z" transform="translate(1000,0)"></path></g><g data-mml-node="mo" transform="translate(1944.7,0)"><path data-c="2026" d="M78 60Q78 84 95 102T138 120Q162 120 180 104T199 61Q199 36 182 18T139 0T96 17T78 60ZM525 60Q525 84 542 102T585 120Q609 120 627 104T646 61Q646 36 629 18T586 0T543 17T525 60ZM972 60Q972 84 989 102T1032 120Q1056 120 1074 104T1093 61Q1093 36 1076 18T1033 0T990 17T972 60Z"></path></g><g data-mml-node="mn" transform="translate(3283.3,0)"><path data-c="31" d="M213 578L200 573Q186 568 160 563T102 556H83V602H102Q149 604 189 617T245 641T273 663Q275 666 285 666Q294 666 302 660V361L303 61Q310 54 315 52T339 48T401 46H427V0H416Q395 3 257 3Q121 3 100 0H88V46H114Q136 46 152 46T177 47T193 50T201 52T207 57T213 61V578Z"></path></g><g data-mml-node="mo" transform="translate(3783.3,0)"><path data-c="5D" d="M22 710V750H159V-250H22V-210H119V710H22Z"></path></g></g><g data-mml-node="mo" transform="translate(4283.6,0)"><path data-c="2212" d="M84 237T84 250T98 270H679Q694 262 694 250T679 230H98Q84 237 84 250Z"></path></g><g data-mml-node="mi" transform="translate(5283.8,0)"><path data-c="1D465" d="M52 289Q59 331 106 386T222 442Q257 442 286 424T329 379Q371 442 430 442Q467 442 494 420T522 361Q522 332 508 314T481 292T458 288Q439 288 427 299T415 328Q415 374 465 391Q454 404 425 404Q412 404 406 402Q368 386 350 336Q290 115 290 78Q290 50 306 38T341 26Q378 26 414 59T463 140Q466 150 469 151T485 153H489Q504 153 504 145Q504 144 502 134Q486 77 440 33T333 -11Q263 -11 227 52Q186 -10 133 -10H127Q78 -10 57 16T35 71Q35 103 54 123T99 143Q142 143 142 101Q142 81 130 66T107 46T94 41L91 40Q91 39 97 36T113 29T132 26Q168 26 194 71Q203 87 217 139T245 247T261 313Q266 340 266 352Q266 380 251 392T217 404Q177 404 142 372T93 290Q91 281 88 280T72 278H58Q52 284 52 289Z"></path></g></g></g></svg></mjx-container> 来计算 -x 的反码表示。</p>
+<blockquote>
+<p>了解术语来源比单纯的记忆术语有意思多了！</p>
+</blockquote>
+<h2 id="参考文章"><a href="#参考文章" class="headerlink" title="参考文章"></a>参考文章</h2><ul>
+<li>《深入理解计算机系统》</li>
+</ul>
+
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diff --git a/archives/2020/08/index.html b/archives/2020/08/index.html
index 4047b709..24feaae1 100644
--- a/archives/2020/08/index.html
+++ b/archives/2020/08/index.html
@@ -151,7 +151,7 @@ <h1 class="site-title">Moralok</h1>
   <nav class="site-state">
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+          <span class="site-state-item-count">49</span>
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@@ -188,7 +188,7 @@ <h1 class="site-title">Moralok</h1>
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   </span>
   <span class="post-meta-item">
     <span class="post-meta-item-icon">
       <i class="fa fa-coffee"></i>
     </span>
-    <span title="站点阅读时长">6:56</span>
+    <span title="站点阅读时长">7:09</span>
   </span>
 </div>
   <div class="powered-by">由 <a href="https://hexo.io/" rel="noopener" target="_blank">Hexo</a> & <a href="https://theme-next.js.org/" rel="noopener" target="_blank">NexT.Gemini</a> 强力驱动
diff --git a/archives/2020/09/index.html b/archives/2020/09/index.html
index 4ed19d9f..2392292e 100644
--- a/archives/2020/09/index.html
+++ b/archives/2020/09/index.html
@@ -151,7 +151,7 @@ <h1 class="site-title">Moralok</h1>
   <nav class="site-state">
       <div class="site-state-item site-state-posts">
         <a href="/archives/">
-          <span class="site-state-item-count">48</span>
+          <span class="site-state-item-count">49</span>
           <span class="site-state-item-name">日志</span>
         </a>
       </div>
@@ -188,7 +188,7 @@ <h1 class="site-title">Moralok</h1>
     <div class="post-content">
       <div class="collection-title">
         
-        <span class="collection-header">还行! 目前共计 48 篇日志。 继续努力。</span>
+        <span class="collection-header">还行! 目前共计 49 篇日志。 继续努力。</span>
       </div>
 
       
@@ -242,13 +242,13 @@ <h1 class="site-title">Moralok</h1>
     <span class="post-meta-item-icon">
       <i class="fa fa-chart-line"></i>
     </span>
-    <span title="站点总字数">125k</span>
+    <span title="站点总字数">129k</span>
   </span>
   <span class="post-meta-item">
     <span class="post-meta-item-icon">
       <i class="fa fa-coffee"></i>
     </span>
-    <span title="站点阅读时长">6:56</span>
+    <span title="站点阅读时长">7:09</span>
   </span>
 </div>
   <div class="powered-by">由 <a href="https://hexo.io/" rel="noopener" target="_blank">Hexo</a> & <a href="https://theme-next.js.org/" rel="noopener" target="_blank">NexT.Gemini</a> 强力驱动
diff --git a/archives/2020/index.html b/archives/2020/index.html
index 9a4f3a98..cda79197 100644
--- a/archives/2020/index.html
+++ b/archives/2020/index.html
@@ -151,7 +151,7 @@ <h1 class="site-title">Moralok</h1>
   <nav class="site-state">
       <div class="site-state-item site-state-posts">
         <a href="/archives/">
-          <span class="site-state-item-count">48</span>
+          <span class="site-state-item-count">49</span>
           <span class="site-state-item-name">日志</span>
         </a>
       </div>
@@ -188,7 +188,7 @@ <h1 class="site-title">Moralok</h1>
     <div class="post-content">
       <div class="collection-title">
         
-        <span class="collection-header">还行! 目前共计 48 篇日志。 继续努力。</span>
+        <span class="collection-header">还行! 目前共计 49 篇日志。 继续努力。</span>
       </div>
 
       
@@ -302,13 +302,13 @@ <h1 class="site-title">Moralok</h1>
     <span class="post-meta-item-icon">
       <i class="fa fa-chart-line"></i>
     </span>
-    <span title="站点总字数">125k</span>
+    <span title="站点总字数">129k</span>
   </span>
   <span class="post-meta-item">
     <span class="post-meta-item-icon">
       <i class="fa fa-coffee"></i>
     </span>
-    <span title="站点阅读时长">6:56</span>
+    <span title="站点阅读时长">7:09</span>
   </span>
 </div>
   <div class="powered-by">由 <a href="https://hexo.io/" rel="noopener" target="_blank">Hexo</a> & <a href="https://theme-next.js.org/" rel="noopener" target="_blank">NexT.Gemini</a> 强力驱动
diff --git a/archives/2023/05/index.html b/archives/2023/05/index.html
index ed475b29..77df90b8 100644
--- a/archives/2023/05/index.html
+++ b/archives/2023/05/index.html
@@ -151,7 +151,7 @@ <h1 class="site-title">Moralok</h1>
   <nav class="site-state">
       <div class="site-state-item site-state-posts">
         <a href="/archives/">
-          <span class="site-state-item-count">48</span>
+          <span class="site-state-item-count">49</span>
           <span class="site-state-item-name">日志</span>
         </a>
       </div>
@@ -188,7 +188,7 @@ <h1 class="site-title">Moralok</h1>
     <div class="post-content">
       <div class="collection-title">
         
-        <span class="collection-header">还行! 目前共计 48 篇日志。 继续努力。</span>
+        <span class="collection-header">还行! 目前共计 49 篇日志。 继续努力。</span>
       </div>
 
       
@@ -242,13 +242,13 @@ <h1 class="site-title">Moralok</h1>
     <span class="post-meta-item-icon">
       <i class="fa fa-chart-line"></i>
     </span>
-    <span title="站点总字数">125k</span>
+    <span title="站点总字数">129k</span>
   </span>
   <span class="post-meta-item">
     <span class="post-meta-item-icon">
       <i class="fa fa-coffee"></i>
     </span>
-    <span title="站点阅读时长">6:56</span>
+    <span title="站点阅读时长">7:09</span>
   </span>
 </div>
   <div class="powered-by">由 <a href="https://hexo.io/" rel="noopener" target="_blank">Hexo</a> & <a href="https://theme-next.js.org/" rel="noopener" target="_blank">NexT.Gemini</a> 强力驱动
diff --git a/archives/2023/06/index.html b/archives/2023/06/index.html
index 722fa9b7..b4f8cd17 100644
--- a/archives/2023/06/index.html
+++ b/archives/2023/06/index.html
@@ -151,7 +151,7 @@ <h1 class="site-title">Moralok</h1>
   <nav class="site-state">
       <div class="site-state-item site-state-posts">
         <a href="/archives/">
-          <span class="site-state-item-count">48</span>
+          <span class="site-state-item-count">49</span>
           <span class="site-state-item-name">日志</span>
         </a>
       </div>
@@ -188,7 +188,7 @@ <h1 class="site-title">Moralok</h1>
     <div class="post-content">
       <div class="collection-title">
         
-        <span class="collection-header">还行! 目前共计 48 篇日志。 继续努力。</span>
+        <span class="collection-header">还行! 目前共计 49 篇日志。 继续努力。</span>
       </div>
 
       
@@ -382,13 +382,13 @@ <h1 class="site-title">Moralok</h1>
     <span class="post-meta-item-icon">
       <i class="fa fa-chart-line"></i>
     </span>
-    <span title="站点总字数">125k</span>
+    <span title="站点总字数">129k</span>
   </span>
   <span class="post-meta-item">
     <span class="post-meta-item-icon">
       <i class="fa fa-coffee"></i>
     </span>
-    <span title="站点阅读时长">6:56</span>
+    <span title="站点阅读时长">7:09</span>
   </span>
 </div>
   <div class="powered-by">由 <a href="https://hexo.io/" rel="noopener" target="_blank">Hexo</a> & <a href="https://theme-next.js.org/" rel="noopener" target="_blank">NexT.Gemini</a> 强力驱动
diff --git a/archives/2023/07/index.html b/archives/2023/07/index.html
index d9408b42..7a22e0df 100644
--- a/archives/2023/07/index.html
+++ b/archives/2023/07/index.html
@@ -151,7 +151,7 @@ <h1 class="site-title">Moralok</h1>
   <nav class="site-state">
       <div class="site-state-item site-state-posts">
         <a href="/archives/">
-          <span class="site-state-item-count">48</span>
+          <span class="site-state-item-count">49</span>
           <span class="site-state-item-name">日志</span>
         </a>
       </div>
@@ -188,7 +188,7 @@ <h1 class="site-title">Moralok</h1>
     <div class="post-content">
       <div class="collection-title">
         
-        <span class="collection-header">还行! 目前共计 48 篇日志。 继续努力。</span>
+        <span class="collection-header">还行! 目前共计 49 篇日志。 继续努力。</span>
       </div>
 
       
@@ -242,13 +242,13 @@ <h1 class="site-title">Moralok</h1>
     <span class="post-meta-item-icon">
       <i class="fa fa-chart-line"></i>
     </span>
-    <span title="站点总字数">125k</span>
+    <span title="站点总字数">129k</span>
   </span>
   <span class="post-meta-item">
     <span class="post-meta-item-icon">
       <i class="fa fa-coffee"></i>
     </span>
-    <span title="站点阅读时长">6:56</span>
+    <span title="站点阅读时长">7:09</span>
   </span>
 </div>
   <div class="powered-by">由 <a href="https://hexo.io/" rel="noopener" target="_blank">Hexo</a> & <a href="https://theme-next.js.org/" rel="noopener" target="_blank">NexT.Gemini</a> 强力驱动
diff --git a/archives/2023/08/index.html b/archives/2023/08/index.html
index f98a5883..42fc4369 100644
--- a/archives/2023/08/index.html
+++ b/archives/2023/08/index.html
@@ -151,7 +151,7 @@ <h1 class="site-title">Moralok</h1>
   <nav class="site-state">
       <div class="site-state-item site-state-posts">
         <a href="/archives/">
-          <span class="site-state-item-count">48</span>
+          <span class="site-state-item-count">49</span>
           <span class="site-state-item-name">日志</span>
         </a>
       </div>
@@ -188,7 +188,7 @@ <h1 class="site-title">Moralok</h1>
     <div class="post-content">
       <div class="collection-title">
         
-        <span class="collection-header">还行! 目前共计 48 篇日志。 继续努力。</span>
+        <span class="collection-header">还行! 目前共计 49 篇日志。 继续努力。</span>
       </div>
 
       
@@ -262,13 +262,13 @@ <h1 class="site-title">Moralok</h1>
     <span class="post-meta-item-icon">
       <i class="fa fa-chart-line"></i>
     </span>
-    <span title="站点总字数">125k</span>
+    <span title="站点总字数">129k</span>
   </span>
   <span class="post-meta-item">
     <span class="post-meta-item-icon">
       <i class="fa fa-coffee"></i>
     </span>
-    <span title="站点阅读时长">6:56</span>
+    <span title="站点阅读时长">7:09</span>
   </span>
 </div>
   <div class="powered-by">由 <a href="https://hexo.io/" rel="noopener" target="_blank">Hexo</a> & <a href="https://theme-next.js.org/" rel="noopener" target="_blank">NexT.Gemini</a> 强力驱动
diff --git a/archives/2023/11/index.html b/archives/2023/11/index.html
index cd376dd5..508fb3f1 100644
--- a/archives/2023/11/index.html
+++ b/archives/2023/11/index.html
@@ -151,7 +151,7 @@ <h1 class="site-title">Moralok</h1>
   <nav class="site-state">
       <div class="site-state-item site-state-posts">
         <a href="/archives/">
-          <span class="site-state-item-count">48</span>
+          <span class="site-state-item-count">49</span>
           <span class="site-state-item-name">日志</span>
         </a>
       </div>
@@ -188,7 +188,7 @@ <h1 class="site-title">Moralok</h1>
     <div class="post-content">
       <div class="collection-title">
         
-        <span class="collection-header">还行! 目前共计 48 篇日志。 继续努力。</span>
+        <span class="collection-header">还行! 目前共计 49 篇日志。 继续努力。</span>
       </div>
 
       
@@ -425,13 +425,13 @@ <h1 class="site-title">Moralok</h1>
     <span class="post-meta-item-icon">
       <i class="fa fa-chart-line"></i>
     </span>
-    <span title="站点总字数">125k</span>
+    <span title="站点总字数">129k</span>
   </span>
   <span class="post-meta-item">
     <span class="post-meta-item-icon">
       <i class="fa fa-coffee"></i>
     </span>
-    <span title="站点阅读时长">6:56</span>
+    <span title="站点阅读时长">7:09</span>
   </span>
 </div>
   <div class="powered-by">由 <a href="https://hexo.io/" rel="noopener" target="_blank">Hexo</a> & <a href="https://theme-next.js.org/" rel="noopener" target="_blank">NexT.Gemini</a> 强力驱动
diff --git a/archives/2023/11/page/2/index.html b/archives/2023/11/page/2/index.html
index 77554707..af39dda9 100644
--- a/archives/2023/11/page/2/index.html
+++ b/archives/2023/11/page/2/index.html
@@ -151,7 +151,7 @@ <h1 class="site-title">Moralok</h1>
   <nav class="site-state">
       <div class="site-state-item site-state-posts">
         <a href="/archives/">
-          <span class="site-state-item-count">48</span>
+          <span class="site-state-item-count">49</span>
           <span class="site-state-item-name">日志</span>
         </a>
       </div>
@@ -188,7 +188,7 @@ <h1 class="site-title">Moralok</h1>
     <div class="post-content">
       <div class="collection-title">
         
-        <span class="collection-header">还行! 目前共计 48 篇日志。 继续努力。</span>
+        <span class="collection-header">还行! 目前共计 49 篇日志。 继续努力。</span>
       </div>
 
       
@@ -285,13 +285,13 @@ <h1 class="site-title">Moralok</h1>
     <span class="post-meta-item-icon">
       <i class="fa fa-chart-line"></i>
     </span>
-    <span title="站点总字数">125k</span>
+    <span title="站点总字数">129k</span>
   </span>
   <span class="post-meta-item">
     <span class="post-meta-item-icon">
       <i class="fa fa-coffee"></i>
     </span>
-    <span title="站点阅读时长">6:56</span>
+    <span title="站点阅读时长">7:09</span>
   </span>
 </div>
   <div class="powered-by">由 <a href="https://hexo.io/" rel="noopener" target="_blank">Hexo</a> & <a href="https://theme-next.js.org/" rel="noopener" target="_blank">NexT.Gemini</a> 强力驱动
diff --git a/archives/2023/12/index.html b/archives/2023/12/index.html
index d68a1550..cfe15d8b 100644
--- a/archives/2023/12/index.html
+++ b/archives/2023/12/index.html
@@ -151,7 +151,7 @@ <h1 class="site-title">Moralok</h1>
   <nav class="site-state">
       <div class="site-state-item site-state-posts">
         <a href="/archives/">
-          <span class="site-state-item-count">48</span>
+          <span class="site-state-item-count">49</span>
           <span class="site-state-item-name">日志</span>
         </a>
       </div>
@@ -188,7 +188,7 @@ <h1 class="site-title">Moralok</h1>
     <div class="post-content">
       <div class="collection-title">
         
-        <span class="collection-header">还行! 目前共计 48 篇日志。 继续努力。</span>
+        <span class="collection-header">还行! 目前共计 49 篇日志。 继续努力。</span>
       </div>
 
       
@@ -425,13 +425,13 @@ <h1 class="site-title">Moralok</h1>
     <span class="post-meta-item-icon">
       <i class="fa fa-chart-line"></i>
     </span>
-    <span title="站点总字数">125k</span>
+    <span title="站点总字数">129k</span>
   </span>
   <span class="post-meta-item">
     <span class="post-meta-item-icon">
       <i class="fa fa-coffee"></i>
     </span>
-    <span title="站点阅读时长">6:56</span>
+    <span title="站点阅读时长">7:09</span>
   </span>
 </div>
   <div class="powered-by">由 <a href="https://hexo.io/" rel="noopener" target="_blank">Hexo</a> & <a href="https://theme-next.js.org/" rel="noopener" target="_blank">NexT.Gemini</a> 强力驱动
diff --git a/archives/2023/12/page/2/index.html b/archives/2023/12/page/2/index.html
index 9e58b76f..f36f34c0 100644
--- a/archives/2023/12/page/2/index.html
+++ b/archives/2023/12/page/2/index.html
@@ -151,7 +151,7 @@ <h1 class="site-title">Moralok</h1>
   <nav class="site-state">
       <div class="site-state-item site-state-posts">
         <a href="/archives/">
-          <span class="site-state-item-count">48</span>
+          <span class="site-state-item-count">49</span>
           <span class="site-state-item-name">日志</span>
         </a>
       </div>
@@ -188,7 +188,7 @@ <h1 class="site-title">Moralok</h1>
     <div class="post-content">
       <div class="collection-title">
         
-        <span class="collection-header">还行! 目前共计 48 篇日志。 继续努力。</span>
+        <span class="collection-header">还行! 目前共计 49 篇日志。 继续努力。</span>
       </div>
 
       
@@ -325,13 +325,13 @@ <h1 class="site-title">Moralok</h1>
     <span class="post-meta-item-icon">
       <i class="fa fa-chart-line"></i>
     </span>
-    <span title="站点总字数">125k</span>
+    <span title="站点总字数">129k</span>
   </span>
   <span class="post-meta-item">
     <span class="post-meta-item-icon">
       <i class="fa fa-coffee"></i>
     </span>
-    <span title="站点阅读时长">6:56</span>
+    <span title="站点阅读时长">7:09</span>
   </span>
 </div>
   <div class="powered-by">由 <a href="https://hexo.io/" rel="noopener" target="_blank">Hexo</a> & <a href="https://theme-next.js.org/" rel="noopener" target="_blank">NexT.Gemini</a> 强力驱动
diff --git a/archives/2023/index.html b/archives/2023/index.html
index aa0c1603..784e0c12 100644
--- a/archives/2023/index.html
+++ b/archives/2023/index.html
@@ -151,7 +151,7 @@ <h1 class="site-title">Moralok</h1>
   <nav class="site-state">
       <div class="site-state-item site-state-posts">
         <a href="/archives/">
-          <span class="site-state-item-count">48</span>
+          <span class="site-state-item-count">49</span>
           <span class="site-state-item-name">日志</span>
         </a>
       </div>
@@ -188,7 +188,7 @@ <h1 class="site-title">Moralok</h1>
     <div class="post-content">
       <div class="collection-title">
         
-        <span class="collection-header">还行! 目前共计 48 篇日志。 继续努力。</span>
+        <span class="collection-header">还行! 目前共计 49 篇日志。 继续努力。</span>
       </div>
 
       
@@ -425,13 +425,13 @@ <h1 class="site-title">Moralok</h1>
     <span class="post-meta-item-icon">
       <i class="fa fa-chart-line"></i>
     </span>
-    <span title="站点总字数">125k</span>
+    <span title="站点总字数">129k</span>
   </span>
   <span class="post-meta-item">
     <span class="post-meta-item-icon">
       <i class="fa fa-coffee"></i>
     </span>
-    <span title="站点阅读时长">6:56</span>
+    <span title="站点阅读时长">7:09</span>
   </span>
 </div>
   <div class="powered-by">由 <a href="https://hexo.io/" rel="noopener" target="_blank">Hexo</a> & <a href="https://theme-next.js.org/" rel="noopener" target="_blank">NexT.Gemini</a> 强力驱动
diff --git a/archives/2023/page/2/index.html b/archives/2023/page/2/index.html
index f76f0d34..7d7ac25d 100644
--- a/archives/2023/page/2/index.html
+++ b/archives/2023/page/2/index.html
@@ -151,7 +151,7 @@ <h1 class="site-title">Moralok</h1>
   <nav class="site-state">
       <div class="site-state-item site-state-posts">
         <a href="/archives/">
-          <span class="site-state-item-count">48</span>
+          <span class="site-state-item-count">49</span>
           <span class="site-state-item-name">日志</span>
         </a>
       </div>
@@ -188,7 +188,7 @@ <h1 class="site-title">Moralok</h1>
     <div class="post-content">
       <div class="collection-title">
         
-        <span class="collection-header">还行! 目前共计 48 篇日志。 继续努力。</span>
+        <span class="collection-header">还行! 目前共计 49 篇日志。 继续努力。</span>
       </div>
 
       
@@ -425,13 +425,13 @@ <h1 class="site-title">Moralok</h1>
     <span class="post-meta-item-icon">
       <i class="fa fa-chart-line"></i>
     </span>
-    <span title="站点总字数">125k</span>
+    <span title="站点总字数">129k</span>
   </span>
   <span class="post-meta-item">
     <span class="post-meta-item-icon">
       <i class="fa fa-coffee"></i>
     </span>
-    <span title="站点阅读时长">6:56</span>
+    <span title="站点阅读时长">7:09</span>
   </span>
 </div>
   <div class="powered-by">由 <a href="https://hexo.io/" rel="noopener" target="_blank">Hexo</a> & <a href="https://theme-next.js.org/" rel="noopener" target="_blank">NexT.Gemini</a> 强力驱动
diff --git a/archives/2023/page/3/index.html b/archives/2023/page/3/index.html
index 5c9509d9..8251090a 100644
--- a/archives/2023/page/3/index.html
+++ b/archives/2023/page/3/index.html
@@ -151,7 +151,7 @@ <h1 class="site-title">Moralok</h1>
   <nav class="site-state">
       <div class="site-state-item site-state-posts">
         <a href="/archives/">
-          <span class="site-state-item-count">48</span>
+          <span class="site-state-item-count">49</span>
           <span class="site-state-item-name">日志</span>
         </a>
       </div>
@@ -188,7 +188,7 @@ <h1 class="site-title">Moralok</h1>
     <div class="post-content">
       <div class="collection-title">
         
-        <span class="collection-header">还行! 目前共计 48 篇日志。 继续努力。</span>
+        <span class="collection-header">还行! 目前共计 49 篇日志。 继续努力。</span>
       </div>
 
       
@@ -425,13 +425,13 @@ <h1 class="site-title">Moralok</h1>
     <span class="post-meta-item-icon">
       <i class="fa fa-chart-line"></i>
     </span>
-    <span title="站点总字数">125k</span>
+    <span title="站点总字数">129k</span>
   </span>
   <span class="post-meta-item">
     <span class="post-meta-item-icon">
       <i class="fa fa-coffee"></i>
     </span>
-    <span title="站点阅读时长">6:56</span>
+    <span title="站点阅读时长">7:09</span>
   </span>
 </div>
   <div class="powered-by">由 <a href="https://hexo.io/" rel="noopener" target="_blank">Hexo</a> & <a href="https://theme-next.js.org/" rel="noopener" target="_blank">NexT.Gemini</a> 强力驱动
diff --git a/archives/2023/page/4/index.html b/archives/2023/page/4/index.html
index c2b6678e..0a81392a 100644
--- a/archives/2023/page/4/index.html
+++ b/archives/2023/page/4/index.html
@@ -151,7 +151,7 @@ <h1 class="site-title">Moralok</h1>
   <nav class="site-state">
       <div class="site-state-item site-state-posts">
         <a href="/archives/">
-          <span class="site-state-item-count">48</span>
+          <span class="site-state-item-count">49</span>
           <span class="site-state-item-name">日志</span>
         </a>
       </div>
@@ -188,7 +188,7 @@ <h1 class="site-title">Moralok</h1>
     <div class="post-content">
       <div class="collection-title">
         
-        <span class="collection-header">还行! 目前共计 48 篇日志。 继续努力。</span>
+        <span class="collection-header">还行! 目前共计 49 篇日志。 继续努力。</span>
       </div>
 
       
@@ -425,13 +425,13 @@ <h1 class="site-title">Moralok</h1>
     <span class="post-meta-item-icon">
       <i class="fa fa-chart-line"></i>
     </span>
-    <span title="站点总字数">125k</span>
+    <span title="站点总字数">129k</span>
   </span>
   <span class="post-meta-item">
     <span class="post-meta-item-icon">
       <i class="fa fa-coffee"></i>
     </span>
-    <span title="站点阅读时长">6:56</span>
+    <span title="站点阅读时长">7:09</span>
   </span>
 </div>
   <div class="powered-by">由 <a href="https://hexo.io/" rel="noopener" target="_blank">Hexo</a> & <a href="https://theme-next.js.org/" rel="noopener" target="_blank">NexT.Gemini</a> 强力驱动
diff --git a/archives/2024/01/index.html b/archives/2024/01/index.html
index 9755ae62..565e5bce 100644
--- a/archives/2024/01/index.html
+++ b/archives/2024/01/index.html
@@ -151,7 +151,7 @@ <h1 class="site-title">Moralok</h1>
   <nav class="site-state">
       <div class="site-state-item site-state-posts">
         <a href="/archives/">
-          <span class="site-state-item-count">48</span>
+          <span class="site-state-item-count">49</span>
           <span class="site-state-item-name">日志</span>
         </a>
       </div>
@@ -188,7 +188,7 @@ <h1 class="site-title">Moralok</h1>
     <div class="post-content">
       <div class="collection-title">
         
-        <span class="collection-header">还行! 目前共计 48 篇日志。 继续努力。</span>
+        <span class="collection-header">还行! 目前共计 49 篇日志。 继续努力。</span>
       </div>
 
       
@@ -302,13 +302,13 @@ <h1 class="site-title">Moralok</h1>
     <span class="post-meta-item-icon">
       <i class="fa fa-chart-line"></i>
     </span>
-    <span title="站点总字数">125k</span>
+    <span title="站点总字数">129k</span>
   </span>
   <span class="post-meta-item">
     <span class="post-meta-item-icon">
       <i class="fa fa-coffee"></i>
     </span>
-    <span title="站点阅读时长">6:56</span>
+    <span title="站点阅读时长">7:09</span>
   </span>
 </div>
   <div class="powered-by">由 <a href="https://hexo.io/" rel="noopener" target="_blank">Hexo</a> & <a href="https://theme-next.js.org/" rel="noopener" target="_blank">NexT.Gemini</a> 强力驱动
diff --git a/archives/2024/03/index.html b/archives/2024/03/index.html
new file mode 100644
index 00000000..70fec47e
--- /dev/null
+++ b/archives/2024/03/index.html
@@ -0,0 +1,293 @@
+<!DOCTYPE html>
+<html lang="zh-CN">
+<head>
+  <meta charset="UTF-8">
+<meta name="viewport" content="width=device-width">
+<meta name="theme-color" content="#222"><meta name="generator" content="Hexo 7.1.1">
+
+  <link rel="apple-touch-icon" sizes="180x180" href="/images/apple-touch-icon-next.png">
+  <link rel="icon" type="image/png" sizes="32x32" href="/images/favicon-32x32-next.png">
+  <link rel="icon" type="image/png" sizes="16x16" href="/images/favicon-16x16-next.png">
+  <link rel="mask-icon" href="/images/logo.svg" color="#222">
+
+<link rel="stylesheet" href="/css/main.css">
+
+
+
+<link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/font-awesome/6.5.0/css/all.min.css" integrity="sha256-yIDrPSXHZdOZhAqiBP7CKzIwMQmRCJ8UeB8Jo17YC4o=" crossorigin="anonymous">
+  <link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/animate.css/3.1.1/animate.min.css" integrity="sha256-PR7ttpcvz8qrF57fur/yAx1qXMFJeJFiA6pSzWi0OIE=" crossorigin="anonymous">
+
+<script class="next-config" data-name="main" type="application/json">{"hostname":"www.moralok.com","root":"/","images":"/images","scheme":"Gemini","darkmode":false,"version":"8.19.1","exturl":false,"sidebar":{"position":"left","display":"always","padding":18,"offset":12},"copycode":{"enable":false,"style":null},"fold":{"enable":false,"height":500},"bookmark":{"enable":false,"color":"#222","save":"auto"},"mediumzoom":false,"lazyload":false,"pangu":false,"comments":{"style":"tabs","active":null,"storage":true,"lazyload":false,"nav":null},"stickytabs":false,"motion":{"enable":true,"async":false,"transition":{"menu_item":"fadeInDown","post_block":"fadeIn","post_header":"fadeInDown","post_body":"fadeInDown","coll_header":"fadeInLeft","sidebar":"fadeInUp"}},"prism":false,"i18n":{"placeholder":"搜索...","empty":"没有找到任何搜索结果：${query}","hits_time":"找到 ${hits} 个搜索结果（用时 ${time} 毫秒）","hits":"找到 ${hits} 个搜索结果"},"path":"/search.xml","localsearch":{"enable":true,"trigger":"auto","top_n_per_article":1,"unescape":false,"preload":false}}</script><script src="/js/config.js"></script>
+
+    <meta name="description" content="假如生命只剩一天">
+<meta property="og:type" content="website">
+<meta property="og:title" content="Moralok">
+<meta property="og:url" content="https://www.moralok.com/archives/2024/03/index.html">
+<meta property="og:site_name" content="Moralok">
+<meta property="og:description" content="假如生命只剩一天">
+<meta property="og:locale" content="zh_CN">
+<meta property="article:author" content="Moralok">
+<meta name="twitter:card" content="summary">
+
+
+<link rel="canonical" href="https://www.moralok.com/archives/2024/03/">
+
+
+
+<script class="next-config" data-name="page" type="application/json">{"sidebar":"","isHome":false,"isPost":false,"lang":"zh-CN","comments":"","permalink":"","path":"archives/2024/03/index.html","title":""}</script>
+
+<script class="next-config" data-name="calendar" type="application/json">""</script>
+<title>归档 | Moralok</title>
+  
+    <script async src="https://www.googletagmanager.com/gtag/js?id=G-2MBCXKHJL0"></script>
+  <script class="next-config" data-name="google_analytics" type="application/json">{"tracking_id":"G-2MBCXKHJL0","only_pageview":false,"measure_protocol_api_secret":null}</script>
+  <script src="/js/third-party/analytics/google-analytics.js"></script>
+
+
+
+
+
+
+
+
+  <noscript>
+    <link rel="stylesheet" href="/css/noscript.css">
+  </noscript>
+</head>
+
+<body itemscope itemtype="http://schema.org/WebPage" class="use-motion">
+  <div class="headband"></div>
+
+  <main class="main">
+    <div class="column">
+      <header class="header" itemscope itemtype="http://schema.org/WPHeader"><div class="site-brand-container">
+  <div class="site-nav-toggle">
+    <div class="toggle" aria-label="切换导航栏" role="button">
+        <span class="toggle-line"></span>
+        <span class="toggle-line"></span>
+        <span class="toggle-line"></span>
+    </div>
+  </div>
+
+  <div class="site-meta">
+
+    <a href="/" class="brand" rel="start">
+      <i class="logo-line"></i>
+      <h1 class="site-title">Moralok</h1>
+      <i class="logo-line"></i>
+    </a>
+  </div>
+
+  <div class="site-nav-right">
+    <div class="toggle popup-trigger" aria-label="搜索" role="button">
+        <i class="fa fa-search fa-fw fa-lg"></i>
+    </div>
+  </div>
+</div>
+
+
+
+<nav class="site-nav">
+  <ul class="main-menu menu"><li class="menu-item menu-item-home"><a href="/" rel="section"><i class="fa fa-home fa-fw"></i>首页</a></li><li class="menu-item menu-item-tags"><a href="/tags/" rel="section"><i class="fa fa-tags fa-fw"></i>标签</a></li>
+      <li class="menu-item menu-item-search">
+        <a role="button" class="popup-trigger"><i class="fa fa-search fa-fw"></i>搜索
+        </a>
+      </li>
+  </ul>
+</nav>
+
+
+
+  <div class="search-pop-overlay">
+    <div class="popup search-popup"><div class="search-header">
+  <span class="search-icon">
+    <i class="fa fa-search"></i>
+  </span>
+  <div class="search-input-container">
+    <input autocomplete="off" autocapitalize="off" maxlength="80"
+           placeholder="搜索..." spellcheck="false"
+           type="search" class="search-input">
+  </div>
+  <span class="popup-btn-close" role="button">
+    <i class="fa fa-times-circle"></i>
+  </span>
+</div>
+<div class="search-result-container no-result">
+  <div class="search-result-icon">
+    <i class="fa fa-spinner fa-pulse fa-5x"></i>
+  </div>
+</div>
+
+    </div>
+  </div>
+
+</header>
+        
+  
+  <aside class="sidebar">
+
+    <div class="sidebar-inner sidebar-overview-active">
+      <ul class="sidebar-nav">
+        <li class="sidebar-nav-toc">
+          文章目录
+        </li>
+        <li class="sidebar-nav-overview">
+          站点概览
+        </li>
+      </ul>
+
+      <div class="sidebar-panel-container">
+        <!--noindex-->
+        <div class="post-toc-wrap sidebar-panel">
+        </div>
+        <!--/noindex-->
+
+        <div class="site-overview-wrap sidebar-panel">
+          <div class="site-author animated" itemprop="author" itemscope itemtype="http://schema.org/Person">
+  <p class="site-author-name" itemprop="name">Moralok</p>
+  <div class="site-description" itemprop="description">假如生命只剩一天</div>
+</div>
+<div class="site-state-wrap animated">
+  <nav class="site-state">
+      <div class="site-state-item site-state-posts">
+        <a href="/archives/">
+          <span class="site-state-item-count">49</span>
+          <span class="site-state-item-name">日志</span>
+        </a>
+      </div>
+      <div class="site-state-item site-state-tags">
+          <a href="/tags/">
+        <span class="site-state-item-count">36</span>
+        <span class="site-state-item-name">标签</span></a>
+      </div>
+  </nav>
+</div>
+  <div class="links-of-author animated">
+      <span class="links-of-author-item">
+        <a href="https://github.com/moralok" title="GitHub → https:&#x2F;&#x2F;github.com&#x2F;moralok" rel="noopener me" target="_blank"><i class="fab fa-github fa-fw"></i>GitHub</a>
+      </span>
+  </div>
+
+        </div>
+      </div>
+    </div>
+
+    
+  </aside>
+
+
+    </div>
+
+    <div class="main-inner archive posts-collapse">
+
+
+  
+  
+  
+  <div class="post-block">
+    <div class="post-content">
+      <div class="collection-title">
+        
+        <span class="collection-header">还行! 目前共计 49 篇日志。 继续努力。</span>
+      </div>
+
+      
+    <div class="collection-year">
+      <span class="collection-header">2024</span>
+    </div>
+
+  <article itemscope itemtype="http://schema.org/Article">
+    <header class="post-header">
+      <div class="post-meta-container">
+        <time itemprop="dateCreated"
+              datetime="2024-03-12T07:48:32+08:00"
+              content="2024-03-12">
+          03-12
+        </time>
+      </div>
+
+      <div class="post-title">
+        <a class="post-title-link" href="/2024/03/11/representating-and-manipulating-information/" itemprop="url">
+          <span itemprop="name">信息的表示和处理</span>
+        </a>
+      </div>
+
+      
+    </header>
+  </article>
+
+
+    </div>
+  </div>
+  
+  
+  
+
+</div>
+  </main>
+
+  <footer class="footer">
+    <div class="footer-inner">
+
+  <div class="copyright">
+    &copy; 
+    <span itemprop="copyrightYear">2024</span>
+    <span class="with-love">
+      <i class="fa fa-heart"></i>
+    </span>
+    <span class="author" itemprop="copyrightHolder">Moralok</span>
+  </div>
+<div class="wordcount">
+  <span class="post-meta-item">
+    <span class="post-meta-item-icon">
+      <i class="fa fa-chart-line"></i>
+    </span>
+    <span title="站点总字数">129k</span>
+  </span>
+  <span class="post-meta-item">
+    <span class="post-meta-item-icon">
+      <i class="fa fa-coffee"></i>
+    </span>
+    <span title="站点阅读时长">7:09</span>
+  </span>
+</div>
+  <div class="powered-by">由 <a href="https://hexo.io/" rel="noopener" target="_blank">Hexo</a> & <a href="https://theme-next.js.org/" rel="noopener" target="_blank">NexT.Gemini</a> 强力驱动
+  </div>
+
+    </div>
+  </footer>
+
+  
+  <div class="back-to-top" role="button" aria-label="返回顶部">
+    <i class="fa fa-arrow-up fa-lg"></i>
+    <span>0%</span>
+  </div>
+
+<noscript>
+  <div class="noscript-warning">Theme NexT works best with JavaScript enabled</div>
+</noscript>
+
+
+  
+  <script src="https://cdnjs.cloudflare.com/ajax/libs/animejs/3.2.1/anime.min.js" integrity="sha256-XL2inqUJaslATFnHdJOi9GfQ60on8Wx1C2H8DYiN1xY=" crossorigin="anonymous"></script>
+<script src="/js/comments.js"></script><script src="/js/utils.js"></script><script src="/js/motion.js"></script><script src="/js/next-boot.js"></script>
+
+  <script src="https://cdnjs.cloudflare.com/ajax/libs/hexo-generator-searchdb/1.4.1/search.js" integrity="sha256-1kfA5uHPf65M5cphT2dvymhkuyHPQp5A53EGZOnOLmc=" crossorigin="anonymous"></script>
+<script src="/js/third-party/search/local-search.js"></script>
+
+
+
+
+
+
+
+  
+
+
+  <script class="next-config" data-name="leancloud_visitors" type="application/json">{"enable":true,"app_id":"3EC6DlIt15eVYStwSVsDsQ2P-MdYXbMMI","app_key":"KKBQicvLunsmAfgH3DJJXvng","server_url":null,"security":false}</script>
+  <script src="/js/third-party/statistics/lean-analytics.js"></script>
+
+
+
+</body>
+</html>
diff --git a/archives/2024/index.html b/archives/2024/index.html
index e1d3434b..8c8eb039 100644
--- a/archives/2024/index.html
+++ b/archives/2024/index.html
@@ -151,7 +151,7 @@ <h1 class="site-title">Moralok</h1>
   <nav class="site-state">
       <div class="site-state-item site-state-posts">
         <a href="/archives/">
-          <span class="site-state-item-count">48</span>
+          <span class="site-state-item-count">49</span>
           <span class="site-state-item-name">日志</span>
         </a>
       </div>
@@ -188,7 +188,7 @@ <h1 class="site-title">Moralok</h1>
     <div class="post-content">
       <div class="collection-title">
         
-        <span class="collection-header">还行! 目前共计 48 篇日志。 继续努力。</span>
+        <span class="collection-header">还行! 目前共计 49 篇日志。 继续努力。</span>
       </div>
 
       
@@ -196,6 +196,26 @@ <h1 class="site-title">Moralok</h1>
       <span class="collection-header">2024</span>
     </div>
 
+  <article itemscope itemtype="http://schema.org/Article">
+    <header class="post-header">
+      <div class="post-meta-container">
+        <time itemprop="dateCreated"
+              datetime="2024-03-12T07:48:32+08:00"
+              content="2024-03-12">
+          03-12
+        </time>
+      </div>
+
+      <div class="post-title">
+        <a class="post-title-link" href="/2024/03/11/representating-and-manipulating-information/" itemprop="url">
+          <span itemprop="name">信息的表示和处理</span>
+        </a>
+      </div>
+
+      
+    </header>
+  </article>
+
   <article itemscope itemtype="http://schema.org/Article">
     <header class="post-header">
       <div class="post-meta-container">
@@ -302,13 +322,13 @@ <h1 class="site-title">Moralok</h1>
     <span class="post-meta-item-icon">
       <i class="fa fa-chart-line"></i>
     </span>
-    <span title="站点总字数">125k</span>
+    <span title="站点总字数">129k</span>
   </span>
   <span class="post-meta-item">
     <span class="post-meta-item-icon">
       <i class="fa fa-coffee"></i>
     </span>
-    <span title="站点阅读时长">6:56</span>
+    <span title="站点阅读时长">7:09</span>
   </span>
 </div>
   <div class="powered-by">由 <a href="https://hexo.io/" rel="noopener" target="_blank">Hexo</a> & <a href="https://theme-next.js.org/" rel="noopener" target="_blank">NexT.Gemini</a> 强力驱动
diff --git a/archives/index.html b/archives/index.html
index eefc9813..a8130a1a 100644
--- a/archives/index.html
+++ b/archives/index.html
@@ -151,7 +151,7 @@ <h1 class="site-title">Moralok</h1>
   <nav class="site-state">
       <div class="site-state-item site-state-posts">
         <a href="/archives/">
-          <span class="site-state-item-count">48</span>
+          <span class="site-state-item-count">49</span>
           <span class="site-state-item-name">日志</span>
         </a>
       </div>
@@ -188,7 +188,7 @@ <h1 class="site-title">Moralok</h1>
     <div class="post-content">
       <div class="collection-title">
         
-        <span class="collection-header">还行! 目前共计 48 篇日志。 继续努力。</span>
+        <span class="collection-header">还行! 目前共计 49 篇日志。 继续努力。</span>
       </div>
 
       
@@ -196,6 +196,26 @@ <h1 class="site-title">Moralok</h1>
       <span class="collection-header">2024</span>
     </div>
 
+  <article itemscope itemtype="http://schema.org/Article">
+    <header class="post-header">
+      <div class="post-meta-container">
+        <time itemprop="dateCreated"
+              datetime="2024-03-12T07:48:32+08:00"
+              content="2024-03-12">
+          03-12
+        </time>
+      </div>
+
+      <div class="post-title">
+        <a class="post-title-link" href="/2024/03/11/representating-and-manipulating-information/" itemprop="url">
+          <span itemprop="name">信息的表示和处理</span>
+        </a>
+      </div>
+
+      
+    </header>
+  </article>
+
   <article itemscope itemtype="http://schema.org/Article">
     <header class="post-header">
       <div class="post-meta-container">
@@ -379,26 +399,6 @@ <h1 class="site-title">Moralok</h1>
     </header>
   </article>
 
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-        <time itemprop="dateCreated"
-              datetime="2023-12-13T12:16:17+08:00"
-              content="2023-12-13">
-          12-13
-        </time>
-      </div>
-
-      <div class="post-title">
-        <a class="post-title-link" href="/2023/12/13/how-to-grant-when-MySQL-started-with-skip-name-resolve-mode/" itemprop="url">
-          <span itemprop="name">当 MySQL 以 skip-name-resolve 模式启动时如何使用 grant 命令</span>
-        </a>
-      </div>
-
-      
-    </header>
-  </article>
-
 
     </div>
   </div>
@@ -428,13 +428,13 @@ <h1 class="site-title">Moralok</h1>
     <span class="post-meta-item-icon">
       <i class="fa fa-chart-line"></i>
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-    <span title="站点总字数">125k</span>
+    <span title="站点总字数">129k</span>
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     <span class="post-meta-item-icon">
       <i class="fa fa-coffee"></i>
     </span>
-    <span title="站点阅读时长">6:56</span>
+    <span title="站点阅读时长">7:09</span>
   </span>
 </div>
   <div class="powered-by">由 <a href="https://hexo.io/" rel="noopener" target="_blank">Hexo</a> & <a href="https://theme-next.js.org/" rel="noopener" target="_blank">NexT.Gemini</a> 强力驱动
diff --git a/archives/page/2/index.html b/archives/page/2/index.html
index 86dded46..8bf5343a 100644
--- a/archives/page/2/index.html
+++ b/archives/page/2/index.html
@@ -151,7 +151,7 @@ <h1 class="site-title">Moralok</h1>
   <nav class="site-state">
       <div class="site-state-item site-state-posts">
         <a href="/archives/">
-          <span class="site-state-item-count">48</span>
+          <span class="site-state-item-count">49</span>
           <span class="site-state-item-name">日志</span>
         </a>
       </div>
@@ -188,7 +188,7 @@ <h1 class="site-title">Moralok</h1>
     <div class="post-content">
       <div class="collection-title">
         
-        <span class="collection-header">还行! 目前共计 48 篇日志。 继续努力。</span>
+        <span class="collection-header">还行! 目前共计 49 篇日志。 继续努力。</span>
       </div>
 
       
@@ -196,6 +196,26 @@ <h1 class="site-title">Moralok</h1>
       <span class="collection-header">2023</span>
     </div>
 
+  <article itemscope itemtype="http://schema.org/Article">
+    <header class="post-header">
+      <div class="post-meta-container">
+        <time itemprop="dateCreated"
+              datetime="2023-12-13T12:16:17+08:00"
+              content="2023-12-13">
+          12-13
+        </time>
+      </div>
+
+      <div class="post-title">
+        <a class="post-title-link" href="/2023/12/13/how-to-grant-when-MySQL-started-with-skip-name-resolve-mode/" itemprop="url">
+          <span itemprop="name">当 MySQL 以 skip-name-resolve 模式启动时如何使用 grant 命令</span>
+        </a>
+      </div>
+
+      
+    </header>
+  </article>
+
   <article itemscope itemtype="http://schema.org/Article">
     <header class="post-header">
       <div class="post-meta-container">
@@ -376,26 +396,6 @@ <h1 class="site-title">Moralok</h1>
     </header>
   </article>
 
-  <article itemscope itemtype="http://schema.org/Article">
-    <header class="post-header">
-      <div class="post-meta-container">
-        <time itemprop="dateCreated"
-              datetime="2023-11-29T13:40:07+08:00"
-              content="2023-11-29">
-          11-29
-        </time>
-      </div>
-
-      <div class="post-title">
-        <a class="post-title-link" href="/2023/11/29/how-does-Dubbo-SPI-adaptive-extension-works/" itemprop="url">
-          <span itemprop="name">Dubbo SPI 自适应拓展的工作原理</span>
-        </a>
-      </div>
-
-      
-    </header>
-  </article>
-
 
     </div>
   </div>
@@ -425,13 +425,13 @@ <h1 class="site-title">Moralok</h1>
     <span class="post-meta-item-icon">
       <i class="fa fa-chart-line"></i>
     </span>
-    <span title="站点总字数">125k</span>
+    <span title="站点总字数">129k</span>
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     <span class="post-meta-item-icon">
       <i class="fa fa-coffee"></i>
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-    <span title="站点阅读时长">6:56</span>
+    <span title="站点阅读时长">7:09</span>
   </span>
 </div>
   <div class="powered-by">由 <a href="https://hexo.io/" rel="noopener" target="_blank">Hexo</a> & <a href="https://theme-next.js.org/" rel="noopener" target="_blank">NexT.Gemini</a> 强力驱动
diff --git a/archives/page/3/index.html b/archives/page/3/index.html
index a602a2d1..89fa2e5a 100644
--- a/archives/page/3/index.html
+++ b/archives/page/3/index.html
@@ -151,7 +151,7 @@ <h1 class="site-title">Moralok</h1>
   <nav class="site-state">
       <div class="site-state-item site-state-posts">
         <a href="/archives/">
-          <span class="site-state-item-count">48</span>
+          <span class="site-state-item-count">49</span>
           <span class="site-state-item-name">日志</span>
         </a>
       </div>
@@ -188,7 +188,7 @@ <h1 class="site-title">Moralok</h1>
     <div class="post-content">
       <div class="collection-title">
         
-        <span class="collection-header">还行! 目前共计 48 篇日志。 继续努力。</span>
+        <span class="collection-header">还行! 目前共计 49 篇日志。 继续努力。</span>
       </div>
 
       
@@ -196,6 +196,26 @@ <h1 class="site-title">Moralok</h1>
       <span class="collection-header">2023</span>
     </div>
 
+  <article itemscope itemtype="http://schema.org/Article">
+    <header class="post-header">
+      <div class="post-meta-container">
+        <time itemprop="dateCreated"
+              datetime="2023-11-29T13:40:07+08:00"
+              content="2023-11-29">
+          11-29
+        </time>
+      </div>
+
+      <div class="post-title">
+        <a class="post-title-link" href="/2023/11/29/how-does-Dubbo-SPI-adaptive-extension-works/" itemprop="url">
+          <span itemprop="name">Dubbo SPI 自适应拓展的工作原理</span>
+        </a>
+      </div>
+
+      
+    </header>
+  </article>
+
   <article itemscope itemtype="http://schema.org/Article">
     <header class="post-header">
       <div class="post-meta-container">
@@ -376,26 +396,6 @@ <h1 class="site-title">Moralok</h1>
     </header>
   </article>
 
-  <article itemscope itemtype="http://schema.org/Article">
-    <header class="post-header">
-      <div class="post-meta-container">
-        <time itemprop="dateCreated"
-              datetime="2023-11-04T19:21:25+08:00"
-              content="2023-11-04">
-          11-04
-        </time>
-      </div>
-
-      <div class="post-title">
-        <a class="post-title-link" href="/2023/11/04/testing-and-analysis-of-jvm-memory-area/" itemprop="url">
-          <span itemprop="name">JVM 内存区域的测试和分析</span>
-        </a>
-      </div>
-
-      
-    </header>
-  </article>
-
 
     </div>
   </div>
@@ -425,13 +425,13 @@ <h1 class="site-title">Moralok</h1>
     <span class="post-meta-item-icon">
       <i class="fa fa-chart-line"></i>
     </span>
-    <span title="站点总字数">125k</span>
+    <span title="站点总字数">129k</span>
   </span>
   <span class="post-meta-item">
     <span class="post-meta-item-icon">
       <i class="fa fa-coffee"></i>
     </span>
-    <span title="站点阅读时长">6:56</span>
+    <span title="站点阅读时长">7:09</span>
   </span>
 </div>
   <div class="powered-by">由 <a href="https://hexo.io/" rel="noopener" target="_blank">Hexo</a> & <a href="https://theme-next.js.org/" rel="noopener" target="_blank">NexT.Gemini</a> 强力驱动
diff --git a/archives/page/4/index.html b/archives/page/4/index.html
index a2385745..c5681aa0 100644
--- a/archives/page/4/index.html
+++ b/archives/page/4/index.html
@@ -151,7 +151,7 @@ <h1 class="site-title">Moralok</h1>
   <nav class="site-state">
       <div class="site-state-item site-state-posts">
         <a href="/archives/">
-          <span class="site-state-item-count">48</span>
+          <span class="site-state-item-count">49</span>
           <span class="site-state-item-name">日志</span>
         </a>
       </div>
@@ -188,7 +188,7 @@ <h1 class="site-title">Moralok</h1>
     <div class="post-content">
       <div class="collection-title">
         
-        <span class="collection-header">还行! 目前共计 48 篇日志。 继续努力。</span>
+        <span class="collection-header">还行! 目前共计 49 篇日志。 继续努力。</span>
       </div>
 
       
@@ -196,6 +196,26 @@ <h1 class="site-title">Moralok</h1>
       <span class="collection-header">2023</span>
     </div>
 
+  <article itemscope itemtype="http://schema.org/Article">
+    <header class="post-header">
+      <div class="post-meta-container">
+        <time itemprop="dateCreated"
+              datetime="2023-11-04T19:21:25+08:00"
+              content="2023-11-04">
+          11-04
+        </time>
+      </div>
+
+      <div class="post-title">
+        <a class="post-title-link" href="/2023/11/04/testing-and-analysis-of-jvm-memory-area/" itemprop="url">
+          <span itemprop="name">JVM 内存区域的测试和分析</span>
+        </a>
+      </div>
+
+      
+    </header>
+  </article>
+
   <article itemscope itemtype="http://schema.org/Article">
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@@ -376,26 +396,6 @@ <h1 class="site-title">Moralok</h1>
     </header>
   </article>
 
-  <article itemscope itemtype="http://schema.org/Article">
-    <header class="post-header">
-      <div class="post-meta-container">
-        <time itemprop="dateCreated"
-              datetime="2023-06-13T22:56:11+08:00"
-              content="2023-06-13">
-          06-13
-        </time>
-      </div>
-
-      <div class="post-title">
-        <a class="post-title-link" href="/2023/06/13/how-to-configure-proxy-for-terminal-docker-and-container/" itemprop="url">
-          <span itemprop="name">如何为终端、docker 和容器设置代理</span>
-        </a>
-      </div>
-
-      
-    </header>
-  </article>
-
 
     </div>
   </div>
@@ -425,13 +425,13 @@ <h1 class="site-title">Moralok</h1>
     <span class="post-meta-item-icon">
       <i class="fa fa-chart-line"></i>
     </span>
-    <span title="站点总字数">125k</span>
+    <span title="站点总字数">129k</span>
   </span>
   <span class="post-meta-item">
     <span class="post-meta-item-icon">
       <i class="fa fa-coffee"></i>
     </span>
-    <span title="站点阅读时长">6:56</span>
+    <span title="站点阅读时长">7:09</span>
   </span>
 </div>
   <div class="powered-by">由 <a href="https://hexo.io/" rel="noopener" target="_blank">Hexo</a> & <a href="https://theme-next.js.org/" rel="noopener" target="_blank">NexT.Gemini</a> 强力驱动
diff --git a/archives/page/5/index.html b/archives/page/5/index.html
index 3457980e..006dcc21 100644
--- a/archives/page/5/index.html
+++ b/archives/page/5/index.html
@@ -151,7 +151,7 @@ <h1 class="site-title">Moralok</h1>
   <nav class="site-state">
       <div class="site-state-item site-state-posts">
         <a href="/archives/">
-          <span class="site-state-item-count">48</span>
+          <span class="site-state-item-count">49</span>
           <span class="site-state-item-name">日志</span>
         </a>
       </div>
@@ -188,7 +188,7 @@ <h1 class="site-title">Moralok</h1>
     <div class="post-content">
       <div class="collection-title">
         
-        <span class="collection-header">还行! 目前共计 48 篇日志。 继续努力。</span>
+        <span class="collection-header">还行! 目前共计 49 篇日志。 继续努力。</span>
       </div>
 
       
@@ -196,6 +196,26 @@ <h1 class="site-title">Moralok</h1>
       <span class="collection-header">2023</span>
     </div>
 
+  <article itemscope itemtype="http://schema.org/Article">
+    <header class="post-header">
+      <div class="post-meta-container">
+        <time itemprop="dateCreated"
+              datetime="2023-06-13T22:56:11+08:00"
+              content="2023-06-13">
+          06-13
+        </time>
+      </div>
+
+      <div class="post-title">
+        <a class="post-title-link" href="/2023/06/13/how-to-configure-proxy-for-terminal-docker-and-container/" itemprop="url">
+          <span itemprop="name">如何为终端、docker 和容器设置代理</span>
+        </a>
+      </div>
+
+      
+    </header>
+  </article>
+
   <article itemscope itemtype="http://schema.org/Article">
     <header class="post-header">
       <div class="post-meta-container">
@@ -388,13 +408,13 @@ <h1 class="site-title">Moralok</h1>
     <span class="post-meta-item-icon">
       <i class="fa fa-chart-line"></i>
     </span>
-    <span title="站点总字数">125k</span>
+    <span title="站点总字数">129k</span>
   </span>
   <span class="post-meta-item">
     <span class="post-meta-item-icon">
       <i class="fa fa-coffee"></i>
     </span>
-    <span title="站点阅读时长">6:56</span>
+    <span title="站点阅读时长">7:09</span>
   </span>
 </div>
   <div class="powered-by">由 <a href="https://hexo.io/" rel="noopener" target="_blank">Hexo</a> & <a href="https://theme-next.js.org/" rel="noopener" target="_blank">NexT.Gemini</a> 强力驱动
diff --git a/index.html b/index.html
index b97bd036..a374f805 100644
--- a/index.html
+++ b/index.html
@@ -53,7 +53,119 @@
   <noscript>
     <link rel="stylesheet" href="/css/noscript.css">
   </noscript>
-</head>
+<style>mjx-container[jax="SVG"] {
+  direction: ltr;
+}
+
+mjx-container[jax="SVG"] > svg {
+  overflow: visible;
+}
+
+mjx-container[jax="SVG"][display="true"] {
+  display: block;
+  text-align: center;
+  margin: 1em 0;
+}
+
+mjx-container[jax="SVG"][justify="left"] {
+  text-align: left;
+}
+
+mjx-container[jax="SVG"][justify="right"] {
+  text-align: right;
+}
+
+g[data-mml-node="merror"] > g {
+  fill: red;
+  stroke: red;
+}
+
+g[data-mml-node="merror"] > rect[data-background] {
+  fill: yellow;
+  stroke: none;
+}
+
+g[data-mml-node="mtable"] > line[data-line] {
+  stroke-width: 70px;
+  fill: none;
+}
+
+g[data-mml-node="mtable"] > rect[data-frame] {
+  stroke-width: 70px;
+  fill: none;
+}
+
+g[data-mml-node="mtable"] > .mjx-dashed {
+  stroke-dasharray: 140;
+}
+
+g[data-mml-node="mtable"] > .mjx-dotted {
+  stroke-linecap: round;
+  stroke-dasharray: 0,140;
+}
+
+g[data-mml-node="mtable"] > svg {
+  overflow: visible;
+}
+
+[jax="SVG"] mjx-tool {
+  display: inline-block;
+  position: relative;
+  width: 0;
+  height: 0;
+}
+
+[jax="SVG"] mjx-tool > mjx-tip {
+  position: absolute;
+  top: 0;
+  left: 0;
+}
+
+mjx-tool > mjx-tip {
+  display: inline-block;
+  padding: .2em;
+  border: 1px solid #888;
+  font-size: 70%;
+  background-color: #F8F8F8;
+  color: black;
+  box-shadow: 2px 2px 5px #AAAAAA;
+}
+
+g[data-mml-node="maction"][data-toggle] {
+  cursor: pointer;
+}
+
+mjx-status {
+  display: block;
+  position: fixed;
+  left: 1em;
+  bottom: 1em;
+  min-width: 25%;
+  padding: .2em .4em;
+  border: 1px solid #888;
+  font-size: 90%;
+  background-color: #F8F8F8;
+  color: black;
+}
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+foreignObject[data-mjx-xml] {
+  font-family: initial;
+  line-height: normal;
+  overflow: visible;
+}
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+}
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+mjx-container[display="true"] {
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+}
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+mjx-container[display="true"] + br {
+  display: none;
+}
+</style></head>
 
 <body itemscope itemtype="http://schema.org/WebPage" class="use-motion">
   <div class="headband"></div>
@@ -151,7 +263,7 @@ <h1 class="site-title">Moralok</h1>
   <nav class="site-state">
       <div class="site-state-item site-state-posts">
         <a href="/archives/">
-          <span class="site-state-item-count">48</span>
+          <span class="site-state-item-count">49</span>
           <span class="site-state-item-name">日志</span>
         </a>
       </div>
@@ -188,7 +300,7 @@ <h1 class="site-title">Moralok</h1>
   
 
   <article itemscope itemtype="http://schema.org/Article" class="post-content" lang="">
-    <link itemprop="mainEntityOfPage" href="https://www.moralok.com/2024/01/30/installation-and-use-of-k3s/">
+    <link itemprop="mainEntityOfPage" href="https://www.moralok.com/2024/03/11/representating-and-manipulating-information/">
 
     <span hidden itemprop="author" itemscope itemtype="http://schema.org/Person">
       <meta itemprop="image" content="/images/avatar.gif">
@@ -206,7 +318,7 @@ <h1 class="site-title">Moralok</h1>
     </span>
       <header class="post-header">
         <h2 class="post-title" itemprop="name headline">
-          <a href="/2024/01/30/installation-and-use-of-k3s/" class="post-title-link" itemprop="url">k3s 的安装和使用</a>
+          <a href="/2024/03/11/representating-and-manipulating-information/" class="post-title-link" itemprop="url">信息的表示和处理</a>
         </h2>
 
         <div class="post-meta-container">
@@ -217,18 +329,18 @@ <h2 class="post-title" itemprop="name headline">
       </span>
       <span class="post-meta-item-text">发表于</span>
 
-      <time title="创建时间：2024-01-30 19:45:23" itemprop="dateCreated datePublished" datetime="2024-01-30T19:45:23+08:00">2024-01-30</time>
+      <time title="创建时间：2024-03-12 07:48:32" itemprop="dateCreated datePublished" datetime="2024-03-12T07:48:32+08:00">2024-03-12</time>
     </span>
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       <span class="post-meta-item-icon">
         <i class="far fa-calendar-check"></i>
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       <span class="post-meta-item-text">更新于</span>
-      <time title="修改时间：2024-04-10 22:49:47" itemprop="dateModified" datetime="2024-04-10T22:49:47+08:00">2024-04-10</time>
+      <time title="修改时间：2024-04-24 02:42:37" itemprop="dateModified" datetime="2024-04-24T02:42:37+08:00">2024-04-24</time>
     </span>
 
   
-    <span id="/2024/01/30/installation-and-use-of-k3s/" class="post-meta-item leancloud_visitors" data-flag-title="k3s 的安装和使用" title="阅读次数">
+    <span id="/2024/03/11/representating-and-manipulating-information/" class="post-meta-item leancloud_visitors" data-flag-title="信息的表示和处理" title="阅读次数">
       <span class="post-meta-item-icon">
         <i class="far fa-eye"></i>
       </span>
@@ -241,14 +353,14 @@ <h2 class="post-title" itemprop="name headline">
         <i class="far fa-file-word"></i>
       </span>
       <span class="post-meta-item-text">本文字数：</span>
-      <span>1.5k</span>
+      <span>4.1k</span>
     </span>
     <span class="post-meta-item" title="阅读时长">
       <span class="post-meta-item-icon">
         <i class="far fa-clock"></i>
       </span>
       <span class="post-meta-item-text">阅读时长 &asymp;</span>
-      <span>5 分钟</span>
+      <span>14 分钟</span>
     </span>
 </div>
 
@@ -259,10 +371,10 @@ <h2 class="post-title" itemprop="name headline">
     
     
     <div class="post-body" itemprop="articleBody">
-          <p>本文记录了 <code>k3s</code> 的安装和使用，相较于 <code>minikube</code>，前者是一个完全兼容的 <code>Kubernetes</code> 发行版，安装和使用的体验更佳。</p>
+          <p>(0 &amp; 1) + interpretation = everything.</p>
           <!--noindex-->
             <div class="post-button">
-              <a class="btn" href="/2024/01/30/installation-and-use-of-k3s/#more" rel="contents">
+              <a class="btn" href="/2024/03/11/representating-and-manipulating-information/#more" rel="contents">
                 阅读全文 &raquo;
               </a>
             </div>
@@ -293,7 +405,7 @@ <h2 class="post-title" itemprop="name headline">
   
 
   <article itemscope itemtype="http://schema.org/Article" class="post-content" lang="">
-    <link itemprop="mainEntityOfPage" href="https://www.moralok.com/2024/01/18/use-vim/">
+    <link itemprop="mainEntityOfPage" href="https://www.moralok.com/2024/01/30/installation-and-use-of-k3s/">
 
     <span hidden itemprop="author" itemscope itemtype="http://schema.org/Person">
       <meta itemprop="image" content="/images/avatar.gif">
@@ -311,7 +423,7 @@ <h2 class="post-title" itemprop="name headline">
     </span>
       <header class="post-header">
         <h2 class="post-title" itemprop="name headline">
-          <a href="/2024/01/18/use-vim/" class="post-title-link" itemprop="url">使用 Vim</a>
+          <a href="/2024/01/30/installation-and-use-of-k3s/" class="post-title-link" itemprop="url">k3s 的安装和使用</a>
         </h2>
 
         <div class="post-meta-container">
@@ -322,18 +434,18 @@ <h2 class="post-title" itemprop="name headline">
       </span>
       <span class="post-meta-item-text">发表于</span>
 
-      <time title="创建时间：2024-01-18 08:34:08" itemprop="dateCreated datePublished" datetime="2024-01-18T08:34:08+08:00">2024-01-18</time>
+      <time title="创建时间：2024-01-30 19:45:23" itemprop="dateCreated datePublished" datetime="2024-01-30T19:45:23+08:00">2024-01-30</time>
     </span>
     <span class="post-meta-item">
       <span class="post-meta-item-icon">
         <i class="far fa-calendar-check"></i>
       </span>
       <span class="post-meta-item-text">更新于</span>
-      <time title="修改时间：2024-04-10 22:49:47" itemprop="dateModified" datetime="2024-04-10T22:49:47+08:00">2024-04-10</time>
+      <time title="修改时间：2024-04-24 02:42:37" itemprop="dateModified" datetime="2024-04-24T02:42:37+08:00">2024-04-24</time>
     </span>
 
   
-    <span id="/2024/01/18/use-vim/" class="post-meta-item leancloud_visitors" data-flag-title="使用 Vim" title="阅读次数">
+    <span id="/2024/01/30/installation-and-use-of-k3s/" class="post-meta-item leancloud_visitors" data-flag-title="k3s 的安装和使用" title="阅读次数">
       <span class="post-meta-item-icon">
         <i class="far fa-eye"></i>
       </span>
@@ -346,7 +458,7 @@ <h2 class="post-title" itemprop="name headline">
         <i class="far fa-file-word"></i>
       </span>
       <span class="post-meta-item-text">本文字数：</span>
-      <span>1.4k</span>
+      <span>1.5k</span>
     </span>
     <span class="post-meta-item" title="阅读时长">
       <span class="post-meta-item-icon">
@@ -364,10 +476,10 @@ <h2 class="post-title" itemprop="name headline">
     
     
     <div class="post-body" itemprop="articleBody">
-          <p>本文记录了 <code>Vim</code> 常用的快捷键作为备忘清单。</p>
+          <p>本文记录了 <code>k3s</code> 的安装和使用，相较于 <code>minikube</code>，前者是一个完全兼容的 <code>Kubernetes</code> 发行版，安装和使用的体验更佳。</p>
           <!--noindex-->
             <div class="post-button">
-              <a class="btn" href="/2024/01/18/use-vim/#more" rel="contents">
+              <a class="btn" href="/2024/01/30/installation-and-use-of-k3s/#more" rel="contents">
                 阅读全文 &raquo;
               </a>
             </div>
@@ -398,7 +510,7 @@ <h2 class="post-title" itemprop="name headline">
   
 
   <article itemscope itemtype="http://schema.org/Article" class="post-content" lang="">
-    <link itemprop="mainEntityOfPage" href="https://www.moralok.com/2024/01/14/increase-disk-space-of-Ubuntu-server-on-VMware-without-using-GParted/">
+    <link itemprop="mainEntityOfPage" href="https://www.moralok.com/2024/01/18/use-vim/">
 
     <span hidden itemprop="author" itemscope itemtype="http://schema.org/Person">
       <meta itemprop="image" content="/images/avatar.gif">
@@ -416,7 +528,7 @@ <h2 class="post-title" itemprop="name headline">
     </span>
       <header class="post-header">
         <h2 class="post-title" itemprop="name headline">
-          <a href="/2024/01/14/increase-disk-space-of-Ubuntu-server-on-VMware-without-using-GParted/" class="post-title-link" itemprop="url">不使用 GParted 的情况下为 VMware 中的 Ubuntu Server 增大磁盘空间</a>
+          <a href="/2024/01/18/use-vim/" class="post-title-link" itemprop="url">使用 Vim</a>
         </h2>
 
         <div class="post-meta-container">
@@ -427,18 +539,18 @@ <h2 class="post-title" itemprop="name headline">
       </span>
       <span class="post-meta-item-text">发表于</span>
 
-      <time title="创建时间：2024-01-14 15:49:47" itemprop="dateCreated datePublished" datetime="2024-01-14T15:49:47+08:00">2024-01-14</time>
+      <time title="创建时间：2024-01-18 08:34:08" itemprop="dateCreated datePublished" datetime="2024-01-18T08:34:08+08:00">2024-01-18</time>
     </span>
     <span class="post-meta-item">
       <span class="post-meta-item-icon">
         <i class="far fa-calendar-check"></i>
       </span>
       <span class="post-meta-item-text">更新于</span>
-      <time title="修改时间：2024-04-10 22:49:47" itemprop="dateModified" datetime="2024-04-10T22:49:47+08:00">2024-04-10</time>
+      <time title="修改时间：2024-04-24 02:42:37" itemprop="dateModified" datetime="2024-04-24T02:42:37+08:00">2024-04-24</time>
     </span>
 
   
-    <span id="/2024/01/14/increase-disk-space-of-Ubuntu-server-on-VMware-without-using-GParted/" class="post-meta-item leancloud_visitors" data-flag-title="不使用 GParted 的情况下为 VMware 中的 Ubuntu Server 增大磁盘空间" title="阅读次数">
+    <span id="/2024/01/18/use-vim/" class="post-meta-item leancloud_visitors" data-flag-title="使用 Vim" title="阅读次数">
       <span class="post-meta-item-icon">
         <i class="far fa-eye"></i>
       </span>
@@ -451,7 +563,7 @@ <h2 class="post-title" itemprop="name headline">
         <i class="far fa-file-word"></i>
       </span>
       <span class="post-meta-item-text">本文字数：</span>
-      <span>1.6k</span>
+      <span>1.4k</span>
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     <span class="post-meta-item" title="阅读时长">
       <span class="post-meta-item-icon">
@@ -469,10 +581,10 @@ <h2 class="post-title" itemprop="name headline">
     
     
     <div class="post-body" itemprop="articleBody">
-          <p><code>GParted</code> 是一款适用于 <code>Linux</code> 的图形化磁盘分区管理工具，通过它可以便捷地为 <code>VMware</code> 中的 <code>Ubuntu Desktop</code> 增大磁盘空间。然而你可能正在使用 <code>Ubuntu Server</code>，并不想要安装或并不被允许安装图形化界面，本文介绍了如何在不使用 <code>GParted</code> 的情况下，通过命令行使用自带的工具为 <code>VMware</code> 中的 <code>Ubuntu Server</code> 增大磁盘空间。</p>
+          <p>本文记录了 <code>Vim</code> 常用的快捷键作为备忘清单。</p>
           <!--noindex-->
             <div class="post-button">
-              <a class="btn" href="/2024/01/14/increase-disk-space-of-Ubuntu-server-on-VMware-without-using-GParted/#more" rel="contents">
+              <a class="btn" href="/2024/01/18/use-vim/#more" rel="contents">
                 阅读全文 &raquo;
               </a>
             </div>
@@ -503,7 +615,7 @@ <h2 class="post-title" itemprop="name headline">
   
 
   <article itemscope itemtype="http://schema.org/Article" class="post-content" lang="">
-    <link itemprop="mainEntityOfPage" href="https://www.moralok.com/2024/01/06/talk-about-isolation-of-MySQL-transactions/">
+    <link itemprop="mainEntityOfPage" href="https://www.moralok.com/2024/01/14/increase-disk-space-of-Ubuntu-server-on-VMware-without-using-GParted/">
 
     <span hidden itemprop="author" itemscope itemtype="http://schema.org/Person">
       <meta itemprop="image" content="/images/avatar.gif">
@@ -521,7 +633,7 @@ <h2 class="post-title" itemprop="name headline">
     </span>
       <header class="post-header">
         <h2 class="post-title" itemprop="name headline">
-          <a href="/2024/01/06/talk-about-isolation-of-MySQL-transactions/" class="post-title-link" itemprop="url">谈谈 MySQL 事务的隔离性</a>
+          <a href="/2024/01/14/increase-disk-space-of-Ubuntu-server-on-VMware-without-using-GParted/" class="post-title-link" itemprop="url">不使用 GParted 的情况下为 VMware 中的 Ubuntu Server 增大磁盘空间</a>
         </h2>
 
         <div class="post-meta-container">
@@ -532,18 +644,18 @@ <h2 class="post-title" itemprop="name headline">
       </span>
       <span class="post-meta-item-text">发表于</span>
 
-      <time title="创建时间：2024-01-06 13:51:12" itemprop="dateCreated datePublished" datetime="2024-01-06T13:51:12+08:00">2024-01-06</time>
+      <time title="创建时间：2024-01-14 15:49:47" itemprop="dateCreated datePublished" datetime="2024-01-14T15:49:47+08:00">2024-01-14</time>
     </span>
     <span class="post-meta-item">
       <span class="post-meta-item-icon">
         <i class="far fa-calendar-check"></i>
       </span>
       <span class="post-meta-item-text">更新于</span>
-      <time title="修改时间：2024-04-10 22:49:47" itemprop="dateModified" datetime="2024-04-10T22:49:47+08:00">2024-04-10</time>
+      <time title="修改时间：2024-04-24 02:42:37" itemprop="dateModified" datetime="2024-04-24T02:42:37+08:00">2024-04-24</time>
     </span>
 
   
-    <span id="/2024/01/06/talk-about-isolation-of-MySQL-transactions/" class="post-meta-item leancloud_visitors" data-flag-title="谈谈 MySQL 事务的隔离性" title="阅读次数">
+    <span id="/2024/01/14/increase-disk-space-of-Ubuntu-server-on-VMware-without-using-GParted/" class="post-meta-item leancloud_visitors" data-flag-title="不使用 GParted 的情况下为 VMware 中的 Ubuntu Server 增大磁盘空间" title="阅读次数">
       <span class="post-meta-item-icon">
         <i class="far fa-eye"></i>
       </span>
@@ -556,14 +668,14 @@ <h2 class="post-title" itemprop="name headline">
         <i class="far fa-file-word"></i>
       </span>
       <span class="post-meta-item-text">本文字数：</span>
-      <span>4.4k</span>
+      <span>1.6k</span>
     </span>
     <span class="post-meta-item" title="阅读时长">
       <span class="post-meta-item-icon">
         <i class="far fa-clock"></i>
       </span>
       <span class="post-meta-item-text">阅读时长 &asymp;</span>
-      <span>15 分钟</span>
+      <span>5 分钟</span>
     </span>
 </div>
 
@@ -574,10 +686,10 @@ <h2 class="post-title" itemprop="name headline">
     
     
     <div class="post-body" itemprop="articleBody">
-          <p>事务就是一组数据库操作，它具有原子性（<code>Atomicity</code>）、一致性（<code>Consistency</code>）、隔离性（<code>Isolation</code>）和持久性（<code>Durability</code>），简称为 <code>ACID</code>。本文将介绍 <code>MySQL</code> 事务的<strong>隔离性</strong>以及对其的思考。<br>尽管这是一个老生常谈的话题，网上也有很多相关的资料，但是要理解它并不容易。即使林晓斌老师在 <strong>《MySQL 实战 45 讲》</strong> 中用了两个章节进行介绍，但是你在评论区中会发现有些分享或讨论的观点彼此矛盾。原因可能有很多，比如为了易于理解使用简化概念进行分析，有些具体细节各人各执一词同时它们又不好通过测试进行验证，用词不严谨等等。本文尽可能为自己梳理出一个完善并且前后一致的认知体系，再针对一些容易引起误解的地方作进一步的说明。</p>
+          <p><code>GParted</code> 是一款适用于 <code>Linux</code> 的图形化磁盘分区管理工具，通过它可以便捷地为 <code>VMware</code> 中的 <code>Ubuntu Desktop</code> 增大磁盘空间。然而你可能正在使用 <code>Ubuntu Server</code>，并不想要安装或并不被允许安装图形化界面，本文介绍了如何在不使用 <code>GParted</code> 的情况下，通过命令行使用自带的工具为 <code>VMware</code> 中的 <code>Ubuntu Server</code> 增大磁盘空间。</p>
           <!--noindex-->
             <div class="post-button">
-              <a class="btn" href="/2024/01/06/talk-about-isolation-of-MySQL-transactions/#more" rel="contents">
+              <a class="btn" href="/2024/01/14/increase-disk-space-of-Ubuntu-server-on-VMware-without-using-GParted/#more" rel="contents">
                 阅读全文 &raquo;
               </a>
             </div>
@@ -608,7 +720,7 @@ <h2 class="post-title" itemprop="name headline">
   
 
   <article itemscope itemtype="http://schema.org/Article" class="post-content" lang="">
-    <link itemprop="mainEntityOfPage" href="https://www.moralok.com/2023/12/28/explore-the-Java-classes-Cleaner-and-Finalizer/">
+    <link itemprop="mainEntityOfPage" href="https://www.moralok.com/2024/01/06/talk-about-isolation-of-MySQL-transactions/">
 
     <span hidden itemprop="author" itemscope itemtype="http://schema.org/Person">
       <meta itemprop="image" content="/images/avatar.gif">
@@ -626,7 +738,7 @@ <h2 class="post-title" itemprop="name headline">
     </span>
       <header class="post-header">
         <h2 class="post-title" itemprop="name headline">
-          <a href="/2023/12/28/explore-the-Java-classes-Cleaner-and-Finalizer/" class="post-title-link" itemprop="url">探索 Java 类 Cleaner 和 Finalizer</a>
+          <a href="/2024/01/06/talk-about-isolation-of-MySQL-transactions/" class="post-title-link" itemprop="url">谈谈 MySQL 事务的隔离性</a>
         </h2>
 
         <div class="post-meta-container">
@@ -637,18 +749,18 @@ <h2 class="post-title" itemprop="name headline">
       </span>
       <span class="post-meta-item-text">发表于</span>
 
-      <time title="创建时间：2023-12-28 12:59:48" itemprop="dateCreated datePublished" datetime="2023-12-28T12:59:48+08:00">2023-12-28</time>
+      <time title="创建时间：2024-01-06 13:51:12" itemprop="dateCreated datePublished" datetime="2024-01-06T13:51:12+08:00">2024-01-06</time>
     </span>
     <span class="post-meta-item">
       <span class="post-meta-item-icon">
         <i class="far fa-calendar-check"></i>
       </span>
       <span class="post-meta-item-text">更新于</span>
-      <time title="修改时间：2024-04-10 22:49:47" itemprop="dateModified" datetime="2024-04-10T22:49:47+08:00">2024-04-10</time>
+      <time title="修改时间：2024-04-24 02:42:37" itemprop="dateModified" datetime="2024-04-24T02:42:37+08:00">2024-04-24</time>
     </span>
 
   
-    <span id="/2023/12/28/explore-the-Java-classes-Cleaner-and-Finalizer/" class="post-meta-item leancloud_visitors" data-flag-title="探索 Java 类 Cleaner 和 Finalizer" title="阅读次数">
+    <span id="/2024/01/06/talk-about-isolation-of-MySQL-transactions/" class="post-meta-item leancloud_visitors" data-flag-title="谈谈 MySQL 事务的隔离性" title="阅读次数">
       <span class="post-meta-item-icon">
         <i class="far fa-eye"></i>
       </span>
@@ -661,14 +773,14 @@ <h2 class="post-title" itemprop="name headline">
         <i class="far fa-file-word"></i>
       </span>
       <span class="post-meta-item-text">本文字数：</span>
-      <span>3.1k</span>
+      <span>4.4k</span>
     </span>
     <span class="post-meta-item" title="阅读时长">
       <span class="post-meta-item-icon">
         <i class="far fa-clock"></i>
       </span>
       <span class="post-meta-item-text">阅读时长 &asymp;</span>
-      <span>10 分钟</span>
+      <span>15 分钟</span>
     </span>
 </div>
 
@@ -679,10 +791,10 @@ <h2 class="post-title" itemprop="name headline">
     
     
     <div class="post-body" itemprop="articleBody">
-          <p><code>Java</code> 类 <code>Cleaner</code> 和 <code>Finalizer</code> 都实现了一种 <code>finalization</code> 机制，前者更轻量和强大，你可能在了解 <code>NIO</code> 的堆外内存自动释放机制中注意过它；后者为人所诟病，<code>finalize</code> 方法被人强烈反对使用。本文想要解析它们的原因不在于它们实现的功能，而在于它们是 <code>Reference</code> 的具体子类。<br><code>Reference</code> 作为和 <code>GC</code> 紧密联系的类，你可能从很多文字描述中了解过 <code>SoftReference</code>、<code>WeakReference</code> 还有 <code>PhantomReference</code> 但是却很少从代码层面了解过它们，当你牢记“一个对象是否可以被回收的判断依据是它是否从 <code>Root</code> 对象可达”这条规则再面对 <code>Reference</code> 的子类时是否产生过割裂感；你是否好奇过 <code>Finalizer</code> 如何和重写 <code>finalize</code> 方法的类产生联系，本文将从 <code>Cleaner</code> 和 <code>Finalizer</code> 的源码揭示一些你可能已知的结论背后的朴素原理。</p>
+          <p>事务就是一组数据库操作，它具有原子性（<code>Atomicity</code>）、一致性（<code>Consistency</code>）、隔离性（<code>Isolation</code>）和持久性（<code>Durability</code>），简称为 <code>ACID</code>。本文将介绍 <code>MySQL</code> 事务的<strong>隔离性</strong>以及对其的思考。<br>尽管这是一个老生常谈的话题，网上也有很多相关的资料，但是要理解它并不容易。即使林晓斌老师在 <strong>《MySQL 实战 45 讲》</strong> 中用了两个章节进行介绍，但是你在评论区中会发现有些分享或讨论的观点彼此矛盾。原因可能有很多，比如为了易于理解使用简化概念进行分析，有些具体细节各人各执一词同时它们又不好通过测试进行验证，用词不严谨等等。本文尽可能为自己梳理出一个完善并且前后一致的认知体系，再针对一些容易引起误解的地方作进一步的说明。</p>
           <!--noindex-->
             <div class="post-button">
-              <a class="btn" href="/2023/12/28/explore-the-Java-classes-Cleaner-and-Finalizer/#more" rel="contents">
+              <a class="btn" href="/2024/01/06/talk-about-isolation-of-MySQL-transactions/#more" rel="contents">
                 阅读全文 &raquo;
               </a>
             </div>
@@ -713,7 +825,7 @@ <h2 class="post-title" itemprop="name headline">
   
 
   <article itemscope itemtype="http://schema.org/Article" class="post-content" lang="">
-    <link itemprop="mainEntityOfPage" href="https://www.moralok.com/2023/12/27/source-code-analysis-of-Java-class-Reference/">
+    <link itemprop="mainEntityOfPage" href="https://www.moralok.com/2023/12/28/explore-the-Java-classes-Cleaner-and-Finalizer/">
 
     <span hidden itemprop="author" itemscope itemtype="http://schema.org/Person">
       <meta itemprop="image" content="/images/avatar.gif">
@@ -731,7 +843,7 @@ <h2 class="post-title" itemprop="name headline">
     </span>
       <header class="post-header">
         <h2 class="post-title" itemprop="name headline">
-          <a href="/2023/12/27/source-code-analysis-of-Java-class-Reference/" class="post-title-link" itemprop="url">Java 类 Reference 的源码分析</a>
+          <a href="/2023/12/28/explore-the-Java-classes-Cleaner-and-Finalizer/" class="post-title-link" itemprop="url">探索 Java 类 Cleaner 和 Finalizer</a>
         </h2>
 
         <div class="post-meta-container">
@@ -742,18 +854,18 @@ <h2 class="post-title" itemprop="name headline">
       </span>
       <span class="post-meta-item-text">发表于</span>
 
-      <time title="创建时间：2023-12-27 09:43:28" itemprop="dateCreated datePublished" datetime="2023-12-27T09:43:28+08:00">2023-12-27</time>
+      <time title="创建时间：2023-12-28 12:59:48" itemprop="dateCreated datePublished" datetime="2023-12-28T12:59:48+08:00">2023-12-28</time>
     </span>
     <span class="post-meta-item">
       <span class="post-meta-item-icon">
         <i class="far fa-calendar-check"></i>
       </span>
       <span class="post-meta-item-text">更新于</span>
-      <time title="修改时间：2024-04-10 22:49:47" itemprop="dateModified" datetime="2024-04-10T22:49:47+08:00">2024-04-10</time>
+      <time title="修改时间：2024-04-24 02:42:37" itemprop="dateModified" datetime="2024-04-24T02:42:37+08:00">2024-04-24</time>
     </span>
 
   
-    <span id="/2023/12/27/source-code-analysis-of-Java-class-Reference/" class="post-meta-item leancloud_visitors" data-flag-title="Java 类 Reference 的源码分析" title="阅读次数">
+    <span id="/2023/12/28/explore-the-Java-classes-Cleaner-and-Finalizer/" class="post-meta-item leancloud_visitors" data-flag-title="探索 Java 类 Cleaner 和 Finalizer" title="阅读次数">
       <span class="post-meta-item-icon">
         <i class="far fa-eye"></i>
       </span>
@@ -766,7 +878,7 @@ <h2 class="post-title" itemprop="name headline">
         <i class="far fa-file-word"></i>
       </span>
       <span class="post-meta-item-text">本文字数：</span>
-      <span>2.9k</span>
+      <span>3.1k</span>
     </span>
     <span class="post-meta-item" title="阅读时长">
       <span class="post-meta-item-icon">
@@ -784,10 +896,10 @@ <h2 class="post-title" itemprop="name headline">
     
     
     <div class="post-body" itemprop="articleBody">
-          <p>我们知道 <code>Java</code> 扩充了“引用”的概念，引入了软引用、弱引用和虚引用，它们都属于 <code>Reference</code> 类型，也都可以配合 <code>ReferenceQueue</code> 使用。你是否好奇常常被一笔带过的“<code>引用对象</code>的处理过程”？你是否在探究 <code>NIO</code> 堆外内存的自动释放时看到了 <code>Cleaner</code> 的关键代码但不太能梳理整个过程？你是否好奇在研究 <code>JVM</code> 时偶尔看到的 <code>Reference Handler</code> 线程？本文将分析 <code>Reference</code> 和 <code>ReferenceQueue</code> 的源码带你理解<code>引用对象</code>的工作机制。</p>
+          <p><code>Java</code> 类 <code>Cleaner</code> 和 <code>Finalizer</code> 都实现了一种 <code>finalization</code> 机制，前者更轻量和强大，你可能在了解 <code>NIO</code> 的堆外内存自动释放机制中注意过它；后者为人所诟病，<code>finalize</code> 方法被人强烈反对使用。本文想要解析它们的原因不在于它们实现的功能，而在于它们是 <code>Reference</code> 的具体子类。<br><code>Reference</code> 作为和 <code>GC</code> 紧密联系的类，你可能从很多文字描述中了解过 <code>SoftReference</code>、<code>WeakReference</code> 还有 <code>PhantomReference</code> 但是却很少从代码层面了解过它们，当你牢记“一个对象是否可以被回收的判断依据是它是否从 <code>Root</code> 对象可达”这条规则再面对 <code>Reference</code> 的子类时是否产生过割裂感；你是否好奇过 <code>Finalizer</code> 如何和重写 <code>finalize</code> 方法的类产生联系，本文将从 <code>Cleaner</code> 和 <code>Finalizer</code> 的源码揭示一些你可能已知的结论背后的朴素原理。</p>
           <!--noindex-->
             <div class="post-button">
-              <a class="btn" href="/2023/12/27/source-code-analysis-of-Java-class-Reference/#more" rel="contents">
+              <a class="btn" href="/2023/12/28/explore-the-Java-classes-Cleaner-and-Finalizer/#more" rel="contents">
                 阅读全文 &raquo;
               </a>
             </div>
@@ -818,7 +930,7 @@ <h2 class="post-title" itemprop="name headline">
   
 
   <article itemscope itemtype="http://schema.org/Article" class="post-content" lang="">
-    <link itemprop="mainEntityOfPage" href="https://www.moralok.com/2023/12/25/Unsafe-an-anti-Java-class/">
+    <link itemprop="mainEntityOfPage" href="https://www.moralok.com/2023/12/27/source-code-analysis-of-Java-class-Reference/">
 
     <span hidden itemprop="author" itemscope itemtype="http://schema.org/Person">
       <meta itemprop="image" content="/images/avatar.gif">
@@ -836,7 +948,7 @@ <h2 class="post-title" itemprop="name headline">
     </span>
       <header class="post-header">
         <h2 class="post-title" itemprop="name headline">
-          <a href="/2023/12/25/Unsafe-an-anti-Java-class/" class="post-title-link" itemprop="url">Unsafe，一个“反 Java”的 class</a>
+          <a href="/2023/12/27/source-code-analysis-of-Java-class-Reference/" class="post-title-link" itemprop="url">Java 类 Reference 的源码分析</a>
         </h2>
 
         <div class="post-meta-container">
@@ -847,18 +959,18 @@ <h2 class="post-title" itemprop="name headline">
       </span>
       <span class="post-meta-item-text">发表于</span>
 
-      <time title="创建时间：2023-12-25 08:27:04" itemprop="dateCreated datePublished" datetime="2023-12-25T08:27:04+08:00">2023-12-25</time>
+      <time title="创建时间：2023-12-27 09:43:28" itemprop="dateCreated datePublished" datetime="2023-12-27T09:43:28+08:00">2023-12-27</time>
     </span>
     <span class="post-meta-item">
       <span class="post-meta-item-icon">
         <i class="far fa-calendar-check"></i>
       </span>
       <span class="post-meta-item-text">更新于</span>
-      <time title="修改时间：2024-04-10 22:49:47" itemprop="dateModified" datetime="2024-04-10T22:49:47+08:00">2024-04-10</time>
+      <time title="修改时间：2024-04-24 02:42:37" itemprop="dateModified" datetime="2024-04-24T02:42:37+08:00">2024-04-24</time>
     </span>
 
   
-    <span id="/2023/12/25/Unsafe-an-anti-Java-class/" class="post-meta-item leancloud_visitors" data-flag-title="Unsafe，一个“反 Java”的 class" title="阅读次数">
+    <span id="/2023/12/27/source-code-analysis-of-Java-class-Reference/" class="post-meta-item leancloud_visitors" data-flag-title="Java 类 Reference 的源码分析" title="阅读次数">
       <span class="post-meta-item-icon">
         <i class="far fa-eye"></i>
       </span>
@@ -871,14 +983,14 @@ <h2 class="post-title" itemprop="name headline">
         <i class="far fa-file-word"></i>
       </span>
       <span class="post-meta-item-text">本文字数：</span>
-      <span>2.2k</span>
+      <span>2.9k</span>
     </span>
     <span class="post-meta-item" title="阅读时长">
       <span class="post-meta-item-icon">
         <i class="far fa-clock"></i>
       </span>
       <span class="post-meta-item-text">阅读时长 &asymp;</span>
-      <span>7 分钟</span>
+      <span>10 分钟</span>
     </span>
 </div>
 
@@ -889,10 +1001,10 @@ <h2 class="post-title" itemprop="name headline">
     
     
     <div class="post-body" itemprop="articleBody">
-          <p><code>Unsafe</code> 类位于 <code>sun.misc</code> 包中，它提供了一组用于执行低级别、不安全操作的方法。尽管 <code>Unsafe</code> 类及其所有方法都是公共的，但它的使用受到限制，因为只有受信任的代码才能获取其实例。这个类通常被用于一些底层的、对性能敏感的操作，比如直接内存访问、<code>CAS</code>（<code>Compare and Swap</code>）操作等。本文将介绍这个“反 <code>Java</code>”的类及其方法的典型使用场景。</p>
+          <p>我们知道 <code>Java</code> 扩充了“引用”的概念，引入了软引用、弱引用和虚引用，它们都属于 <code>Reference</code> 类型，也都可以配合 <code>ReferenceQueue</code> 使用。你是否好奇常常被一笔带过的“<code>引用对象</code>的处理过程”？你是否在探究 <code>NIO</code> 堆外内存的自动释放时看到了 <code>Cleaner</code> 的关键代码但不太能梳理整个过程？你是否好奇在研究 <code>JVM</code> 时偶尔看到的 <code>Reference Handler</code> 线程？本文将分析 <code>Reference</code> 和 <code>ReferenceQueue</code> 的源码带你理解<code>引用对象</code>的工作机制。</p>
           <!--noindex-->
             <div class="post-button">
-              <a class="btn" href="/2023/12/25/Unsafe-an-anti-Java-class/#more" rel="contents">
+              <a class="btn" href="/2023/12/27/source-code-analysis-of-Java-class-Reference/#more" rel="contents">
                 阅读全文 &raquo;
               </a>
             </div>
@@ -923,7 +1035,7 @@ <h2 class="post-title" itemprop="name headline">
   
 
   <article itemscope itemtype="http://schema.org/Article" class="post-content" lang="">
-    <link itemprop="mainEntityOfPage" href="https://www.moralok.com/2023/12/19/analysis-and-verification-of-the-synchronized-lock-mechanism/">
+    <link itemprop="mainEntityOfPage" href="https://www.moralok.com/2023/12/25/Unsafe-an-anti-Java-class/">
 
     <span hidden itemprop="author" itemscope itemtype="http://schema.org/Person">
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@@ -941,7 +1053,7 @@ <h2 class="post-title" itemprop="name headline">
     </span>
       <header class="post-header">
         <h2 class="post-title" itemprop="name headline">
-          <a href="/2023/12/19/analysis-and-verification-of-the-synchronized-lock-mechanism/" class="post-title-link" itemprop="url">synchronized 锁机制的分析和验证</a>
+          <a href="/2023/12/25/Unsafe-an-anti-Java-class/" class="post-title-link" itemprop="url">Unsafe，一个“反 Java”的 class</a>
         </h2>
 
         <div class="post-meta-container">
@@ -952,18 +1064,18 @@ <h2 class="post-title" itemprop="name headline">
       </span>
       <span class="post-meta-item-text">发表于</span>
 
-      <time title="创建时间：2023-12-19 12:09:07" itemprop="dateCreated datePublished" datetime="2023-12-19T12:09:07+08:00">2023-12-19</time>
+      <time title="创建时间：2023-12-25 08:27:04" itemprop="dateCreated datePublished" datetime="2023-12-25T08:27:04+08:00">2023-12-25</time>
     </span>
     <span class="post-meta-item">
       <span class="post-meta-item-icon">
         <i class="far fa-calendar-check"></i>
       </span>
       <span class="post-meta-item-text">更新于</span>
-      <time title="修改时间：2024-04-10 22:49:47" itemprop="dateModified" datetime="2024-04-10T22:49:47+08:00">2024-04-10</time>
+      <time title="修改时间：2024-04-24 02:42:37" itemprop="dateModified" datetime="2024-04-24T02:42:37+08:00">2024-04-24</time>
     </span>
 
   
-    <span id="/2023/12/19/analysis-and-verification-of-the-synchronized-lock-mechanism/" class="post-meta-item leancloud_visitors" data-flag-title="synchronized 锁机制的分析和验证" title="阅读次数">
+    <span id="/2023/12/25/Unsafe-an-anti-Java-class/" class="post-meta-item leancloud_visitors" data-flag-title="Unsafe，一个“反 Java”的 class" title="阅读次数">
       <span class="post-meta-item-icon">
         <i class="far fa-eye"></i>
       </span>
@@ -976,14 +1088,14 @@ <h2 class="post-title" itemprop="name headline">
         <i class="far fa-file-word"></i>
       </span>
       <span class="post-meta-item-text">本文字数：</span>
-      <span>7.4k</span>
+      <span>2.2k</span>
     </span>
     <span class="post-meta-item" title="阅读时长">
       <span class="post-meta-item-icon">
         <i class="far fa-clock"></i>
       </span>
       <span class="post-meta-item-text">阅读时长 &asymp;</span>
-      <span>25 分钟</span>
+      <span>7 分钟</span>
     </span>
 </div>
 
@@ -994,10 +1106,10 @@ <h2 class="post-title" itemprop="name headline">
     
     
     <div class="post-body" itemprop="articleBody">
-          <p>本文详细介绍了 <code>Java</code> 中 <code>synchronized</code> 锁的机制、存储结构、优化措施以及升级过程，并通过 <code>jol-core</code> 演示 <code>Mark Word</code> 的变化来验证锁升级的多个 <code>case</code>。</p>
+          <p><code>Unsafe</code> 类位于 <code>sun.misc</code> 包中，它提供了一组用于执行低级别、不安全操作的方法。尽管 <code>Unsafe</code> 类及其所有方法都是公共的，但它的使用受到限制，因为只有受信任的代码才能获取其实例。这个类通常被用于一些底层的、对性能敏感的操作，比如直接内存访问、<code>CAS</code>（<code>Compare and Swap</code>）操作等。本文将介绍这个“反 <code>Java</code>”的类及其方法的典型使用场景。</p>
           <!--noindex-->
             <div class="post-button">
-              <a class="btn" href="/2023/12/19/analysis-and-verification-of-the-synchronized-lock-mechanism/#more" rel="contents">
+              <a class="btn" href="/2023/12/25/Unsafe-an-anti-Java-class/#more" rel="contents">
                 阅读全文 &raquo;
               </a>
             </div>
@@ -1028,7 +1140,7 @@ <h2 class="post-title" itemprop="name headline">
   
 
   <article itemscope itemtype="http://schema.org/Article" class="post-content" lang="">
-    <link itemprop="mainEntityOfPage" href="https://www.moralok.com/2023/12/14/install-ELK-using-Docker-Compose/">
+    <link itemprop="mainEntityOfPage" href="https://www.moralok.com/2023/12/19/analysis-and-verification-of-the-synchronized-lock-mechanism/">
 
     <span hidden itemprop="author" itemscope itemtype="http://schema.org/Person">
       <meta itemprop="image" content="/images/avatar.gif">
@@ -1046,7 +1158,7 @@ <h2 class="post-title" itemprop="name headline">
     </span>
       <header class="post-header">
         <h2 class="post-title" itemprop="name headline">
-          <a href="/2023/12/14/install-ELK-using-Docker-Compose/" class="post-title-link" itemprop="url">使用 Docker Compose 安装 ELK</a>
+          <a href="/2023/12/19/analysis-and-verification-of-the-synchronized-lock-mechanism/" class="post-title-link" itemprop="url">synchronized 锁机制的分析和验证</a>
         </h2>
 
         <div class="post-meta-container">
@@ -1057,18 +1169,18 @@ <h2 class="post-title" itemprop="name headline">
       </span>
       <span class="post-meta-item-text">发表于</span>
 
-      <time title="创建时间：2023-12-14 19:35:00" itemprop="dateCreated datePublished" datetime="2023-12-14T19:35:00+08:00">2023-12-14</time>
+      <time title="创建时间：2023-12-19 12:09:07" itemprop="dateCreated datePublished" datetime="2023-12-19T12:09:07+08:00">2023-12-19</time>
     </span>
     <span class="post-meta-item">
       <span class="post-meta-item-icon">
         <i class="far fa-calendar-check"></i>
       </span>
       <span class="post-meta-item-text">更新于</span>
-      <time title="修改时间：2024-04-10 22:49:47" itemprop="dateModified" datetime="2024-04-10T22:49:47+08:00">2024-04-10</time>
+      <time title="修改时间：2024-04-24 02:42:37" itemprop="dateModified" datetime="2024-04-24T02:42:37+08:00">2024-04-24</time>
     </span>
 
   
-    <span id="/2023/12/14/install-ELK-using-Docker-Compose/" class="post-meta-item leancloud_visitors" data-flag-title="使用 Docker Compose 安装 ELK" title="阅读次数">
+    <span id="/2023/12/19/analysis-and-verification-of-the-synchronized-lock-mechanism/" class="post-meta-item leancloud_visitors" data-flag-title="synchronized 锁机制的分析和验证" title="阅读次数">
       <span class="post-meta-item-icon">
         <i class="far fa-eye"></i>
       </span>
@@ -1081,14 +1193,14 @@ <h2 class="post-title" itemprop="name headline">
         <i class="far fa-file-word"></i>
       </span>
       <span class="post-meta-item-text">本文字数：</span>
-      <span>2.8k</span>
+      <span>7.4k</span>
     </span>
     <span class="post-meta-item" title="阅读时长">
       <span class="post-meta-item-icon">
         <i class="far fa-clock"></i>
       </span>
       <span class="post-meta-item-text">阅读时长 &asymp;</span>
-      <span>9 分钟</span>
+      <span>25 分钟</span>
     </span>
 </div>
 
@@ -1099,10 +1211,10 @@ <h2 class="post-title" itemprop="name headline">
     
     
     <div class="post-body" itemprop="articleBody">
-          <p>印象里每次安装 <code>ElK</code> 组件的体验都不是很好，或多或少都遇到过奇奇怪怪的问题。本文几乎完全按照官方文档：<a target="_blank" rel="noopener" href="https://www.elastic.co/cn/blog/getting-started-with-the-elastic-stack-and-docker-compose">Getting started with the Elastic Stack and Docker Compose: Part 1</a> 通过 <code>docker compose</code> 安装 <code>elasticsearch</code>、<code>kibana</code>、<code>metricbeat</code>、<code>filebeat</code> 和 <code>logstash</code>，但是移除了 <code>ssl</code> 相关的配置。你可以直接按照原文档进行安装，但是对照本文可以帮助你更快速地移除不需要的配置以及绕开可能踩到的坑。<br>此安装方式尽量<strong>使用环境变量代替编写配置文件</strong>，便于在备份和分享时将敏感信息留存在本地。本次安装时间为 <code>2023-12-14</code>，使用官方镜像，版本为 <code>8.11.2</code>。</p>
+          <p>本文详细介绍了 <code>Java</code> 中 <code>synchronized</code> 锁的机制、存储结构、优化措施以及升级过程，并通过 <code>jol-core</code> 演示 <code>Mark Word</code> 的变化来验证锁升级的多个 <code>case</code>。</p>
           <!--noindex-->
             <div class="post-button">
-              <a class="btn" href="/2023/12/14/install-ELK-using-Docker-Compose/#more" rel="contents">
+              <a class="btn" href="/2023/12/19/analysis-and-verification-of-the-synchronized-lock-mechanism/#more" rel="contents">
                 阅读全文 &raquo;
               </a>
             </div>
@@ -1133,7 +1245,7 @@ <h2 class="post-title" itemprop="name headline">
   
 
   <article itemscope itemtype="http://schema.org/Article" class="post-content" lang="">
-    <link itemprop="mainEntityOfPage" href="https://www.moralok.com/2023/12/13/how-to-grant-when-MySQL-started-with-skip-name-resolve-mode/">
+    <link itemprop="mainEntityOfPage" href="https://www.moralok.com/2023/12/14/install-ELK-using-Docker-Compose/">
 
     <span hidden itemprop="author" itemscope itemtype="http://schema.org/Person">
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@@ -1151,7 +1263,7 @@ <h2 class="post-title" itemprop="name headline">
     </span>
       <header class="post-header">
         <h2 class="post-title" itemprop="name headline">
-          <a href="/2023/12/13/how-to-grant-when-MySQL-started-with-skip-name-resolve-mode/" class="post-title-link" itemprop="url">当 MySQL 以 skip-name-resolve 模式启动时如何使用 grant 命令</a>
+          <a href="/2023/12/14/install-ELK-using-Docker-Compose/" class="post-title-link" itemprop="url">使用 Docker Compose 安装 ELK</a>
         </h2>
 
         <div class="post-meta-container">
@@ -1162,18 +1274,18 @@ <h2 class="post-title" itemprop="name headline">
       </span>
       <span class="post-meta-item-text">发表于</span>
 
-      <time title="创建时间：2023-12-13 12:16:17" itemprop="dateCreated datePublished" datetime="2023-12-13T12:16:17+08:00">2023-12-13</time>
+      <time title="创建时间：2023-12-14 19:35:00" itemprop="dateCreated datePublished" datetime="2023-12-14T19:35:00+08:00">2023-12-14</time>
     </span>
     <span class="post-meta-item">
       <span class="post-meta-item-icon">
         <i class="far fa-calendar-check"></i>
       </span>
       <span class="post-meta-item-text">更新于</span>
-      <time title="修改时间：2024-04-10 22:49:47" itemprop="dateModified" datetime="2024-04-10T22:49:47+08:00">2024-04-10</time>
+      <time title="修改时间：2024-04-24 02:42:37" itemprop="dateModified" datetime="2024-04-24T02:42:37+08:00">2024-04-24</time>
     </span>
 
   
-    <span id="/2023/12/13/how-to-grant-when-MySQL-started-with-skip-name-resolve-mode/" class="post-meta-item leancloud_visitors" data-flag-title="当 MySQL 以 skip-name-resolve 模式启动时如何使用 grant 命令" title="阅读次数">
+    <span id="/2023/12/14/install-ELK-using-Docker-Compose/" class="post-meta-item leancloud_visitors" data-flag-title="使用 Docker Compose 安装 ELK" title="阅读次数">
       <span class="post-meta-item-icon">
         <i class="far fa-eye"></i>
       </span>
@@ -1186,14 +1298,14 @@ <h2 class="post-title" itemprop="name headline">
         <i class="far fa-file-word"></i>
       </span>
       <span class="post-meta-item-text">本文字数：</span>
-      <span>888</span>
+      <span>2.8k</span>
     </span>
     <span class="post-meta-item" title="阅读时长">
       <span class="post-meta-item-icon">
         <i class="far fa-clock"></i>
       </span>
       <span class="post-meta-item-text">阅读时长 &asymp;</span>
-      <span>3 分钟</span>
+      <span>9 分钟</span>
     </span>
 </div>
 
@@ -1204,10 +1316,10 @@ <h2 class="post-title" itemprop="name headline">
     
     
     <div class="post-body" itemprop="articleBody">
-          <p>本文介绍了 <code>MySQL</code> 中 <code>skip-name-resolve</code> 参数<strong>对连接的优化作用</strong>，随之而来的权限表<strong>仅可使用 <code>IP</code> 的限制</strong>，以及如何在无法提前确定 <code>IP</code> 的情况下使用 <code>grant</code> 命令<strong>搭配通配符 <code>%</code> 进行授权</strong>。</p>
+          <p>印象里每次安装 <code>ElK</code> 组件的体验都不是很好，或多或少都遇到过奇奇怪怪的问题。本文几乎完全按照官方文档：<a target="_blank" rel="noopener" href="https://www.elastic.co/cn/blog/getting-started-with-the-elastic-stack-and-docker-compose">Getting started with the Elastic Stack and Docker Compose: Part 1</a> 通过 <code>docker compose</code> 安装 <code>elasticsearch</code>、<code>kibana</code>、<code>metricbeat</code>、<code>filebeat</code> 和 <code>logstash</code>，但是移除了 <code>ssl</code> 相关的配置。你可以直接按照原文档进行安装，但是对照本文可以帮助你更快速地移除不需要的配置以及绕开可能踩到的坑。<br>此安装方式尽量<strong>使用环境变量代替编写配置文件</strong>，便于在备份和分享时将敏感信息留存在本地。本次安装时间为 <code>2023-12-14</code>，使用官方镜像，版本为 <code>8.11.2</code>。</p>
           <!--noindex-->
             <div class="post-button">
-              <a class="btn" href="/2023/12/13/how-to-grant-when-MySQL-started-with-skip-name-resolve-mode/#more" rel="contents">
+              <a class="btn" href="/2023/12/14/install-ELK-using-Docker-Compose/#more" rel="contents">
                 阅读全文 &raquo;
               </a>
             </div>
@@ -1253,13 +1365,13 @@ <h2 class="post-title" itemprop="name headline">
     <span class="post-meta-item-icon">
       <i class="fa fa-chart-line"></i>
     </span>
-    <span title="站点总字数">125k</span>
+    <span title="站点总字数">129k</span>
   </span>
   <span class="post-meta-item">
     <span class="post-meta-item-icon">
       <i class="fa fa-coffee"></i>
     </span>
-    <span title="站点阅读时长">6:56</span>
+    <span title="站点阅读时长">7:09</span>
   </span>
 </div>
   <div class="powered-by">由 <a href="https://hexo.io/" rel="noopener" target="_blank">Hexo</a> & <a href="https://theme-next.js.org/" rel="noopener" target="_blank">NexT.Gemini</a> 强力驱动
diff --git a/leancloud_counter_security_urls.json b/leancloud_counter_security_urls.json
index 6b590ede..f18920c4 100644
--- a/leancloud_counter_security_urls.json
+++ b/leancloud_counter_security_urls.json
@@ -1 +1 @@
-[{"title":"安装 Docker","url":"/2020/08/18/install-Docker/"},{"title":"Docker 常用命令","url":"/2020/08/19/docker-frequently-used-commands/"},{"title":"Linux 常用命令和快捷键","url":"/2020/08/27/Linux-frequently-used-commands/"},{"title":"在 Ubuntu 上安装 Clash","url":"/2023/05/27/how-to-install-clash-on-ubuntu/"},{"title":"MySQL 常用命令","url":"/2020/09/04/MySQL-frequently-used-commands/"},{"title":"在 Windows 10 上安装 OpenVPN 服务端","url":"/2023/06/07/how-to-setup-OpenVPN-server-on-windows-10/"},{"title":"在 iOS 和 macOS 上安装 OpenVPN 客户端","url":"/2023/06/07/how-to-setup-OpenVPN-connect-client-on-iOS-and-macOS/"},{"title":"使用 OpenVPN 访问家庭内网","url":"/2023/06/07/how-to-use-OpenVPN-to-access-home-network/"},{"title":"如何为终端、docker 和容器设置代理","url":"/2023/06/13/how-to-configure-proxy-for-terminal-docker-and-container/"},{"title":"Ubuntu server 20.04 安装后没有分配全部磁盘空间","url":"/2023/06/24/Ubuntu-server-20-04-not-all-disk-space-was-allocated-after-installation/"},{"title":"如何在 Ubuntu 20.04 上安装 Minikube","url":"/2023/06/23/how-to-install-Minikube-on-Ubuntu-20-04/"},{"title":"如何使用 SSH 连接 Github 和服务器","url":"/2023/06/28/how-to-use-ssh-to-connect-github-and-server/"},{"title":"Tmux 常用命令和快捷键","url":"/2023/06/29/tmux-frequently-used-commands/"},{"title":"Java 类加载器源码分析","url":"/2023/07/13/Java-class-loader-source-code-analysis/"},{"title":"Spring Bean 加载过程","url":"/2023/08/10/how-does-Spring-load-beans/"},{"title":"JVM GC 的测试和分析","url":"/2023/11/01/testing-and-analysis-of-jvm-gc/"},{"title":"字符串常量池的测试和分析","url":"/2023/11/03/testing-and-analysis-of-StringTable/"},{"title":"Spring 应用 context 刷新流程","url":"/2023/08/04/Spring-application-context-refresh-process/"},{"title":"Java 垃圾收集","url":"/2023/11/07/garbage-collection-in-Java/"},{"title":"关于 Java 字节码指令的一些例子分析","url":"/2023/11/09/some-examples-of-Java-bytecode-instruction-analysis/"},{"title":"JVM 内存区域的测试和分析","url":"/2023/11/04/testing-and-analysis-of-jvm-memory-area/"},{"title":"基于 Redis 的分布式锁的简单实现","url":"/2023/11/13/simple-implementation-of-distributed-lock-based-on-Redis/"},{"title":"使用 Grafana 和 Prometheus 搭建监控","url":"/2023/11/18/setup-monitoring-using-grafana-and-prometheus/"},{"title":"JDK 动态代理和 CGLib","url":"/2023/11/19/JDK-dynamic-proxy-and-CGLib/"},{"title":"Spring AOP 如何创建代理 beans","url":"/2023/11/19/how-does-Spring-AOP-create-proxy-beans/"},{"title":"Spring 中的循环依赖","url":"/2023/11/22/circular-dependencies-in-Spring/"},{"title":"Spring @Configuration 注解的源码分析","url":"/2023/11/23/source-code-analysis-of-Spring-Configuration-annotation/"},{"title":"Dubbo SPI 的工作原理","url":"/2023/11/28/how-does-Dubbo-SPI-works/"},{"title":"Nginx 反向代理在家庭网络中的应用","url":"/2023/12/01/Nginx-reverse-proxy-for-home-networks/"},{"title":"Dubbo SPI 自适应拓展的工作原理","url":"/2023/11/29/how-does-Dubbo-SPI-adaptive-extension-works/"},{"title":"使用 logrotate 滚动 Docker 容器内的 Nginx 的日志","url":"/2023/12/02/rotating-nginx-logs-in-docker-container-with-logrotate/"},{"title":"Spring 中 @Import 注解的使用和源码分析","url":"/2023/12/04/use-and-analysis-of-Import-annotation-in-Spring/"},{"title":"Spring Boot 自定义 starter 和自动配置的工作原理","url":"/2023/12/06/custom-starter-and-auto-configuration-in-Spring-Boot/"},{"title":"Spring Boot SPI 的工作原理","url":"/2023/12/06/how-does-Spring-Boot-SPI-works/"},{"title":"Spring 中 @PropertySource 注解的使用和源码分析","url":"/2023/12/07/use-and-analysis-of-PropertySource-annotation-in-Spring/"},{"title":"ConfigurationProperties 一定要搭配 EnableConfigurationProperties 使用吗","url":"/2023/12/10/is-it-necessary-to-use-ConfigurationProperties-with-EnableConfigurationProperties/"},{"title":"Spring AutowiredAnnotationBeanPostProcessor 的源码分析","url":"/2023/12/08/source-code-analysis-of-AutowiredAnnotationBeanPostProcessor-in-Spring/"},{"title":"当 MySQL 以 skip-name-resolve 模式启动时如何使用 grant 命令","url":"/2023/12/13/how-to-grant-when-MySQL-started-with-skip-name-resolve-mode/"},{"title":"使用 Docker Compose 安装 ELK","url":"/2023/12/14/install-ELK-using-Docker-Compose/"},{"title":"synchronized 锁机制的分析和验证","url":"/2023/12/19/analysis-and-verification-of-the-synchronized-lock-mechanism/"},{"title":"Unsafe，一个“反 Java”的 class","url":"/2023/12/25/Unsafe-an-anti-Java-class/"},{"title":"Java 类 Reference 的源码分析","url":"/2023/12/27/source-code-analysis-of-Java-class-Reference/"},{"title":"探索 Java 类 Cleaner 和 Finalizer","url":"/2023/12/28/explore-the-Java-classes-Cleaner-and-Finalizer/"},{"title":"ComponentScan 扫描路径覆盖的真相","url":"/2023/12/11/the-truth-about-override-of-ComponentScan-basePackages/"},{"title":"谈谈 MySQL 事务的隔离性","url":"/2024/01/06/talk-about-isolation-of-MySQL-transactions/"},{"title":"不使用 GParted 的情况下为 VMware 中的 Ubuntu Server 增大磁盘空间","url":"/2024/01/14/increase-disk-space-of-Ubuntu-server-on-VMware-without-using-GParted/"},{"title":"使用 Vim","url":"/2024/01/18/use-vim/"},{"title":"k3s 的安装和使用","url":"/2024/01/30/installation-and-use-of-k3s/"}]
\ No newline at end of file
+[{"title":"安装 Docker","url":"/2020/08/18/install-Docker/"},{"title":"Docker 常用命令","url":"/2020/08/19/docker-frequently-used-commands/"},{"title":"Linux 常用命令和快捷键","url":"/2020/08/27/Linux-frequently-used-commands/"},{"title":"MySQL 常用命令","url":"/2020/09/04/MySQL-frequently-used-commands/"},{"title":"在 iOS 和 macOS 上安装 OpenVPN 客户端","url":"/2023/06/07/how-to-setup-OpenVPN-connect-client-on-iOS-and-macOS/"},{"title":"在 Ubuntu 上安装 Clash","url":"/2023/05/27/how-to-install-clash-on-ubuntu/"},{"title":"在 Windows 10 上安装 OpenVPN 服务端","url":"/2023/06/07/how-to-setup-OpenVPN-server-on-windows-10/"},{"title":"使用 OpenVPN 访问家庭内网","url":"/2023/06/07/how-to-use-OpenVPN-to-access-home-network/"},{"title":"如何在 Ubuntu 20.04 上安装 Minikube","url":"/2023/06/23/how-to-install-Minikube-on-Ubuntu-20-04/"},{"title":"Ubuntu server 20.04 安装后没有分配全部磁盘空间","url":"/2023/06/24/Ubuntu-server-20-04-not-all-disk-space-was-allocated-after-installation/"},{"title":"如何使用 SSH 连接 Github 和服务器","url":"/2023/06/28/how-to-use-ssh-to-connect-github-and-server/"},{"title":"Tmux 常用命令和快捷键","url":"/2023/06/29/tmux-frequently-used-commands/"},{"title":"Spring 应用 context 刷新流程","url":"/2023/08/04/Spring-application-context-refresh-process/"},{"title":"Java 类加载器源码分析","url":"/2023/07/13/Java-class-loader-source-code-analysis/"},{"title":"Spring Bean 加载过程","url":"/2023/08/10/how-does-Spring-load-beans/"},{"title":"JVM GC 的测试和分析","url":"/2023/11/01/testing-and-analysis-of-jvm-gc/"},{"title":"字符串常量池的测试和分析","url":"/2023/11/03/testing-and-analysis-of-StringTable/"},{"title":"JVM 内存区域的测试和分析","url":"/2023/11/04/testing-and-analysis-of-jvm-memory-area/"},{"title":"Java 垃圾收集","url":"/2023/11/07/garbage-collection-in-Java/"},{"title":"关于 Java 字节码指令的一些例子分析","url":"/2023/11/09/some-examples-of-Java-bytecode-instruction-analysis/"},{"title":"基于 Redis 的分布式锁的简单实现","url":"/2023/11/13/simple-implementation-of-distributed-lock-based-on-Redis/"},{"title":"使用 Grafana 和 Prometheus 搭建监控","url":"/2023/11/18/setup-monitoring-using-grafana-and-prometheus/"},{"title":"JDK 动态代理和 CGLib","url":"/2023/11/19/JDK-dynamic-proxy-and-CGLib/"},{"title":"Spring AOP 如何创建代理 beans","url":"/2023/11/19/how-does-Spring-AOP-create-proxy-beans/"},{"title":"Spring 中的循环依赖","url":"/2023/11/22/circular-dependencies-in-Spring/"},{"title":"如何为终端、docker 和容器设置代理","url":"/2023/06/13/how-to-configure-proxy-for-terminal-docker-and-container/"},{"title":"Nginx 反向代理在家庭网络中的应用","url":"/2023/12/01/Nginx-reverse-proxy-for-home-networks/"},{"title":"使用 logrotate 滚动 Docker 容器内的 Nginx 的日志","url":"/2023/12/02/rotating-nginx-logs-in-docker-container-with-logrotate/"},{"title":"Dubbo SPI 自适应拓展的工作原理","url":"/2023/11/29/how-does-Dubbo-SPI-adaptive-extension-works/"},{"title":"Spring 中 @Import 注解的使用和源码分析","url":"/2023/12/04/use-and-analysis-of-Import-annotation-in-Spring/"},{"title":"Spring Boot 自定义 starter 和自动配置的工作原理","url":"/2023/12/06/custom-starter-and-auto-configuration-in-Spring-Boot/"},{"title":"Spring Boot SPI 的工作原理","url":"/2023/12/06/how-does-Spring-Boot-SPI-works/"},{"title":"Spring 中 @PropertySource 注解的使用和源码分析","url":"/2023/12/07/use-and-analysis-of-PropertySource-annotation-in-Spring/"},{"title":"Spring AutowiredAnnotationBeanPostProcessor 的源码分析","url":"/2023/12/08/source-code-analysis-of-AutowiredAnnotationBeanPostProcessor-in-Spring/"},{"title":"ConfigurationProperties 一定要搭配 EnableConfigurationProperties 使用吗","url":"/2023/12/10/is-it-necessary-to-use-ConfigurationProperties-with-EnableConfigurationProperties/"},{"title":"Dubbo SPI 的工作原理","url":"/2023/11/28/how-does-Dubbo-SPI-works/"},{"title":"当 MySQL 以 skip-name-resolve 模式启动时如何使用 grant 命令","url":"/2023/12/13/how-to-grant-when-MySQL-started-with-skip-name-resolve-mode/"},{"title":"使用 Docker Compose 安装 ELK","url":"/2023/12/14/install-ELK-using-Docker-Compose/"},{"title":"ComponentScan 扫描路径覆盖的真相","url":"/2023/12/11/the-truth-about-override-of-ComponentScan-basePackages/"},{"title":"synchronized 锁机制的分析和验证","url":"/2023/12/19/analysis-and-verification-of-the-synchronized-lock-mechanism/"},{"title":"Unsafe，一个“反 Java”的 class","url":"/2023/12/25/Unsafe-an-anti-Java-class/"},{"title":"Java 类 Reference 的源码分析","url":"/2023/12/27/source-code-analysis-of-Java-class-Reference/"},{"title":"谈谈 MySQL 事务的隔离性","url":"/2024/01/06/talk-about-isolation-of-MySQL-transactions/"},{"title":"探索 Java 类 Cleaner 和 Finalizer","url":"/2023/12/28/explore-the-Java-classes-Cleaner-and-Finalizer/"},{"title":"不使用 GParted 的情况下为 VMware 中的 Ubuntu Server 增大磁盘空间","url":"/2024/01/14/increase-disk-space-of-Ubuntu-server-on-VMware-without-using-GParted/"},{"title":"使用 Vim","url":"/2024/01/18/use-vim/"},{"title":"k3s 的安装和使用","url":"/2024/01/30/installation-and-use-of-k3s/"},{"title":"信息的表示和处理","url":"/2024/03/11/representating-and-manipulating-information/"},{"title":"Spring @Configuration 注解的源码分析","url":"/2023/11/23/source-code-analysis-of-Spring-Configuration-annotation/"}]
\ No newline at end of file
diff --git a/page/2/index.html b/page/2/index.html
index e03ef86e..14e0854b 100644
--- a/page/2/index.html
+++ b/page/2/index.html
@@ -151,7 +151,7 @@ <h1 class="site-title">Moralok</h1>
   <nav class="site-state">
       <div class="site-state-item site-state-posts">
         <a href="/archives/">
-          <span class="site-state-item-count">48</span>
+          <span class="site-state-item-count">49</span>
           <span class="site-state-item-name">日志</span>
         </a>
       </div>
@@ -188,7 +188,7 @@ <h1 class="site-title">Moralok</h1>
   
 
   <article itemscope itemtype="http://schema.org/Article" class="post-content" lang="">
-    <link itemprop="mainEntityOfPage" href="https://www.moralok.com/2023/12/11/the-truth-about-override-of-ComponentScan-basePackages/">
+    <link itemprop="mainEntityOfPage" href="https://www.moralok.com/2023/12/13/how-to-grant-when-MySQL-started-with-skip-name-resolve-mode/">
 
     <span hidden itemprop="author" itemscope itemtype="http://schema.org/Person">
       <meta itemprop="image" content="/images/avatar.gif">
@@ -206,7 +206,7 @@ <h1 class="site-title">Moralok</h1>
     </span>
       <header class="post-header">
         <h2 class="post-title" itemprop="name headline">
-          <a href="/2023/12/11/the-truth-about-override-of-ComponentScan-basePackages/" class="post-title-link" itemprop="url">ComponentScan 扫描路径覆盖的真相</a>
+          <a href="/2023/12/13/how-to-grant-when-MySQL-started-with-skip-name-resolve-mode/" class="post-title-link" itemprop="url">当 MySQL 以 skip-name-resolve 模式启动时如何使用 grant 命令</a>
         </h2>
 
         <div class="post-meta-container">
@@ -217,18 +217,18 @@ <h2 class="post-title" itemprop="name headline">
       </span>
       <span class="post-meta-item-text">发表于</span>
 
-      <time title="创建时间：2023-12-11 10:11:22" itemprop="dateCreated datePublished" datetime="2023-12-11T10:11:22+08:00">2023-12-11</time>
+      <time title="创建时间：2023-12-13 12:16:17" itemprop="dateCreated datePublished" datetime="2023-12-13T12:16:17+08:00">2023-12-13</time>
     </span>
     <span class="post-meta-item">
       <span class="post-meta-item-icon">
         <i class="far fa-calendar-check"></i>
       </span>
       <span class="post-meta-item-text">更新于</span>
-      <time title="修改时间：2024-04-10 22:49:47" itemprop="dateModified" datetime="2024-04-10T22:49:47+08:00">2024-04-10</time>
+      <time title="修改时间：2024-04-24 02:42:37" itemprop="dateModified" datetime="2024-04-24T02:42:37+08:00">2024-04-24</time>
     </span>
 
   
-    <span id="/2023/12/11/the-truth-about-override-of-ComponentScan-basePackages/" class="post-meta-item leancloud_visitors" data-flag-title="ComponentScan 扫描路径覆盖的真相" title="阅读次数">
+    <span id="/2023/12/13/how-to-grant-when-MySQL-started-with-skip-name-resolve-mode/" class="post-meta-item leancloud_visitors" data-flag-title="当 MySQL 以 skip-name-resolve 模式启动时如何使用 grant 命令" title="阅读次数">
       <span class="post-meta-item-icon">
         <i class="far fa-eye"></i>
       </span>
@@ -241,14 +241,14 @@ <h2 class="post-title" itemprop="name headline">
         <i class="far fa-file-word"></i>
       </span>
       <span class="post-meta-item-text">本文字数：</span>
-      <span>4.9k</span>
+      <span>888</span>
     </span>
     <span class="post-meta-item" title="阅读时长">
       <span class="post-meta-item-icon">
         <i class="far fa-clock"></i>
       </span>
       <span class="post-meta-item-text">阅读时长 &asymp;</span>
-      <span>16 分钟</span>
+      <span>3 分钟</span>
     </span>
 </div>
 
@@ -259,10 +259,10 @@ <h2 class="post-title" itemprop="name headline">
     
     
     <div class="post-body" itemprop="articleBody">
-          <p><code>@ComponentScan</code> 注解是 <code>Spring</code> 中很常用的注解，用于扫描并加载指定类路径下的 <code>Bean</code>，而 <code>Spring Boot</code> 为了便捷使用 <code>@SpringBootApplication</code> 组合注解集成了 <code>@ComponentScan</code> 的能力。也许你听说过使用后者会覆盖前者中关于包扫描的设置，但你是否质疑过这个“不合常理”的结论？是否好奇过为什么它们不像其他注解在嵌套使用时可以同时生效？又是否好奇过 <code>@SpringBootApplication</code> 可以间接设置 <code>@ComponentScan</code> 属性的原因？本文从源码角度分析 <code>@ComponentScan</code> 的工作原理，揭示它独特的检索算法和注解层次结构中的属性覆盖机制。</p>
+          <p>本文介绍了 <code>MySQL</code> 中 <code>skip-name-resolve</code> 参数<strong>对连接的优化作用</strong>，随之而来的权限表<strong>仅可使用 <code>IP</code> 的限制</strong>，以及如何在无法提前确定 <code>IP</code> 的情况下使用 <code>grant</code> 命令<strong>搭配通配符 <code>%</code> 进行授权</strong>。</p>
           <!--noindex-->
             <div class="post-button">
-              <a class="btn" href="/2023/12/11/the-truth-about-override-of-ComponentScan-basePackages/#more" rel="contents">
+              <a class="btn" href="/2023/12/13/how-to-grant-when-MySQL-started-with-skip-name-resolve-mode/#more" rel="contents">
                 阅读全文 &raquo;
               </a>
             </div>
@@ -293,7 +293,7 @@ <h2 class="post-title" itemprop="name headline">
   
 
   <article itemscope itemtype="http://schema.org/Article" class="post-content" lang="">
-    <link itemprop="mainEntityOfPage" href="https://www.moralok.com/2023/12/10/is-it-necessary-to-use-ConfigurationProperties-with-EnableConfigurationProperties/">
+    <link itemprop="mainEntityOfPage" href="https://www.moralok.com/2023/12/11/the-truth-about-override-of-ComponentScan-basePackages/">
 
     <span hidden itemprop="author" itemscope itemtype="http://schema.org/Person">
       <meta itemprop="image" content="/images/avatar.gif">
@@ -311,7 +311,7 @@ <h2 class="post-title" itemprop="name headline">
     </span>
       <header class="post-header">
         <h2 class="post-title" itemprop="name headline">
-          <a href="/2023/12/10/is-it-necessary-to-use-ConfigurationProperties-with-EnableConfigurationProperties/" class="post-title-link" itemprop="url">ConfigurationProperties 一定要搭配 EnableConfigurationProperties 使用吗</a>
+          <a href="/2023/12/11/the-truth-about-override-of-ComponentScan-basePackages/" class="post-title-link" itemprop="url">ComponentScan 扫描路径覆盖的真相</a>
         </h2>
 
         <div class="post-meta-container">
@@ -322,18 +322,18 @@ <h2 class="post-title" itemprop="name headline">
       </span>
       <span class="post-meta-item-text">发表于</span>
 
-      <time title="创建时间：2023-12-10 11:41:00" itemprop="dateCreated datePublished" datetime="2023-12-10T11:41:00+08:00">2023-12-10</time>
+      <time title="创建时间：2023-12-11 10:11:22" itemprop="dateCreated datePublished" datetime="2023-12-11T10:11:22+08:00">2023-12-11</time>
     </span>
     <span class="post-meta-item">
       <span class="post-meta-item-icon">
         <i class="far fa-calendar-check"></i>
       </span>
       <span class="post-meta-item-text">更新于</span>
-      <time title="修改时间：2024-04-10 22:49:47" itemprop="dateModified" datetime="2024-04-10T22:49:47+08:00">2024-04-10</time>
+      <time title="修改时间：2024-04-24 02:42:37" itemprop="dateModified" datetime="2024-04-24T02:42:37+08:00">2024-04-24</time>
     </span>
 
   
-    <span id="/2023/12/10/is-it-necessary-to-use-ConfigurationProperties-with-EnableConfigurationProperties/" class="post-meta-item leancloud_visitors" data-flag-title="ConfigurationProperties 一定要搭配 EnableConfigurationProperties 使用吗" title="阅读次数">
+    <span id="/2023/12/11/the-truth-about-override-of-ComponentScan-basePackages/" class="post-meta-item leancloud_visitors" data-flag-title="ComponentScan 扫描路径覆盖的真相" title="阅读次数">
       <span class="post-meta-item-icon">
         <i class="far fa-eye"></i>
       </span>
@@ -346,14 +346,14 @@ <h2 class="post-title" itemprop="name headline">
         <i class="far fa-file-word"></i>
       </span>
       <span class="post-meta-item-text">本文字数：</span>
-      <span>1.9k</span>
+      <span>4.9k</span>
     </span>
     <span class="post-meta-item" title="阅读时长">
       <span class="post-meta-item-icon">
         <i class="far fa-clock"></i>
       </span>
       <span class="post-meta-item-text">阅读时长 &asymp;</span>
-      <span>6 分钟</span>
+      <span>16 分钟</span>
     </span>
 </div>
 
@@ -364,10 +364,10 @@ <h2 class="post-title" itemprop="name headline">
     
     
     <div class="post-body" itemprop="articleBody">
-          <p><code>@ConfigurationProperties</code> 和 <code>@EnableConfigurationProperties</code> 是 <code>Spring Boot</code> 中常用的注解，提供了方便和强大的外部化配置支持。尽管它们常常一起出现，但是它们真的必须一起使用吗？<code>Spring Boot</code> 的灵活性常常让我们忽略配置背后产生的作用究竟是什么？本文将从源码角度出发分析两个注解的<strong>作用时机</strong>和<strong>工作原理</strong>。</p>
+          <p><code>@ComponentScan</code> 注解是 <code>Spring</code> 中很常用的注解，用于扫描并加载指定类路径下的 <code>Bean</code>，而 <code>Spring Boot</code> 为了便捷使用 <code>@SpringBootApplication</code> 组合注解集成了 <code>@ComponentScan</code> 的能力。也许你听说过使用后者会覆盖前者中关于包扫描的设置，但你是否质疑过这个“不合常理”的结论？是否好奇过为什么它们不像其他注解在嵌套使用时可以同时生效？又是否好奇过 <code>@SpringBootApplication</code> 可以间接设置 <code>@ComponentScan</code> 属性的原因？本文从源码角度分析 <code>@ComponentScan</code> 的工作原理，揭示它独特的检索算法和注解层次结构中的属性覆盖机制。</p>
           <!--noindex-->
             <div class="post-button">
-              <a class="btn" href="/2023/12/10/is-it-necessary-to-use-ConfigurationProperties-with-EnableConfigurationProperties/#more" rel="contents">
+              <a class="btn" href="/2023/12/11/the-truth-about-override-of-ComponentScan-basePackages/#more" rel="contents">
                 阅读全文 &raquo;
               </a>
             </div>
@@ -398,7 +398,7 @@ <h2 class="post-title" itemprop="name headline">
   
 
   <article itemscope itemtype="http://schema.org/Article" class="post-content" lang="">
-    <link itemprop="mainEntityOfPage" href="https://www.moralok.com/2023/12/08/source-code-analysis-of-AutowiredAnnotationBeanPostProcessor-in-Spring/">
+    <link itemprop="mainEntityOfPage" href="https://www.moralok.com/2023/12/10/is-it-necessary-to-use-ConfigurationProperties-with-EnableConfigurationProperties/">
 
     <span hidden itemprop="author" itemscope itemtype="http://schema.org/Person">
       <meta itemprop="image" content="/images/avatar.gif">
@@ -416,7 +416,7 @@ <h2 class="post-title" itemprop="name headline">
     </span>
       <header class="post-header">
         <h2 class="post-title" itemprop="name headline">
-          <a href="/2023/12/08/source-code-analysis-of-AutowiredAnnotationBeanPostProcessor-in-Spring/" class="post-title-link" itemprop="url">Spring AutowiredAnnotationBeanPostProcessor 的源码分析</a>
+          <a href="/2023/12/10/is-it-necessary-to-use-ConfigurationProperties-with-EnableConfigurationProperties/" class="post-title-link" itemprop="url">ConfigurationProperties 一定要搭配 EnableConfigurationProperties 使用吗</a>
         </h2>
 
         <div class="post-meta-container">
@@ -427,18 +427,18 @@ <h2 class="post-title" itemprop="name headline">
       </span>
       <span class="post-meta-item-text">发表于</span>
 
-      <time title="创建时间：2023-12-08 12:00:30" itemprop="dateCreated datePublished" datetime="2023-12-08T12:00:30+08:00">2023-12-08</time>
+      <time title="创建时间：2023-12-10 11:41:00" itemprop="dateCreated datePublished" datetime="2023-12-10T11:41:00+08:00">2023-12-10</time>
     </span>
     <span class="post-meta-item">
       <span class="post-meta-item-icon">
         <i class="far fa-calendar-check"></i>
       </span>
       <span class="post-meta-item-text">更新于</span>
-      <time title="修改时间：2024-04-10 22:49:47" itemprop="dateModified" datetime="2024-04-10T22:49:47+08:00">2024-04-10</time>
+      <time title="修改时间：2024-04-24 02:42:37" itemprop="dateModified" datetime="2024-04-24T02:42:37+08:00">2024-04-24</time>
     </span>
 
   
-    <span id="/2023/12/08/source-code-analysis-of-AutowiredAnnotationBeanPostProcessor-in-Spring/" class="post-meta-item leancloud_visitors" data-flag-title="Spring AutowiredAnnotationBeanPostProcessor 的源码分析" title="阅读次数">
+    <span id="/2023/12/10/is-it-necessary-to-use-ConfigurationProperties-with-EnableConfigurationProperties/" class="post-meta-item leancloud_visitors" data-flag-title="ConfigurationProperties 一定要搭配 EnableConfigurationProperties 使用吗" title="阅读次数">
       <span class="post-meta-item-icon">
         <i class="far fa-eye"></i>
       </span>
@@ -451,14 +451,14 @@ <h2 class="post-title" itemprop="name headline">
         <i class="far fa-file-word"></i>
       </span>
       <span class="post-meta-item-text">本文字数：</span>
-      <span>3.8k</span>
+      <span>1.9k</span>
     </span>
     <span class="post-meta-item" title="阅读时长">
       <span class="post-meta-item-icon">
         <i class="far fa-clock"></i>
       </span>
       <span class="post-meta-item-text">阅读时长 &asymp;</span>
-      <span>13 分钟</span>
+      <span>6 分钟</span>
     </span>
 </div>
 
@@ -469,10 +469,10 @@ <h2 class="post-title" itemprop="name headline">
     
     
     <div class="post-body" itemprop="articleBody">
-          <p>在 <code>Spring</code> 中，<code>AutowiredAnnotationBeanPostProcessor</code> 是一个非常重要的后处理器，它可以自动装配标注注解的字段和方法，默认使用 <code>@Autowired</code> 和 <code>@Value</code> 注解，可以支持 <code>JSR-330</code> 的 <code>@Inject</code> 注解。本文通过分析源码介绍它的调用时机和工作原理。</p>
+          <p><code>@ConfigurationProperties</code> 和 <code>@EnableConfigurationProperties</code> 是 <code>Spring Boot</code> 中常用的注解，提供了方便和强大的外部化配置支持。尽管它们常常一起出现，但是它们真的必须一起使用吗？<code>Spring Boot</code> 的灵活性常常让我们忽略配置背后产生的作用究竟是什么？本文将从源码角度出发分析两个注解的<strong>作用时机</strong>和<strong>工作原理</strong>。</p>
           <!--noindex-->
             <div class="post-button">
-              <a class="btn" href="/2023/12/08/source-code-analysis-of-AutowiredAnnotationBeanPostProcessor-in-Spring/#more" rel="contents">
+              <a class="btn" href="/2023/12/10/is-it-necessary-to-use-ConfigurationProperties-with-EnableConfigurationProperties/#more" rel="contents">
                 阅读全文 &raquo;
               </a>
             </div>
@@ -503,7 +503,7 @@ <h2 class="post-title" itemprop="name headline">
   
 
   <article itemscope itemtype="http://schema.org/Article" class="post-content" lang="">
-    <link itemprop="mainEntityOfPage" href="https://www.moralok.com/2023/12/07/use-and-analysis-of-PropertySource-annotation-in-Spring/">
+    <link itemprop="mainEntityOfPage" href="https://www.moralok.com/2023/12/08/source-code-analysis-of-AutowiredAnnotationBeanPostProcessor-in-Spring/">
 
     <span hidden itemprop="author" itemscope itemtype="http://schema.org/Person">
       <meta itemprop="image" content="/images/avatar.gif">
@@ -521,7 +521,7 @@ <h2 class="post-title" itemprop="name headline">
     </span>
       <header class="post-header">
         <h2 class="post-title" itemprop="name headline">
-          <a href="/2023/12/07/use-and-analysis-of-PropertySource-annotation-in-Spring/" class="post-title-link" itemprop="url">Spring 中 @PropertySource 注解的使用和源码分析</a>
+          <a href="/2023/12/08/source-code-analysis-of-AutowiredAnnotationBeanPostProcessor-in-Spring/" class="post-title-link" itemprop="url">Spring AutowiredAnnotationBeanPostProcessor 的源码分析</a>
         </h2>
 
         <div class="post-meta-container">
@@ -532,18 +532,18 @@ <h2 class="post-title" itemprop="name headline">
       </span>
       <span class="post-meta-item-text">发表于</span>
 
-      <time title="创建时间：2023-12-07 11:55:49" itemprop="dateCreated datePublished" datetime="2023-12-07T11:55:49+08:00">2023-12-07</time>
+      <time title="创建时间：2023-12-08 12:00:30" itemprop="dateCreated datePublished" datetime="2023-12-08T12:00:30+08:00">2023-12-08</time>
     </span>
     <span class="post-meta-item">
       <span class="post-meta-item-icon">
         <i class="far fa-calendar-check"></i>
       </span>
       <span class="post-meta-item-text">更新于</span>
-      <time title="修改时间：2024-04-10 22:49:47" itemprop="dateModified" datetime="2024-04-10T22:49:47+08:00">2024-04-10</time>
+      <time title="修改时间：2024-04-24 02:42:37" itemprop="dateModified" datetime="2024-04-24T02:42:37+08:00">2024-04-24</time>
     </span>
 
   
-    <span id="/2023/12/07/use-and-analysis-of-PropertySource-annotation-in-Spring/" class="post-meta-item leancloud_visitors" data-flag-title="Spring 中 @PropertySource 注解的使用和源码分析" title="阅读次数">
+    <span id="/2023/12/08/source-code-analysis-of-AutowiredAnnotationBeanPostProcessor-in-Spring/" class="post-meta-item leancloud_visitors" data-flag-title="Spring AutowiredAnnotationBeanPostProcessor 的源码分析" title="阅读次数">
       <span class="post-meta-item-icon">
         <i class="far fa-eye"></i>
       </span>
@@ -556,14 +556,14 @@ <h2 class="post-title" itemprop="name headline">
         <i class="far fa-file-word"></i>
       </span>
       <span class="post-meta-item-text">本文字数：</span>
-      <span>1.3k</span>
+      <span>3.8k</span>
     </span>
     <span class="post-meta-item" title="阅读时长">
       <span class="post-meta-item-icon">
         <i class="far fa-clock"></i>
       </span>
       <span class="post-meta-item-text">阅读时长 &asymp;</span>
-      <span>4 分钟</span>
+      <span>13 分钟</span>
     </span>
 </div>
 
@@ -574,10 +574,10 @@ <h2 class="post-title" itemprop="name headline">
     
     
     <div class="post-body" itemprop="articleBody">
-          <p><code>@PropertySource</code> 注解提供了一种方便的声明性机制，用于将 <code>PropertySource</code> 添加到 <code>Spring</code> 容器的 <code>Environment</code> 环境中。该注解通常搭配 <code>@Configuration</code> 注解一起使用。本文将介绍如何使用 <code>@PropertySource</code> 注解，并通过分析源码解释外部配置文件是如何被解析进入 <code>Spring</code> 的 <code>Environment</code> 中。</p>
+          <p>在 <code>Spring</code> 中，<code>AutowiredAnnotationBeanPostProcessor</code> 是一个非常重要的后处理器，它可以自动装配标注注解的字段和方法，默认使用 <code>@Autowired</code> 和 <code>@Value</code> 注解，可以支持 <code>JSR-330</code> 的 <code>@Inject</code> 注解。本文通过分析源码介绍它的调用时机和工作原理。</p>
           <!--noindex-->
             <div class="post-button">
-              <a class="btn" href="/2023/12/07/use-and-analysis-of-PropertySource-annotation-in-Spring/#more" rel="contents">
+              <a class="btn" href="/2023/12/08/source-code-analysis-of-AutowiredAnnotationBeanPostProcessor-in-Spring/#more" rel="contents">
                 阅读全文 &raquo;
               </a>
             </div>
@@ -608,7 +608,7 @@ <h2 class="post-title" itemprop="name headline">
   
 
   <article itemscope itemtype="http://schema.org/Article" class="post-content" lang="">
-    <link itemprop="mainEntityOfPage" href="https://www.moralok.com/2023/12/06/how-does-Spring-Boot-SPI-works/">
+    <link itemprop="mainEntityOfPage" href="https://www.moralok.com/2023/12/07/use-and-analysis-of-PropertySource-annotation-in-Spring/">
 
     <span hidden itemprop="author" itemscope itemtype="http://schema.org/Person">
       <meta itemprop="image" content="/images/avatar.gif">
@@ -626,7 +626,7 @@ <h2 class="post-title" itemprop="name headline">
     </span>
       <header class="post-header">
         <h2 class="post-title" itemprop="name headline">
-          <a href="/2023/12/06/how-does-Spring-Boot-SPI-works/" class="post-title-link" itemprop="url">Spring Boot SPI 的工作原理</a>
+          <a href="/2023/12/07/use-and-analysis-of-PropertySource-annotation-in-Spring/" class="post-title-link" itemprop="url">Spring 中 @PropertySource 注解的使用和源码分析</a>
         </h2>
 
         <div class="post-meta-container">
@@ -637,18 +637,18 @@ <h2 class="post-title" itemprop="name headline">
       </span>
       <span class="post-meta-item-text">发表于</span>
 
-      <time title="创建时间：2023-12-06 17:27:55" itemprop="dateCreated datePublished" datetime="2023-12-06T17:27:55+08:00">2023-12-06</time>
+      <time title="创建时间：2023-12-07 11:55:49" itemprop="dateCreated datePublished" datetime="2023-12-07T11:55:49+08:00">2023-12-07</time>
     </span>
     <span class="post-meta-item">
       <span class="post-meta-item-icon">
         <i class="far fa-calendar-check"></i>
       </span>
       <span class="post-meta-item-text">更新于</span>
-      <time title="修改时间：2024-04-10 22:49:47" itemprop="dateModified" datetime="2024-04-10T22:49:47+08:00">2024-04-10</time>
+      <time title="修改时间：2024-04-24 02:42:37" itemprop="dateModified" datetime="2024-04-24T02:42:37+08:00">2024-04-24</time>
     </span>
 
   
-    <span id="/2023/12/06/how-does-Spring-Boot-SPI-works/" class="post-meta-item leancloud_visitors" data-flag-title="Spring Boot SPI 的工作原理" title="阅读次数">
+    <span id="/2023/12/07/use-and-analysis-of-PropertySource-annotation-in-Spring/" class="post-meta-item leancloud_visitors" data-flag-title="Spring 中 @PropertySource 注解的使用和源码分析" title="阅读次数">
       <span class="post-meta-item-icon">
         <i class="far fa-eye"></i>
       </span>
@@ -661,7 +661,7 @@ <h2 class="post-title" itemprop="name headline">
         <i class="far fa-file-word"></i>
       </span>
       <span class="post-meta-item-text">本文字数：</span>
-      <span>1.1k</span>
+      <span>1.3k</span>
     </span>
     <span class="post-meta-item" title="阅读时长">
       <span class="post-meta-item-icon">
@@ -679,10 +679,10 @@ <h2 class="post-title" itemprop="name headline">
     
     
     <div class="post-body" itemprop="articleBody">
-          <p>在分析 <code>Spring Boot</code> 自动配置的工作原理时，我们并没有深入“如何获得配置在 <code>spring.factories</code> 中的自动配置类”。本文将从图解和源码两个角度分析 <code>Spring Boot SPI</code> 机制，了解 <code>spring.factories</code> 中的配置是如何被加载和解析成为缓存中的“接口-实现”键值对。</p>
+          <p><code>@PropertySource</code> 注解提供了一种方便的声明性机制，用于将 <code>PropertySource</code> 添加到 <code>Spring</code> 容器的 <code>Environment</code> 环境中。该注解通常搭配 <code>@Configuration</code> 注解一起使用。本文将介绍如何使用 <code>@PropertySource</code> 注解，并通过分析源码解释外部配置文件是如何被解析进入 <code>Spring</code> 的 <code>Environment</code> 中。</p>
           <!--noindex-->
             <div class="post-button">
-              <a class="btn" href="/2023/12/06/how-does-Spring-Boot-SPI-works/#more" rel="contents">
+              <a class="btn" href="/2023/12/07/use-and-analysis-of-PropertySource-annotation-in-Spring/#more" rel="contents">
                 阅读全文 &raquo;
               </a>
             </div>
@@ -713,7 +713,7 @@ <h2 class="post-title" itemprop="name headline">
   
 
   <article itemscope itemtype="http://schema.org/Article" class="post-content" lang="">
-    <link itemprop="mainEntityOfPage" href="https://www.moralok.com/2023/12/06/custom-starter-and-auto-configuration-in-Spring-Boot/">
+    <link itemprop="mainEntityOfPage" href="https://www.moralok.com/2023/12/06/how-does-Spring-Boot-SPI-works/">
 
     <span hidden itemprop="author" itemscope itemtype="http://schema.org/Person">
       <meta itemprop="image" content="/images/avatar.gif">
@@ -731,7 +731,7 @@ <h2 class="post-title" itemprop="name headline">
     </span>
       <header class="post-header">
         <h2 class="post-title" itemprop="name headline">
-          <a href="/2023/12/06/custom-starter-and-auto-configuration-in-Spring-Boot/" class="post-title-link" itemprop="url">Spring Boot 自定义 starter 和自动配置的工作原理</a>
+          <a href="/2023/12/06/how-does-Spring-Boot-SPI-works/" class="post-title-link" itemprop="url">Spring Boot SPI 的工作原理</a>
         </h2>
 
         <div class="post-meta-container">
@@ -742,18 +742,18 @@ <h2 class="post-title" itemprop="name headline">
       </span>
       <span class="post-meta-item-text">发表于</span>
 
-      <time title="创建时间：2023-12-06 08:02:11" itemprop="dateCreated datePublished" datetime="2023-12-06T08:02:11+08:00">2023-12-06</time>
+      <time title="创建时间：2023-12-06 17:27:55" itemprop="dateCreated datePublished" datetime="2023-12-06T17:27:55+08:00">2023-12-06</time>
     </span>
     <span class="post-meta-item">
       <span class="post-meta-item-icon">
         <i class="far fa-calendar-check"></i>
       </span>
       <span class="post-meta-item-text">更新于</span>
-      <time title="修改时间：2024-04-10 22:49:47" itemprop="dateModified" datetime="2024-04-10T22:49:47+08:00">2024-04-10</time>
+      <time title="修改时间：2024-04-24 02:42:37" itemprop="dateModified" datetime="2024-04-24T02:42:37+08:00">2024-04-24</time>
     </span>
 
   
-    <span id="/2023/12/06/custom-starter-and-auto-configuration-in-Spring-Boot/" class="post-meta-item leancloud_visitors" data-flag-title="Spring Boot 自定义 starter 和自动配置的工作原理" title="阅读次数">
+    <span id="/2023/12/06/how-does-Spring-Boot-SPI-works/" class="post-meta-item leancloud_visitors" data-flag-title="Spring Boot SPI 的工作原理" title="阅读次数">
       <span class="post-meta-item-icon">
         <i class="far fa-eye"></i>
       </span>
@@ -766,14 +766,14 @@ <h2 class="post-title" itemprop="name headline">
         <i class="far fa-file-word"></i>
       </span>
       <span class="post-meta-item-text">本文字数：</span>
-      <span>2.6k</span>
+      <span>1.1k</span>
     </span>
     <span class="post-meta-item" title="阅读时长">
       <span class="post-meta-item-icon">
         <i class="far fa-clock"></i>
       </span>
       <span class="post-meta-item-text">阅读时长 &asymp;</span>
-      <span>9 分钟</span>
+      <span>4 分钟</span>
     </span>
 </div>
 
@@ -784,10 +784,10 @@ <h2 class="post-title" itemprop="name headline">
     
     
     <div class="post-body" itemprop="articleBody">
-          <p>如果你正在参与一个共享库的开发，你可能会想为使用方提供自动配置的支持，以帮助对方快速地接入和使用。自动配置机制往往和 <code>starter</code> 联系在一起，本文将介绍如何创建一个自定义的 <code>starter</code> 并从源码角度分析 <code>Spring Boot</code> 自动配置的工作原理。</p>
+          <p>在分析 <code>Spring Boot</code> 自动配置的工作原理时，我们并没有深入“如何获得配置在 <code>spring.factories</code> 中的自动配置类”。本文将从图解和源码两个角度分析 <code>Spring Boot SPI</code> 机制，了解 <code>spring.factories</code> 中的配置是如何被加载和解析成为缓存中的“接口-实现”键值对。</p>
           <!--noindex-->
             <div class="post-button">
-              <a class="btn" href="/2023/12/06/custom-starter-and-auto-configuration-in-Spring-Boot/#more" rel="contents">
+              <a class="btn" href="/2023/12/06/how-does-Spring-Boot-SPI-works/#more" rel="contents">
                 阅读全文 &raquo;
               </a>
             </div>
@@ -818,7 +818,7 @@ <h2 class="post-title" itemprop="name headline">
   
 
   <article itemscope itemtype="http://schema.org/Article" class="post-content" lang="">
-    <link itemprop="mainEntityOfPage" href="https://www.moralok.com/2023/12/04/use-and-analysis-of-Import-annotation-in-Spring/">
+    <link itemprop="mainEntityOfPage" href="https://www.moralok.com/2023/12/06/custom-starter-and-auto-configuration-in-Spring-Boot/">
 
     <span hidden itemprop="author" itemscope itemtype="http://schema.org/Person">
       <meta itemprop="image" content="/images/avatar.gif">
@@ -836,7 +836,7 @@ <h2 class="post-title" itemprop="name headline">
     </span>
       <header class="post-header">
         <h2 class="post-title" itemprop="name headline">
-          <a href="/2023/12/04/use-and-analysis-of-Import-annotation-in-Spring/" class="post-title-link" itemprop="url">Spring 中 @Import 注解的使用和源码分析</a>
+          <a href="/2023/12/06/custom-starter-and-auto-configuration-in-Spring-Boot/" class="post-title-link" itemprop="url">Spring Boot 自定义 starter 和自动配置的工作原理</a>
         </h2>
 
         <div class="post-meta-container">
@@ -847,18 +847,18 @@ <h2 class="post-title" itemprop="name headline">
       </span>
       <span class="post-meta-item-text">发表于</span>
 
-      <time title="创建时间：2023-12-04 08:36:21" itemprop="dateCreated datePublished" datetime="2023-12-04T08:36:21+08:00">2023-12-04</time>
+      <time title="创建时间：2023-12-06 08:02:11" itemprop="dateCreated datePublished" datetime="2023-12-06T08:02:11+08:00">2023-12-06</time>
     </span>
     <span class="post-meta-item">
       <span class="post-meta-item-icon">
         <i class="far fa-calendar-check"></i>
       </span>
       <span class="post-meta-item-text">更新于</span>
-      <time title="修改时间：2024-04-10 22:49:47" itemprop="dateModified" datetime="2024-04-10T22:49:47+08:00">2024-04-10</time>
+      <time title="修改时间：2024-04-24 02:42:37" itemprop="dateModified" datetime="2024-04-24T02:42:37+08:00">2024-04-24</time>
     </span>
 
   
-    <span id="/2023/12/04/use-and-analysis-of-Import-annotation-in-Spring/" class="post-meta-item leancloud_visitors" data-flag-title="Spring 中 @Import 注解的使用和源码分析" title="阅读次数">
+    <span id="/2023/12/06/custom-starter-and-auto-configuration-in-Spring-Boot/" class="post-meta-item leancloud_visitors" data-flag-title="Spring Boot 自定义 starter 和自动配置的工作原理" title="阅读次数">
       <span class="post-meta-item-icon">
         <i class="far fa-eye"></i>
       </span>
@@ -871,14 +871,14 @@ <h2 class="post-title" itemprop="name headline">
         <i class="far fa-file-word"></i>
       </span>
       <span class="post-meta-item-text">本文字数：</span>
-      <span>3.6k</span>
+      <span>2.6k</span>
     </span>
     <span class="post-meta-item" title="阅读时长">
       <span class="post-meta-item-icon">
         <i class="far fa-clock"></i>
       </span>
       <span class="post-meta-item-text">阅读时长 &asymp;</span>
-      <span>12 分钟</span>
+      <span>9 分钟</span>
     </span>
 </div>
 
@@ -889,10 +889,10 @@ <h2 class="post-title" itemprop="name headline">
     
     
     <div class="post-body" itemprop="articleBody">
-          <p><code>Import</code> 注解是 <code>Spring</code> 基于 <code>Java</code> 注解配置的重要组成部分，处理 <code>Import</code> 注解是处理 <code>Configuration</code> 注解的子过程之一，本文将介绍 <code>Import</code> 注解的 <code>3</code> 种使用方式，然后通过分析源码和处理过程示意图解释它是如何导入（注册） <code>BeanDefinition</code> 的。</p>
+          <p>如果你正在参与一个共享库的开发，你可能会想为使用方提供自动配置的支持，以帮助对方快速地接入和使用。自动配置机制往往和 <code>starter</code> 联系在一起，本文将介绍如何创建一个自定义的 <code>starter</code> 并从源码角度分析 <code>Spring Boot</code> 自动配置的工作原理。</p>
           <!--noindex-->
             <div class="post-button">
-              <a class="btn" href="/2023/12/04/use-and-analysis-of-Import-annotation-in-Spring/#more" rel="contents">
+              <a class="btn" href="/2023/12/06/custom-starter-and-auto-configuration-in-Spring-Boot/#more" rel="contents">
                 阅读全文 &raquo;
               </a>
             </div>
@@ -923,7 +923,7 @@ <h2 class="post-title" itemprop="name headline">
   
 
   <article itemscope itemtype="http://schema.org/Article" class="post-content" lang="">
-    <link itemprop="mainEntityOfPage" href="https://www.moralok.com/2023/12/02/rotating-nginx-logs-in-docker-container-with-logrotate/">
+    <link itemprop="mainEntityOfPage" href="https://www.moralok.com/2023/12/04/use-and-analysis-of-Import-annotation-in-Spring/">
 
     <span hidden itemprop="author" itemscope itemtype="http://schema.org/Person">
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@@ -941,7 +941,7 @@ <h2 class="post-title" itemprop="name headline">
     </span>
       <header class="post-header">
         <h2 class="post-title" itemprop="name headline">
-          <a href="/2023/12/02/rotating-nginx-logs-in-docker-container-with-logrotate/" class="post-title-link" itemprop="url">使用 logrotate 滚动 Docker 容器内的 Nginx 的日志</a>
+          <a href="/2023/12/04/use-and-analysis-of-Import-annotation-in-Spring/" class="post-title-link" itemprop="url">Spring 中 @Import 注解的使用和源码分析</a>
         </h2>
 
         <div class="post-meta-container">
@@ -952,18 +952,18 @@ <h2 class="post-title" itemprop="name headline">
       </span>
       <span class="post-meta-item-text">发表于</span>
 
-      <time title="创建时间：2023-12-02 13:26:20" itemprop="dateCreated datePublished" datetime="2023-12-02T13:26:20+08:00">2023-12-02</time>
+      <time title="创建时间：2023-12-04 08:36:21" itemprop="dateCreated datePublished" datetime="2023-12-04T08:36:21+08:00">2023-12-04</time>
     </span>
     <span class="post-meta-item">
       <span class="post-meta-item-icon">
         <i class="far fa-calendar-check"></i>
       </span>
       <span class="post-meta-item-text">更新于</span>
-      <time title="修改时间：2024-04-10 22:49:47" itemprop="dateModified" datetime="2024-04-10T22:49:47+08:00">2024-04-10</time>
+      <time title="修改时间：2024-04-24 02:42:37" itemprop="dateModified" datetime="2024-04-24T02:42:37+08:00">2024-04-24</time>
     </span>
 
   
-    <span id="/2023/12/02/rotating-nginx-logs-in-docker-container-with-logrotate/" class="post-meta-item leancloud_visitors" data-flag-title="使用 logrotate 滚动 Docker 容器内的 Nginx 的日志" title="阅读次数">
+    <span id="/2023/12/04/use-and-analysis-of-Import-annotation-in-Spring/" class="post-meta-item leancloud_visitors" data-flag-title="Spring 中 @Import 注解的使用和源码分析" title="阅读次数">
       <span class="post-meta-item-icon">
         <i class="far fa-eye"></i>
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@@ -976,7 +976,7 @@ <h2 class="post-title" itemprop="name headline">
         <i class="far fa-file-word"></i>
       </span>
       <span class="post-meta-item-text">本文字数：</span>
-      <span>3.7k</span>
+      <span>3.6k</span>
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@@ -994,10 +994,10 @@ <h2 class="post-title" itemprop="name headline">
     
     
     <div class="post-body" itemprop="articleBody">
-          <p><code>Nginx</code> 没有提供开箱即用的日志滚动功能，而是将其交给使用者自己实现。你既可以按照官方文档的建议通过编写脚本实现，也可以使用 <code>logrotate</code> 管理日志。但是和在普通场景下不同，在使用 <code>Docker</code> 运行 <code>Nginx</code> 时，你可能需要额外考虑一点细节。本文记录了在为 <code>Docker</code> 中的 <code>Nginx</code> 的日志文件配置滚动功能过程中遇到的一些问题和思考。</p>
+          <p><code>Import</code> 注解是 <code>Spring</code> 基于 <code>Java</code> 注解配置的重要组成部分，处理 <code>Import</code> 注解是处理 <code>Configuration</code> 注解的子过程之一，本文将介绍 <code>Import</code> 注解的 <code>3</code> 种使用方式，然后通过分析源码和处理过程示意图解释它是如何导入（注册） <code>BeanDefinition</code> 的。</p>
           <!--noindex-->
             <div class="post-button">
-              <a class="btn" href="/2023/12/02/rotating-nginx-logs-in-docker-container-with-logrotate/#more" rel="contents">
+              <a class="btn" href="/2023/12/04/use-and-analysis-of-Import-annotation-in-Spring/#more" rel="contents">
                 阅读全文 &raquo;
               </a>
             </div>
@@ -1028,7 +1028,7 @@ <h2 class="post-title" itemprop="name headline">
   
 
   <article itemscope itemtype="http://schema.org/Article" class="post-content" lang="">
-    <link itemprop="mainEntityOfPage" href="https://www.moralok.com/2023/12/01/Nginx-reverse-proxy-for-home-networks/">
+    <link itemprop="mainEntityOfPage" href="https://www.moralok.com/2023/12/02/rotating-nginx-logs-in-docker-container-with-logrotate/">
 
     <span hidden itemprop="author" itemscope itemtype="http://schema.org/Person">
       <meta itemprop="image" content="/images/avatar.gif">
@@ -1046,7 +1046,7 @@ <h2 class="post-title" itemprop="name headline">
     </span>
       <header class="post-header">
         <h2 class="post-title" itemprop="name headline">
-          <a href="/2023/12/01/Nginx-reverse-proxy-for-home-networks/" class="post-title-link" itemprop="url">Nginx 反向代理在家庭网络中的应用</a>
+          <a href="/2023/12/02/rotating-nginx-logs-in-docker-container-with-logrotate/" class="post-title-link" itemprop="url">使用 logrotate 滚动 Docker 容器内的 Nginx 的日志</a>
         </h2>
 
         <div class="post-meta-container">
@@ -1057,18 +1057,18 @@ <h2 class="post-title" itemprop="name headline">
       </span>
       <span class="post-meta-item-text">发表于</span>
 
-      <time title="创建时间：2023-12-01 10:31:05" itemprop="dateCreated datePublished" datetime="2023-12-01T10:31:05+08:00">2023-12-01</time>
+      <time title="创建时间：2023-12-02 13:26:20" itemprop="dateCreated datePublished" datetime="2023-12-02T13:26:20+08:00">2023-12-02</time>
     </span>
     <span class="post-meta-item">
       <span class="post-meta-item-icon">
         <i class="far fa-calendar-check"></i>
       </span>
       <span class="post-meta-item-text">更新于</span>
-      <time title="修改时间：2024-04-10 22:49:47" itemprop="dateModified" datetime="2024-04-10T22:49:47+08:00">2024-04-10</time>
+      <time title="修改时间：2024-04-24 02:42:37" itemprop="dateModified" datetime="2024-04-24T02:42:37+08:00">2024-04-24</time>
     </span>
 
   
-    <span id="/2023/12/01/Nginx-reverse-proxy-for-home-networks/" class="post-meta-item leancloud_visitors" data-flag-title="Nginx 反向代理在家庭网络中的应用" title="阅读次数">
+    <span id="/2023/12/02/rotating-nginx-logs-in-docker-container-with-logrotate/" class="post-meta-item leancloud_visitors" data-flag-title="使用 logrotate 滚动 Docker 容器内的 Nginx 的日志" title="阅读次数">
       <span class="post-meta-item-icon">
         <i class="far fa-eye"></i>
       </span>
@@ -1081,14 +1081,14 @@ <h2 class="post-title" itemprop="name headline">
         <i class="far fa-file-word"></i>
       </span>
       <span class="post-meta-item-text">本文字数：</span>
-      <span>1.1k</span>
+      <span>3.7k</span>
     </span>
     <span class="post-meta-item" title="阅读时长">
       <span class="post-meta-item-icon">
         <i class="far fa-clock"></i>
       </span>
       <span class="post-meta-item-text">阅读时长 &asymp;</span>
-      <span>4 分钟</span>
+      <span>12 分钟</span>
     </span>
 </div>
 
@@ -1099,10 +1099,10 @@ <h2 class="post-title" itemprop="name headline">
     
     
     <div class="post-body" itemprop="articleBody">
-          <p>原先在使用 <code>Cloudflare Tunnel</code> 访问家庭网络中的服务时，是直接将域名解析到相应服务。尽管 <code>Cloudflare</code> 已经提供相关的请求统计和安全防护功能，部分服务自身也有访问日志，但是为了更好地监控和跟踪对外服务的使用情况，采集 <code>Cloudlfare</code> 统计中缺少的新，决定使用 <code>Nginx</code> 反向代理内部服务，统一内部服务的访问入口。简而言之就是，又折腾一些有的没的。以上修改带来的一个附加好处是在局域网内访问服务时，通过在 <code>hosts</code> 文件中添加域名映射，可以用更加容易记忆的域名代替 <code>IP + port</code> 的形式去访问。</p>
+          <p><code>Nginx</code> 没有提供开箱即用的日志滚动功能，而是将其交给使用者自己实现。你既可以按照官方文档的建议通过编写脚本实现，也可以使用 <code>logrotate</code> 管理日志。但是和在普通场景下不同，在使用 <code>Docker</code> 运行 <code>Nginx</code> 时，你可能需要额外考虑一点细节。本文记录了在为 <code>Docker</code> 中的 <code>Nginx</code> 的日志文件配置滚动功能过程中遇到的一些问题和思考。</p>
           <!--noindex-->
             <div class="post-button">
-              <a class="btn" href="/2023/12/01/Nginx-reverse-proxy-for-home-networks/#more" rel="contents">
+              <a class="btn" href="/2023/12/02/rotating-nginx-logs-in-docker-container-with-logrotate/#more" rel="contents">
                 阅读全文 &raquo;
               </a>
             </div>
@@ -1133,7 +1133,7 @@ <h2 class="post-title" itemprop="name headline">
   
 
   <article itemscope itemtype="http://schema.org/Article" class="post-content" lang="">
-    <link itemprop="mainEntityOfPage" href="https://www.moralok.com/2023/11/29/how-does-Dubbo-SPI-adaptive-extension-works/">
+    <link itemprop="mainEntityOfPage" href="https://www.moralok.com/2023/12/01/Nginx-reverse-proxy-for-home-networks/">
 
     <span hidden itemprop="author" itemscope itemtype="http://schema.org/Person">
       <meta itemprop="image" content="/images/avatar.gif">
@@ -1151,7 +1151,7 @@ <h2 class="post-title" itemprop="name headline">
     </span>
       <header class="post-header">
         <h2 class="post-title" itemprop="name headline">
-          <a href="/2023/11/29/how-does-Dubbo-SPI-adaptive-extension-works/" class="post-title-link" itemprop="url">Dubbo SPI 自适应拓展的工作原理</a>
+          <a href="/2023/12/01/Nginx-reverse-proxy-for-home-networks/" class="post-title-link" itemprop="url">Nginx 反向代理在家庭网络中的应用</a>
         </h2>
 
         <div class="post-meta-container">
@@ -1162,18 +1162,18 @@ <h2 class="post-title" itemprop="name headline">
       </span>
       <span class="post-meta-item-text">发表于</span>
 
-      <time title="创建时间：2023-11-29 13:40:07" itemprop="dateCreated datePublished" datetime="2023-11-29T13:40:07+08:00">2023-11-29</time>
+      <time title="创建时间：2023-12-01 10:31:05" itemprop="dateCreated datePublished" datetime="2023-12-01T10:31:05+08:00">2023-12-01</time>
     </span>
     <span class="post-meta-item">
       <span class="post-meta-item-icon">
         <i class="far fa-calendar-check"></i>
       </span>
       <span class="post-meta-item-text">更新于</span>
-      <time title="修改时间：2024-04-10 22:49:47" itemprop="dateModified" datetime="2024-04-10T22:49:47+08:00">2024-04-10</time>
+      <time title="修改时间：2024-04-24 02:42:37" itemprop="dateModified" datetime="2024-04-24T02:42:37+08:00">2024-04-24</time>
     </span>
 
   
-    <span id="/2023/11/29/how-does-Dubbo-SPI-adaptive-extension-works/" class="post-meta-item leancloud_visitors" data-flag-title="Dubbo SPI 自适应拓展的工作原理" title="阅读次数">
+    <span id="/2023/12/01/Nginx-reverse-proxy-for-home-networks/" class="post-meta-item leancloud_visitors" data-flag-title="Nginx 反向代理在家庭网络中的应用" title="阅读次数">
       <span class="post-meta-item-icon">
         <i class="far fa-eye"></i>
       </span>
@@ -1186,14 +1186,14 @@ <h2 class="post-title" itemprop="name headline">
         <i class="far fa-file-word"></i>
       </span>
       <span class="post-meta-item-text">本文字数：</span>
-      <span>5.4k</span>
+      <span>1.1k</span>
     </span>
     <span class="post-meta-item" title="阅读时长">
       <span class="post-meta-item-icon">
         <i class="far fa-clock"></i>
       </span>
       <span class="post-meta-item-text">阅读时长 &asymp;</span>
-      <span>18 分钟</span>
+      <span>4 分钟</span>
     </span>
 </div>
 
@@ -1204,10 +1204,10 @@ <h2 class="post-title" itemprop="name headline">
     
     
     <div class="post-body" itemprop="articleBody">
-          <p>直接展示一个具体的 <code>Dubbo SPI</code> 自适应拓展是什么样子，是一种非常好的表现其作用的方式。正如官方博客中所说的，它让人对自适应拓展有更加感性的认识，避免读者一开始就陷入复杂的代码生成逻辑。本文在此基础上，从更原始的使用方式上展现“动态加载”技术对“按需加载”的天然倾向，从更普遍的角度解释自适应拓展的本质目的，在介绍 <code>Dubbo</code> 的具体实现是如何约束自身从而规避缺点之后，详细梳理了 <code>Dubbo SPI</code> 自适应拓展的相关源码和工作原理。</p>
+          <p>原先在使用 <code>Cloudflare Tunnel</code> 访问家庭网络中的服务时，是直接将域名解析到相应服务。尽管 <code>Cloudflare</code> 已经提供相关的请求统计和安全防护功能，部分服务自身也有访问日志，但是为了更好地监控和跟踪对外服务的使用情况，采集 <code>Cloudlfare</code> 统计中缺少的新，决定使用 <code>Nginx</code> 反向代理内部服务，统一内部服务的访问入口。简而言之就是，又折腾一些有的没的。以上修改带来的一个附加好处是在局域网内访问服务时，通过在 <code>hosts</code> 文件中添加域名映射，可以用更加容易记忆的域名代替 <code>IP + port</code> 的形式去访问。</p>
           <!--noindex-->
             <div class="post-button">
-              <a class="btn" href="/2023/11/29/how-does-Dubbo-SPI-adaptive-extension-works/#more" rel="contents">
+              <a class="btn" href="/2023/12/01/Nginx-reverse-proxy-for-home-networks/#more" rel="contents">
                 阅读全文 &raquo;
               </a>
             </div>
@@ -1253,13 +1253,13 @@ <h2 class="post-title" itemprop="name headline">
     <span class="post-meta-item-icon">
       <i class="fa fa-chart-line"></i>
     </span>
-    <span title="站点总字数">125k</span>
+    <span title="站点总字数">129k</span>
   </span>
   <span class="post-meta-item">
     <span class="post-meta-item-icon">
       <i class="fa fa-coffee"></i>
     </span>
-    <span title="站点阅读时长">6:56</span>
+    <span title="站点阅读时长">7:09</span>
   </span>
 </div>
   <div class="powered-by">由 <a href="https://hexo.io/" rel="noopener" target="_blank">Hexo</a> & <a href="https://theme-next.js.org/" rel="noopener" target="_blank">NexT.Gemini</a> 强力驱动
diff --git a/page/3/index.html b/page/3/index.html
index 7eeebe23..777c269d 100644
--- a/page/3/index.html
+++ b/page/3/index.html
@@ -151,7 +151,7 @@ <h1 class="site-title">Moralok</h1>
   <nav class="site-state">
       <div class="site-state-item site-state-posts">
         <a href="/archives/">
-          <span class="site-state-item-count">48</span>
+          <span class="site-state-item-count">49</span>
           <span class="site-state-item-name">日志</span>
         </a>
       </div>
@@ -183,6 +183,111 @@ <h1 class="site-title">Moralok</h1>
     
 
 
+<div class="post-block">
+  
+  
+
+  <article itemscope itemtype="http://schema.org/Article" class="post-content" lang="">
+    <link itemprop="mainEntityOfPage" href="https://www.moralok.com/2023/11/29/how-does-Dubbo-SPI-adaptive-extension-works/">
+
+    <span hidden itemprop="author" itemscope itemtype="http://schema.org/Person">
+      <meta itemprop="image" content="/images/avatar.gif">
+      <meta itemprop="name" content="Moralok">
+    </span>
+
+    <span hidden itemprop="publisher" itemscope itemtype="http://schema.org/Organization">
+      <meta itemprop="name" content="Moralok">
+      <meta itemprop="description" content="假如生命只剩一天">
+    </span>
+
+    <span hidden itemprop="post" itemscope itemtype="http://schema.org/CreativeWork">
+      <meta itemprop="name" content="undefined | Moralok">
+      <meta itemprop="description" content="">
+    </span>
+      <header class="post-header">
+        <h2 class="post-title" itemprop="name headline">
+          <a href="/2023/11/29/how-does-Dubbo-SPI-adaptive-extension-works/" class="post-title-link" itemprop="url">Dubbo SPI 自适应拓展的工作原理</a>
+        </h2>
+
+        <div class="post-meta-container">
+          <div class="post-meta">
+    <span class="post-meta-item">
+      <span class="post-meta-item-icon">
+        <i class="far fa-calendar"></i>
+      </span>
+      <span class="post-meta-item-text">发表于</span>
+
+      <time title="创建时间：2023-11-29 13:40:07" itemprop="dateCreated datePublished" datetime="2023-11-29T13:40:07+08:00">2023-11-29</time>
+    </span>
+    <span class="post-meta-item">
+      <span class="post-meta-item-icon">
+        <i class="far fa-calendar-check"></i>
+      </span>
+      <span class="post-meta-item-text">更新于</span>
+      <time title="修改时间：2024-04-24 02:42:37" itemprop="dateModified" datetime="2024-04-24T02:42:37+08:00">2024-04-24</time>
+    </span>
+
+  
+    <span id="/2023/11/29/how-does-Dubbo-SPI-adaptive-extension-works/" class="post-meta-item leancloud_visitors" data-flag-title="Dubbo SPI 自适应拓展的工作原理" title="阅读次数">
+      <span class="post-meta-item-icon">
+        <i class="far fa-eye"></i>
+      </span>
+      <span class="post-meta-item-text">阅读次数：</span>
+      <span class="leancloud-visitors-count"></span>
+    </span>
+    <span class="post-meta-break"></span>
+    <span class="post-meta-item" title="本文字数">
+      <span class="post-meta-item-icon">
+        <i class="far fa-file-word"></i>
+      </span>
+      <span class="post-meta-item-text">本文字数：</span>
+      <span>5.4k</span>
+    </span>
+    <span class="post-meta-item" title="阅读时长">
+      <span class="post-meta-item-icon">
+        <i class="far fa-clock"></i>
+      </span>
+      <span class="post-meta-item-text">阅读时长 &asymp;</span>
+      <span>18 分钟</span>
+    </span>
+</div>
+
+        </div>
+      </header>
+
+    
+    
+    
+    <div class="post-body" itemprop="articleBody">
+          <p>直接展示一个具体的 <code>Dubbo SPI</code> 自适应拓展是什么样子，是一种非常好的表现其作用的方式。正如官方博客中所说的，它让人对自适应拓展有更加感性的认识，避免读者一开始就陷入复杂的代码生成逻辑。本文在此基础上，从更原始的使用方式上展现“动态加载”技术对“按需加载”的天然倾向，从更普遍的角度解释自适应拓展的本质目的，在介绍 <code>Dubbo</code> 的具体实现是如何约束自身从而规避缺点之后，详细梳理了 <code>Dubbo SPI</code> 自适应拓展的相关源码和工作原理。</p>
+          <!--noindex-->
+            <div class="post-button">
+              <a class="btn" href="/2023/11/29/how-does-Dubbo-SPI-adaptive-extension-works/#more" rel="contents">
+                阅读全文 &raquo;
+              </a>
+            </div>
+          <!--/noindex-->
+        
+      
+    </div>
+
+    
+    
+    
+
+    <footer class="post-footer">
+        <div class="post-eof"></div>
+      
+    </footer>
+  </article>
+</div>
+
+
+
+
+    
+
+
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@@ -224,7 +329,7 @@ <h2 class="post-title" itemprop="name headline">
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-      <time title="修改时间：2024-04-10 22:49:47" itemprop="dateModified" datetime="2024-04-10T22:49:47+08:00">2024-04-10</time>
+      <time title="修改时间：2024-04-24 02:42:37" itemprop="dateModified" datetime="2024-04-24T02:42:37+08:00">2024-04-24</time>
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@@ -329,7 +434,7 @@ <h2 class="post-title" itemprop="name headline">
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-      <time title="修改时间：2024-04-10 22:49:47" itemprop="dateModified" datetime="2024-04-10T22:49:47+08:00">2024-04-10</time>
+      <time title="修改时间：2024-04-24 02:42:37" itemprop="dateModified" datetime="2024-04-24T02:42:37+08:00">2024-04-24</time>
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@@ -434,7 +539,7 @@ <h2 class="post-title" itemprop="name headline">
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-      <time title="修改时间：2024-04-10 22:49:47" itemprop="dateModified" datetime="2024-04-10T22:49:47+08:00">2024-04-10</time>
+      <time title="修改时间：2024-04-24 02:42:37" itemprop="dateModified" datetime="2024-04-24T02:42:37+08:00">2024-04-24</time>
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@@ -539,7 +644,7 @@ <h2 class="post-title" itemprop="name headline">
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-      <time title="修改时间：2024-04-10 22:49:47" itemprop="dateModified" datetime="2024-04-10T22:49:47+08:00">2024-04-10</time>
+      <time title="修改时间：2024-04-24 02:42:37" itemprop="dateModified" datetime="2024-04-24T02:42:37+08:00">2024-04-24</time>
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@@ -767,7 +872,7 @@ <h2 class="post-title" itemprop="name headline">
         <i class="far fa-calendar-check"></i>
       </span>
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-      <time title="修改时间：2024-04-10 22:49:47" itemprop="dateModified" datetime="2024-04-10T22:49:47+08:00">2024-04-10</time>
+      <time title="修改时间：2024-04-24 02:42:37" itemprop="dateModified" datetime="2024-04-24T02:42:37+08:00">2024-04-24</time>
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@@ -969,7 +1074,7 @@ <h2 class="post-title" itemprop="name headline">
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-      <time title="修改时间：2024-04-10 22:49:47" itemprop="dateModified" datetime="2024-04-10T22:49:47+08:00">2024-04-10</time>
+      <time title="修改时间：2024-04-24 02:42:37" itemprop="dateModified" datetime="2024-04-24T02:42:37+08:00">2024-04-24</time>
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@@ -1074,7 +1179,7 @@ <h2 class="post-title" itemprop="name headline">
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-      <time title="修改时间：2024-04-10 22:49:47" itemprop="dateModified" datetime="2024-04-10T22:49:47+08:00">2024-04-10</time>
+      <time title="修改时间：2024-04-24 02:42:37" itemprop="dateModified" datetime="2024-04-24T02:42:37+08:00">2024-04-24</time>
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@@ -1228,7 +1333,7 @@ <h2 class="post-title" itemprop="name headline">
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-      <time title="修改时间：2024-04-10 22:49:47" itemprop="dateModified" datetime="2024-04-10T22:49:47+08:00">2024-04-10</time>
+      <time title="修改时间：2024-04-24 02:42:37" itemprop="dateModified" datetime="2024-04-24T02:42:37+08:00">2024-04-24</time>
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@@ -1396,7 +1501,7 @@ <h2 class="post-title" itemprop="name headline">
         <i class="far fa-calendar-check"></i>
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-      <time title="修改时间：2024-04-10 22:49:47" itemprop="dateModified" datetime="2024-04-10T22:49:47+08:00">2024-04-10</time>
+      <time title="修改时间：2024-04-24 02:42:37" itemprop="dateModified" datetime="2024-04-24T02:42:37+08:00">2024-04-24</time>
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@@ -1785,239 +1890,6 @@ <h2 id="参考文章"><a href="#参考文章" class="headerlink" title="参考
 
 
 
-    
-
-
-<div class="post-block">
-  
-  
-
-  <article itemscope itemtype="http://schema.org/Article" class="post-content" lang="">
-    <link itemprop="mainEntityOfPage" href="https://www.moralok.com/2023/11/04/testing-and-analysis-of-jvm-memory-area/">
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-      <meta itemprop="image" content="/images/avatar.gif">
-      <meta itemprop="name" content="Moralok">
-    </span>
-
-    <span hidden itemprop="publisher" itemscope itemtype="http://schema.org/Organization">
-      <meta itemprop="name" content="Moralok">
-      <meta itemprop="description" content="假如生命只剩一天">
-    </span>
-
-    <span hidden itemprop="post" itemscope itemtype="http://schema.org/CreativeWork">
-      <meta itemprop="name" content="undefined | Moralok">
-      <meta itemprop="description" content="">
-    </span>
-      <header class="post-header">
-        <h2 class="post-title" itemprop="name headline">
-          <a href="/2023/11/04/testing-and-analysis-of-jvm-memory-area/" class="post-title-link" itemprop="url">JVM 内存区域的测试和分析</a>
-        </h2>
-
-        <div class="post-meta-container">
-          <div class="post-meta">
-    <span class="post-meta-item">
-      <span class="post-meta-item-icon">
-        <i class="far fa-calendar"></i>
-      </span>
-      <span class="post-meta-item-text">发表于</span>
-
-      <time title="创建时间：2023-11-04 19:21:25" itemprop="dateCreated datePublished" datetime="2023-11-04T19:21:25+08:00">2023-11-04</time>
-    </span>
-    <span class="post-meta-item">
-      <span class="post-meta-item-icon">
-        <i class="far fa-calendar-check"></i>
-      </span>
-      <span class="post-meta-item-text">更新于</span>
-      <time title="修改时间：2024-04-10 22:49:47" itemprop="dateModified" datetime="2024-04-10T22:49:47+08:00">2024-04-10</time>
-    </span>
-
-  
-    <span id="/2023/11/04/testing-and-analysis-of-jvm-memory-area/" class="post-meta-item leancloud_visitors" data-flag-title="JVM 内存区域的测试和分析" title="阅读次数">
-      <span class="post-meta-item-icon">
-        <i class="far fa-eye"></i>
-      </span>
-      <span class="post-meta-item-text">阅读次数：</span>
-      <span class="leancloud-visitors-count"></span>
-    </span>
-    <span class="post-meta-break"></span>
-    <span class="post-meta-item" title="本文字数">
-      <span class="post-meta-item-icon">
-        <i class="far fa-file-word"></i>
-      </span>
-      <span class="post-meta-item-text">本文字数：</span>
-      <span>3.2k</span>
-    </span>
-    <span class="post-meta-item" title="阅读时长">
-      <span class="post-meta-item-icon">
-        <i class="far fa-clock"></i>
-      </span>
-      <span class="post-meta-item-text">阅读时长 &asymp;</span>
-      <span>11 分钟</span>
-    </span>
-</div>
-
-        </div>
-      </header>
-
-    
-    
-    
-    <div class="post-body" itemprop="articleBody">
-          <h2 id="内存区域"><a href="#内存区域" class="headerlink" title="内存区域"></a>内存区域</h2><p>JVM 内存区域划分为：</p>
-<ul>
-<li>程序计数器</li>
-<li>虚拟机栈</li>
-<li>本地方法栈</li>
-<li>堆</li>
-<li>方法区</li>
-</ul>
-<img src="/2023/11/04/testing-and-analysis-of-jvm-memory-area/Pasted%20image%2020231102215652.png" class="" title="内存区域划分">
-
-<h2 id="程序计数器"><a href="#程序计数器" class="headerlink" title="程序计数器"></a>程序计数器</h2><h2 id="虚拟机栈"><a href="#虚拟机栈" class="headerlink" title="虚拟机栈"></a>虚拟机栈</h2><p>Java 虚拟机栈（Java Virtual Machine Stack），线程私有，生命周期与线程相同。虚拟机栈描述的是 Java 方法执行的线程内存模型。每个方法被执行的时候，Java虚拟机都会同步创建一个栈帧（Stack Frame）用于存储局部变量表、操作数栈、动态连接、方法出口等信息。</p>
-<p>可以使用 <code>-Xss1024k</code> 设置虚拟机栈的大小。默认情况下都是 1024k，只有 Windows 中取决于虚拟内存。</p>
-<h3 id="栈内存溢出"><a href="#栈内存溢出" class="headerlink" title="栈内存溢出"></a>栈内存溢出</h3><ol>
-<li>栈帧过多导致栈内存溢出</li>
-<li>栈帧过大导致栈内存溢出（难复现）</li>
-</ol>
-<h4 id="不正确的递归调用"><a href="#不正确的递归调用" class="headerlink" title="不正确的递归调用"></a>不正确的递归调用</h4><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">class</span> <span class="title class_">StackTest_4</span> &#123;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">static</span> <span class="type">int</span> <span class="variable">count</span> <span class="operator">=</span> <span class="number">0</span>;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 改变栈的大小限制 -Xss256k，观察调用次数的变化</span></span><br><span class="line">    <span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">main</span><span class="params">(String[] args)</span> &#123;</span><br><span class="line">        <span class="keyword">try</span> &#123;</span><br><span class="line">            method1();</span><br><span class="line">        &#125; <span class="keyword">catch</span> (Throwable t) &#123;</span><br><span class="line">            t.printStackTrace();</span><br><span class="line">        &#125; <span class="keyword">finally</span> &#123;</span><br><span class="line">            <span class="comment">// 默认情况下经过 20000+ 次，改变参数后 3000+ 次</span></span><br><span class="line">            System.out.println(count);</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">method1</span><span class="params">()</span> &#123;</span><br><span class="line">        count++;</span><br><span class="line">        method1();</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
-
-
-<h4 id="循环引用导致-JSON-解析无限循环"><a href="#循环引用导致-JSON-解析无限循环" class="headerlink" title="循环引用导致 JSON 解析无限循环"></a>循环引用导致 JSON 解析无限循环</h4><p>并非只有自己写的递归方法可能引发栈内存溢出，有可能第三方库也会引发栈内存溢出。</p>
-<figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br><span class="line">46</span><br><span class="line">47</span><br><span class="line">48</span><br><span class="line">49</span><br><span class="line">50</span><br><span class="line">51</span><br><span class="line">52</span><br><span class="line">53</span><br><span class="line">54</span><br><span class="line">55</span><br><span class="line">56</span><br><span class="line">57</span><br><span class="line">58</span><br><span class="line">59</span><br><span class="line">60</span><br><span class="line">61</span><br><span class="line">62</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">class</span> <span class="title class_">StackTest_5</span> &#123;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">main</span><span class="params">(String[] args)</span> <span class="keyword">throws</span> JsonProcessingException &#123;</span><br><span class="line">        <span class="type">Department</span> <span class="variable">department</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">Department</span>();</span><br><span class="line">        department.setName(<span class="string">&quot;Tech&quot;</span>);</span><br><span class="line"></span><br><span class="line">        <span class="type">Employee</span> <span class="variable">employee1</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">Employee</span>();</span><br><span class="line">        employee1.setName(<span class="string">&quot;Tom&quot;</span>);</span><br><span class="line">        employee1.setDepartment(department);</span><br><span class="line"></span><br><span class="line">        <span class="type">Employee</span> <span class="variable">employee2</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">Employee</span>();</span><br><span class="line">        employee2.setName(<span class="string">&quot;Tim&quot;</span>);</span><br><span class="line">        employee2.setDepartment(department);</span><br><span class="line"></span><br><span class="line">        department.setEmployees(Arrays.asList(employee1, employee2));</span><br><span class="line"></span><br><span class="line">        <span class="type">ObjectMapper</span> <span class="variable">objectMapper</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">ObjectMapper</span>();</span><br><span class="line">        System.out.println(objectMapper.writeValueAsString(department));</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">static</span> <span class="keyword">class</span> <span class="title class_">Department</span> &#123;</span><br><span class="line">        <span class="keyword">private</span> String name;</span><br><span class="line">        <span class="keyword">private</span> List&lt;Employee&gt; employees;</span><br><span class="line"></span><br><span class="line">        <span class="keyword">public</span> String <span class="title function_">getName</span><span class="params">()</span> &#123;</span><br><span class="line">            <span class="keyword">return</span> name;</span><br><span class="line">        &#125;</span><br><span class="line"></span><br><span class="line">        <span class="keyword">public</span> <span class="keyword">void</span> <span class="title function_">setName</span><span class="params">(String name)</span> &#123;</span><br><span class="line">            <span class="built_in">this</span>.name = name;</span><br><span class="line">        &#125;</span><br><span class="line"></span><br><span class="line">        <span class="keyword">public</span> List&lt;Employee&gt; <span class="title function_">getEmployees</span><span class="params">()</span> &#123;</span><br><span class="line">            <span class="keyword">return</span> employees;</span><br><span class="line">        &#125;</span><br><span class="line"></span><br><span class="line">        <span class="keyword">public</span> <span class="keyword">void</span> <span class="title function_">setEmployees</span><span class="params">(List&lt;Employee&gt; employees)</span> &#123;</span><br><span class="line">            <span class="built_in">this</span>.employees = employees;</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">static</span> <span class="keyword">class</span> <span class="title class_">Employee</span> &#123;</span><br><span class="line">        <span class="keyword">private</span> String name;</span><br><span class="line">        <span class="keyword">private</span> Department department;</span><br><span class="line"></span><br><span class="line">        <span class="keyword">public</span> String <span class="title function_">getName</span><span class="params">()</span> &#123;</span><br><span class="line">            <span class="keyword">return</span> name;</span><br><span class="line">        &#125;</span><br><span class="line"></span><br><span class="line">        <span class="keyword">public</span> <span class="keyword">void</span> <span class="title function_">setName</span><span class="params">(String name)</span> &#123;</span><br><span class="line">            <span class="built_in">this</span>.name = name;</span><br><span class="line">        &#125;</span><br><span class="line"></span><br><span class="line">        <span class="keyword">public</span> Department <span class="title function_">getDepartment</span><span class="params">()</span> &#123;</span><br><span class="line">            <span class="keyword">return</span> department;</span><br><span class="line">        &#125;</span><br><span class="line"></span><br><span class="line">        <span class="keyword">public</span> <span class="keyword">void</span> <span class="title function_">setDepartment</span><span class="params">(Department department)</span> &#123;</span><br><span class="line">            <span class="built_in">this</span>.department = department;</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
-
-<h3 id="局部变量的线程安全问题"><a href="#局部变量的线程安全问题" class="headerlink" title="局部变量的线程安全问题"></a>局部变量的线程安全问题</h3><ol>
-<li>局部变量如果未逃离方法的作用范围，就是线程安全的。</li>
-<li>局部变量如果是引用类型且逃离了方法的作用范围，就是线程不安全的。</li>
-</ol>
-<figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">class</span> <span class="title class_">StackTest_3</span> &#123;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">main</span><span class="params">(String[] args)</span> &#123;</span><br><span class="line">        method1();</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 线程安全</span></span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">method1</span><span class="params">()</span> &#123;</span><br><span class="line">        <span class="type">StringBuilder</span> <span class="variable">sb</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">StringBuilder</span>();</span><br><span class="line">        sb.append(<span class="number">1</span>);</span><br><span class="line">        sb.append(<span class="number">2</span>);</span><br><span class="line">        sb.append(<span class="number">3</span>);</span><br><span class="line">        System.out.println(sb);</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 线程不安全</span></span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">method2</span><span class="params">(StringBuilder sb)</span> &#123;</span><br><span class="line">        sb.append(<span class="number">1</span>);</span><br><span class="line">        sb.append(<span class="number">2</span>);</span><br><span class="line">        sb.append(<span class="number">3</span>);</span><br><span class="line">        System.out.println(sb);</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 线程不安全，看到一个说法：发生指令重排，sb 的 append 操作发生在返回之后（有待确认）</span></span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">static</span> StringBuilder <span class="title function_">method3</span><span class="params">()</span> &#123;</span><br><span class="line">        <span class="type">StringBuilder</span> <span class="variable">sb</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">StringBuilder</span>();</span><br><span class="line">        sb.append(<span class="number">1</span>);</span><br><span class="line">        sb.append(<span class="number">2</span>);</span><br><span class="line">        sb.append(<span class="number">3</span>);</span><br><span class="line">        <span class="keyword">return</span> sb;</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
-
-<h3 id="线程问题排查"><a href="#线程问题排查" class="headerlink" title="线程问题排查"></a>线程问题排查</h3><h4 id="CPU-占用率居高不下"><a href="#CPU-占用率居高不下" class="headerlink" title="CPU 占用率居高不下"></a>CPU 占用率居高不下</h4><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">class</span> <span class="title class_">ThreadTest_1</span> &#123;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">main</span><span class="params">(String[] args)</span> &#123;</span><br><span class="line">        <span class="keyword">new</span> <span class="title class_">Thread</span>(<span class="literal">null</span>, () -&gt; &#123;</span><br><span class="line">            System.out.println(<span class="string">&quot;t1...&quot;</span>);</span><br><span class="line">            <span class="keyword">while</span> (<span class="literal">true</span>) &#123;</span><br><span class="line"></span><br><span class="line">            &#125;</span><br><span class="line">        &#125;, <span class="string">&quot;thread1&quot;</span>).start();</span><br><span class="line"></span><br><span class="line">        <span class="keyword">new</span> <span class="title class_">Thread</span>(<span class="literal">null</span>, () -&gt; &#123;</span><br><span class="line">            System.out.println(<span class="string">&quot;t2...&quot;</span>);</span><br><span class="line">            <span class="keyword">try</span> &#123;</span><br><span class="line">                TimeUnit.SECONDS.sleep(<span class="number">1000</span>);</span><br><span class="line">            &#125; <span class="keyword">catch</span> (InterruptedException e) &#123;</span><br><span class="line">                e.printStackTrace();</span><br><span class="line">            &#125;</span><br><span class="line">        &#125;, <span class="string">&quot;thread2&quot;</span>).start();</span><br><span class="line"></span><br><span class="line">        <span class="keyword">new</span> <span class="title class_">Thread</span>(<span class="literal">null</span>, () -&gt; &#123;</span><br><span class="line">            System.out.println(<span class="string">&quot;t3...&quot;</span>);</span><br><span class="line">            <span class="keyword">try</span> &#123;</span><br><span class="line">                TimeUnit.SECONDS.sleep(<span class="number">1000</span>);</span><br><span class="line">            &#125; <span class="keyword">catch</span> (InterruptedException e) &#123;</span><br><span class="line">                e.printStackTrace();</span><br><span class="line">            &#125;</span><br><span class="line">        &#125;, <span class="string">&quot;thread3&quot;</span>).start();</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
-<p>当发现 CPU 占用率居高不下时，可以尝试以下步骤：</p>
-<ol>
-<li><code>top</code>，定位 cpu 占用高的进程 id。</li>
-<li><code>ps H -eo pid,tid,%cpu | grep pid</code>，进一步定位引起 cpu 占用高的线程 id。</li>
-<li><code>jstack pid</code>，根据线程 id 换算成 16进制的 nid 找到对应线程，进一步定位到问题的源码行号。</li>
-</ol>
-<figure class="highlight console"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br></pre></td><td class="code"><pre><span class="line">&quot;thread1&quot; #8 prio=5 os_prio=0 tid=0x00007f9bd0162800 nid=0x1061ad runnable [0x00007f9bd56eb000]</span><br><span class="line">   java.lang.Thread.State: RUNNABLE</span><br><span class="line">	at com.moralok.jvm.thread.ThreadTest_1.lambda$main$0(ThreadTest_1.java:10)</span><br><span class="line">	at com.moralok.jvm.thread.ThreadTest_1$$Lambda$1/250421012.run(Unknown Source)</span><br><span class="line">	at java.lang.Thread.run(Thread.java:750)</span><br></pre></td></tr></table></figure>
-
-<h4 id="死锁，迟迟未返回结果"><a href="#死锁，迟迟未返回结果" class="headerlink" title="死锁，迟迟未返回结果"></a>死锁，迟迟未返回结果</h4><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">class</span> <span class="title class_">ThreadTest_2</span> &#123;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">static</span> <span class="keyword">final</span> <span class="type">Object</span> <span class="variable">A</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">Object</span>();</span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">static</span> <span class="keyword">final</span> <span class="type">Object</span> <span class="variable">B</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">Object</span>();</span><br><span class="line"></span><br><span class="line">    <span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">main</span><span class="params">(String[] args)</span> &#123;</span><br><span class="line">        <span class="keyword">new</span> <span class="title class_">Thread</span>(<span class="literal">null</span>, () -&gt; &#123;</span><br><span class="line">            System.out.println(<span class="string">&quot;t1...&quot;</span>);</span><br><span class="line">            <span class="keyword">synchronized</span> (A) &#123;</span><br><span class="line">                System.out.println(Thread.currentThread().getName() + <span class="string">&quot; get A&quot;</span>);</span><br><span class="line">                <span class="keyword">try</span> &#123;</span><br><span class="line">                    TimeUnit.SECONDS.sleep(<span class="number">5</span>);</span><br><span class="line">                &#125; <span class="keyword">catch</span> (InterruptedException e) &#123;</span><br><span class="line">                    <span class="keyword">throw</span> <span class="keyword">new</span> <span class="title class_">RuntimeException</span>(e);</span><br><span class="line">                &#125;</span><br><span class="line">                <span class="keyword">synchronized</span> (B) &#123;</span><br><span class="line">                    System.out.println(Thread.currentThread().getName() + <span class="string">&quot; get B&quot;</span>);</span><br><span class="line">                &#125;</span><br><span class="line">            &#125;</span><br><span class="line">        &#125;, <span class="string">&quot;thread1&quot;</span>).start();</span><br><span class="line"></span><br><span class="line">        <span class="keyword">new</span> <span class="title class_">Thread</span>(<span class="literal">null</span>, () -&gt; &#123;</span><br><span class="line">            System.out.println(<span class="string">&quot;t2...&quot;</span>);</span><br><span class="line">            <span class="keyword">synchronized</span> (B) &#123;</span><br><span class="line">                System.out.println(Thread.currentThread().getName() + <span class="string">&quot; get B&quot;</span>);</span><br><span class="line">                <span class="keyword">try</span> &#123;</span><br><span class="line">                    TimeUnit.SECONDS.sleep(<span class="number">5</span>);</span><br><span class="line">                &#125; <span class="keyword">catch</span> (InterruptedException e) &#123;</span><br><span class="line">                    <span class="keyword">throw</span> <span class="keyword">new</span> <span class="title class_">RuntimeException</span>(e);</span><br><span class="line">                &#125;</span><br><span class="line">                <span class="keyword">synchronized</span> (A) &#123;</span><br><span class="line">                    System.out.println(Thread.currentThread().getName() + <span class="string">&quot; get A&quot;</span>);</span><br><span class="line">                &#125;</span><br><span class="line">            &#125;</span><br><span class="line">        &#125;, <span class="string">&quot;thread2&quot;</span>).start();</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
-
-<ol>
-<li><code>jstack pid</code>，会显示找到死锁，以及死锁涉及的线程,，并各自持有的锁还有等待的锁。</li>
-<li>其他工具如 jconsole 也具有检测死锁的功能。</li>
-</ol>
-<h2 id="本地方法栈"><a href="#本地方法栈" class="headerlink" title="本地方法栈"></a>本地方法栈</h2><h2 id="堆"><a href="#堆" class="headerlink" title="堆"></a>堆</h2><p>堆（Heap）的特点：</p>
-<ol>
-<li>线程共享，需要考虑线程安全问题。</li>
-<li>存在垃圾回收机制。</li>
-<li>使用 -Xmx8m 设置大小。</li>
-</ol>
-<h3 id="堆内存溢出"><a href="#堆内存溢出" class="headerlink" title="堆内存溢出"></a>堆内存溢出</h3><p>既然堆有垃圾回收机制，为什么还会发生内存溢出呢？最开始的时候，我也有这样的困惑。<br>后来我才认识到，还在使用中的对象是不能被强制回收的，不再使用的对象不是立刻回收的。当创建对象却没有足够的内存空间时，如果清理掉那些不再使用的对象就有足够的内存空间，就不会发生内存溢出，程序只是表现为卡顿。</p>
-<figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">class</span> <span class="title class_">HeapTest_1</span> &#123;  </span><br><span class="line">  </span><br><span class="line">    <span class="comment">// -Xmx8m  </span></span><br><span class="line">    <span class="comment">// 不设置可能不提示 Java heap space，出错地方不同，报错信息不同  </span></span><br><span class="line">    <span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">main</span><span class="params">(String[] args)</span> &#123;  </span><br><span class="line">        <span class="type">int</span> <span class="variable">i</span> <span class="operator">=</span> <span class="number">0</span>;  </span><br><span class="line">        <span class="keyword">try</span> &#123;  </span><br><span class="line">            List&lt;String&gt; list = <span class="keyword">new</span> <span class="title class_">ArrayList</span>&lt;&gt;();  </span><br><span class="line">            <span class="type">String</span> <span class="variable">s</span> <span class="operator">=</span> <span class="string">&quot;hello&quot;</span>;  </span><br><span class="line">            <span class="keyword">while</span> (<span class="literal">true</span>) &#123;  </span><br><span class="line">                list.add(s);  </span><br><span class="line">                s = s + s;  </span><br><span class="line">                i++;  </span><br><span class="line">            &#125;  </span><br><span class="line">        &#125; <span class="keyword">catch</span> (Throwable t) &#123;  </span><br><span class="line">            t.printStackTrace();  </span><br><span class="line">        &#125; <span class="keyword">finally</span> &#123;  </span><br><span class="line">            System.out.println(<span class="string">&quot;运行次数 &quot;</span> + i);  </span><br><span class="line">        &#125;  </span><br><span class="line">    &#125;  </span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
-
-<figure class="highlight console"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br></pre></td><td class="code"><pre><span class="line">java.lang.OutOfMemoryError: Java heap space</span><br><span class="line">	at java.util.Arrays.copyOf(Arrays.java:3332)</span><br><span class="line">	at java.lang.AbstractStringBuilder.ensureCapacityInternal(AbstractStringBuilder.java:124)</span><br><span class="line">	at java.lang.AbstractStringBuilder.append(AbstractStringBuilder.java:448)</span><br><span class="line">	at java.lang.StringBuilder.append(StringBuilder.java:141)</span><br><span class="line">	at com.moralok.jvm.memory.heap.HeapTest_1.main(HeapTest_1.java:21)</span><br><span class="line">运行次数 17</span><br></pre></td></tr></table></figure>
-
-<p>堆内存溢出的发生往往需要长时间的运行，因此在排查相关问题时，可以适当调小堆内存。</p>
-<h3 id="监测堆内存"><a href="#监测堆内存" class="headerlink" title="监测堆内存"></a>监测堆内存</h3><ol>
-<li>使用 jps 查看 Java 进程列表</li>
-<li>使用 <code>jmap -heap pid</code> 查看堆内存信息</li>
-<li>还可以使用 jconsole 观察堆内存变化曲线</li>
-<li>还可以使用 VisualVM 查看堆信息</li>
-</ol>
-<figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">class</span> <span class="title class_">HeapTest_2</span> &#123;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">main</span><span class="params">(String[] args)</span> <span class="keyword">throws</span> InterruptedException &#123;</span><br><span class="line">        System.out.println(<span class="string">&quot;1...&quot;</span>);</span><br><span class="line">        TimeUnit.SECONDS.sleep(<span class="number">30</span>);</span><br><span class="line">        <span class="comment">// 堆空间占用上升 10MB</span></span><br><span class="line">        <span class="type">byte</span>[] bytes = <span class="keyword">new</span> <span class="title class_">byte</span>[<span class="number">1024</span> * <span class="number">1024</span> * <span class="number">10</span>];</span><br><span class="line">        System.out.println(<span class="string">&quot;2...&quot;</span>);</span><br><span class="line">        TimeUnit.SECONDS.sleep(<span class="number">30</span>);</span><br><span class="line">        bytes = <span class="literal">null</span>;</span><br><span class="line">        <span class="comment">// 堆空间占用下降</span></span><br><span class="line">        System.gc();</span><br><span class="line">        System.out.println(<span class="string">&quot;3...&quot;</span>);</span><br><span class="line">        TimeUnit.SECONDS.sleep(<span class="number">3000</span>);</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
-
-<p>使用 <code>jmap -heap pid</code> 查看堆内存信息：</p>
-<figure class="highlight console"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br></pre></td><td class="code"><pre><span class="line">Eden Space:</span><br><span class="line">   capacity = 268435456 (256.0MB)</span><br><span class="line">   used     = 32212360 (30.72010040283203MB)</span><br><span class="line"></span><br><span class="line">   used     = 42698136 (40.720115661621094MB)</span><br><span class="line"></span><br><span class="line">   used     = 5368728 (5.120018005371094MB)</span><br></pre></td></tr></table></figure>
-
-<p>使用 jconsole 查看堆内存信息：</p>
-<img src="/2023/11/04/testing-and-analysis-of-jvm-memory-area/Pasted%20image%2020231104200411.png" class="" title="jconsole 观察堆内存占用">
-
-<h3 id="堆内存占用居高不下"><a href="#堆内存占用居高不下" class="headerlink" title="堆内存占用居高不下"></a>堆内存占用居高不下</h3><p>当你发现堆内存占用居高不下，经过 GC，下降也不明显，如果你想查看一下堆内的具体情况，可以将其 dump 查看。</p>
-<figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">class</span> <span class="title class_">HeapTest_3</span> &#123;  </span><br><span class="line">  </span><br><span class="line">    <span class="comment">// jps 查进程，jmap 看堆内存，jconsole 执行GC，堆内存占用没有明显下降  </span></span><br><span class="line">    <span class="comment">// 使用 VisualVM 的堆 dump 功能，观察大对象  </span></span><br><span class="line">    <span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">main</span><span class="params">(String[] args)</span> <span class="keyword">throws</span> IOException &#123;  </span><br><span class="line">        List&lt;Student&gt; students = <span class="keyword">new</span> <span class="title class_">ArrayList</span>&lt;&gt;();  </span><br><span class="line">        <span class="keyword">for</span> (<span class="type">int</span> <span class="variable">i</span> <span class="operator">=</span> <span class="number">0</span>; i &lt; <span class="number">200</span>; i++) &#123;  </span><br><span class="line">            students.add(<span class="keyword">new</span> <span class="title class_">Student</span>());  </span><br><span class="line">        &#125;  </span><br><span class="line">        System.in.read();  </span><br><span class="line">    &#125;  </span><br><span class="line">  </span><br><span class="line">    <span class="keyword">static</span> <span class="keyword">class</span> <span class="title class_">Student</span> &#123;  </span><br><span class="line">        <span class="keyword">private</span> <span class="type">byte</span>[] score = <span class="keyword">new</span> <span class="title class_">byte</span>[<span class="number">1024</span> * <span class="number">1024</span>];  </span><br><span class="line">    &#125;  </span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
-<p>可使用 VisualVM 的 Heap Dump 功能：</p>
-<img src="/2023/11/04/testing-and-analysis-of-jvm-memory-area/Pasted%20image%2020231104201139.png" class="" title="VisualVM 观察堆中的大对象">
-
-<p>也可使用 <code>jmap -dump:format=b,file=filename.hprof pid</code>，需要其他分析工具搭配。</p>
-<h2 id="方法区"><a href="#方法区" class="headerlink" title="方法区"></a>方法区</h2><p>根据《Java虚拟机规范》，方法区在逻辑上是堆的一部分，但是在具体实现上，各个虚拟机厂商并不相同。对于 Hotspot 而言：</p>
-<ul>
-<li>JDK 8 之前，方法区的具体实现为永久代，使用堆内存，使用 -XX:MaxPermSize&#x3D;10m 设置大小。</li>
-<li>JDK 8 开始，方法区的具体实现为元空间，使用直接内存，使用 -XX:MaxMetaspaceSize&#x3D;10m 设置大小。</li>
-</ul>
-<h3 id="方法区溢出"><a href="#方法区溢出" class="headerlink" title="方法区溢出"></a>方法区溢出</h3><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">class</span> <span class="title class_">MethodAreaTest_1</span> <span class="keyword">extends</span> <span class="title class_">ClassLoader</span> &#123;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// -XX:MaxMetaspaceSize=8m MaxMetaspaceSize is too small.</span></span><br><span class="line">    <span class="comment">// -XX:MaxMetaspaceSize=10m java.lang.OutOfMemoryError: Compressed class space</span></span><br><span class="line">    <span class="comment">// 不是 Metaspace 应该是某个参数设置的问题</span></span><br><span class="line">    <span class="comment">// JDK 6: -XX:MaxPermSize=8m PermGen space</span></span><br><span class="line">    <span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">main</span><span class="params">(String[] args)</span> &#123;</span><br><span class="line">        <span class="type">int</span> <span class="variable">j</span> <span class="operator">=</span> <span class="number">0</span>;</span><br><span class="line">        <span class="keyword">try</span> &#123;</span><br><span class="line">            <span class="type">MethodAreaTest_1</span> <span class="variable">methodAreaTest1</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">MethodAreaTest_1</span>();</span><br><span class="line">            <span class="keyword">for</span> (<span class="type">int</span> <span class="variable">i</span> <span class="operator">=</span> <span class="number">0</span>; i &lt; <span class="number">20000</span>; i++, j++) &#123;</span><br><span class="line">                <span class="type">ClassWriter</span> <span class="variable">classWriter</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">ClassWriter</span>(<span class="number">0</span>);</span><br><span class="line">                <span class="comment">// 版本号，public，类名，包名，父类，接口</span></span><br><span class="line">                classWriter.visit(Opcodes.V1_8, Opcodes.ACC_PUBLIC, <span class="string">&quot;Class&quot;</span> + i, <span class="literal">null</span>, <span class="string">&quot;java/lang/Object&quot;</span>, <span class="literal">null</span>);</span><br><span class="line">                <span class="comment">// 返回二进制字节码</span></span><br><span class="line">                <span class="type">byte</span>[] code = classWriter.toByteArray();</span><br><span class="line">                <span class="comment">// 加载类</span></span><br><span class="line">                methodAreaTest1.defineClass(<span class="string">&quot;Class&quot;</span> + i, code, <span class="number">0</span>, code.length);</span><br><span class="line">            &#125;</span><br><span class="line">        &#125; <span class="keyword">catch</span> (ClassFormatError e) &#123;</span><br><span class="line">            e.printStackTrace();</span><br><span class="line">        &#125; <span class="keyword">finally</span> &#123;</span><br><span class="line">            System.out.println(<span class="string">&quot;次数 &quot;</span> + j);</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
-<ol>
-<li>当设置的值太小时 -XX:MaxMetaspaceSize&#x3D;8m，提示 MaxMetaspaceSize is too small。</li>
-<li>实验中抛出 java.lang.OutOfMemoryError: Compressed class space。</li>
-<li>添加参数 -XX:-UseCompressedClassPointers 后，抛出 java.lang.OutOfMemoryError: Metaspace。</li>
-<li>JDK 6 设置 -XX:MaxPermSize&#x3D;8m，抛出 java.lang.OutOfMemoryError: PermGen space。</li>
-</ol>
-<p>不要认为自己不会写动态生成字节码相关的代码就忽略这方面的问题，如今很多框架使用字节码技术大量地动态生成类。</p>
-<h2 id="运行时常量池"><a href="#运行时常量池" class="headerlink" title="运行时常量池"></a>运行时常量池</h2><p>二进制字节码文件主要包含三类信息：</p>
-<ol>
-<li>类的基本信息</li>
-<li>类的常量池（Constant Pool）</li>
-<li>类的方法信息</li>
-</ol>
-<h3 id="使用-javap-反编译"><a href="#使用-javap-反编译" class="headerlink" title="使用 javap 反编译"></a>使用 javap 反编译</h3><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">class</span> <span class="title class_">MethodAreaTest_2</span> &#123;  </span><br><span class="line">  </span><br><span class="line">    <span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">main</span><span class="params">(String[] args)</span> &#123;  </span><br><span class="line">        System.out.println(<span class="string">&quot;hello world&quot;</span>);  </span><br><span class="line">    &#125;  </span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
-
-<figure class="highlight console"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br><span class="line">46</span><br><span class="line">47</span><br><span class="line">48</span><br><span class="line">49</span><br><span class="line">50</span><br><span class="line">51</span><br><span class="line">52</span><br><span class="line">53</span><br><span class="line">54</span><br><span class="line">55</span><br><span class="line">56</span><br><span class="line">57</span><br><span class="line">58</span><br><span class="line">59</span><br><span class="line">60</span><br><span class="line">61</span><br><span class="line">62</span><br><span class="line">63</span><br><span class="line">64</span><br><span class="line">65</span><br><span class="line">66</span><br><span class="line">67</span><br><span class="line">68</span><br><span class="line">69</span><br><span class="line">70</span><br><span class="line">71</span><br><span class="line">72</span><br><span class="line">73</span><br><span class="line">74</span><br></pre></td><td class="code"><pre><span class="line">Classfile /C:/Users/username/Documents/github/jvm-study/target/classes/com/moralok/jvm/memory/methodarea/MethodAreaTest_2.class</span><br><span class="line">  Last modified 2023-11-4; size 619 bytes</span><br><span class="line">  MD5 checksum 0ed10a8f0a03be54fd4159958ee7446c</span><br><span class="line">  Compiled from &quot;MethodAreaTest_2.java&quot;</span><br><span class="line">public class com.moralok.jvm.memory.methodarea.MethodAreaTest_2</span><br><span class="line">  minor version: 0</span><br><span class="line">  major version: 52</span><br><span class="line">  flags: ACC_PUBLIC, ACC_SUPER</span><br><span class="line">Constant pool:</span><br><span class="line"><span class="meta prompt_">   #</span><span class="language-bash">1 = Methodref          <span class="comment">#6.#20         // java/lang/Object.&quot;&lt;init&gt;&quot;:()V</span></span></span><br><span class="line"><span class="meta prompt_">   #</span><span class="language-bash">2 = Fieldref           <span class="comment">#21.#22        // java/lang/System.out:Ljava/io/PrintStream;</span></span></span><br><span class="line"><span class="meta prompt_">   #</span><span class="language-bash">3 = String             <span class="comment">#23            // hello world</span></span></span><br><span class="line"><span class="meta prompt_">   #</span><span class="language-bash">4 = Methodref          <span class="comment">#24.#25        // java/io/PrintStream.println:(Ljava/lang/String;)V</span></span></span><br><span class="line"><span class="meta prompt_">   #</span><span class="language-bash">5 = Class              <span class="comment">#26            // com/moralok/jvm/memory/methodarea/MethodAreaTest_2</span></span></span><br><span class="line"><span class="meta prompt_">   #</span><span class="language-bash">6 = Class              <span class="comment">#27            // java/lang/Object</span></span></span><br><span class="line"><span class="meta prompt_">   #</span><span class="language-bash">7 = Utf8               &lt;init&gt;</span></span><br><span class="line"><span class="meta prompt_">   #</span><span class="language-bash">8 = Utf8               ()V</span></span><br><span class="line"><span class="meta prompt_">   #</span><span class="language-bash">9 = Utf8               Code</span></span><br><span class="line"><span class="meta prompt_">  #</span><span class="language-bash">10 = Utf8               LineNumberTable</span></span><br><span class="line"><span class="meta prompt_">  #</span><span class="language-bash">11 = Utf8               LocalVariableTable</span></span><br><span class="line"><span class="meta prompt_">  #</span><span class="language-bash">12 = Utf8               this</span></span><br><span class="line"><span class="meta prompt_">  #</span><span class="language-bash">13 = Utf8               Lcom/moralok/jvm/memory/methodarea/MethodAreaTest_2;</span></span><br><span class="line"><span class="meta prompt_">  #</span><span class="language-bash">14 = Utf8               main</span></span><br><span class="line"><span class="meta prompt_">  #</span><span class="language-bash">15 = Utf8               ([Ljava/lang/String;)V</span></span><br><span class="line"><span class="meta prompt_">  #</span><span class="language-bash">16 = Utf8               args</span></span><br><span class="line"><span class="meta prompt_">  #</span><span class="language-bash">17 = Utf8               [Ljava/lang/String;</span></span><br><span class="line"><span class="meta prompt_">  #</span><span class="language-bash">18 = Utf8               SourceFile</span></span><br><span class="line"><span class="meta prompt_">  #</span><span class="language-bash">19 = Utf8               MethodAreaTest_2.java</span></span><br><span class="line"><span class="meta prompt_">  #</span><span class="language-bash">20 = NameAndType        <span class="comment">#7:#8          // &quot;&lt;init&gt;&quot;:()V</span></span></span><br><span class="line"><span class="meta prompt_">  #</span><span class="language-bash">21 = Class              <span class="comment">#28            // java/lang/System</span></span></span><br><span class="line"><span class="meta prompt_">  #</span><span class="language-bash">22 = NameAndType        <span class="comment">#29:#30        // out:Ljava/io/PrintStream;</span></span></span><br><span class="line"><span class="meta prompt_">  #</span><span class="language-bash">23 = Utf8               hello world</span></span><br><span class="line"><span class="meta prompt_">  #</span><span class="language-bash">24 = Class              <span class="comment">#31            // java/io/PrintStream</span></span></span><br><span class="line"><span class="meta prompt_">  #</span><span class="language-bash">25 = NameAndType        <span class="comment">#32:#33        // println:(Ljava/lang/String;)V</span></span></span><br><span class="line"><span class="meta prompt_">  #</span><span class="language-bash">26 = Utf8               com/moralok/jvm/memory/methodarea/MethodAreaTest_2</span></span><br><span class="line"><span class="meta prompt_">  #</span><span class="language-bash">27 = Utf8               java/lang/Object</span></span><br><span class="line"><span class="meta prompt_">  #</span><span class="language-bash">28 = Utf8               java/lang/System</span></span><br><span class="line"><span class="meta prompt_">  #</span><span class="language-bash">29 = Utf8               out</span></span><br><span class="line"><span class="meta prompt_">  #</span><span class="language-bash">30 = Utf8               Ljava/io/PrintStream;</span></span><br><span class="line"><span class="meta prompt_">  #</span><span class="language-bash">31 = Utf8               java/io/PrintStream</span></span><br><span class="line"><span class="meta prompt_">  #</span><span class="language-bash">32 = Utf8               println</span></span><br><span class="line"><span class="meta prompt_">  #</span><span class="language-bash">33 = Utf8               (Ljava/lang/String;)V</span></span><br><span class="line">&#123;</span><br><span class="line">  public com.moralok.jvm.memory.methodarea.MethodAreaTest_2();</span><br><span class="line">    descriptor: ()V</span><br><span class="line">    flags: ACC_PUBLIC</span><br><span class="line">    Code:</span><br><span class="line">      stack=1, locals=1, args_size=1</span><br><span class="line">         0: aload_0</span><br><span class="line">         1: invokespecial #1                  // Method java/lang/Object.&quot;&lt;init&gt;&quot;:()V</span><br><span class="line">         4: return</span><br><span class="line">      LineNumberTable:</span><br><span class="line">        line 3: 0</span><br><span class="line">      LocalVariableTable:</span><br><span class="line">        Start  Length  Slot  Name   Signature</span><br><span class="line">            0       5     0  this   Lcom/moralok/jvm/memory/methodarea/MethodAreaTest_2;</span><br><span class="line"></span><br><span class="line">  public static void main(java.lang.String[]);</span><br><span class="line">    descriptor: ([Ljava/lang/String;)V</span><br><span class="line">    flags: ACC_PUBLIC, ACC_STATIC</span><br><span class="line">    Code:</span><br><span class="line">      stack=2, locals=1, args_size=1</span><br><span class="line">         0: getstatic     #2                  // Field java/lang/System.out:Ljava/io/PrintStream;</span><br><span class="line">         3: ldc           #3                  // String hello world</span><br><span class="line">         5: invokevirtual #4                  // Method java/io/PrintStream.println:(Ljava/lang/String;)V</span><br><span class="line">         8: return</span><br><span class="line">      LineNumberTable:</span><br><span class="line">        line 6: 0</span><br><span class="line">        line 7: 8</span><br><span class="line">      LocalVariableTable:</span><br><span class="line">        Start  Length  Slot  Name   Signature</span><br><span class="line">            0       9     0  args   [Ljava/lang/String;</span><br><span class="line">&#125;</span><br><span class="line">SourceFile: &quot;MethodAreaTest_2.java&quot;</span><br></pre></td></tr></table></figure>
-
-<ol>
-<li>Class 文件的常量池就是一张表，虚拟机根据索引去查找类名、字段名及其类型，方法名及其参数类型和字面量等。</li>
-<li>当类被加载到虚拟机之后，Class 文件中的常量池中的信息就进入到了运行时常量池。</li>
-<li>这个过程其实就是信息从文件进入了内存。</li>
-</ol>
-<p>虚拟机解释器（interpreter）需要解释的字节码指令如下：</p>
-<figure class="highlight console"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line">0: getstatic     #2</span><br><span class="line">3: ldc           #3</span><br><span class="line">5: invokevirtual #4</span><br></pre></td></tr></table></figure>
-<p>索引 <code>#2</code> 的意思就是去常量表里查找对应项代表的事物。</p>
-<h2 id="直接内存"><a href="#直接内存" class="headerlink" title="直接内存"></a>直接内存</h2><ul>
-<li>常见于 NIO 操作中的数据缓冲区。</li>
-<li>分配和回收的成本较高，但读写性能更高。</li>
-<li>不由 JVM 进行内存释放</li>
-</ul>
-<h3 id="NIO-和-IO-的拷贝性能"><a href="#NIO-和-IO-的拷贝性能" class="headerlink" title="NIO 和 IO 的拷贝性能"></a>NIO 和 IO 的拷贝性能</h3><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br><span class="line">46</span><br><span class="line">47</span><br><span class="line">48</span><br><span class="line">49</span><br><span class="line">50</span><br><span class="line">51</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">class</span> <span class="title class_">DirectMemoryTest_1</span> &#123;  </span><br><span class="line">  </span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">static</span> <span class="keyword">final</span> <span class="type">String</span> <span class="variable">FROM</span> <span class="operator">=</span> <span class="string">&quot;C:\\Users\\username\\Videos\\jellyfin\\media\\movies\\Harry Potter and the Chamber of Secrets (2002) [1080p]\\Harry.Potter.and.the.Chamber.of.Secrets.2002.1080p.BrRip.x264.YIFY.mp4&quot;</span>;  </span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">static</span> <span class="keyword">final</span> <span class="type">String</span> <span class="variable">TO</span> <span class="operator">=</span> <span class="string">&quot;C:\\Users\\username\\Videos\\jellyfin\\media\\movies\\Harry Potter and the Chamber of Secrets (2002) [1080p]\\Harry.Potter.and.the.Chamber.of.Secrets.2002.1080p.BrRip.x264.YIFY-copy.mp4&quot;</span>;  </span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">static</span> <span class="keyword">final</span> <span class="type">int</span> <span class="variable">_1Mb</span> <span class="operator">=</span> <span class="number">1024</span> * <span class="number">1024</span>;  </span><br><span class="line">  </span><br><span class="line">    <span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">main</span><span class="params">(String[] args)</span> &#123;  </span><br><span class="line">        io();  </span><br><span class="line">        directBuffer();  </span><br><span class="line">    &#125;  </span><br><span class="line">  </span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">directBuffer</span><span class="params">()</span> &#123;  </span><br><span class="line">        <span class="type">long</span> <span class="variable">start</span> <span class="operator">=</span> System.nanoTime();  </span><br><span class="line">        <span class="keyword">try</span> (<span class="type">FileChannel</span> <span class="variable">from</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">FileInputStream</span>(FROM).getChannel();  </span><br><span class="line">             <span class="type">FileChannel</span> <span class="variable">to</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">FileOutputStream</span>(TO).getChannel()) &#123;  </span><br><span class="line">            <span class="type">ByteBuffer</span> <span class="variable">buffer</span> <span class="operator">=</span> ByteBuffer.allocateDirect(_1Mb);  </span><br><span class="line">            <span class="keyword">while</span> (<span class="literal">true</span>) &#123;  </span><br><span class="line">                <span class="type">int</span> <span class="variable">len</span> <span class="operator">=</span> from.read(buffer);  </span><br><span class="line">                <span class="keyword">if</span> (len == -<span class="number">1</span>) &#123;  </span><br><span class="line">                    <span class="keyword">break</span>;  </span><br><span class="line">                &#125;  </span><br><span class="line">                buffer.flip();  </span><br><span class="line">                to.write(buffer);  </span><br><span class="line">                buffer.clear();  </span><br><span class="line">            &#125;  </span><br><span class="line">        &#125; <span class="keyword">catch</span> (IOException e) &#123;  </span><br><span class="line">            e.printStackTrace();  </span><br><span class="line">        &#125;  </span><br><span class="line">        <span class="type">long</span> <span class="variable">end</span> <span class="operator">=</span> System.nanoTime();  </span><br><span class="line">        System.out.println(<span class="string">&quot;directBuffer 用时 &quot;</span> + (end - start) / <span class="number">1000_000.0</span>);  </span><br><span class="line">    &#125;  </span><br><span class="line">  </span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">io</span><span class="params">()</span> &#123;  </span><br><span class="line">        <span class="type">long</span> <span class="variable">start</span> <span class="operator">=</span> System.nanoTime();  </span><br><span class="line">        <span class="keyword">try</span> (<span class="type">FileInputStream</span> <span class="variable">from</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">FileInputStream</span>(FROM);  </span><br><span class="line">             <span class="type">FileOutputStream</span> <span class="variable">to</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">FileOutputStream</span>(TO)) &#123;  </span><br><span class="line">            <span class="type">byte</span>[] buffer = <span class="keyword">new</span> <span class="title class_">byte</span>[_1Mb];  </span><br><span class="line">            <span class="keyword">while</span> (<span class="literal">true</span>) &#123;  </span><br><span class="line">                <span class="type">int</span> <span class="variable">len</span> <span class="operator">=</span> from.read(buffer);  </span><br><span class="line">                <span class="keyword">if</span> (len == -<span class="number">1</span>) &#123;  </span><br><span class="line">                    <span class="keyword">break</span>;  </span><br><span class="line">                &#125;  </span><br><span class="line">                to.write(buffer);  </span><br><span class="line">            &#125;  </span><br><span class="line">        &#125; <span class="keyword">catch</span> (IOException e) &#123;  </span><br><span class="line">            e.printStackTrace();  </span><br><span class="line">        &#125;  </span><br><span class="line">        <span class="type">long</span> <span class="variable">end</span> <span class="operator">=</span> System.nanoTime();  </span><br><span class="line">        System.out.println(<span class="string">&quot;io 用时 &quot;</span> + (end - start) / <span class="number">1000_000.0</span>);  </span><br><span class="line">    &#125;  </span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
-
-<figure class="highlight console"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line">io 用时 1676.9797</span><br><span class="line">directBuffer 用时 836.4796</span><br></pre></td></tr></table></figure>
-
-<img src="/2023/11/04/testing-and-analysis-of-jvm-memory-area/Pasted%20image%2020231104235546.png" class="" title="普通的 IO 拷贝">
-
-<img src="/2023/11/04/testing-and-analysis-of-jvm-memory-area/Pasted%20image%2020231104235846.png" class="" title="NIO 拷贝">
-
-
-<h3 id="直接内存溢出"><a href="#直接内存溢出" class="headerlink" title="直接内存溢出"></a>直接内存溢出</h3><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">class</span> <span class="title class_">DirectMemoryTest_2</span> &#123;  </span><br><span class="line">  </span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">static</span> <span class="keyword">final</span> <span class="type">int</span> <span class="variable">_100Mb</span> <span class="operator">=</span> <span class="number">1024</span> * <span class="number">1024</span> * <span class="number">100</span>;  </span><br><span class="line">  </span><br><span class="line">    <span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">main</span><span class="params">(String[] args)</span> &#123;  </span><br><span class="line">        List&lt;ByteBuffer&gt; list = <span class="keyword">new</span> <span class="title class_">ArrayList</span>&lt;&gt;();  </span><br><span class="line">        <span class="type">int</span> <span class="variable">i</span> <span class="operator">=</span> <span class="number">0</span>;  </span><br><span class="line">        <span class="keyword">try</span> &#123;  </span><br><span class="line">            <span class="keyword">while</span> (<span class="literal">true</span>) &#123;  </span><br><span class="line">                <span class="type">ByteBuffer</span> <span class="variable">byteBuffer</span> <span class="operator">=</span> ByteBuffer.allocateDirect(_100Mb);  </span><br><span class="line">                list.add(byteBuffer);  </span><br><span class="line">                i++;  </span><br><span class="line">            &#125;  </span><br><span class="line">        &#125; <span class="keyword">catch</span> (Throwable t) &#123;  </span><br><span class="line">            t.printStackTrace();  </span><br><span class="line">        &#125; System.out.println(i);  </span><br><span class="line">    &#125;  </span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
-
-<figure class="highlight console"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br></pre></td><td class="code"><pre><span class="line">java.lang.OutOfMemoryError: Direct buffer memory</span><br><span class="line">	at java.nio.Bits.reserveMemory(Bits.java:695)</span><br><span class="line">	at java.nio.DirectByteBuffer.&lt;init&gt;(DirectByteBuffer.java:123)</span><br><span class="line">	at java.nio.ByteBuffer.allocateDirect(ByteBuffer.java:311)</span><br><span class="line">	at com.moralok.jvm.memory.direct.DirectMemoryTest_2.main(DirectMemoryTest_2.java:16)</span><br><span class="line">145</span><br></pre></td></tr></table></figure>
-
-<p>这似乎是代码中抛出的异常，而不是真正的直接内存溢出？</p>
-<h3 id="直接内存释放的原理"><a href="#直接内存释放的原理" class="headerlink" title="直接内存释放的原理"></a>直接内存释放的原理</h3><h4 id="演示直接内存的释放受-GC-影响"><a href="#演示直接内存的释放受-GC-影响" class="headerlink" title="演示直接内存的释放受 GC 影响"></a>演示直接内存的释放受 GC 影响</h4><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">class</span> <span class="title class_">DirectMemoryTest_3</span> &#123;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">static</span> <span class="keyword">final</span> <span class="type">int</span> <span class="variable">_1GB</span> <span class="operator">=</span> <span class="number">1024</span> * <span class="number">1024</span> * <span class="number">1024</span>;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">main</span><span class="params">(String[] args)</span> <span class="keyword">throws</span> IOException &#123;</span><br><span class="line">        <span class="type">ByteBuffer</span> <span class="variable">byteBuffer</span> <span class="operator">=</span> ByteBuffer.allocateDirect(_1GB);</span><br><span class="line">        System.out.println(<span class="string">&quot;分配完毕&quot;</span>);</span><br><span class="line">        System.in.read();</span><br><span class="line">        System.out.println(<span class="string">&quot;开始释放&quot;</span>);</span><br><span class="line">        byteBuffer = <span class="literal">null</span>;</span><br><span class="line">        <span class="comment">// 随着 ByteBuffer 的释放，从任务管理器界面看到程序的内存的占用迅速下降 1GB。</span></span><br><span class="line">        System.gc();</span><br><span class="line">        System.in.read();</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
-
-<h4 id="手动进行直接内存的分配和释放"><a href="#手动进行直接内存的分配和释放" class="headerlink" title="手动进行直接内存的分配和释放"></a>手动进行直接内存的分配和释放</h4><p>在代码中实现手动进行直接内存的分配和释放。</p>
-<figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">class</span> <span class="title class_">DirectMemoryTest_4</span> &#123;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">static</span> <span class="keyword">final</span> <span class="type">int</span> <span class="variable">_1GB</span> <span class="operator">=</span> <span class="number">1024</span> * <span class="number">1024</span> * <span class="number">1024</span>;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">main</span><span class="params">(String[] args)</span> <span class="keyword">throws</span> IOException &#123;</span><br><span class="line">        <span class="type">Unsafe</span> <span class="variable">unsafe</span> <span class="operator">=</span> getUnsafe();</span><br><span class="line"></span><br><span class="line">        <span class="comment">// 分配内存</span></span><br><span class="line">        <span class="type">long</span> <span class="variable">base</span> <span class="operator">=</span> unsafe.allocateMemory(_1GB);</span><br><span class="line">        unsafe.setMemory(base, _1GB, (<span class="type">byte</span>) <span class="number">0</span>);</span><br><span class="line">        System.in.read();</span><br><span class="line"></span><br><span class="line">        <span class="comment">// 释放内存</span></span><br><span class="line">        unsafe.freeMemory(base);</span><br><span class="line">        System.in.read();</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">static</span> Unsafe <span class="title function_">getUnsafe</span><span class="params">()</span> &#123;</span><br><span class="line">        <span class="keyword">try</span> &#123;</span><br><span class="line">            <span class="type">Field</span> <span class="variable">f</span> <span class="operator">=</span> Unsafe.class.getDeclaredField(<span class="string">&quot;theUnsafe&quot;</span>);</span><br><span class="line">            f.setAccessible(<span class="literal">true</span>);</span><br><span class="line">            <span class="type">Unsafe</span> <span class="variable">unsafe</span> <span class="operator">=</span> (Unsafe) f.get(<span class="literal">null</span>);</span><br><span class="line">            <span class="keyword">return</span> unsafe;</span><br><span class="line">        &#125; <span class="keyword">catch</span> (NoSuchFieldException | IllegalAccessException e) &#123;</span><br><span class="line">            <span class="keyword">throw</span> <span class="keyword">new</span> <span class="title class_">RuntimeException</span>(e);</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
-
-<h4 id="如何将-GC-和直接内存的分配和释放关联"><a href="#如何将-GC-和直接内存的分配和释放关联" class="headerlink" title="如何将 GC 和直接内存的分配和释放关联"></a>如何将 GC 和直接内存的分配和释放关联</h4><p>本质上，直接内存的自动释放是利用了虚引用的机制，间接调用了 unsafe 的分配和释放直接内存的方法。</p>
-<p>DirectByteBuffer 就是使用 unsafe.allocateMemory(size) 分配直接内存。DirectByteBuffer 对象以及一个 Deallocator 对象（Runnable 类型）一起用于创建了一个虚引用类型的 Cleaner 对象。</p>
-<figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br></pre></td><td class="code"><pre><span class="line">DirectByteBuffer(<span class="type">int</span> cap) &#123;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 省略</span></span><br><span class="line">    <span class="keyword">try</span> &#123;</span><br><span class="line">        base = unsafe.allocateMemory(size);</span><br><span class="line">    &#125; <span class="keyword">catch</span> (OutOfMemoryError x) &#123;</span><br><span class="line">        Bits.unreserveMemory(size, cap);</span><br><span class="line">        <span class="keyword">throw</span> x;</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="comment">// 省略</span></span><br><span class="line">    cleaner = Cleaner.create(<span class="built_in">this</span>, <span class="keyword">new</span> <span class="title class_">Deallocator</span>(base, size, cap));</span><br><span class="line">    att = <span class="literal">null</span>;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
-
-<p>根据虚引用的机制，如果 DirectByteBuffer 对象被回收，虚引用对象会被加入到 Cleanner 的引用队列，ReferenceHandler 线程会处理引用队列中的 Cleaner 对象，进而调用 Deallocator 对象的 run 方法。</p>
-<figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title function_">run</span><span class="params">()</span> &#123;</span><br><span class="line">    <span class="keyword">if</span> (address == <span class="number">0</span>) &#123;</span><br><span class="line">        <span class="comment">// Paranoia</span></span><br><span class="line">        <span class="keyword">return</span>;</span><br><span class="line">    &#125;</span><br><span class="line">    unsafe.freeMemory(address);</span><br><span class="line">    address = <span class="number">0</span>;</span><br><span class="line">    Bits.unreserveMemory(size, capacity);</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
-
-      
-    </div>
-
-    
-    
-    
-
-    <footer class="post-footer">
-        <div class="post-eof"></div>
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-  </article>
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     <a class="extend prev" rel="prev" title="上一页" aria-label="上一页" href="/page/2/"><i class="fa fa-angle-left"></i></a><a class="page-number" href="/">1</a><a class="page-number" href="/page/2/">2</a><span class="page-number current">3</span><a class="page-number" href="/page/4/">4</a><a class="page-number" href="/page/5/">5</a><a class="extend next" rel="next" title="下一页" aria-label="下一页" href="/page/4/"><i class="fa fa-angle-right"></i></a>
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@@ -2041,13 +1913,13 @@ <h4 id="如何将-GC-和直接内存的分配和释放关联"><a href="#如何
     <span class="post-meta-item-icon">
       <i class="fa fa-chart-line"></i>
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-    <span title="站点总字数">125k</span>
+    <span title="站点总字数">129k</span>
   </span>
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     <span class="post-meta-item-icon">
       <i class="fa fa-coffee"></i>
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-    <span title="站点阅读时长">6:56</span>
+    <span title="站点阅读时长">7:09</span>
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 </div>
   <div class="powered-by">由 <a href="https://hexo.io/" rel="noopener" target="_blank">Hexo</a> & <a href="https://theme-next.js.org/" rel="noopener" target="_blank">NexT.Gemini</a> 强力驱动
diff --git a/page/4/index.html b/page/4/index.html
index 9e4a6d47..48693efe 100644
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+++ b/page/4/index.html
@@ -151,7 +151,7 @@ <h1 class="site-title">Moralok</h1>
   <nav class="site-state">
       <div class="site-state-item site-state-posts">
         <a href="/archives/">
-          <span class="site-state-item-count">48</span>
+          <span class="site-state-item-count">49</span>
           <span class="site-state-item-name">日志</span>
         </a>
       </div>
@@ -183,6 +183,239 @@ <h1 class="site-title">Moralok</h1>
     
 
 
+<div class="post-block">
+  
+  
+
+  <article itemscope itemtype="http://schema.org/Article" class="post-content" lang="">
+    <link itemprop="mainEntityOfPage" href="https://www.moralok.com/2023/11/04/testing-and-analysis-of-jvm-memory-area/">
+
+    <span hidden itemprop="author" itemscope itemtype="http://schema.org/Person">
+      <meta itemprop="image" content="/images/avatar.gif">
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+    <span hidden itemprop="publisher" itemscope itemtype="http://schema.org/Organization">
+      <meta itemprop="name" content="Moralok">
+      <meta itemprop="description" content="假如生命只剩一天">
+    </span>
+
+    <span hidden itemprop="post" itemscope itemtype="http://schema.org/CreativeWork">
+      <meta itemprop="name" content="undefined | Moralok">
+      <meta itemprop="description" content="">
+    </span>
+      <header class="post-header">
+        <h2 class="post-title" itemprop="name headline">
+          <a href="/2023/11/04/testing-and-analysis-of-jvm-memory-area/" class="post-title-link" itemprop="url">JVM 内存区域的测试和分析</a>
+        </h2>
+
+        <div class="post-meta-container">
+          <div class="post-meta">
+    <span class="post-meta-item">
+      <span class="post-meta-item-icon">
+        <i class="far fa-calendar"></i>
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+      <span class="post-meta-item-text">发表于</span>
+
+      <time title="创建时间：2023-11-04 19:21:25" itemprop="dateCreated datePublished" datetime="2023-11-04T19:21:25+08:00">2023-11-04</time>
+    </span>
+    <span class="post-meta-item">
+      <span class="post-meta-item-icon">
+        <i class="far fa-calendar-check"></i>
+      </span>
+      <span class="post-meta-item-text">更新于</span>
+      <time title="修改时间：2024-04-24 02:42:37" itemprop="dateModified" datetime="2024-04-24T02:42:37+08:00">2024-04-24</time>
+    </span>
+
+  
+    <span id="/2023/11/04/testing-and-analysis-of-jvm-memory-area/" class="post-meta-item leancloud_visitors" data-flag-title="JVM 内存区域的测试和分析" title="阅读次数">
+      <span class="post-meta-item-icon">
+        <i class="far fa-eye"></i>
+      </span>
+      <span class="post-meta-item-text">阅读次数：</span>
+      <span class="leancloud-visitors-count"></span>
+    </span>
+    <span class="post-meta-break"></span>
+    <span class="post-meta-item" title="本文字数">
+      <span class="post-meta-item-icon">
+        <i class="far fa-file-word"></i>
+      </span>
+      <span class="post-meta-item-text">本文字数：</span>
+      <span>3.2k</span>
+    </span>
+    <span class="post-meta-item" title="阅读时长">
+      <span class="post-meta-item-icon">
+        <i class="far fa-clock"></i>
+      </span>
+      <span class="post-meta-item-text">阅读时长 &asymp;</span>
+      <span>11 分钟</span>
+    </span>
+</div>
+
+        </div>
+      </header>
+
+    
+    
+    
+    <div class="post-body" itemprop="articleBody">
+          <h2 id="内存区域"><a href="#内存区域" class="headerlink" title="内存区域"></a>内存区域</h2><p>JVM 内存区域划分为：</p>
+<ul>
+<li>程序计数器</li>
+<li>虚拟机栈</li>
+<li>本地方法栈</li>
+<li>堆</li>
+<li>方法区</li>
+</ul>
+<img src="/2023/11/04/testing-and-analysis-of-jvm-memory-area/Pasted%20image%2020231102215652.png" class="" title="内存区域划分">
+
+<h2 id="程序计数器"><a href="#程序计数器" class="headerlink" title="程序计数器"></a>程序计数器</h2><h2 id="虚拟机栈"><a href="#虚拟机栈" class="headerlink" title="虚拟机栈"></a>虚拟机栈</h2><p>Java 虚拟机栈（Java Virtual Machine Stack），线程私有，生命周期与线程相同。虚拟机栈描述的是 Java 方法执行的线程内存模型。每个方法被执行的时候，Java虚拟机都会同步创建一个栈帧（Stack Frame）用于存储局部变量表、操作数栈、动态连接、方法出口等信息。</p>
+<p>可以使用 <code>-Xss1024k</code> 设置虚拟机栈的大小。默认情况下都是 1024k，只有 Windows 中取决于虚拟内存。</p>
+<h3 id="栈内存溢出"><a href="#栈内存溢出" class="headerlink" title="栈内存溢出"></a>栈内存溢出</h3><ol>
+<li>栈帧过多导致栈内存溢出</li>
+<li>栈帧过大导致栈内存溢出（难复现）</li>
+</ol>
+<h4 id="不正确的递归调用"><a href="#不正确的递归调用" class="headerlink" title="不正确的递归调用"></a>不正确的递归调用</h4><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">class</span> <span class="title class_">StackTest_4</span> &#123;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">static</span> <span class="type">int</span> <span class="variable">count</span> <span class="operator">=</span> <span class="number">0</span>;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 改变栈的大小限制 -Xss256k，观察调用次数的变化</span></span><br><span class="line">    <span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">main</span><span class="params">(String[] args)</span> &#123;</span><br><span class="line">        <span class="keyword">try</span> &#123;</span><br><span class="line">            method1();</span><br><span class="line">        &#125; <span class="keyword">catch</span> (Throwable t) &#123;</span><br><span class="line">            t.printStackTrace();</span><br><span class="line">        &#125; <span class="keyword">finally</span> &#123;</span><br><span class="line">            <span class="comment">// 默认情况下经过 20000+ 次，改变参数后 3000+ 次</span></span><br><span class="line">            System.out.println(count);</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">method1</span><span class="params">()</span> &#123;</span><br><span class="line">        count++;</span><br><span class="line">        method1();</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+
+<h4 id="循环引用导致-JSON-解析无限循环"><a href="#循环引用导致-JSON-解析无限循环" class="headerlink" title="循环引用导致 JSON 解析无限循环"></a>循环引用导致 JSON 解析无限循环</h4><p>并非只有自己写的递归方法可能引发栈内存溢出，有可能第三方库也会引发栈内存溢出。</p>
+<figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br><span class="line">46</span><br><span class="line">47</span><br><span class="line">48</span><br><span class="line">49</span><br><span class="line">50</span><br><span class="line">51</span><br><span class="line">52</span><br><span class="line">53</span><br><span class="line">54</span><br><span class="line">55</span><br><span class="line">56</span><br><span class="line">57</span><br><span class="line">58</span><br><span class="line">59</span><br><span class="line">60</span><br><span class="line">61</span><br><span class="line">62</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">class</span> <span class="title class_">StackTest_5</span> &#123;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">main</span><span class="params">(String[] args)</span> <span class="keyword">throws</span> JsonProcessingException &#123;</span><br><span class="line">        <span class="type">Department</span> <span class="variable">department</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">Department</span>();</span><br><span class="line">        department.setName(<span class="string">&quot;Tech&quot;</span>);</span><br><span class="line"></span><br><span class="line">        <span class="type">Employee</span> <span class="variable">employee1</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">Employee</span>();</span><br><span class="line">        employee1.setName(<span class="string">&quot;Tom&quot;</span>);</span><br><span class="line">        employee1.setDepartment(department);</span><br><span class="line"></span><br><span class="line">        <span class="type">Employee</span> <span class="variable">employee2</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">Employee</span>();</span><br><span class="line">        employee2.setName(<span class="string">&quot;Tim&quot;</span>);</span><br><span class="line">        employee2.setDepartment(department);</span><br><span class="line"></span><br><span class="line">        department.setEmployees(Arrays.asList(employee1, employee2));</span><br><span class="line"></span><br><span class="line">        <span class="type">ObjectMapper</span> <span class="variable">objectMapper</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">ObjectMapper</span>();</span><br><span class="line">        System.out.println(objectMapper.writeValueAsString(department));</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">static</span> <span class="keyword">class</span> <span class="title class_">Department</span> &#123;</span><br><span class="line">        <span class="keyword">private</span> String name;</span><br><span class="line">        <span class="keyword">private</span> List&lt;Employee&gt; employees;</span><br><span class="line"></span><br><span class="line">        <span class="keyword">public</span> String <span class="title function_">getName</span><span class="params">()</span> &#123;</span><br><span class="line">            <span class="keyword">return</span> name;</span><br><span class="line">        &#125;</span><br><span class="line"></span><br><span class="line">        <span class="keyword">public</span> <span class="keyword">void</span> <span class="title function_">setName</span><span class="params">(String name)</span> &#123;</span><br><span class="line">            <span class="built_in">this</span>.name = name;</span><br><span class="line">        &#125;</span><br><span class="line"></span><br><span class="line">        <span class="keyword">public</span> List&lt;Employee&gt; <span class="title function_">getEmployees</span><span class="params">()</span> &#123;</span><br><span class="line">            <span class="keyword">return</span> employees;</span><br><span class="line">        &#125;</span><br><span class="line"></span><br><span class="line">        <span class="keyword">public</span> <span class="keyword">void</span> <span class="title function_">setEmployees</span><span class="params">(List&lt;Employee&gt; employees)</span> &#123;</span><br><span class="line">            <span class="built_in">this</span>.employees = employees;</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">static</span> <span class="keyword">class</span> <span class="title class_">Employee</span> &#123;</span><br><span class="line">        <span class="keyword">private</span> String name;</span><br><span class="line">        <span class="keyword">private</span> Department department;</span><br><span class="line"></span><br><span class="line">        <span class="keyword">public</span> String <span class="title function_">getName</span><span class="params">()</span> &#123;</span><br><span class="line">            <span class="keyword">return</span> name;</span><br><span class="line">        &#125;</span><br><span class="line"></span><br><span class="line">        <span class="keyword">public</span> <span class="keyword">void</span> <span class="title function_">setName</span><span class="params">(String name)</span> &#123;</span><br><span class="line">            <span class="built_in">this</span>.name = name;</span><br><span class="line">        &#125;</span><br><span class="line"></span><br><span class="line">        <span class="keyword">public</span> Department <span class="title function_">getDepartment</span><span class="params">()</span> &#123;</span><br><span class="line">            <span class="keyword">return</span> department;</span><br><span class="line">        &#125;</span><br><span class="line"></span><br><span class="line">        <span class="keyword">public</span> <span class="keyword">void</span> <span class="title function_">setDepartment</span><span class="params">(Department department)</span> &#123;</span><br><span class="line">            <span class="built_in">this</span>.department = department;</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<h3 id="局部变量的线程安全问题"><a href="#局部变量的线程安全问题" class="headerlink" title="局部变量的线程安全问题"></a>局部变量的线程安全问题</h3><ol>
+<li>局部变量如果未逃离方法的作用范围，就是线程安全的。</li>
+<li>局部变量如果是引用类型且逃离了方法的作用范围，就是线程不安全的。</li>
+</ol>
+<figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">class</span> <span class="title class_">StackTest_3</span> &#123;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">main</span><span class="params">(String[] args)</span> &#123;</span><br><span class="line">        method1();</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 线程安全</span></span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">method1</span><span class="params">()</span> &#123;</span><br><span class="line">        <span class="type">StringBuilder</span> <span class="variable">sb</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">StringBuilder</span>();</span><br><span class="line">        sb.append(<span class="number">1</span>);</span><br><span class="line">        sb.append(<span class="number">2</span>);</span><br><span class="line">        sb.append(<span class="number">3</span>);</span><br><span class="line">        System.out.println(sb);</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 线程不安全</span></span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">method2</span><span class="params">(StringBuilder sb)</span> &#123;</span><br><span class="line">        sb.append(<span class="number">1</span>);</span><br><span class="line">        sb.append(<span class="number">2</span>);</span><br><span class="line">        sb.append(<span class="number">3</span>);</span><br><span class="line">        System.out.println(sb);</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 线程不安全，看到一个说法：发生指令重排，sb 的 append 操作发生在返回之后（有待确认）</span></span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">static</span> StringBuilder <span class="title function_">method3</span><span class="params">()</span> &#123;</span><br><span class="line">        <span class="type">StringBuilder</span> <span class="variable">sb</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">StringBuilder</span>();</span><br><span class="line">        sb.append(<span class="number">1</span>);</span><br><span class="line">        sb.append(<span class="number">2</span>);</span><br><span class="line">        sb.append(<span class="number">3</span>);</span><br><span class="line">        <span class="keyword">return</span> sb;</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<h3 id="线程问题排查"><a href="#线程问题排查" class="headerlink" title="线程问题排查"></a>线程问题排查</h3><h4 id="CPU-占用率居高不下"><a href="#CPU-占用率居高不下" class="headerlink" title="CPU 占用率居高不下"></a>CPU 占用率居高不下</h4><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">class</span> <span class="title class_">ThreadTest_1</span> &#123;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">main</span><span class="params">(String[] args)</span> &#123;</span><br><span class="line">        <span class="keyword">new</span> <span class="title class_">Thread</span>(<span class="literal">null</span>, () -&gt; &#123;</span><br><span class="line">            System.out.println(<span class="string">&quot;t1...&quot;</span>);</span><br><span class="line">            <span class="keyword">while</span> (<span class="literal">true</span>) &#123;</span><br><span class="line"></span><br><span class="line">            &#125;</span><br><span class="line">        &#125;, <span class="string">&quot;thread1&quot;</span>).start();</span><br><span class="line"></span><br><span class="line">        <span class="keyword">new</span> <span class="title class_">Thread</span>(<span class="literal">null</span>, () -&gt; &#123;</span><br><span class="line">            System.out.println(<span class="string">&quot;t2...&quot;</span>);</span><br><span class="line">            <span class="keyword">try</span> &#123;</span><br><span class="line">                TimeUnit.SECONDS.sleep(<span class="number">1000</span>);</span><br><span class="line">            &#125; <span class="keyword">catch</span> (InterruptedException e) &#123;</span><br><span class="line">                e.printStackTrace();</span><br><span class="line">            &#125;</span><br><span class="line">        &#125;, <span class="string">&quot;thread2&quot;</span>).start();</span><br><span class="line"></span><br><span class="line">        <span class="keyword">new</span> <span class="title class_">Thread</span>(<span class="literal">null</span>, () -&gt; &#123;</span><br><span class="line">            System.out.println(<span class="string">&quot;t3...&quot;</span>);</span><br><span class="line">            <span class="keyword">try</span> &#123;</span><br><span class="line">                TimeUnit.SECONDS.sleep(<span class="number">1000</span>);</span><br><span class="line">            &#125; <span class="keyword">catch</span> (InterruptedException e) &#123;</span><br><span class="line">                e.printStackTrace();</span><br><span class="line">            &#125;</span><br><span class="line">        &#125;, <span class="string">&quot;thread3&quot;</span>).start();</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+<p>当发现 CPU 占用率居高不下时，可以尝试以下步骤：</p>
+<ol>
+<li><code>top</code>，定位 cpu 占用高的进程 id。</li>
+<li><code>ps H -eo pid,tid,%cpu | grep pid</code>，进一步定位引起 cpu 占用高的线程 id。</li>
+<li><code>jstack pid</code>，根据线程 id 换算成 16进制的 nid 找到对应线程，进一步定位到问题的源码行号。</li>
+</ol>
+<figure class="highlight console"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br></pre></td><td class="code"><pre><span class="line">&quot;thread1&quot; #8 prio=5 os_prio=0 tid=0x00007f9bd0162800 nid=0x1061ad runnable [0x00007f9bd56eb000]</span><br><span class="line">   java.lang.Thread.State: RUNNABLE</span><br><span class="line">	at com.moralok.jvm.thread.ThreadTest_1.lambda$main$0(ThreadTest_1.java:10)</span><br><span class="line">	at com.moralok.jvm.thread.ThreadTest_1$$Lambda$1/250421012.run(Unknown Source)</span><br><span class="line">	at java.lang.Thread.run(Thread.java:750)</span><br></pre></td></tr></table></figure>
+
+<h4 id="死锁，迟迟未返回结果"><a href="#死锁，迟迟未返回结果" class="headerlink" title="死锁，迟迟未返回结果"></a>死锁，迟迟未返回结果</h4><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">class</span> <span class="title class_">ThreadTest_2</span> &#123;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">static</span> <span class="keyword">final</span> <span class="type">Object</span> <span class="variable">A</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">Object</span>();</span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">static</span> <span class="keyword">final</span> <span class="type">Object</span> <span class="variable">B</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">Object</span>();</span><br><span class="line"></span><br><span class="line">    <span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">main</span><span class="params">(String[] args)</span> &#123;</span><br><span class="line">        <span class="keyword">new</span> <span class="title class_">Thread</span>(<span class="literal">null</span>, () -&gt; &#123;</span><br><span class="line">            System.out.println(<span class="string">&quot;t1...&quot;</span>);</span><br><span class="line">            <span class="keyword">synchronized</span> (A) &#123;</span><br><span class="line">                System.out.println(Thread.currentThread().getName() + <span class="string">&quot; get A&quot;</span>);</span><br><span class="line">                <span class="keyword">try</span> &#123;</span><br><span class="line">                    TimeUnit.SECONDS.sleep(<span class="number">5</span>);</span><br><span class="line">                &#125; <span class="keyword">catch</span> (InterruptedException e) &#123;</span><br><span class="line">                    <span class="keyword">throw</span> <span class="keyword">new</span> <span class="title class_">RuntimeException</span>(e);</span><br><span class="line">                &#125;</span><br><span class="line">                <span class="keyword">synchronized</span> (B) &#123;</span><br><span class="line">                    System.out.println(Thread.currentThread().getName() + <span class="string">&quot; get B&quot;</span>);</span><br><span class="line">                &#125;</span><br><span class="line">            &#125;</span><br><span class="line">        &#125;, <span class="string">&quot;thread1&quot;</span>).start();</span><br><span class="line"></span><br><span class="line">        <span class="keyword">new</span> <span class="title class_">Thread</span>(<span class="literal">null</span>, () -&gt; &#123;</span><br><span class="line">            System.out.println(<span class="string">&quot;t2...&quot;</span>);</span><br><span class="line">            <span class="keyword">synchronized</span> (B) &#123;</span><br><span class="line">                System.out.println(Thread.currentThread().getName() + <span class="string">&quot; get B&quot;</span>);</span><br><span class="line">                <span class="keyword">try</span> &#123;</span><br><span class="line">                    TimeUnit.SECONDS.sleep(<span class="number">5</span>);</span><br><span class="line">                &#125; <span class="keyword">catch</span> (InterruptedException e) &#123;</span><br><span class="line">                    <span class="keyword">throw</span> <span class="keyword">new</span> <span class="title class_">RuntimeException</span>(e);</span><br><span class="line">                &#125;</span><br><span class="line">                <span class="keyword">synchronized</span> (A) &#123;</span><br><span class="line">                    System.out.println(Thread.currentThread().getName() + <span class="string">&quot; get A&quot;</span>);</span><br><span class="line">                &#125;</span><br><span class="line">            &#125;</span><br><span class="line">        &#125;, <span class="string">&quot;thread2&quot;</span>).start();</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<ol>
+<li><code>jstack pid</code>，会显示找到死锁，以及死锁涉及的线程,，并各自持有的锁还有等待的锁。</li>
+<li>其他工具如 jconsole 也具有检测死锁的功能。</li>
+</ol>
+<h2 id="本地方法栈"><a href="#本地方法栈" class="headerlink" title="本地方法栈"></a>本地方法栈</h2><h2 id="堆"><a href="#堆" class="headerlink" title="堆"></a>堆</h2><p>堆（Heap）的特点：</p>
+<ol>
+<li>线程共享，需要考虑线程安全问题。</li>
+<li>存在垃圾回收机制。</li>
+<li>使用 -Xmx8m 设置大小。</li>
+</ol>
+<h3 id="堆内存溢出"><a href="#堆内存溢出" class="headerlink" title="堆内存溢出"></a>堆内存溢出</h3><p>既然堆有垃圾回收机制，为什么还会发生内存溢出呢？最开始的时候，我也有这样的困惑。<br>后来我才认识到，还在使用中的对象是不能被强制回收的，不再使用的对象不是立刻回收的。当创建对象却没有足够的内存空间时，如果清理掉那些不再使用的对象就有足够的内存空间，就不会发生内存溢出，程序只是表现为卡顿。</p>
+<figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">class</span> <span class="title class_">HeapTest_1</span> &#123;  </span><br><span class="line">  </span><br><span class="line">    <span class="comment">// -Xmx8m  </span></span><br><span class="line">    <span class="comment">// 不设置可能不提示 Java heap space，出错地方不同，报错信息不同  </span></span><br><span class="line">    <span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">main</span><span class="params">(String[] args)</span> &#123;  </span><br><span class="line">        <span class="type">int</span> <span class="variable">i</span> <span class="operator">=</span> <span class="number">0</span>;  </span><br><span class="line">        <span class="keyword">try</span> &#123;  </span><br><span class="line">            List&lt;String&gt; list = <span class="keyword">new</span> <span class="title class_">ArrayList</span>&lt;&gt;();  </span><br><span class="line">            <span class="type">String</span> <span class="variable">s</span> <span class="operator">=</span> <span class="string">&quot;hello&quot;</span>;  </span><br><span class="line">            <span class="keyword">while</span> (<span class="literal">true</span>) &#123;  </span><br><span class="line">                list.add(s);  </span><br><span class="line">                s = s + s;  </span><br><span class="line">                i++;  </span><br><span class="line">            &#125;  </span><br><span class="line">        &#125; <span class="keyword">catch</span> (Throwable t) &#123;  </span><br><span class="line">            t.printStackTrace();  </span><br><span class="line">        &#125; <span class="keyword">finally</span> &#123;  </span><br><span class="line">            System.out.println(<span class="string">&quot;运行次数 &quot;</span> + i);  </span><br><span class="line">        &#125;  </span><br><span class="line">    &#125;  </span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<figure class="highlight console"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br></pre></td><td class="code"><pre><span class="line">java.lang.OutOfMemoryError: Java heap space</span><br><span class="line">	at java.util.Arrays.copyOf(Arrays.java:3332)</span><br><span class="line">	at java.lang.AbstractStringBuilder.ensureCapacityInternal(AbstractStringBuilder.java:124)</span><br><span class="line">	at java.lang.AbstractStringBuilder.append(AbstractStringBuilder.java:448)</span><br><span class="line">	at java.lang.StringBuilder.append(StringBuilder.java:141)</span><br><span class="line">	at com.moralok.jvm.memory.heap.HeapTest_1.main(HeapTest_1.java:21)</span><br><span class="line">运行次数 17</span><br></pre></td></tr></table></figure>
+
+<p>堆内存溢出的发生往往需要长时间的运行，因此在排查相关问题时，可以适当调小堆内存。</p>
+<h3 id="监测堆内存"><a href="#监测堆内存" class="headerlink" title="监测堆内存"></a>监测堆内存</h3><ol>
+<li>使用 jps 查看 Java 进程列表</li>
+<li>使用 <code>jmap -heap pid</code> 查看堆内存信息</li>
+<li>还可以使用 jconsole 观察堆内存变化曲线</li>
+<li>还可以使用 VisualVM 查看堆信息</li>
+</ol>
+<figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">class</span> <span class="title class_">HeapTest_2</span> &#123;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">main</span><span class="params">(String[] args)</span> <span class="keyword">throws</span> InterruptedException &#123;</span><br><span class="line">        System.out.println(<span class="string">&quot;1...&quot;</span>);</span><br><span class="line">        TimeUnit.SECONDS.sleep(<span class="number">30</span>);</span><br><span class="line">        <span class="comment">// 堆空间占用上升 10MB</span></span><br><span class="line">        <span class="type">byte</span>[] bytes = <span class="keyword">new</span> <span class="title class_">byte</span>[<span class="number">1024</span> * <span class="number">1024</span> * <span class="number">10</span>];</span><br><span class="line">        System.out.println(<span class="string">&quot;2...&quot;</span>);</span><br><span class="line">        TimeUnit.SECONDS.sleep(<span class="number">30</span>);</span><br><span class="line">        bytes = <span class="literal">null</span>;</span><br><span class="line">        <span class="comment">// 堆空间占用下降</span></span><br><span class="line">        System.gc();</span><br><span class="line">        System.out.println(<span class="string">&quot;3...&quot;</span>);</span><br><span class="line">        TimeUnit.SECONDS.sleep(<span class="number">3000</span>);</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<p>使用 <code>jmap -heap pid</code> 查看堆内存信息：</p>
+<figure class="highlight console"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br></pre></td><td class="code"><pre><span class="line">Eden Space:</span><br><span class="line">   capacity = 268435456 (256.0MB)</span><br><span class="line">   used     = 32212360 (30.72010040283203MB)</span><br><span class="line"></span><br><span class="line">   used     = 42698136 (40.720115661621094MB)</span><br><span class="line"></span><br><span class="line">   used     = 5368728 (5.120018005371094MB)</span><br></pre></td></tr></table></figure>
+
+<p>使用 jconsole 查看堆内存信息：</p>
+<img src="/2023/11/04/testing-and-analysis-of-jvm-memory-area/Pasted%20image%2020231104200411.png" class="" title="jconsole 观察堆内存占用">
+
+<h3 id="堆内存占用居高不下"><a href="#堆内存占用居高不下" class="headerlink" title="堆内存占用居高不下"></a>堆内存占用居高不下</h3><p>当你发现堆内存占用居高不下，经过 GC，下降也不明显，如果你想查看一下堆内的具体情况，可以将其 dump 查看。</p>
+<figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">class</span> <span class="title class_">HeapTest_3</span> &#123;  </span><br><span class="line">  </span><br><span class="line">    <span class="comment">// jps 查进程，jmap 看堆内存，jconsole 执行GC，堆内存占用没有明显下降  </span></span><br><span class="line">    <span class="comment">// 使用 VisualVM 的堆 dump 功能，观察大对象  </span></span><br><span class="line">    <span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">main</span><span class="params">(String[] args)</span> <span class="keyword">throws</span> IOException &#123;  </span><br><span class="line">        List&lt;Student&gt; students = <span class="keyword">new</span> <span class="title class_">ArrayList</span>&lt;&gt;();  </span><br><span class="line">        <span class="keyword">for</span> (<span class="type">int</span> <span class="variable">i</span> <span class="operator">=</span> <span class="number">0</span>; i &lt; <span class="number">200</span>; i++) &#123;  </span><br><span class="line">            students.add(<span class="keyword">new</span> <span class="title class_">Student</span>());  </span><br><span class="line">        &#125;  </span><br><span class="line">        System.in.read();  </span><br><span class="line">    &#125;  </span><br><span class="line">  </span><br><span class="line">    <span class="keyword">static</span> <span class="keyword">class</span> <span class="title class_">Student</span> &#123;  </span><br><span class="line">        <span class="keyword">private</span> <span class="type">byte</span>[] score = <span class="keyword">new</span> <span class="title class_">byte</span>[<span class="number">1024</span> * <span class="number">1024</span>];  </span><br><span class="line">    &#125;  </span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+<p>可使用 VisualVM 的 Heap Dump 功能：</p>
+<img src="/2023/11/04/testing-and-analysis-of-jvm-memory-area/Pasted%20image%2020231104201139.png" class="" title="VisualVM 观察堆中的大对象">
+
+<p>也可使用 <code>jmap -dump:format=b,file=filename.hprof pid</code>，需要其他分析工具搭配。</p>
+<h2 id="方法区"><a href="#方法区" class="headerlink" title="方法区"></a>方法区</h2><p>根据《Java虚拟机规范》，方法区在逻辑上是堆的一部分，但是在具体实现上，各个虚拟机厂商并不相同。对于 Hotspot 而言：</p>
+<ul>
+<li>JDK 8 之前，方法区的具体实现为永久代，使用堆内存，使用 -XX:MaxPermSize&#x3D;10m 设置大小。</li>
+<li>JDK 8 开始，方法区的具体实现为元空间，使用直接内存，使用 -XX:MaxMetaspaceSize&#x3D;10m 设置大小。</li>
+</ul>
+<h3 id="方法区溢出"><a href="#方法区溢出" class="headerlink" title="方法区溢出"></a>方法区溢出</h3><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">class</span> <span class="title class_">MethodAreaTest_1</span> <span class="keyword">extends</span> <span class="title class_">ClassLoader</span> &#123;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// -XX:MaxMetaspaceSize=8m MaxMetaspaceSize is too small.</span></span><br><span class="line">    <span class="comment">// -XX:MaxMetaspaceSize=10m java.lang.OutOfMemoryError: Compressed class space</span></span><br><span class="line">    <span class="comment">// 不是 Metaspace 应该是某个参数设置的问题</span></span><br><span class="line">    <span class="comment">// JDK 6: -XX:MaxPermSize=8m PermGen space</span></span><br><span class="line">    <span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">main</span><span class="params">(String[] args)</span> &#123;</span><br><span class="line">        <span class="type">int</span> <span class="variable">j</span> <span class="operator">=</span> <span class="number">0</span>;</span><br><span class="line">        <span class="keyword">try</span> &#123;</span><br><span class="line">            <span class="type">MethodAreaTest_1</span> <span class="variable">methodAreaTest1</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">MethodAreaTest_1</span>();</span><br><span class="line">            <span class="keyword">for</span> (<span class="type">int</span> <span class="variable">i</span> <span class="operator">=</span> <span class="number">0</span>; i &lt; <span class="number">20000</span>; i++, j++) &#123;</span><br><span class="line">                <span class="type">ClassWriter</span> <span class="variable">classWriter</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">ClassWriter</span>(<span class="number">0</span>);</span><br><span class="line">                <span class="comment">// 版本号，public，类名，包名，父类，接口</span></span><br><span class="line">                classWriter.visit(Opcodes.V1_8, Opcodes.ACC_PUBLIC, <span class="string">&quot;Class&quot;</span> + i, <span class="literal">null</span>, <span class="string">&quot;java/lang/Object&quot;</span>, <span class="literal">null</span>);</span><br><span class="line">                <span class="comment">// 返回二进制字节码</span></span><br><span class="line">                <span class="type">byte</span>[] code = classWriter.toByteArray();</span><br><span class="line">                <span class="comment">// 加载类</span></span><br><span class="line">                methodAreaTest1.defineClass(<span class="string">&quot;Class&quot;</span> + i, code, <span class="number">0</span>, code.length);</span><br><span class="line">            &#125;</span><br><span class="line">        &#125; <span class="keyword">catch</span> (ClassFormatError e) &#123;</span><br><span class="line">            e.printStackTrace();</span><br><span class="line">        &#125; <span class="keyword">finally</span> &#123;</span><br><span class="line">            System.out.println(<span class="string">&quot;次数 &quot;</span> + j);</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+<ol>
+<li>当设置的值太小时 -XX:MaxMetaspaceSize&#x3D;8m，提示 MaxMetaspaceSize is too small。</li>
+<li>实验中抛出 java.lang.OutOfMemoryError: Compressed class space。</li>
+<li>添加参数 -XX:-UseCompressedClassPointers 后，抛出 java.lang.OutOfMemoryError: Metaspace。</li>
+<li>JDK 6 设置 -XX:MaxPermSize&#x3D;8m，抛出 java.lang.OutOfMemoryError: PermGen space。</li>
+</ol>
+<p>不要认为自己不会写动态生成字节码相关的代码就忽略这方面的问题，如今很多框架使用字节码技术大量地动态生成类。</p>
+<h2 id="运行时常量池"><a href="#运行时常量池" class="headerlink" title="运行时常量池"></a>运行时常量池</h2><p>二进制字节码文件主要包含三类信息：</p>
+<ol>
+<li>类的基本信息</li>
+<li>类的常量池（Constant Pool）</li>
+<li>类的方法信息</li>
+</ol>
+<h3 id="使用-javap-反编译"><a href="#使用-javap-反编译" class="headerlink" title="使用 javap 反编译"></a>使用 javap 反编译</h3><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">class</span> <span class="title class_">MethodAreaTest_2</span> &#123;  </span><br><span class="line">  </span><br><span class="line">    <span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">main</span><span class="params">(String[] args)</span> &#123;  </span><br><span class="line">        System.out.println(<span class="string">&quot;hello world&quot;</span>);  </span><br><span class="line">    &#125;  </span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<figure class="highlight console"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br><span class="line">46</span><br><span class="line">47</span><br><span class="line">48</span><br><span class="line">49</span><br><span class="line">50</span><br><span class="line">51</span><br><span class="line">52</span><br><span class="line">53</span><br><span class="line">54</span><br><span class="line">55</span><br><span class="line">56</span><br><span class="line">57</span><br><span class="line">58</span><br><span class="line">59</span><br><span class="line">60</span><br><span class="line">61</span><br><span class="line">62</span><br><span class="line">63</span><br><span class="line">64</span><br><span class="line">65</span><br><span class="line">66</span><br><span class="line">67</span><br><span class="line">68</span><br><span class="line">69</span><br><span class="line">70</span><br><span class="line">71</span><br><span class="line">72</span><br><span class="line">73</span><br><span class="line">74</span><br></pre></td><td class="code"><pre><span class="line">Classfile /C:/Users/username/Documents/github/jvm-study/target/classes/com/moralok/jvm/memory/methodarea/MethodAreaTest_2.class</span><br><span class="line">  Last modified 2023-11-4; size 619 bytes</span><br><span class="line">  MD5 checksum 0ed10a8f0a03be54fd4159958ee7446c</span><br><span class="line">  Compiled from &quot;MethodAreaTest_2.java&quot;</span><br><span class="line">public class com.moralok.jvm.memory.methodarea.MethodAreaTest_2</span><br><span class="line">  minor version: 0</span><br><span class="line">  major version: 52</span><br><span class="line">  flags: ACC_PUBLIC, ACC_SUPER</span><br><span class="line">Constant pool:</span><br><span class="line"><span class="meta prompt_">   #</span><span class="language-bash">1 = Methodref          <span class="comment">#6.#20         // java/lang/Object.&quot;&lt;init&gt;&quot;:()V</span></span></span><br><span class="line"><span class="meta prompt_">   #</span><span class="language-bash">2 = Fieldref           <span class="comment">#21.#22        // java/lang/System.out:Ljava/io/PrintStream;</span></span></span><br><span class="line"><span class="meta prompt_">   #</span><span class="language-bash">3 = String             <span class="comment">#23            // hello world</span></span></span><br><span class="line"><span class="meta prompt_">   #</span><span class="language-bash">4 = Methodref          <span class="comment">#24.#25        // java/io/PrintStream.println:(Ljava/lang/String;)V</span></span></span><br><span class="line"><span class="meta prompt_">   #</span><span class="language-bash">5 = Class              <span class="comment">#26            // com/moralok/jvm/memory/methodarea/MethodAreaTest_2</span></span></span><br><span class="line"><span class="meta prompt_">   #</span><span class="language-bash">6 = Class              <span class="comment">#27            // java/lang/Object</span></span></span><br><span class="line"><span class="meta prompt_">   #</span><span class="language-bash">7 = Utf8               &lt;init&gt;</span></span><br><span class="line"><span class="meta prompt_">   #</span><span class="language-bash">8 = Utf8               ()V</span></span><br><span class="line"><span class="meta prompt_">   #</span><span class="language-bash">9 = Utf8               Code</span></span><br><span class="line"><span class="meta prompt_">  #</span><span class="language-bash">10 = Utf8               LineNumberTable</span></span><br><span class="line"><span class="meta prompt_">  #</span><span class="language-bash">11 = Utf8               LocalVariableTable</span></span><br><span class="line"><span class="meta prompt_">  #</span><span class="language-bash">12 = Utf8               this</span></span><br><span class="line"><span class="meta prompt_">  #</span><span class="language-bash">13 = Utf8               Lcom/moralok/jvm/memory/methodarea/MethodAreaTest_2;</span></span><br><span class="line"><span class="meta prompt_">  #</span><span class="language-bash">14 = Utf8               main</span></span><br><span class="line"><span class="meta prompt_">  #</span><span class="language-bash">15 = Utf8               ([Ljava/lang/String;)V</span></span><br><span class="line"><span class="meta prompt_">  #</span><span class="language-bash">16 = Utf8               args</span></span><br><span class="line"><span class="meta prompt_">  #</span><span class="language-bash">17 = Utf8               [Ljava/lang/String;</span></span><br><span class="line"><span class="meta prompt_">  #</span><span class="language-bash">18 = Utf8               SourceFile</span></span><br><span class="line"><span class="meta prompt_">  #</span><span class="language-bash">19 = Utf8               MethodAreaTest_2.java</span></span><br><span class="line"><span class="meta prompt_">  #</span><span class="language-bash">20 = NameAndType        <span class="comment">#7:#8          // &quot;&lt;init&gt;&quot;:()V</span></span></span><br><span class="line"><span class="meta prompt_">  #</span><span class="language-bash">21 = Class              <span class="comment">#28            // java/lang/System</span></span></span><br><span class="line"><span class="meta prompt_">  #</span><span class="language-bash">22 = NameAndType        <span class="comment">#29:#30        // out:Ljava/io/PrintStream;</span></span></span><br><span class="line"><span class="meta prompt_">  #</span><span class="language-bash">23 = Utf8               hello world</span></span><br><span class="line"><span class="meta prompt_">  #</span><span class="language-bash">24 = Class              <span class="comment">#31            // java/io/PrintStream</span></span></span><br><span class="line"><span class="meta prompt_">  #</span><span class="language-bash">25 = NameAndType        <span class="comment">#32:#33        // println:(Ljava/lang/String;)V</span></span></span><br><span class="line"><span class="meta prompt_">  #</span><span class="language-bash">26 = Utf8               com/moralok/jvm/memory/methodarea/MethodAreaTest_2</span></span><br><span class="line"><span class="meta prompt_">  #</span><span class="language-bash">27 = Utf8               java/lang/Object</span></span><br><span class="line"><span class="meta prompt_">  #</span><span class="language-bash">28 = Utf8               java/lang/System</span></span><br><span class="line"><span class="meta prompt_">  #</span><span class="language-bash">29 = Utf8               out</span></span><br><span class="line"><span class="meta prompt_">  #</span><span class="language-bash">30 = Utf8               Ljava/io/PrintStream;</span></span><br><span class="line"><span class="meta prompt_">  #</span><span class="language-bash">31 = Utf8               java/io/PrintStream</span></span><br><span class="line"><span class="meta prompt_">  #</span><span class="language-bash">32 = Utf8               println</span></span><br><span class="line"><span class="meta prompt_">  #</span><span class="language-bash">33 = Utf8               (Ljava/lang/String;)V</span></span><br><span class="line">&#123;</span><br><span class="line">  public com.moralok.jvm.memory.methodarea.MethodAreaTest_2();</span><br><span class="line">    descriptor: ()V</span><br><span class="line">    flags: ACC_PUBLIC</span><br><span class="line">    Code:</span><br><span class="line">      stack=1, locals=1, args_size=1</span><br><span class="line">         0: aload_0</span><br><span class="line">         1: invokespecial #1                  // Method java/lang/Object.&quot;&lt;init&gt;&quot;:()V</span><br><span class="line">         4: return</span><br><span class="line">      LineNumberTable:</span><br><span class="line">        line 3: 0</span><br><span class="line">      LocalVariableTable:</span><br><span class="line">        Start  Length  Slot  Name   Signature</span><br><span class="line">            0       5     0  this   Lcom/moralok/jvm/memory/methodarea/MethodAreaTest_2;</span><br><span class="line"></span><br><span class="line">  public static void main(java.lang.String[]);</span><br><span class="line">    descriptor: ([Ljava/lang/String;)V</span><br><span class="line">    flags: ACC_PUBLIC, ACC_STATIC</span><br><span class="line">    Code:</span><br><span class="line">      stack=2, locals=1, args_size=1</span><br><span class="line">         0: getstatic     #2                  // Field java/lang/System.out:Ljava/io/PrintStream;</span><br><span class="line">         3: ldc           #3                  // String hello world</span><br><span class="line">         5: invokevirtual #4                  // Method java/io/PrintStream.println:(Ljava/lang/String;)V</span><br><span class="line">         8: return</span><br><span class="line">      LineNumberTable:</span><br><span class="line">        line 6: 0</span><br><span class="line">        line 7: 8</span><br><span class="line">      LocalVariableTable:</span><br><span class="line">        Start  Length  Slot  Name   Signature</span><br><span class="line">            0       9     0  args   [Ljava/lang/String;</span><br><span class="line">&#125;</span><br><span class="line">SourceFile: &quot;MethodAreaTest_2.java&quot;</span><br></pre></td></tr></table></figure>
+
+<ol>
+<li>Class 文件的常量池就是一张表，虚拟机根据索引去查找类名、字段名及其类型，方法名及其参数类型和字面量等。</li>
+<li>当类被加载到虚拟机之后，Class 文件中的常量池中的信息就进入到了运行时常量池。</li>
+<li>这个过程其实就是信息从文件进入了内存。</li>
+</ol>
+<p>虚拟机解释器（interpreter）需要解释的字节码指令如下：</p>
+<figure class="highlight console"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line">0: getstatic     #2</span><br><span class="line">3: ldc           #3</span><br><span class="line">5: invokevirtual #4</span><br></pre></td></tr></table></figure>
+<p>索引 <code>#2</code> 的意思就是去常量表里查找对应项代表的事物。</p>
+<h2 id="直接内存"><a href="#直接内存" class="headerlink" title="直接内存"></a>直接内存</h2><ul>
+<li>常见于 NIO 操作中的数据缓冲区。</li>
+<li>分配和回收的成本较高，但读写性能更高。</li>
+<li>不由 JVM 进行内存释放</li>
+</ul>
+<h3 id="NIO-和-IO-的拷贝性能"><a href="#NIO-和-IO-的拷贝性能" class="headerlink" title="NIO 和 IO 的拷贝性能"></a>NIO 和 IO 的拷贝性能</h3><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br><span class="line">46</span><br><span class="line">47</span><br><span class="line">48</span><br><span class="line">49</span><br><span class="line">50</span><br><span class="line">51</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">class</span> <span class="title class_">DirectMemoryTest_1</span> &#123;  </span><br><span class="line">  </span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">static</span> <span class="keyword">final</span> <span class="type">String</span> <span class="variable">FROM</span> <span class="operator">=</span> <span class="string">&quot;C:\\Users\\username\\Videos\\jellyfin\\media\\movies\\Harry Potter and the Chamber of Secrets (2002) [1080p]\\Harry.Potter.and.the.Chamber.of.Secrets.2002.1080p.BrRip.x264.YIFY.mp4&quot;</span>;  </span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">static</span> <span class="keyword">final</span> <span class="type">String</span> <span class="variable">TO</span> <span class="operator">=</span> <span class="string">&quot;C:\\Users\\username\\Videos\\jellyfin\\media\\movies\\Harry Potter and the Chamber of Secrets (2002) [1080p]\\Harry.Potter.and.the.Chamber.of.Secrets.2002.1080p.BrRip.x264.YIFY-copy.mp4&quot;</span>;  </span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">static</span> <span class="keyword">final</span> <span class="type">int</span> <span class="variable">_1Mb</span> <span class="operator">=</span> <span class="number">1024</span> * <span class="number">1024</span>;  </span><br><span class="line">  </span><br><span class="line">    <span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">main</span><span class="params">(String[] args)</span> &#123;  </span><br><span class="line">        io();  </span><br><span class="line">        directBuffer();  </span><br><span class="line">    &#125;  </span><br><span class="line">  </span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">directBuffer</span><span class="params">()</span> &#123;  </span><br><span class="line">        <span class="type">long</span> <span class="variable">start</span> <span class="operator">=</span> System.nanoTime();  </span><br><span class="line">        <span class="keyword">try</span> (<span class="type">FileChannel</span> <span class="variable">from</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">FileInputStream</span>(FROM).getChannel();  </span><br><span class="line">             <span class="type">FileChannel</span> <span class="variable">to</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">FileOutputStream</span>(TO).getChannel()) &#123;  </span><br><span class="line">            <span class="type">ByteBuffer</span> <span class="variable">buffer</span> <span class="operator">=</span> ByteBuffer.allocateDirect(_1Mb);  </span><br><span class="line">            <span class="keyword">while</span> (<span class="literal">true</span>) &#123;  </span><br><span class="line">                <span class="type">int</span> <span class="variable">len</span> <span class="operator">=</span> from.read(buffer);  </span><br><span class="line">                <span class="keyword">if</span> (len == -<span class="number">1</span>) &#123;  </span><br><span class="line">                    <span class="keyword">break</span>;  </span><br><span class="line">                &#125;  </span><br><span class="line">                buffer.flip();  </span><br><span class="line">                to.write(buffer);  </span><br><span class="line">                buffer.clear();  </span><br><span class="line">            &#125;  </span><br><span class="line">        &#125; <span class="keyword">catch</span> (IOException e) &#123;  </span><br><span class="line">            e.printStackTrace();  </span><br><span class="line">        &#125;  </span><br><span class="line">        <span class="type">long</span> <span class="variable">end</span> <span class="operator">=</span> System.nanoTime();  </span><br><span class="line">        System.out.println(<span class="string">&quot;directBuffer 用时 &quot;</span> + (end - start) / <span class="number">1000_000.0</span>);  </span><br><span class="line">    &#125;  </span><br><span class="line">  </span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">io</span><span class="params">()</span> &#123;  </span><br><span class="line">        <span class="type">long</span> <span class="variable">start</span> <span class="operator">=</span> System.nanoTime();  </span><br><span class="line">        <span class="keyword">try</span> (<span class="type">FileInputStream</span> <span class="variable">from</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">FileInputStream</span>(FROM);  </span><br><span class="line">             <span class="type">FileOutputStream</span> <span class="variable">to</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">FileOutputStream</span>(TO)) &#123;  </span><br><span class="line">            <span class="type">byte</span>[] buffer = <span class="keyword">new</span> <span class="title class_">byte</span>[_1Mb];  </span><br><span class="line">            <span class="keyword">while</span> (<span class="literal">true</span>) &#123;  </span><br><span class="line">                <span class="type">int</span> <span class="variable">len</span> <span class="operator">=</span> from.read(buffer);  </span><br><span class="line">                <span class="keyword">if</span> (len == -<span class="number">1</span>) &#123;  </span><br><span class="line">                    <span class="keyword">break</span>;  </span><br><span class="line">                &#125;  </span><br><span class="line">                to.write(buffer);  </span><br><span class="line">            &#125;  </span><br><span class="line">        &#125; <span class="keyword">catch</span> (IOException e) &#123;  </span><br><span class="line">            e.printStackTrace();  </span><br><span class="line">        &#125;  </span><br><span class="line">        <span class="type">long</span> <span class="variable">end</span> <span class="operator">=</span> System.nanoTime();  </span><br><span class="line">        System.out.println(<span class="string">&quot;io 用时 &quot;</span> + (end - start) / <span class="number">1000_000.0</span>);  </span><br><span class="line">    &#125;  </span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<figure class="highlight console"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line">io 用时 1676.9797</span><br><span class="line">directBuffer 用时 836.4796</span><br></pre></td></tr></table></figure>
+
+<img src="/2023/11/04/testing-and-analysis-of-jvm-memory-area/Pasted%20image%2020231104235546.png" class="" title="普通的 IO 拷贝">
+
+<img src="/2023/11/04/testing-and-analysis-of-jvm-memory-area/Pasted%20image%2020231104235846.png" class="" title="NIO 拷贝">
+
+
+<h3 id="直接内存溢出"><a href="#直接内存溢出" class="headerlink" title="直接内存溢出"></a>直接内存溢出</h3><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">class</span> <span class="title class_">DirectMemoryTest_2</span> &#123;  </span><br><span class="line">  </span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">static</span> <span class="keyword">final</span> <span class="type">int</span> <span class="variable">_100Mb</span> <span class="operator">=</span> <span class="number">1024</span> * <span class="number">1024</span> * <span class="number">100</span>;  </span><br><span class="line">  </span><br><span class="line">    <span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">main</span><span class="params">(String[] args)</span> &#123;  </span><br><span class="line">        List&lt;ByteBuffer&gt; list = <span class="keyword">new</span> <span class="title class_">ArrayList</span>&lt;&gt;();  </span><br><span class="line">        <span class="type">int</span> <span class="variable">i</span> <span class="operator">=</span> <span class="number">0</span>;  </span><br><span class="line">        <span class="keyword">try</span> &#123;  </span><br><span class="line">            <span class="keyword">while</span> (<span class="literal">true</span>) &#123;  </span><br><span class="line">                <span class="type">ByteBuffer</span> <span class="variable">byteBuffer</span> <span class="operator">=</span> ByteBuffer.allocateDirect(_100Mb);  </span><br><span class="line">                list.add(byteBuffer);  </span><br><span class="line">                i++;  </span><br><span class="line">            &#125;  </span><br><span class="line">        &#125; <span class="keyword">catch</span> (Throwable t) &#123;  </span><br><span class="line">            t.printStackTrace();  </span><br><span class="line">        &#125; System.out.println(i);  </span><br><span class="line">    &#125;  </span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<figure class="highlight console"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br></pre></td><td class="code"><pre><span class="line">java.lang.OutOfMemoryError: Direct buffer memory</span><br><span class="line">	at java.nio.Bits.reserveMemory(Bits.java:695)</span><br><span class="line">	at java.nio.DirectByteBuffer.&lt;init&gt;(DirectByteBuffer.java:123)</span><br><span class="line">	at java.nio.ByteBuffer.allocateDirect(ByteBuffer.java:311)</span><br><span class="line">	at com.moralok.jvm.memory.direct.DirectMemoryTest_2.main(DirectMemoryTest_2.java:16)</span><br><span class="line">145</span><br></pre></td></tr></table></figure>
+
+<p>这似乎是代码中抛出的异常，而不是真正的直接内存溢出？</p>
+<h3 id="直接内存释放的原理"><a href="#直接内存释放的原理" class="headerlink" title="直接内存释放的原理"></a>直接内存释放的原理</h3><h4 id="演示直接内存的释放受-GC-影响"><a href="#演示直接内存的释放受-GC-影响" class="headerlink" title="演示直接内存的释放受 GC 影响"></a>演示直接内存的释放受 GC 影响</h4><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">class</span> <span class="title class_">DirectMemoryTest_3</span> &#123;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">static</span> <span class="keyword">final</span> <span class="type">int</span> <span class="variable">_1GB</span> <span class="operator">=</span> <span class="number">1024</span> * <span class="number">1024</span> * <span class="number">1024</span>;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">main</span><span class="params">(String[] args)</span> <span class="keyword">throws</span> IOException &#123;</span><br><span class="line">        <span class="type">ByteBuffer</span> <span class="variable">byteBuffer</span> <span class="operator">=</span> ByteBuffer.allocateDirect(_1GB);</span><br><span class="line">        System.out.println(<span class="string">&quot;分配完毕&quot;</span>);</span><br><span class="line">        System.in.read();</span><br><span class="line">        System.out.println(<span class="string">&quot;开始释放&quot;</span>);</span><br><span class="line">        byteBuffer = <span class="literal">null</span>;</span><br><span class="line">        <span class="comment">// 随着 ByteBuffer 的释放，从任务管理器界面看到程序的内存的占用迅速下降 1GB。</span></span><br><span class="line">        System.gc();</span><br><span class="line">        System.in.read();</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<h4 id="手动进行直接内存的分配和释放"><a href="#手动进行直接内存的分配和释放" class="headerlink" title="手动进行直接内存的分配和释放"></a>手动进行直接内存的分配和释放</h4><p>在代码中实现手动进行直接内存的分配和释放。</p>
+<figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">class</span> <span class="title class_">DirectMemoryTest_4</span> &#123;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">static</span> <span class="keyword">final</span> <span class="type">int</span> <span class="variable">_1GB</span> <span class="operator">=</span> <span class="number">1024</span> * <span class="number">1024</span> * <span class="number">1024</span>;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">main</span><span class="params">(String[] args)</span> <span class="keyword">throws</span> IOException &#123;</span><br><span class="line">        <span class="type">Unsafe</span> <span class="variable">unsafe</span> <span class="operator">=</span> getUnsafe();</span><br><span class="line"></span><br><span class="line">        <span class="comment">// 分配内存</span></span><br><span class="line">        <span class="type">long</span> <span class="variable">base</span> <span class="operator">=</span> unsafe.allocateMemory(_1GB);</span><br><span class="line">        unsafe.setMemory(base, _1GB, (<span class="type">byte</span>) <span class="number">0</span>);</span><br><span class="line">        System.in.read();</span><br><span class="line"></span><br><span class="line">        <span class="comment">// 释放内存</span></span><br><span class="line">        unsafe.freeMemory(base);</span><br><span class="line">        System.in.read();</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">static</span> Unsafe <span class="title function_">getUnsafe</span><span class="params">()</span> &#123;</span><br><span class="line">        <span class="keyword">try</span> &#123;</span><br><span class="line">            <span class="type">Field</span> <span class="variable">f</span> <span class="operator">=</span> Unsafe.class.getDeclaredField(<span class="string">&quot;theUnsafe&quot;</span>);</span><br><span class="line">            f.setAccessible(<span class="literal">true</span>);</span><br><span class="line">            <span class="type">Unsafe</span> <span class="variable">unsafe</span> <span class="operator">=</span> (Unsafe) f.get(<span class="literal">null</span>);</span><br><span class="line">            <span class="keyword">return</span> unsafe;</span><br><span class="line">        &#125; <span class="keyword">catch</span> (NoSuchFieldException | IllegalAccessException e) &#123;</span><br><span class="line">            <span class="keyword">throw</span> <span class="keyword">new</span> <span class="title class_">RuntimeException</span>(e);</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<h4 id="如何将-GC-和直接内存的分配和释放关联"><a href="#如何将-GC-和直接内存的分配和释放关联" class="headerlink" title="如何将 GC 和直接内存的分配和释放关联"></a>如何将 GC 和直接内存的分配和释放关联</h4><p>本质上，直接内存的自动释放是利用了虚引用的机制，间接调用了 unsafe 的分配和释放直接内存的方法。</p>
+<p>DirectByteBuffer 就是使用 unsafe.allocateMemory(size) 分配直接内存。DirectByteBuffer 对象以及一个 Deallocator 对象（Runnable 类型）一起用于创建了一个虚引用类型的 Cleaner 对象。</p>
+<figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br></pre></td><td class="code"><pre><span class="line">DirectByteBuffer(<span class="type">int</span> cap) &#123;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 省略</span></span><br><span class="line">    <span class="keyword">try</span> &#123;</span><br><span class="line">        base = unsafe.allocateMemory(size);</span><br><span class="line">    &#125; <span class="keyword">catch</span> (OutOfMemoryError x) &#123;</span><br><span class="line">        Bits.unreserveMemory(size, cap);</span><br><span class="line">        <span class="keyword">throw</span> x;</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="comment">// 省略</span></span><br><span class="line">    cleaner = Cleaner.create(<span class="built_in">this</span>, <span class="keyword">new</span> <span class="title class_">Deallocator</span>(base, size, cap));</span><br><span class="line">    att = <span class="literal">null</span>;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<p>根据虚引用的机制，如果 DirectByteBuffer 对象被回收，虚引用对象会被加入到 Cleanner 的引用队列，ReferenceHandler 线程会处理引用队列中的 Cleaner 对象，进而调用 Deallocator 对象的 run 方法。</p>
+<figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title function_">run</span><span class="params">()</span> &#123;</span><br><span class="line">    <span class="keyword">if</span> (address == <span class="number">0</span>) &#123;</span><br><span class="line">        <span class="comment">// Paranoia</span></span><br><span class="line">        <span class="keyword">return</span>;</span><br><span class="line">    &#125;</span><br><span class="line">    unsafe.freeMemory(address);</span><br><span class="line">    address = <span class="number">0</span>;</span><br><span class="line">    Bits.unreserveMemory(size, capacity);</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
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-  <article itemscope itemtype="http://schema.org/Article" class="post-content" lang="">
-    <link itemprop="mainEntityOfPage" href="https://www.moralok.com/2023/06/13/how-to-configure-proxy-for-terminal-docker-and-container/">
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-      <meta itemprop="name" content="Moralok">
-      <meta itemprop="description" content="假如生命只剩一天">
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-      <meta itemprop="name" content="undefined | Moralok">
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-      <header class="post-header">
-        <h2 class="post-title" itemprop="name headline">
-          <a href="/2023/06/13/how-to-configure-proxy-for-terminal-docker-and-container/" class="post-title-link" itemprop="url">如何为终端、docker 和容器设置代理</a>
-        </h2>
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-      <time title="创建时间：2023-06-13 22:56:11" itemprop="dateCreated datePublished" datetime="2023-06-13T22:56:11+08:00">2023-06-13</time>
-    </span>
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-    </span>
-
-  
-    <span id="/2023/06/13/how-to-configure-proxy-for-terminal-docker-and-container/" class="post-meta-item leancloud_visitors" data-flag-title="如何为终端、docker 和容器设置代理" title="阅读次数">
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-      <span>1.3k</span>
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-    <span class="post-meta-item" title="阅读时长">
-      <span class="post-meta-item-icon">
-        <i class="far fa-clock"></i>
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-      <span class="post-meta-item-text">阅读时长 &asymp;</span>
-      <span>4 分钟</span>
-    </span>
-</div>
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-    <div class="post-body" itemprop="articleBody">
-          <p>在 <a href="/2023/05/27/how-to-install-clash-on-ubuntu/" title="在 Ubuntu 上安装 Clash">Ubuntu 上安装 Clash</a> 后，Clash 通过监听本地的 7890 端口，提供代理服务。但是不同程序设置代理的方式不尽相同，并不是启动了 Clash 以及在某一处设置后，整个系统发出的 HTTP 请求都能经过代理。本文将介绍如何为终端、docker 和容器添加代理。</p>
-<h2 id="为终端设置代理"><a href="#为终端设置代理" class="headerlink" title="为终端设置代理"></a>为终端设置代理</h2><p>有时候，我们需要在终端通过执行命令的方式访问网络和下载资源，比如使用 <code>wget</code> 和 <code>curl</code>。</p>
-<h3 id="设置-Shell-环境变量"><a href="#设置-Shell-环境变量" class="headerlink" title="设置 Shell 环境变量"></a>设置 Shell 环境变量</h3><p>这一类软件都是可以通过为 Shell 设置环境变量的方式来设置代理，涉及到的环境变量有 <code>http_proxy</code>、<code>https_proxy</code> 和 <code>no_proxy</code>。<br>仅为当前会话设置，执行命令：</p>
-<figure class="highlight shell"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line">export http_proxy=http://proxyAddress:port</span><br><span class="line">export https_proxy=http://proxyAddress:port</span><br><span class="line">export no_proxy=localhost,127.0.0.1</span><br></pre></td></tr></table></figure>
-<p>永久设置代理，在设置 Shell 环境变量的脚本中（不同 Shell 的配置文件不同，比如 <code>~/.bashrc</code> 或 <code>~/.zshrc</code>）添加：</p>
-<figure class="highlight shell"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line">export http_proxy=http://proxyAddress:port</span><br><span class="line">export https_proxy=http://proxyAddress:port</span><br><span class="line">export no_proxy=localhost,127.0.0.1</span><br></pre></td></tr></table></figure>
-<p>重新启动一个会话或者执行命令 <code>source ~/.bashrc</code> 使其在当前会话立即生效。</p>
-<h3 id="修改-wget-配置文件"><a href="#修改-wget-配置文件" class="headerlink" title="修改 wget 配置文件"></a>修改 wget 配置文件</h3><p>在搜索过程中发现还可以在 <code>wget</code> 的配置文件 <code>~/.wgetrc</code> 中添加:</p>
-<figure class="highlight shell"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br></pre></td><td class="code"><pre><span class="line">use_proxy = on</span><br><span class="line"></span><br><span class="line">http_proxy = http://proxyAddress:port</span><br><span class="line">https_proxy = http://proxyAddress:port</span><br></pre></td></tr></table></figure>
-
-<h2 id="为-docker-设置代理"><a href="#为-docker-设置代理" class="headerlink" title="为 docker 设置代理"></a>为 docker 设置代理</h2><p>如果你以为为终端设置代理后 docker 就会使用代理，那你就错了。在从官方的镜像仓库 pull 镜像反复出错后并收到类似 <code>Error response from daemon: Get &quot;https://registry-1.docker.io/v2/&quot;: read tcp 192.168.3.140:59460-&gt;44.205.64.79:443: read: connection reset by peer</code> 这样的报错信息后，我才开始怀疑我并没有真正给 docker 设置好代理。<br>在执行 <code>docker pull</code> 命令时，实际上命令是由守护进程 <code>docker daemon</code> 执行的。</p>
-<h3 id="通过-systemd-设置"><a href="#通过-systemd-设置" class="headerlink" title="通过 systemd 设置"></a>通过 systemd 设置</h3><p>如果你的 <code>docker daemon</code> 是通过 <code>systemd</code> 管理的，那么你可以通过设置 <code>docker.service</code> 服务的环境变量来设置代理。<br>执行命令查看 <code>docker.service</code> 信息，得知配置文件位置 <code>/lib/systemd/system/docker.service</code>。</p>
-<figure class="highlight shell"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta prompt_">~$ </span><span class="language-bash">systemctl status docker.service</span> </span><br><span class="line">● docker.service - Docker Application Container Engine</span><br><span class="line">     Loaded: loaded (/lib/systemd/system/docker.service; enabled; vendor preset: enabled)</span><br><span class="line">     Active: active (running) since Tue 2023-06-13 00:52:54 CST; 22h ago</span><br><span class="line">TriggeredBy: ● docker.socket</span><br><span class="line">       Docs: https://docs.docker.com</span><br><span class="line">   Main PID: 387690 (dockerd)</span><br><span class="line">      Tasks: 139</span><br><span class="line">     Memory: 89.6M</span><br><span class="line">        CPU: 1min 26.512s</span><br><span class="line">     CGroup: /system.slice/docker.service</span><br></pre></td></tr></table></figure>
-<p>在 <code>docker.service</code> 的 <code>[Service]</code> 模块添加：</p>
-<figure class="highlight shell"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line">Environment=HTTP_PROXY=http://proxyAddress:port</span><br><span class="line">Environment=HTTPS_PROXY=http://proxyAddress:port</span><br><span class="line">Environment=NO_PROXY=localhost,127.0.0.1</span><br></pre></td></tr></table></figure>
-<p>重新加载配置文件并重启服务：</p>
-<figure class="highlight shell"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line">systemctl daemon-reload</span><br><span class="line">systemctl restart docker.service</span><br></pre></td></tr></table></figure>
-
-<h3 id="修改-dockerd-配置文件"><a href="#修改-dockerd-配置文件" class="headerlink" title="修改 dockerd 配置文件"></a>修改 dockerd 配置文件</h3><p>还可以修改 <code>dockerd</code> 配置文件，添加：</p>
-<figure class="highlight shell"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">export http_proxy=&quot;http://proxyAddress:port&quot;</span><br></pre></td></tr></table></figure>
-<p>然后重启 <code>docker daemon</code> 即可。</p>
-<blockquote>
-<p>国内的镜像仓库在绝大多数时候都可以满足条件，但是存在个别镜像同步不及时的情况，如果使用 latest 标签拉取到的镜像并非近期的镜像，因此有时候需要直接从官方镜像仓库拉取镜像。</p>
-</blockquote>
-<h2 id="为-docker-容器设置代理"><a href="#为-docker-容器设置代理" class="headerlink" title="为 docker 容器设置代理"></a>为 docker 容器设置代理</h2><p>为 <code>docker daemon</code> 进程设置代理和为 docker 容器设置代理是有区别的。比如使用 docker 启动媒体服务器 jellyfin 后，jellyfin 的刮削功能就需要代理才能正常使用，这时候不要因为在很多地方设置过代理就以为容器内部已经在使用代理了。</p>
-<h3 id="修改配置文件"><a href="#修改配置文件" class="headerlink" title="修改配置文件"></a>修改配置文件</h3><p>创建或修改 <code>~/.docker/config.json</code>，添加：</p>
-<figure class="highlight json"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br></pre></td><td class="code"><pre><span class="line"><span class="punctuation">&#123;</span></span><br><span class="line">    <span class="attr">&quot;proxies&quot;</span><span class="punctuation">:</span></span><br><span class="line">    <span class="punctuation">&#123;</span></span><br><span class="line">        <span class="attr">&quot;default&quot;</span><span class="punctuation">:</span></span><br><span class="line">        <span class="punctuation">&#123;</span></span><br><span class="line">            <span class="attr">&quot;httpProxy&quot;</span><span class="punctuation">:</span> <span class="string">&quot;http://proxyAddress:port&quot;</span><span class="punctuation">,</span></span><br><span class="line">            <span class="attr">&quot;httpsProxy&quot;</span><span class="punctuation">:</span> <span class="string">&quot;http://proxyAddress:port&quot;</span><span class="punctuation">,</span></span><br><span class="line">            <span class="attr">&quot;noProxy&quot;</span><span class="punctuation">:</span> <span class="string">&quot;localhost,127.0.0.1&quot;</span></span><br><span class="line">        <span class="punctuation">&#125;</span></span><br><span class="line">    <span class="punctuation">&#125;</span></span><br><span class="line"><span class="punctuation">&#125;</span></span><br></pre></td></tr></table></figure>
-<p>此后创建的新容器，会自动设置环境变量来使用代理。</p>
-<h3 id="为指定容器添加环境变量"><a href="#为指定容器添加环境变量" class="headerlink" title="为指定容器添加环境变量"></a>为指定容器添加环境变量</h3><p>在启动容器时使用 <code>-e</code> 手动注入环境变量 <code>http_proxy</code>。这意味着进入容器使用 <code>export</code> 设置环境变量的方式也是可行的。</p>
-<blockquote>
-<p>注意：如果代理是使用宿主机的代理，当网络为 <code>bridge</code> 模式，proxyAddress 需要填写宿主机的 IP；如果使用 <code>host</code> 模式，proxyAddress 可以填写 127.0.0.1。</p>
-</blockquote>
-<h2 id="总结"><a href="#总结" class="headerlink" title="总结"></a>总结</h2><p>不要因为在很多地方设置过代理，就想当然地以为当前的访问也是经过代理的。每个软件设置代理的方式不尽相同，但是大体上可以归结为：</p>
-<ol>
-<li>使用系统的环境变量</li>
-<li>修改软件的配置文件</li>
-<li>执行时注入参数</li>
-</ol>
-<p>举一反三，像 <code>apt</code> 和 <code>git</code> 这类软件也是有其设置代理的方法。当你的代理稳定但是相应的访问失败时，大胆假设你的代理没有设置成功。要理清楚，当前的访问是谁发起的，才能正确地使用关键词搜索到正确的设置方式。</p>
-<blockquote>
-<p>原本我在 docker 相关的使用中，有关代理的设置方式是通过修改配置文件，实现永久、全局的代理配置。但是在后续的使用中，发现代理在一些场景（比如使用 cloudflare tunnel）中会引起不易排查的问题，决定采用临时、局部的配置方式。</p>
-</blockquote>
-<h2 id="参考链接"><a href="#参考链接" class="headerlink" title="参考链接"></a>参考链接</h2><p><a target="_blank" rel="noopener" href="https://zhuanlan.zhihu.com/p/46973701">Linux 让终端走代理的几种方法</a><br><a target="_blank" rel="noopener" href="https://blog.51cto.com/u_14814563/5415887">Linux ❀ wget设置代理</a><br><a target="_blank" rel="noopener" href="https://cloud-atlas.readthedocs.io/zh_CN/latest/docker/network/docker_proxy.html#docker-server-proxy">配置Docker使用代理</a><br><a target="_blank" rel="noopener" href="https://note.qidong.name/2020/05/docker-proxy/">Docker的三种网络代理配置</a><br><a target="_blank" rel="noopener" href="https://neucrack.com/p/286">docker 设置代理，以及国内加速镜像设置</a></p>
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+    <span title="站点阅读时长">7:09</span>
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   <nav class="site-state">
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@@ -183,6 +183,146 @@ <h1 class="site-title">Moralok</h1>
     
 
 
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+  <article itemscope itemtype="http://schema.org/Article" class="post-content" lang="">
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+          <a href="/2023/06/13/how-to-configure-proxy-for-terminal-docker-and-container/" class="post-title-link" itemprop="url">如何为终端、docker 和容器设置代理</a>
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+    
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+          <p>在 <a href="/2023/05/27/how-to-install-clash-on-ubuntu/" title="在 Ubuntu 上安装 Clash">Ubuntu 上安装 Clash</a> 后，Clash 通过监听本地的 7890 端口，提供代理服务。但是不同程序设置代理的方式不尽相同，并不是启动了 Clash 以及在某一处设置后，整个系统发出的 HTTP 请求都能经过代理。本文将介绍如何为终端、docker 和容器添加代理。</p>
+<h2 id="为终端设置代理"><a href="#为终端设置代理" class="headerlink" title="为终端设置代理"></a>为终端设置代理</h2><p>有时候，我们需要在终端通过执行命令的方式访问网络和下载资源，比如使用 <code>wget</code> 和 <code>curl</code>。</p>
+<h3 id="设置-Shell-环境变量"><a href="#设置-Shell-环境变量" class="headerlink" title="设置 Shell 环境变量"></a>设置 Shell 环境变量</h3><p>这一类软件都是可以通过为 Shell 设置环境变量的方式来设置代理，涉及到的环境变量有 <code>http_proxy</code>、<code>https_proxy</code> 和 <code>no_proxy</code>。<br>仅为当前会话设置，执行命令：</p>
+<figure class="highlight shell"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line">export http_proxy=http://proxyAddress:port</span><br><span class="line">export https_proxy=http://proxyAddress:port</span><br><span class="line">export no_proxy=localhost,127.0.0.1</span><br></pre></td></tr></table></figure>
+<p>永久设置代理，在设置 Shell 环境变量的脚本中（不同 Shell 的配置文件不同，比如 <code>~/.bashrc</code> 或 <code>~/.zshrc</code>）添加：</p>
+<figure class="highlight shell"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line">export http_proxy=http://proxyAddress:port</span><br><span class="line">export https_proxy=http://proxyAddress:port</span><br><span class="line">export no_proxy=localhost,127.0.0.1</span><br></pre></td></tr></table></figure>
+<p>重新启动一个会话或者执行命令 <code>source ~/.bashrc</code> 使其在当前会话立即生效。</p>
+<h3 id="修改-wget-配置文件"><a href="#修改-wget-配置文件" class="headerlink" title="修改 wget 配置文件"></a>修改 wget 配置文件</h3><p>在搜索过程中发现还可以在 <code>wget</code> 的配置文件 <code>~/.wgetrc</code> 中添加:</p>
+<figure class="highlight shell"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br></pre></td><td class="code"><pre><span class="line">use_proxy = on</span><br><span class="line"></span><br><span class="line">http_proxy = http://proxyAddress:port</span><br><span class="line">https_proxy = http://proxyAddress:port</span><br></pre></td></tr></table></figure>
+
+<h2 id="为-docker-设置代理"><a href="#为-docker-设置代理" class="headerlink" title="为 docker 设置代理"></a>为 docker 设置代理</h2><p>如果你以为为终端设置代理后 docker 就会使用代理，那你就错了。在从官方的镜像仓库 pull 镜像反复出错后并收到类似 <code>Error response from daemon: Get &quot;https://registry-1.docker.io/v2/&quot;: read tcp 192.168.3.140:59460-&gt;44.205.64.79:443: read: connection reset by peer</code> 这样的报错信息后，我才开始怀疑我并没有真正给 docker 设置好代理。<br>在执行 <code>docker pull</code> 命令时，实际上命令是由守护进程 <code>docker daemon</code> 执行的。</p>
+<h3 id="通过-systemd-设置"><a href="#通过-systemd-设置" class="headerlink" title="通过 systemd 设置"></a>通过 systemd 设置</h3><p>如果你的 <code>docker daemon</code> 是通过 <code>systemd</code> 管理的，那么你可以通过设置 <code>docker.service</code> 服务的环境变量来设置代理。<br>执行命令查看 <code>docker.service</code> 信息，得知配置文件位置 <code>/lib/systemd/system/docker.service</code>。</p>
+<figure class="highlight shell"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta prompt_">~$ </span><span class="language-bash">systemctl status docker.service</span> </span><br><span class="line">● docker.service - Docker Application Container Engine</span><br><span class="line">     Loaded: loaded (/lib/systemd/system/docker.service; enabled; vendor preset: enabled)</span><br><span class="line">     Active: active (running) since Tue 2023-06-13 00:52:54 CST; 22h ago</span><br><span class="line">TriggeredBy: ● docker.socket</span><br><span class="line">       Docs: https://docs.docker.com</span><br><span class="line">   Main PID: 387690 (dockerd)</span><br><span class="line">      Tasks: 139</span><br><span class="line">     Memory: 89.6M</span><br><span class="line">        CPU: 1min 26.512s</span><br><span class="line">     CGroup: /system.slice/docker.service</span><br></pre></td></tr></table></figure>
+<p>在 <code>docker.service</code> 的 <code>[Service]</code> 模块添加：</p>
+<figure class="highlight shell"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line">Environment=HTTP_PROXY=http://proxyAddress:port</span><br><span class="line">Environment=HTTPS_PROXY=http://proxyAddress:port</span><br><span class="line">Environment=NO_PROXY=localhost,127.0.0.1</span><br></pre></td></tr></table></figure>
+<p>重新加载配置文件并重启服务：</p>
+<figure class="highlight shell"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line">systemctl daemon-reload</span><br><span class="line">systemctl restart docker.service</span><br></pre></td></tr></table></figure>
+
+<h3 id="修改-dockerd-配置文件"><a href="#修改-dockerd-配置文件" class="headerlink" title="修改 dockerd 配置文件"></a>修改 dockerd 配置文件</h3><p>还可以修改 <code>dockerd</code> 配置文件，添加：</p>
+<figure class="highlight shell"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">export http_proxy=&quot;http://proxyAddress:port&quot;</span><br></pre></td></tr></table></figure>
+<p>然后重启 <code>docker daemon</code> 即可。</p>
+<blockquote>
+<p>国内的镜像仓库在绝大多数时候都可以满足条件，但是存在个别镜像同步不及时的情况，如果使用 latest 标签拉取到的镜像并非近期的镜像，因此有时候需要直接从官方镜像仓库拉取镜像。</p>
+</blockquote>
+<h2 id="为-docker-容器设置代理"><a href="#为-docker-容器设置代理" class="headerlink" title="为 docker 容器设置代理"></a>为 docker 容器设置代理</h2><p>为 <code>docker daemon</code> 进程设置代理和为 docker 容器设置代理是有区别的。比如使用 docker 启动媒体服务器 jellyfin 后，jellyfin 的刮削功能就需要代理才能正常使用，这时候不要因为在很多地方设置过代理就以为容器内部已经在使用代理了。</p>
+<h3 id="修改配置文件"><a href="#修改配置文件" class="headerlink" title="修改配置文件"></a>修改配置文件</h3><p>创建或修改 <code>~/.docker/config.json</code>，添加：</p>
+<figure class="highlight json"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br></pre></td><td class="code"><pre><span class="line"><span class="punctuation">&#123;</span></span><br><span class="line">    <span class="attr">&quot;proxies&quot;</span><span class="punctuation">:</span></span><br><span class="line">    <span class="punctuation">&#123;</span></span><br><span class="line">        <span class="attr">&quot;default&quot;</span><span class="punctuation">:</span></span><br><span class="line">        <span class="punctuation">&#123;</span></span><br><span class="line">            <span class="attr">&quot;httpProxy&quot;</span><span class="punctuation">:</span> <span class="string">&quot;http://proxyAddress:port&quot;</span><span class="punctuation">,</span></span><br><span class="line">            <span class="attr">&quot;httpsProxy&quot;</span><span class="punctuation">:</span> <span class="string">&quot;http://proxyAddress:port&quot;</span><span class="punctuation">,</span></span><br><span class="line">            <span class="attr">&quot;noProxy&quot;</span><span class="punctuation">:</span> <span class="string">&quot;localhost,127.0.0.1&quot;</span></span><br><span class="line">        <span class="punctuation">&#125;</span></span><br><span class="line">    <span class="punctuation">&#125;</span></span><br><span class="line"><span class="punctuation">&#125;</span></span><br></pre></td></tr></table></figure>
+<p>此后创建的新容器，会自动设置环境变量来使用代理。</p>
+<h3 id="为指定容器添加环境变量"><a href="#为指定容器添加环境变量" class="headerlink" title="为指定容器添加环境变量"></a>为指定容器添加环境变量</h3><p>在启动容器时使用 <code>-e</code> 手动注入环境变量 <code>http_proxy</code>。这意味着进入容器使用 <code>export</code> 设置环境变量的方式也是可行的。</p>
+<blockquote>
+<p>注意：如果代理是使用宿主机的代理，当网络为 <code>bridge</code> 模式，proxyAddress 需要填写宿主机的 IP；如果使用 <code>host</code> 模式，proxyAddress 可以填写 127.0.0.1。</p>
+</blockquote>
+<h2 id="总结"><a href="#总结" class="headerlink" title="总结"></a>总结</h2><p>不要因为在很多地方设置过代理，就想当然地以为当前的访问也是经过代理的。每个软件设置代理的方式不尽相同，但是大体上可以归结为：</p>
+<ol>
+<li>使用系统的环境变量</li>
+<li>修改软件的配置文件</li>
+<li>执行时注入参数</li>
+</ol>
+<p>举一反三，像 <code>apt</code> 和 <code>git</code> 这类软件也是有其设置代理的方法。当你的代理稳定但是相应的访问失败时，大胆假设你的代理没有设置成功。要理清楚，当前的访问是谁发起的，才能正确地使用关键词搜索到正确的设置方式。</p>
+<blockquote>
+<p>原本我在 docker 相关的使用中，有关代理的设置方式是通过修改配置文件，实现永久、全局的代理配置。但是在后续的使用中，发现代理在一些场景（比如使用 cloudflare tunnel）中会引起不易排查的问题，决定采用临时、局部的配置方式。</p>
+</blockquote>
+<h2 id="参考链接"><a href="#参考链接" class="headerlink" title="参考链接"></a>参考链接</h2><p><a target="_blank" rel="noopener" href="https://zhuanlan.zhihu.com/p/46973701">Linux 让终端走代理的几种方法</a><br><a target="_blank" rel="noopener" href="https://blog.51cto.com/u_14814563/5415887">Linux ❀ wget设置代理</a><br><a target="_blank" rel="noopener" href="https://cloud-atlas.readthedocs.io/zh_CN/latest/docker/network/docker_proxy.html#docker-server-proxy">配置Docker使用代理</a><br><a target="_blank" rel="noopener" href="https://note.qidong.name/2020/05/docker-proxy/">Docker的三种网络代理配置</a><br><a target="_blank" rel="noopener" href="https://neucrack.com/p/286">docker 设置代理，以及国内加速镜像设置</a></p>
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diff --git a/search.xml b/search.xml
index aa0026ea..28d5187e 100644
--- a/search.xml
+++ b/search.xml
@@ -924,59 +924,6 @@
         <tag>linux</tag>
       </tags>
   </entry>
-  <entry>
-    <title>在 Ubuntu 上安装 Clash</title>
-    <url>/2023/05/27/how-to-install-clash-on-ubuntu/</url>
-    <content><![CDATA[<p>本文记录了如何在 <code>Ubuntu</code> 上安装 <code>Clash</code>，以供各类程序在必要的时候使用代理。<br>有些时候我们面对特定资源会遇到下载速度极其缓慢甚至无法下载的情况，像是使用 <code>Github</code>，下载 <code>k8s</code> 相关镜像，还有访问特定网站等等。也许有些 Dirty Hack 的方式可以短暂地绕开限制，比如修改 <code>hosts</code> 文件，但这并不总是见效。也许添加国内的镜像仓库地址可以满足很多人的需求，但是说不准就会遇到镜像更新不及时甚至镜像被污染的情况。总之，如果你有一把不错的梯子，使用代理辅助开发肯定会拥有更好的体验。<br>当然，为 <code>Git</code> 设置代理，为 <code>Terminal</code> 设置代理，为 <code>Docker Engine</code> 设置代理，为 <code>Docker</code> 容器设置代理，为 <strong>“还有一些你尚未知道原来这还需要这样设置代理的地方”</strong> 设置代理，仍然是一件痛苦的事情。如果你有条件为全屋设备配置透明代理，肯定能避免踩非常多的坑。</p>
-<span id="more"></span>
-
-<blockquote>
-<p><strong>注意：多个 <code>Clash</code> 相关的仓库已经 GG</strong><br><strong>请谨慎甄别网上搜索到的所谓备份的可靠性和安全性！！！</strong><br><strong>请谨慎甄别网上搜索到的所谓备份的可靠性和安全性！！！</strong><br><strong>请谨慎甄别网上搜索到的所谓备份的可靠性和安全性！！！</strong></p>
-</blockquote>
-<hr>
-<h2 id="通过-Docker-运行-Clash"><a href="#通过-Docker-运行-Clash" class="headerlink" title="通过 Docker 运行 Clash"></a>通过 Docker 运行 Clash</h2><blockquote>
-<p>本人最新的安装是通过直接拷贝旧服务器上的二进制可执行文件以及全球 <code>IP</code> 库文件来完成的，保留已有安装的相关文件在短时间内仍然可以满足重新安装的需求。<strong>注意到原作者 <code>Dreamacro</code> 的 <code>Docker</code> 镜像仓库仍然保留，也许通过 <code>Docker</code> 运行 <code>Clash</code> 是个更好的选择</strong>。</p>
-</blockquote>
-<ul>
-<li><code>docker-compose.yml</code><figure class="highlight yaml"><table><tr><td class="code"><pre><span class="line"><span class="attr">version:</span> <span class="string">&quot;1.0&quot;</span></span><br><span class="line"><span class="attr">services:</span></span><br><span class="line">  <span class="attr">clash:</span></span><br><span class="line">    <span class="attr">image:</span> <span class="string">dreamacro/clash:v1.18.0</span></span><br><span class="line">    <span class="attr">container_name:</span> <span class="string">clash</span></span><br><span class="line">    <span class="attr">ports:</span></span><br><span class="line">      <span class="bullet">-</span> <span class="number">9090</span><span class="string">:9090</span></span><br><span class="line">      <span class="bullet">-</span> <span class="number">7890</span><span class="string">:7890</span></span><br><span class="line">    <span class="attr">mem_limit:</span> <span class="string">$&#123;CLASH_MEM_LIMIT:-64m&#125;</span></span><br><span class="line">    <span class="attr">restart:</span> <span class="string">unless-stopped</span></span><br></pre></td></tr></table></figure></li>
-<li>配置文件在容器内的位置 <code>/root/.config/clash/config.yaml</code></li>
-</ul>
-<blockquote>
-<p>长远来看，使用无法得到更新的旧版本仍然可能在未来导致安全问题的发生，以后再说吧 &#x3D;_&#x3D;。</p>
-</blockquote>
-<hr>
-<h2 id="二进制安装-Clash"><a href="#二进制安装-Clash" class="headerlink" title="二进制安装 Clash"></a>二进制安装 Clash</h2><blockquote>
-<p>本方式仅限仍然可获得可靠安全的二进制可执行文件的人使用。</p>
-</blockquote>
-<h3 id="安装-Clash"><a href="#安装-Clash" class="headerlink" title="安装 Clash"></a>安装 Clash</h3><ol>
-<li><del>从 <a href="https://github.com/Dreamacro/clash/releases">GitHub</a> 下载预构建的二进制文件。</del>（ <strong>仓库已删除</strong> ）<figure class="highlight shell"><table><tr><td class="code"><pre><span class="line"><span class="meta prompt_">$ </span><span class="language-bash">wget https://github.com/Dreamacro/clash/releases/download/v1.16.0/clash-linux-amd64-v1.16.0.gz</span></span><br></pre></td></tr></table></figure></li>
-<li>使用 <code>gzip</code> 解压压缩包 <code>clash-linux-amd64-v1.16.0.gz</code> 得到 <code>clash-linux-amd64-v1.16.0</code>。忽略提示。<figure class="highlight shell"><table><tr><td class="code"><pre><span class="line"><span class="meta prompt_">$ </span><span class="language-bash">gzip -d clash-linux-amd64-v1.16.0.gz</span> </span><br><span class="line">gzip: clash-linux-amd64-v1.16.0: Value too large for defined data type</span><br></pre></td></tr></table></figure></li>
-<li>移动二进制文件到目录 <code>/usr/local/bin</code> 并且重命名为 <code>clash</code>。<figure class="highlight shell"><table><tr><td class="code"><pre><span class="line"><span class="meta prompt_">$ </span><span class="language-bash">sudo <span class="built_in">mv</span> clash-linux-amd64-v1.16.0 /usr/local/bin/clash</span></span><br></pre></td></tr></table></figure></li>
-<li>通过 <code>clash -v</code> 查看 <code>Clash</code> 的版本信息。<figure class="highlight shell"><table><tr><td class="code"><pre><span class="line"><span class="meta prompt_">$ </span><span class="language-bash">clash -v</span></span><br><span class="line">Clash v1.16.0 linux amd64 with go1.20.4 Fri May 19 13:57:32 UTC 2023</span><br></pre></td></tr></table></figure></li>
-</ol>
-<h3 id="使用-Clash"><a href="#使用-Clash" class="headerlink" title="使用 Clash"></a>使用 Clash</h3><ol>
-<li>使用命令 <code>clash</code> 启动，可以看到日志。<figure class="highlight shell"><table><tr><td class="code"><pre><span class="line">:~$ clash</span><br><span class="line">INFO[0000] Can&#x27;t find config, create a initial config file </span><br><span class="line">INFO[0000] Can&#x27;t find MMDB, start download              </span><br><span class="line">INFO[0003] Mixed(http+socks) proxy listening at: 127.0.0.1:7890</span><br></pre></td></tr></table></figure></li>
-<li><del>在第一次启动 <code>Clash</code> 时，<code>Clash</code> 会在 <code>~/.config</code> 下创建目录 <code>clash</code>，并在其中创建 <code>3</code> 个文件。其中 <code>config.yaml</code> 是 <code>Clash</code> 的配置文件，<code>Country.mmdb</code> 是全球 <code>IP</code> 库，可以实现各个国家的 <code>IP</code> 信息解析和地理定位。<code>cache.db</code> 用于缓存。</del>（ <strong><code>CDN</code> 已失效</strong> ）<figure class="highlight shell"><table><tr><td class="code"><pre><span class="line">:~/.config/clash$ ls</span><br><span class="line">cache.db  config.yaml  Country.mmdb</span><br></pre></td></tr></table></figure></li>
-<li>如果梯子的订阅支持 <code>Clash</code>，直接订阅；否则需要手动修改配置文件。</li>
-<li>可以浏览器访问 <a href="http://clash.razord.top/#/proxies">http://clash.razord.top/#/proxies</a> 选择代理服务器。（ <strong>注意：使用 <code>http</code></strong> ）</li>
-</ol>
-<h3 id="设置-Clash-开机自动启动"><a href="#设置-Clash-开机自动启动" class="headerlink" title="设置 Clash 开机自动启动"></a>设置 Clash 开机自动启动</h3><blockquote>
-<p><del>参考官方文档 <a href="https://dreamacro.github.io/clash/introduction/service.html">Clash as a service</a>。</del>（ <strong>已 <code>404</code></strong> ）</p>
-</blockquote>
-<ol>
-<li>拷贝配置文件和全球 <code>IP</code> 库到 <code>/etc/clash</code><figure class="highlight shell"><table><tr><td class="code"><pre><span class="line">~/.config/clash$ sudo cp config.yaml /etc/clash/</span><br><span class="line">~/.config/clash$ sudo cp Country.mmdb /etc/clash/</span><br></pre></td></tr></table></figure></li>
-<li>在 <code>/etc/systemd/system/clash.service</code> 创建 <code>systemd</code> 配置文件<figure class="highlight shell"><table><tr><td class="code"><pre><span class="line">[Unit]</span><br><span class="line">Description=Clash daemon, A rule-based proxy in Go.</span><br><span class="line">After=network-online.target</span><br><span class="line"></span><br><span class="line">[Service]</span><br><span class="line">Type=simple</span><br><span class="line">Restart=always </span><br><span class="line">ExecStart=/usr/local/bin/clash -d /etc/clash</span><br><span class="line"></span><br><span class="line">[Install]</span><br><span class="line">WantedBy=multi-user.target</span><br></pre></td></tr></table></figure></li>
-<li>重载 <code>systemd</code><figure class="highlight shell"><table><tr><td class="code"><pre><span class="line">systemctl daemon-reload</span><br></pre></td></tr></table></figure></li>
-<li>设置系统开机时自动启动 <code>Clash</code><figure class="highlight shell"><table><tr><td class="code"><pre><span class="line">systemctl enable clash</span><br></pre></td></tr></table></figure></li>
-<li>启动 <code>Clash</code><figure class="highlight shell"><table><tr><td class="code"><pre><span class="line">systemctl start clash</span><br></pre></td></tr></table></figure></li>
-<li>检查 <code>Clash</code> 的健康状态和日志<figure class="highlight shell"><table><tr><td class="code"><pre><span class="line">systemctl status clash</span><br><span class="line">journalctl -xe</span><br></pre></td></tr></table></figure></li>
-</ol>
-]]></content>
-      <tags>
-        <tag>clash</tag>
-        <tag>proxy</tag>
-      </tags>
-  </entry>
   <entry>
     <title>MySQL 常用命令</title>
     <url>/2020/09/04/MySQL-frequently-used-commands/</url>
@@ -1248,50 +1195,6 @@
         <tag>mysql</tag>
       </tags>
   </entry>
-  <entry>
-    <title>在 Windows 10 上安装 OpenVPN 服务端</title>
-    <url>/2023/06/07/how-to-setup-OpenVPN-server-on-windows-10/</url>
-    <content><![CDATA[<p>本文记录了如何在 <code>Windows 10</code> 上安装和配置 <code>OpenVPN</code> 服务端。</p>
-<span id="more"></span>
-
-<ul>
-<li>客户端的安装：<a href="/2023/06/07/how-to-setup-OpenVPN-connect-client-on-iOS-and-macOS/" title="在 iOS 和 macOS 上安装 OpenVPN 客户端">在 iOS 和 macOS 上安装 OpenVPN 客户端</a></li>
-<li>主要目的：<a href="/2023/06/07/how-to-use-OpenVPN-to-access-home-network/" title="使用 OpenVPN 访问家庭内网">使用 OpenVPN 访问家庭内网</a></li>
-</ul>
-<h2 id="环境"><a href="#环境" class="headerlink" title="环境"></a>环境</h2><ul>
-<li><code>Windows 10</code> 专业版</li>
-<li><code>OpenVPN 2.6.4</code></li>
-<li>拥有动态公网 <code>IP</code></li>
-</ul>
-<h2 id="安装-OpenVPN-server"><a href="#安装-OpenVPN-server" class="headerlink" title="安装 OpenVPN server"></a>安装 OpenVPN server</h2><ol>
-<li>从 <a href="https://openvpn.net/community-downloads/">OpenVPN 社区</a> 下载 <code>Windows 64-bit MSI installer</code>。本次安装的版本为 <code>OpenVPN 2.6.4</code>。</li>
-<li>在选择安装类型时，选择 <code>Customize</code> 而不要选择 <code>Install Now</code>。<ul>
-<li>勾选 <code>OpenVPN -&gt; OpenVPN Service -&gt; Entire feature will be installed on local hard drive</code>；</li>
-<li>勾选 <code>OpenSSL Utilities -&gt; EasyRSA 3 Certificate Management Scripts -&gt; Entire feature will be installed on local hard drive</code>；</li>
-</ul>
-</li>
-<li>安装完毕后，会弹出一条消息提示未找到可读的连接配置文件，暂时忽略。此时在“控制面板\网络和 Internet\网络连接”中可以看到创建了两个新的网络适配器 <code>OpenVPN TAP-Windows6</code> 和 <code>OpenVPN Wintun</code>。</li>
-</ol>
-<h2 id="配置-OpenVPN-server"><a href="#配置-OpenVPN-server" class="headerlink" title="配置 OpenVPN server"></a>配置 OpenVPN server</h2><ol>
-<li>打开 <code>Windows 10</code> 终端程序。</li>
-<li>进入 <code>OpenVPN</code> 默认安装目录中的 <code>easy-rsa</code> 目录。<figure class="highlight shell"><table><tr><td class="code"><pre><span class="line">cd &#x27;C:\Program Files\OpenVPN\easy-rsa&#x27;</span><br></pre></td></tr></table></figure></li>
-<li>执行命令进入 <code>Easy-RSA 3 Shell</code>。<figure class="highlight shell"><table><tr><td class="code"><pre><span class="line">.\EasyRSA-Start.bat</span><br></pre></td></tr></table></figure></li>
-<li>初始化公钥基础设施目录 <code>pki</code>。<figure class="highlight shell"><table><tr><td class="code"><pre><span class="line">./easyrsa init-pki</span><br></pre></td></tr></table></figure></li>
-<li>构建证书颁发机构（<code>CA</code>）密钥，<code>CA</code> 根证书文件将在后续用于对其他证书和密钥进行签名。该命令要求输入 <code>Common Name</code>，输入主机名即可。创建的 <code>ca.crt</code> 保存在目录 <code>C：\Program Files\OpenVPN\easy-rsa\pki</code> 中，<code>ca.key</code> 保存在目录 <code>C：\Program Files\OpenVPN\easy-rsa\pki\private</code> 中。<figure class="highlight shell"><table><tr><td class="code"><pre><span class="line">./easyrsa build-ca nopass</span><br></pre></td></tr></table></figure></li>
-<li>构建服务器证书和密钥。创建的 <code>server.crt</code> 保存在目录 <code>C：\Program Files\OpenVPN\easy-rsa\pki\issued</code> 中，<code>server.key</code> 保存在目录 <code>C：\Program Files\OpenVPN\easy-rsa\pki\private</code> 中。<figure class="highlight shell"><table><tr><td class="code"><pre><span class="line">./easyrsa build-server-full server nopass</span><br></pre></td></tr></table></figure></li>
-<li>构建客户端证书和密钥。创建的 <code>client.crt</code> 保存在目录 <code>C：\Program Files\OpenVPN\easy-rsa\pki\issued</code> 中，<code>client.key</code> 保存在目录 <code>C：\Program Files\OpenVPN\easy-rsa\pki\private</code> 中。<figure class="highlight shell"><table><tr><td class="code"><pre><span class="line">./easyrsa build-client-full client nopass</span><br></pre></td></tr></table></figure></li>
-<li>生成 <code>Diffie-Hellman</code> 参数<figure class="highlight shell"><table><tr><td class="code"><pre><span class="line">./easyrsa gen-dh</span><br></pre></td></tr></table></figure></li>
-<li>从目录 <code>C：\Program Files\OpenVPN\sample-config</code> 复制服务端配置文件模板 <code>server.ovpn</code> 到目录 <code>C：\Program Files\OpenVPN\config</code> 中，修改以下配置：端口号按需修改，默认为 <code>1194</code>，需要保证 <code>OpenVPN</code> 的网络流量可以通过防火墙，设置 <code>Windows 10 Defender</code> 允许 <code>OpenVPN</code> 通过即可。<code>dh2048.pem</code> 修改为生成的文件名 <code>dh.pem</code>。取消注释 <code>duplicate-cn</code>，让多个客户端使用同一个客户端证书。注释掉 <code>tls-auth ta.key 0</code>。<figure class="highlight ini"><table><tr><td class="code"><pre><span class="line">port 1194</span><br><span class="line">dh dh.pem</span><br><span class="line">duplicate-cn</span><br><span class="line"><span class="comment">;tls-auth ta.key 0</span></span><br></pre></td></tr></table></figure></li>
-<li>复制 <code>ca.crt</code>，<code>dh.pem</code>，<code>server.crt</code> 和 <code>server.key</code> 到目录 <code>C：\Program Files\OpenVPN\config</code> 中。</li>
-</ol>
-<h2 id="启动与连接"><a href="#启动与连接" class="headerlink" title="启动与连接"></a>启动与连接</h2><p>启动 <code>OpenVPN</code>，点击连接，系统提示分配 <code>IP</code> 为 <code>10.8.0.1</code>。按配置，每次 <code>OpenVPN server</code> 都将为自己分配 <code>10.8.0.1</code>。</p>
-<h2 id="参考链接"><a href="#参考链接" class="headerlink" title="参考链接"></a>参考链接</h2><p><a href="https://blog.eyyyye.com/article/39#menu_3">openvpn安装配置说明(windows系统)</a><br><a href="https://zhuanlan.zhihu.com/p/525197398">如何在Windows 10上安装和配置OpenVPN</a></p>
-]]></content>
-      <tags>
-        <tag>proxy</tag>
-        <tag>openvpn</tag>
-      </tags>
-  </entry>
   <entry>
     <title>在 iOS 和 macOS 上安装 OpenVPN 客户端</title>
     <url>/2023/06/07/how-to-setup-OpenVPN-connect-client-on-iOS-and-macOS/</url>
@@ -1347,10 +1250,107 @@
 <li><a href="https://openvpn.net/faq/how-do-i-use-a-client-certificate-and-private-key-from-the-ios-keychain/">如何通过 iOS Keychain 使用客户端证书和密钥</a></li>
 <li><a href="https://help.endian.com/hc/en-us/articles/360008350974-How-to-configure-iOS-OpenVPN-client-with-certificate-authentication">如何配置 iOS OpenVPN 客户端的证书认证</a></li>
 </ul>
+]]></content>
+      <tags>
+        <tag>openvpn</tag>
+        <tag>proxy</tag>
+      </tags>
+  </entry>
+  <entry>
+    <title>在 Ubuntu 上安装 Clash</title>
+    <url>/2023/05/27/how-to-install-clash-on-ubuntu/</url>
+    <content><![CDATA[<p>本文记录了如何在 <code>Ubuntu</code> 上安装 <code>Clash</code>，以供各类程序在必要的时候使用代理。<br>有些时候我们面对特定资源会遇到下载速度极其缓慢甚至无法下载的情况，像是使用 <code>Github</code>，下载 <code>k8s</code> 相关镜像，还有访问特定网站等等。也许有些 Dirty Hack 的方式可以短暂地绕开限制，比如修改 <code>hosts</code> 文件，但这并不总是见效。也许添加国内的镜像仓库地址可以满足很多人的需求，但是说不准就会遇到镜像更新不及时甚至镜像被污染的情况。总之，如果你有一把不错的梯子，使用代理辅助开发肯定会拥有更好的体验。<br>当然，为 <code>Git</code> 设置代理，为 <code>Terminal</code> 设置代理，为 <code>Docker Engine</code> 设置代理，为 <code>Docker</code> 容器设置代理，为 <strong>“还有一些你尚未知道原来这还需要这样设置代理的地方”</strong> 设置代理，仍然是一件痛苦的事情。如果你有条件为全屋设备配置透明代理，肯定能避免踩非常多的坑。</p>
+<span id="more"></span>
+
+<blockquote>
+<p><strong>注意：多个 <code>Clash</code> 相关的仓库已经 GG</strong><br><strong>请谨慎甄别网上搜索到的所谓备份的可靠性和安全性！！！</strong><br><strong>请谨慎甄别网上搜索到的所谓备份的可靠性和安全性！！！</strong><br><strong>请谨慎甄别网上搜索到的所谓备份的可靠性和安全性！！！</strong></p>
+</blockquote>
+<hr>
+<h2 id="通过-Docker-运行-Clash"><a href="#通过-Docker-运行-Clash" class="headerlink" title="通过 Docker 运行 Clash"></a>通过 Docker 运行 Clash</h2><blockquote>
+<p>本人最新的安装是通过直接拷贝旧服务器上的二进制可执行文件以及全球 <code>IP</code> 库文件来完成的，保留已有安装的相关文件在短时间内仍然可以满足重新安装的需求。<strong>注意到原作者 <code>Dreamacro</code> 的 <code>Docker</code> 镜像仓库仍然保留，也许通过 <code>Docker</code> 运行 <code>Clash</code> 是个更好的选择</strong>。</p>
+</blockquote>
+<ul>
+<li><code>docker-compose.yml</code><figure class="highlight yaml"><table><tr><td class="code"><pre><span class="line"><span class="attr">version:</span> <span class="string">&quot;1.0&quot;</span></span><br><span class="line"><span class="attr">services:</span></span><br><span class="line">  <span class="attr">clash:</span></span><br><span class="line">    <span class="attr">image:</span> <span class="string">dreamacro/clash:v1.18.0</span></span><br><span class="line">    <span class="attr">container_name:</span> <span class="string">clash</span></span><br><span class="line">    <span class="attr">ports:</span></span><br><span class="line">      <span class="bullet">-</span> <span class="number">9090</span><span class="string">:9090</span></span><br><span class="line">      <span class="bullet">-</span> <span class="number">7890</span><span class="string">:7890</span></span><br><span class="line">    <span class="attr">mem_limit:</span> <span class="string">$&#123;CLASH_MEM_LIMIT:-64m&#125;</span></span><br><span class="line">    <span class="attr">restart:</span> <span class="string">unless-stopped</span></span><br></pre></td></tr></table></figure></li>
+<li>配置文件在容器内的位置 <code>/root/.config/clash/config.yaml</code></li>
+</ul>
+<blockquote>
+<p>长远来看，使用无法得到更新的旧版本仍然可能在未来导致安全问题的发生，以后再说吧 &#x3D;_&#x3D;。</p>
+</blockquote>
+<hr>
+<h2 id="二进制安装-Clash"><a href="#二进制安装-Clash" class="headerlink" title="二进制安装 Clash"></a>二进制安装 Clash</h2><blockquote>
+<p>本方式仅限仍然可获得可靠安全的二进制可执行文件的人使用。</p>
+</blockquote>
+<h3 id="安装-Clash"><a href="#安装-Clash" class="headerlink" title="安装 Clash"></a>安装 Clash</h3><ol>
+<li><del>从 <a href="https://github.com/Dreamacro/clash/releases">GitHub</a> 下载预构建的二进制文件。</del>（ <strong>仓库已删除</strong> ）<figure class="highlight shell"><table><tr><td class="code"><pre><span class="line"><span class="meta prompt_">$ </span><span class="language-bash">wget https://github.com/Dreamacro/clash/releases/download/v1.16.0/clash-linux-amd64-v1.16.0.gz</span></span><br></pre></td></tr></table></figure></li>
+<li>使用 <code>gzip</code> 解压压缩包 <code>clash-linux-amd64-v1.16.0.gz</code> 得到 <code>clash-linux-amd64-v1.16.0</code>。忽略提示。<figure class="highlight shell"><table><tr><td class="code"><pre><span class="line"><span class="meta prompt_">$ </span><span class="language-bash">gzip -d clash-linux-amd64-v1.16.0.gz</span> </span><br><span class="line">gzip: clash-linux-amd64-v1.16.0: Value too large for defined data type</span><br></pre></td></tr></table></figure></li>
+<li>移动二进制文件到目录 <code>/usr/local/bin</code> 并且重命名为 <code>clash</code>。<figure class="highlight shell"><table><tr><td class="code"><pre><span class="line"><span class="meta prompt_">$ </span><span class="language-bash">sudo <span class="built_in">mv</span> clash-linux-amd64-v1.16.0 /usr/local/bin/clash</span></span><br></pre></td></tr></table></figure></li>
+<li>通过 <code>clash -v</code> 查看 <code>Clash</code> 的版本信息。<figure class="highlight shell"><table><tr><td class="code"><pre><span class="line"><span class="meta prompt_">$ </span><span class="language-bash">clash -v</span></span><br><span class="line">Clash v1.16.0 linux amd64 with go1.20.4 Fri May 19 13:57:32 UTC 2023</span><br></pre></td></tr></table></figure></li>
+</ol>
+<h3 id="使用-Clash"><a href="#使用-Clash" class="headerlink" title="使用 Clash"></a>使用 Clash</h3><ol>
+<li>使用命令 <code>clash</code> 启动，可以看到日志。<figure class="highlight shell"><table><tr><td class="code"><pre><span class="line">:~$ clash</span><br><span class="line">INFO[0000] Can&#x27;t find config, create a initial config file </span><br><span class="line">INFO[0000] Can&#x27;t find MMDB, start download              </span><br><span class="line">INFO[0003] Mixed(http+socks) proxy listening at: 127.0.0.1:7890</span><br></pre></td></tr></table></figure></li>
+<li><del>在第一次启动 <code>Clash</code> 时，<code>Clash</code> 会在 <code>~/.config</code> 下创建目录 <code>clash</code>，并在其中创建 <code>3</code> 个文件。其中 <code>config.yaml</code> 是 <code>Clash</code> 的配置文件，<code>Country.mmdb</code> 是全球 <code>IP</code> 库，可以实现各个国家的 <code>IP</code> 信息解析和地理定位。<code>cache.db</code> 用于缓存。</del>（ <strong><code>CDN</code> 已失效</strong> ）<figure class="highlight shell"><table><tr><td class="code"><pre><span class="line">:~/.config/clash$ ls</span><br><span class="line">cache.db  config.yaml  Country.mmdb</span><br></pre></td></tr></table></figure></li>
+<li>如果梯子的订阅支持 <code>Clash</code>，直接订阅；否则需要手动修改配置文件。</li>
+<li>可以浏览器访问 <a href="http://clash.razord.top/#/proxies">http://clash.razord.top/#/proxies</a> 选择代理服务器。（ <strong>注意：使用 <code>http</code></strong> ）</li>
+</ol>
+<h3 id="设置-Clash-开机自动启动"><a href="#设置-Clash-开机自动启动" class="headerlink" title="设置 Clash 开机自动启动"></a>设置 Clash 开机自动启动</h3><blockquote>
+<p><del>参考官方文档 <a href="https://dreamacro.github.io/clash/introduction/service.html">Clash as a service</a>。</del>（ <strong>已 <code>404</code></strong> ）</p>
+</blockquote>
+<ol>
+<li>拷贝配置文件和全球 <code>IP</code> 库到 <code>/etc/clash</code><figure class="highlight shell"><table><tr><td class="code"><pre><span class="line">~/.config/clash$ sudo cp config.yaml /etc/clash/</span><br><span class="line">~/.config/clash$ sudo cp Country.mmdb /etc/clash/</span><br></pre></td></tr></table></figure></li>
+<li>在 <code>/etc/systemd/system/clash.service</code> 创建 <code>systemd</code> 配置文件<figure class="highlight shell"><table><tr><td class="code"><pre><span class="line">[Unit]</span><br><span class="line">Description=Clash daemon, A rule-based proxy in Go.</span><br><span class="line">After=network-online.target</span><br><span class="line"></span><br><span class="line">[Service]</span><br><span class="line">Type=simple</span><br><span class="line">Restart=always </span><br><span class="line">ExecStart=/usr/local/bin/clash -d /etc/clash</span><br><span class="line"></span><br><span class="line">[Install]</span><br><span class="line">WantedBy=multi-user.target</span><br></pre></td></tr></table></figure></li>
+<li>重载 <code>systemd</code><figure class="highlight shell"><table><tr><td class="code"><pre><span class="line">systemctl daemon-reload</span><br></pre></td></tr></table></figure></li>
+<li>设置系统开机时自动启动 <code>Clash</code><figure class="highlight shell"><table><tr><td class="code"><pre><span class="line">systemctl enable clash</span><br></pre></td></tr></table></figure></li>
+<li>启动 <code>Clash</code><figure class="highlight shell"><table><tr><td class="code"><pre><span class="line">systemctl start clash</span><br></pre></td></tr></table></figure></li>
+<li>检查 <code>Clash</code> 的健康状态和日志<figure class="highlight shell"><table><tr><td class="code"><pre><span class="line">systemctl status clash</span><br><span class="line">journalctl -xe</span><br></pre></td></tr></table></figure></li>
+</ol>
 ]]></content>
       <tags>
         <tag>proxy</tag>
+        <tag>clash</tag>
+      </tags>
+  </entry>
+  <entry>
+    <title>在 Windows 10 上安装 OpenVPN 服务端</title>
+    <url>/2023/06/07/how-to-setup-OpenVPN-server-on-windows-10/</url>
+    <content><![CDATA[<p>本文记录了如何在 <code>Windows 10</code> 上安装和配置 <code>OpenVPN</code> 服务端。</p>
+<span id="more"></span>
+
+<ul>
+<li>客户端的安装：<a href="/2023/06/07/how-to-setup-OpenVPN-connect-client-on-iOS-and-macOS/" title="在 iOS 和 macOS 上安装 OpenVPN 客户端">在 iOS 和 macOS 上安装 OpenVPN 客户端</a></li>
+<li>主要目的：<a href="/2023/06/07/how-to-use-OpenVPN-to-access-home-network/" title="使用 OpenVPN 访问家庭内网">使用 OpenVPN 访问家庭内网</a></li>
+</ul>
+<h2 id="环境"><a href="#环境" class="headerlink" title="环境"></a>环境</h2><ul>
+<li><code>Windows 10</code> 专业版</li>
+<li><code>OpenVPN 2.6.4</code></li>
+<li>拥有动态公网 <code>IP</code></li>
+</ul>
+<h2 id="安装-OpenVPN-server"><a href="#安装-OpenVPN-server" class="headerlink" title="安装 OpenVPN server"></a>安装 OpenVPN server</h2><ol>
+<li>从 <a href="https://openvpn.net/community-downloads/">OpenVPN 社区</a> 下载 <code>Windows 64-bit MSI installer</code>。本次安装的版本为 <code>OpenVPN 2.6.4</code>。</li>
+<li>在选择安装类型时，选择 <code>Customize</code> 而不要选择 <code>Install Now</code>。<ul>
+<li>勾选 <code>OpenVPN -&gt; OpenVPN Service -&gt; Entire feature will be installed on local hard drive</code>；</li>
+<li>勾选 <code>OpenSSL Utilities -&gt; EasyRSA 3 Certificate Management Scripts -&gt; Entire feature will be installed on local hard drive</code>；</li>
+</ul>
+</li>
+<li>安装完毕后，会弹出一条消息提示未找到可读的连接配置文件，暂时忽略。此时在“控制面板\网络和 Internet\网络连接”中可以看到创建了两个新的网络适配器 <code>OpenVPN TAP-Windows6</code> 和 <code>OpenVPN Wintun</code>。</li>
+</ol>
+<h2 id="配置-OpenVPN-server"><a href="#配置-OpenVPN-server" class="headerlink" title="配置 OpenVPN server"></a>配置 OpenVPN server</h2><ol>
+<li>打开 <code>Windows 10</code> 终端程序。</li>
+<li>进入 <code>OpenVPN</code> 默认安装目录中的 <code>easy-rsa</code> 目录。<figure class="highlight shell"><table><tr><td class="code"><pre><span class="line">cd &#x27;C:\Program Files\OpenVPN\easy-rsa&#x27;</span><br></pre></td></tr></table></figure></li>
+<li>执行命令进入 <code>Easy-RSA 3 Shell</code>。<figure class="highlight shell"><table><tr><td class="code"><pre><span class="line">.\EasyRSA-Start.bat</span><br></pre></td></tr></table></figure></li>
+<li>初始化公钥基础设施目录 <code>pki</code>。<figure class="highlight shell"><table><tr><td class="code"><pre><span class="line">./easyrsa init-pki</span><br></pre></td></tr></table></figure></li>
+<li>构建证书颁发机构（<code>CA</code>）密钥，<code>CA</code> 根证书文件将在后续用于对其他证书和密钥进行签名。该命令要求输入 <code>Common Name</code>，输入主机名即可。创建的 <code>ca.crt</code> 保存在目录 <code>C：\Program Files\OpenVPN\easy-rsa\pki</code> 中，<code>ca.key</code> 保存在目录 <code>C：\Program Files\OpenVPN\easy-rsa\pki\private</code> 中。<figure class="highlight shell"><table><tr><td class="code"><pre><span class="line">./easyrsa build-ca nopass</span><br></pre></td></tr></table></figure></li>
+<li>构建服务器证书和密钥。创建的 <code>server.crt</code> 保存在目录 <code>C：\Program Files\OpenVPN\easy-rsa\pki\issued</code> 中，<code>server.key</code> 保存在目录 <code>C：\Program Files\OpenVPN\easy-rsa\pki\private</code> 中。<figure class="highlight shell"><table><tr><td class="code"><pre><span class="line">./easyrsa build-server-full server nopass</span><br></pre></td></tr></table></figure></li>
+<li>构建客户端证书和密钥。创建的 <code>client.crt</code> 保存在目录 <code>C：\Program Files\OpenVPN\easy-rsa\pki\issued</code> 中，<code>client.key</code> 保存在目录 <code>C：\Program Files\OpenVPN\easy-rsa\pki\private</code> 中。<figure class="highlight shell"><table><tr><td class="code"><pre><span class="line">./easyrsa build-client-full client nopass</span><br></pre></td></tr></table></figure></li>
+<li>生成 <code>Diffie-Hellman</code> 参数<figure class="highlight shell"><table><tr><td class="code"><pre><span class="line">./easyrsa gen-dh</span><br></pre></td></tr></table></figure></li>
+<li>从目录 <code>C：\Program Files\OpenVPN\sample-config</code> 复制服务端配置文件模板 <code>server.ovpn</code> 到目录 <code>C：\Program Files\OpenVPN\config</code> 中，修改以下配置：端口号按需修改，默认为 <code>1194</code>，需要保证 <code>OpenVPN</code> 的网络流量可以通过防火墙，设置 <code>Windows 10 Defender</code> 允许 <code>OpenVPN</code> 通过即可。<code>dh2048.pem</code> 修改为生成的文件名 <code>dh.pem</code>。取消注释 <code>duplicate-cn</code>，让多个客户端使用同一个客户端证书。注释掉 <code>tls-auth ta.key 0</code>。<figure class="highlight ini"><table><tr><td class="code"><pre><span class="line">port 1194</span><br><span class="line">dh dh.pem</span><br><span class="line">duplicate-cn</span><br><span class="line"><span class="comment">;tls-auth ta.key 0</span></span><br></pre></td></tr></table></figure></li>
+<li>复制 <code>ca.crt</code>，<code>dh.pem</code>，<code>server.crt</code> 和 <code>server.key</code> 到目录 <code>C：\Program Files\OpenVPN\config</code> 中。</li>
+</ol>
+<h2 id="启动与连接"><a href="#启动与连接" class="headerlink" title="启动与连接"></a>启动与连接</h2><p>启动 <code>OpenVPN</code>，点击连接，系统提示分配 <code>IP</code> 为 <code>10.8.0.1</code>。按配置，每次 <code>OpenVPN server</code> 都将为自己分配 <code>10.8.0.1</code>。</p>
+<h2 id="参考链接"><a href="#参考链接" class="headerlink" title="参考链接"></a>参考链接</h2><p><a href="https://blog.eyyyye.com/article/39#menu_3">openvpn安装配置说明(windows系统)</a><br><a href="https://zhuanlan.zhihu.com/p/525197398">如何在Windows 10上安装和配置OpenVPN</a></p>
+]]></content>
+      <tags>
         <tag>openvpn</tag>
+        <tag>proxy</tag>
       </tags>
   </entry>
   <entry>
@@ -1419,104 +1419,29 @@
 <h2 id="参考链接"><a href="#参考链接" class="headerlink" title="参考链接"></a>参考链接</h2><p><a href="https://blog.51cto.com/richie/389636">透过openvpn来访问内网资源</a><br><a href="https://limbo.moe/posts/2018/openvpn-routes">OpenVPN 路由详解</a><br><a href="https://qastack.cn/superuser/865302/yet-another-routing-issue-in-openvpn-cannot-access-local-machines-while-on-vpn">OpenVPN中的另一个路由问题 - 在VPN上无法访问本地计算机</a><br><a href="https://www.nixops.me/articles/openvpn-add-local-routing-table.html">openvpn添加本地路由表</a><br><a href="https://blog.csdn.net/qq_43615820/article/details/113660623">windows开启路由转发</a><br><a href="https://www.cnblogs.com/snake-hand/p/3143041.html">linux route命令的使用详解</a><br><a href="https://blog.csdn.net/bcbobo21cn/article/details/52548923">Windows命令行route命令使用图解</a></p>
 ]]></content>
       <tags>
-        <tag>proxy</tag>
         <tag>openvpn</tag>
+        <tag>proxy</tag>
       </tags>
   </entry>
   <entry>
-    <title>如何为终端、docker 和容器设置代理</title>
-    <url>/2023/06/13/how-to-configure-proxy-for-terminal-docker-and-container/</url>
-    <content><![CDATA[<p>在 <a href="/2023/05/27/how-to-install-clash-on-ubuntu/" title="在 Ubuntu 上安装 Clash">Ubuntu 上安装 Clash</a> 后，Clash 通过监听本地的 7890 端口，提供代理服务。但是不同程序设置代理的方式不尽相同，并不是启动了 Clash 以及在某一处设置后，整个系统发出的 HTTP 请求都能经过代理。本文将介绍如何为终端、docker 和容器添加代理。</p>
-<h2 id="为终端设置代理"><a href="#为终端设置代理" class="headerlink" title="为终端设置代理"></a>为终端设置代理</h2><p>有时候，我们需要在终端通过执行命令的方式访问网络和下载资源，比如使用 <code>wget</code> 和 <code>curl</code>。</p>
-<h3 id="设置-Shell-环境变量"><a href="#设置-Shell-环境变量" class="headerlink" title="设置 Shell 环境变量"></a>设置 Shell 环境变量</h3><p>这一类软件都是可以通过为 Shell 设置环境变量的方式来设置代理，涉及到的环境变量有 <code>http_proxy</code>、<code>https_proxy</code> 和 <code>no_proxy</code>。<br>仅为当前会话设置，执行命令：</p>
-<figure class="highlight shell"><table><tr><td class="code"><pre><span class="line">export http_proxy=http://proxyAddress:port</span><br><span class="line">export https_proxy=http://proxyAddress:port</span><br><span class="line">export no_proxy=localhost,127.0.0.1</span><br></pre></td></tr></table></figure>
-<p>永久设置代理，在设置 Shell 环境变量的脚本中（不同 Shell 的配置文件不同，比如 <code>~/.bashrc</code> 或 <code>~/.zshrc</code>）添加：</p>
-<figure class="highlight shell"><table><tr><td class="code"><pre><span class="line">export http_proxy=http://proxyAddress:port</span><br><span class="line">export https_proxy=http://proxyAddress:port</span><br><span class="line">export no_proxy=localhost,127.0.0.1</span><br></pre></td></tr></table></figure>
-<p>重新启动一个会话或者执行命令 <code>source ~/.bashrc</code> 使其在当前会话立即生效。</p>
-<h3 id="修改-wget-配置文件"><a href="#修改-wget-配置文件" class="headerlink" title="修改 wget 配置文件"></a>修改 wget 配置文件</h3><p>在搜索过程中发现还可以在 <code>wget</code> 的配置文件 <code>~/.wgetrc</code> 中添加:</p>
-<figure class="highlight shell"><table><tr><td class="code"><pre><span class="line">use_proxy = on</span><br><span class="line"></span><br><span class="line">http_proxy = http://proxyAddress:port</span><br><span class="line">https_proxy = http://proxyAddress:port</span><br></pre></td></tr></table></figure>
+    <title>如何在 Ubuntu 20.04 上安装 Minikube</title>
+    <url>/2023/06/23/how-to-install-Minikube-on-Ubuntu-20-04/</url>
+    <content><![CDATA[<h2 id="环境搭建"><a href="#环境搭建" class="headerlink" title="环境搭建"></a>环境搭建</h2><h3 id="安装-Ubuntu-20-04"><a href="#安装-Ubuntu-20-04" class="headerlink" title="安装 Ubuntu 20.04"></a>安装 Ubuntu 20.04</h3><p>使用 Vmware Workstation 通过 <code>ubuntu-20.04.6-live-server-amd64.iso</code> 安装。需要满足条件如下：</p>
+<ul>
+<li>2 个或更多 CPU（2 CPU）。</li>
+<li>2GB 可用内存（4GB）。</li>
+<li>20GB 可用磁盘空间（30GB）。</li>
+<li>网络连接</li>
+<li>容器或虚拟机管理器（Docker）。</li>
+</ul>
+<h3 id="安装-Docker"><a href="#安装-Docker" class="headerlink" title="安装 Docker"></a>安装 Docker</h3><p>参考官方文档：<a href="https://docs.docker.com/engine/install/ubuntu/">Install Docker Engine on Ubuntu</a>。</p>
+<h3 id="安装-Minikube"><a href="#安装-Minikube" class="headerlink" title="安装 Minikube"></a>安装 Minikube</h3><p>参考官方文档：<a href="https://minikube.sigs.k8s.io/docs/start/">minikube start</a>。</p>
+<h3 id="安装-kubectl-并启动-kubectl-自动补全功能"><a href="#安装-kubectl-并启动-kubectl-自动补全功能" class="headerlink" title="安装 kubectl 并启动 kubectl 自动补全功能"></a>安装 kubectl 并启动 kubectl 自动补全功能</h3><p>参考官方文档：<a href="https://kubernetes.io/zh-cn/docs/tasks/tools/install-kubectl-linux/">在 Linux 系统中安装并设置 kubectl</a>。</p>
+<h3 id="开始使用"><a href="#开始使用" class="headerlink" title="开始使用"></a>开始使用</h3><p>创建集群：</p>
+<figure class="highlight shell"><table><tr><td class="code"><pre><span class="line">minikube start</span><br></pre></td></tr></table></figure>
 
-<h2 id="为-docker-设置代理"><a href="#为-docker-设置代理" class="headerlink" title="为 docker 设置代理"></a>为 docker 设置代理</h2><p>如果你以为为终端设置代理后 docker 就会使用代理，那你就错了。在从官方的镜像仓库 pull 镜像反复出错后并收到类似 <code>Error response from daemon: Get &quot;https://registry-1.docker.io/v2/&quot;: read tcp 192.168.3.140:59460-&gt;44.205.64.79:443: read: connection reset by peer</code> 这样的报错信息后，我才开始怀疑我并没有真正给 docker 设置好代理。<br>在执行 <code>docker pull</code> 命令时，实际上命令是由守护进程 <code>docker daemon</code> 执行的。</p>
-<h3 id="通过-systemd-设置"><a href="#通过-systemd-设置" class="headerlink" title="通过 systemd 设置"></a>通过 systemd 设置</h3><p>如果你的 <code>docker daemon</code> 是通过 <code>systemd</code> 管理的，那么你可以通过设置 <code>docker.service</code> 服务的环境变量来设置代理。<br>执行命令查看 <code>docker.service</code> 信息，得知配置文件位置 <code>/lib/systemd/system/docker.service</code>。</p>
-<figure class="highlight shell"><table><tr><td class="code"><pre><span class="line"><span class="meta prompt_">~$ </span><span class="language-bash">systemctl status docker.service</span> </span><br><span class="line">● docker.service - Docker Application Container Engine</span><br><span class="line">     Loaded: loaded (/lib/systemd/system/docker.service; enabled; vendor preset: enabled)</span><br><span class="line">     Active: active (running) since Tue 2023-06-13 00:52:54 CST; 22h ago</span><br><span class="line">TriggeredBy: ● docker.socket</span><br><span class="line">       Docs: https://docs.docker.com</span><br><span class="line">   Main PID: 387690 (dockerd)</span><br><span class="line">      Tasks: 139</span><br><span class="line">     Memory: 89.6M</span><br><span class="line">        CPU: 1min 26.512s</span><br><span class="line">     CGroup: /system.slice/docker.service</span><br></pre></td></tr></table></figure>
-<p>在 <code>docker.service</code> 的 <code>[Service]</code> 模块添加：</p>
-<figure class="highlight shell"><table><tr><td class="code"><pre><span class="line">Environment=HTTP_PROXY=http://proxyAddress:port</span><br><span class="line">Environment=HTTPS_PROXY=http://proxyAddress:port</span><br><span class="line">Environment=NO_PROXY=localhost,127.0.0.1</span><br></pre></td></tr></table></figure>
-<p>重新加载配置文件并重启服务：</p>
-<figure class="highlight shell"><table><tr><td class="code"><pre><span class="line">systemctl daemon-reload</span><br><span class="line">systemctl restart docker.service</span><br></pre></td></tr></table></figure>
-
-<h3 id="修改-dockerd-配置文件"><a href="#修改-dockerd-配置文件" class="headerlink" title="修改 dockerd 配置文件"></a>修改 dockerd 配置文件</h3><p>还可以修改 <code>dockerd</code> 配置文件，添加：</p>
-<figure class="highlight shell"><table><tr><td class="code"><pre><span class="line">export http_proxy=&quot;http://proxyAddress:port&quot;</span><br></pre></td></tr></table></figure>
-<p>然后重启 <code>docker daemon</code> 即可。</p>
-<blockquote>
-<p>国内的镜像仓库在绝大多数时候都可以满足条件，但是存在个别镜像同步不及时的情况，如果使用 latest 标签拉取到的镜像并非近期的镜像，因此有时候需要直接从官方镜像仓库拉取镜像。</p>
-</blockquote>
-<h2 id="为-docker-容器设置代理"><a href="#为-docker-容器设置代理" class="headerlink" title="为 docker 容器设置代理"></a>为 docker 容器设置代理</h2><p>为 <code>docker daemon</code> 进程设置代理和为 docker 容器设置代理是有区别的。比如使用 docker 启动媒体服务器 jellyfin 后，jellyfin 的刮削功能就需要代理才能正常使用，这时候不要因为在很多地方设置过代理就以为容器内部已经在使用代理了。</p>
-<h3 id="修改配置文件"><a href="#修改配置文件" class="headerlink" title="修改配置文件"></a>修改配置文件</h3><p>创建或修改 <code>~/.docker/config.json</code>，添加：</p>
-<figure class="highlight json"><table><tr><td class="code"><pre><span class="line"><span class="punctuation">&#123;</span></span><br><span class="line">    <span class="attr">&quot;proxies&quot;</span><span class="punctuation">:</span></span><br><span class="line">    <span class="punctuation">&#123;</span></span><br><span class="line">        <span class="attr">&quot;default&quot;</span><span class="punctuation">:</span></span><br><span class="line">        <span class="punctuation">&#123;</span></span><br><span class="line">            <span class="attr">&quot;httpProxy&quot;</span><span class="punctuation">:</span> <span class="string">&quot;http://proxyAddress:port&quot;</span><span class="punctuation">,</span></span><br><span class="line">            <span class="attr">&quot;httpsProxy&quot;</span><span class="punctuation">:</span> <span class="string">&quot;http://proxyAddress:port&quot;</span><span class="punctuation">,</span></span><br><span class="line">            <span class="attr">&quot;noProxy&quot;</span><span class="punctuation">:</span> <span class="string">&quot;localhost,127.0.0.1&quot;</span></span><br><span class="line">        <span class="punctuation">&#125;</span></span><br><span class="line">    <span class="punctuation">&#125;</span></span><br><span class="line"><span class="punctuation">&#125;</span></span><br></pre></td></tr></table></figure>
-<p>此后创建的新容器，会自动设置环境变量来使用代理。</p>
-<h3 id="为指定容器添加环境变量"><a href="#为指定容器添加环境变量" class="headerlink" title="为指定容器添加环境变量"></a>为指定容器添加环境变量</h3><p>在启动容器时使用 <code>-e</code> 手动注入环境变量 <code>http_proxy</code>。这意味着进入容器使用 <code>export</code> 设置环境变量的方式也是可行的。</p>
-<blockquote>
-<p>注意：如果代理是使用宿主机的代理，当网络为 <code>bridge</code> 模式，proxyAddress 需要填写宿主机的 IP；如果使用 <code>host</code> 模式，proxyAddress 可以填写 127.0.0.1。</p>
-</blockquote>
-<h2 id="总结"><a href="#总结" class="headerlink" title="总结"></a>总结</h2><p>不要因为在很多地方设置过代理，就想当然地以为当前的访问也是经过代理的。每个软件设置代理的方式不尽相同，但是大体上可以归结为：</p>
-<ol>
-<li>使用系统的环境变量</li>
-<li>修改软件的配置文件</li>
-<li>执行时注入参数</li>
-</ol>
-<p>举一反三，像 <code>apt</code> 和 <code>git</code> 这类软件也是有其设置代理的方法。当你的代理稳定但是相应的访问失败时，大胆假设你的代理没有设置成功。要理清楚，当前的访问是谁发起的，才能正确地使用关键词搜索到正确的设置方式。</p>
-<blockquote>
-<p>原本我在 docker 相关的使用中，有关代理的设置方式是通过修改配置文件，实现永久、全局的代理配置。但是在后续的使用中，发现代理在一些场景（比如使用 cloudflare tunnel）中会引起不易排查的问题，决定采用临时、局部的配置方式。</p>
-</blockquote>
-<h2 id="参考链接"><a href="#参考链接" class="headerlink" title="参考链接"></a>参考链接</h2><p><a href="https://zhuanlan.zhihu.com/p/46973701">Linux 让终端走代理的几种方法</a><br><a href="https://blog.51cto.com/u_14814563/5415887">Linux ❀ wget设置代理</a><br><a href="https://cloud-atlas.readthedocs.io/zh_CN/latest/docker/network/docker_proxy.html#docker-server-proxy">配置Docker使用代理</a><br><a href="https://note.qidong.name/2020/05/docker-proxy/">Docker的三种网络代理配置</a><br><a href="https://neucrack.com/p/286">docker 设置代理，以及国内加速镜像设置</a></p>
-]]></content>
-      <tags>
-        <tag>docker</tag>
-        <tag>proxy</tag>
-      </tags>
-  </entry>
-  <entry>
-    <title>Ubuntu server 20.04 安装后没有分配全部磁盘空间</title>
-    <url>/2023/06/24/Ubuntu-server-20-04-not-all-disk-space-was-allocated-after-installation/</url>
-    <content><![CDATA[<p>使用 <code>VMware</code> 安装 <code>Ubuntu server 20.04</code>，注意到实际文件系统的总空间大小仅占设置的虚拟磁盘空间大小的一半左右。本文介绍了如何解决该问题。</p>
-<span id="more"></span>
-
-<blockquote>
-<p>最近在本地测试 <code>Kubesphere</code> 和 <code>Minikube</code>，使用 <code>Ubuntu server 20.04</code> 搭建了多个虚拟机，磁盘空间紧张。注意到在安装后，实际文件系统的总空间大小仅占设置的虚拟磁盘空间大小的一半左右。如果 <code>Ubuntu server 20.04</code> 安装时使用默认的 <code>LVM</code> 选项，就会出现这种情况。</p>
-</blockquote>
-<h2 id="解决步骤"><a href="#解决步骤" class="headerlink" title="解决步骤"></a>解决步骤</h2><ol>
-<li>使用 <code>df -h</code> 命令显示文件系统的总空间和可用空间信息。分配了 <code>40G</code> 磁盘空间，可用仅 <code>19G</code>。<figure class="highlight shell"><table><tr><td class="code"><pre><span class="line"><span class="meta prompt_">$ </span><span class="language-bash"><span class="built_in">df</span> -h</span></span><br><span class="line">Filesystem                         Size  Used Avail Use% Mounted on</span><br><span class="line">udev                               3.9G     0  3.9G   0% /dev</span><br><span class="line">tmpfs                              792M  7.5M  785M   1% /run</span><br><span class="line">/dev/mapper/ubuntu--vg-ubuntu--lv   19G   17G  995M  95% /</span><br><span class="line">tmpfs                              3.9G     0  3.9G   0% /dev/shm</span><br><span class="line">tmpfs                              5.0M     0  5.0M   0% /run/lock</span><br><span class="line">tmpfs                              3.9G     0  3.9G   0% /sys/fs/cgroup</span><br><span class="line">/dev/sda2                          2.0G  108M  1.7G   6% /boot</span><br><span class="line">/dev/loop0                          64M   64M     0 100% /snap/core20/1828</span><br><span class="line">/dev/loop2                          50M   50M     0 100% /snap/snapd/18357</span><br><span class="line">/dev/loop1                          92M   92M     0 100% /snap/lxd/24061</span><br><span class="line">tmpfs                              792M     0  792M   0% /run/user/1000</span><br><span class="line">/dev/loop3                          54M   54M     0 100% /snap/snapd/19457</span><br></pre></td></tr></table></figure></li>
-<li>使用 <code>sudo vgdisplay</code> 命令查看发现 <code>Free  PE / Size</code> 还有 <code>19G</code>。<figure class="highlight shell"><table><tr><td class="code"><pre><span class="line"><span class="meta prompt_">$ </span><span class="language-bash">sudo vgdisplay</span></span><br><span class="line">  --- Volume group ---</span><br><span class="line">  VG Name               ubuntu-vg</span><br><span class="line">  System ID             </span><br><span class="line">  Format                lvm2</span><br><span class="line">  Metadata Areas        1</span><br><span class="line">  Metadata Sequence No  2</span><br><span class="line">  VG Access             read/write</span><br><span class="line">  VG Status             resizable</span><br><span class="line">  MAX LV                0</span><br><span class="line">  Cur LV                1</span><br><span class="line">  Open LV               1</span><br><span class="line">  Max PV                0</span><br><span class="line">  Cur PV                1</span><br><span class="line">  Act PV                1</span><br><span class="line">  VG Size               &lt;38.00 GiB</span><br><span class="line">  PE Size               4.00 MiB</span><br><span class="line">  Total PE              9727</span><br><span class="line">  Alloc PE / Size       4863 / &lt;19.00 GiB</span><br><span class="line">  Free  PE / Size       4864 / 19.00 GiB</span><br><span class="line">  VG UUID               NuEjzH-CKXm-W6lA-gqzj-4bds-IR1Y-dTZ8IP</span><br></pre></td></tr></table></figure></li>
-<li>使用 <code>sudo lvextend -l +100%FREE /dev/mapper/ubuntu--vg-ubuntu--lv</code> 调整逻辑卷的大小。<figure class="highlight shell"><table><tr><td class="code"><pre><span class="line"><span class="meta prompt_">$ </span><span class="language-bash">sudo lvextend -l +100%FREE /dev/mapper/ubuntu--vg-ubuntu--lv</span></span><br><span class="line">Size of logical volume ubuntu-vg/ubuntu-lv changed from &lt;19.00 GiB (4863 extents) to &lt;38.00 GiB (9727 extents).</span><br><span class="line">Logical volume ubuntu-vg/ubuntu-lv successfully resized.</span><br></pre></td></tr></table></figure></li>
-<li>使用 <code>sudo resize2fs /dev/mapper/ubuntu--vg-ubuntu--lv</code> 调整文件系统的大小。<figure class="highlight shell"><table><tr><td class="code"><pre><span class="line"><span class="meta prompt_">$ </span><span class="language-bash">sudo resize2fs /dev/mapper/ubuntu--vg-ubuntu--lv</span></span><br><span class="line">resize2fs 1.45.5 (07-Jan-2020)</span><br><span class="line">Filesystem at /dev/mapper/ubuntu--vg-ubuntu--lv is mounted on /; on-line resizing required</span><br><span class="line">old_desc_blocks = 3, new_desc_blocks = 5</span><br><span class="line">The filesystem on /dev/mapper/ubuntu--vg-ubuntu--lv is now 9960448 (4k) blocks long.</span><br></pre></td></tr></table></figure></li>
-<li>使用 <code>df -h</code> 命令再次查看，确认文件系统的总空间大小调整为 <code>38G</code>。<figure class="highlight shell"><table><tr><td class="code"><pre><span class="line">df -h</span><br><span class="line">Filesystem                         Size  Used Avail Use% Mounted on</span><br><span class="line">udev                               3.9G     0  3.9G   0% /dev</span><br><span class="line">tmpfs                              792M  7.5M  785M   1% /run</span><br><span class="line">/dev/mapper/ubuntu--vg-ubuntu--lv   38G   17G   19G  47% /</span><br><span class="line">tmpfs                              3.9G     0  3.9G   0% /dev/shm</span><br><span class="line">tmpfs                              5.0M     0  5.0M   0% /run/lock</span><br><span class="line">tmpfs                              3.9G     0  3.9G   0% /sys/fs/cgroup</span><br><span class="line">/dev/sda2                          2.0G  108M  1.7G   6% /boot</span><br><span class="line">/dev/loop0                          64M   64M     0 100% /snap/core20/1828</span><br><span class="line">/dev/loop2                          50M   50M     0 100% /snap/snapd/18357</span><br><span class="line">/dev/loop1                          92M   92M     0 100% /snap/lxd/24061</span><br><span class="line">tmpfs                              792M     0  792M   0% /run/user/1000</span><br><span class="line">/dev/loop3                          54M   54M     0 100% /snap/snapd/19457</span><br><span class="line">/dev/loop4                          64M   64M     0 100% /snap/core20/1950</span><br></pre></td></tr></table></figure></li>
-</ol>
-<h2 id="参考链接"><a href="#参考链接" class="headerlink" title="参考链接"></a>参考链接</h2><p><a href="https://blog.csdn.net/weixin_43302340/article/details/120341241">ubuntu20.04 server 安装后磁盘空间只有一半的处理</a><br><a href="https://askubuntu.com/questions/1269493/ubuntu-server-20-04-1-lts-not-all-disk-space-was-allocated-during-installation">Ubuntu Server 20.04.1 LTS, not all disk space was allocated during installation?</a></p>
-]]></content>
-      <tags>
-        <tag>linux</tag>
-        <tag>ubuntu</tag>
-      </tags>
-  </entry>
-  <entry>
-    <title>如何在 Ubuntu 20.04 上安装 Minikube</title>
-    <url>/2023/06/23/how-to-install-Minikube-on-Ubuntu-20-04/</url>
-    <content><![CDATA[<h2 id="环境搭建"><a href="#环境搭建" class="headerlink" title="环境搭建"></a>环境搭建</h2><h3 id="安装-Ubuntu-20-04"><a href="#安装-Ubuntu-20-04" class="headerlink" title="安装 Ubuntu 20.04"></a>安装 Ubuntu 20.04</h3><p>使用 Vmware Workstation 通过 <code>ubuntu-20.04.6-live-server-amd64.iso</code> 安装。需要满足条件如下：</p>
-<ul>
-<li>2 个或更多 CPU（2 CPU）。</li>
-<li>2GB 可用内存（4GB）。</li>
-<li>20GB 可用磁盘空间（30GB）。</li>
-<li>网络连接</li>
-<li>容器或虚拟机管理器（Docker）。</li>
-</ul>
-<h3 id="安装-Docker"><a href="#安装-Docker" class="headerlink" title="安装 Docker"></a>安装 Docker</h3><p>参考官方文档：<a href="https://docs.docker.com/engine/install/ubuntu/">Install Docker Engine on Ubuntu</a>。</p>
-<h3 id="安装-Minikube"><a href="#安装-Minikube" class="headerlink" title="安装 Minikube"></a>安装 Minikube</h3><p>参考官方文档：<a href="https://minikube.sigs.k8s.io/docs/start/">minikube start</a>。</p>
-<h3 id="安装-kubectl-并启动-kubectl-自动补全功能"><a href="#安装-kubectl-并启动-kubectl-自动补全功能" class="headerlink" title="安装 kubectl 并启动 kubectl 自动补全功能"></a>安装 kubectl 并启动 kubectl 自动补全功能</h3><p>参考官方文档：<a href="https://kubernetes.io/zh-cn/docs/tasks/tools/install-kubectl-linux/">在 Linux 系统中安装并设置 kubectl</a>。</p>
-<h3 id="开始使用"><a href="#开始使用" class="headerlink" title="开始使用"></a>开始使用</h3><p>创建集群：</p>
-<figure class="highlight shell"><table><tr><td class="code"><pre><span class="line">minikube start</span><br></pre></td></tr></table></figure>
-
-<h4 id="创建集群时的权限问题"><a href="#创建集群时的权限问题" class="headerlink" title="创建集群时的权限问题"></a>创建集群时的权限问题</h4><h5 id="不加-sudo"><a href="#不加-sudo" class="headerlink" title="不加 sudo"></a>不加 sudo</h5><p>不加 <code>sudo</code> 的时候，创建集群失败，提示无法选择默认 driver。可能是 docker 处于不健康状态或者用户权限不足。</p>
-<figure class="highlight plaintext"><table><tr><td class="code"><pre><span class="line">$ minikube start</span><br><span class="line">* minikube v1.30.1 on Ubuntu 20.04</span><br><span class="line">* Unable to pick a default driver. Here is what was considered, in preference order:</span><br><span class="line">  - docker: Not healthy: &quot;docker version --format &#123;&#123;.Server.Os&#125;&#125;-&#123;&#123;.Server.Version&#125;&#125;:&#123;&#123;.Server.Platform.Name&#125;&#125;&quot; exit status 1: permission denied while trying to connect to the Docker daemon socket at unix:///var/run/docker.sock: Get &quot;http://%2Fvar%2Frun%2Fdocker.sock/v1.24/version&quot;: dial unix /var/run/docker.sock: connect: permission denied</span><br><span class="line">  - docker: Suggestion: Add your user to the &#x27;docker&#x27; group: &#x27;sudo usermod -aG docker $USER &amp;&amp; newgrp docker&#x27; &lt;https://docs.docker.com/engine/install/linux-postinstall/&gt;</span><br><span class="line">* Alternatively you could install one of these drivers:</span><br><span class="line">  - kvm2: Not installed: exec: &quot;virsh&quot;: executable file not found in $PATH</span><br><span class="line">  - podman: Not installed: exec: &quot;podman&quot;: executable file not found in $PATH</span><br><span class="line">  - qemu2: Not installed: exec: &quot;qemu-system-x86_64&quot;: executable file not found in $PATH</span><br><span class="line">  - virtualbox: Not installed: unable to find VBoxManage in $PATH</span><br><span class="line"></span><br><span class="line">X Exiting due to DRV_NOT_HEALTHY: Found driver(s) but none were healthy. See above for suggestions how to fix installed drivers.</span><br></pre></td></tr></table></figure>
+<h4 id="创建集群时的权限问题"><a href="#创建集群时的权限问题" class="headerlink" title="创建集群时的权限问题"></a>创建集群时的权限问题</h4><h5 id="不加-sudo"><a href="#不加-sudo" class="headerlink" title="不加 sudo"></a>不加 sudo</h5><p>不加 <code>sudo</code> 的时候，创建集群失败，提示无法选择默认 driver。可能是 docker 处于不健康状态或者用户权限不足。</p>
+<figure class="highlight plaintext"><table><tr><td class="code"><pre><span class="line">$ minikube start</span><br><span class="line">* minikube v1.30.1 on Ubuntu 20.04</span><br><span class="line">* Unable to pick a default driver. Here is what was considered, in preference order:</span><br><span class="line">  - docker: Not healthy: &quot;docker version --format &#123;&#123;.Server.Os&#125;&#125;-&#123;&#123;.Server.Version&#125;&#125;:&#123;&#123;.Server.Platform.Name&#125;&#125;&quot; exit status 1: permission denied while trying to connect to the Docker daemon socket at unix:///var/run/docker.sock: Get &quot;http://%2Fvar%2Frun%2Fdocker.sock/v1.24/version&quot;: dial unix /var/run/docker.sock: connect: permission denied</span><br><span class="line">  - docker: Suggestion: Add your user to the &#x27;docker&#x27; group: &#x27;sudo usermod -aG docker $USER &amp;&amp; newgrp docker&#x27; &lt;https://docs.docker.com/engine/install/linux-postinstall/&gt;</span><br><span class="line">* Alternatively you could install one of these drivers:</span><br><span class="line">  - kvm2: Not installed: exec: &quot;virsh&quot;: executable file not found in $PATH</span><br><span class="line">  - podman: Not installed: exec: &quot;podman&quot;: executable file not found in $PATH</span><br><span class="line">  - qemu2: Not installed: exec: &quot;qemu-system-x86_64&quot;: executable file not found in $PATH</span><br><span class="line">  - virtualbox: Not installed: unable to find VBoxManage in $PATH</span><br><span class="line"></span><br><span class="line">X Exiting due to DRV_NOT_HEALTHY: Found driver(s) but none were healthy. See above for suggestions how to fix installed drivers.</span><br></pre></td></tr></table></figure>
 
 <h5 id="使用-sudo"><a href="#使用-sudo" class="headerlink" title="使用 sudo"></a>使用 sudo</h5><p>使用 <code>sudo</code> 的时候，会提示不建议通过 <code>root</code> 权限使用 <code>docker</code>，如果还是想要继续，可以使用选项 <code>--force</code>。</p>
 <figure class="highlight shell"><table><tr><td class="code"><pre><span class="line"><span class="meta prompt_">$ </span><span class="language-bash">sudo minikube start</span></span><br><span class="line">* minikube v1.30.1 on Ubuntu 20.04</span><br><span class="line">* Automatically selected the docker driver. Other choices: none, ssh</span><br><span class="line">* The &quot;docker&quot; driver should not be used with root privileges. If you wish to continue as root, use --force.</span><br><span class="line">* If you are running minikube within a VM, consider using --driver=none:</span><br><span class="line">*   https://minikube.sigs.k8s.io/docs/reference/drivers/none/</span><br><span class="line"></span><br><span class="line">X Exiting due to DRV_AS_ROOT: The &quot;docker&quot; driver should not be used with root privileges.</span><br></pre></td></tr></table></figure>
@@ -1560,6 +1485,29 @@
         <tag>k8s</tag>
       </tags>
   </entry>
+  <entry>
+    <title>Ubuntu server 20.04 安装后没有分配全部磁盘空间</title>
+    <url>/2023/06/24/Ubuntu-server-20-04-not-all-disk-space-was-allocated-after-installation/</url>
+    <content><![CDATA[<p>使用 <code>VMware</code> 安装 <code>Ubuntu server 20.04</code>，注意到实际文件系统的总空间大小仅占设置的虚拟磁盘空间大小的一半左右。本文介绍了如何解决该问题。</p>
+<span id="more"></span>
+
+<blockquote>
+<p>最近在本地测试 <code>Kubesphere</code> 和 <code>Minikube</code>，使用 <code>Ubuntu server 20.04</code> 搭建了多个虚拟机，磁盘空间紧张。注意到在安装后，实际文件系统的总空间大小仅占设置的虚拟磁盘空间大小的一半左右。如果 <code>Ubuntu server 20.04</code> 安装时使用默认的 <code>LVM</code> 选项，就会出现这种情况。</p>
+</blockquote>
+<h2 id="解决步骤"><a href="#解决步骤" class="headerlink" title="解决步骤"></a>解决步骤</h2><ol>
+<li>使用 <code>df -h</code> 命令显示文件系统的总空间和可用空间信息。分配了 <code>40G</code> 磁盘空间，可用仅 <code>19G</code>。<figure class="highlight shell"><table><tr><td class="code"><pre><span class="line"><span class="meta prompt_">$ </span><span class="language-bash"><span class="built_in">df</span> -h</span></span><br><span class="line">Filesystem                         Size  Used Avail Use% Mounted on</span><br><span class="line">udev                               3.9G     0  3.9G   0% /dev</span><br><span class="line">tmpfs                              792M  7.5M  785M   1% /run</span><br><span class="line">/dev/mapper/ubuntu--vg-ubuntu--lv   19G   17G  995M  95% /</span><br><span class="line">tmpfs                              3.9G     0  3.9G   0% /dev/shm</span><br><span class="line">tmpfs                              5.0M     0  5.0M   0% /run/lock</span><br><span class="line">tmpfs                              3.9G     0  3.9G   0% /sys/fs/cgroup</span><br><span class="line">/dev/sda2                          2.0G  108M  1.7G   6% /boot</span><br><span class="line">/dev/loop0                          64M   64M     0 100% /snap/core20/1828</span><br><span class="line">/dev/loop2                          50M   50M     0 100% /snap/snapd/18357</span><br><span class="line">/dev/loop1                          92M   92M     0 100% /snap/lxd/24061</span><br><span class="line">tmpfs                              792M     0  792M   0% /run/user/1000</span><br><span class="line">/dev/loop3                          54M   54M     0 100% /snap/snapd/19457</span><br></pre></td></tr></table></figure></li>
+<li>使用 <code>sudo vgdisplay</code> 命令查看发现 <code>Free  PE / Size</code> 还有 <code>19G</code>。<figure class="highlight shell"><table><tr><td class="code"><pre><span class="line"><span class="meta prompt_">$ </span><span class="language-bash">sudo vgdisplay</span></span><br><span class="line">  --- Volume group ---</span><br><span class="line">  VG Name               ubuntu-vg</span><br><span class="line">  System ID             </span><br><span class="line">  Format                lvm2</span><br><span class="line">  Metadata Areas        1</span><br><span class="line">  Metadata Sequence No  2</span><br><span class="line">  VG Access             read/write</span><br><span class="line">  VG Status             resizable</span><br><span class="line">  MAX LV                0</span><br><span class="line">  Cur LV                1</span><br><span class="line">  Open LV               1</span><br><span class="line">  Max PV                0</span><br><span class="line">  Cur PV                1</span><br><span class="line">  Act PV                1</span><br><span class="line">  VG Size               &lt;38.00 GiB</span><br><span class="line">  PE Size               4.00 MiB</span><br><span class="line">  Total PE              9727</span><br><span class="line">  Alloc PE / Size       4863 / &lt;19.00 GiB</span><br><span class="line">  Free  PE / Size       4864 / 19.00 GiB</span><br><span class="line">  VG UUID               NuEjzH-CKXm-W6lA-gqzj-4bds-IR1Y-dTZ8IP</span><br></pre></td></tr></table></figure></li>
+<li>使用 <code>sudo lvextend -l +100%FREE /dev/mapper/ubuntu--vg-ubuntu--lv</code> 调整逻辑卷的大小。<figure class="highlight shell"><table><tr><td class="code"><pre><span class="line"><span class="meta prompt_">$ </span><span class="language-bash">sudo lvextend -l +100%FREE /dev/mapper/ubuntu--vg-ubuntu--lv</span></span><br><span class="line">Size of logical volume ubuntu-vg/ubuntu-lv changed from &lt;19.00 GiB (4863 extents) to &lt;38.00 GiB (9727 extents).</span><br><span class="line">Logical volume ubuntu-vg/ubuntu-lv successfully resized.</span><br></pre></td></tr></table></figure></li>
+<li>使用 <code>sudo resize2fs /dev/mapper/ubuntu--vg-ubuntu--lv</code> 调整文件系统的大小。<figure class="highlight shell"><table><tr><td class="code"><pre><span class="line"><span class="meta prompt_">$ </span><span class="language-bash">sudo resize2fs /dev/mapper/ubuntu--vg-ubuntu--lv</span></span><br><span class="line">resize2fs 1.45.5 (07-Jan-2020)</span><br><span class="line">Filesystem at /dev/mapper/ubuntu--vg-ubuntu--lv is mounted on /; on-line resizing required</span><br><span class="line">old_desc_blocks = 3, new_desc_blocks = 5</span><br><span class="line">The filesystem on /dev/mapper/ubuntu--vg-ubuntu--lv is now 9960448 (4k) blocks long.</span><br></pre></td></tr></table></figure></li>
+<li>使用 <code>df -h</code> 命令再次查看，确认文件系统的总空间大小调整为 <code>38G</code>。<figure class="highlight shell"><table><tr><td class="code"><pre><span class="line">df -h</span><br><span class="line">Filesystem                         Size  Used Avail Use% Mounted on</span><br><span class="line">udev                               3.9G     0  3.9G   0% /dev</span><br><span class="line">tmpfs                              792M  7.5M  785M   1% /run</span><br><span class="line">/dev/mapper/ubuntu--vg-ubuntu--lv   38G   17G   19G  47% /</span><br><span class="line">tmpfs                              3.9G     0  3.9G   0% /dev/shm</span><br><span class="line">tmpfs                              5.0M     0  5.0M   0% /run/lock</span><br><span class="line">tmpfs                              3.9G     0  3.9G   0% /sys/fs/cgroup</span><br><span class="line">/dev/sda2                          2.0G  108M  1.7G   6% /boot</span><br><span class="line">/dev/loop0                          64M   64M     0 100% /snap/core20/1828</span><br><span class="line">/dev/loop2                          50M   50M     0 100% /snap/snapd/18357</span><br><span class="line">/dev/loop1                          92M   92M     0 100% /snap/lxd/24061</span><br><span class="line">tmpfs                              792M     0  792M   0% /run/user/1000</span><br><span class="line">/dev/loop3                          54M   54M     0 100% /snap/snapd/19457</span><br><span class="line">/dev/loop4                          64M   64M     0 100% /snap/core20/1950</span><br></pre></td></tr></table></figure></li>
+</ol>
+<h2 id="参考链接"><a href="#参考链接" class="headerlink" title="参考链接"></a>参考链接</h2><p><a href="https://blog.csdn.net/weixin_43302340/article/details/120341241">ubuntu20.04 server 安装后磁盘空间只有一半的处理</a><br><a href="https://askubuntu.com/questions/1269493/ubuntu-server-20-04-1-lts-not-all-disk-space-was-allocated-during-installation">Ubuntu Server 20.04.1 LTS, not all disk space was allocated during installation?</a></p>
+]]></content>
+      <tags>
+        <tag>linux</tag>
+        <tag>ubuntu</tag>
+      </tags>
+  </entry>
   <entry>
     <title>如何使用 SSH 连接 Github 和服务器</title>
     <url>/2023/06/28/how-to-use-ssh-to-connect-github-and-server/</url>
@@ -1694,6 +1642,123 @@
         <tag>tmux</tag>
       </tags>
   </entry>
+  <entry>
+    <title>Spring 应用 context 刷新流程</title>
+    <url>/2023/08/04/Spring-application-context-refresh-process/</url>
+    <content><![CDATA[<h3 id="context-刷新流程简单图解"><a href="#context-刷新流程简单图解" class="headerlink" title="context 刷新流程简单图解"></a>context 刷新流程简单图解</h3><h4 id="刷新流程"><a href="#刷新流程" class="headerlink" title="刷新流程"></a>刷新流程</h4><img src="/2023/08/04/Spring-application-context-refresh-process/Pasted%20image%2020231122005901.png" class="" title="Spring context 刷新流程">
+
+<h4 id="刷新流程中的组件"><a href="#刷新流程中的组件" class="headerlink" title="刷新流程中的组件"></a>刷新流程中的组件</h4><img src="/2023/08/04/Spring-application-context-refresh-process/Pasted%20image%2020231122021817.png" class="" title="Spring context 刷新流程中的组件">
+
+<h3 id="上下文刷新-AbstractApplicationContext-refresh"><a href="#上下文刷新-AbstractApplicationContext-refresh" class="headerlink" title="上下文刷新 AbstractApplicationContext#refresh"></a>上下文刷新 AbstractApplicationContext#refresh</h3><figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title function_">refresh</span><span class="params">()</span> <span class="keyword">throws</span> BeansException, IllegalStateException &#123;</span><br><span class="line">    <span class="comment">// 刷新和销毁的同步监视器。</span></span><br><span class="line">    <span class="keyword">synchronized</span> (<span class="built_in">this</span>.startupShutdownMonitor) &#123;</span><br><span class="line">        <span class="comment">// 1. 准备 context 以供刷新。</span></span><br><span class="line">        prepareRefresh();</span><br><span class="line">        <span class="comment">// 2. 告诉 context 子类刷新内部 beanFactory 并返回。</span></span><br><span class="line">        <span class="type">ConfigurableListableBeanFactory</span> <span class="variable">beanFactory</span> <span class="operator">=</span> obtainFreshBeanFactory();</span><br><span class="line">        <span class="comment">// 3. 准备 beanFactory 以供在此 context 中使用。</span></span><br><span class="line">        prepareBeanFactory(beanFactory);</span><br><span class="line">        <span class="keyword">try</span> &#123;</span><br><span class="line">            <span class="comment">// 4. 允许 context 子类对 bean 工厂进行后处理。</span></span><br><span class="line">            postProcessBeanFactory(beanFactory);</span><br><span class="line">            <span class="comment">// 5. 调用在 context 中注册为 bean 的工厂后处理器。</span></span><br><span class="line">            invokeBeanFactoryPostProcessors(beanFactory);</span><br><span class="line">            <span class="comment">// 6. 注册拦截 Bean 创建的 Bean 后处理器。</span></span><br><span class="line">            registerBeanPostProcessors(beanFactory);</span><br><span class="line">            <span class="comment">// 7. 初始化 context 的消息源。</span></span><br><span class="line">            initMessageSource();</span><br><span class="line">            <span class="comment">// 8. 为 context 初始化事件多播器。</span></span><br><span class="line">            initApplicationEventMulticaster();</span><br><span class="line">            <span class="comment">// 9. 在特定 context 子类中初始化其他特殊 bean。</span></span><br><span class="line">            onRefresh();</span><br><span class="line">            <span class="comment">// 10. 检查监听器 beans 并注册。</span></span><br><span class="line">            registerListeners();</span><br><span class="line">            <span class="comment">// 11. 实例化所有剩余的（非惰性初始化）单例。</span></span><br><span class="line">            finishBeanFactoryInitialization(beanFactory);</span><br><span class="line">            <span class="comment">// 12. 最后一步：发布相应的事件。</span></span><br><span class="line">            finishRefresh();</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="keyword">catch</span> (BeansException ex) &#123;</span><br><span class="line">            <span class="comment">// ...</span></span><br><span class="line">            <span class="comment">// 销毁已经创建的单例，以防止资源未正常释放。</span></span><br><span class="line">            destroyBeans();</span><br><span class="line">            <span class="comment">// 重置 &#x27;active&#x27; flag.</span></span><br><span class="line">            cancelRefresh(ex);</span><br><span class="line">            <span class="keyword">throw</span> ex;</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="keyword">finally</span> &#123;</span><br><span class="line">            resetCommonCaches();</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<h3 id="准备-context-以供刷新-prepareRefresh"><a href="#准备-context-以供刷新-prepareRefresh" class="headerlink" title="准备 context 以供刷新 prepareRefresh"></a>准备 context 以供刷新 prepareRefresh</h3><p>准备此 context 以供刷新，设置其启动日期和活动标志以及执行属性源的初始化。</p>
+<blockquote>
+<p>编写管理资源的容器时，可以参考。</p>
+</blockquote>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">protected</span> <span class="keyword">void</span> <span class="title function_">prepareRefresh</span><span class="params">()</span> &#123;</span><br><span class="line">    <span class="built_in">this</span>.startupDate = System.currentTimeMillis();</span><br><span class="line">    <span class="built_in">this</span>.closed.set(<span class="literal">false</span>);</span><br><span class="line">    <span class="built_in">this</span>.active.set(<span class="literal">true</span>);</span><br><span class="line">    <span class="keyword">if</span> (logger.isInfoEnabled()) &#123;</span><br><span class="line">        logger.info(<span class="string">&quot;Refreshing &quot;</span> + <span class="built_in">this</span>);</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="comment">// 初始化 PropertySource，默认什么都不做。</span></span><br><span class="line">    initPropertySources();</span><br><span class="line">    <span class="comment">// 校验所有被标记为 required 的 properties 都可以被解析。</span></span><br><span class="line">    getEnvironment().validateRequiredProperties();</span><br><span class="line">    <span class="comment">// 允许收集早期的 ApplicationEvents，当事件多播器可用就发送。</span></span><br><span class="line">    <span class="built_in">this</span>.earlyApplicationEvents = <span class="keyword">new</span> <span class="title class_">LinkedHashSet</span>&lt;ApplicationEvent&gt;();</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<h3 id="obtainFreshBeanFactory"><a href="#obtainFreshBeanFactory" class="headerlink" title="obtainFreshBeanFactory"></a>obtainFreshBeanFactory</h3><p>告诉子类刷新内部 bean 工厂并返回，返回的实例类型为 <strong>DefaultListableBeanFactory</strong>。在这里完成了配置文件的读取，初步注册了 bean 定义。</p>
+<blockquote>
+<p>我大概这辈子都不会想理清楚这里面关于 XML 文件的解析过程，但是我知道可以在这里观察到 beanFactory 因为配置文件注册了哪些 bean。</p>
+</blockquote>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">protected</span> ConfigurableListableBeanFactory <span class="title function_">obtainFreshBeanFactory</span><span class="params">()</span> &#123;</span><br><span class="line">    <span class="comment">// 刷新 beanFactory</span></span><br><span class="line">    <span class="comment">// 使用 XmlBeanDefinitionReader 加载配置文件中的 bean 定义</span></span><br><span class="line">    refreshBeanFactory();</span><br><span class="line">    <span class="comment">// 返回 beanFactory</span></span><br><span class="line">    <span class="type">ConfigurableListableBeanFactory</span> <span class="variable">beanFactory</span> <span class="operator">=</span> getBeanFactory();</span><br><span class="line">    <span class="keyword">if</span> (logger.isDebugEnabled()) &#123;</span><br><span class="line">        logger.debug(<span class="string">&quot;Bean factory for &quot;</span> + getDisplayName() + <span class="string">&quot;: &quot;</span> + beanFactory);</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="keyword">return</span> beanFactory;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<h3 id="准备-beanFactory"><a href="#准备-beanFactory" class="headerlink" title="准备 beanFactory"></a>准备 beanFactory</h3><p>配置 BeanFactory 以供在此 context 中使用，例如 context 的类加载器和一些后处理器，手动注册一些单例。</p>
+<ol>
+<li>为 beanFactory 配置 context 相关的资源，如类加载器</li>
+<li>添加 Bean 后处理器<ul>
+<li>ApplicationContextAwareProcessor，context 回调，注入特定类型时可触发自定义逻辑</li>
+<li>ApplicationListenerDetector，检测 ApplicationListener</li>
+</ul>
+</li>
+<li>手动注册单例</li>
+</ol>
+<blockquote>
+<p>ignoreDependencyInterface 和 registerResolvableDependency 在理解之后比单纯地记忆它们有趣许多。</p>
+</blockquote>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">protected</span> <span class="keyword">void</span> <span class="title function_">prepareBeanFactory</span><span class="params">(ConfigurableListableBeanFactory beanFactory)</span> &#123;</span><br><span class="line">    <span class="comment">// 告诉内部 beanFactory 使用 context 的类加载器等等。</span></span><br><span class="line">    beanFactory.setBeanClassLoader(getClassLoader());</span><br><span class="line">    beanFactory.setBeanExpressionResolver(<span class="keyword">new</span> <span class="title class_">StandardBeanExpressionResolver</span>(beanFactory.getBeanClassLoader()));</span><br><span class="line">    beanFactory.addPropertyEditorRegistrar(<span class="keyword">new</span> <span class="title class_">ResourceEditorRegistrar</span>(<span class="built_in">this</span>, getEnvironment()));</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 为内部 beanFactory 配置 context 回调。</span></span><br><span class="line">    beanFactory.addBeanPostProcessor(<span class="keyword">new</span> <span class="title class_">ApplicationContextAwareProcessor</span>(<span class="built_in">this</span>));</span><br><span class="line">    <span class="comment">// 如果一个 bean 的依赖实现了以下接口，忽略该依赖的检查和自动装配。</span></span><br><span class="line">    <span class="comment">// 例如在 populateBean 时，如果 bena 的依赖存在 set 方法，就会去解析，调用 getBean</span></span><br><span class="line">    <span class="comment">// 被设置 ignoreDependencyInterface 的依赖，仍然可以通过后置处理器进行依赖注入，例如以下的类型会使用上面那个后置处理器的回调方法注入。</span></span><br><span class="line">    <span class="comment">// 因此 @Autowire 这些通过后置处理器实现依赖注入的注解，也不会受影响</span></span><br><span class="line">    <span class="comment">// 这样设计的一个可能是往往注入这些类型时，希望触发某些事件。</span></span><br><span class="line">    beanFactory.ignoreDependencyInterface(EnvironmentAware.class);</span><br><span class="line">    beanFactory.ignoreDependencyInterface(EmbeddedValueResolverAware.class);</span><br><span class="line">    beanFactory.ignoreDependencyInterface(ResourceLoaderAware.class);</span><br><span class="line">    beanFactory.ignoreDependencyInterface(ApplicationEventPublisherAware.class);</span><br><span class="line">    beanFactory.ignoreDependencyInterface(MessageSourceAware.class);</span><br><span class="line">    beanFactory.ignoreDependencyInterface(ApplicationContextAware.class);</span><br><span class="line"></span><br><span class="line">    <span class="comment">// BeanFactory 之类的接口没有在普通工厂中注册为可解析类型，直接为它们指定 bean。</span></span><br><span class="line">    beanFactory.registerResolvableDependency(BeanFactory.class, beanFactory);</span><br><span class="line">    beanFactory.registerResolvableDependency(ResourceLoader.class, <span class="built_in">this</span>);</span><br><span class="line">    beanFactory.registerResolvableDependency(ApplicationEventPublisher.class, <span class="built_in">this</span>);</span><br><span class="line">    beanFactory.registerResolvableDependency(ApplicationContext.class, <span class="built_in">this</span>);</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 提前注册后处理器以检测内部 beans 是否是一个 ApplicationListener。</span></span><br><span class="line">    beanFactory.addBeanPostProcessor(<span class="keyword">new</span> <span class="title class_">ApplicationListenerDetector</span>(<span class="built_in">this</span>));</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 检测是否有 LoadTimeWeaver，如果存在就准备编织。</span></span><br><span class="line">    <span class="keyword">if</span> (beanFactory.containsBean(LOAD_TIME_WEAVER_BEAN_NAME)) &#123;</span><br><span class="line">        beanFactory.addBeanPostProcessor(<span class="keyword">new</span> <span class="title class_">LoadTimeWeaverAwareProcessor</span>(beanFactory));</span><br><span class="line">        <span class="comment">// Set a temporary ClassLoader for type matching.</span></span><br><span class="line">        beanFactory.setTempClassLoader(<span class="keyword">new</span> <span class="title class_">ContextTypeMatchClassLoader</span>(beanFactory.getBeanClassLoader()));</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 手动注册默认的环境 beans。</span></span><br><span class="line">    <span class="keyword">if</span> (!beanFactory.containsLocalBean(ENVIRONMENT_BEAN_NAME)) &#123;</span><br><span class="line">        beanFactory.registerSingleton(ENVIRONMENT_BEAN_NAME, getEnvironment());</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="keyword">if</span> (!beanFactory.containsLocalBean(SYSTEM_PROPERTIES_BEAN_NAME)) &#123;</span><br><span class="line">        beanFactory.registerSingleton(SYSTEM_PROPERTIES_BEAN_NAME, getEnvironment().getSystemProperties());</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="keyword">if</span> (!beanFactory.containsLocalBean(SYSTEM_ENVIRONMENT_BEAN_NAME)) &#123;</span><br><span class="line">        beanFactory.registerSingleton(SYSTEM_ENVIRONMENT_BEAN_NAME, getEnvironment().getSystemEnvironment());</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<blockquote>
+<p>在创建 Bean 开始前注册的单例，都属于手动注册的单例 manualSingletonNames</p>
+</blockquote>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title function_">registerSingleton</span><span class="params">(String beanName, Object singletonObject)</span> <span class="keyword">throws</span> IllegalStateException &#123;</span><br><span class="line">    <span class="built_in">super</span>.registerSingleton(beanName, singletonObject);</span><br><span class="line"></span><br><span class="line">    <span class="keyword">if</span> (hasBeanCreationStarted()) &#123;</span><br><span class="line">        <span class="comment">// Cannot modify startup-time collection elements anymore (for stable iteration)</span></span><br><span class="line">        <span class="keyword">synchronized</span> (<span class="built_in">this</span>.beanDefinitionMap) &#123;</span><br><span class="line">            <span class="keyword">if</span> (!<span class="built_in">this</span>.beanDefinitionMap.containsKey(beanName)) &#123;</span><br><span class="line">                Set&lt;String&gt; updatedSingletons = <span class="keyword">new</span> <span class="title class_">LinkedHashSet</span>&lt;String&gt;(<span class="built_in">this</span>.manualSingletonNames.size() + <span class="number">1</span>);</span><br><span class="line">                updatedSingletons.addAll(<span class="built_in">this</span>.manualSingletonNames);</span><br><span class="line">                updatedSingletons.add(beanName);</span><br><span class="line">                <span class="built_in">this</span>.manualSingletonNames = updatedSingletons;</span><br><span class="line">            &#125;</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="keyword">else</span> &#123;</span><br><span class="line">        <span class="comment">// Still in startup registration phase</span></span><br><span class="line">        <span class="keyword">if</span> (!<span class="built_in">this</span>.beanDefinitionMap.containsKey(beanName)) &#123;</span><br><span class="line">            <span class="built_in">this</span>.manualSingletonNames.add(beanName);</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    clearByTypeCache();</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<h3 id="postProcessBeanFactory"><a href="#postProcessBeanFactory" class="headerlink" title="postProcessBeanFactory"></a>postProcessBeanFactory</h3><p>在标准初始化后修改内部 beanFactory，默认什么都不做。</p>
+<h3 id="invokeBeanFactoryPostProcessors"><a href="#invokeBeanFactoryPostProcessors" class="headerlink" title="invokeBeanFactoryPostProcessors"></a>invokeBeanFactoryPostProcessors</h3><p>实例化并调用所有在 context 中注册的 beanFactory 后处理器，需遵循顺序规则。具体的处理被委托给 PostProcessorRegistrationDelegate。</p>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">protected</span> <span class="keyword">void</span> <span class="title function_">invokeBeanFactoryPostProcessors</span><span class="params">(ConfigurableListableBeanFactory beanFactory)</span> &#123;</span><br><span class="line">    PostProcessorRegistrationDelegate.invokeBeanFactoryPostProcessors(beanFactory, getBeanFactoryPostProcessors());</span><br><span class="line">    <span class="comment">// ...</span></span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<p>invokeBeanFactoryPostProcessors 方法堪比裹脚布。</p>
+<p><strong>关于调用顺序的规则</strong>：</p>
+<ol>
+<li>BeanFactoryPostProcessor 分为 context 添加的和 beanFactory 注册的，前者优于后者</li>
+<li>BeanFactoryPostProcessor 又可分为常规的和 BeanDefinitionRegistryPostProcessor，后者优于前者</li>
+<li>PriorityOrdered 优于 Ordered 优于剩余的</li>
+</ol>
+<p>可能新增 beanDefinition 的情况：</p>
+<ol>
+<li>BeanDefinitionRegistryPostProcessor 可能在 beanFactory 中引入新的 beanDefinition</li>
+</ol>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">invokeBeanFactoryPostProcessors</span><span class="params">(</span></span><br><span class="line"><span class="params">		ConfigurableListableBeanFactory beanFactory, List&lt;BeanFactoryPostProcessor&gt; beanFactoryPostProcessors)</span> &#123;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 存储已处理过的后处理器</span></span><br><span class="line">    Set&lt;String&gt; processedBeans = <span class="keyword">new</span> <span class="title class_">HashSet</span>&lt;String&gt;();</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 第一阶段：BeanDefinitionRegistryPostProcessor</span></span><br><span class="line">    <span class="keyword">if</span> (beanFactory <span class="keyword">instanceof</span> BeanDefinitionRegistry) &#123;</span><br><span class="line">        <span class="comment">// 如果 beanFactory 同时是 BeanDefinitionRegistry 类型</span></span><br><span class="line">        <span class="type">BeanDefinitionRegistry</span> <span class="variable">registry</span> <span class="operator">=</span> (BeanDefinitionRegistry) beanFactory;</span><br><span class="line">        <span class="comment">// 存储常规的 BeanFactoryPostProcessor</span></span><br><span class="line">        List&lt;BeanFactoryPostProcessor&gt; regularPostProcessors = <span class="keyword">new</span> <span class="title class_">LinkedList</span>&lt;BeanFactoryPostProcessor&gt;();</span><br><span class="line">        <span class="comment">// 存储 BeanDefinitionRegistryPostProcessor</span></span><br><span class="line">        List&lt;BeanDefinitionRegistryPostProcessor&gt; registryProcessors = <span class="keyword">new</span> <span class="title class_">LinkedList</span>&lt;BeanDefinitionRegistryPostProcessor&gt;();</span><br><span class="line"></span><br><span class="line">        <span class="comment">// 第 0 轮，先对 context 注册的 BeanFactoryPostProcessor 进行分类</span></span><br><span class="line">        <span class="keyword">for</span> (BeanFactoryPostProcessor postProcessor : beanFactoryPostProcessors) &#123;</span><br><span class="line">            <span class="keyword">if</span> (postProcessor <span class="keyword">instanceof</span> BeanDefinitionRegistryPostProcessor) &#123;</span><br><span class="line">                <span class="type">BeanDefinitionRegistryPostProcessor</span> <span class="variable">registryProcessor</span> <span class="operator">=</span></span><br><span class="line">                        (BeanDefinitionRegistryPostProcessor) postProcessor;</span><br><span class="line">                <span class="comment">// 分类的同时，直接调用 BeanDefinitionRegistryPostProcessor</span></span><br><span class="line">                registryProcessor.postProcessBeanDefinitionRegistry(registry);</span><br><span class="line">                registryProcessors.add(registryProcessor);</span><br><span class="line">            &#125;</span><br><span class="line">            <span class="keyword">else</span> &#123;</span><br><span class="line">                regularPostProcessors.add(postProcessor);</span><br><span class="line">            &#125;</span><br><span class="line">        &#125;</span><br><span class="line"></span><br><span class="line">        <span class="comment">// 将 BeanDefinitionRegistryPostProcessors 按是否实现 PriorityOrdered，Ordered，以及剩余的进行分类</span></span><br><span class="line">        List&lt;BeanDefinitionRegistryPostProcessor&gt; currentRegistryProcessors = <span class="keyword">new</span> <span class="title class_">ArrayList</span>&lt;BeanDefinitionRegistryPostProcessor&gt;();</span><br><span class="line"></span><br><span class="line">        <span class="comment">// 第 1 轮，先处理 beanFactory 中实现了 PriorityOrdered 的 BeanDefinitionRegistryPostProcessor</span></span><br><span class="line">        String[] postProcessorNames =</span><br><span class="line">                beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, <span class="literal">true</span>, <span class="literal">false</span>);</span><br><span class="line">        <span class="keyword">for</span> (String ppName : postProcessorNames) &#123;</span><br><span class="line">            <span class="keyword">if</span> (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) &#123;</span><br><span class="line">                <span class="comment">// getBean 并添加到当前的后处理器集合</span></span><br><span class="line">                currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));</span><br><span class="line">                processedBeans.add(ppName);</span><br><span class="line">            &#125;</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="comment">// 排序后添加</span></span><br><span class="line">        sortPostProcessors(currentRegistryProcessors, beanFactory);</span><br><span class="line">        registryProcessors.addAll(currentRegistryProcessors);</span><br><span class="line">        invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);</span><br><span class="line">        currentRegistryProcessors.clear();</span><br><span class="line"></span><br><span class="line">        <span class="comment">// 第 2 轮，Ordered</span></span><br><span class="line">        postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, <span class="literal">true</span>, <span class="literal">false</span>);</span><br><span class="line">        <span class="keyword">for</span> (String ppName : postProcessorNames) &#123;</span><br><span class="line">            <span class="keyword">if</span> (!processedBeans.contains(ppName) &amp;&amp; beanFactory.isTypeMatch(ppName, Ordered.class)) &#123;</span><br><span class="line">                currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));</span><br><span class="line">                processedBeans.add(ppName);</span><br><span class="line">            &#125;</span><br><span class="line">        &#125;</span><br><span class="line">        sortPostProcessors(currentRegistryProcessors, beanFactory);</span><br><span class="line">        registryProcessors.addAll(currentRegistryProcessors);</span><br><span class="line">        invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);</span><br><span class="line">        currentRegistryProcessors.clear();</span><br><span class="line"></span><br><span class="line">        <span class="comment">// 第 3 轮， 调用剩余的 BeanDefinitionRegistryPostProcessors 直到没有新的出现。</span></span><br><span class="line">        <span class="comment">// 后出现的 PriorityOrdered 不比前面的 Ordered 更早被处理</span></span><br><span class="line">        <span class="type">boolean</span> <span class="variable">reiterate</span> <span class="operator">=</span> <span class="literal">true</span>;</span><br><span class="line">        <span class="keyword">while</span> (reiterate) &#123;</span><br><span class="line">            reiterate = <span class="literal">false</span>;</span><br><span class="line">            postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, <span class="literal">true</span>, <span class="literal">false</span>);</span><br><span class="line">            <span class="keyword">for</span> (String ppName : postProcessorNames) &#123;</span><br><span class="line">                <span class="keyword">if</span> (!processedBeans.contains(ppName)) &#123;</span><br><span class="line">                    currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));</span><br><span class="line">                    processedBeans.add(ppName);</span><br><span class="line">                    reiterate = <span class="literal">true</span>;</span><br><span class="line">                &#125;</span><br><span class="line">            &#125;</span><br><span class="line">            sortPostProcessors(currentRegistryProcessors, beanFactory);</span><br><span class="line">            registryProcessors.addAll(currentRegistryProcessors);</span><br><span class="line">            invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);</span><br><span class="line">            currentRegistryProcessors.clear();</span><br><span class="line">        &#125;</span><br><span class="line"></span><br><span class="line">        <span class="comment">// 调用目前出现的 BeanFactoryPostProcessors</span></span><br><span class="line">        <span class="comment">// 仍遵循 PriorityOrdered、Ordered、Regular（registry）、Regular（context 添加的） 的顺序</span></span><br><span class="line">        invokeBeanFactoryPostProcessors(registryProcessors, beanFactory);</span><br><span class="line">        invokeBeanFactoryPostProcessors(regularPostProcessors, beanFactory);</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">else</span> &#123;</span><br><span class="line">        <span class="comment">// 否则，直接调用 context 注册的 beanFactoryPostProcessors</span></span><br><span class="line">        invokeBeanFactoryPostProcessors(beanFactoryPostProcessors, beanFactory);</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 第二阶段：BeanFactoryPostProcessor</span></span><br><span class="line">    String[] postProcessorNames =</span><br><span class="line">            beanFactory.getBeanNamesForType(BeanFactoryPostProcessor.class, <span class="literal">true</span>, <span class="literal">false</span>);</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 将 BeanFactoryPostProcessor 按是否实现 PriorityOrdered，Ordered，以及剩余的进行分类</span></span><br><span class="line">    List&lt;BeanFactoryPostProcessor&gt; priorityOrderedPostProcessors = <span class="keyword">new</span> <span class="title class_">ArrayList</span>&lt;BeanFactoryPostProcessor&gt;();</span><br><span class="line">    List&lt;String&gt; orderedPostProcessorNames = <span class="keyword">new</span> <span class="title class_">ArrayList</span>&lt;String&gt;();</span><br><span class="line">    List&lt;String&gt; nonOrderedPostProcessorNames = <span class="keyword">new</span> <span class="title class_">ArrayList</span>&lt;String&gt;();</span><br><span class="line">    <span class="keyword">for</span> (String ppName : postProcessorNames) &#123;</span><br><span class="line">        <span class="keyword">if</span> (processedBeans.contains(ppName)) &#123;</span><br><span class="line">            <span class="comment">// 第一阶段已处理，跳过</span></span><br><span class="line">        &#125;</span><br><span class="line">        <span class="keyword">else</span> <span class="keyword">if</span> (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) &#123;</span><br><span class="line">            priorityOrderedPostProcessors.add(beanFactory.getBean(ppName, BeanFactoryPostProcessor.class));</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="keyword">else</span> <span class="keyword">if</span> (beanFactory.isTypeMatch(ppName, Ordered.class)) &#123;</span><br><span class="line">            orderedPostProcessorNames.add(ppName);</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="keyword">else</span> &#123;</span><br><span class="line">            nonOrderedPostProcessorNames.add(ppName);</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 第 1 轮，BeanFactoryPostProcessors that implement PriorityOrdered.</span></span><br><span class="line">    sortPostProcessors(priorityOrderedPostProcessors, beanFactory);</span><br><span class="line">    invokeBeanFactoryPostProcessors(priorityOrderedPostProcessors, beanFactory);</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 第 2 轮，BeanFactoryPostProcessors that implement Ordered.</span></span><br><span class="line">    List&lt;BeanFactoryPostProcessor&gt; orderedPostProcessors = <span class="keyword">new</span> <span class="title class_">ArrayList</span>&lt;BeanFactoryPostProcessor&gt;();</span><br><span class="line">    <span class="keyword">for</span> (String postProcessorName : orderedPostProcessorNames) &#123;</span><br><span class="line">        orderedPostProcessors.add(beanFactory.getBean(postProcessorName, BeanFactoryPostProcessor.class));</span><br><span class="line">    &#125;</span><br><span class="line">    sortPostProcessors(orderedPostProcessors, beanFactory);</span><br><span class="line">    invokeBeanFactoryPostProcessors(orderedPostProcessors, beanFactory);</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 第 3 轮，剩余的 BeanFactoryPostProcessors.</span></span><br><span class="line">    List&lt;BeanFactoryPostProcessor&gt; nonOrderedPostProcessors = <span class="keyword">new</span> <span class="title class_">ArrayList</span>&lt;BeanFactoryPostProcessor&gt;();</span><br><span class="line">    <span class="keyword">for</span> (String postProcessorName : nonOrderedPostProcessorNames) &#123;</span><br><span class="line">        nonOrderedPostProcessors.add(beanFactory.getBean(postProcessorName, BeanFactoryPostProcessor.class));</span><br><span class="line">    &#125;</span><br><span class="line">    invokeBeanFactoryPostProcessors(nonOrderedPostProcessors, beanFactory);</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 清理缓存的 merged bean definitions 因为 post-processors 可能已经修改了原来的 metadata</span></span><br><span class="line">    beanFactory.clearMetadataCache();</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<h3 id="registerBeanPostProcessors"><a href="#registerBeanPostProcessors" class="headerlink" title="registerBeanPostProcessors"></a>registerBeanPostProcessors</h3><p>注册拦截 <code>bean</code> 创建的 <code>bean</code> 后处理器。具体的处理被委托给 PostProcessorRegistrationDelegate。</p>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">protected</span> <span class="keyword">void</span> <span class="title function_">registerBeanPostProcessors</span><span class="params">(ConfigurableListableBeanFactory beanFactory)</span> &#123;</span><br><span class="line">    PostProcessorRegistrationDelegate.registerBeanPostProcessors(beanFactory, <span class="built_in">this</span>);</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<p>registerBeanPostProcessors 相比之下是一条清新的裹脚布。这里特别区分 3 种类型的 Bean 后处理器：</p>
+<ul>
+<li>MergedBeanDefinitionPostProcessor</li>
+<li>InstantiationAwareBeanPostProcessor 感知实例化</li>
+<li>DestructionAwareBeanPostProcessor 感知销毁</li>
+</ul>
+<p>ApplicationListenerDetector 既是 MergedBeanDefinitionPostProcessor，又是 DestructionAwareBeanPostProcessor，在初始化后将 listener 加入，在销毁前将 listener 移除。</p>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">registerBeanPostProcessors</span><span class="params">(</span></span><br><span class="line"><span class="params">		ConfigurableListableBeanFactory beanFactory, AbstractApplicationContext applicationContext)</span> &#123;</span><br><span class="line">    <span class="comment">// 获取 BeanPostProcessor 的名称</span></span><br><span class="line">    String[] postProcessorNames = beanFactory.getBeanNamesForType(BeanPostProcessor.class, <span class="literal">true</span>, <span class="literal">false</span>);</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 注册 BeanPostProcessorChecker，在 BeanPostProcessor 实例化期间创建 bean 时，记录一条消息。</span></span><br><span class="line">    <span class="comment">// 即，当一个 bean 不能被所有 BeanPostProcessors 处理时，记录。</span></span><br><span class="line">    <span class="type">int</span> <span class="variable">beanProcessorTargetCount</span> <span class="operator">=</span> beanFactory.getBeanPostProcessorCount() + <span class="number">1</span> + postProcessorNames.length;</span><br><span class="line">    beanFactory.addBeanPostProcessor(<span class="keyword">new</span> <span class="title class_">BeanPostProcessorChecker</span>(beanFactory, beanProcessorTargetCount));</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 将 BeanPostProcessors 按 implement PriorityOrdered，Ordered，和剩余的进行分类。</span></span><br><span class="line">    List&lt;BeanPostProcessor&gt; priorityOrderedPostProcessors = <span class="keyword">new</span> <span class="title class_">ArrayList</span>&lt;BeanPostProcessor&gt;();</span><br><span class="line">    List&lt;BeanPostProcessor&gt; internalPostProcessors = <span class="keyword">new</span> <span class="title class_">ArrayList</span>&lt;BeanPostProcessor&gt;();</span><br><span class="line">    List&lt;String&gt; orderedPostProcessorNames = <span class="keyword">new</span> <span class="title class_">ArrayList</span>&lt;String&gt;();</span><br><span class="line">    List&lt;String&gt; nonOrderedPostProcessorNames = <span class="keyword">new</span> <span class="title class_">ArrayList</span>&lt;String&gt;();</span><br><span class="line">    <span class="keyword">for</span> (String ppName : postProcessorNames) &#123;</span><br><span class="line">        <span class="keyword">if</span> (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) &#123;</span><br><span class="line">            <span class="type">BeanPostProcessor</span> <span class="variable">pp</span> <span class="operator">=</span> beanFactory.getBean(ppName, BeanPostProcessor.class);</span><br><span class="line">            priorityOrderedPostProcessors.add(pp);</span><br><span class="line">            <span class="keyword">if</span> (pp <span class="keyword">instanceof</span> MergedBeanDefinitionPostProcessor) &#123;</span><br><span class="line">                internalPostProcessors.add(pp);</span><br><span class="line">            &#125;</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="keyword">else</span> <span class="keyword">if</span> (beanFactory.isTypeMatch(ppName, Ordered.class)) &#123;</span><br><span class="line">            orderedPostProcessorNames.add(ppName);</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="keyword">else</span> &#123;</span><br><span class="line">            nonOrderedPostProcessorNames.add(ppName);</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 第 1 轮，注册 BeanPostProcessors that implement PriorityOrdered.</span></span><br><span class="line">    sortPostProcessors(priorityOrderedPostProcessors, beanFactory);</span><br><span class="line">    registerBeanPostProcessors(beanFactory, priorityOrderedPostProcessors);</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 第 2 轮，注册 BeanPostProcessors that implement Ordered.</span></span><br><span class="line">    List&lt;BeanPostProcessor&gt; orderedPostProcessors = <span class="keyword">new</span> <span class="title class_">ArrayList</span>&lt;BeanPostProcessor&gt;();</span><br><span class="line">    <span class="keyword">for</span> (String ppName : orderedPostProcessorNames) &#123;</span><br><span class="line">        <span class="type">BeanPostProcessor</span> <span class="variable">pp</span> <span class="operator">=</span> beanFactory.getBean(ppName, BeanPostProcessor.class);</span><br><span class="line">        orderedPostProcessors.add(pp);</span><br><span class="line">        <span class="keyword">if</span> (pp <span class="keyword">instanceof</span> MergedBeanDefinitionPostProcessor) &#123;</span><br><span class="line">            internalPostProcessors.add(pp);</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line">    sortPostProcessors(orderedPostProcessors, beanFactory);</span><br><span class="line">    registerBeanPostProcessors(beanFactory, orderedPostProcessors);</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 第 3 轮，注册剩余的 regular BeanPostProcessors.</span></span><br><span class="line">    List&lt;BeanPostProcessor&gt; nonOrderedPostProcessors = <span class="keyword">new</span> <span class="title class_">ArrayList</span>&lt;BeanPostProcessor&gt;();</span><br><span class="line">    <span class="keyword">for</span> (String ppName : nonOrderedPostProcessorNames) &#123;</span><br><span class="line">        <span class="type">BeanPostProcessor</span> <span class="variable">pp</span> <span class="operator">=</span> beanFactory.getBean(ppName, BeanPostProcessor.class);</span><br><span class="line">        nonOrderedPostProcessors.add(pp);</span><br><span class="line">        <span class="keyword">if</span> (pp <span class="keyword">instanceof</span> MergedBeanDefinitionPostProcessor) &#123;</span><br><span class="line">            internalPostProcessors.add(pp);</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line">    registerBeanPostProcessors(beanFactory, nonOrderedPostProcessors);</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 最后（第 4 轮）, 排序并注册 internal BeanPostProcessors.</span></span><br><span class="line">    sortPostProcessors(internalPostProcessors, beanFactory);</span><br><span class="line">    registerBeanPostProcessors(beanFactory, internalPostProcessors);</span><br><span class="line"></span><br><span class="line">    <span class="comment">// Re-register post-processor for detecting inner beans as ApplicationListeners,</span></span><br><span class="line">    <span class="comment">// moving it to the end of the processor chain (for picking up proxies etc).</span></span><br><span class="line">    <span class="comment">// 重新注册用于检测 ApplicationListeners 的 Bean 后处理器，将其移动到处理器链的最后（用于获取代理）。</span></span><br><span class="line">    beanFactory.addBeanPostProcessor(<span class="keyword">new</span> <span class="title class_">ApplicationListenerDetector</span>(applicationContext));</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<p>添加 BeanPostProcessor 时</p>
+<ol>
+<li>先移除</li>
+<li>再添加</li>
+<li>判断类型并记录标记<ul>
+<li>感知实例化的后处理器</li>
+<li>感知销毁的后处理器</li>
+</ul>
+</li>
+</ol>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title function_">addBeanPostProcessor</span><span class="params">(BeanPostProcessor beanPostProcessor)</span> &#123;</span><br><span class="line">    Assert.notNull(beanPostProcessor, <span class="string">&quot;BeanPostProcessor must not be null&quot;</span>);</span><br><span class="line">    <span class="built_in">this</span>.beanPostProcessors.remove(beanPostProcessor);</span><br><span class="line">    <span class="built_in">this</span>.beanPostProcessors.add(beanPostProcessor);</span><br><span class="line">    <span class="keyword">if</span> (beanPostProcessor <span class="keyword">instanceof</span> InstantiationAwareBeanPostProcessor) &#123;</span><br><span class="line">        <span class="built_in">this</span>.hasInstantiationAwareBeanPostProcessors = <span class="literal">true</span>;</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="keyword">if</span> (beanPostProcessor <span class="keyword">instanceof</span> DestructionAwareBeanPostProcessor) &#123;</span><br><span class="line">        <span class="built_in">this</span>.hasDestructionAwareBeanPostProcessors = <span class="literal">true</span>;</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<h3 id="initMessageSource"><a href="#initMessageSource" class="headerlink" title="initMessageSource"></a>initMessageSource</h3><p>初始化消息源。 如果在此 context 中未定义，则使用父级的。</p>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">protected</span> <span class="keyword">void</span> <span class="title function_">initMessageSource</span><span class="params">()</span> &#123;</span><br><span class="line">    <span class="type">ConfigurableListableBeanFactory</span> <span class="variable">beanFactory</span> <span class="operator">=</span> getBeanFactory();</span><br><span class="line">    <span class="keyword">if</span> (beanFactory.containsLocalBean(MESSAGE_SOURCE_BEAN_NAME)) &#123;</span><br><span class="line">        <span class="built_in">this</span>.messageSource = beanFactory.getBean(MESSAGE_SOURCE_BEAN_NAME, MessageSource.class);</span><br><span class="line">        <span class="comment">// 设置 parent MessageSource.</span></span><br><span class="line">        <span class="keyword">if</span> (<span class="built_in">this</span>.parent != <span class="literal">null</span> &amp;&amp; <span class="built_in">this</span>.messageSource <span class="keyword">instanceof</span> HierarchicalMessageSource) &#123;</span><br><span class="line">            <span class="type">HierarchicalMessageSource</span> <span class="variable">hms</span> <span class="operator">=</span> (HierarchicalMessageSource) <span class="built_in">this</span>.messageSource;</span><br><span class="line">            <span class="keyword">if</span> (hms.getParentMessageSource() == <span class="literal">null</span>) &#123;</span><br><span class="line">                <span class="comment">// 只有当 parent MessageSource 尚未注册才将 parent context 设置为 parent MessageSource</span></span><br><span class="line">                hms.setParentMessageSource(getInternalParentMessageSource());</span><br><span class="line">            &#125;</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="keyword">if</span> (logger.isDebugEnabled()) &#123;</span><br><span class="line">            logger.debug(<span class="string">&quot;Using MessageSource [&quot;</span> + <span class="built_in">this</span>.messageSource + <span class="string">&quot;]&quot;</span>);</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="keyword">else</span> &#123;</span><br><span class="line">        <span class="comment">// 使用代理 messageSource，以此接收 getMessage 调用。</span></span><br><span class="line">        <span class="type">DelegatingMessageSource</span> <span class="variable">dms</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">DelegatingMessageSource</span>();</span><br><span class="line">        dms.setParentMessageSource(getInternalParentMessageSource());</span><br><span class="line">        <span class="built_in">this</span>.messageSource = dms;</span><br><span class="line">        beanFactory.registerSingleton(MESSAGE_SOURCE_BEAN_NAME, <span class="built_in">this</span>.messageSource);</span><br><span class="line">        <span class="keyword">if</span> (logger.isDebugEnabled()) &#123;</span><br><span class="line">            logger.debug(<span class="string">&quot;Unable to locate MessageSource with name &#x27;&quot;</span> + MESSAGE_SOURCE_BEAN_NAME +</span><br><span class="line">                    <span class="string">&quot;&#x27;: using default [&quot;</span> + <span class="built_in">this</span>.messageSource + <span class="string">&quot;]&quot;</span>);</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<h3 id="initApplicationEventMulticaster"><a href="#initApplicationEventMulticaster" class="headerlink" title="initApplicationEventMulticaster"></a>initApplicationEventMulticaster</h3><p>初始化 <code>ApplicationEventMulticaster</code>。 如果上下文中未定义，则使用 <code>SimpleApplicationEventMulticaster</code>。可以看得出代码的结构和 initMessageSource 是类似的。</p>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">protected</span> <span class="keyword">void</span> <span class="title function_">initApplicationEventMulticaster</span><span class="params">()</span> &#123;</span><br><span class="line">    <span class="type">ConfigurableListableBeanFactory</span> <span class="variable">beanFactory</span> <span class="operator">=</span> getBeanFactory();</span><br><span class="line">    <span class="keyword">if</span> (beanFactory.containsLocalBean(APPLICATION_EVENT_MULTICASTER_BEAN_NAME)) &#123;</span><br><span class="line">        <span class="built_in">this</span>.applicationEventMulticaster =</span><br><span class="line">                beanFactory.getBean(APPLICATION_EVENT_MULTICASTER_BEAN_NAME, ApplicationEventMulticaster.class);</span><br><span class="line">        <span class="keyword">if</span> (logger.isDebugEnabled()) &#123;</span><br><span class="line">            logger.debug(<span class="string">&quot;Using ApplicationEventMulticaster [&quot;</span> + <span class="built_in">this</span>.applicationEventMulticaster + <span class="string">&quot;]&quot;</span>);</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="keyword">else</span> &#123;</span><br><span class="line">        <span class="built_in">this</span>.applicationEventMulticaster = <span class="keyword">new</span> <span class="title class_">SimpleApplicationEventMulticaster</span>(beanFactory);</span><br><span class="line">        beanFactory.registerSingleton(APPLICATION_EVENT_MULTICASTER_BEAN_NAME, <span class="built_in">this</span>.applicationEventMulticaster);</span><br><span class="line">        <span class="keyword">if</span> (logger.isDebugEnabled()) &#123;</span><br><span class="line">            logger.debug(<span class="string">&quot;Unable to locate ApplicationEventMulticaster with name &#x27;&quot;</span> +</span><br><span class="line">                    APPLICATION_EVENT_MULTICASTER_BEAN_NAME +</span><br><span class="line">                    <span class="string">&quot;&#x27;: using default [&quot;</span> + <span class="built_in">this</span>.applicationEventMulticaster + <span class="string">&quot;]&quot;</span>);</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<h3 id="onRefresh"><a href="#onRefresh" class="headerlink" title="onRefresh"></a>onRefresh</h3><p>可以重写模板方法来添加特定 context 的刷新工作。默认情况下什么都不做。</p>
+<h3 id="registerListeners"><a href="#registerListeners" class="headerlink" title="registerListeners"></a>registerListeners</h3><p>获取侦听器 <code>bean</code> 并注册。无需初始化即可添加</p>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">protected</span> <span class="keyword">void</span> <span class="title function_">registerListeners</span><span class="params">()</span> &#123;</span><br><span class="line">    <span class="comment">// 注册静态指定的 ApplicationListener，和 beanFactoryPostProcessor 类似，context 可以提前添加好。</span></span><br><span class="line">    <span class="keyword">for</span> (ApplicationListener&lt;?&gt; listener : getApplicationListeners()) &#123;</span><br><span class="line">        getApplicationEventMulticaster().addApplicationListener(listener);</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// Do not initialize FactoryBeans here: We need to leave all regular beans</span></span><br><span class="line">    <span class="comment">// uninitialized to let post-processors apply to them!</span></span><br><span class="line">    <span class="comment">// 这段注释看到不止一次，但是不太理解，感觉和代码联系不起来？</span></span><br><span class="line">    String[] listenerBeanNames = getBeanNamesForType(ApplicationListener.class, <span class="literal">true</span>, <span class="literal">false</span>);</span><br><span class="line">    <span class="keyword">for</span> (String listenerBeanName : listenerBeanNames) &#123;</span><br><span class="line">        getApplicationEventMulticaster().addApplicationListenerBean(listenerBeanName);</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 现在我们终于有了多播器，发布早期的应用事件。</span></span><br><span class="line">    Set&lt;ApplicationEvent&gt; earlyEventsToProcess = <span class="built_in">this</span>.earlyApplicationEvents;</span><br><span class="line">    <span class="built_in">this</span>.earlyApplicationEvents = <span class="literal">null</span>;</span><br><span class="line">    <span class="keyword">if</span> (earlyEventsToProcess != <span class="literal">null</span>) &#123;</span><br><span class="line">        <span class="keyword">for</span> (ApplicationEvent earlyEvent : earlyEventsToProcess) &#123;</span><br><span class="line">            getApplicationEventMulticaster().multicastEvent(earlyEvent);</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<p>添加 ApplicationListener。</p>
+<blockquote>
+<p>后处理器 ApplicationListenerDetector 在 processor chain 的最后，最终会将创建的代理添加为监听器。什么情况下会出现代码中预防的情况呢？</p>
+</blockquote>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title function_">addApplicationListener</span><span class="params">(ApplicationListener&lt;?&gt; listener)</span> &#123;</span><br><span class="line">    <span class="keyword">synchronized</span> (<span class="built_in">this</span>.retrievalMutex) &#123;</span><br><span class="line">        <span class="comment">// 如果已经注册，需要显式地删除代理，以避免同一监听器的双重调用。</span></span><br><span class="line">        <span class="type">Object</span> <span class="variable">singletonTarget</span> <span class="operator">=</span> AopProxyUtils.getSingletonTarget(listener);</span><br><span class="line">        <span class="keyword">if</span> (singletonTarget <span class="keyword">instanceof</span> ApplicationListener) &#123;</span><br><span class="line">            <span class="built_in">this</span>.defaultRetriever.applicationListeners.remove(singletonTarget);</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="built_in">this</span>.defaultRetriever.applicationListeners.add(listener);</span><br><span class="line">        <span class="built_in">this</span>.retrieverCache.clear();</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<h3 id="finishBeanFactoryInitialization"><a href="#finishBeanFactoryInitialization" class="headerlink" title="finishBeanFactoryInitialization"></a>finishBeanFactoryInitialization</h3><p>实例化所有剩余的（非惰性初始化）单例。以 context 视角，是完成内部 beanFactory 的初始化。</p>
+<p>几乎可以只关注最后的 <code>beanFactory.preInstantiateSingletons()</code>。</p>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">protected</span> <span class="keyword">void</span> <span class="title function_">finishBeanFactoryInitialization</span><span class="params">(ConfigurableListableBeanFactory beanFactory)</span> &#123;</span><br><span class="line">    <span class="comment">// 为 context 初始化转换服务</span></span><br><span class="line">    <span class="keyword">if</span> (beanFactory.containsBean(CONVERSION_SERVICE_BEAN_NAME) &amp;&amp;</span><br><span class="line">            beanFactory.isTypeMatch(CONVERSION_SERVICE_BEAN_NAME, ConversionService.class)) &#123;</span><br><span class="line">        beanFactory.setConversionService(</span><br><span class="line">                beanFactory.getBean(CONVERSION_SERVICE_BEAN_NAME, ConversionService.class));</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 如果之前没有任何 bean 后处理器（例如 PropertyPlaceholderConfigurer）注册，则注册默认的嵌入值解析器，主要用于解析注释属性值。</span></span><br><span class="line">    <span class="comment">// 接口 ConfigurableEnvironment 继承自 ConfigurablePropertyResolver</span></span><br><span class="line">    <span class="keyword">if</span> (!beanFactory.hasEmbeddedValueResolver()) &#123;</span><br><span class="line">        beanFactory.addEmbeddedValueResolver(<span class="keyword">new</span> <span class="title class_">StringValueResolver</span>() &#123;</span><br><span class="line">            <span class="meta">@Override</span></span><br><span class="line">            <span class="keyword">public</span> String <span class="title function_">resolveStringValue</span><span class="params">(String strVal)</span> &#123;</span><br><span class="line">                <span class="keyword">return</span> getEnvironment().resolvePlaceholders(strVal);</span><br><span class="line">            &#125;</span><br><span class="line">        &#125;);</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 尽早初始化 LoadTimeWeaverAware，以便尽早注册其转换器。</span></span><br><span class="line">    String[] weaverAwareNames = beanFactory.getBeanNamesForType(LoadTimeWeaverAware.class, <span class="literal">false</span>, <span class="literal">false</span>);</span><br><span class="line">    <span class="keyword">for</span> (String weaverAwareName : weaverAwareNames) &#123;</span><br><span class="line">        getBean(weaverAwareName);</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 停止使用临时类加载器进行类型匹配。</span></span><br><span class="line">    beanFactory.setTempClassLoader(<span class="literal">null</span>);</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 允许缓存所有 bean 定义的元数据，而不期望进一步更改。</span></span><br><span class="line">    beanFactory.freezeConfiguration();</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 实例化所有剩余的（非惰性初始化）单例。</span></span><br><span class="line">    beanFactory.preInstantiateSingletons();</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<p>确保所有非惰性初始化单例都已实例化，同时还要考虑 <code>FactoryBeans</code>。 如果需要，通常在工厂设置结束时调用。</p>
+<a href="/2023/08/10/how-does-Spring-load-beans/" title="Spring Bean 加载过程">加载 Bean 的流程分析在此</a>。
+
+<blockquote>
+<p>先对集合进行 Copy 再迭代是很常见的处理方式，可以有效保证迭代时不受原集合影响，也不会影响到原集合。</p>
+</blockquote>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="meta">@Override</span></span><br><span class="line"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title function_">preInstantiateSingletons</span><span class="params">()</span> <span class="keyword">throws</span> BeansException &#123;</span><br><span class="line">    <span class="keyword">if</span> (<span class="built_in">this</span>.logger.isDebugEnabled()) &#123;</span><br><span class="line">        <span class="built_in">this</span>.logger.debug(<span class="string">&quot;Pre-instantiating singletons in &quot;</span> + <span class="built_in">this</span>);</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 拷贝一份 beanDefinitionNames</span></span><br><span class="line">    List&lt;String&gt; beanNames = <span class="keyword">new</span> <span class="title class_">ArrayList</span>&lt;String&gt;(<span class="built_in">this</span>.beanDefinitionNames);</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 触发所有非惰性初始化单例的实例化</span></span><br><span class="line">    <span class="keyword">for</span> (String beanName : beanNames) &#123;</span><br><span class="line">        <span class="type">RootBeanDefinition</span> <span class="variable">bd</span> <span class="operator">=</span> getMergedLocalBeanDefinition(beanName);</span><br><span class="line">        <span class="keyword">if</span> (!bd.isAbstract() &amp;&amp; bd.isSingleton() &amp;&amp; !bd.isLazyInit()) &#123;</span><br><span class="line">            <span class="keyword">if</span> (isFactoryBean(beanName)) &#123;</span><br><span class="line">                <span class="comment">// FactoryBean</span></span><br><span class="line">                <span class="keyword">final</span> FactoryBean&lt;?&gt; factory = (FactoryBean&lt;?&gt;) getBean(FACTORY_BEAN_PREFIX + beanName);</span><br><span class="line">                <span class="type">boolean</span> isEagerInit;</span><br><span class="line">                <span class="keyword">if</span> (System.getSecurityManager() != <span class="literal">null</span> &amp;&amp; factory <span class="keyword">instanceof</span> SmartFactoryBean) &#123;</span><br><span class="line">                    isEagerInit = AccessController.doPrivileged(<span class="keyword">new</span> <span class="title class_">PrivilegedAction</span>&lt;Boolean&gt;() &#123;</span><br><span class="line">                        <span class="meta">@Override</span></span><br><span class="line">                        <span class="keyword">public</span> Boolean <span class="title function_">run</span><span class="params">()</span> &#123;</span><br><span class="line">                            <span class="keyword">return</span> ((SmartFactoryBean&lt;?&gt;) factory).isEagerInit();</span><br><span class="line">                        &#125;</span><br><span class="line">                    &#125;, getAccessControlContext());</span><br><span class="line">                &#125;</span><br><span class="line">                <span class="keyword">else</span> &#123;</span><br><span class="line">                    isEagerInit = (factory <span class="keyword">instanceof</span> SmartFactoryBean &amp;&amp;</span><br><span class="line">                            ((SmartFactoryBean&lt;?&gt;) factory).isEagerInit());</span><br><span class="line">                &#125;</span><br><span class="line">                <span class="keyword">if</span> (isEagerInit) &#123;</span><br><span class="line">                    <span class="comment">// 是否立即初始化</span></span><br><span class="line">                    getBean(beanName);</span><br><span class="line">                &#125;</span><br><span class="line">            &#125;</span><br><span class="line">            <span class="keyword">else</span> &#123;</span><br><span class="line">                <span class="comment">// 常规 Bean（重要）</span></span><br><span class="line">                getBean(beanName);</span><br><span class="line">            &#125;</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 触发所有适用 bean 的初始化后回调</span></span><br><span class="line">    <span class="keyword">for</span> (String beanName : beanNames) &#123;</span><br><span class="line">        <span class="type">Object</span> <span class="variable">singletonInstance</span> <span class="operator">=</span> getSingleton(beanName);</span><br><span class="line">        <span class="keyword">if</span> (singletonInstance <span class="keyword">instanceof</span> SmartInitializingSingleton) &#123;</span><br><span class="line">            <span class="keyword">final</span> <span class="type">SmartInitializingSingleton</span> <span class="variable">smartSingleton</span> <span class="operator">=</span> (SmartInitializingSingleton) singletonInstance;</span><br><span class="line">            <span class="keyword">if</span> (System.getSecurityManager() != <span class="literal">null</span>) &#123;</span><br><span class="line">                AccessController.doPrivileged(<span class="keyword">new</span> <span class="title class_">PrivilegedAction</span>&lt;Object&gt;() &#123;</span><br><span class="line">                    <span class="meta">@Override</span></span><br><span class="line">                    <span class="keyword">public</span> Object <span class="title function_">run</span><span class="params">()</span> &#123;</span><br><span class="line">                        smartSingleton.afterSingletonsInstantiated();</span><br><span class="line">                        <span class="keyword">return</span> <span class="literal">null</span>;</span><br><span class="line">                    &#125;</span><br><span class="line">                &#125;, getAccessControlContext());</span><br><span class="line">            &#125;</span><br><span class="line">            <span class="keyword">else</span> &#123;</span><br><span class="line">                smartSingleton.afterSingletonsInstantiated();</span><br><span class="line">            &#125;</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<h3 id="finishRefresh"><a href="#finishRefresh" class="headerlink" title="finishRefresh"></a>finishRefresh</h3><p>最后一步，完成 context 刷新，比如发布相应的事件。</p>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">protected</span> <span class="keyword">void</span> <span class="title function_">finishRefresh</span><span class="params">()</span> &#123;</span><br><span class="line">    <span class="comment">// 1. 为此 context 初始化生命周期处理器。</span></span><br><span class="line">    initLifecycleProcessor();</span><br><span class="line">    <span class="comment">// 2. 将刷新传播到生命周期处理器。</span></span><br><span class="line">    getLifecycleProcessor().onRefresh();</span><br><span class="line">    <span class="comment">// 3. 发布 ContextRefreshedEvent。</span></span><br><span class="line">    publishEvent(<span class="keyword">new</span> <span class="title class_">ContextRefreshedEvent</span>(<span class="built_in">this</span>));</span><br><span class="line">    <span class="comment">// 4. 参与 LiveBeansView MBean（如果处于活动状态）。</span></span><br><span class="line">    LiveBeansView.registerApplicationContext(<span class="built_in">this</span>);</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>]]></content>
+      <tags>
+        <tag>java</tag>
+        <tag>spring</tag>
+      </tags>
+  </entry>
   <entry>
     <title>Java 类加载器源码分析</title>
     <url>/2023/07/13/Java-class-loader-source-code-analysis/</url>
@@ -2151,120 +2216,148 @@
       </tags>
   </entry>
   <entry>
-    <title>Spring 应用 context 刷新流程</title>
-    <url>/2023/08/04/Spring-application-context-refresh-process/</url>
-    <content><![CDATA[<h3 id="context-刷新流程简单图解"><a href="#context-刷新流程简单图解" class="headerlink" title="context 刷新流程简单图解"></a>context 刷新流程简单图解</h3><h4 id="刷新流程"><a href="#刷新流程" class="headerlink" title="刷新流程"></a>刷新流程</h4><img src="/2023/08/04/Spring-application-context-refresh-process/Pasted%20image%2020231122005901.png" class="" title="Spring context 刷新流程">
+    <title>JVM 内存区域的测试和分析</title>
+    <url>/2023/11/04/testing-and-analysis-of-jvm-memory-area/</url>
+    <content><![CDATA[<h2 id="内存区域"><a href="#内存区域" class="headerlink" title="内存区域"></a>内存区域</h2><p>JVM 内存区域划分为：</p>
+<ul>
+<li>程序计数器</li>
+<li>虚拟机栈</li>
+<li>本地方法栈</li>
+<li>堆</li>
+<li>方法区</li>
+</ul>
+<img src="/2023/11/04/testing-and-analysis-of-jvm-memory-area/Pasted%20image%2020231102215652.png" class="" title="内存区域划分">
 
-<h4 id="刷新流程中的组件"><a href="#刷新流程中的组件" class="headerlink" title="刷新流程中的组件"></a>刷新流程中的组件</h4><img src="/2023/08/04/Spring-application-context-refresh-process/Pasted%20image%2020231122021817.png" class="" title="Spring context 刷新流程中的组件">
+<h2 id="程序计数器"><a href="#程序计数器" class="headerlink" title="程序计数器"></a>程序计数器</h2><h2 id="虚拟机栈"><a href="#虚拟机栈" class="headerlink" title="虚拟机栈"></a>虚拟机栈</h2><p>Java 虚拟机栈（Java Virtual Machine Stack），线程私有，生命周期与线程相同。虚拟机栈描述的是 Java 方法执行的线程内存模型。每个方法被执行的时候，Java虚拟机都会同步创建一个栈帧（Stack Frame）用于存储局部变量表、操作数栈、动态连接、方法出口等信息。</p>
+<p>可以使用 <code>-Xss1024k</code> 设置虚拟机栈的大小。默认情况下都是 1024k，只有 Windows 中取决于虚拟内存。</p>
+<h3 id="栈内存溢出"><a href="#栈内存溢出" class="headerlink" title="栈内存溢出"></a>栈内存溢出</h3><ol>
+<li>栈帧过多导致栈内存溢出</li>
+<li>栈帧过大导致栈内存溢出（难复现）</li>
+</ol>
+<h4 id="不正确的递归调用"><a href="#不正确的递归调用" class="headerlink" title="不正确的递归调用"></a>不正确的递归调用</h4><figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">class</span> <span class="title class_">StackTest_4</span> &#123;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">static</span> <span class="type">int</span> <span class="variable">count</span> <span class="operator">=</span> <span class="number">0</span>;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 改变栈的大小限制 -Xss256k，观察调用次数的变化</span></span><br><span class="line">    <span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">main</span><span class="params">(String[] args)</span> &#123;</span><br><span class="line">        <span class="keyword">try</span> &#123;</span><br><span class="line">            method1();</span><br><span class="line">        &#125; <span class="keyword">catch</span> (Throwable t) &#123;</span><br><span class="line">            t.printStackTrace();</span><br><span class="line">        &#125; <span class="keyword">finally</span> &#123;</span><br><span class="line">            <span class="comment">// 默认情况下经过 20000+ 次，改变参数后 3000+ 次</span></span><br><span class="line">            System.out.println(count);</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">method1</span><span class="params">()</span> &#123;</span><br><span class="line">        count++;</span><br><span class="line">        method1();</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
 
-<h3 id="上下文刷新-AbstractApplicationContext-refresh"><a href="#上下文刷新-AbstractApplicationContext-refresh" class="headerlink" title="上下文刷新 AbstractApplicationContext#refresh"></a>上下文刷新 AbstractApplicationContext#refresh</h3><figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title function_">refresh</span><span class="params">()</span> <span class="keyword">throws</span> BeansException, IllegalStateException &#123;</span><br><span class="line">    <span class="comment">// 刷新和销毁的同步监视器。</span></span><br><span class="line">    <span class="keyword">synchronized</span> (<span class="built_in">this</span>.startupShutdownMonitor) &#123;</span><br><span class="line">        <span class="comment">// 1. 准备 context 以供刷新。</span></span><br><span class="line">        prepareRefresh();</span><br><span class="line">        <span class="comment">// 2. 告诉 context 子类刷新内部 beanFactory 并返回。</span></span><br><span class="line">        <span class="type">ConfigurableListableBeanFactory</span> <span class="variable">beanFactory</span> <span class="operator">=</span> obtainFreshBeanFactory();</span><br><span class="line">        <span class="comment">// 3. 准备 beanFactory 以供在此 context 中使用。</span></span><br><span class="line">        prepareBeanFactory(beanFactory);</span><br><span class="line">        <span class="keyword">try</span> &#123;</span><br><span class="line">            <span class="comment">// 4. 允许 context 子类对 bean 工厂进行后处理。</span></span><br><span class="line">            postProcessBeanFactory(beanFactory);</span><br><span class="line">            <span class="comment">// 5. 调用在 context 中注册为 bean 的工厂后处理器。</span></span><br><span class="line">            invokeBeanFactoryPostProcessors(beanFactory);</span><br><span class="line">            <span class="comment">// 6. 注册拦截 Bean 创建的 Bean 后处理器。</span></span><br><span class="line">            registerBeanPostProcessors(beanFactory);</span><br><span class="line">            <span class="comment">// 7. 初始化 context 的消息源。</span></span><br><span class="line">            initMessageSource();</span><br><span class="line">            <span class="comment">// 8. 为 context 初始化事件多播器。</span></span><br><span class="line">            initApplicationEventMulticaster();</span><br><span class="line">            <span class="comment">// 9. 在特定 context 子类中初始化其他特殊 bean。</span></span><br><span class="line">            onRefresh();</span><br><span class="line">            <span class="comment">// 10. 检查监听器 beans 并注册。</span></span><br><span class="line">            registerListeners();</span><br><span class="line">            <span class="comment">// 11. 实例化所有剩余的（非惰性初始化）单例。</span></span><br><span class="line">            finishBeanFactoryInitialization(beanFactory);</span><br><span class="line">            <span class="comment">// 12. 最后一步：发布相应的事件。</span></span><br><span class="line">            finishRefresh();</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="keyword">catch</span> (BeansException ex) &#123;</span><br><span class="line">            <span class="comment">// ...</span></span><br><span class="line">            <span class="comment">// 销毁已经创建的单例，以防止资源未正常释放。</span></span><br><span class="line">            destroyBeans();</span><br><span class="line">            <span class="comment">// 重置 &#x27;active&#x27; flag.</span></span><br><span class="line">            cancelRefresh(ex);</span><br><span class="line">            <span class="keyword">throw</span> ex;</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="keyword">finally</span> &#123;</span><br><span class="line">            resetCommonCaches();</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
 
-<h3 id="准备-context-以供刷新-prepareRefresh"><a href="#准备-context-以供刷新-prepareRefresh" class="headerlink" title="准备 context 以供刷新 prepareRefresh"></a>准备 context 以供刷新 prepareRefresh</h3><p>准备此 context 以供刷新，设置其启动日期和活动标志以及执行属性源的初始化。</p>
-<blockquote>
-<p>编写管理资源的容器时，可以参考。</p>
-</blockquote>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">protected</span> <span class="keyword">void</span> <span class="title function_">prepareRefresh</span><span class="params">()</span> &#123;</span><br><span class="line">    <span class="built_in">this</span>.startupDate = System.currentTimeMillis();</span><br><span class="line">    <span class="built_in">this</span>.closed.set(<span class="literal">false</span>);</span><br><span class="line">    <span class="built_in">this</span>.active.set(<span class="literal">true</span>);</span><br><span class="line">    <span class="keyword">if</span> (logger.isInfoEnabled()) &#123;</span><br><span class="line">        logger.info(<span class="string">&quot;Refreshing &quot;</span> + <span class="built_in">this</span>);</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="comment">// 初始化 PropertySource，默认什么都不做。</span></span><br><span class="line">    initPropertySources();</span><br><span class="line">    <span class="comment">// 校验所有被标记为 required 的 properties 都可以被解析。</span></span><br><span class="line">    getEnvironment().validateRequiredProperties();</span><br><span class="line">    <span class="comment">// 允许收集早期的 ApplicationEvents，当事件多播器可用就发送。</span></span><br><span class="line">    <span class="built_in">this</span>.earlyApplicationEvents = <span class="keyword">new</span> <span class="title class_">LinkedHashSet</span>&lt;ApplicationEvent&gt;();</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+<h4 id="循环引用导致-JSON-解析无限循环"><a href="#循环引用导致-JSON-解析无限循环" class="headerlink" title="循环引用导致 JSON 解析无限循环"></a>循环引用导致 JSON 解析无限循环</h4><p>并非只有自己写的递归方法可能引发栈内存溢出，有可能第三方库也会引发栈内存溢出。</p>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">class</span> <span class="title class_">StackTest_5</span> &#123;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">main</span><span class="params">(String[] args)</span> <span class="keyword">throws</span> JsonProcessingException &#123;</span><br><span class="line">        <span class="type">Department</span> <span class="variable">department</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">Department</span>();</span><br><span class="line">        department.setName(<span class="string">&quot;Tech&quot;</span>);</span><br><span class="line"></span><br><span class="line">        <span class="type">Employee</span> <span class="variable">employee1</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">Employee</span>();</span><br><span class="line">        employee1.setName(<span class="string">&quot;Tom&quot;</span>);</span><br><span class="line">        employee1.setDepartment(department);</span><br><span class="line"></span><br><span class="line">        <span class="type">Employee</span> <span class="variable">employee2</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">Employee</span>();</span><br><span class="line">        employee2.setName(<span class="string">&quot;Tim&quot;</span>);</span><br><span class="line">        employee2.setDepartment(department);</span><br><span class="line"></span><br><span class="line">        department.setEmployees(Arrays.asList(employee1, employee2));</span><br><span class="line"></span><br><span class="line">        <span class="type">ObjectMapper</span> <span class="variable">objectMapper</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">ObjectMapper</span>();</span><br><span class="line">        System.out.println(objectMapper.writeValueAsString(department));</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">static</span> <span class="keyword">class</span> <span class="title class_">Department</span> &#123;</span><br><span class="line">        <span class="keyword">private</span> String name;</span><br><span class="line">        <span class="keyword">private</span> List&lt;Employee&gt; employees;</span><br><span class="line"></span><br><span class="line">        <span class="keyword">public</span> String <span class="title function_">getName</span><span class="params">()</span> &#123;</span><br><span class="line">            <span class="keyword">return</span> name;</span><br><span class="line">        &#125;</span><br><span class="line"></span><br><span class="line">        <span class="keyword">public</span> <span class="keyword">void</span> <span class="title function_">setName</span><span class="params">(String name)</span> &#123;</span><br><span class="line">            <span class="built_in">this</span>.name = name;</span><br><span class="line">        &#125;</span><br><span class="line"></span><br><span class="line">        <span class="keyword">public</span> List&lt;Employee&gt; <span class="title function_">getEmployees</span><span class="params">()</span> &#123;</span><br><span class="line">            <span class="keyword">return</span> employees;</span><br><span class="line">        &#125;</span><br><span class="line"></span><br><span class="line">        <span class="keyword">public</span> <span class="keyword">void</span> <span class="title function_">setEmployees</span><span class="params">(List&lt;Employee&gt; employees)</span> &#123;</span><br><span class="line">            <span class="built_in">this</span>.employees = employees;</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">static</span> <span class="keyword">class</span> <span class="title class_">Employee</span> &#123;</span><br><span class="line">        <span class="keyword">private</span> String name;</span><br><span class="line">        <span class="keyword">private</span> Department department;</span><br><span class="line"></span><br><span class="line">        <span class="keyword">public</span> String <span class="title function_">getName</span><span class="params">()</span> &#123;</span><br><span class="line">            <span class="keyword">return</span> name;</span><br><span class="line">        &#125;</span><br><span class="line"></span><br><span class="line">        <span class="keyword">public</span> <span class="keyword">void</span> <span class="title function_">setName</span><span class="params">(String name)</span> &#123;</span><br><span class="line">            <span class="built_in">this</span>.name = name;</span><br><span class="line">        &#125;</span><br><span class="line"></span><br><span class="line">        <span class="keyword">public</span> Department <span class="title function_">getDepartment</span><span class="params">()</span> &#123;</span><br><span class="line">            <span class="keyword">return</span> department;</span><br><span class="line">        &#125;</span><br><span class="line"></span><br><span class="line">        <span class="keyword">public</span> <span class="keyword">void</span> <span class="title function_">setDepartment</span><span class="params">(Department department)</span> &#123;</span><br><span class="line">            <span class="built_in">this</span>.department = department;</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
 
-<h3 id="obtainFreshBeanFactory"><a href="#obtainFreshBeanFactory" class="headerlink" title="obtainFreshBeanFactory"></a>obtainFreshBeanFactory</h3><p>告诉子类刷新内部 bean 工厂并返回，返回的实例类型为 <strong>DefaultListableBeanFactory</strong>。在这里完成了配置文件的读取，初步注册了 bean 定义。</p>
-<blockquote>
-<p>我大概这辈子都不会想理清楚这里面关于 XML 文件的解析过程，但是我知道可以在这里观察到 beanFactory 因为配置文件注册了哪些 bean。</p>
-</blockquote>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">protected</span> ConfigurableListableBeanFactory <span class="title function_">obtainFreshBeanFactory</span><span class="params">()</span> &#123;</span><br><span class="line">    <span class="comment">// 刷新 beanFactory</span></span><br><span class="line">    <span class="comment">// 使用 XmlBeanDefinitionReader 加载配置文件中的 bean 定义</span></span><br><span class="line">    refreshBeanFactory();</span><br><span class="line">    <span class="comment">// 返回 beanFactory</span></span><br><span class="line">    <span class="type">ConfigurableListableBeanFactory</span> <span class="variable">beanFactory</span> <span class="operator">=</span> getBeanFactory();</span><br><span class="line">    <span class="keyword">if</span> (logger.isDebugEnabled()) &#123;</span><br><span class="line">        logger.debug(<span class="string">&quot;Bean factory for &quot;</span> + getDisplayName() + <span class="string">&quot;: &quot;</span> + beanFactory);</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="keyword">return</span> beanFactory;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+<h3 id="局部变量的线程安全问题"><a href="#局部变量的线程安全问题" class="headerlink" title="局部变量的线程安全问题"></a>局部变量的线程安全问题</h3><ol>
+<li>局部变量如果未逃离方法的作用范围，就是线程安全的。</li>
+<li>局部变量如果是引用类型且逃离了方法的作用范围，就是线程不安全的。</li>
+</ol>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">class</span> <span class="title class_">StackTest_3</span> &#123;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">main</span><span class="params">(String[] args)</span> &#123;</span><br><span class="line">        method1();</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 线程安全</span></span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">method1</span><span class="params">()</span> &#123;</span><br><span class="line">        <span class="type">StringBuilder</span> <span class="variable">sb</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">StringBuilder</span>();</span><br><span class="line">        sb.append(<span class="number">1</span>);</span><br><span class="line">        sb.append(<span class="number">2</span>);</span><br><span class="line">        sb.append(<span class="number">3</span>);</span><br><span class="line">        System.out.println(sb);</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 线程不安全</span></span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">method2</span><span class="params">(StringBuilder sb)</span> &#123;</span><br><span class="line">        sb.append(<span class="number">1</span>);</span><br><span class="line">        sb.append(<span class="number">2</span>);</span><br><span class="line">        sb.append(<span class="number">3</span>);</span><br><span class="line">        System.out.println(sb);</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 线程不安全，看到一个说法：发生指令重排，sb 的 append 操作发生在返回之后（有待确认）</span></span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">static</span> StringBuilder <span class="title function_">method3</span><span class="params">()</span> &#123;</span><br><span class="line">        <span class="type">StringBuilder</span> <span class="variable">sb</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">StringBuilder</span>();</span><br><span class="line">        sb.append(<span class="number">1</span>);</span><br><span class="line">        sb.append(<span class="number">2</span>);</span><br><span class="line">        sb.append(<span class="number">3</span>);</span><br><span class="line">        <span class="keyword">return</span> sb;</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
 
-<h3 id="准备-beanFactory"><a href="#准备-beanFactory" class="headerlink" title="准备 beanFactory"></a>准备 beanFactory</h3><p>配置 BeanFactory 以供在此 context 中使用，例如 context 的类加载器和一些后处理器，手动注册一些单例。</p>
+<h3 id="线程问题排查"><a href="#线程问题排查" class="headerlink" title="线程问题排查"></a>线程问题排查</h3><h4 id="CPU-占用率居高不下"><a href="#CPU-占用率居高不下" class="headerlink" title="CPU 占用率居高不下"></a>CPU 占用率居高不下</h4><figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">class</span> <span class="title class_">ThreadTest_1</span> &#123;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">main</span><span class="params">(String[] args)</span> &#123;</span><br><span class="line">        <span class="keyword">new</span> <span class="title class_">Thread</span>(<span class="literal">null</span>, () -&gt; &#123;</span><br><span class="line">            System.out.println(<span class="string">&quot;t1...&quot;</span>);</span><br><span class="line">            <span class="keyword">while</span> (<span class="literal">true</span>) &#123;</span><br><span class="line"></span><br><span class="line">            &#125;</span><br><span class="line">        &#125;, <span class="string">&quot;thread1&quot;</span>).start();</span><br><span class="line"></span><br><span class="line">        <span class="keyword">new</span> <span class="title class_">Thread</span>(<span class="literal">null</span>, () -&gt; &#123;</span><br><span class="line">            System.out.println(<span class="string">&quot;t2...&quot;</span>);</span><br><span class="line">            <span class="keyword">try</span> &#123;</span><br><span class="line">                TimeUnit.SECONDS.sleep(<span class="number">1000</span>);</span><br><span class="line">            &#125; <span class="keyword">catch</span> (InterruptedException e) &#123;</span><br><span class="line">                e.printStackTrace();</span><br><span class="line">            &#125;</span><br><span class="line">        &#125;, <span class="string">&quot;thread2&quot;</span>).start();</span><br><span class="line"></span><br><span class="line">        <span class="keyword">new</span> <span class="title class_">Thread</span>(<span class="literal">null</span>, () -&gt; &#123;</span><br><span class="line">            System.out.println(<span class="string">&quot;t3...&quot;</span>);</span><br><span class="line">            <span class="keyword">try</span> &#123;</span><br><span class="line">                TimeUnit.SECONDS.sleep(<span class="number">1000</span>);</span><br><span class="line">            &#125; <span class="keyword">catch</span> (InterruptedException e) &#123;</span><br><span class="line">                e.printStackTrace();</span><br><span class="line">            &#125;</span><br><span class="line">        &#125;, <span class="string">&quot;thread3&quot;</span>).start();</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+<p>当发现 CPU 占用率居高不下时，可以尝试以下步骤：</p>
 <ol>
-<li>为 beanFactory 配置 context 相关的资源，如类加载器</li>
-<li>添加 Bean 后处理器<ul>
-<li>ApplicationContextAwareProcessor，context 回调，注入特定类型时可触发自定义逻辑</li>
-<li>ApplicationListenerDetector，检测 ApplicationListener</li>
-</ul>
-</li>
-<li>手动注册单例</li>
+<li><code>top</code>，定位 cpu 占用高的进程 id。</li>
+<li><code>ps H -eo pid,tid,%cpu | grep pid</code>，进一步定位引起 cpu 占用高的线程 id。</li>
+<li><code>jstack pid</code>，根据线程 id 换算成 16进制的 nid 找到对应线程，进一步定位到问题的源码行号。</li>
 </ol>
-<blockquote>
-<p>ignoreDependencyInterface 和 registerResolvableDependency 在理解之后比单纯地记忆它们有趣许多。</p>
-</blockquote>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">protected</span> <span class="keyword">void</span> <span class="title function_">prepareBeanFactory</span><span class="params">(ConfigurableListableBeanFactory beanFactory)</span> &#123;</span><br><span class="line">    <span class="comment">// 告诉内部 beanFactory 使用 context 的类加载器等等。</span></span><br><span class="line">    beanFactory.setBeanClassLoader(getClassLoader());</span><br><span class="line">    beanFactory.setBeanExpressionResolver(<span class="keyword">new</span> <span class="title class_">StandardBeanExpressionResolver</span>(beanFactory.getBeanClassLoader()));</span><br><span class="line">    beanFactory.addPropertyEditorRegistrar(<span class="keyword">new</span> <span class="title class_">ResourceEditorRegistrar</span>(<span class="built_in">this</span>, getEnvironment()));</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 为内部 beanFactory 配置 context 回调。</span></span><br><span class="line">    beanFactory.addBeanPostProcessor(<span class="keyword">new</span> <span class="title class_">ApplicationContextAwareProcessor</span>(<span class="built_in">this</span>));</span><br><span class="line">    <span class="comment">// 如果一个 bean 的依赖实现了以下接口，忽略该依赖的检查和自动装配。</span></span><br><span class="line">    <span class="comment">// 例如在 populateBean 时，如果 bena 的依赖存在 set 方法，就会去解析，调用 getBean</span></span><br><span class="line">    <span class="comment">// 被设置 ignoreDependencyInterface 的依赖，仍然可以通过后置处理器进行依赖注入，例如以下的类型会使用上面那个后置处理器的回调方法注入。</span></span><br><span class="line">    <span class="comment">// 因此 @Autowire 这些通过后置处理器实现依赖注入的注解，也不会受影响</span></span><br><span class="line">    <span class="comment">// 这样设计的一个可能是往往注入这些类型时，希望触发某些事件。</span></span><br><span class="line">    beanFactory.ignoreDependencyInterface(EnvironmentAware.class);</span><br><span class="line">    beanFactory.ignoreDependencyInterface(EmbeddedValueResolverAware.class);</span><br><span class="line">    beanFactory.ignoreDependencyInterface(ResourceLoaderAware.class);</span><br><span class="line">    beanFactory.ignoreDependencyInterface(ApplicationEventPublisherAware.class);</span><br><span class="line">    beanFactory.ignoreDependencyInterface(MessageSourceAware.class);</span><br><span class="line">    beanFactory.ignoreDependencyInterface(ApplicationContextAware.class);</span><br><span class="line"></span><br><span class="line">    <span class="comment">// BeanFactory 之类的接口没有在普通工厂中注册为可解析类型，直接为它们指定 bean。</span></span><br><span class="line">    beanFactory.registerResolvableDependency(BeanFactory.class, beanFactory);</span><br><span class="line">    beanFactory.registerResolvableDependency(ResourceLoader.class, <span class="built_in">this</span>);</span><br><span class="line">    beanFactory.registerResolvableDependency(ApplicationEventPublisher.class, <span class="built_in">this</span>);</span><br><span class="line">    beanFactory.registerResolvableDependency(ApplicationContext.class, <span class="built_in">this</span>);</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 提前注册后处理器以检测内部 beans 是否是一个 ApplicationListener。</span></span><br><span class="line">    beanFactory.addBeanPostProcessor(<span class="keyword">new</span> <span class="title class_">ApplicationListenerDetector</span>(<span class="built_in">this</span>));</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 检测是否有 LoadTimeWeaver，如果存在就准备编织。</span></span><br><span class="line">    <span class="keyword">if</span> (beanFactory.containsBean(LOAD_TIME_WEAVER_BEAN_NAME)) &#123;</span><br><span class="line">        beanFactory.addBeanPostProcessor(<span class="keyword">new</span> <span class="title class_">LoadTimeWeaverAwareProcessor</span>(beanFactory));</span><br><span class="line">        <span class="comment">// Set a temporary ClassLoader for type matching.</span></span><br><span class="line">        beanFactory.setTempClassLoader(<span class="keyword">new</span> <span class="title class_">ContextTypeMatchClassLoader</span>(beanFactory.getBeanClassLoader()));</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 手动注册默认的环境 beans。</span></span><br><span class="line">    <span class="keyword">if</span> (!beanFactory.containsLocalBean(ENVIRONMENT_BEAN_NAME)) &#123;</span><br><span class="line">        beanFactory.registerSingleton(ENVIRONMENT_BEAN_NAME, getEnvironment());</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="keyword">if</span> (!beanFactory.containsLocalBean(SYSTEM_PROPERTIES_BEAN_NAME)) &#123;</span><br><span class="line">        beanFactory.registerSingleton(SYSTEM_PROPERTIES_BEAN_NAME, getEnvironment().getSystemProperties());</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="keyword">if</span> (!beanFactory.containsLocalBean(SYSTEM_ENVIRONMENT_BEAN_NAME)) &#123;</span><br><span class="line">        beanFactory.registerSingleton(SYSTEM_ENVIRONMENT_BEAN_NAME, getEnvironment().getSystemEnvironment());</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
-
-<blockquote>
-<p>在创建 Bean 开始前注册的单例，都属于手动注册的单例 manualSingletonNames</p>
-</blockquote>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title function_">registerSingleton</span><span class="params">(String beanName, Object singletonObject)</span> <span class="keyword">throws</span> IllegalStateException &#123;</span><br><span class="line">    <span class="built_in">super</span>.registerSingleton(beanName, singletonObject);</span><br><span class="line"></span><br><span class="line">    <span class="keyword">if</span> (hasBeanCreationStarted()) &#123;</span><br><span class="line">        <span class="comment">// Cannot modify startup-time collection elements anymore (for stable iteration)</span></span><br><span class="line">        <span class="keyword">synchronized</span> (<span class="built_in">this</span>.beanDefinitionMap) &#123;</span><br><span class="line">            <span class="keyword">if</span> (!<span class="built_in">this</span>.beanDefinitionMap.containsKey(beanName)) &#123;</span><br><span class="line">                Set&lt;String&gt; updatedSingletons = <span class="keyword">new</span> <span class="title class_">LinkedHashSet</span>&lt;String&gt;(<span class="built_in">this</span>.manualSingletonNames.size() + <span class="number">1</span>);</span><br><span class="line">                updatedSingletons.addAll(<span class="built_in">this</span>.manualSingletonNames);</span><br><span class="line">                updatedSingletons.add(beanName);</span><br><span class="line">                <span class="built_in">this</span>.manualSingletonNames = updatedSingletons;</span><br><span class="line">            &#125;</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="keyword">else</span> &#123;</span><br><span class="line">        <span class="comment">// Still in startup registration phase</span></span><br><span class="line">        <span class="keyword">if</span> (!<span class="built_in">this</span>.beanDefinitionMap.containsKey(beanName)) &#123;</span><br><span class="line">            <span class="built_in">this</span>.manualSingletonNames.add(beanName);</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    clearByTypeCache();</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+<figure class="highlight console"><table><tr><td class="code"><pre><span class="line">&quot;thread1&quot; #8 prio=5 os_prio=0 tid=0x00007f9bd0162800 nid=0x1061ad runnable [0x00007f9bd56eb000]</span><br><span class="line">   java.lang.Thread.State: RUNNABLE</span><br><span class="line">	at com.moralok.jvm.thread.ThreadTest_1.lambda$main$0(ThreadTest_1.java:10)</span><br><span class="line">	at com.moralok.jvm.thread.ThreadTest_1$$Lambda$1/250421012.run(Unknown Source)</span><br><span class="line">	at java.lang.Thread.run(Thread.java:750)</span><br></pre></td></tr></table></figure>
 
-<h3 id="postProcessBeanFactory"><a href="#postProcessBeanFactory" class="headerlink" title="postProcessBeanFactory"></a>postProcessBeanFactory</h3><p>在标准初始化后修改内部 beanFactory，默认什么都不做。</p>
-<h3 id="invokeBeanFactoryPostProcessors"><a href="#invokeBeanFactoryPostProcessors" class="headerlink" title="invokeBeanFactoryPostProcessors"></a>invokeBeanFactoryPostProcessors</h3><p>实例化并调用所有在 context 中注册的 beanFactory 后处理器，需遵循顺序规则。具体的处理被委托给 PostProcessorRegistrationDelegate。</p>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">protected</span> <span class="keyword">void</span> <span class="title function_">invokeBeanFactoryPostProcessors</span><span class="params">(ConfigurableListableBeanFactory beanFactory)</span> &#123;</span><br><span class="line">    PostProcessorRegistrationDelegate.invokeBeanFactoryPostProcessors(beanFactory, getBeanFactoryPostProcessors());</span><br><span class="line">    <span class="comment">// ...</span></span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+<h4 id="死锁，迟迟未返回结果"><a href="#死锁，迟迟未返回结果" class="headerlink" title="死锁，迟迟未返回结果"></a>死锁，迟迟未返回结果</h4><figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">class</span> <span class="title class_">ThreadTest_2</span> &#123;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">static</span> <span class="keyword">final</span> <span class="type">Object</span> <span class="variable">A</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">Object</span>();</span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">static</span> <span class="keyword">final</span> <span class="type">Object</span> <span class="variable">B</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">Object</span>();</span><br><span class="line"></span><br><span class="line">    <span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">main</span><span class="params">(String[] args)</span> &#123;</span><br><span class="line">        <span class="keyword">new</span> <span class="title class_">Thread</span>(<span class="literal">null</span>, () -&gt; &#123;</span><br><span class="line">            System.out.println(<span class="string">&quot;t1...&quot;</span>);</span><br><span class="line">            <span class="keyword">synchronized</span> (A) &#123;</span><br><span class="line">                System.out.println(Thread.currentThread().getName() + <span class="string">&quot; get A&quot;</span>);</span><br><span class="line">                <span class="keyword">try</span> &#123;</span><br><span class="line">                    TimeUnit.SECONDS.sleep(<span class="number">5</span>);</span><br><span class="line">                &#125; <span class="keyword">catch</span> (InterruptedException e) &#123;</span><br><span class="line">                    <span class="keyword">throw</span> <span class="keyword">new</span> <span class="title class_">RuntimeException</span>(e);</span><br><span class="line">                &#125;</span><br><span class="line">                <span class="keyword">synchronized</span> (B) &#123;</span><br><span class="line">                    System.out.println(Thread.currentThread().getName() + <span class="string">&quot; get B&quot;</span>);</span><br><span class="line">                &#125;</span><br><span class="line">            &#125;</span><br><span class="line">        &#125;, <span class="string">&quot;thread1&quot;</span>).start();</span><br><span class="line"></span><br><span class="line">        <span class="keyword">new</span> <span class="title class_">Thread</span>(<span class="literal">null</span>, () -&gt; &#123;</span><br><span class="line">            System.out.println(<span class="string">&quot;t2...&quot;</span>);</span><br><span class="line">            <span class="keyword">synchronized</span> (B) &#123;</span><br><span class="line">                System.out.println(Thread.currentThread().getName() + <span class="string">&quot; get B&quot;</span>);</span><br><span class="line">                <span class="keyword">try</span> &#123;</span><br><span class="line">                    TimeUnit.SECONDS.sleep(<span class="number">5</span>);</span><br><span class="line">                &#125; <span class="keyword">catch</span> (InterruptedException e) &#123;</span><br><span class="line">                    <span class="keyword">throw</span> <span class="keyword">new</span> <span class="title class_">RuntimeException</span>(e);</span><br><span class="line">                &#125;</span><br><span class="line">                <span class="keyword">synchronized</span> (A) &#123;</span><br><span class="line">                    System.out.println(Thread.currentThread().getName() + <span class="string">&quot; get A&quot;</span>);</span><br><span class="line">                &#125;</span><br><span class="line">            &#125;</span><br><span class="line">        &#125;, <span class="string">&quot;thread2&quot;</span>).start();</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
 
-<p>invokeBeanFactoryPostProcessors 方法堪比裹脚布。</p>
-<p><strong>关于调用顺序的规则</strong>：</p>
 <ol>
-<li>BeanFactoryPostProcessor 分为 context 添加的和 beanFactory 注册的，前者优于后者</li>
-<li>BeanFactoryPostProcessor 又可分为常规的和 BeanDefinitionRegistryPostProcessor，后者优于前者</li>
-<li>PriorityOrdered 优于 Ordered 优于剩余的</li>
+<li><code>jstack pid</code>，会显示找到死锁，以及死锁涉及的线程,，并各自持有的锁还有等待的锁。</li>
+<li>其他工具如 jconsole 也具有检测死锁的功能。</li>
 </ol>
-<p>可能新增 beanDefinition 的情况：</p>
+<h2 id="本地方法栈"><a href="#本地方法栈" class="headerlink" title="本地方法栈"></a>本地方法栈</h2><h2 id="堆"><a href="#堆" class="headerlink" title="堆"></a>堆</h2><p>堆（Heap）的特点：</p>
 <ol>
-<li>BeanDefinitionRegistryPostProcessor 可能在 beanFactory 中引入新的 beanDefinition</li>
+<li>线程共享，需要考虑线程安全问题。</li>
+<li>存在垃圾回收机制。</li>
+<li>使用 -Xmx8m 设置大小。</li>
 </ol>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">invokeBeanFactoryPostProcessors</span><span class="params">(</span></span><br><span class="line"><span class="params">		ConfigurableListableBeanFactory beanFactory, List&lt;BeanFactoryPostProcessor&gt; beanFactoryPostProcessors)</span> &#123;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 存储已处理过的后处理器</span></span><br><span class="line">    Set&lt;String&gt; processedBeans = <span class="keyword">new</span> <span class="title class_">HashSet</span>&lt;String&gt;();</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 第一阶段：BeanDefinitionRegistryPostProcessor</span></span><br><span class="line">    <span class="keyword">if</span> (beanFactory <span class="keyword">instanceof</span> BeanDefinitionRegistry) &#123;</span><br><span class="line">        <span class="comment">// 如果 beanFactory 同时是 BeanDefinitionRegistry 类型</span></span><br><span class="line">        <span class="type">BeanDefinitionRegistry</span> <span class="variable">registry</span> <span class="operator">=</span> (BeanDefinitionRegistry) beanFactory;</span><br><span class="line">        <span class="comment">// 存储常规的 BeanFactoryPostProcessor</span></span><br><span class="line">        List&lt;BeanFactoryPostProcessor&gt; regularPostProcessors = <span class="keyword">new</span> <span class="title class_">LinkedList</span>&lt;BeanFactoryPostProcessor&gt;();</span><br><span class="line">        <span class="comment">// 存储 BeanDefinitionRegistryPostProcessor</span></span><br><span class="line">        List&lt;BeanDefinitionRegistryPostProcessor&gt; registryProcessors = <span class="keyword">new</span> <span class="title class_">LinkedList</span>&lt;BeanDefinitionRegistryPostProcessor&gt;();</span><br><span class="line"></span><br><span class="line">        <span class="comment">// 第 0 轮，先对 context 注册的 BeanFactoryPostProcessor 进行分类</span></span><br><span class="line">        <span class="keyword">for</span> (BeanFactoryPostProcessor postProcessor : beanFactoryPostProcessors) &#123;</span><br><span class="line">            <span class="keyword">if</span> (postProcessor <span class="keyword">instanceof</span> BeanDefinitionRegistryPostProcessor) &#123;</span><br><span class="line">                <span class="type">BeanDefinitionRegistryPostProcessor</span> <span class="variable">registryProcessor</span> <span class="operator">=</span></span><br><span class="line">                        (BeanDefinitionRegistryPostProcessor) postProcessor;</span><br><span class="line">                <span class="comment">// 分类的同时，直接调用 BeanDefinitionRegistryPostProcessor</span></span><br><span class="line">                registryProcessor.postProcessBeanDefinitionRegistry(registry);</span><br><span class="line">                registryProcessors.add(registryProcessor);</span><br><span class="line">            &#125;</span><br><span class="line">            <span class="keyword">else</span> &#123;</span><br><span class="line">                regularPostProcessors.add(postProcessor);</span><br><span class="line">            &#125;</span><br><span class="line">        &#125;</span><br><span class="line"></span><br><span class="line">        <span class="comment">// 将 BeanDefinitionRegistryPostProcessors 按是否实现 PriorityOrdered，Ordered，以及剩余的进行分类</span></span><br><span class="line">        List&lt;BeanDefinitionRegistryPostProcessor&gt; currentRegistryProcessors = <span class="keyword">new</span> <span class="title class_">ArrayList</span>&lt;BeanDefinitionRegistryPostProcessor&gt;();</span><br><span class="line"></span><br><span class="line">        <span class="comment">// 第 1 轮，先处理 beanFactory 中实现了 PriorityOrdered 的 BeanDefinitionRegistryPostProcessor</span></span><br><span class="line">        String[] postProcessorNames =</span><br><span class="line">                beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, <span class="literal">true</span>, <span class="literal">false</span>);</span><br><span class="line">        <span class="keyword">for</span> (String ppName : postProcessorNames) &#123;</span><br><span class="line">            <span class="keyword">if</span> (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) &#123;</span><br><span class="line">                <span class="comment">// getBean 并添加到当前的后处理器集合</span></span><br><span class="line">                currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));</span><br><span class="line">                processedBeans.add(ppName);</span><br><span class="line">            &#125;</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="comment">// 排序后添加</span></span><br><span class="line">        sortPostProcessors(currentRegistryProcessors, beanFactory);</span><br><span class="line">        registryProcessors.addAll(currentRegistryProcessors);</span><br><span class="line">        invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);</span><br><span class="line">        currentRegistryProcessors.clear();</span><br><span class="line"></span><br><span class="line">        <span class="comment">// 第 2 轮，Ordered</span></span><br><span class="line">        postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, <span class="literal">true</span>, <span class="literal">false</span>);</span><br><span class="line">        <span class="keyword">for</span> (String ppName : postProcessorNames) &#123;</span><br><span class="line">            <span class="keyword">if</span> (!processedBeans.contains(ppName) &amp;&amp; beanFactory.isTypeMatch(ppName, Ordered.class)) &#123;</span><br><span class="line">                currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));</span><br><span class="line">                processedBeans.add(ppName);</span><br><span class="line">            &#125;</span><br><span class="line">        &#125;</span><br><span class="line">        sortPostProcessors(currentRegistryProcessors, beanFactory);</span><br><span class="line">        registryProcessors.addAll(currentRegistryProcessors);</span><br><span class="line">        invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);</span><br><span class="line">        currentRegistryProcessors.clear();</span><br><span class="line"></span><br><span class="line">        <span class="comment">// 第 3 轮， 调用剩余的 BeanDefinitionRegistryPostProcessors 直到没有新的出现。</span></span><br><span class="line">        <span class="comment">// 后出现的 PriorityOrdered 不比前面的 Ordered 更早被处理</span></span><br><span class="line">        <span class="type">boolean</span> <span class="variable">reiterate</span> <span class="operator">=</span> <span class="literal">true</span>;</span><br><span class="line">        <span class="keyword">while</span> (reiterate) &#123;</span><br><span class="line">            reiterate = <span class="literal">false</span>;</span><br><span class="line">            postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, <span class="literal">true</span>, <span class="literal">false</span>);</span><br><span class="line">            <span class="keyword">for</span> (String ppName : postProcessorNames) &#123;</span><br><span class="line">                <span class="keyword">if</span> (!processedBeans.contains(ppName)) &#123;</span><br><span class="line">                    currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));</span><br><span class="line">                    processedBeans.add(ppName);</span><br><span class="line">                    reiterate = <span class="literal">true</span>;</span><br><span class="line">                &#125;</span><br><span class="line">            &#125;</span><br><span class="line">            sortPostProcessors(currentRegistryProcessors, beanFactory);</span><br><span class="line">            registryProcessors.addAll(currentRegistryProcessors);</span><br><span class="line">            invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);</span><br><span class="line">            currentRegistryProcessors.clear();</span><br><span class="line">        &#125;</span><br><span class="line"></span><br><span class="line">        <span class="comment">// 调用目前出现的 BeanFactoryPostProcessors</span></span><br><span class="line">        <span class="comment">// 仍遵循 PriorityOrdered、Ordered、Regular（registry）、Regular（context 添加的） 的顺序</span></span><br><span class="line">        invokeBeanFactoryPostProcessors(registryProcessors, beanFactory);</span><br><span class="line">        invokeBeanFactoryPostProcessors(regularPostProcessors, beanFactory);</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">else</span> &#123;</span><br><span class="line">        <span class="comment">// 否则，直接调用 context 注册的 beanFactoryPostProcessors</span></span><br><span class="line">        invokeBeanFactoryPostProcessors(beanFactoryPostProcessors, beanFactory);</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 第二阶段：BeanFactoryPostProcessor</span></span><br><span class="line">    String[] postProcessorNames =</span><br><span class="line">            beanFactory.getBeanNamesForType(BeanFactoryPostProcessor.class, <span class="literal">true</span>, <span class="literal">false</span>);</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 将 BeanFactoryPostProcessor 按是否实现 PriorityOrdered，Ordered，以及剩余的进行分类</span></span><br><span class="line">    List&lt;BeanFactoryPostProcessor&gt; priorityOrderedPostProcessors = <span class="keyword">new</span> <span class="title class_">ArrayList</span>&lt;BeanFactoryPostProcessor&gt;();</span><br><span class="line">    List&lt;String&gt; orderedPostProcessorNames = <span class="keyword">new</span> <span class="title class_">ArrayList</span>&lt;String&gt;();</span><br><span class="line">    List&lt;String&gt; nonOrderedPostProcessorNames = <span class="keyword">new</span> <span class="title class_">ArrayList</span>&lt;String&gt;();</span><br><span class="line">    <span class="keyword">for</span> (String ppName : postProcessorNames) &#123;</span><br><span class="line">        <span class="keyword">if</span> (processedBeans.contains(ppName)) &#123;</span><br><span class="line">            <span class="comment">// 第一阶段已处理，跳过</span></span><br><span class="line">        &#125;</span><br><span class="line">        <span class="keyword">else</span> <span class="keyword">if</span> (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) &#123;</span><br><span class="line">            priorityOrderedPostProcessors.add(beanFactory.getBean(ppName, BeanFactoryPostProcessor.class));</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="keyword">else</span> <span class="keyword">if</span> (beanFactory.isTypeMatch(ppName, Ordered.class)) &#123;</span><br><span class="line">            orderedPostProcessorNames.add(ppName);</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="keyword">else</span> &#123;</span><br><span class="line">            nonOrderedPostProcessorNames.add(ppName);</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 第 1 轮，BeanFactoryPostProcessors that implement PriorityOrdered.</span></span><br><span class="line">    sortPostProcessors(priorityOrderedPostProcessors, beanFactory);</span><br><span class="line">    invokeBeanFactoryPostProcessors(priorityOrderedPostProcessors, beanFactory);</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 第 2 轮，BeanFactoryPostProcessors that implement Ordered.</span></span><br><span class="line">    List&lt;BeanFactoryPostProcessor&gt; orderedPostProcessors = <span class="keyword">new</span> <span class="title class_">ArrayList</span>&lt;BeanFactoryPostProcessor&gt;();</span><br><span class="line">    <span class="keyword">for</span> (String postProcessorName : orderedPostProcessorNames) &#123;</span><br><span class="line">        orderedPostProcessors.add(beanFactory.getBean(postProcessorName, BeanFactoryPostProcessor.class));</span><br><span class="line">    &#125;</span><br><span class="line">    sortPostProcessors(orderedPostProcessors, beanFactory);</span><br><span class="line">    invokeBeanFactoryPostProcessors(orderedPostProcessors, beanFactory);</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 第 3 轮，剩余的 BeanFactoryPostProcessors.</span></span><br><span class="line">    List&lt;BeanFactoryPostProcessor&gt; nonOrderedPostProcessors = <span class="keyword">new</span> <span class="title class_">ArrayList</span>&lt;BeanFactoryPostProcessor&gt;();</span><br><span class="line">    <span class="keyword">for</span> (String postProcessorName : nonOrderedPostProcessorNames) &#123;</span><br><span class="line">        nonOrderedPostProcessors.add(beanFactory.getBean(postProcessorName, BeanFactoryPostProcessor.class));</span><br><span class="line">    &#125;</span><br><span class="line">    invokeBeanFactoryPostProcessors(nonOrderedPostProcessors, beanFactory);</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 清理缓存的 merged bean definitions 因为 post-processors 可能已经修改了原来的 metadata</span></span><br><span class="line">    beanFactory.clearMetadataCache();</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+<h3 id="堆内存溢出"><a href="#堆内存溢出" class="headerlink" title="堆内存溢出"></a>堆内存溢出</h3><p>既然堆有垃圾回收机制，为什么还会发生内存溢出呢？最开始的时候，我也有这样的困惑。<br>后来我才认识到，还在使用中的对象是不能被强制回收的，不再使用的对象不是立刻回收的。当创建对象却没有足够的内存空间时，如果清理掉那些不再使用的对象就有足够的内存空间，就不会发生内存溢出，程序只是表现为卡顿。</p>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">class</span> <span class="title class_">HeapTest_1</span> &#123;  </span><br><span class="line">  </span><br><span class="line">    <span class="comment">// -Xmx8m  </span></span><br><span class="line">    <span class="comment">// 不设置可能不提示 Java heap space，出错地方不同，报错信息不同  </span></span><br><span class="line">    <span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">main</span><span class="params">(String[] args)</span> &#123;  </span><br><span class="line">        <span class="type">int</span> <span class="variable">i</span> <span class="operator">=</span> <span class="number">0</span>;  </span><br><span class="line">        <span class="keyword">try</span> &#123;  </span><br><span class="line">            List&lt;String&gt; list = <span class="keyword">new</span> <span class="title class_">ArrayList</span>&lt;&gt;();  </span><br><span class="line">            <span class="type">String</span> <span class="variable">s</span> <span class="operator">=</span> <span class="string">&quot;hello&quot;</span>;  </span><br><span class="line">            <span class="keyword">while</span> (<span class="literal">true</span>) &#123;  </span><br><span class="line">                list.add(s);  </span><br><span class="line">                s = s + s;  </span><br><span class="line">                i++;  </span><br><span class="line">            &#125;  </span><br><span class="line">        &#125; <span class="keyword">catch</span> (Throwable t) &#123;  </span><br><span class="line">            t.printStackTrace();  </span><br><span class="line">        &#125; <span class="keyword">finally</span> &#123;  </span><br><span class="line">            System.out.println(<span class="string">&quot;运行次数 &quot;</span> + i);  </span><br><span class="line">        &#125;  </span><br><span class="line">    &#125;  </span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
 
-<h3 id="registerBeanPostProcessors"><a href="#registerBeanPostProcessors" class="headerlink" title="registerBeanPostProcessors"></a>registerBeanPostProcessors</h3><p>注册拦截 <code>bean</code> 创建的 <code>bean</code> 后处理器。具体的处理被委托给 PostProcessorRegistrationDelegate。</p>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">protected</span> <span class="keyword">void</span> <span class="title function_">registerBeanPostProcessors</span><span class="params">(ConfigurableListableBeanFactory beanFactory)</span> &#123;</span><br><span class="line">    PostProcessorRegistrationDelegate.registerBeanPostProcessors(beanFactory, <span class="built_in">this</span>);</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+<figure class="highlight console"><table><tr><td class="code"><pre><span class="line">java.lang.OutOfMemoryError: Java heap space</span><br><span class="line">	at java.util.Arrays.copyOf(Arrays.java:3332)</span><br><span class="line">	at java.lang.AbstractStringBuilder.ensureCapacityInternal(AbstractStringBuilder.java:124)</span><br><span class="line">	at java.lang.AbstractStringBuilder.append(AbstractStringBuilder.java:448)</span><br><span class="line">	at java.lang.StringBuilder.append(StringBuilder.java:141)</span><br><span class="line">	at com.moralok.jvm.memory.heap.HeapTest_1.main(HeapTest_1.java:21)</span><br><span class="line">运行次数 17</span><br></pre></td></tr></table></figure>
 
-<p>registerBeanPostProcessors 相比之下是一条清新的裹脚布。这里特别区分 3 种类型的 Bean 后处理器：</p>
+<p>堆内存溢出的发生往往需要长时间的运行，因此在排查相关问题时，可以适当调小堆内存。</p>
+<h3 id="监测堆内存"><a href="#监测堆内存" class="headerlink" title="监测堆内存"></a>监测堆内存</h3><ol>
+<li>使用 jps 查看 Java 进程列表</li>
+<li>使用 <code>jmap -heap pid</code> 查看堆内存信息</li>
+<li>还可以使用 jconsole 观察堆内存变化曲线</li>
+<li>还可以使用 VisualVM 查看堆信息</li>
+</ol>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">class</span> <span class="title class_">HeapTest_2</span> &#123;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">main</span><span class="params">(String[] args)</span> <span class="keyword">throws</span> InterruptedException &#123;</span><br><span class="line">        System.out.println(<span class="string">&quot;1...&quot;</span>);</span><br><span class="line">        TimeUnit.SECONDS.sleep(<span class="number">30</span>);</span><br><span class="line">        <span class="comment">// 堆空间占用上升 10MB</span></span><br><span class="line">        <span class="type">byte</span>[] bytes = <span class="keyword">new</span> <span class="title class_">byte</span>[<span class="number">1024</span> * <span class="number">1024</span> * <span class="number">10</span>];</span><br><span class="line">        System.out.println(<span class="string">&quot;2...&quot;</span>);</span><br><span class="line">        TimeUnit.SECONDS.sleep(<span class="number">30</span>);</span><br><span class="line">        bytes = <span class="literal">null</span>;</span><br><span class="line">        <span class="comment">// 堆空间占用下降</span></span><br><span class="line">        System.gc();</span><br><span class="line">        System.out.println(<span class="string">&quot;3...&quot;</span>);</span><br><span class="line">        TimeUnit.SECONDS.sleep(<span class="number">3000</span>);</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<p>使用 <code>jmap -heap pid</code> 查看堆内存信息：</p>
+<figure class="highlight console"><table><tr><td class="code"><pre><span class="line">Eden Space:</span><br><span class="line">   capacity = 268435456 (256.0MB)</span><br><span class="line">   used     = 32212360 (30.72010040283203MB)</span><br><span class="line"></span><br><span class="line">   used     = 42698136 (40.720115661621094MB)</span><br><span class="line"></span><br><span class="line">   used     = 5368728 (5.120018005371094MB)</span><br></pre></td></tr></table></figure>
+
+<p>使用 jconsole 查看堆内存信息：</p>
+<img src="/2023/11/04/testing-and-analysis-of-jvm-memory-area/Pasted%20image%2020231104200411.png" class="" title="jconsole 观察堆内存占用">
+
+<h3 id="堆内存占用居高不下"><a href="#堆内存占用居高不下" class="headerlink" title="堆内存占用居高不下"></a>堆内存占用居高不下</h3><p>当你发现堆内存占用居高不下，经过 GC，下降也不明显，如果你想查看一下堆内的具体情况，可以将其 dump 查看。</p>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">class</span> <span class="title class_">HeapTest_3</span> &#123;  </span><br><span class="line">  </span><br><span class="line">    <span class="comment">// jps 查进程，jmap 看堆内存，jconsole 执行GC，堆内存占用没有明显下降  </span></span><br><span class="line">    <span class="comment">// 使用 VisualVM 的堆 dump 功能，观察大对象  </span></span><br><span class="line">    <span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">main</span><span class="params">(String[] args)</span> <span class="keyword">throws</span> IOException &#123;  </span><br><span class="line">        List&lt;Student&gt; students = <span class="keyword">new</span> <span class="title class_">ArrayList</span>&lt;&gt;();  </span><br><span class="line">        <span class="keyword">for</span> (<span class="type">int</span> <span class="variable">i</span> <span class="operator">=</span> <span class="number">0</span>; i &lt; <span class="number">200</span>; i++) &#123;  </span><br><span class="line">            students.add(<span class="keyword">new</span> <span class="title class_">Student</span>());  </span><br><span class="line">        &#125;  </span><br><span class="line">        System.in.read();  </span><br><span class="line">    &#125;  </span><br><span class="line">  </span><br><span class="line">    <span class="keyword">static</span> <span class="keyword">class</span> <span class="title class_">Student</span> &#123;  </span><br><span class="line">        <span class="keyword">private</span> <span class="type">byte</span>[] score = <span class="keyword">new</span> <span class="title class_">byte</span>[<span class="number">1024</span> * <span class="number">1024</span>];  </span><br><span class="line">    &#125;  </span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+<p>可使用 VisualVM 的 Heap Dump 功能：</p>
+<img src="/2023/11/04/testing-and-analysis-of-jvm-memory-area/Pasted%20image%2020231104201139.png" class="" title="VisualVM 观察堆中的大对象">
+
+<p>也可使用 <code>jmap -dump:format=b,file=filename.hprof pid</code>，需要其他分析工具搭配。</p>
+<h2 id="方法区"><a href="#方法区" class="headerlink" title="方法区"></a>方法区</h2><p>根据《Java虚拟机规范》，方法区在逻辑上是堆的一部分，但是在具体实现上，各个虚拟机厂商并不相同。对于 Hotspot 而言：</p>
 <ul>
-<li>MergedBeanDefinitionPostProcessor</li>
-<li>InstantiationAwareBeanPostProcessor 感知实例化</li>
-<li>DestructionAwareBeanPostProcessor 感知销毁</li>
+<li>JDK 8 之前，方法区的具体实现为永久代，使用堆内存，使用 -XX:MaxPermSize&#x3D;10m 设置大小。</li>
+<li>JDK 8 开始，方法区的具体实现为元空间，使用直接内存，使用 -XX:MaxMetaspaceSize&#x3D;10m 设置大小。</li>
 </ul>
-<p>ApplicationListenerDetector 既是 MergedBeanDefinitionPostProcessor，又是 DestructionAwareBeanPostProcessor，在初始化后将 listener 加入，在销毁前将 listener 移除。</p>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">registerBeanPostProcessors</span><span class="params">(</span></span><br><span class="line"><span class="params">		ConfigurableListableBeanFactory beanFactory, AbstractApplicationContext applicationContext)</span> &#123;</span><br><span class="line">    <span class="comment">// 获取 BeanPostProcessor 的名称</span></span><br><span class="line">    String[] postProcessorNames = beanFactory.getBeanNamesForType(BeanPostProcessor.class, <span class="literal">true</span>, <span class="literal">false</span>);</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 注册 BeanPostProcessorChecker，在 BeanPostProcessor 实例化期间创建 bean 时，记录一条消息。</span></span><br><span class="line">    <span class="comment">// 即，当一个 bean 不能被所有 BeanPostProcessors 处理时，记录。</span></span><br><span class="line">    <span class="type">int</span> <span class="variable">beanProcessorTargetCount</span> <span class="operator">=</span> beanFactory.getBeanPostProcessorCount() + <span class="number">1</span> + postProcessorNames.length;</span><br><span class="line">    beanFactory.addBeanPostProcessor(<span class="keyword">new</span> <span class="title class_">BeanPostProcessorChecker</span>(beanFactory, beanProcessorTargetCount));</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 将 BeanPostProcessors 按 implement PriorityOrdered，Ordered，和剩余的进行分类。</span></span><br><span class="line">    List&lt;BeanPostProcessor&gt; priorityOrderedPostProcessors = <span class="keyword">new</span> <span class="title class_">ArrayList</span>&lt;BeanPostProcessor&gt;();</span><br><span class="line">    List&lt;BeanPostProcessor&gt; internalPostProcessors = <span class="keyword">new</span> <span class="title class_">ArrayList</span>&lt;BeanPostProcessor&gt;();</span><br><span class="line">    List&lt;String&gt; orderedPostProcessorNames = <span class="keyword">new</span> <span class="title class_">ArrayList</span>&lt;String&gt;();</span><br><span class="line">    List&lt;String&gt; nonOrderedPostProcessorNames = <span class="keyword">new</span> <span class="title class_">ArrayList</span>&lt;String&gt;();</span><br><span class="line">    <span class="keyword">for</span> (String ppName : postProcessorNames) &#123;</span><br><span class="line">        <span class="keyword">if</span> (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) &#123;</span><br><span class="line">            <span class="type">BeanPostProcessor</span> <span class="variable">pp</span> <span class="operator">=</span> beanFactory.getBean(ppName, BeanPostProcessor.class);</span><br><span class="line">            priorityOrderedPostProcessors.add(pp);</span><br><span class="line">            <span class="keyword">if</span> (pp <span class="keyword">instanceof</span> MergedBeanDefinitionPostProcessor) &#123;</span><br><span class="line">                internalPostProcessors.add(pp);</span><br><span class="line">            &#125;</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="keyword">else</span> <span class="keyword">if</span> (beanFactory.isTypeMatch(ppName, Ordered.class)) &#123;</span><br><span class="line">            orderedPostProcessorNames.add(ppName);</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="keyword">else</span> &#123;</span><br><span class="line">            nonOrderedPostProcessorNames.add(ppName);</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 第 1 轮，注册 BeanPostProcessors that implement PriorityOrdered.</span></span><br><span class="line">    sortPostProcessors(priorityOrderedPostProcessors, beanFactory);</span><br><span class="line">    registerBeanPostProcessors(beanFactory, priorityOrderedPostProcessors);</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 第 2 轮，注册 BeanPostProcessors that implement Ordered.</span></span><br><span class="line">    List&lt;BeanPostProcessor&gt; orderedPostProcessors = <span class="keyword">new</span> <span class="title class_">ArrayList</span>&lt;BeanPostProcessor&gt;();</span><br><span class="line">    <span class="keyword">for</span> (String ppName : orderedPostProcessorNames) &#123;</span><br><span class="line">        <span class="type">BeanPostProcessor</span> <span class="variable">pp</span> <span class="operator">=</span> beanFactory.getBean(ppName, BeanPostProcessor.class);</span><br><span class="line">        orderedPostProcessors.add(pp);</span><br><span class="line">        <span class="keyword">if</span> (pp <span class="keyword">instanceof</span> MergedBeanDefinitionPostProcessor) &#123;</span><br><span class="line">            internalPostProcessors.add(pp);</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line">    sortPostProcessors(orderedPostProcessors, beanFactory);</span><br><span class="line">    registerBeanPostProcessors(beanFactory, orderedPostProcessors);</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 第 3 轮，注册剩余的 regular BeanPostProcessors.</span></span><br><span class="line">    List&lt;BeanPostProcessor&gt; nonOrderedPostProcessors = <span class="keyword">new</span> <span class="title class_">ArrayList</span>&lt;BeanPostProcessor&gt;();</span><br><span class="line">    <span class="keyword">for</span> (String ppName : nonOrderedPostProcessorNames) &#123;</span><br><span class="line">        <span class="type">BeanPostProcessor</span> <span class="variable">pp</span> <span class="operator">=</span> beanFactory.getBean(ppName, BeanPostProcessor.class);</span><br><span class="line">        nonOrderedPostProcessors.add(pp);</span><br><span class="line">        <span class="keyword">if</span> (pp <span class="keyword">instanceof</span> MergedBeanDefinitionPostProcessor) &#123;</span><br><span class="line">            internalPostProcessors.add(pp);</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line">    registerBeanPostProcessors(beanFactory, nonOrderedPostProcessors);</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 最后（第 4 轮）, 排序并注册 internal BeanPostProcessors.</span></span><br><span class="line">    sortPostProcessors(internalPostProcessors, beanFactory);</span><br><span class="line">    registerBeanPostProcessors(beanFactory, internalPostProcessors);</span><br><span class="line"></span><br><span class="line">    <span class="comment">// Re-register post-processor for detecting inner beans as ApplicationListeners,</span></span><br><span class="line">    <span class="comment">// moving it to the end of the processor chain (for picking up proxies etc).</span></span><br><span class="line">    <span class="comment">// 重新注册用于检测 ApplicationListeners 的 Bean 后处理器，将其移动到处理器链的最后（用于获取代理）。</span></span><br><span class="line">    beanFactory.addBeanPostProcessor(<span class="keyword">new</span> <span class="title class_">ApplicationListenerDetector</span>(applicationContext));</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+<h3 id="方法区溢出"><a href="#方法区溢出" class="headerlink" title="方法区溢出"></a>方法区溢出</h3><figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">class</span> <span class="title class_">MethodAreaTest_1</span> <span class="keyword">extends</span> <span class="title class_">ClassLoader</span> &#123;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// -XX:MaxMetaspaceSize=8m MaxMetaspaceSize is too small.</span></span><br><span class="line">    <span class="comment">// -XX:MaxMetaspaceSize=10m java.lang.OutOfMemoryError: Compressed class space</span></span><br><span class="line">    <span class="comment">// 不是 Metaspace 应该是某个参数设置的问题</span></span><br><span class="line">    <span class="comment">// JDK 6: -XX:MaxPermSize=8m PermGen space</span></span><br><span class="line">    <span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">main</span><span class="params">(String[] args)</span> &#123;</span><br><span class="line">        <span class="type">int</span> <span class="variable">j</span> <span class="operator">=</span> <span class="number">0</span>;</span><br><span class="line">        <span class="keyword">try</span> &#123;</span><br><span class="line">            <span class="type">MethodAreaTest_1</span> <span class="variable">methodAreaTest1</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">MethodAreaTest_1</span>();</span><br><span class="line">            <span class="keyword">for</span> (<span class="type">int</span> <span class="variable">i</span> <span class="operator">=</span> <span class="number">0</span>; i &lt; <span class="number">20000</span>; i++, j++) &#123;</span><br><span class="line">                <span class="type">ClassWriter</span> <span class="variable">classWriter</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">ClassWriter</span>(<span class="number">0</span>);</span><br><span class="line">                <span class="comment">// 版本号，public，类名，包名，父类，接口</span></span><br><span class="line">                classWriter.visit(Opcodes.V1_8, Opcodes.ACC_PUBLIC, <span class="string">&quot;Class&quot;</span> + i, <span class="literal">null</span>, <span class="string">&quot;java/lang/Object&quot;</span>, <span class="literal">null</span>);</span><br><span class="line">                <span class="comment">// 返回二进制字节码</span></span><br><span class="line">                <span class="type">byte</span>[] code = classWriter.toByteArray();</span><br><span class="line">                <span class="comment">// 加载类</span></span><br><span class="line">                methodAreaTest1.defineClass(<span class="string">&quot;Class&quot;</span> + i, code, <span class="number">0</span>, code.length);</span><br><span class="line">            &#125;</span><br><span class="line">        &#125; <span class="keyword">catch</span> (ClassFormatError e) &#123;</span><br><span class="line">            e.printStackTrace();</span><br><span class="line">        &#125; <span class="keyword">finally</span> &#123;</span><br><span class="line">            System.out.println(<span class="string">&quot;次数 &quot;</span> + j);</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+<ol>
+<li>当设置的值太小时 -XX:MaxMetaspaceSize&#x3D;8m，提示 MaxMetaspaceSize is too small。</li>
+<li>实验中抛出 java.lang.OutOfMemoryError: Compressed class space。</li>
+<li>添加参数 -XX:-UseCompressedClassPointers 后，抛出 java.lang.OutOfMemoryError: Metaspace。</li>
+<li>JDK 6 设置 -XX:MaxPermSize&#x3D;8m，抛出 java.lang.OutOfMemoryError: PermGen space。</li>
+</ol>
+<p>不要认为自己不会写动态生成字节码相关的代码就忽略这方面的问题，如今很多框架使用字节码技术大量地动态生成类。</p>
+<h2 id="运行时常量池"><a href="#运行时常量池" class="headerlink" title="运行时常量池"></a>运行时常量池</h2><p>二进制字节码文件主要包含三类信息：</p>
+<ol>
+<li>类的基本信息</li>
+<li>类的常量池（Constant Pool）</li>
+<li>类的方法信息</li>
+</ol>
+<h3 id="使用-javap-反编译"><a href="#使用-javap-反编译" class="headerlink" title="使用 javap 反编译"></a>使用 javap 反编译</h3><figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">class</span> <span class="title class_">MethodAreaTest_2</span> &#123;  </span><br><span class="line">  </span><br><span class="line">    <span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">main</span><span class="params">(String[] args)</span> &#123;  </span><br><span class="line">        System.out.println(<span class="string">&quot;hello world&quot;</span>);  </span><br><span class="line">    &#125;  </span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<figure class="highlight console"><table><tr><td class="code"><pre><span class="line">Classfile /C:/Users/username/Documents/github/jvm-study/target/classes/com/moralok/jvm/memory/methodarea/MethodAreaTest_2.class</span><br><span class="line">  Last modified 2023-11-4; size 619 bytes</span><br><span class="line">  MD5 checksum 0ed10a8f0a03be54fd4159958ee7446c</span><br><span class="line">  Compiled from &quot;MethodAreaTest_2.java&quot;</span><br><span class="line">public class com.moralok.jvm.memory.methodarea.MethodAreaTest_2</span><br><span class="line">  minor version: 0</span><br><span class="line">  major version: 52</span><br><span class="line">  flags: ACC_PUBLIC, ACC_SUPER</span><br><span class="line">Constant pool:</span><br><span class="line"><span class="meta prompt_">   #</span><span class="language-bash">1 = Methodref          <span class="comment">#6.#20         // java/lang/Object.&quot;&lt;init&gt;&quot;:()V</span></span></span><br><span class="line"><span class="meta prompt_">   #</span><span class="language-bash">2 = Fieldref           <span class="comment">#21.#22        // java/lang/System.out:Ljava/io/PrintStream;</span></span></span><br><span class="line"><span class="meta prompt_">   #</span><span class="language-bash">3 = String             <span class="comment">#23            // hello world</span></span></span><br><span class="line"><span class="meta prompt_">   #</span><span class="language-bash">4 = Methodref          <span class="comment">#24.#25        // java/io/PrintStream.println:(Ljava/lang/String;)V</span></span></span><br><span class="line"><span class="meta prompt_">   #</span><span class="language-bash">5 = Class              <span class="comment">#26            // com/moralok/jvm/memory/methodarea/MethodAreaTest_2</span></span></span><br><span class="line"><span class="meta prompt_">   #</span><span class="language-bash">6 = Class              <span class="comment">#27            // java/lang/Object</span></span></span><br><span class="line"><span class="meta prompt_">   #</span><span class="language-bash">7 = Utf8               &lt;init&gt;</span></span><br><span class="line"><span class="meta prompt_">   #</span><span class="language-bash">8 = Utf8               ()V</span></span><br><span class="line"><span class="meta prompt_">   #</span><span class="language-bash">9 = Utf8               Code</span></span><br><span class="line"><span class="meta prompt_">  #</span><span class="language-bash">10 = Utf8               LineNumberTable</span></span><br><span class="line"><span class="meta prompt_">  #</span><span class="language-bash">11 = Utf8               LocalVariableTable</span></span><br><span class="line"><span class="meta prompt_">  #</span><span class="language-bash">12 = Utf8               this</span></span><br><span class="line"><span class="meta prompt_">  #</span><span class="language-bash">13 = Utf8               Lcom/moralok/jvm/memory/methodarea/MethodAreaTest_2;</span></span><br><span class="line"><span class="meta prompt_">  #</span><span class="language-bash">14 = Utf8               main</span></span><br><span class="line"><span class="meta prompt_">  #</span><span class="language-bash">15 = Utf8               ([Ljava/lang/String;)V</span></span><br><span class="line"><span class="meta prompt_">  #</span><span class="language-bash">16 = Utf8               args</span></span><br><span class="line"><span class="meta prompt_">  #</span><span class="language-bash">17 = Utf8               [Ljava/lang/String;</span></span><br><span class="line"><span class="meta prompt_">  #</span><span class="language-bash">18 = Utf8               SourceFile</span></span><br><span class="line"><span class="meta prompt_">  #</span><span class="language-bash">19 = Utf8               MethodAreaTest_2.java</span></span><br><span class="line"><span class="meta prompt_">  #</span><span class="language-bash">20 = NameAndType        <span class="comment">#7:#8          // &quot;&lt;init&gt;&quot;:()V</span></span></span><br><span class="line"><span class="meta prompt_">  #</span><span class="language-bash">21 = Class              <span class="comment">#28            // java/lang/System</span></span></span><br><span class="line"><span class="meta prompt_">  #</span><span class="language-bash">22 = NameAndType        <span class="comment">#29:#30        // out:Ljava/io/PrintStream;</span></span></span><br><span class="line"><span class="meta prompt_">  #</span><span class="language-bash">23 = Utf8               hello world</span></span><br><span class="line"><span class="meta prompt_">  #</span><span class="language-bash">24 = Class              <span class="comment">#31            // java/io/PrintStream</span></span></span><br><span class="line"><span class="meta prompt_">  #</span><span class="language-bash">25 = NameAndType        <span class="comment">#32:#33        // println:(Ljava/lang/String;)V</span></span></span><br><span class="line"><span class="meta prompt_">  #</span><span class="language-bash">26 = Utf8               com/moralok/jvm/memory/methodarea/MethodAreaTest_2</span></span><br><span class="line"><span class="meta prompt_">  #</span><span class="language-bash">27 = Utf8               java/lang/Object</span></span><br><span class="line"><span class="meta prompt_">  #</span><span class="language-bash">28 = Utf8               java/lang/System</span></span><br><span class="line"><span class="meta prompt_">  #</span><span class="language-bash">29 = Utf8               out</span></span><br><span class="line"><span class="meta prompt_">  #</span><span class="language-bash">30 = Utf8               Ljava/io/PrintStream;</span></span><br><span class="line"><span class="meta prompt_">  #</span><span class="language-bash">31 = Utf8               java/io/PrintStream</span></span><br><span class="line"><span class="meta prompt_">  #</span><span class="language-bash">32 = Utf8               println</span></span><br><span class="line"><span class="meta prompt_">  #</span><span class="language-bash">33 = Utf8               (Ljava/lang/String;)V</span></span><br><span class="line">&#123;</span><br><span class="line">  public com.moralok.jvm.memory.methodarea.MethodAreaTest_2();</span><br><span class="line">    descriptor: ()V</span><br><span class="line">    flags: ACC_PUBLIC</span><br><span class="line">    Code:</span><br><span class="line">      stack=1, locals=1, args_size=1</span><br><span class="line">         0: aload_0</span><br><span class="line">         1: invokespecial #1                  // Method java/lang/Object.&quot;&lt;init&gt;&quot;:()V</span><br><span class="line">         4: return</span><br><span class="line">      LineNumberTable:</span><br><span class="line">        line 3: 0</span><br><span class="line">      LocalVariableTable:</span><br><span class="line">        Start  Length  Slot  Name   Signature</span><br><span class="line">            0       5     0  this   Lcom/moralok/jvm/memory/methodarea/MethodAreaTest_2;</span><br><span class="line"></span><br><span class="line">  public static void main(java.lang.String[]);</span><br><span class="line">    descriptor: ([Ljava/lang/String;)V</span><br><span class="line">    flags: ACC_PUBLIC, ACC_STATIC</span><br><span class="line">    Code:</span><br><span class="line">      stack=2, locals=1, args_size=1</span><br><span class="line">         0: getstatic     #2                  // Field java/lang/System.out:Ljava/io/PrintStream;</span><br><span class="line">         3: ldc           #3                  // String hello world</span><br><span class="line">         5: invokevirtual #4                  // Method java/io/PrintStream.println:(Ljava/lang/String;)V</span><br><span class="line">         8: return</span><br><span class="line">      LineNumberTable:</span><br><span class="line">        line 6: 0</span><br><span class="line">        line 7: 8</span><br><span class="line">      LocalVariableTable:</span><br><span class="line">        Start  Length  Slot  Name   Signature</span><br><span class="line">            0       9     0  args   [Ljava/lang/String;</span><br><span class="line">&#125;</span><br><span class="line">SourceFile: &quot;MethodAreaTest_2.java&quot;</span><br></pre></td></tr></table></figure>
 
-<p>添加 BeanPostProcessor 时</p>
 <ol>
-<li>先移除</li>
-<li>再添加</li>
-<li>判断类型并记录标记<ul>
-<li>感知实例化的后处理器</li>
-<li>感知销毁的后处理器</li>
-</ul>
-</li>
+<li>Class 文件的常量池就是一张表，虚拟机根据索引去查找类名、字段名及其类型，方法名及其参数类型和字面量等。</li>
+<li>当类被加载到虚拟机之后，Class 文件中的常量池中的信息就进入到了运行时常量池。</li>
+<li>这个过程其实就是信息从文件进入了内存。</li>
 </ol>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title function_">addBeanPostProcessor</span><span class="params">(BeanPostProcessor beanPostProcessor)</span> &#123;</span><br><span class="line">    Assert.notNull(beanPostProcessor, <span class="string">&quot;BeanPostProcessor must not be null&quot;</span>);</span><br><span class="line">    <span class="built_in">this</span>.beanPostProcessors.remove(beanPostProcessor);</span><br><span class="line">    <span class="built_in">this</span>.beanPostProcessors.add(beanPostProcessor);</span><br><span class="line">    <span class="keyword">if</span> (beanPostProcessor <span class="keyword">instanceof</span> InstantiationAwareBeanPostProcessor) &#123;</span><br><span class="line">        <span class="built_in">this</span>.hasInstantiationAwareBeanPostProcessors = <span class="literal">true</span>;</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="keyword">if</span> (beanPostProcessor <span class="keyword">instanceof</span> DestructionAwareBeanPostProcessor) &#123;</span><br><span class="line">        <span class="built_in">this</span>.hasDestructionAwareBeanPostProcessors = <span class="literal">true</span>;</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+<p>虚拟机解释器（interpreter）需要解释的字节码指令如下：</p>
+<figure class="highlight console"><table><tr><td class="code"><pre><span class="line">0: getstatic     #2</span><br><span class="line">3: ldc           #3</span><br><span class="line">5: invokevirtual #4</span><br></pre></td></tr></table></figure>
+<p>索引 <code>#2</code> 的意思就是去常量表里查找对应项代表的事物。</p>
+<h2 id="直接内存"><a href="#直接内存" class="headerlink" title="直接内存"></a>直接内存</h2><ul>
+<li>常见于 NIO 操作中的数据缓冲区。</li>
+<li>分配和回收的成本较高，但读写性能更高。</li>
+<li>不由 JVM 进行内存释放</li>
+</ul>
+<h3 id="NIO-和-IO-的拷贝性能"><a href="#NIO-和-IO-的拷贝性能" class="headerlink" title="NIO 和 IO 的拷贝性能"></a>NIO 和 IO 的拷贝性能</h3><figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">class</span> <span class="title class_">DirectMemoryTest_1</span> &#123;  </span><br><span class="line">  </span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">static</span> <span class="keyword">final</span> <span class="type">String</span> <span class="variable">FROM</span> <span class="operator">=</span> <span class="string">&quot;C:\\Users\\username\\Videos\\jellyfin\\media\\movies\\Harry Potter and the Chamber of Secrets (2002) [1080p]\\Harry.Potter.and.the.Chamber.of.Secrets.2002.1080p.BrRip.x264.YIFY.mp4&quot;</span>;  </span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">static</span> <span class="keyword">final</span> <span class="type">String</span> <span class="variable">TO</span> <span class="operator">=</span> <span class="string">&quot;C:\\Users\\username\\Videos\\jellyfin\\media\\movies\\Harry Potter and the Chamber of Secrets (2002) [1080p]\\Harry.Potter.and.the.Chamber.of.Secrets.2002.1080p.BrRip.x264.YIFY-copy.mp4&quot;</span>;  </span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">static</span> <span class="keyword">final</span> <span class="type">int</span> <span class="variable">_1Mb</span> <span class="operator">=</span> <span class="number">1024</span> * <span class="number">1024</span>;  </span><br><span class="line">  </span><br><span class="line">    <span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">main</span><span class="params">(String[] args)</span> &#123;  </span><br><span class="line">        io();  </span><br><span class="line">        directBuffer();  </span><br><span class="line">    &#125;  </span><br><span class="line">  </span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">directBuffer</span><span class="params">()</span> &#123;  </span><br><span class="line">        <span class="type">long</span> <span class="variable">start</span> <span class="operator">=</span> System.nanoTime();  </span><br><span class="line">        <span class="keyword">try</span> (<span class="type">FileChannel</span> <span class="variable">from</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">FileInputStream</span>(FROM).getChannel();  </span><br><span class="line">             <span class="type">FileChannel</span> <span class="variable">to</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">FileOutputStream</span>(TO).getChannel()) &#123;  </span><br><span class="line">            <span class="type">ByteBuffer</span> <span class="variable">buffer</span> <span class="operator">=</span> ByteBuffer.allocateDirect(_1Mb);  </span><br><span class="line">            <span class="keyword">while</span> (<span class="literal">true</span>) &#123;  </span><br><span class="line">                <span class="type">int</span> <span class="variable">len</span> <span class="operator">=</span> from.read(buffer);  </span><br><span class="line">                <span class="keyword">if</span> (len == -<span class="number">1</span>) &#123;  </span><br><span class="line">                    <span class="keyword">break</span>;  </span><br><span class="line">                &#125;  </span><br><span class="line">                buffer.flip();  </span><br><span class="line">                to.write(buffer);  </span><br><span class="line">                buffer.clear();  </span><br><span class="line">            &#125;  </span><br><span class="line">        &#125; <span class="keyword">catch</span> (IOException e) &#123;  </span><br><span class="line">            e.printStackTrace();  </span><br><span class="line">        &#125;  </span><br><span class="line">        <span class="type">long</span> <span class="variable">end</span> <span class="operator">=</span> System.nanoTime();  </span><br><span class="line">        System.out.println(<span class="string">&quot;directBuffer 用时 &quot;</span> + (end - start) / <span class="number">1000_000.0</span>);  </span><br><span class="line">    &#125;  </span><br><span class="line">  </span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">io</span><span class="params">()</span> &#123;  </span><br><span class="line">        <span class="type">long</span> <span class="variable">start</span> <span class="operator">=</span> System.nanoTime();  </span><br><span class="line">        <span class="keyword">try</span> (<span class="type">FileInputStream</span> <span class="variable">from</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">FileInputStream</span>(FROM);  </span><br><span class="line">             <span class="type">FileOutputStream</span> <span class="variable">to</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">FileOutputStream</span>(TO)) &#123;  </span><br><span class="line">            <span class="type">byte</span>[] buffer = <span class="keyword">new</span> <span class="title class_">byte</span>[_1Mb];  </span><br><span class="line">            <span class="keyword">while</span> (<span class="literal">true</span>) &#123;  </span><br><span class="line">                <span class="type">int</span> <span class="variable">len</span> <span class="operator">=</span> from.read(buffer);  </span><br><span class="line">                <span class="keyword">if</span> (len == -<span class="number">1</span>) &#123;  </span><br><span class="line">                    <span class="keyword">break</span>;  </span><br><span class="line">                &#125;  </span><br><span class="line">                to.write(buffer);  </span><br><span class="line">            &#125;  </span><br><span class="line">        &#125; <span class="keyword">catch</span> (IOException e) &#123;  </span><br><span class="line">            e.printStackTrace();  </span><br><span class="line">        &#125;  </span><br><span class="line">        <span class="type">long</span> <span class="variable">end</span> <span class="operator">=</span> System.nanoTime();  </span><br><span class="line">        System.out.println(<span class="string">&quot;io 用时 &quot;</span> + (end - start) / <span class="number">1000_000.0</span>);  </span><br><span class="line">    &#125;  </span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
 
-<h3 id="initMessageSource"><a href="#initMessageSource" class="headerlink" title="initMessageSource"></a>initMessageSource</h3><p>初始化消息源。 如果在此 context 中未定义，则使用父级的。</p>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">protected</span> <span class="keyword">void</span> <span class="title function_">initMessageSource</span><span class="params">()</span> &#123;</span><br><span class="line">    <span class="type">ConfigurableListableBeanFactory</span> <span class="variable">beanFactory</span> <span class="operator">=</span> getBeanFactory();</span><br><span class="line">    <span class="keyword">if</span> (beanFactory.containsLocalBean(MESSAGE_SOURCE_BEAN_NAME)) &#123;</span><br><span class="line">        <span class="built_in">this</span>.messageSource = beanFactory.getBean(MESSAGE_SOURCE_BEAN_NAME, MessageSource.class);</span><br><span class="line">        <span class="comment">// 设置 parent MessageSource.</span></span><br><span class="line">        <span class="keyword">if</span> (<span class="built_in">this</span>.parent != <span class="literal">null</span> &amp;&amp; <span class="built_in">this</span>.messageSource <span class="keyword">instanceof</span> HierarchicalMessageSource) &#123;</span><br><span class="line">            <span class="type">HierarchicalMessageSource</span> <span class="variable">hms</span> <span class="operator">=</span> (HierarchicalMessageSource) <span class="built_in">this</span>.messageSource;</span><br><span class="line">            <span class="keyword">if</span> (hms.getParentMessageSource() == <span class="literal">null</span>) &#123;</span><br><span class="line">                <span class="comment">// 只有当 parent MessageSource 尚未注册才将 parent context 设置为 parent MessageSource</span></span><br><span class="line">                hms.setParentMessageSource(getInternalParentMessageSource());</span><br><span class="line">            &#125;</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="keyword">if</span> (logger.isDebugEnabled()) &#123;</span><br><span class="line">            logger.debug(<span class="string">&quot;Using MessageSource [&quot;</span> + <span class="built_in">this</span>.messageSource + <span class="string">&quot;]&quot;</span>);</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="keyword">else</span> &#123;</span><br><span class="line">        <span class="comment">// 使用代理 messageSource，以此接收 getMessage 调用。</span></span><br><span class="line">        <span class="type">DelegatingMessageSource</span> <span class="variable">dms</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">DelegatingMessageSource</span>();</span><br><span class="line">        dms.setParentMessageSource(getInternalParentMessageSource());</span><br><span class="line">        <span class="built_in">this</span>.messageSource = dms;</span><br><span class="line">        beanFactory.registerSingleton(MESSAGE_SOURCE_BEAN_NAME, <span class="built_in">this</span>.messageSource);</span><br><span class="line">        <span class="keyword">if</span> (logger.isDebugEnabled()) &#123;</span><br><span class="line">            logger.debug(<span class="string">&quot;Unable to locate MessageSource with name &#x27;&quot;</span> + MESSAGE_SOURCE_BEAN_NAME +</span><br><span class="line">                    <span class="string">&quot;&#x27;: using default [&quot;</span> + <span class="built_in">this</span>.messageSource + <span class="string">&quot;]&quot;</span>);</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+<figure class="highlight console"><table><tr><td class="code"><pre><span class="line">io 用时 1676.9797</span><br><span class="line">directBuffer 用时 836.4796</span><br></pre></td></tr></table></figure>
 
-<h3 id="initApplicationEventMulticaster"><a href="#initApplicationEventMulticaster" class="headerlink" title="initApplicationEventMulticaster"></a>initApplicationEventMulticaster</h3><p>初始化 <code>ApplicationEventMulticaster</code>。 如果上下文中未定义，则使用 <code>SimpleApplicationEventMulticaster</code>。可以看得出代码的结构和 initMessageSource 是类似的。</p>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">protected</span> <span class="keyword">void</span> <span class="title function_">initApplicationEventMulticaster</span><span class="params">()</span> &#123;</span><br><span class="line">    <span class="type">ConfigurableListableBeanFactory</span> <span class="variable">beanFactory</span> <span class="operator">=</span> getBeanFactory();</span><br><span class="line">    <span class="keyword">if</span> (beanFactory.containsLocalBean(APPLICATION_EVENT_MULTICASTER_BEAN_NAME)) &#123;</span><br><span class="line">        <span class="built_in">this</span>.applicationEventMulticaster =</span><br><span class="line">                beanFactory.getBean(APPLICATION_EVENT_MULTICASTER_BEAN_NAME, ApplicationEventMulticaster.class);</span><br><span class="line">        <span class="keyword">if</span> (logger.isDebugEnabled()) &#123;</span><br><span class="line">            logger.debug(<span class="string">&quot;Using ApplicationEventMulticaster [&quot;</span> + <span class="built_in">this</span>.applicationEventMulticaster + <span class="string">&quot;]&quot;</span>);</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="keyword">else</span> &#123;</span><br><span class="line">        <span class="built_in">this</span>.applicationEventMulticaster = <span class="keyword">new</span> <span class="title class_">SimpleApplicationEventMulticaster</span>(beanFactory);</span><br><span class="line">        beanFactory.registerSingleton(APPLICATION_EVENT_MULTICASTER_BEAN_NAME, <span class="built_in">this</span>.applicationEventMulticaster);</span><br><span class="line">        <span class="keyword">if</span> (logger.isDebugEnabled()) &#123;</span><br><span class="line">            logger.debug(<span class="string">&quot;Unable to locate ApplicationEventMulticaster with name &#x27;&quot;</span> +</span><br><span class="line">                    APPLICATION_EVENT_MULTICASTER_BEAN_NAME +</span><br><span class="line">                    <span class="string">&quot;&#x27;: using default [&quot;</span> + <span class="built_in">this</span>.applicationEventMulticaster + <span class="string">&quot;]&quot;</span>);</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+<img src="/2023/11/04/testing-and-analysis-of-jvm-memory-area/Pasted%20image%2020231104235546.png" class="" title="普通的 IO 拷贝">
 
-<h3 id="onRefresh"><a href="#onRefresh" class="headerlink" title="onRefresh"></a>onRefresh</h3><p>可以重写模板方法来添加特定 context 的刷新工作。默认情况下什么都不做。</p>
-<h3 id="registerListeners"><a href="#registerListeners" class="headerlink" title="registerListeners"></a>registerListeners</h3><p>获取侦听器 <code>bean</code> 并注册。无需初始化即可添加</p>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">protected</span> <span class="keyword">void</span> <span class="title function_">registerListeners</span><span class="params">()</span> &#123;</span><br><span class="line">    <span class="comment">// 注册静态指定的 ApplicationListener，和 beanFactoryPostProcessor 类似，context 可以提前添加好。</span></span><br><span class="line">    <span class="keyword">for</span> (ApplicationListener&lt;?&gt; listener : getApplicationListeners()) &#123;</span><br><span class="line">        getApplicationEventMulticaster().addApplicationListener(listener);</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// Do not initialize FactoryBeans here: We need to leave all regular beans</span></span><br><span class="line">    <span class="comment">// uninitialized to let post-processors apply to them!</span></span><br><span class="line">    <span class="comment">// 这段注释看到不止一次，但是不太理解，感觉和代码联系不起来？</span></span><br><span class="line">    String[] listenerBeanNames = getBeanNamesForType(ApplicationListener.class, <span class="literal">true</span>, <span class="literal">false</span>);</span><br><span class="line">    <span class="keyword">for</span> (String listenerBeanName : listenerBeanNames) &#123;</span><br><span class="line">        getApplicationEventMulticaster().addApplicationListenerBean(listenerBeanName);</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 现在我们终于有了多播器，发布早期的应用事件。</span></span><br><span class="line">    Set&lt;ApplicationEvent&gt; earlyEventsToProcess = <span class="built_in">this</span>.earlyApplicationEvents;</span><br><span class="line">    <span class="built_in">this</span>.earlyApplicationEvents = <span class="literal">null</span>;</span><br><span class="line">    <span class="keyword">if</span> (earlyEventsToProcess != <span class="literal">null</span>) &#123;</span><br><span class="line">        <span class="keyword">for</span> (ApplicationEvent earlyEvent : earlyEventsToProcess) &#123;</span><br><span class="line">            getApplicationEventMulticaster().multicastEvent(earlyEvent);</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+<img src="/2023/11/04/testing-and-analysis-of-jvm-memory-area/Pasted%20image%2020231104235846.png" class="" title="NIO 拷贝">
 
-<p>添加 ApplicationListener。</p>
-<blockquote>
-<p>后处理器 ApplicationListenerDetector 在 processor chain 的最后，最终会将创建的代理添加为监听器。什么情况下会出现代码中预防的情况呢？</p>
-</blockquote>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title function_">addApplicationListener</span><span class="params">(ApplicationListener&lt;?&gt; listener)</span> &#123;</span><br><span class="line">    <span class="keyword">synchronized</span> (<span class="built_in">this</span>.retrievalMutex) &#123;</span><br><span class="line">        <span class="comment">// 如果已经注册，需要显式地删除代理，以避免同一监听器的双重调用。</span></span><br><span class="line">        <span class="type">Object</span> <span class="variable">singletonTarget</span> <span class="operator">=</span> AopProxyUtils.getSingletonTarget(listener);</span><br><span class="line">        <span class="keyword">if</span> (singletonTarget <span class="keyword">instanceof</span> ApplicationListener) &#123;</span><br><span class="line">            <span class="built_in">this</span>.defaultRetriever.applicationListeners.remove(singletonTarget);</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="built_in">this</span>.defaultRetriever.applicationListeners.add(listener);</span><br><span class="line">        <span class="built_in">this</span>.retrieverCache.clear();</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
 
-<h3 id="finishBeanFactoryInitialization"><a href="#finishBeanFactoryInitialization" class="headerlink" title="finishBeanFactoryInitialization"></a>finishBeanFactoryInitialization</h3><p>实例化所有剩余的（非惰性初始化）单例。以 context 视角，是完成内部 beanFactory 的初始化。</p>
-<p>几乎可以只关注最后的 <code>beanFactory.preInstantiateSingletons()</code>。</p>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">protected</span> <span class="keyword">void</span> <span class="title function_">finishBeanFactoryInitialization</span><span class="params">(ConfigurableListableBeanFactory beanFactory)</span> &#123;</span><br><span class="line">    <span class="comment">// 为 context 初始化转换服务</span></span><br><span class="line">    <span class="keyword">if</span> (beanFactory.containsBean(CONVERSION_SERVICE_BEAN_NAME) &amp;&amp;</span><br><span class="line">            beanFactory.isTypeMatch(CONVERSION_SERVICE_BEAN_NAME, ConversionService.class)) &#123;</span><br><span class="line">        beanFactory.setConversionService(</span><br><span class="line">                beanFactory.getBean(CONVERSION_SERVICE_BEAN_NAME, ConversionService.class));</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 如果之前没有任何 bean 后处理器（例如 PropertyPlaceholderConfigurer）注册，则注册默认的嵌入值解析器，主要用于解析注释属性值。</span></span><br><span class="line">    <span class="comment">// 接口 ConfigurableEnvironment 继承自 ConfigurablePropertyResolver</span></span><br><span class="line">    <span class="keyword">if</span> (!beanFactory.hasEmbeddedValueResolver()) &#123;</span><br><span class="line">        beanFactory.addEmbeddedValueResolver(<span class="keyword">new</span> <span class="title class_">StringValueResolver</span>() &#123;</span><br><span class="line">            <span class="meta">@Override</span></span><br><span class="line">            <span class="keyword">public</span> String <span class="title function_">resolveStringValue</span><span class="params">(String strVal)</span> &#123;</span><br><span class="line">                <span class="keyword">return</span> getEnvironment().resolvePlaceholders(strVal);</span><br><span class="line">            &#125;</span><br><span class="line">        &#125;);</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 尽早初始化 LoadTimeWeaverAware，以便尽早注册其转换器。</span></span><br><span class="line">    String[] weaverAwareNames = beanFactory.getBeanNamesForType(LoadTimeWeaverAware.class, <span class="literal">false</span>, <span class="literal">false</span>);</span><br><span class="line">    <span class="keyword">for</span> (String weaverAwareName : weaverAwareNames) &#123;</span><br><span class="line">        getBean(weaverAwareName);</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 停止使用临时类加载器进行类型匹配。</span></span><br><span class="line">    beanFactory.setTempClassLoader(<span class="literal">null</span>);</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 允许缓存所有 bean 定义的元数据，而不期望进一步更改。</span></span><br><span class="line">    beanFactory.freezeConfiguration();</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 实例化所有剩余的（非惰性初始化）单例。</span></span><br><span class="line">    beanFactory.preInstantiateSingletons();</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+<h3 id="直接内存溢出"><a href="#直接内存溢出" class="headerlink" title="直接内存溢出"></a>直接内存溢出</h3><figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">class</span> <span class="title class_">DirectMemoryTest_2</span> &#123;  </span><br><span class="line">  </span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">static</span> <span class="keyword">final</span> <span class="type">int</span> <span class="variable">_100Mb</span> <span class="operator">=</span> <span class="number">1024</span> * <span class="number">1024</span> * <span class="number">100</span>;  </span><br><span class="line">  </span><br><span class="line">    <span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">main</span><span class="params">(String[] args)</span> &#123;  </span><br><span class="line">        List&lt;ByteBuffer&gt; list = <span class="keyword">new</span> <span class="title class_">ArrayList</span>&lt;&gt;();  </span><br><span class="line">        <span class="type">int</span> <span class="variable">i</span> <span class="operator">=</span> <span class="number">0</span>;  </span><br><span class="line">        <span class="keyword">try</span> &#123;  </span><br><span class="line">            <span class="keyword">while</span> (<span class="literal">true</span>) &#123;  </span><br><span class="line">                <span class="type">ByteBuffer</span> <span class="variable">byteBuffer</span> <span class="operator">=</span> ByteBuffer.allocateDirect(_100Mb);  </span><br><span class="line">                list.add(byteBuffer);  </span><br><span class="line">                i++;  </span><br><span class="line">            &#125;  </span><br><span class="line">        &#125; <span class="keyword">catch</span> (Throwable t) &#123;  </span><br><span class="line">            t.printStackTrace();  </span><br><span class="line">        &#125; System.out.println(i);  </span><br><span class="line">    &#125;  </span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
 
-<p>确保所有非惰性初始化单例都已实例化，同时还要考虑 <code>FactoryBeans</code>。 如果需要，通常在工厂设置结束时调用。</p>
-<a href="/2023/08/10/how-does-Spring-load-beans/" title="Spring Bean 加载过程">加载 Bean 的流程分析在此</a>。
+<figure class="highlight console"><table><tr><td class="code"><pre><span class="line">java.lang.OutOfMemoryError: Direct buffer memory</span><br><span class="line">	at java.nio.Bits.reserveMemory(Bits.java:695)</span><br><span class="line">	at java.nio.DirectByteBuffer.&lt;init&gt;(DirectByteBuffer.java:123)</span><br><span class="line">	at java.nio.ByteBuffer.allocateDirect(ByteBuffer.java:311)</span><br><span class="line">	at com.moralok.jvm.memory.direct.DirectMemoryTest_2.main(DirectMemoryTest_2.java:16)</span><br><span class="line">145</span><br></pre></td></tr></table></figure>
 
-<blockquote>
-<p>先对集合进行 Copy 再迭代是很常见的处理方式，可以有效保证迭代时不受原集合影响，也不会影响到原集合。</p>
-</blockquote>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="meta">@Override</span></span><br><span class="line"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title function_">preInstantiateSingletons</span><span class="params">()</span> <span class="keyword">throws</span> BeansException &#123;</span><br><span class="line">    <span class="keyword">if</span> (<span class="built_in">this</span>.logger.isDebugEnabled()) &#123;</span><br><span class="line">        <span class="built_in">this</span>.logger.debug(<span class="string">&quot;Pre-instantiating singletons in &quot;</span> + <span class="built_in">this</span>);</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 拷贝一份 beanDefinitionNames</span></span><br><span class="line">    List&lt;String&gt; beanNames = <span class="keyword">new</span> <span class="title class_">ArrayList</span>&lt;String&gt;(<span class="built_in">this</span>.beanDefinitionNames);</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 触发所有非惰性初始化单例的实例化</span></span><br><span class="line">    <span class="keyword">for</span> (String beanName : beanNames) &#123;</span><br><span class="line">        <span class="type">RootBeanDefinition</span> <span class="variable">bd</span> <span class="operator">=</span> getMergedLocalBeanDefinition(beanName);</span><br><span class="line">        <span class="keyword">if</span> (!bd.isAbstract() &amp;&amp; bd.isSingleton() &amp;&amp; !bd.isLazyInit()) &#123;</span><br><span class="line">            <span class="keyword">if</span> (isFactoryBean(beanName)) &#123;</span><br><span class="line">                <span class="comment">// FactoryBean</span></span><br><span class="line">                <span class="keyword">final</span> FactoryBean&lt;?&gt; factory = (FactoryBean&lt;?&gt;) getBean(FACTORY_BEAN_PREFIX + beanName);</span><br><span class="line">                <span class="type">boolean</span> isEagerInit;</span><br><span class="line">                <span class="keyword">if</span> (System.getSecurityManager() != <span class="literal">null</span> &amp;&amp; factory <span class="keyword">instanceof</span> SmartFactoryBean) &#123;</span><br><span class="line">                    isEagerInit = AccessController.doPrivileged(<span class="keyword">new</span> <span class="title class_">PrivilegedAction</span>&lt;Boolean&gt;() &#123;</span><br><span class="line">                        <span class="meta">@Override</span></span><br><span class="line">                        <span class="keyword">public</span> Boolean <span class="title function_">run</span><span class="params">()</span> &#123;</span><br><span class="line">                            <span class="keyword">return</span> ((SmartFactoryBean&lt;?&gt;) factory).isEagerInit();</span><br><span class="line">                        &#125;</span><br><span class="line">                    &#125;, getAccessControlContext());</span><br><span class="line">                &#125;</span><br><span class="line">                <span class="keyword">else</span> &#123;</span><br><span class="line">                    isEagerInit = (factory <span class="keyword">instanceof</span> SmartFactoryBean &amp;&amp;</span><br><span class="line">                            ((SmartFactoryBean&lt;?&gt;) factory).isEagerInit());</span><br><span class="line">                &#125;</span><br><span class="line">                <span class="keyword">if</span> (isEagerInit) &#123;</span><br><span class="line">                    <span class="comment">// 是否立即初始化</span></span><br><span class="line">                    getBean(beanName);</span><br><span class="line">                &#125;</span><br><span class="line">            &#125;</span><br><span class="line">            <span class="keyword">else</span> &#123;</span><br><span class="line">                <span class="comment">// 常规 Bean（重要）</span></span><br><span class="line">                getBean(beanName);</span><br><span class="line">            &#125;</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 触发所有适用 bean 的初始化后回调</span></span><br><span class="line">    <span class="keyword">for</span> (String beanName : beanNames) &#123;</span><br><span class="line">        <span class="type">Object</span> <span class="variable">singletonInstance</span> <span class="operator">=</span> getSingleton(beanName);</span><br><span class="line">        <span class="keyword">if</span> (singletonInstance <span class="keyword">instanceof</span> SmartInitializingSingleton) &#123;</span><br><span class="line">            <span class="keyword">final</span> <span class="type">SmartInitializingSingleton</span> <span class="variable">smartSingleton</span> <span class="operator">=</span> (SmartInitializingSingleton) singletonInstance;</span><br><span class="line">            <span class="keyword">if</span> (System.getSecurityManager() != <span class="literal">null</span>) &#123;</span><br><span class="line">                AccessController.doPrivileged(<span class="keyword">new</span> <span class="title class_">PrivilegedAction</span>&lt;Object&gt;() &#123;</span><br><span class="line">                    <span class="meta">@Override</span></span><br><span class="line">                    <span class="keyword">public</span> Object <span class="title function_">run</span><span class="params">()</span> &#123;</span><br><span class="line">                        smartSingleton.afterSingletonsInstantiated();</span><br><span class="line">                        <span class="keyword">return</span> <span class="literal">null</span>;</span><br><span class="line">                    &#125;</span><br><span class="line">                &#125;, getAccessControlContext());</span><br><span class="line">            &#125;</span><br><span class="line">            <span class="keyword">else</span> &#123;</span><br><span class="line">                smartSingleton.afterSingletonsInstantiated();</span><br><span class="line">            &#125;</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+<p>这似乎是代码中抛出的异常，而不是真正的直接内存溢出？</p>
+<h3 id="直接内存释放的原理"><a href="#直接内存释放的原理" class="headerlink" title="直接内存释放的原理"></a>直接内存释放的原理</h3><h4 id="演示直接内存的释放受-GC-影响"><a href="#演示直接内存的释放受-GC-影响" class="headerlink" title="演示直接内存的释放受 GC 影响"></a>演示直接内存的释放受 GC 影响</h4><figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">class</span> <span class="title class_">DirectMemoryTest_3</span> &#123;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">static</span> <span class="keyword">final</span> <span class="type">int</span> <span class="variable">_1GB</span> <span class="operator">=</span> <span class="number">1024</span> * <span class="number">1024</span> * <span class="number">1024</span>;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">main</span><span class="params">(String[] args)</span> <span class="keyword">throws</span> IOException &#123;</span><br><span class="line">        <span class="type">ByteBuffer</span> <span class="variable">byteBuffer</span> <span class="operator">=</span> ByteBuffer.allocateDirect(_1GB);</span><br><span class="line">        System.out.println(<span class="string">&quot;分配完毕&quot;</span>);</span><br><span class="line">        System.in.read();</span><br><span class="line">        System.out.println(<span class="string">&quot;开始释放&quot;</span>);</span><br><span class="line">        byteBuffer = <span class="literal">null</span>;</span><br><span class="line">        <span class="comment">// 随着 ByteBuffer 的释放，从任务管理器界面看到程序的内存的占用迅速下降 1GB。</span></span><br><span class="line">        System.gc();</span><br><span class="line">        System.in.read();</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
 
-<h3 id="finishRefresh"><a href="#finishRefresh" class="headerlink" title="finishRefresh"></a>finishRefresh</h3><p>最后一步，完成 context 刷新，比如发布相应的事件。</p>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">protected</span> <span class="keyword">void</span> <span class="title function_">finishRefresh</span><span class="params">()</span> &#123;</span><br><span class="line">    <span class="comment">// 1. 为此 context 初始化生命周期处理器。</span></span><br><span class="line">    initLifecycleProcessor();</span><br><span class="line">    <span class="comment">// 2. 将刷新传播到生命周期处理器。</span></span><br><span class="line">    getLifecycleProcessor().onRefresh();</span><br><span class="line">    <span class="comment">// 3. 发布 ContextRefreshedEvent。</span></span><br><span class="line">    publishEvent(<span class="keyword">new</span> <span class="title class_">ContextRefreshedEvent</span>(<span class="built_in">this</span>));</span><br><span class="line">    <span class="comment">// 4. 参与 LiveBeansView MBean（如果处于活动状态）。</span></span><br><span class="line">    LiveBeansView.registerApplicationContext(<span class="built_in">this</span>);</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>]]></content>
+<h4 id="手动进行直接内存的分配和释放"><a href="#手动进行直接内存的分配和释放" class="headerlink" title="手动进行直接内存的分配和释放"></a>手动进行直接内存的分配和释放</h4><p>在代码中实现手动进行直接内存的分配和释放。</p>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">class</span> <span class="title class_">DirectMemoryTest_4</span> &#123;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">static</span> <span class="keyword">final</span> <span class="type">int</span> <span class="variable">_1GB</span> <span class="operator">=</span> <span class="number">1024</span> * <span class="number">1024</span> * <span class="number">1024</span>;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">main</span><span class="params">(String[] args)</span> <span class="keyword">throws</span> IOException &#123;</span><br><span class="line">        <span class="type">Unsafe</span> <span class="variable">unsafe</span> <span class="operator">=</span> getUnsafe();</span><br><span class="line"></span><br><span class="line">        <span class="comment">// 分配内存</span></span><br><span class="line">        <span class="type">long</span> <span class="variable">base</span> <span class="operator">=</span> unsafe.allocateMemory(_1GB);</span><br><span class="line">        unsafe.setMemory(base, _1GB, (<span class="type">byte</span>) <span class="number">0</span>);</span><br><span class="line">        System.in.read();</span><br><span class="line"></span><br><span class="line">        <span class="comment">// 释放内存</span></span><br><span class="line">        unsafe.freeMemory(base);</span><br><span class="line">        System.in.read();</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">static</span> Unsafe <span class="title function_">getUnsafe</span><span class="params">()</span> &#123;</span><br><span class="line">        <span class="keyword">try</span> &#123;</span><br><span class="line">            <span class="type">Field</span> <span class="variable">f</span> <span class="operator">=</span> Unsafe.class.getDeclaredField(<span class="string">&quot;theUnsafe&quot;</span>);</span><br><span class="line">            f.setAccessible(<span class="literal">true</span>);</span><br><span class="line">            <span class="type">Unsafe</span> <span class="variable">unsafe</span> <span class="operator">=</span> (Unsafe) f.get(<span class="literal">null</span>);</span><br><span class="line">            <span class="keyword">return</span> unsafe;</span><br><span class="line">        &#125; <span class="keyword">catch</span> (NoSuchFieldException | IllegalAccessException e) &#123;</span><br><span class="line">            <span class="keyword">throw</span> <span class="keyword">new</span> <span class="title class_">RuntimeException</span>(e);</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<h4 id="如何将-GC-和直接内存的分配和释放关联"><a href="#如何将-GC-和直接内存的分配和释放关联" class="headerlink" title="如何将 GC 和直接内存的分配和释放关联"></a>如何将 GC 和直接内存的分配和释放关联</h4><p>本质上，直接内存的自动释放是利用了虚引用的机制，间接调用了 unsafe 的分配和释放直接内存的方法。</p>
+<p>DirectByteBuffer 就是使用 unsafe.allocateMemory(size) 分配直接内存。DirectByteBuffer 对象以及一个 Deallocator 对象（Runnable 类型）一起用于创建了一个虚引用类型的 Cleaner 对象。</p>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line">DirectByteBuffer(<span class="type">int</span> cap) &#123;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 省略</span></span><br><span class="line">    <span class="keyword">try</span> &#123;</span><br><span class="line">        base = unsafe.allocateMemory(size);</span><br><span class="line">    &#125; <span class="keyword">catch</span> (OutOfMemoryError x) &#123;</span><br><span class="line">        Bits.unreserveMemory(size, cap);</span><br><span class="line">        <span class="keyword">throw</span> x;</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="comment">// 省略</span></span><br><span class="line">    cleaner = Cleaner.create(<span class="built_in">this</span>, <span class="keyword">new</span> <span class="title class_">Deallocator</span>(base, size, cap));</span><br><span class="line">    att = <span class="literal">null</span>;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<p>根据虚引用的机制，如果 DirectByteBuffer 对象被回收，虚引用对象会被加入到 Cleanner 的引用队列，ReferenceHandler 线程会处理引用队列中的 Cleaner 对象，进而调用 Deallocator 对象的 run 方法。</p>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title function_">run</span><span class="params">()</span> &#123;</span><br><span class="line">    <span class="keyword">if</span> (address == <span class="number">0</span>) &#123;</span><br><span class="line">        <span class="comment">// Paranoia</span></span><br><span class="line">        <span class="keyword">return</span>;</span><br><span class="line">    &#125;</span><br><span class="line">    unsafe.freeMemory(address);</span><br><span class="line">    address = <span class="number">0</span>;</span><br><span class="line">    Bits.unreserveMemory(size, capacity);</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+]]></content>
       <tags>
         <tag>java</tag>
-        <tag>spring</tag>
+        <tag>jvm</tag>
       </tags>
   </entry>
   <entry>
@@ -2693,204 +2786,59 @@
       </tags>
   </entry>
   <entry>
-    <title>JVM 内存区域的测试和分析</title>
-    <url>/2023/11/04/testing-and-analysis-of-jvm-memory-area/</url>
-    <content><![CDATA[<h2 id="内存区域"><a href="#内存区域" class="headerlink" title="内存区域"></a>内存区域</h2><p>JVM 内存区域划分为：</p>
-<ul>
-<li>程序计数器</li>
-<li>虚拟机栈</li>
-<li>本地方法栈</li>
-<li>堆</li>
-<li>方法区</li>
-</ul>
-<img src="/2023/11/04/testing-and-analysis-of-jvm-memory-area/Pasted%20image%2020231102215652.png" class="" title="内存区域划分">
+    <title>基于 Redis 的分布式锁的简单实现</title>
+    <url>/2023/11/13/simple-implementation-of-distributed-lock-based-on-Redis/</url>
+    <content><![CDATA[<p>在分布式应用中，并发访问资源需要谨慎考虑。比如读取和修改保存并不是一个原子操作，在并发时，就可能发生修改的结果被覆盖的问题。</p>
+<img src="/2023/11/13/simple-implementation-of-distributed-lock-based-on-Redis/Pasted%20image%2020231110180458.png" class="" title="分布式应用中的并发问题">
 
-<h2 id="程序计数器"><a href="#程序计数器" class="headerlink" title="程序计数器"></a>程序计数器</h2><h2 id="虚拟机栈"><a href="#虚拟机栈" class="headerlink" title="虚拟机栈"></a>虚拟机栈</h2><p>Java 虚拟机栈（Java Virtual Machine Stack），线程私有，生命周期与线程相同。虚拟机栈描述的是 Java 方法执行的线程内存模型。每个方法被执行的时候，Java虚拟机都会同步创建一个栈帧（Stack Frame）用于存储局部变量表、操作数栈、动态连接、方法出口等信息。</p>
-<p>可以使用 <code>-Xss1024k</code> 设置虚拟机栈的大小。默认情况下都是 1024k，只有 Windows 中取决于虚拟内存。</p>
-<h3 id="栈内存溢出"><a href="#栈内存溢出" class="headerlink" title="栈内存溢出"></a>栈内存溢出</h3><ol>
-<li>栈帧过多导致栈内存溢出</li>
-<li>栈帧过大导致栈内存溢出（难复现）</li>
-</ol>
-<h4 id="不正确的递归调用"><a href="#不正确的递归调用" class="headerlink" title="不正确的递归调用"></a>不正确的递归调用</h4><figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">class</span> <span class="title class_">StackTest_4</span> &#123;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">static</span> <span class="type">int</span> <span class="variable">count</span> <span class="operator">=</span> <span class="number">0</span>;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 改变栈的大小限制 -Xss256k，观察调用次数的变化</span></span><br><span class="line">    <span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">main</span><span class="params">(String[] args)</span> &#123;</span><br><span class="line">        <span class="keyword">try</span> &#123;</span><br><span class="line">            method1();</span><br><span class="line">        &#125; <span class="keyword">catch</span> (Throwable t) &#123;</span><br><span class="line">            t.printStackTrace();</span><br><span class="line">        &#125; <span class="keyword">finally</span> &#123;</span><br><span class="line">            <span class="comment">// 默认情况下经过 20000+ 次，改变参数后 3000+ 次</span></span><br><span class="line">            System.out.println(count);</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">method1</span><span class="params">()</span> &#123;</span><br><span class="line">        count++;</span><br><span class="line">        method1();</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+<p>很多人都了解在必要的时候需要使用分布式锁来限制程序的并发执行，但是在具体的细节上，往往并不正确。</p>
+<h2 id="基于-Redis-的分布式锁简单实现"><a href="#基于-Redis-的分布式锁简单实现" class="headerlink" title="基于 Redis 的分布式锁简单实现"></a>基于 Redis 的分布式锁简单实现</h2><p>本质上要实现的目标就是在 Redis 中占坑，告诉后来者资源已经被锁定，放弃或者稍后重试。Redis 原生支持 set if not exists 的语义。</p>
+<figure class="highlight console"><table><tr><td class="code"><pre><span class="line"><span class="meta prompt_">&gt; </span><span class="language-bash">setnx lock:user1 <span class="literal">true</span></span></span><br><span class="line">OK</span><br><span class="line"></span><br><span class="line">... do something</span><br><span class="line"><span class="meta prompt_"></span></span><br><span class="line"><span class="meta prompt_">&gt; </span><span class="language-bash">del lock:user1</span></span><br><span class="line">(integer) 1</span><br></pre></td></tr></table></figure>
 
+<h3 id="死锁问题"><a href="#死锁问题" class="headerlink" title="死锁问题"></a>死锁问题</h3><h4 id="问题一：异常引发死锁-1"><a href="#问题一：异常引发死锁-1" class="headerlink" title="问题一：异常引发死锁 1"></a>问题一：异常引发死锁 1</h4><p>如果在处理过程中，程序出现异常，将导致 del 指令没有执行成功。锁无法释放，其他线程将无法再获取锁。</p>
+<img src="/2023/11/13/simple-implementation-of-distributed-lock-based-on-Redis/Pasted%20image%2020231110182254.png" class="" title="异常引发死锁 1">
 
-<h4 id="循环引用导致-JSON-解析无限循环"><a href="#循环引用导致-JSON-解析无限循环" class="headerlink" title="循环引用导致 JSON 解析无限循环"></a>循环引用导致 JSON 解析无限循环</h4><p>并非只有自己写的递归方法可能引发栈内存溢出，有可能第三方库也会引发栈内存溢出。</p>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">class</span> <span class="title class_">StackTest_5</span> &#123;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">main</span><span class="params">(String[] args)</span> <span class="keyword">throws</span> JsonProcessingException &#123;</span><br><span class="line">        <span class="type">Department</span> <span class="variable">department</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">Department</span>();</span><br><span class="line">        department.setName(<span class="string">&quot;Tech&quot;</span>);</span><br><span class="line"></span><br><span class="line">        <span class="type">Employee</span> <span class="variable">employee1</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">Employee</span>();</span><br><span class="line">        employee1.setName(<span class="string">&quot;Tom&quot;</span>);</span><br><span class="line">        employee1.setDepartment(department);</span><br><span class="line"></span><br><span class="line">        <span class="type">Employee</span> <span class="variable">employee2</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">Employee</span>();</span><br><span class="line">        employee2.setName(<span class="string">&quot;Tim&quot;</span>);</span><br><span class="line">        employee2.setDepartment(department);</span><br><span class="line"></span><br><span class="line">        department.setEmployees(Arrays.asList(employee1, employee2));</span><br><span class="line"></span><br><span class="line">        <span class="type">ObjectMapper</span> <span class="variable">objectMapper</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">ObjectMapper</span>();</span><br><span class="line">        System.out.println(objectMapper.writeValueAsString(department));</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">static</span> <span class="keyword">class</span> <span class="title class_">Department</span> &#123;</span><br><span class="line">        <span class="keyword">private</span> String name;</span><br><span class="line">        <span class="keyword">private</span> List&lt;Employee&gt; employees;</span><br><span class="line"></span><br><span class="line">        <span class="keyword">public</span> String <span class="title function_">getName</span><span class="params">()</span> &#123;</span><br><span class="line">            <span class="keyword">return</span> name;</span><br><span class="line">        &#125;</span><br><span class="line"></span><br><span class="line">        <span class="keyword">public</span> <span class="keyword">void</span> <span class="title function_">setName</span><span class="params">(String name)</span> &#123;</span><br><span class="line">            <span class="built_in">this</span>.name = name;</span><br><span class="line">        &#125;</span><br><span class="line"></span><br><span class="line">        <span class="keyword">public</span> List&lt;Employee&gt; <span class="title function_">getEmployees</span><span class="params">()</span> &#123;</span><br><span class="line">            <span class="keyword">return</span> employees;</span><br><span class="line">        &#125;</span><br><span class="line"></span><br><span class="line">        <span class="keyword">public</span> <span class="keyword">void</span> <span class="title function_">setEmployees</span><span class="params">(List&lt;Employee&gt; employees)</span> &#123;</span><br><span class="line">            <span class="built_in">this</span>.employees = employees;</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">static</span> <span class="keyword">class</span> <span class="title class_">Employee</span> &#123;</span><br><span class="line">        <span class="keyword">private</span> String name;</span><br><span class="line">        <span class="keyword">private</span> Department department;</span><br><span class="line"></span><br><span class="line">        <span class="keyword">public</span> String <span class="title function_">getName</span><span class="params">()</span> &#123;</span><br><span class="line">            <span class="keyword">return</span> name;</span><br><span class="line">        &#125;</span><br><span class="line"></span><br><span class="line">        <span class="keyword">public</span> <span class="keyword">void</span> <span class="title function_">setName</span><span class="params">(String name)</span> &#123;</span><br><span class="line">            <span class="built_in">this</span>.name = name;</span><br><span class="line">        &#125;</span><br><span class="line"></span><br><span class="line">        <span class="keyword">public</span> Department <span class="title function_">getDepartment</span><span class="params">()</span> &#123;</span><br><span class="line">            <span class="keyword">return</span> department;</span><br><span class="line">        &#125;</span><br><span class="line"></span><br><span class="line">        <span class="keyword">public</span> <span class="keyword">void</span> <span class="title function_">setDepartment</span><span class="params">(Department department)</span> &#123;</span><br><span class="line">            <span class="built_in">this</span>.department = department;</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+<h4 id="改进一：设置超时时间"><a href="#改进一：设置超时时间" class="headerlink" title="改进一：设置超时时间"></a>改进一：设置超时时间</h4><p>对 key 设置过期时间，如果在处理过程中，程序出现异常，导致 del 指令没有执行成功，设置的过期时间一到，key 将自动被删除，锁也就等于被释放了。</p>
+<figure class="highlight console"><table><tr><td class="code"><pre><span class="line"><span class="meta prompt_">&gt; </span><span class="language-bash">setnx lock:user1 <span class="literal">true</span></span></span><br><span class="line">OK</span><br><span class="line"><span class="meta prompt_">&gt; </span><span class="language-bash">expire lock:user1 5</span></span><br><span class="line"></span><br><span class="line">... do something</span><br><span class="line"><span class="meta prompt_"></span></span><br><span class="line"><span class="meta prompt_">&gt; </span><span class="language-bash">del lock:user1</span></span><br><span class="line">(integer) 1</span><br></pre></td></tr></table></figure>
 
-<h3 id="局部变量的线程安全问题"><a href="#局部变量的线程安全问题" class="headerlink" title="局部变量的线程安全问题"></a>局部变量的线程安全问题</h3><ol>
-<li>局部变量如果未逃离方法的作用范围，就是线程安全的。</li>
-<li>局部变量如果是引用类型且逃离了方法的作用范围，就是线程不安全的。</li>
-</ol>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">class</span> <span class="title class_">StackTest_3</span> &#123;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">main</span><span class="params">(String[] args)</span> &#123;</span><br><span class="line">        method1();</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 线程安全</span></span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">method1</span><span class="params">()</span> &#123;</span><br><span class="line">        <span class="type">StringBuilder</span> <span class="variable">sb</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">StringBuilder</span>();</span><br><span class="line">        sb.append(<span class="number">1</span>);</span><br><span class="line">        sb.append(<span class="number">2</span>);</span><br><span class="line">        sb.append(<span class="number">3</span>);</span><br><span class="line">        System.out.println(sb);</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 线程不安全</span></span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">method2</span><span class="params">(StringBuilder sb)</span> &#123;</span><br><span class="line">        sb.append(<span class="number">1</span>);</span><br><span class="line">        sb.append(<span class="number">2</span>);</span><br><span class="line">        sb.append(<span class="number">3</span>);</span><br><span class="line">        System.out.println(sb);</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 线程不安全，看到一个说法：发生指令重排，sb 的 append 操作发生在返回之后（有待确认）</span></span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">static</span> StringBuilder <span class="title function_">method3</span><span class="params">()</span> &#123;</span><br><span class="line">        <span class="type">StringBuilder</span> <span class="variable">sb</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">StringBuilder</span>();</span><br><span class="line">        sb.append(<span class="number">1</span>);</span><br><span class="line">        sb.append(<span class="number">2</span>);</span><br><span class="line">        sb.append(<span class="number">3</span>);</span><br><span class="line">        <span class="keyword">return</span> sb;</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+<h4 id="问题二：异常引发死锁-2"><a href="#问题二：异常引发死锁-2" class="headerlink" title="问题二：异常引发死锁 2"></a>问题二：异常引发死锁 2</h4><p>事实上，上述措施并没有彻底解决问题。如果在设置 key 的超时时间之前，程序出现异常，一切仍旧会发生。</p>
+<img src="/2023/11/13/simple-implementation-of-distributed-lock-based-on-Redis/Pasted%20image%2020231110190407.png" class="" title="异常引发死锁 2">
 
-<h3 id="线程问题排查"><a href="#线程问题排查" class="headerlink" title="线程问题排查"></a>线程问题排查</h3><h4 id="CPU-占用率居高不下"><a href="#CPU-占用率居高不下" class="headerlink" title="CPU 占用率居高不下"></a>CPU 占用率居高不下</h4><figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">class</span> <span class="title class_">ThreadTest_1</span> &#123;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">main</span><span class="params">(String[] args)</span> &#123;</span><br><span class="line">        <span class="keyword">new</span> <span class="title class_">Thread</span>(<span class="literal">null</span>, () -&gt; &#123;</span><br><span class="line">            System.out.println(<span class="string">&quot;t1...&quot;</span>);</span><br><span class="line">            <span class="keyword">while</span> (<span class="literal">true</span>) &#123;</span><br><span class="line"></span><br><span class="line">            &#125;</span><br><span class="line">        &#125;, <span class="string">&quot;thread1&quot;</span>).start();</span><br><span class="line"></span><br><span class="line">        <span class="keyword">new</span> <span class="title class_">Thread</span>(<span class="literal">null</span>, () -&gt; &#123;</span><br><span class="line">            System.out.println(<span class="string">&quot;t2...&quot;</span>);</span><br><span class="line">            <span class="keyword">try</span> &#123;</span><br><span class="line">                TimeUnit.SECONDS.sleep(<span class="number">1000</span>);</span><br><span class="line">            &#125; <span class="keyword">catch</span> (InterruptedException e) &#123;</span><br><span class="line">                e.printStackTrace();</span><br><span class="line">            &#125;</span><br><span class="line">        &#125;, <span class="string">&quot;thread2&quot;</span>).start();</span><br><span class="line"></span><br><span class="line">        <span class="keyword">new</span> <span class="title class_">Thread</span>(<span class="literal">null</span>, () -&gt; &#123;</span><br><span class="line">            System.out.println(<span class="string">&quot;t3...&quot;</span>);</span><br><span class="line">            <span class="keyword">try</span> &#123;</span><br><span class="line">                TimeUnit.SECONDS.sleep(<span class="number">1000</span>);</span><br><span class="line">            &#125; <span class="keyword">catch</span> (InterruptedException e) &#123;</span><br><span class="line">                e.printStackTrace();</span><br><span class="line">            &#125;</span><br><span class="line">        &#125;, <span class="string">&quot;thread3&quot;</span>).start();</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
-<p>当发现 CPU 占用率居高不下时，可以尝试以下步骤：</p>
-<ol>
-<li><code>top</code>，定位 cpu 占用高的进程 id。</li>
-<li><code>ps H -eo pid,tid,%cpu | grep pid</code>，进一步定位引起 cpu 占用高的线程 id。</li>
-<li><code>jstack pid</code>，根据线程 id 换算成 16进制的 nid 找到对应线程，进一步定位到问题的源码行号。</li>
-</ol>
-<figure class="highlight console"><table><tr><td class="code"><pre><span class="line">&quot;thread1&quot; #8 prio=5 os_prio=0 tid=0x00007f9bd0162800 nid=0x1061ad runnable [0x00007f9bd56eb000]</span><br><span class="line">   java.lang.Thread.State: RUNNABLE</span><br><span class="line">	at com.moralok.jvm.thread.ThreadTest_1.lambda$main$0(ThreadTest_1.java:10)</span><br><span class="line">	at com.moralok.jvm.thread.ThreadTest_1$$Lambda$1/250421012.run(Unknown Source)</span><br><span class="line">	at java.lang.Thread.run(Thread.java:750)</span><br></pre></td></tr></table></figure>
+<p>本质原因是 setnx 和 expire 两个指令不是一个原子操作。那么是否可以使用 Redis 的事务解决呢？不行。因为 expire 依赖于 setnx 的执行结果，如果 setnx 没有成功，expire 就不应该执行。</p>
+<h4 id="改进二：setnx-expire-的原子指令"><a href="#改进二：setnx-expire-的原子指令" class="headerlink" title="改进二：setnx + expire 的原子指令"></a>改进二：setnx + expire 的原子指令</h4><p>如果 setnx 和 expire 可以用一个原子指令实现就好了。</p>
+<img src="/2023/11/13/simple-implementation-of-distributed-lock-based-on-Redis/Pasted%20image%2020231110190442.png" class="" title="setnx + expire 原子指令">
 
-<h4 id="死锁，迟迟未返回结果"><a href="#死锁，迟迟未返回结果" class="headerlink" title="死锁，迟迟未返回结果"></a>死锁，迟迟未返回结果</h4><figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">class</span> <span class="title class_">ThreadTest_2</span> &#123;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">static</span> <span class="keyword">final</span> <span class="type">Object</span> <span class="variable">A</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">Object</span>();</span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">static</span> <span class="keyword">final</span> <span class="type">Object</span> <span class="variable">B</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">Object</span>();</span><br><span class="line"></span><br><span class="line">    <span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">main</span><span class="params">(String[] args)</span> &#123;</span><br><span class="line">        <span class="keyword">new</span> <span class="title class_">Thread</span>(<span class="literal">null</span>, () -&gt; &#123;</span><br><span class="line">            System.out.println(<span class="string">&quot;t1...&quot;</span>);</span><br><span class="line">            <span class="keyword">synchronized</span> (A) &#123;</span><br><span class="line">                System.out.println(Thread.currentThread().getName() + <span class="string">&quot; get A&quot;</span>);</span><br><span class="line">                <span class="keyword">try</span> &#123;</span><br><span class="line">                    TimeUnit.SECONDS.sleep(<span class="number">5</span>);</span><br><span class="line">                &#125; <span class="keyword">catch</span> (InterruptedException e) &#123;</span><br><span class="line">                    <span class="keyword">throw</span> <span class="keyword">new</span> <span class="title class_">RuntimeException</span>(e);</span><br><span class="line">                &#125;</span><br><span class="line">                <span class="keyword">synchronized</span> (B) &#123;</span><br><span class="line">                    System.out.println(Thread.currentThread().getName() + <span class="string">&quot; get B&quot;</span>);</span><br><span class="line">                &#125;</span><br><span class="line">            &#125;</span><br><span class="line">        &#125;, <span class="string">&quot;thread1&quot;</span>).start();</span><br><span class="line"></span><br><span class="line">        <span class="keyword">new</span> <span class="title class_">Thread</span>(<span class="literal">null</span>, () -&gt; &#123;</span><br><span class="line">            System.out.println(<span class="string">&quot;t2...&quot;</span>);</span><br><span class="line">            <span class="keyword">synchronized</span> (B) &#123;</span><br><span class="line">                System.out.println(Thread.currentThread().getName() + <span class="string">&quot; get B&quot;</span>);</span><br><span class="line">                <span class="keyword">try</span> &#123;</span><br><span class="line">                    TimeUnit.SECONDS.sleep(<span class="number">5</span>);</span><br><span class="line">                &#125; <span class="keyword">catch</span> (InterruptedException e) &#123;</span><br><span class="line">                    <span class="keyword">throw</span> <span class="keyword">new</span> <span class="title class_">RuntimeException</span>(e);</span><br><span class="line">                &#125;</span><br><span class="line">                <span class="keyword">synchronized</span> (A) &#123;</span><br><span class="line">                    System.out.println(Thread.currentThread().getName() + <span class="string">&quot; get A&quot;</span>);</span><br><span class="line">                &#125;</span><br><span class="line">            &#125;</span><br><span class="line">        &#125;, <span class="string">&quot;thread2&quot;</span>).start();</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+<h5 id="基于原生指令的实现"><a href="#基于原生指令的实现" class="headerlink" title="基于原生指令的实现"></a>基于原生指令的实现</h5><p>在 Redis 2.8 版本中，Redis 的作者加入 set 指令扩展参数，允许 setnx 和 expire 组合成一个原子指令。</p>
+<figure class="highlight console"><table><tr><td class="code"><pre><span class="line"><span class="meta prompt_">&gt; </span><span class="language-bash"><span class="built_in">set</span> lock:user1 <span class="literal">true</span> ex 5 nx</span></span><br><span class="line">OK</span><br><span class="line"></span><br><span class="line">... do something</span><br><span class="line"><span class="meta prompt_"></span></span><br><span class="line"><span class="meta prompt_">&gt; </span><span class="language-bash">del lock:user1</span></span><br><span class="line">(integer) 1</span><br></pre></td></tr></table></figure>
 
-<ol>
-<li><code>jstack pid</code>，会显示找到死锁，以及死锁涉及的线程,，并各自持有的锁还有等待的锁。</li>
-<li>其他工具如 jconsole 也具有检测死锁的功能。</li>
-</ol>
-<h2 id="本地方法栈"><a href="#本地方法栈" class="headerlink" title="本地方法栈"></a>本地方法栈</h2><h2 id="堆"><a href="#堆" class="headerlink" title="堆"></a>堆</h2><p>堆（Heap）的特点：</p>
-<ol>
-<li>线程共享，需要考虑线程安全问题。</li>
-<li>存在垃圾回收机制。</li>
-<li>使用 -Xmx8m 设置大小。</li>
-</ol>
-<h3 id="堆内存溢出"><a href="#堆内存溢出" class="headerlink" title="堆内存溢出"></a>堆内存溢出</h3><p>既然堆有垃圾回收机制，为什么还会发生内存溢出呢？最开始的时候，我也有这样的困惑。<br>后来我才认识到，还在使用中的对象是不能被强制回收的，不再使用的对象不是立刻回收的。当创建对象却没有足够的内存空间时，如果清理掉那些不再使用的对象就有足够的内存空间，就不会发生内存溢出，程序只是表现为卡顿。</p>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">class</span> <span class="title class_">HeapTest_1</span> &#123;  </span><br><span class="line">  </span><br><span class="line">    <span class="comment">// -Xmx8m  </span></span><br><span class="line">    <span class="comment">// 不设置可能不提示 Java heap space，出错地方不同，报错信息不同  </span></span><br><span class="line">    <span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">main</span><span class="params">(String[] args)</span> &#123;  </span><br><span class="line">        <span class="type">int</span> <span class="variable">i</span> <span class="operator">=</span> <span class="number">0</span>;  </span><br><span class="line">        <span class="keyword">try</span> &#123;  </span><br><span class="line">            List&lt;String&gt; list = <span class="keyword">new</span> <span class="title class_">ArrayList</span>&lt;&gt;();  </span><br><span class="line">            <span class="type">String</span> <span class="variable">s</span> <span class="operator">=</span> <span class="string">&quot;hello&quot;</span>;  </span><br><span class="line">            <span class="keyword">while</span> (<span class="literal">true</span>) &#123;  </span><br><span class="line">                list.add(s);  </span><br><span class="line">                s = s + s;  </span><br><span class="line">                i++;  </span><br><span class="line">            &#125;  </span><br><span class="line">        &#125; <span class="keyword">catch</span> (Throwable t) &#123;  </span><br><span class="line">            t.printStackTrace();  </span><br><span class="line">        &#125; <span class="keyword">finally</span> &#123;  </span><br><span class="line">            System.out.println(<span class="string">&quot;运行次数 &quot;</span> + i);  </span><br><span class="line">        &#125;  </span><br><span class="line">    &#125;  </span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+<h5 id="基于-Lua-脚本的实现"><a href="#基于-Lua-脚本的实现" class="headerlink" title="基于 Lua 脚本的实现"></a>基于 Lua 脚本的实现</h5><p>除了使用原生的指令外，还可以使用 Lua 脚本，将多个 Redis 指令组合成一个原子指令。</p>
+<figure class="highlight lua"><table><tr><td class="code"><pre><span class="line"><span class="keyword">if</span> redis.call(<span class="string">&#x27;setnx&#x27;</span>, KEYS[<span class="number">1</span>], ARGV[<span class="number">1</span>]) == <span class="number">1</span> <span class="keyword">then</span></span><br><span class="line">  redis.call(<span class="string">&#x27;expire&#x27;</span>, KEYS[<span class="number">1</span>], ARGV[<span class="number">2</span>])</span><br><span class="line">  <span class="keyword">return</span> <span class="literal">true</span></span><br><span class="line"><span class="keyword">else</span></span><br><span class="line">  <span class="keyword">return</span> <span class="literal">false</span></span><br><span class="line"><span class="keyword">end</span></span><br></pre></td></tr></table></figure>
 
-<figure class="highlight console"><table><tr><td class="code"><pre><span class="line">java.lang.OutOfMemoryError: Java heap space</span><br><span class="line">	at java.util.Arrays.copyOf(Arrays.java:3332)</span><br><span class="line">	at java.lang.AbstractStringBuilder.ensureCapacityInternal(AbstractStringBuilder.java:124)</span><br><span class="line">	at java.lang.AbstractStringBuilder.append(AbstractStringBuilder.java:448)</span><br><span class="line">	at java.lang.StringBuilder.append(StringBuilder.java:141)</span><br><span class="line">	at com.moralok.jvm.memory.heap.HeapTest_1.main(HeapTest_1.java:21)</span><br><span class="line">运行次数 17</span><br></pre></td></tr></table></figure>
+<h3 id="超时问题"><a href="#超时问题" class="headerlink" title="超时问题"></a>超时问题</h3><p>基于 Redis 的分布式锁还会面临超时问题。如果在加锁和释放之间的处理逻辑过于耗时，以至于超出了 key 的过期时间，锁将在处理结束前被释放，就可能发生问题。</p>
+<img src="/2023/11/13/simple-implementation-of-distributed-lock-based-on-Redis/Pasted%20image%2020231110191738.png" class="" title="其他线程提前进入临界区">
 
-<p>堆内存溢出的发生往往需要长时间的运行，因此在排查相关问题时，可以适当调小堆内存。</p>
-<h3 id="监测堆内存"><a href="#监测堆内存" class="headerlink" title="监测堆内存"></a>监测堆内存</h3><ol>
-<li>使用 jps 查看 Java 进程列表</li>
-<li>使用 <code>jmap -heap pid</code> 查看堆内存信息</li>
-<li>还可以使用 jconsole 观察堆内存变化曲线</li>
-<li>还可以使用 VisualVM 查看堆信息</li>
-</ol>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">class</span> <span class="title class_">HeapTest_2</span> &#123;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">main</span><span class="params">(String[] args)</span> <span class="keyword">throws</span> InterruptedException &#123;</span><br><span class="line">        System.out.println(<span class="string">&quot;1...&quot;</span>);</span><br><span class="line">        TimeUnit.SECONDS.sleep(<span class="number">30</span>);</span><br><span class="line">        <span class="comment">// 堆空间占用上升 10MB</span></span><br><span class="line">        <span class="type">byte</span>[] bytes = <span class="keyword">new</span> <span class="title class_">byte</span>[<span class="number">1024</span> * <span class="number">1024</span> * <span class="number">10</span>];</span><br><span class="line">        System.out.println(<span class="string">&quot;2...&quot;</span>);</span><br><span class="line">        TimeUnit.SECONDS.sleep(<span class="number">30</span>);</span><br><span class="line">        bytes = <span class="literal">null</span>;</span><br><span class="line">        <span class="comment">// 堆空间占用下降</span></span><br><span class="line">        System.gc();</span><br><span class="line">        System.out.println(<span class="string">&quot;3...&quot;</span>);</span><br><span class="line">        TimeUnit.SECONDS.sleep(<span class="number">3000</span>);</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+<h4 id="问题一：其他线程提前进入临界区"><a href="#问题一：其他线程提前进入临界区" class="headerlink" title="问题一：其他线程提前进入临界区"></a>问题一：其他线程提前进入临界区</h4><p>如果第一个线程因为处理逻辑过于耗时导致在处理结束前锁已经被释放，其他线程将可以提前获得锁，临界区的代码将不能保证严格串行执行。</p>
+<h4 id="问题二：错误释放其他线程的锁"><a href="#问题二：错误释放其他线程的锁" class="headerlink" title="问题二：错误释放其他线程的锁"></a>问题二：错误释放其他线程的锁</h4><p>如果在第二个线程获得锁后，第一个线程刚好处理逻辑结束去释放锁，将导致第二个线程的锁提前被释放，引发连锁问题。</p>
+<h4 id="改进一：不要用于较长时间的任务"><a href="#改进一：不要用于较长时间的任务" class="headerlink" title="改进一：不要用于较长时间的任务"></a>改进一：不要用于较长时间的任务</h4><p>与其说是改进，不如说是注意事项。如果真的出现问题，造成的数据错误可能需要人工介入解决。</p>
+<p>如果真的存在这样的业务场景，应考虑使用其他解决方案加以优化。</p>
+<h4 id="改进二：使用-watchdog-实现锁续期"><a href="#改进二：使用-watchdog-实现锁续期" class="headerlink" title="改进二：使用 watchdog 实现锁续期"></a>改进二：使用 watchdog 实现锁续期</h4><p>为 Redis 的 key 设置过期时间，其实是为了解决死锁问题而做出的兜底措施。可以为获得的锁设置定时任务定期地为锁续期，以避免锁被提前释放。</p>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">private</span> <span class="keyword">void</span> <span class="title function_">scheduleRenewal</span><span class="params">()</span> &#123;</span><br><span class="line">    <span class="type">String</span> <span class="variable">value</span> <span class="operator">=</span> lockValue.get();</span><br><span class="line">    ScheduledFuture&lt;?&gt; scheduledFuture = sScheduler.scheduleAtFixedRate(</span><br><span class="line">        () -&gt; <span class="built_in">this</span>.renewal(value), RENEWAL_INTERVAL, RENEWAL_INTERVAL, TimeUnit.MILLISECONDS</span><br><span class="line">    );</span><br><span class="line">    renewalTask.set(scheduledFuture);</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
 
-<p>使用 <code>jmap -heap pid</code> 查看堆内存信息：</p>
-<figure class="highlight console"><table><tr><td class="code"><pre><span class="line">Eden Space:</span><br><span class="line">   capacity = 268435456 (256.0MB)</span><br><span class="line">   used     = 32212360 (30.72010040283203MB)</span><br><span class="line"></span><br><span class="line">   used     = 42698136 (40.720115661621094MB)</span><br><span class="line"></span><br><span class="line">   used     = 5368728 (5.120018005371094MB)</span><br></pre></td></tr></table></figure>
+<p>但是这个方式仍然不能避免解锁失败时的其他线程的等待时间。</p>
+<h4 id="改进三：加锁时指定-tag"><a href="#改进三：加锁时指定-tag" class="headerlink" title="改进三：加锁时指定 tag"></a>改进三：加锁时指定 tag</h4><p>可以将 set 指令的 value 参数设置为一个随机数，释放锁时先匹配持有的 tag 是否和 value 一致，如果一致再删除 key，以此避免锁被其他线程错误释放。</p>
+<h5 id="基于原生指令的实现-1"><a href="#基于原生指令的实现-1" class="headerlink" title="基于原生指令的实现"></a>基于原生指令的实现</h5><figure class="highlight console"><table><tr><td class="code"><pre><span class="line">tag = random.nextint()</span><br><span class="line">if redis.set(key, tag, nx= True, ex=5):</span><br><span class="line">	do_something()</span><br><span class="line">	redis.delifequals(key, tag)</span><br></pre></td></tr></table></figure>
 
-<p>使用 jconsole 查看堆内存信息：</p>
-<img src="/2023/11/04/testing-and-analysis-of-jvm-memory-area/Pasted%20image%2020231104200411.png" class="" title="jconsole 观察堆内存占用">
+<p>但是注意，Redis 并没有提供语义为 delete if equals 的原子指令，这样的话问题并不能被彻底解决。如果在第一个线程判断 tag 是否和 value 相等之后，第二个线程刚好获得了锁，然后第一个线程因为匹配成功执行删除 key 操作，仍然将导致第二个线程获得的锁被第一个线程错误释放。</p>
+<img src="/2023/11/13/simple-implementation-of-distributed-lock-based-on-Redis/Pasted%20image%2020231110193919.png" class="" title="错误释放其他线程的锁">
 
-<h3 id="堆内存占用居高不下"><a href="#堆内存占用居高不下" class="headerlink" title="堆内存占用居高不下"></a>堆内存占用居高不下</h3><p>当你发现堆内存占用居高不下，经过 GC，下降也不明显，如果你想查看一下堆内的具体情况，可以将其 dump 查看。</p>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">class</span> <span class="title class_">HeapTest_3</span> &#123;  </span><br><span class="line">  </span><br><span class="line">    <span class="comment">// jps 查进程，jmap 看堆内存，jconsole 执行GC，堆内存占用没有明显下降  </span></span><br><span class="line">    <span class="comment">// 使用 VisualVM 的堆 dump 功能，观察大对象  </span></span><br><span class="line">    <span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">main</span><span class="params">(String[] args)</span> <span class="keyword">throws</span> IOException &#123;  </span><br><span class="line">        List&lt;Student&gt; students = <span class="keyword">new</span> <span class="title class_">ArrayList</span>&lt;&gt;();  </span><br><span class="line">        <span class="keyword">for</span> (<span class="type">int</span> <span class="variable">i</span> <span class="operator">=</span> <span class="number">0</span>; i &lt; <span class="number">200</span>; i++) &#123;  </span><br><span class="line">            students.add(<span class="keyword">new</span> <span class="title class_">Student</span>());  </span><br><span class="line">        &#125;  </span><br><span class="line">        System.in.read();  </span><br><span class="line">    &#125;  </span><br><span class="line">  </span><br><span class="line">    <span class="keyword">static</span> <span class="keyword">class</span> <span class="title class_">Student</span> &#123;  </span><br><span class="line">        <span class="keyword">private</span> <span class="type">byte</span>[] score = <span class="keyword">new</span> <span class="title class_">byte</span>[<span class="number">1024</span> * <span class="number">1024</span>];  </span><br><span class="line">    &#125;  </span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
-<p>可使用 VisualVM 的 Heap Dump 功能：</p>
-<img src="/2023/11/04/testing-and-analysis-of-jvm-memory-area/Pasted%20image%2020231104201139.png" class="" title="VisualVM 观察堆中的大对象">
+<h5 id="基于-Lua-脚本的实现-1"><a href="#基于-Lua-脚本的实现-1" class="headerlink" title="基于 Lua 脚本的实现"></a>基于 Lua 脚本的实现</h5><figure class="highlight lua"><table><tr><td class="code"><pre><span class="line"><span class="keyword">if</span> redis.call(<span class="string">&quot;get&quot;</span>, KEYS[<span class="number">1</span>]) == ARGV[<span class="number">1</span>] <span class="keyword">then</span></span><br><span class="line">  <span class="keyword">return</span> redis.call(<span class="string">&quot;del&quot;</span>, KEYS[<span class="number">1</span>])</span><br><span class="line"><span class="keyword">else</span></span><br><span class="line">  <span class="keyword">return</span> <span class="number">0</span></span><br><span class="line"><span class="keyword">end</span></span><br></pre></td></tr></table></figure>
 
-<p>也可使用 <code>jmap -dump:format=b,file=filename.hprof pid</code>，需要其他分析工具搭配。</p>
-<h2 id="方法区"><a href="#方法区" class="headerlink" title="方法区"></a>方法区</h2><p>根据《Java虚拟机规范》，方法区在逻辑上是堆的一部分，但是在具体实现上，各个虚拟机厂商并不相同。对于 Hotspot 而言：</p>
-<ul>
-<li>JDK 8 之前，方法区的具体实现为永久代，使用堆内存，使用 -XX:MaxPermSize&#x3D;10m 设置大小。</li>
-<li>JDK 8 开始，方法区的具体实现为元空间，使用直接内存，使用 -XX:MaxMetaspaceSize&#x3D;10m 设置大小。</li>
-</ul>
-<h3 id="方法区溢出"><a href="#方法区溢出" class="headerlink" title="方法区溢出"></a>方法区溢出</h3><figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">class</span> <span class="title class_">MethodAreaTest_1</span> <span class="keyword">extends</span> <span class="title class_">ClassLoader</span> &#123;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// -XX:MaxMetaspaceSize=8m MaxMetaspaceSize is too small.</span></span><br><span class="line">    <span class="comment">// -XX:MaxMetaspaceSize=10m java.lang.OutOfMemoryError: Compressed class space</span></span><br><span class="line">    <span class="comment">// 不是 Metaspace 应该是某个参数设置的问题</span></span><br><span class="line">    <span class="comment">// JDK 6: -XX:MaxPermSize=8m PermGen space</span></span><br><span class="line">    <span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">main</span><span class="params">(String[] args)</span> &#123;</span><br><span class="line">        <span class="type">int</span> <span class="variable">j</span> <span class="operator">=</span> <span class="number">0</span>;</span><br><span class="line">        <span class="keyword">try</span> &#123;</span><br><span class="line">            <span class="type">MethodAreaTest_1</span> <span class="variable">methodAreaTest1</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">MethodAreaTest_1</span>();</span><br><span class="line">            <span class="keyword">for</span> (<span class="type">int</span> <span class="variable">i</span> <span class="operator">=</span> <span class="number">0</span>; i &lt; <span class="number">20000</span>; i++, j++) &#123;</span><br><span class="line">                <span class="type">ClassWriter</span> <span class="variable">classWriter</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">ClassWriter</span>(<span class="number">0</span>);</span><br><span class="line">                <span class="comment">// 版本号，public，类名，包名，父类，接口</span></span><br><span class="line">                classWriter.visit(Opcodes.V1_8, Opcodes.ACC_PUBLIC, <span class="string">&quot;Class&quot;</span> + i, <span class="literal">null</span>, <span class="string">&quot;java/lang/Object&quot;</span>, <span class="literal">null</span>);</span><br><span class="line">                <span class="comment">// 返回二进制字节码</span></span><br><span class="line">                <span class="type">byte</span>[] code = classWriter.toByteArray();</span><br><span class="line">                <span class="comment">// 加载类</span></span><br><span class="line">                methodAreaTest1.defineClass(<span class="string">&quot;Class&quot;</span> + i, code, <span class="number">0</span>, code.length);</span><br><span class="line">            &#125;</span><br><span class="line">        &#125; <span class="keyword">catch</span> (ClassFormatError e) &#123;</span><br><span class="line">            e.printStackTrace();</span><br><span class="line">        &#125; <span class="keyword">finally</span> &#123;</span><br><span class="line">            System.out.println(<span class="string">&quot;次数 &quot;</span> + j);</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
-<ol>
-<li>当设置的值太小时 -XX:MaxMetaspaceSize&#x3D;8m，提示 MaxMetaspaceSize is too small。</li>
-<li>实验中抛出 java.lang.OutOfMemoryError: Compressed class space。</li>
-<li>添加参数 -XX:-UseCompressedClassPointers 后，抛出 java.lang.OutOfMemoryError: Metaspace。</li>
-<li>JDK 6 设置 -XX:MaxPermSize&#x3D;8m，抛出 java.lang.OutOfMemoryError: PermGen space。</li>
-</ol>
-<p>不要认为自己不会写动态生成字节码相关的代码就忽略这方面的问题，如今很多框架使用字节码技术大量地动态生成类。</p>
-<h2 id="运行时常量池"><a href="#运行时常量池" class="headerlink" title="运行时常量池"></a>运行时常量池</h2><p>二进制字节码文件主要包含三类信息：</p>
-<ol>
-<li>类的基本信息</li>
-<li>类的常量池（Constant Pool）</li>
-<li>类的方法信息</li>
-</ol>
-<h3 id="使用-javap-反编译"><a href="#使用-javap-反编译" class="headerlink" title="使用 javap 反编译"></a>使用 javap 反编译</h3><figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">class</span> <span class="title class_">MethodAreaTest_2</span> &#123;  </span><br><span class="line">  </span><br><span class="line">    <span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">main</span><span class="params">(String[] args)</span> &#123;  </span><br><span class="line">        System.out.println(<span class="string">&quot;hello world&quot;</span>);  </span><br><span class="line">    &#125;  </span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+<h3 id="可重入性"><a href="#可重入性" class="headerlink" title="可重入性"></a>可重入性</h3><p>可重入性是指线程在已经持有锁的情况下再次请求加锁，如果一个锁支持同一个线程多次加锁，那么就称这个锁是可重入的，类似 Java 的 ReentrantLock。</p>
+<h4 id="使用-ThreadLocal-实现锁计数"><a href="#使用-ThreadLocal-实现锁计数" class="headerlink" title="使用 ThreadLocal 实现锁计数"></a>使用 ThreadLocal 实现锁计数</h4><p>Redis 分布式锁如果要支持可重入，可以使用线程的 ThreadLocal 变量存储当前持有的锁计数。但是在多次获得锁后，过期时间并没有得到延长，后续获得锁后持有锁的时间其实比设置的时间更短。</p>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">private</span> ThreadLocal&lt;Integer&gt; lockCount = ThreadLocal.withInitial(() -&gt; <span class="number">0</span>);</span><br><span class="line"></span><br><span class="line"><span class="keyword">public</span> <span class="type">boolean</span> <span class="title function_">tryLock</span><span class="params">()</span> &#123;  </span><br><span class="line">    <span class="type">Integer</span> <span class="variable">count</span> <span class="operator">=</span> lockCount.get();  </span><br><span class="line">    <span class="keyword">if</span> (count != <span class="literal">null</span> &amp;&amp; count &gt; <span class="number">0</span>) &#123;  </span><br><span class="line">        lockCount.set(count + <span class="number">1</span>);   </span><br><span class="line">        <span class="keyword">return</span> <span class="literal">true</span>;    </span><br><span class="line">    &#125;  </span><br><span class="line">    <span class="type">String</span> <span class="variable">result</span> <span class="operator">=</span> commands.set(lockKey, lockValue.get(), SetArgs.Builder.nx().px(RedisLockManager.LOCK_EXPIRE));  </span><br><span class="line">    <span class="keyword">if</span> (<span class="string">&quot;OK&quot;</span>.equals(result)) &#123;  </span><br><span class="line">        lockCount.set(<span class="number">1</span>);  </span><br><span class="line">        scheduleRenewal();  </span><br><span class="line">        <span class="keyword">return</span> <span class="literal">true</span>;    </span><br><span class="line">    &#125;  </span><br><span class="line">    <span class="keyword">return</span> <span class="literal">false</span>;  </span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
 
-<figure class="highlight console"><table><tr><td class="code"><pre><span class="line">Classfile /C:/Users/username/Documents/github/jvm-study/target/classes/com/moralok/jvm/memory/methodarea/MethodAreaTest_2.class</span><br><span class="line">  Last modified 2023-11-4; size 619 bytes</span><br><span class="line">  MD5 checksum 0ed10a8f0a03be54fd4159958ee7446c</span><br><span class="line">  Compiled from &quot;MethodAreaTest_2.java&quot;</span><br><span class="line">public class com.moralok.jvm.memory.methodarea.MethodAreaTest_2</span><br><span class="line">  minor version: 0</span><br><span class="line">  major version: 52</span><br><span class="line">  flags: ACC_PUBLIC, ACC_SUPER</span><br><span class="line">Constant pool:</span><br><span class="line"><span class="meta prompt_">   #</span><span class="language-bash">1 = Methodref          <span class="comment">#6.#20         // java/lang/Object.&quot;&lt;init&gt;&quot;:()V</span></span></span><br><span class="line"><span class="meta prompt_">   #</span><span class="language-bash">2 = Fieldref           <span class="comment">#21.#22        // java/lang/System.out:Ljava/io/PrintStream;</span></span></span><br><span class="line"><span class="meta prompt_">   #</span><span class="language-bash">3 = String             <span class="comment">#23            // hello world</span></span></span><br><span class="line"><span class="meta prompt_">   #</span><span class="language-bash">4 = Methodref          <span class="comment">#24.#25        // java/io/PrintStream.println:(Ljava/lang/String;)V</span></span></span><br><span class="line"><span class="meta prompt_">   #</span><span class="language-bash">5 = Class              <span class="comment">#26            // com/moralok/jvm/memory/methodarea/MethodAreaTest_2</span></span></span><br><span class="line"><span class="meta prompt_">   #</span><span class="language-bash">6 = Class              <span class="comment">#27            // java/lang/Object</span></span></span><br><span class="line"><span class="meta prompt_">   #</span><span class="language-bash">7 = Utf8               &lt;init&gt;</span></span><br><span class="line"><span class="meta prompt_">   #</span><span class="language-bash">8 = Utf8               ()V</span></span><br><span class="line"><span class="meta prompt_">   #</span><span class="language-bash">9 = Utf8               Code</span></span><br><span class="line"><span class="meta prompt_">  #</span><span class="language-bash">10 = Utf8               LineNumberTable</span></span><br><span class="line"><span class="meta prompt_">  #</span><span class="language-bash">11 = Utf8               LocalVariableTable</span></span><br><span class="line"><span class="meta prompt_">  #</span><span class="language-bash">12 = Utf8               this</span></span><br><span class="line"><span class="meta prompt_">  #</span><span class="language-bash">13 = Utf8               Lcom/moralok/jvm/memory/methodarea/MethodAreaTest_2;</span></span><br><span class="line"><span class="meta prompt_">  #</span><span class="language-bash">14 = Utf8               main</span></span><br><span class="line"><span class="meta prompt_">  #</span><span class="language-bash">15 = Utf8               ([Ljava/lang/String;)V</span></span><br><span class="line"><span class="meta prompt_">  #</span><span class="language-bash">16 = Utf8               args</span></span><br><span class="line"><span class="meta prompt_">  #</span><span class="language-bash">17 = Utf8               [Ljava/lang/String;</span></span><br><span class="line"><span class="meta prompt_">  #</span><span class="language-bash">18 = Utf8               SourceFile</span></span><br><span class="line"><span class="meta prompt_">  #</span><span class="language-bash">19 = Utf8               MethodAreaTest_2.java</span></span><br><span class="line"><span class="meta prompt_">  #</span><span class="language-bash">20 = NameAndType        <span class="comment">#7:#8          // &quot;&lt;init&gt;&quot;:()V</span></span></span><br><span class="line"><span class="meta prompt_">  #</span><span class="language-bash">21 = Class              <span class="comment">#28            // java/lang/System</span></span></span><br><span class="line"><span class="meta prompt_">  #</span><span class="language-bash">22 = NameAndType        <span class="comment">#29:#30        // out:Ljava/io/PrintStream;</span></span></span><br><span class="line"><span class="meta prompt_">  #</span><span class="language-bash">23 = Utf8               hello world</span></span><br><span class="line"><span class="meta prompt_">  #</span><span class="language-bash">24 = Class              <span class="comment">#31            // java/io/PrintStream</span></span></span><br><span class="line"><span class="meta prompt_">  #</span><span class="language-bash">25 = NameAndType        <span class="comment">#32:#33        // println:(Ljava/lang/String;)V</span></span></span><br><span class="line"><span class="meta prompt_">  #</span><span class="language-bash">26 = Utf8               com/moralok/jvm/memory/methodarea/MethodAreaTest_2</span></span><br><span class="line"><span class="meta prompt_">  #</span><span class="language-bash">27 = Utf8               java/lang/Object</span></span><br><span class="line"><span class="meta prompt_">  #</span><span class="language-bash">28 = Utf8               java/lang/System</span></span><br><span class="line"><span class="meta prompt_">  #</span><span class="language-bash">29 = Utf8               out</span></span><br><span class="line"><span class="meta prompt_">  #</span><span class="language-bash">30 = Utf8               Ljava/io/PrintStream;</span></span><br><span class="line"><span class="meta prompt_">  #</span><span class="language-bash">31 = Utf8               java/io/PrintStream</span></span><br><span class="line"><span class="meta prompt_">  #</span><span class="language-bash">32 = Utf8               println</span></span><br><span class="line"><span class="meta prompt_">  #</span><span class="language-bash">33 = Utf8               (Ljava/lang/String;)V</span></span><br><span class="line">&#123;</span><br><span class="line">  public com.moralok.jvm.memory.methodarea.MethodAreaTest_2();</span><br><span class="line">    descriptor: ()V</span><br><span class="line">    flags: ACC_PUBLIC</span><br><span class="line">    Code:</span><br><span class="line">      stack=1, locals=1, args_size=1</span><br><span class="line">         0: aload_0</span><br><span class="line">         1: invokespecial #1                  // Method java/lang/Object.&quot;&lt;init&gt;&quot;:()V</span><br><span class="line">         4: return</span><br><span class="line">      LineNumberTable:</span><br><span class="line">        line 3: 0</span><br><span class="line">      LocalVariableTable:</span><br><span class="line">        Start  Length  Slot  Name   Signature</span><br><span class="line">            0       5     0  this   Lcom/moralok/jvm/memory/methodarea/MethodAreaTest_2;</span><br><span class="line"></span><br><span class="line">  public static void main(java.lang.String[]);</span><br><span class="line">    descriptor: ([Ljava/lang/String;)V</span><br><span class="line">    flags: ACC_PUBLIC, ACC_STATIC</span><br><span class="line">    Code:</span><br><span class="line">      stack=2, locals=1, args_size=1</span><br><span class="line">         0: getstatic     #2                  // Field java/lang/System.out:Ljava/io/PrintStream;</span><br><span class="line">         3: ldc           #3                  // String hello world</span><br><span class="line">         5: invokevirtual #4                  // Method java/io/PrintStream.println:(Ljava/lang/String;)V</span><br><span class="line">         8: return</span><br><span class="line">      LineNumberTable:</span><br><span class="line">        line 6: 0</span><br><span class="line">        line 7: 8</span><br><span class="line">      LocalVariableTable:</span><br><span class="line">        Start  Length  Slot  Name   Signature</span><br><span class="line">            0       9     0  args   [Ljava/lang/String;</span><br><span class="line">&#125;</span><br><span class="line">SourceFile: &quot;MethodAreaTest_2.java&quot;</span><br></pre></td></tr></table></figure>
-
-<ol>
-<li>Class 文件的常量池就是一张表，虚拟机根据索引去查找类名、字段名及其类型，方法名及其参数类型和字面量等。</li>
-<li>当类被加载到虚拟机之后，Class 文件中的常量池中的信息就进入到了运行时常量池。</li>
-<li>这个过程其实就是信息从文件进入了内存。</li>
-</ol>
-<p>虚拟机解释器（interpreter）需要解释的字节码指令如下：</p>
-<figure class="highlight console"><table><tr><td class="code"><pre><span class="line">0: getstatic     #2</span><br><span class="line">3: ldc           #3</span><br><span class="line">5: invokevirtual #4</span><br></pre></td></tr></table></figure>
-<p>索引 <code>#2</code> 的意思就是去常量表里查找对应项代表的事物。</p>
-<h2 id="直接内存"><a href="#直接内存" class="headerlink" title="直接内存"></a>直接内存</h2><ul>
-<li>常见于 NIO 操作中的数据缓冲区。</li>
-<li>分配和回收的成本较高，但读写性能更高。</li>
-<li>不由 JVM 进行内存释放</li>
-</ul>
-<h3 id="NIO-和-IO-的拷贝性能"><a href="#NIO-和-IO-的拷贝性能" class="headerlink" title="NIO 和 IO 的拷贝性能"></a>NIO 和 IO 的拷贝性能</h3><figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">class</span> <span class="title class_">DirectMemoryTest_1</span> &#123;  </span><br><span class="line">  </span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">static</span> <span class="keyword">final</span> <span class="type">String</span> <span class="variable">FROM</span> <span class="operator">=</span> <span class="string">&quot;C:\\Users\\username\\Videos\\jellyfin\\media\\movies\\Harry Potter and the Chamber of Secrets (2002) [1080p]\\Harry.Potter.and.the.Chamber.of.Secrets.2002.1080p.BrRip.x264.YIFY.mp4&quot;</span>;  </span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">static</span> <span class="keyword">final</span> <span class="type">String</span> <span class="variable">TO</span> <span class="operator">=</span> <span class="string">&quot;C:\\Users\\username\\Videos\\jellyfin\\media\\movies\\Harry Potter and the Chamber of Secrets (2002) [1080p]\\Harry.Potter.and.the.Chamber.of.Secrets.2002.1080p.BrRip.x264.YIFY-copy.mp4&quot;</span>;  </span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">static</span> <span class="keyword">final</span> <span class="type">int</span> <span class="variable">_1Mb</span> <span class="operator">=</span> <span class="number">1024</span> * <span class="number">1024</span>;  </span><br><span class="line">  </span><br><span class="line">    <span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">main</span><span class="params">(String[] args)</span> &#123;  </span><br><span class="line">        io();  </span><br><span class="line">        directBuffer();  </span><br><span class="line">    &#125;  </span><br><span class="line">  </span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">directBuffer</span><span class="params">()</span> &#123;  </span><br><span class="line">        <span class="type">long</span> <span class="variable">start</span> <span class="operator">=</span> System.nanoTime();  </span><br><span class="line">        <span class="keyword">try</span> (<span class="type">FileChannel</span> <span class="variable">from</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">FileInputStream</span>(FROM).getChannel();  </span><br><span class="line">             <span class="type">FileChannel</span> <span class="variable">to</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">FileOutputStream</span>(TO).getChannel()) &#123;  </span><br><span class="line">            <span class="type">ByteBuffer</span> <span class="variable">buffer</span> <span class="operator">=</span> ByteBuffer.allocateDirect(_1Mb);  </span><br><span class="line">            <span class="keyword">while</span> (<span class="literal">true</span>) &#123;  </span><br><span class="line">                <span class="type">int</span> <span class="variable">len</span> <span class="operator">=</span> from.read(buffer);  </span><br><span class="line">                <span class="keyword">if</span> (len == -<span class="number">1</span>) &#123;  </span><br><span class="line">                    <span class="keyword">break</span>;  </span><br><span class="line">                &#125;  </span><br><span class="line">                buffer.flip();  </span><br><span class="line">                to.write(buffer);  </span><br><span class="line">                buffer.clear();  </span><br><span class="line">            &#125;  </span><br><span class="line">        &#125; <span class="keyword">catch</span> (IOException e) &#123;  </span><br><span class="line">            e.printStackTrace();  </span><br><span class="line">        &#125;  </span><br><span class="line">        <span class="type">long</span> <span class="variable">end</span> <span class="operator">=</span> System.nanoTime();  </span><br><span class="line">        System.out.println(<span class="string">&quot;directBuffer 用时 &quot;</span> + (end - start) / <span class="number">1000_000.0</span>);  </span><br><span class="line">    &#125;  </span><br><span class="line">  </span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">io</span><span class="params">()</span> &#123;  </span><br><span class="line">        <span class="type">long</span> <span class="variable">start</span> <span class="operator">=</span> System.nanoTime();  </span><br><span class="line">        <span class="keyword">try</span> (<span class="type">FileInputStream</span> <span class="variable">from</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">FileInputStream</span>(FROM);  </span><br><span class="line">             <span class="type">FileOutputStream</span> <span class="variable">to</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">FileOutputStream</span>(TO)) &#123;  </span><br><span class="line">            <span class="type">byte</span>[] buffer = <span class="keyword">new</span> <span class="title class_">byte</span>[_1Mb];  </span><br><span class="line">            <span class="keyword">while</span> (<span class="literal">true</span>) &#123;  </span><br><span class="line">                <span class="type">int</span> <span class="variable">len</span> <span class="operator">=</span> from.read(buffer);  </span><br><span class="line">                <span class="keyword">if</span> (len == -<span class="number">1</span>) &#123;  </span><br><span class="line">                    <span class="keyword">break</span>;  </span><br><span class="line">                &#125;  </span><br><span class="line">                to.write(buffer);  </span><br><span class="line">            &#125;  </span><br><span class="line">        &#125; <span class="keyword">catch</span> (IOException e) &#123;  </span><br><span class="line">            e.printStackTrace();  </span><br><span class="line">        &#125;  </span><br><span class="line">        <span class="type">long</span> <span class="variable">end</span> <span class="operator">=</span> System.nanoTime();  </span><br><span class="line">        System.out.println(<span class="string">&quot;io 用时 &quot;</span> + (end - start) / <span class="number">1000_000.0</span>);  </span><br><span class="line">    &#125;  </span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
-
-<figure class="highlight console"><table><tr><td class="code"><pre><span class="line">io 用时 1676.9797</span><br><span class="line">directBuffer 用时 836.4796</span><br></pre></td></tr></table></figure>
-
-<img src="/2023/11/04/testing-and-analysis-of-jvm-memory-area/Pasted%20image%2020231104235546.png" class="" title="普通的 IO 拷贝">
-
-<img src="/2023/11/04/testing-and-analysis-of-jvm-memory-area/Pasted%20image%2020231104235846.png" class="" title="NIO 拷贝">
-
-
-<h3 id="直接内存溢出"><a href="#直接内存溢出" class="headerlink" title="直接内存溢出"></a>直接内存溢出</h3><figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">class</span> <span class="title class_">DirectMemoryTest_2</span> &#123;  </span><br><span class="line">  </span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">static</span> <span class="keyword">final</span> <span class="type">int</span> <span class="variable">_100Mb</span> <span class="operator">=</span> <span class="number">1024</span> * <span class="number">1024</span> * <span class="number">100</span>;  </span><br><span class="line">  </span><br><span class="line">    <span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">main</span><span class="params">(String[] args)</span> &#123;  </span><br><span class="line">        List&lt;ByteBuffer&gt; list = <span class="keyword">new</span> <span class="title class_">ArrayList</span>&lt;&gt;();  </span><br><span class="line">        <span class="type">int</span> <span class="variable">i</span> <span class="operator">=</span> <span class="number">0</span>;  </span><br><span class="line">        <span class="keyword">try</span> &#123;  </span><br><span class="line">            <span class="keyword">while</span> (<span class="literal">true</span>) &#123;  </span><br><span class="line">                <span class="type">ByteBuffer</span> <span class="variable">byteBuffer</span> <span class="operator">=</span> ByteBuffer.allocateDirect(_100Mb);  </span><br><span class="line">                list.add(byteBuffer);  </span><br><span class="line">                i++;  </span><br><span class="line">            &#125;  </span><br><span class="line">        &#125; <span class="keyword">catch</span> (Throwable t) &#123;  </span><br><span class="line">            t.printStackTrace();  </span><br><span class="line">        &#125; System.out.println(i);  </span><br><span class="line">    &#125;  </span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
-
-<figure class="highlight console"><table><tr><td class="code"><pre><span class="line">java.lang.OutOfMemoryError: Direct buffer memory</span><br><span class="line">	at java.nio.Bits.reserveMemory(Bits.java:695)</span><br><span class="line">	at java.nio.DirectByteBuffer.&lt;init&gt;(DirectByteBuffer.java:123)</span><br><span class="line">	at java.nio.ByteBuffer.allocateDirect(ByteBuffer.java:311)</span><br><span class="line">	at com.moralok.jvm.memory.direct.DirectMemoryTest_2.main(DirectMemoryTest_2.java:16)</span><br><span class="line">145</span><br></pre></td></tr></table></figure>
-
-<p>这似乎是代码中抛出的异常，而不是真正的直接内存溢出？</p>
-<h3 id="直接内存释放的原理"><a href="#直接内存释放的原理" class="headerlink" title="直接内存释放的原理"></a>直接内存释放的原理</h3><h4 id="演示直接内存的释放受-GC-影响"><a href="#演示直接内存的释放受-GC-影响" class="headerlink" title="演示直接内存的释放受 GC 影响"></a>演示直接内存的释放受 GC 影响</h4><figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">class</span> <span class="title class_">DirectMemoryTest_3</span> &#123;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">static</span> <span class="keyword">final</span> <span class="type">int</span> <span class="variable">_1GB</span> <span class="operator">=</span> <span class="number">1024</span> * <span class="number">1024</span> * <span class="number">1024</span>;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">main</span><span class="params">(String[] args)</span> <span class="keyword">throws</span> IOException &#123;</span><br><span class="line">        <span class="type">ByteBuffer</span> <span class="variable">byteBuffer</span> <span class="operator">=</span> ByteBuffer.allocateDirect(_1GB);</span><br><span class="line">        System.out.println(<span class="string">&quot;分配完毕&quot;</span>);</span><br><span class="line">        System.in.read();</span><br><span class="line">        System.out.println(<span class="string">&quot;开始释放&quot;</span>);</span><br><span class="line">        byteBuffer = <span class="literal">null</span>;</span><br><span class="line">        <span class="comment">// 随着 ByteBuffer 的释放，从任务管理器界面看到程序的内存的占用迅速下降 1GB。</span></span><br><span class="line">        System.gc();</span><br><span class="line">        System.in.read();</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
-
-<h4 id="手动进行直接内存的分配和释放"><a href="#手动进行直接内存的分配和释放" class="headerlink" title="手动进行直接内存的分配和释放"></a>手动进行直接内存的分配和释放</h4><p>在代码中实现手动进行直接内存的分配和释放。</p>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">class</span> <span class="title class_">DirectMemoryTest_4</span> &#123;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">static</span> <span class="keyword">final</span> <span class="type">int</span> <span class="variable">_1GB</span> <span class="operator">=</span> <span class="number">1024</span> * <span class="number">1024</span> * <span class="number">1024</span>;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">main</span><span class="params">(String[] args)</span> <span class="keyword">throws</span> IOException &#123;</span><br><span class="line">        <span class="type">Unsafe</span> <span class="variable">unsafe</span> <span class="operator">=</span> getUnsafe();</span><br><span class="line"></span><br><span class="line">        <span class="comment">// 分配内存</span></span><br><span class="line">        <span class="type">long</span> <span class="variable">base</span> <span class="operator">=</span> unsafe.allocateMemory(_1GB);</span><br><span class="line">        unsafe.setMemory(base, _1GB, (<span class="type">byte</span>) <span class="number">0</span>);</span><br><span class="line">        System.in.read();</span><br><span class="line"></span><br><span class="line">        <span class="comment">// 释放内存</span></span><br><span class="line">        unsafe.freeMemory(base);</span><br><span class="line">        System.in.read();</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">static</span> Unsafe <span class="title function_">getUnsafe</span><span class="params">()</span> &#123;</span><br><span class="line">        <span class="keyword">try</span> &#123;</span><br><span class="line">            <span class="type">Field</span> <span class="variable">f</span> <span class="operator">=</span> Unsafe.class.getDeclaredField(<span class="string">&quot;theUnsafe&quot;</span>);</span><br><span class="line">            f.setAccessible(<span class="literal">true</span>);</span><br><span class="line">            <span class="type">Unsafe</span> <span class="variable">unsafe</span> <span class="operator">=</span> (Unsafe) f.get(<span class="literal">null</span>);</span><br><span class="line">            <span class="keyword">return</span> unsafe;</span><br><span class="line">        &#125; <span class="keyword">catch</span> (NoSuchFieldException | IllegalAccessException e) &#123;</span><br><span class="line">            <span class="keyword">throw</span> <span class="keyword">new</span> <span class="title class_">RuntimeException</span>(e);</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
-
-<h4 id="如何将-GC-和直接内存的分配和释放关联"><a href="#如何将-GC-和直接内存的分配和释放关联" class="headerlink" title="如何将 GC 和直接内存的分配和释放关联"></a>如何将 GC 和直接内存的分配和释放关联</h4><p>本质上，直接内存的自动释放是利用了虚引用的机制，间接调用了 unsafe 的分配和释放直接内存的方法。</p>
-<p>DirectByteBuffer 就是使用 unsafe.allocateMemory(size) 分配直接内存。DirectByteBuffer 对象以及一个 Deallocator 对象（Runnable 类型）一起用于创建了一个虚引用类型的 Cleaner 对象。</p>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line">DirectByteBuffer(<span class="type">int</span> cap) &#123;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 省略</span></span><br><span class="line">    <span class="keyword">try</span> &#123;</span><br><span class="line">        base = unsafe.allocateMemory(size);</span><br><span class="line">    &#125; <span class="keyword">catch</span> (OutOfMemoryError x) &#123;</span><br><span class="line">        Bits.unreserveMemory(size, cap);</span><br><span class="line">        <span class="keyword">throw</span> x;</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="comment">// 省略</span></span><br><span class="line">    cleaner = Cleaner.create(<span class="built_in">this</span>, <span class="keyword">new</span> <span class="title class_">Deallocator</span>(base, size, cap));</span><br><span class="line">    att = <span class="literal">null</span>;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
-
-<p>根据虚引用的机制，如果 DirectByteBuffer 对象被回收，虚引用对象会被加入到 Cleanner 的引用队列，ReferenceHandler 线程会处理引用队列中的 Cleaner 对象，进而调用 Deallocator 对象的 run 方法。</p>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title function_">run</span><span class="params">()</span> &#123;</span><br><span class="line">    <span class="keyword">if</span> (address == <span class="number">0</span>) &#123;</span><br><span class="line">        <span class="comment">// Paranoia</span></span><br><span class="line">        <span class="keyword">return</span>;</span><br><span class="line">    &#125;</span><br><span class="line">    unsafe.freeMemory(address);</span><br><span class="line">    address = <span class="number">0</span>;</span><br><span class="line">    Bits.unreserveMemory(size, capacity);</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
-]]></content>
-      <tags>
-        <tag>java</tag>
-        <tag>jvm</tag>
-      </tags>
-  </entry>
-  <entry>
-    <title>基于 Redis 的分布式锁的简单实现</title>
-    <url>/2023/11/13/simple-implementation-of-distributed-lock-based-on-Redis/</url>
-    <content><![CDATA[<p>在分布式应用中，并发访问资源需要谨慎考虑。比如读取和修改保存并不是一个原子操作，在并发时，就可能发生修改的结果被覆盖的问题。</p>
-<img src="/2023/11/13/simple-implementation-of-distributed-lock-based-on-Redis/Pasted%20image%2020231110180458.png" class="" title="分布式应用中的并发问题">
-
-<p>很多人都了解在必要的时候需要使用分布式锁来限制程序的并发执行，但是在具体的细节上，往往并不正确。</p>
-<h2 id="基于-Redis-的分布式锁简单实现"><a href="#基于-Redis-的分布式锁简单实现" class="headerlink" title="基于 Redis 的分布式锁简单实现"></a>基于 Redis 的分布式锁简单实现</h2><p>本质上要实现的目标就是在 Redis 中占坑，告诉后来者资源已经被锁定，放弃或者稍后重试。Redis 原生支持 set if not exists 的语义。</p>
-<figure class="highlight console"><table><tr><td class="code"><pre><span class="line"><span class="meta prompt_">&gt; </span><span class="language-bash">setnx lock:user1 <span class="literal">true</span></span></span><br><span class="line">OK</span><br><span class="line"></span><br><span class="line">... do something</span><br><span class="line"><span class="meta prompt_"></span></span><br><span class="line"><span class="meta prompt_">&gt; </span><span class="language-bash">del lock:user1</span></span><br><span class="line">(integer) 1</span><br></pre></td></tr></table></figure>
-
-<h3 id="死锁问题"><a href="#死锁问题" class="headerlink" title="死锁问题"></a>死锁问题</h3><h4 id="问题一：异常引发死锁-1"><a href="#问题一：异常引发死锁-1" class="headerlink" title="问题一：异常引发死锁 1"></a>问题一：异常引发死锁 1</h4><p>如果在处理过程中，程序出现异常，将导致 del 指令没有执行成功。锁无法释放，其他线程将无法再获取锁。</p>
-<img src="/2023/11/13/simple-implementation-of-distributed-lock-based-on-Redis/Pasted%20image%2020231110182254.png" class="" title="异常引发死锁 1">
-
-<h4 id="改进一：设置超时时间"><a href="#改进一：设置超时时间" class="headerlink" title="改进一：设置超时时间"></a>改进一：设置超时时间</h4><p>对 key 设置过期时间，如果在处理过程中，程序出现异常，导致 del 指令没有执行成功，设置的过期时间一到，key 将自动被删除，锁也就等于被释放了。</p>
-<figure class="highlight console"><table><tr><td class="code"><pre><span class="line"><span class="meta prompt_">&gt; </span><span class="language-bash">setnx lock:user1 <span class="literal">true</span></span></span><br><span class="line">OK</span><br><span class="line"><span class="meta prompt_">&gt; </span><span class="language-bash">expire lock:user1 5</span></span><br><span class="line"></span><br><span class="line">... do something</span><br><span class="line"><span class="meta prompt_"></span></span><br><span class="line"><span class="meta prompt_">&gt; </span><span class="language-bash">del lock:user1</span></span><br><span class="line">(integer) 1</span><br></pre></td></tr></table></figure>
-
-<h4 id="问题二：异常引发死锁-2"><a href="#问题二：异常引发死锁-2" class="headerlink" title="问题二：异常引发死锁 2"></a>问题二：异常引发死锁 2</h4><p>事实上，上述措施并没有彻底解决问题。如果在设置 key 的超时时间之前，程序出现异常，一切仍旧会发生。</p>
-<img src="/2023/11/13/simple-implementation-of-distributed-lock-based-on-Redis/Pasted%20image%2020231110190407.png" class="" title="异常引发死锁 2">
-
-<p>本质原因是 setnx 和 expire 两个指令不是一个原子操作。那么是否可以使用 Redis 的事务解决呢？不行。因为 expire 依赖于 setnx 的执行结果，如果 setnx 没有成功，expire 就不应该执行。</p>
-<h4 id="改进二：setnx-expire-的原子指令"><a href="#改进二：setnx-expire-的原子指令" class="headerlink" title="改进二：setnx + expire 的原子指令"></a>改进二：setnx + expire 的原子指令</h4><p>如果 setnx 和 expire 可以用一个原子指令实现就好了。</p>
-<img src="/2023/11/13/simple-implementation-of-distributed-lock-based-on-Redis/Pasted%20image%2020231110190442.png" class="" title="setnx + expire 原子指令">
-
-<h5 id="基于原生指令的实现"><a href="#基于原生指令的实现" class="headerlink" title="基于原生指令的实现"></a>基于原生指令的实现</h5><p>在 Redis 2.8 版本中，Redis 的作者加入 set 指令扩展参数，允许 setnx 和 expire 组合成一个原子指令。</p>
-<figure class="highlight console"><table><tr><td class="code"><pre><span class="line"><span class="meta prompt_">&gt; </span><span class="language-bash"><span class="built_in">set</span> lock:user1 <span class="literal">true</span> ex 5 nx</span></span><br><span class="line">OK</span><br><span class="line"></span><br><span class="line">... do something</span><br><span class="line"><span class="meta prompt_"></span></span><br><span class="line"><span class="meta prompt_">&gt; </span><span class="language-bash">del lock:user1</span></span><br><span class="line">(integer) 1</span><br></pre></td></tr></table></figure>
-
-<h5 id="基于-Lua-脚本的实现"><a href="#基于-Lua-脚本的实现" class="headerlink" title="基于 Lua 脚本的实现"></a>基于 Lua 脚本的实现</h5><p>除了使用原生的指令外，还可以使用 Lua 脚本，将多个 Redis 指令组合成一个原子指令。</p>
-<figure class="highlight lua"><table><tr><td class="code"><pre><span class="line"><span class="keyword">if</span> redis.call(<span class="string">&#x27;setnx&#x27;</span>, KEYS[<span class="number">1</span>], ARGV[<span class="number">1</span>]) == <span class="number">1</span> <span class="keyword">then</span></span><br><span class="line">  redis.call(<span class="string">&#x27;expire&#x27;</span>, KEYS[<span class="number">1</span>], ARGV[<span class="number">2</span>])</span><br><span class="line">  <span class="keyword">return</span> <span class="literal">true</span></span><br><span class="line"><span class="keyword">else</span></span><br><span class="line">  <span class="keyword">return</span> <span class="literal">false</span></span><br><span class="line"><span class="keyword">end</span></span><br></pre></td></tr></table></figure>
-
-<h3 id="超时问题"><a href="#超时问题" class="headerlink" title="超时问题"></a>超时问题</h3><p>基于 Redis 的分布式锁还会面临超时问题。如果在加锁和释放之间的处理逻辑过于耗时，以至于超出了 key 的过期时间，锁将在处理结束前被释放，就可能发生问题。</p>
-<img src="/2023/11/13/simple-implementation-of-distributed-lock-based-on-Redis/Pasted%20image%2020231110191738.png" class="" title="其他线程提前进入临界区">
-
-<h4 id="问题一：其他线程提前进入临界区"><a href="#问题一：其他线程提前进入临界区" class="headerlink" title="问题一：其他线程提前进入临界区"></a>问题一：其他线程提前进入临界区</h4><p>如果第一个线程因为处理逻辑过于耗时导致在处理结束前锁已经被释放，其他线程将可以提前获得锁，临界区的代码将不能保证严格串行执行。</p>
-<h4 id="问题二：错误释放其他线程的锁"><a href="#问题二：错误释放其他线程的锁" class="headerlink" title="问题二：错误释放其他线程的锁"></a>问题二：错误释放其他线程的锁</h4><p>如果在第二个线程获得锁后，第一个线程刚好处理逻辑结束去释放锁，将导致第二个线程的锁提前被释放，引发连锁问题。</p>
-<h4 id="改进一：不要用于较长时间的任务"><a href="#改进一：不要用于较长时间的任务" class="headerlink" title="改进一：不要用于较长时间的任务"></a>改进一：不要用于较长时间的任务</h4><p>与其说是改进，不如说是注意事项。如果真的出现问题，造成的数据错误可能需要人工介入解决。</p>
-<p>如果真的存在这样的业务场景，应考虑使用其他解决方案加以优化。</p>
-<h4 id="改进二：使用-watchdog-实现锁续期"><a href="#改进二：使用-watchdog-实现锁续期" class="headerlink" title="改进二：使用 watchdog 实现锁续期"></a>改进二：使用 watchdog 实现锁续期</h4><p>为 Redis 的 key 设置过期时间，其实是为了解决死锁问题而做出的兜底措施。可以为获得的锁设置定时任务定期地为锁续期，以避免锁被提前释放。</p>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">private</span> <span class="keyword">void</span> <span class="title function_">scheduleRenewal</span><span class="params">()</span> &#123;</span><br><span class="line">    <span class="type">String</span> <span class="variable">value</span> <span class="operator">=</span> lockValue.get();</span><br><span class="line">    ScheduledFuture&lt;?&gt; scheduledFuture = sScheduler.scheduleAtFixedRate(</span><br><span class="line">        () -&gt; <span class="built_in">this</span>.renewal(value), RENEWAL_INTERVAL, RENEWAL_INTERVAL, TimeUnit.MILLISECONDS</span><br><span class="line">    );</span><br><span class="line">    renewalTask.set(scheduledFuture);</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
-
-<p>但是这个方式仍然不能避免解锁失败时的其他线程的等待时间。</p>
-<h4 id="改进三：加锁时指定-tag"><a href="#改进三：加锁时指定-tag" class="headerlink" title="改进三：加锁时指定 tag"></a>改进三：加锁时指定 tag</h4><p>可以将 set 指令的 value 参数设置为一个随机数，释放锁时先匹配持有的 tag 是否和 value 一致，如果一致再删除 key，以此避免锁被其他线程错误释放。</p>
-<h5 id="基于原生指令的实现-1"><a href="#基于原生指令的实现-1" class="headerlink" title="基于原生指令的实现"></a>基于原生指令的实现</h5><figure class="highlight console"><table><tr><td class="code"><pre><span class="line">tag = random.nextint()</span><br><span class="line">if redis.set(key, tag, nx= True, ex=5):</span><br><span class="line">	do_something()</span><br><span class="line">	redis.delifequals(key, tag)</span><br></pre></td></tr></table></figure>
-
-<p>但是注意，Redis 并没有提供语义为 delete if equals 的原子指令，这样的话问题并不能被彻底解决。如果在第一个线程判断 tag 是否和 value 相等之后，第二个线程刚好获得了锁，然后第一个线程因为匹配成功执行删除 key 操作，仍然将导致第二个线程获得的锁被第一个线程错误释放。</p>
-<img src="/2023/11/13/simple-implementation-of-distributed-lock-based-on-Redis/Pasted%20image%2020231110193919.png" class="" title="错误释放其他线程的锁">
-
-<h5 id="基于-Lua-脚本的实现-1"><a href="#基于-Lua-脚本的实现-1" class="headerlink" title="基于 Lua 脚本的实现"></a>基于 Lua 脚本的实现</h5><figure class="highlight lua"><table><tr><td class="code"><pre><span class="line"><span class="keyword">if</span> redis.call(<span class="string">&quot;get&quot;</span>, KEYS[<span class="number">1</span>]) == ARGV[<span class="number">1</span>] <span class="keyword">then</span></span><br><span class="line">  <span class="keyword">return</span> redis.call(<span class="string">&quot;del&quot;</span>, KEYS[<span class="number">1</span>])</span><br><span class="line"><span class="keyword">else</span></span><br><span class="line">  <span class="keyword">return</span> <span class="number">0</span></span><br><span class="line"><span class="keyword">end</span></span><br></pre></td></tr></table></figure>
-
-<h3 id="可重入性"><a href="#可重入性" class="headerlink" title="可重入性"></a>可重入性</h3><p>可重入性是指线程在已经持有锁的情况下再次请求加锁，如果一个锁支持同一个线程多次加锁，那么就称这个锁是可重入的，类似 Java 的 ReentrantLock。</p>
-<h4 id="使用-ThreadLocal-实现锁计数"><a href="#使用-ThreadLocal-实现锁计数" class="headerlink" title="使用 ThreadLocal 实现锁计数"></a>使用 ThreadLocal 实现锁计数</h4><p>Redis 分布式锁如果要支持可重入，可以使用线程的 ThreadLocal 变量存储当前持有的锁计数。但是在多次获得锁后，过期时间并没有得到延长，后续获得锁后持有锁的时间其实比设置的时间更短。</p>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">private</span> ThreadLocal&lt;Integer&gt; lockCount = ThreadLocal.withInitial(() -&gt; <span class="number">0</span>);</span><br><span class="line"></span><br><span class="line"><span class="keyword">public</span> <span class="type">boolean</span> <span class="title function_">tryLock</span><span class="params">()</span> &#123;  </span><br><span class="line">    <span class="type">Integer</span> <span class="variable">count</span> <span class="operator">=</span> lockCount.get();  </span><br><span class="line">    <span class="keyword">if</span> (count != <span class="literal">null</span> &amp;&amp; count &gt; <span class="number">0</span>) &#123;  </span><br><span class="line">        lockCount.set(count + <span class="number">1</span>);   </span><br><span class="line">        <span class="keyword">return</span> <span class="literal">true</span>;    </span><br><span class="line">    &#125;  </span><br><span class="line">    <span class="type">String</span> <span class="variable">result</span> <span class="operator">=</span> commands.set(lockKey, lockValue.get(), SetArgs.Builder.nx().px(RedisLockManager.LOCK_EXPIRE));  </span><br><span class="line">    <span class="keyword">if</span> (<span class="string">&quot;OK&quot;</span>.equals(result)) &#123;  </span><br><span class="line">        lockCount.set(<span class="number">1</span>);  </span><br><span class="line">        scheduleRenewal();  </span><br><span class="line">        <span class="keyword">return</span> <span class="literal">true</span>;    </span><br><span class="line">    &#125;  </span><br><span class="line">    <span class="keyword">return</span> <span class="literal">false</span>;  </span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
-
-<h4 id="使用-Redis-hash-实现锁计数"><a href="#使用-Redis-hash-实现锁计数" class="headerlink" title="使用 Redis hash 实现锁计数"></a>使用 Redis hash 实现锁计数</h4><p>还可以使用 Redis 的 hash 数据结构实现锁计数，支持重新获取锁后重置过期时间。</p>
-<figure class="highlight lua"><table><tr><td class="code"><pre><span class="line"><span class="keyword">if</span> (redis.call(<span class="string">&#x27;exists&#x27;</span>, KEYS[<span class="number">1</span>]) == <span class="number">0</span>) <span class="keyword">then</span> </span><br><span class="line">	redis.call(<span class="string">&#x27;hset&#x27;</span>, KEYS[<span class="number">1</span>], ARGV[<span class="number">2</span>], <span class="number">1</span>);</span><br><span class="line">	redis.call(<span class="string">&#x27;pexpire&#x27;</span>, KEYS[<span class="number">1</span>], ARGV[<span class="number">1</span>]);</span><br><span class="line">    <span class="keyword">return</span> <span class="literal">nil</span>;</span><br><span class="line">    <span class="keyword">end</span>;</span><br><span class="line"><span class="keyword">if</span> (redis.call(<span class="string">&#x27;hexists&#x27;</span>, KEYS[<span class="number">1</span>], ARGV[<span class="number">2</span>]) == <span class="number">1</span>) <span class="keyword">then</span></span><br><span class="line">	redis.call(<span class="string">&#x27;hincrby&#x27;</span>, KEYS[<span class="number">1</span>], ARGV[<span class="number">2</span>], <span class="number">1</span>);</span><br><span class="line">	redis.call(<span class="string">&#x27;pexpire&#x27;</span>, KEYS[<span class="number">1</span>], ARGV[<span class="number">1</span>]);</span><br><span class="line">    <span class="keyword">return</span> <span class="literal">nil</span>;</span><br><span class="line"><span class="keyword">return</span> redis.call(<span class="string">&#x27;pttl&#x27;</span>, KEYS[<span class="number">1</span>]);</span><br></pre></td></tr></table></figure>
+<h4 id="使用-Redis-hash-实现锁计数"><a href="#使用-Redis-hash-实现锁计数" class="headerlink" title="使用 Redis hash 实现锁计数"></a>使用 Redis hash 实现锁计数</h4><p>还可以使用 Redis 的 hash 数据结构实现锁计数，支持重新获取锁后重置过期时间。</p>
+<figure class="highlight lua"><table><tr><td class="code"><pre><span class="line"><span class="keyword">if</span> (redis.call(<span class="string">&#x27;exists&#x27;</span>, KEYS[<span class="number">1</span>]) == <span class="number">0</span>) <span class="keyword">then</span> </span><br><span class="line">	redis.call(<span class="string">&#x27;hset&#x27;</span>, KEYS[<span class="number">1</span>], ARGV[<span class="number">2</span>], <span class="number">1</span>);</span><br><span class="line">	redis.call(<span class="string">&#x27;pexpire&#x27;</span>, KEYS[<span class="number">1</span>], ARGV[<span class="number">1</span>]);</span><br><span class="line">    <span class="keyword">return</span> <span class="literal">nil</span>;</span><br><span class="line">    <span class="keyword">end</span>;</span><br><span class="line"><span class="keyword">if</span> (redis.call(<span class="string">&#x27;hexists&#x27;</span>, KEYS[<span class="number">1</span>], ARGV[<span class="number">2</span>]) == <span class="number">1</span>) <span class="keyword">then</span></span><br><span class="line">	redis.call(<span class="string">&#x27;hincrby&#x27;</span>, KEYS[<span class="number">1</span>], ARGV[<span class="number">2</span>], <span class="number">1</span>);</span><br><span class="line">	redis.call(<span class="string">&#x27;pexpire&#x27;</span>, KEYS[<span class="number">1</span>], ARGV[<span class="number">1</span>]);</span><br><span class="line">    <span class="keyword">return</span> <span class="literal">nil</span>;</span><br><span class="line"><span class="keyword">return</span> redis.call(<span class="string">&#x27;pttl&#x27;</span>, KEYS[<span class="number">1</span>]);</span><br></pre></td></tr></table></figure>
 
 <p>书的作者<strong>不推荐使用可重入锁</strong>，他提出可重入锁会加重客户端的复杂度，如果在编写代码时注意在逻辑结构上进行调整，完全可以避免使用可重入锁。</p>
 <h2 id="代码实现"><a href="#代码实现" class="headerlink" title="代码实现"></a>代码实现</h2><p><a href="https://github.com/moralok/redis-lock">redis-lock</a></p>
@@ -3385,438 +3333,322 @@
       </tags>
   </entry>
   <entry>
-    <title>Spring @Configuration 注解的源码分析</title>
-    <url>/2023/11/23/source-code-analysis-of-Spring-Configuration-annotation/</url>
-    <content><![CDATA[<p><code>Configuration</code> 注解是 <code>Spring</code> 中常用的注解，在一般的应用场景中，它用于标识一个类作为配置类，搭配 <code>Bean</code> 注解将创建的 <code>bean</code> 交给 <code>Spring</code> 容器管理。神奇的是，被 <code>Bean</code> 注解标注的方法，只会被真正调用一次。这种方法调用被拦截的情况很容易让人联想到代理，如果你在 <code>Debug</code> 时注意过配置类的实例，你会发现配置类的 <code>Class</code> 名称中携带 <code>EnhancerBySpringCGLIB</code>。本文将从源码角度，分析 <code>Configuration</code> 注解是如何工作的。</p>
-<span id="more"></span>
-
-<h2 id="测试用例"><a href="#测试用例" class="headerlink" title="测试用例"></a>测试用例</h2><ul>
-<li>配置类<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="meta">@Configuration</span></span><br><span class="line"><span class="keyword">public</span> <span class="keyword">class</span> <span class="title class_">BeanConfig</span> &#123;</span><br><span class="line"></span><br><span class="line">    <span class="meta">@Bean</span></span><br><span class="line">    <span class="keyword">public</span> Person <span class="title function_">lisi</span><span class="params">()</span> &#123;</span><br><span class="line">        <span class="keyword">return</span> <span class="keyword">new</span> <span class="title class_">Person</span>(<span class="string">&quot;lisi&quot;</span>, <span class="number">20</span>);</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="meta">@Bean(value = &quot;customName&quot;)</span></span><br><span class="line">    <span class="keyword">public</span> Person <span class="title function_">person</span><span class="params">()</span> &#123;</span><br><span class="line">        <span class="comment">// 测试 lisi() 在配置类拥有注解 @Configuration 时只会真正执行一次</span></span><br><span class="line">        lisi();</span><br><span class="line">        <span class="keyword">return</span> <span class="keyword">new</span> <span class="title class_">Person</span>(<span class="string">&quot;wangwu&quot;</span>, <span class="number">30</span>);</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure></li>
-<li>测试类<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="meta">@Test</span></span><br><span class="line"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title function_">annotationConfigTest</span><span class="params">()</span> &#123;</span><br><span class="line">    <span class="type">ApplicationContext</span> <span class="variable">ac</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">AnnotationConfigApplicationContext</span>(BeanConfig.class);</span><br><span class="line">    <span class="type">BeanConfig</span> <span class="variable">beanConfig</span> <span class="operator">=</span> (BeanConfig) ac.getBean(<span class="string">&quot;beanConfig&quot;</span>);</span><br><span class="line">    <span class="comment">// 即使通过 beanConfig 调用，也不会执行第二次</span></span><br><span class="line">    <span class="type">Person</span> <span class="variable">lisi</span> <span class="operator">=</span> beanConfig.lisi();</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure></li>
-</ul>
-<h2 id="解析配置类"><a href="#解析配置类" class="headerlink" title="解析配置类"></a>解析配置类</h2><h3 id="什么是配置类？"><a href="#什么是配置类？" class="headerlink" title="什么是配置类？"></a>什么是配置类？</h3><p>通常情况下，我们称被 <code>Configuration</code> 注解标注的类为配置类。事实上，配置类的范围比这个定义稍微广泛一些，可以划分为全配置类和精简配置类。在解析配置类时，我们再进一步说明。</p>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="type">ApplicationContext</span> <span class="variable">ac</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">AnnotationConfigApplicationContext</span>(BeanConfig.class);</span><br><span class="line"></span><br><span class="line"><span class="keyword">public</span> <span class="title function_">AnnotationConfigApplicationContext</span><span class="params">(Class&lt;?&gt;... annotatedClasses)</span> &#123;</span><br><span class="line">    <span class="built_in">this</span>();</span><br><span class="line">    <span class="comment">// 注册类，几乎可以说无条件地注册 annotatedClasses 的 bean 定义</span></span><br><span class="line">    register(annotatedClasses);</span><br><span class="line">    refresh();</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+    <title>如何为终端、docker 和容器设置代理</title>
+    <url>/2023/06/13/how-to-configure-proxy-for-terminal-docker-and-container/</url>
+    <content><![CDATA[<p>在 <a href="/2023/05/27/how-to-install-clash-on-ubuntu/" title="在 Ubuntu 上安装 Clash">Ubuntu 上安装 Clash</a> 后，Clash 通过监听本地的 7890 端口，提供代理服务。但是不同程序设置代理的方式不尽相同，并不是启动了 Clash 以及在某一处设置后，整个系统发出的 HTTP 请求都能经过代理。本文将介绍如何为终端、docker 和容器添加代理。</p>
+<h2 id="为终端设置代理"><a href="#为终端设置代理" class="headerlink" title="为终端设置代理"></a>为终端设置代理</h2><p>有时候，我们需要在终端通过执行命令的方式访问网络和下载资源，比如使用 <code>wget</code> 和 <code>curl</code>。</p>
+<h3 id="设置-Shell-环境变量"><a href="#设置-Shell-环境变量" class="headerlink" title="设置 Shell 环境变量"></a>设置 Shell 环境变量</h3><p>这一类软件都是可以通过为 Shell 设置环境变量的方式来设置代理，涉及到的环境变量有 <code>http_proxy</code>、<code>https_proxy</code> 和 <code>no_proxy</code>。<br>仅为当前会话设置，执行命令：</p>
+<figure class="highlight shell"><table><tr><td class="code"><pre><span class="line">export http_proxy=http://proxyAddress:port</span><br><span class="line">export https_proxy=http://proxyAddress:port</span><br><span class="line">export no_proxy=localhost,127.0.0.1</span><br></pre></td></tr></table></figure>
+<p>永久设置代理，在设置 Shell 环境变量的脚本中（不同 Shell 的配置文件不同，比如 <code>~/.bashrc</code> 或 <code>~/.zshrc</code>）添加：</p>
+<figure class="highlight shell"><table><tr><td class="code"><pre><span class="line">export http_proxy=http://proxyAddress:port</span><br><span class="line">export https_proxy=http://proxyAddress:port</span><br><span class="line">export no_proxy=localhost,127.0.0.1</span><br></pre></td></tr></table></figure>
+<p>重新启动一个会话或者执行命令 <code>source ~/.bashrc</code> 使其在当前会话立即生效。</p>
+<h3 id="修改-wget-配置文件"><a href="#修改-wget-配置文件" class="headerlink" title="修改 wget 配置文件"></a>修改 wget 配置文件</h3><p>在搜索过程中发现还可以在 <code>wget</code> 的配置文件 <code>~/.wgetrc</code> 中添加:</p>
+<figure class="highlight shell"><table><tr><td class="code"><pre><span class="line">use_proxy = on</span><br><span class="line"></span><br><span class="line">http_proxy = http://proxyAddress:port</span><br><span class="line">https_proxy = http://proxyAddress:port</span><br></pre></td></tr></table></figure>
 
-<p>本文不详细介绍配置类本身如何注册到 <code>BeanFactory</code> 中。当 <code>BeanConfig</code> 被传递给 <code>AnnotationConfigApplicationContext</code>，自身会先被解析为 <code>BeanDefinition</code> 注册到 <code>beanFactory</code> 中。有两点需要注意：</p>
-<ol>
-<li><code>annotatedClasses</code> 可以传入多个，意味着一开始<strong>静态指定的配置类</strong>可以有多个。</li>
-<li><code>annotatedClasses</code> 除了在命名上提示用户应传入被注解的类外，<code>register(annotatedClasses)</code> 实际上只是将它们视作普通的 <code>Bean</code> 注册到 <code>beanFactory</code> 中。它们是从外界传入的**首批 <code>BeanDefinition</code>**。</li>
-</ol>
-<p>之后 <code>Spring</code> 进入 <code>refresh</code> 流程。使用 <code>IDEA Debug</code> 观察此时的 <code>beanDefinitionMap</code>，除了 <code>beanConfig</code> 外，<code>AnnotationConfigApplicationContext</code> 在创建时，已经自动注册了 <code>6</code> 个 <code>bean</code> 定义，其中一个就是我们今天的主角 <code>org.springframework.context.annotation.internalConfigurationAnnotationProcessor -&gt; org.springframework.context.annotation.ConfigurationClassPostProcessor</code>。显而易见，此时配置类还未被处理得到新的 <code>bean</code> 定义。</p>
-<div style="width:70%;margin:auto"><img src="/2023/11/23/source-code-analysis-of-Spring-Configuration-annotation/Snipaste_2023-11-24_15-26-08.png" class="" title="AnnotationConfigApplicationContext 刷新前的 bean 定义"></div>
+<h2 id="为-docker-设置代理"><a href="#为-docker-设置代理" class="headerlink" title="为 docker 设置代理"></a>为 docker 设置代理</h2><p>如果你以为为终端设置代理后 docker 就会使用代理，那你就错了。在从官方的镜像仓库 pull 镜像反复出错后并收到类似 <code>Error response from daemon: Get &quot;https://registry-1.docker.io/v2/&quot;: read tcp 192.168.3.140:59460-&gt;44.205.64.79:443: read: connection reset by peer</code> 这样的报错信息后，我才开始怀疑我并没有真正给 docker 设置好代理。<br>在执行 <code>docker pull</code> 命令时，实际上命令是由守护进程 <code>docker daemon</code> 执行的。</p>
+<h3 id="通过-systemd-设置"><a href="#通过-systemd-设置" class="headerlink" title="通过 systemd 设置"></a>通过 systemd 设置</h3><p>如果你的 <code>docker daemon</code> 是通过 <code>systemd</code> 管理的，那么你可以通过设置 <code>docker.service</code> 服务的环境变量来设置代理。<br>执行命令查看 <code>docker.service</code> 信息，得知配置文件位置 <code>/lib/systemd/system/docker.service</code>。</p>
+<figure class="highlight shell"><table><tr><td class="code"><pre><span class="line"><span class="meta prompt_">~$ </span><span class="language-bash">systemctl status docker.service</span> </span><br><span class="line">● docker.service - Docker Application Container Engine</span><br><span class="line">     Loaded: loaded (/lib/systemd/system/docker.service; enabled; vendor preset: enabled)</span><br><span class="line">     Active: active (running) since Tue 2023-06-13 00:52:54 CST; 22h ago</span><br><span class="line">TriggeredBy: ● docker.socket</span><br><span class="line">       Docs: https://docs.docker.com</span><br><span class="line">   Main PID: 387690 (dockerd)</span><br><span class="line">      Tasks: 139</span><br><span class="line">     Memory: 89.6M</span><br><span class="line">        CPU: 1min 26.512s</span><br><span class="line">     CGroup: /system.slice/docker.service</span><br></pre></td></tr></table></figure>
+<p>在 <code>docker.service</code> 的 <code>[Service]</code> 模块添加：</p>
+<figure class="highlight shell"><table><tr><td class="code"><pre><span class="line">Environment=HTTP_PROXY=http://proxyAddress:port</span><br><span class="line">Environment=HTTPS_PROXY=http://proxyAddress:port</span><br><span class="line">Environment=NO_PROXY=localhost,127.0.0.1</span><br></pre></td></tr></table></figure>
+<p>重新加载配置文件并重启服务：</p>
+<figure class="highlight shell"><table><tr><td class="code"><pre><span class="line">systemctl daemon-reload</span><br><span class="line">systemctl restart docker.service</span><br></pre></td></tr></table></figure>
 
-<h3 id="配置类后处理器-ConfigurationClassPostProcessor"><a href="#配置类后处理器-ConfigurationClassPostProcessor" class="headerlink" title="配置类后处理器 ConfigurationClassPostProcessor"></a>配置类后处理器 ConfigurationClassPostProcessor</h3><p>配置类后处理器 <code>ConfigurationClassPostProcessor</code> 实现了接口 <code>BeanDefinitionRegistryPostProcessor</code>，也因此同时实现了接口 <code>BeanFactoryPostProcessor</code>。在<a href="/2023/08/04/Spring-application-context-refresh-process/" title="Spring 应用 context 刷新流程">Spring 应用 context 刷新流程</a>中，我们介绍过这两个接口，它们作为工厂后处理器，被用于 <code>refresh</code> 过程的<strong>调用工厂后处理器阶段</strong>（<code>invokeBeanFactoryPostProcessors(beanFactory)</code>）。工厂后处理器的作用，一言以蔽之，允许自定义修改应用上下文中的 bean 定义。</p>
-<p>配置类后处理器 <code>ConfigurationClassPostProcessor</code> 的具体作用可以概括为两点：</p>
-<ol>
-<li>解析配置类中配置的 <code>Bean</code>，将它们的 <code>bean</code> 定义注册到 <code>BeanFactory</code> 中。</li>
-<li>（如有必要）增强配置类</li>
-</ol>
-<h3 id="处理配置类的核心方法-processConfigBeanDefinitions"><a href="#处理配置类的核心方法-processConfigBeanDefinitions" class="headerlink" title="处理配置类的核心方法 processConfigBeanDefinitions"></a>处理配置类的核心方法 processConfigBeanDefinitions</h3><p>根据之前的介绍，进入 <code>invokeBeanFactoryPostProcessors(beanFactory)</code>，<code>ConfigurationClassPostProcessor</code> 会先作为 <code>BeanDefinitionRegistryPostProcessor</code> 被调用。</p>
+<h3 id="修改-dockerd-配置文件"><a href="#修改-dockerd-配置文件" class="headerlink" title="修改 dockerd 配置文件"></a>修改 dockerd 配置文件</h3><p>还可以修改 <code>dockerd</code> 配置文件，添加：</p>
+<figure class="highlight shell"><table><tr><td class="code"><pre><span class="line">export http_proxy=&quot;http://proxyAddress:port&quot;</span><br></pre></td></tr></table></figure>
+<p>然后重启 <code>docker daemon</code> 即可。</p>
 <blockquote>
-<p>个人的理解是，先将 <code>BeanFactory</code> 视作 <code>BeanDefinitionRegistry</code> 注册好 <code>BeanDefinition</code>，再视作 <code>BeanFactory</code> 进行处理，有点预备好原材料再统一处理的意思。</p>
+<p>国内的镜像仓库在绝大多数时候都可以满足条件，但是存在个别镜像同步不及时的情况，如果使用 latest 标签拉取到的镜像并非近期的镜像，因此有时候需要直接从官方镜像仓库拉取镜像。</p>
 </blockquote>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="meta">@Override</span></span><br><span class="line"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title function_">postProcessBeanDefinitionRegistry</span><span class="params">(BeanDefinitionRegistry registry)</span> &#123;</span><br><span class="line">    <span class="comment">// ...</span></span><br><span class="line">    <span class="comment">// 处理配置的 BeanDefinition</span></span><br><span class="line">    processConfigBeanDefinitions(registry);</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
-
+<h2 id="为-docker-容器设置代理"><a href="#为-docker-容器设置代理" class="headerlink" title="为 docker 容器设置代理"></a>为 docker 容器设置代理</h2><p>为 <code>docker daemon</code> 进程设置代理和为 docker 容器设置代理是有区别的。比如使用 docker 启动媒体服务器 jellyfin 后，jellyfin 的刮削功能就需要代理才能正常使用，这时候不要因为在很多地方设置过代理就以为容器内部已经在使用代理了。</p>
+<h3 id="修改配置文件"><a href="#修改配置文件" class="headerlink" title="修改配置文件"></a>修改配置文件</h3><p>创建或修改 <code>~/.docker/config.json</code>，添加：</p>
+<figure class="highlight json"><table><tr><td class="code"><pre><span class="line"><span class="punctuation">&#123;</span></span><br><span class="line">    <span class="attr">&quot;proxies&quot;</span><span class="punctuation">:</span></span><br><span class="line">    <span class="punctuation">&#123;</span></span><br><span class="line">        <span class="attr">&quot;default&quot;</span><span class="punctuation">:</span></span><br><span class="line">        <span class="punctuation">&#123;</span></span><br><span class="line">            <span class="attr">&quot;httpProxy&quot;</span><span class="punctuation">:</span> <span class="string">&quot;http://proxyAddress:port&quot;</span><span class="punctuation">,</span></span><br><span class="line">            <span class="attr">&quot;httpsProxy&quot;</span><span class="punctuation">:</span> <span class="string">&quot;http://proxyAddress:port&quot;</span><span class="punctuation">,</span></span><br><span class="line">            <span class="attr">&quot;noProxy&quot;</span><span class="punctuation">:</span> <span class="string">&quot;localhost,127.0.0.1&quot;</span></span><br><span class="line">        <span class="punctuation">&#125;</span></span><br><span class="line">    <span class="punctuation">&#125;</span></span><br><span class="line"><span class="punctuation">&#125;</span></span><br></pre></td></tr></table></figure>
+<p>此后创建的新容器，会自动设置环境变量来使用代理。</p>
+<h3 id="为指定容器添加环境变量"><a href="#为指定容器添加环境变量" class="headerlink" title="为指定容器添加环境变量"></a>为指定容器添加环境变量</h3><p>在启动容器时使用 <code>-e</code> 手动注入环境变量 <code>http_proxy</code>。这意味着进入容器使用 <code>export</code> 设置环境变量的方式也是可行的。</p>
 <blockquote>
-<p>核心方法 <code>processConfigBeanDefinitions(registry)</code> 冗长，个人建议无需过度关注细节（但同时个人感受是反复阅读和 <code>Debug</code> 确实有益于加深理解，看个人时间和精力）。</p>
+<p>注意：如果代理是使用宿主机的代理，当网络为 <code>bridge</code> 模式，proxyAddress 需要填写宿主机的 IP；如果使用 <code>host</code> 模式，proxyAddress 可以填写 127.0.0.1。</p>
 </blockquote>
-<p>基于配置类的 <code>BeanDefinition Registry</code>（也就是 <code>BeanFactory</code>），获取配置类，构建和校验配置模型：</p>
+<h2 id="总结"><a href="#总结" class="headerlink" title="总结"></a>总结</h2><p>不要因为在很多地方设置过代理，就想当然地以为当前的访问也是经过代理的。每个软件设置代理的方式不尽相同，但是大体上可以归结为：</p>
 <ol>
-<li>从 <code>BeanDefinition Registry</code>（即 <code>BeanFactory</code>）中查找配置类。</li>
-<li>解析配置类得到<strong>配置模型</strong>，从模型中读取 <code>BeanDefinitions</code> 注册到 <code>BeanDefinition Registry</code>。</li>
-<li>新的 <code>BeanDefinitions</code> 可能有新的配置类，回到 <code>1</code> 再来一遍。重复循环直到不再引入新的配置类。</li>
+<li>使用系统的环境变量</li>
+<li>修改软件的配置文件</li>
+<li>执行时注入参数</li>
 </ol>
-<p>以本文示例进行说明，静态添加的配置类只有 <code>BeanConfig</code>，假如 <code>BeanConfig</code> 不仅被 <code>Configuration</code> 注解标注，还被 <code>ComponentScan</code> 注解标注，并且刚好 <code>Spring</code> 通过扫描获得并添加了新的配置类，那么新的配置类就需要继续被解析。</p>
+<p>举一反三，像 <code>apt</code> 和 <code>git</code> 这类软件也是有其设置代理的方法。当你的代理稳定但是相应的访问失败时，大胆假设你的代理没有设置成功。要理清楚，当前的访问是谁发起的，才能正确地使用关键词搜索到正确的设置方式。</p>
 <blockquote>
-<p>应正视<strong>配置模型</strong>这个概念，它可以理解为配置类到 <code>BeanDefinitions</code> 的中间产物。最初我先入为主，带着<code>解析得到 BeanDefinitions</code> 这样“一阶段”完成的观念，非常不理解 <code>processConfigBeanDefinitions</code> 方法上 <code>Build and validate a configuration model based on the registry of Configuration classes</code> 这句注释。先行强调注意，<strong>处理配置类得到 <code>bean</code> 定义分为“两阶段”，解析配置类得到配置模型，从配置模型中读取 <code>bean</code> 定义</strong>。</p>
+<p>原本我在 docker 相关的使用中，有关代理的设置方式是通过修改配置文件，实现永久、全局的代理配置。但是在后续的使用中，发现代理在一些场景（比如使用 cloudflare tunnel）中会引起不易排查的问题，决定采用临时、局部的配置方式。</p>
 </blockquote>
-<div style="width:60%;margin:auto"><img src="/2023/11/23/source-code-analysis-of-Spring-Configuration-annotation/Pasted%20image%2020231127205117.png" class="" title="处理配置类的过程"></div>
-
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title function_">processConfigBeanDefinitions</span><span class="params">(BeanDefinitionRegistry registry)</span> &#123;</span><br><span class="line">    List&lt;BeanDefinitionHolder&gt; configCandidates = <span class="keyword">new</span> <span class="title class_">ArrayList</span>&lt;BeanDefinitionHolder&gt;();</span><br><span class="line">    <span class="comment">// 刚开始，获取全部的 BeanDefinitions 作为候选</span></span><br><span class="line">    String[] candidateNames = registry.getBeanDefinitionNames();</span><br><span class="line"></span><br><span class="line">    <span class="keyword">for</span> (String beanName : candidateNames) &#123;</span><br><span class="line">        <span class="type">BeanDefinition</span> <span class="variable">beanDef</span> <span class="operator">=</span> registry.getBeanDefinition(beanName);</span><br><span class="line">        <span class="keyword">if</span> (ConfigurationClassUtils.isFullConfigurationClass(beanDef) ||</span><br><span class="line">                ConfigurationClassUtils.isLiteConfigurationClass(beanDef)) &#123;</span><br><span class="line">            <span class="comment">// 根据 beanDef 的 attributes 判断是 Full 还是 Lite 的配置类</span></span><br><span class="line">            <span class="comment">// 已经处理过的配置类，会在 attributes 中添加标识</span></span><br><span class="line">            <span class="keyword">if</span> (logger.isDebugEnabled()) &#123;</span><br><span class="line">                logger.debug(<span class="string">&quot;Bean definition has already been processed as a configuration class: &quot;</span> + beanDef);</span><br><span class="line">            &#125;</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="keyword">else</span> <span class="keyword">if</span> (ConfigurationClassUtils.checkConfigurationClassCandidate(beanDef, <span class="built_in">this</span>.metadataReaderFactory)) &#123;</span><br><span class="line">            <span class="comment">// 未处理过的候选者，检查是否是配置类。</span></span><br><span class="line">            <span class="comment">// configCandidates 的命名让人有些困惑，个人认为这里指代的就是配置类</span></span><br><span class="line">            configCandidates.add(<span class="keyword">new</span> <span class="title class_">BeanDefinitionHolder</span>(beanDef, beanName));</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// Return immediately if no @Configuration classes were found</span></span><br><span class="line">    <span class="comment">// 和注释略有不符，配置类的判定没有这么单一，不仅限于 @Configuration 注解的 Full 配置类</span></span><br><span class="line">    <span class="keyword">if</span> (configCandidates.isEmpty()) &#123;</span><br><span class="line">        <span class="keyword">return</span>;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 根据 attributes 中的 order 排序（来源于 @Order 注解，可能不存在）</span></span><br><span class="line">    Collections.sort(configCandidates, <span class="keyword">new</span> <span class="title class_">Comparator</span>&lt;BeanDefinitionHolder&gt;() &#123;</span><br><span class="line">        <span class="meta">@Override</span></span><br><span class="line">        <span class="keyword">public</span> <span class="type">int</span> <span class="title function_">compare</span><span class="params">(BeanDefinitionHolder bd1, BeanDefinitionHolder bd2)</span> &#123;</span><br><span class="line">            <span class="type">int</span> <span class="variable">i1</span> <span class="operator">=</span> ConfigurationClassUtils.getOrder(bd1.getBeanDefinition());</span><br><span class="line">            <span class="type">int</span> <span class="variable">i2</span> <span class="operator">=</span> ConfigurationClassUtils.getOrder(bd2.getBeanDefinition());</span><br><span class="line">            <span class="keyword">return</span> (i1 &lt; i2) ? -<span class="number">1</span> : (i1 &gt; i2) ? <span class="number">1</span> : <span class="number">0</span>;</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;);</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 检测应用上下文中是否配置了自定义 bean 名称生成策略</span></span><br><span class="line">    <span class="type">SingletonBeanRegistry</span> <span class="variable">sbr</span> <span class="operator">=</span> <span class="literal">null</span>;</span><br><span class="line">    <span class="keyword">if</span> (registry <span class="keyword">instanceof</span> SingletonBeanRegistry) &#123;</span><br><span class="line">        sbr = (SingletonBeanRegistry) registry;</span><br><span class="line">        <span class="keyword">if</span> (!<span class="built_in">this</span>.localBeanNameGeneratorSet &amp;&amp; sbr.containsSingleton(CONFIGURATION_BEAN_NAME_GENERATOR)) &#123;</span><br><span class="line">            <span class="comment">// 如果 localBeanNameGenerator 未设置，且 SingletonBeanRegistry 中存在，就获取并使用</span></span><br><span class="line">            <span class="type">BeanNameGenerator</span> <span class="variable">generator</span> <span class="operator">=</span> (BeanNameGenerator) sbr.getSingleton(CONFIGURATION_BEAN_NAME_GENERATOR);</span><br><span class="line">            <span class="built_in">this</span>.componentScanBeanNameGenerator = generator;</span><br><span class="line">            <span class="built_in">this</span>.importBeanNameGenerator = generator;</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 创建 ConfigurationClassParser，解析每一个配置类（不限于 Full 类型）</span></span><br><span class="line">    <span class="type">ConfigurationClassParser</span> <span class="variable">parser</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">ConfigurationClassParser</span>(</span><br><span class="line">            <span class="built_in">this</span>.metadataReaderFactory, <span class="built_in">this</span>.problemReporter, <span class="built_in">this</span>.environment,</span><br><span class="line">            <span class="built_in">this</span>.resourceLoader, <span class="built_in">this</span>.componentScanBeanNameGenerator, registry);</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 配置类候选</span></span><br><span class="line">    Set&lt;BeanDefinitionHolder&gt; candidates = <span class="keyword">new</span> <span class="title class_">LinkedHashSet</span>&lt;BeanDefinitionHolder&gt;(configCandidates);</span><br><span class="line">    <span class="comment">// 处理过的配置模型，已经被读取过 Bean 定义</span></span><br><span class="line">    <span class="comment">// 个人感觉命名为 alreadyRead 更为准确</span></span><br><span class="line">    Set&lt;ConfigurationClass&gt; alreadyParsed = <span class="keyword">new</span> <span class="title class_">HashSet</span>&lt;ConfigurationClass&gt;(configCandidates.size());</span><br><span class="line">    <span class="keyword">do</span> &#123;</span><br><span class="line">        <span class="comment">// 解析</span></span><br><span class="line">        parser.parse(candidates);</span><br><span class="line">        <span class="comment">// 校验</span></span><br><span class="line">        parser.validate();</span><br><span class="line"></span><br><span class="line">        <span class="comment">// 从 parser 中获取 ConfigurationClass，这就是配置模型（忍不住吐槽一下这个命名和配置类好容易搞混）</span></span><br><span class="line">        Set&lt;ConfigurationClass&gt; configClasses = <span class="keyword">new</span> <span class="title class_">LinkedHashSet</span>&lt;ConfigurationClass&gt;(parser.getConfigurationClasses());</span><br><span class="line">        <span class="comment">// 排除已经读取过 Bean 定义的 ConfigurationClass</span></span><br><span class="line">        configClasses.removeAll(alreadyParsed);</span><br><span class="line"></span><br><span class="line">        <span class="comment">// Read the model and create bean definitions based on its content</span></span><br><span class="line">        <span class="comment">// 读取模型并根据它的内容创建 BeanDefinitions</span></span><br><span class="line">        <span class="keyword">if</span> (<span class="built_in">this</span>.reader == <span class="literal">null</span>) &#123;</span><br><span class="line">            <span class="built_in">this</span>.reader = <span class="keyword">new</span> <span class="title class_">ConfigurationClassBeanDefinitionReader</span>(</span><br><span class="line">                    registry, <span class="built_in">this</span>.sourceExtractor, <span class="built_in">this</span>.resourceLoader, <span class="built_in">this</span>.environment,</span><br><span class="line">                    <span class="built_in">this</span>.importBeanNameGenerator, parser.getImportRegistry());</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="comment">// 加载（读取并注册） BeanDefinitions</span></span><br><span class="line">        <span class="built_in">this</span>.reader.loadBeanDefinitions(configClasses);</span><br><span class="line">        <span class="comment">// 添加到已经读取过的配置模型集合中（上面的 configClasses.removeAll(alreadyParsed) 造成的干扰好大）</span></span><br><span class="line">        alreadyParsed.addAll(configClasses);</span><br><span class="line"></span><br><span class="line">        <span class="comment">// 清空这一轮处理的配置类集合</span></span><br><span class="line">        candidates.clear();</span><br><span class="line">        <span class="comment">// 通过 registry 中的 BeanDefinitions 数量判断是否有新增的 BeanDefinitions</span></span><br><span class="line">        <span class="keyword">if</span> (registry.getBeanDefinitionCount() &gt; candidateNames.length) &#123;</span><br><span class="line">            <span class="comment">// 重新获取全部 BeanDefinitions 作为候选</span></span><br><span class="line">            String[] newCandidateNames = registry.getBeanDefinitionNames();</span><br><span class="line">            <span class="comment">// 保留旧的候选集合用于快速筛选</span></span><br><span class="line">            Set&lt;String&gt; oldCandidateNames = <span class="keyword">new</span> <span class="title class_">HashSet</span>&lt;String&gt;(Arrays.asList(candidateNames));</span><br><span class="line">            <span class="comment">// 为什么 alreadyParsedClasses 不定义在循环外，需要每次动态地从 alreadyParsed 获取？难道 configurationClass.getMetadata().getClassName() 的结果会变化吗？</span></span><br><span class="line">            <span class="comment">// 如果不存在上述情况，直接在添加到 alreadyParsed 时，添加到 alreadyParsedClasses 就好了呀？</span></span><br><span class="line">            Set&lt;String&gt; alreadyParsedClasses = <span class="keyword">new</span> <span class="title class_">HashSet</span>&lt;String&gt;();</span><br><span class="line">            <span class="keyword">for</span> (ConfigurationClass configurationClass : alreadyParsed) &#123;</span><br><span class="line">                alreadyParsedClasses.add(configurationClass.getMetadata().getClassName());</span><br><span class="line">            &#125;</span><br><span class="line">            <span class="keyword">for</span> (String candidateName : newCandidateNames) &#123;</span><br><span class="line">                <span class="comment">// 快速地排除旧候选</span></span><br><span class="line">                <span class="keyword">if</span> (!oldCandidateNames.contains(candidateName)) &#123;</span><br><span class="line">                    <span class="type">BeanDefinition</span> <span class="variable">bd</span> <span class="operator">=</span> registry.getBeanDefinition(candidateName);</span><br><span class="line">                    <span class="comment">// 检查是否是配置类并且未被解析过（比如同一个配置类，重复注册，无需多次处理）</span></span><br><span class="line">                    <span class="keyword">if</span> (ConfigurationClassUtils.checkConfigurationClassCandidate(bd, <span class="built_in">this</span>.metadataReaderFactory) &amp;&amp;</span><br><span class="line">                            !alreadyParsedClasses.contains(bd.getBeanClassName())) &#123;</span><br><span class="line">                        <span class="comment">// 添加到新的配置类集合</span></span><br><span class="line">                        candidates.add(<span class="keyword">new</span> <span class="title class_">BeanDefinitionHolder</span>(bd, candidateName));</span><br><span class="line">                    &#125;</span><br><span class="line">                &#125;</span><br><span class="line">            &#125;</span><br><span class="line">            candidateNames = newCandidateNames;</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="keyword">while</span> (!candidates.isEmpty());</span><br><span class="line"></span><br><span class="line">    <span class="comment">// Register the ImportRegistry as a bean in order to support ImportAware @Configuration classes</span></span><br><span class="line">    <span class="keyword">if</span> (sbr != <span class="literal">null</span>) &#123;</span><br><span class="line">        <span class="keyword">if</span> (!sbr.containsSingleton(IMPORT_REGISTRY_BEAN_NAME)) &#123;</span><br><span class="line">            sbr.registerSingleton(IMPORT_REGISTRY_BEAN_NAME, parser.getImportRegistry());</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 清理 metadataReaderFactory 缓存</span></span><br><span class="line">    <span class="keyword">if</span> (<span class="built_in">this</span>.metadataReaderFactory <span class="keyword">instanceof</span> CachingMetadataReaderFactory) &#123;</span><br><span class="line">        ((CachingMetadataReaderFactory) <span class="built_in">this</span>.metadataReaderFactory).clearCache();</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
-
-<h3 id="判断是否是配置类"><a href="#判断是否是配置类" class="headerlink" title="判断是否是配置类"></a>判断是否是配置类</h3><p><code>checkConfigurationClassCandidate</code> 方法：</p>
-<ol>
-<li>不能 <code>className</code> 为 <code>null</code> 或 <code>Bean</code> 定义拥有工厂方法</li>
-<li>被 <code>Configuration</code> 注解标注（全配置类）</li>
-<li>被 <code>Component</code>、<code>ComponentScan</code>、<code>Import</code>、<code>ImportResource</code> 注解标注或者拥有被 <code>Bean</code> 注解标注的方法</li>
-<li>设置 <code>order</code> 用于排序</li>
-</ol>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">static</span> <span class="type">boolean</span> <span class="title function_">checkConfigurationClassCandidate</span><span class="params">(BeanDefinition beanDef, MetadataReaderFactory metadataReaderFactory)</span> &#123;</span><br><span class="line">    <span class="type">String</span> <span class="variable">className</span> <span class="operator">=</span> beanDef.getBeanClassName();</span><br><span class="line">    <span class="keyword">if</span> (className == <span class="literal">null</span> || beanDef.getFactoryMethodName() != <span class="literal">null</span>) &#123;</span><br><span class="line">        <span class="comment">// 如果 className 为 null，或者拥有工厂方法，返回 false</span></span><br><span class="line">        <span class="comment">// 举例，被 @Bean 注解的方法返回的 Bean，它的类即使被 @Configuration 注解，也不属于配置类</span></span><br><span class="line">        <span class="keyword">return</span> <span class="literal">false</span>;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 获取 AnnotationMetadata</span></span><br><span class="line">    <span class="comment">// 这些分支对应的场景？</span></span><br><span class="line">    AnnotationMetadata metadata;</span><br><span class="line">    <span class="keyword">if</span> (beanDef <span class="keyword">instanceof</span> AnnotatedBeanDefinition &amp;&amp;</span><br><span class="line">            className.equals(((AnnotatedBeanDefinition) beanDef).getMetadata().getClassName())) &#123;</span><br><span class="line">        <span class="comment">// 可以复用 BeanDefinition 中已经解析过的 metadata</span></span><br><span class="line">        metadata = ((AnnotatedBeanDefinition) beanDef).getMetadata();</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="keyword">else</span> <span class="keyword">if</span> (beanDef <span class="keyword">instanceof</span> AbstractBeanDefinition &amp;&amp; ((AbstractBeanDefinition) beanDef).hasBeanClass()) &#123;</span><br><span class="line">        <span class="comment">// 检查是否存在已经加载的 Class，因为我们可能甚至无法加载该类的类文件</span></span><br><span class="line">        <span class="comment">// 创建 metadata 看起来也没干什么事情呀</span></span><br><span class="line">        Class&lt;?&gt; beanClass = ((AbstractBeanDefinition) beanDef).getBeanClass();</span><br><span class="line">        metadata = <span class="keyword">new</span> <span class="title class_">StandardAnnotationMetadata</span>(beanClass, <span class="literal">true</span>);</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="keyword">else</span> &#123;</span><br><span class="line">        <span class="comment">// 第二个分支提到的无法加载类文件的情况是指这里吗？</span></span><br><span class="line">        <span class="keyword">try</span> &#123;</span><br><span class="line">            <span class="type">MetadataReader</span> <span class="variable">metadataReader</span> <span class="operator">=</span> metadataReaderFactory.getMetadataReader(className);</span><br><span class="line">            metadata = metadataReader.getAnnotationMetadata();</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="keyword">catch</span> (IOException ex) &#123;</span><br><span class="line">            <span class="keyword">if</span> (logger.isDebugEnabled()) &#123;</span><br><span class="line">                logger.debug(<span class="string">&quot;Could not find class file for introspecting configuration annotations: &quot;</span> + className, ex);</span><br><span class="line">            &#125;</span><br><span class="line">            <span class="keyword">return</span> <span class="literal">false</span>;</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">if</span> (isFullConfigurationCandidate(metadata)) &#123;</span><br><span class="line">        <span class="comment">// 属于 Full 配置类，添加 Attribute 标记，标识已处理过</span></span><br><span class="line">        beanDef.setAttribute(CONFIGURATION_CLASS_ATTRIBUTE, CONFIGURATION_CLASS_FULL);</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="keyword">else</span> <span class="keyword">if</span> (isLiteConfigurationCandidate(metadata)) &#123;</span><br><span class="line">        <span class="comment">// 属于 Lite 配置类，添加 Attribute 标记，标识已处理过</span></span><br><span class="line">        beanDef.setAttribute(CONFIGURATION_CLASS_ATTRIBUTE, CONFIGURATION_CLASS_LITE);</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="keyword">else</span> &#123;</span><br><span class="line">        <span class="keyword">return</span> <span class="literal">false</span>;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 不管是 Full 还是 Lite 配置类，检查是否被 @Order 注解，如果有则设置到 Attribute，用于排序</span></span><br><span class="line">    Map&lt;String, Object&gt; orderAttributes = metadata.getAnnotationAttributes(Order.class.getName());</span><br><span class="line">    <span class="keyword">if</span> (orderAttributes != <span class="literal">null</span>) &#123;</span><br><span class="line">        beanDef.setAttribute(ORDER_ATTRIBUTE, orderAttributes.get(AnnotationUtils.VALUE));</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">return</span> <span class="literal">true</span>;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
-
-<h4 id="判断是否属于-Full-配置类"><a href="#判断是否属于-Full-配置类" class="headerlink" title="判断是否属于 Full 配置类"></a>判断是否属于 Full 配置类</h4><ol>
-<li>被 <code>Configuration</code> 注解标注</li>
-</ol>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">static</span> <span class="type">boolean</span> <span class="title function_">isFullConfigurationCandidate</span><span class="params">(AnnotationMetadata metadata)</span> &#123;</span><br><span class="line">    <span class="keyword">return</span> metadata.isAnnotated(Configuration.class.getName());</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
-
-<h4 id="判断是否属于-Lite-配置类"><a href="#判断是否属于-Lite-配置类" class="headerlink" title="判断是否属于 Lite 配置类"></a>判断是否属于 Lite 配置类</h4><ol>
-<li>被 <code>Component</code>、<code>ComponentScan</code>、<code>Import</code>、<code>ImportResource</code> 注解标注</li>
-<li>拥有被 <code>Bean</code> 注解标注的方法</li>
-</ol>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">static</span> <span class="type">boolean</span> <span class="title function_">isLiteConfigurationCandidate</span><span class="params">(AnnotationMetadata metadata)</span> &#123;</span><br><span class="line">    <span class="comment">// 接口和注解，直接返回 false</span></span><br><span class="line">    <span class="keyword">if</span> (metadata.isInterface()) &#123;</span><br><span class="line">        <span class="keyword">return</span> <span class="literal">false</span>;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 如果被 @Component、@ComponentScan、@Import、@ImportResource 注解</span></span><br><span class="line">    <span class="keyword">for</span> (String indicator : candidateIndicators) &#123;</span><br><span class="line">        <span class="keyword">if</span> (metadata.isAnnotated(indicator)) &#123;</span><br><span class="line">            <span class="keyword">return</span> <span class="literal">true</span>;</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 拥有被 @Bean 注解的方法</span></span><br><span class="line">    <span class="keyword">try</span> &#123;</span><br><span class="line">        <span class="keyword">return</span> metadata.hasAnnotatedMethods(Bean.class.getName());</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="keyword">catch</span> (Throwable ex) &#123;</span><br><span class="line">        <span class="keyword">if</span> (logger.isDebugEnabled()) &#123;</span><br><span class="line">            logger.debug(<span class="string">&quot;Failed to introspect @Bean methods on class [&quot;</span> + metadata.getClassName() + <span class="string">&quot;]: &quot;</span> + ex);</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="keyword">return</span> <span class="literal">false</span>;</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+<h2 id="参考链接"><a href="#参考链接" class="headerlink" title="参考链接"></a>参考链接</h2><p><a href="https://zhuanlan.zhihu.com/p/46973701">Linux 让终端走代理的几种方法</a><br><a href="https://blog.51cto.com/u_14814563/5415887">Linux ❀ wget设置代理</a><br><a href="https://cloud-atlas.readthedocs.io/zh_CN/latest/docker/network/docker_proxy.html#docker-server-proxy">配置Docker使用代理</a><br><a href="https://note.qidong.name/2020/05/docker-proxy/">Docker的三种网络代理配置</a><br><a href="https://neucrack.com/p/286">docker 设置代理，以及国内加速镜像设置</a></p>
+]]></content>
+      <tags>
+        <tag>docker</tag>
+        <tag>proxy</tag>
+      </tags>
+  </entry>
+  <entry>
+    <title>Nginx 反向代理在家庭网络中的应用</title>
+    <url>/2023/12/01/Nginx-reverse-proxy-for-home-networks/</url>
+    <content><![CDATA[<p>原先在使用 <code>Cloudflare Tunnel</code> 访问家庭网络中的服务时，是直接将域名解析到相应服务。尽管 <code>Cloudflare</code> 已经提供相关的请求统计和安全防护功能，部分服务自身也有访问日志，但是为了更好地监控和跟踪对外服务的使用情况，采集 <code>Cloudlfare</code> 统计中缺少的新，决定使用 <code>Nginx</code> 反向代理内部服务，统一内部服务的访问入口。简而言之就是，又折腾一些有的没的。以上修改带来的一个附加好处是在局域网内访问服务时，通过在 <code>hosts</code> 文件中添加域名映射，可以用更加容易记忆的域名代替 <code>IP + port</code> 的形式去访问。</p>
+<span id="more"></span>
 
-<h3 id="循环处理直至没有新增配置类"><a href="#循环处理直至没有新增配置类" class="headerlink" title="循环处理直至没有新增配置类"></a>循环处理直至没有新增配置类</h3><p>循环处理部分的代码有点难阅读。</p>
-<ul>
-<li>首先是因为命名比较相似，需要理清各个变量的含义和作用<ul>
-<li><code>candidateNames</code> 就是普普通通的纯候选者（全部 <code>BeanDefinitions</code>），每次循环在解析完，加载 <code>BeanDefinitions</code> 后可能会新增</li>
-<li><code>configCandidates</code>（<code>candidates</code>） 就是符合配置类条件的配置类。虽然命名带 <code>Candidates</code>，其实已经是正牌，并非候选。感觉 <code>configClass</code> 更容易理解，但该变量名另作他用。有新增就要继续循环</li>
-<li><code>configClass</code>（<code>ConfigurationClass</code> 类） 是经过解析的配置模型，不要和配置类搞混了。后面出现过 <code>ConfigurationModel</code>，感觉该命名更加准确</li>
-</ul>
-</li>
-<li>其次是因为对黑盒 parser 的作用不了解，个人经验如果完全将 <code>parser</code> 当作黑盒对待，不了解解析过程、解析的返回结果以及如何处理返回结果，理解循环解析的过程时会有点困难<ul>
-<li><code>parser.parse(candidates)</code> 解析配置类构建得到配置模型（<code>ConfigurationClass</code>）。以副作用的形式进行处理，传入 <code>ConfigurationClass</code>，返回 <code>ConfigurationClass</code></li>
-<li><code>this.reader.loadBeanDefinitions(configClasses)</code> 从配置模型（<code>ConfigurationClass</code>）中加载 <code>BeanDefinitions</code></li>
-</ul>
-</li>
-</ul>
 <blockquote>
-<p>再次提示：<strong>正视配置模型的概念，<code>ConfigurationClassParser</code> 使用配置类构建配置模型并校验；<code>ConfigurationClassBeanDefinitionReader</code> 从配置模型中读取 <code>bean</code> 定义。</strong></p>
+<p><code>Cloudflare Tunnel</code> 相较于 <code>Zerotier</code> 和 <code>OpenVPN</code>，尽管它们三者都能避免直接开放家庭网络，但前者可以让用户直接使用域名访问到局域网中的服务，便于分享。但它的速度和延迟并不理想，还有人反馈存在网络不稳定的现象，但作为个人玩具还是够用的。有朋友使用公网服务器配合打洞软件和家庭网络中的服务器组网，实现相同目标的同时效果更好。</p>
 </blockquote>
-<div style="width:50%;margin:auto"><img src="/2023/11/23/source-code-analysis-of-Spring-Configuration-annotation/Pasted%20image%2020231127214511.png" class="" title="处理配置类流程图"></div>
+<h2 id="网络结构示意图"><a href="#网络结构示意图" class="headerlink" title="网络结构示意图"></a>网络结构示意图</h2><p>客户端发起请求，请求经 <code>Cloudflare</code> 转发到局域网中的 <code>Tunnel</code>。原先，<code>Tunnel</code> 如虚线箭头所示，直接将请求发向目标服务，如今改为发向 <code>Nginx</code>，由 <code>Nginx</code> 反向代理，发向目标服务。</p>
+<img src="/2023/12/01/Nginx-reverse-proxy-for-home-networks/Pasted%20image%2020231201202859.png" class="" title="网络结构示意图">
 
-<h3 id="解析配置类构建配置模型"><a href="#解析配置类构建配置模型" class="headerlink" title="解析配置类构建配置模型"></a>解析配置类构建配置模型</h3><p><code>parser.parse(candidates)</code> 正式进入解析过程，<code>ConfigurationClassParser</code> 负责将配置类转换为配置模型（<code>ConfigurationClass</code>）。</p>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title function_">parse</span><span class="params">(Set&lt;BeanDefinitionHolder&gt; configCandidates)</span> &#123;</span><br><span class="line">    <span class="built_in">this</span>.deferredImportSelectors = <span class="keyword">new</span> <span class="title class_">LinkedList</span>&lt;DeferredImportSelectorHolder&gt;();</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 循环依次处理配置类</span></span><br><span class="line">    <span class="keyword">for</span> (BeanDefinitionHolder holder : configCandidates) &#123;</span><br><span class="line">        <span class="type">BeanDefinition</span> <span class="variable">bd</span> <span class="operator">=</span> holder.getBeanDefinition();</span><br><span class="line">        <span class="keyword">try</span> &#123;</span><br><span class="line">            <span class="keyword">if</span> (bd <span class="keyword">instanceof</span> AnnotatedBeanDefinition) &#123;</span><br><span class="line">                <span class="comment">// 拥有注解的 BeanDefinition</span></span><br><span class="line">                parse(((AnnotatedBeanDefinition) bd).getMetadata(), holder.getBeanName());</span><br><span class="line">            &#125;</span><br><span class="line">            <span class="keyword">else</span> <span class="keyword">if</span> (bd <span class="keyword">instanceof</span> AbstractBeanDefinition &amp;&amp; ((AbstractBeanDefinition) bd).hasBeanClass()) &#123;</span><br><span class="line">                parse(((AbstractBeanDefinition) bd).getBeanClass(), holder.getBeanName());</span><br><span class="line">            &#125;</span><br><span class="line">            <span class="keyword">else</span> &#123;</span><br><span class="line">                parse(bd.getBeanClassName(), holder.getBeanName());</span><br><span class="line">            &#125;</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="keyword">catch</span> (BeanDefinitionStoreException ex) &#123;</span><br><span class="line">            <span class="keyword">throw</span> ex;</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="keyword">catch</span> (Throwable ex) &#123;</span><br><span class="line">            <span class="keyword">throw</span> <span class="keyword">new</span> <span class="title class_">BeanDefinitionStoreException</span>(</span><br><span class="line">                    <span class="string">&quot;Failed to parse configuration class [&quot;</span> + bd.getBeanClassName() + <span class="string">&quot;]&quot;</span>, ex);</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    processDeferredImportSelectors();</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+<h2 id="配置"><a href="#配置" class="headerlink" title="配置"></a>配置</h2><h3 id="docker-compose-yml"><a href="#docker-compose-yml" class="headerlink" title="docker-compose.yml"></a>docker-compose.yml</h3><p><code>Nginx</code> 和 <code>Tunnel</code> 还有其他内部服务应处于同一个网络中。</p>
+<figure class="highlight yaml"><table><tr><td class="code"><pre><span class="line"><span class="attr">version:</span> <span class="string">&quot;1.0&quot;</span></span><br><span class="line"><span class="attr">services:</span></span><br><span class="line">  <span class="attr">nginx:</span></span><br><span class="line">    <span class="attr">image:</span> <span class="string">nginx:1.25.3</span></span><br><span class="line">    <span class="attr">container_name:</span> <span class="string">nginx</span></span><br><span class="line">    <span class="attr">ports:</span></span><br><span class="line">      <span class="bullet">-</span> <span class="number">80</span><span class="string">:80</span></span><br><span class="line">    <span class="attr">volumes:</span></span><br><span class="line">      <span class="bullet">-</span> <span class="string">$PWD/etc/nginx/conf.d:/etc/nginx/conf.d</span></span><br><span class="line">      <span class="bullet">-</span> <span class="string">$PWD/etc/nginx/nginx.conf:/etc/nginx/nginx.conf</span></span><br><span class="line">      <span class="bullet">-</span> <span class="string">$PWD/log:/var/log/nginx</span></span><br><span class="line">    <span class="attr">networks:</span></span><br><span class="line">      <span class="bullet">-</span> <span class="string">my-network</span></span><br><span class="line">    <span class="attr">restart:</span> <span class="string">unless-stopped</span></span><br><span class="line"></span><br><span class="line"><span class="attr">networks:</span></span><br><span class="line">  <span class="attr">my-network:</span></span><br><span class="line">    <span class="attr">external:</span> <span class="literal">true</span></span><br></pre></td></tr></table></figure>
 
-<p>每次都创建一个新的配置模型 <code>ConfigurationClass</code>，最终处理结果以副作用的形式直接表现在配置模型上。</p>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">protected</span> <span class="keyword">final</span> <span class="keyword">void</span> <span class="title function_">parse</span><span class="params">(AnnotationMetadata metadata, String beanName)</span> <span class="keyword">throws</span> IOException &#123;</span><br><span class="line">    <span class="comment">// 每次都 new 一个 ConfigurationClass</span></span><br><span class="line">    processConfigurationClass(<span class="keyword">new</span> <span class="title class_">ConfigurationClass</span>(metadata, beanName));</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+<h3 id="etc-nginx-nginx-conf"><a href="#etc-nginx-nginx-conf" class="headerlink" title="&#x2F;etc&#x2F;nginx&#x2F;nginx.conf"></a>&#x2F;etc&#x2F;nginx&#x2F;nginx.conf</h3><p>在最后新增了拒绝未匹配成功的域名，在 <code>Cloudflare Tunnel</code> 的使用场景中，其实用处不大，因为未经配置的域名也无法解析到 <code>Nginx</code> 服务。</p>
+<figure class="highlight plaintext"><table><tr><td class="code"><pre><span class="line">user  nginx;</span><br><span class="line">worker_processes  auto;</span><br><span class="line"></span><br><span class="line">error_log  /var/log/nginx/error.log notice;</span><br><span class="line">pid        /var/run/nginx.pid;</span><br><span class="line"></span><br><span class="line"></span><br><span class="line">events &#123;</span><br><span class="line">    worker_connections  1024;</span><br><span class="line">&#125;</span><br><span class="line"></span><br><span class="line"></span><br><span class="line">http &#123;</span><br><span class="line">    include       /etc/nginx/mime.types;</span><br><span class="line">    default_type  application/octet-stream;</span><br><span class="line"></span><br><span class="line">    log_format  main  &#x27;$remote_addr - $remote_user [$time_local] &quot;$request&quot; &#x27;</span><br><span class="line">                      &#x27;$status $body_bytes_sent &quot;$http_referer&quot; &#x27;</span><br><span class="line">                      &#x27;&quot;$http_user_agent&quot; &quot;$http_x_forwarded_for&quot;&#x27;;</span><br><span class="line"></span><br><span class="line">    access_log  /var/log/nginx/access.log  main;</span><br><span class="line"></span><br><span class="line">    sendfile        on;</span><br><span class="line">    #tcp_nopush     on;</span><br><span class="line"></span><br><span class="line">    keepalive_timeout  65;</span><br><span class="line"></span><br><span class="line">    #gzip  on;</span><br><span class="line"></span><br><span class="line">    include /etc/nginx/conf.d/*.conf;</span><br><span class="line"></span><br><span class="line">    #以上是默认的配置内容，新增拒绝未匹配成功的域名</span><br><span class="line">    server &#123;</span><br><span class="line">        listen 80 default_server;</span><br><span class="line">        server_name _;</span><br><span class="line"></span><br><span class="line">        return 404;</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
 
-<div style="width:50%;margin:auto"><img src="/2023/11/23/source-code-analysis-of-Spring-Configuration-annotation/Pasted%20image%2020231127215414.png" class="" title="处理配置模型"></div>
+<h3 id="etc-nginx-conf-d"><a href="#etc-nginx-conf-d" class="headerlink" title="&#x2F;etc&#x2F;nginx&#x2F;conf.d"></a>&#x2F;etc&#x2F;nginx&#x2F;conf.d</h3><p>本目录下，配置 server 块。</p>
+<figure class="highlight plaintext"><table><tr><td class="code"><pre><span class="line">server &#123;</span><br><span class="line">    listen       80;</span><br><span class="line">    listen  [::]:80;</span><br><span class="line">    server_name  your.domain.com;</span><br><span class="line"></span><br><span class="line">    location / &#123;</span><br><span class="line">        #转发请求</span><br><span class="line">        proxy_pass http://your-service;</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
 
-<p>处理配置模型的方法 <code>processConfigurationClass</code>。</p>
-<ol>
-<li>检查配置模型是否曾经处理过</li>
-<li>处理配置模型（递归处理配置类和它的父类）</li>
-</ol>
-<p><code>SourceClass</code> 是一个简单的包装器，无论带注解的源类是如何被加载的，允许以统一的方式处理。</p>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">protected</span> <span class="keyword">void</span> <span class="title function_">processConfigurationClass</span><span class="params">(ConfigurationClass configClass)</span> <span class="keyword">throws</span> IOException &#123;</span><br><span class="line">    <span class="comment">// 判断是否跳过</span></span><br><span class="line">    <span class="keyword">if</span> (<span class="built_in">this</span>.conditionEvaluator.shouldSkip(configClass.getMetadata(), ConfigurationPhase.PARSE_CONFIGURATION)) &#123;</span><br><span class="line">        <span class="keyword">return</span>;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// ConfigurationClass 重写了 equals 和 hashCode 方法</span></span><br><span class="line">    <span class="type">ConfigurationClass</span> <span class="variable">existingClass</span> <span class="operator">=</span> <span class="built_in">this</span>.configurationClasses.get(configClass);</span><br><span class="line">    <span class="comment">// 判断是否已经存在</span></span><br><span class="line">    <span class="keyword">if</span> (existingClass != <span class="literal">null</span>) &#123;</span><br><span class="line">        <span class="comment">// 检查是否是导入的</span></span><br><span class="line">        <span class="keyword">if</span> (configClass.isImported()) &#123;</span><br><span class="line">            <span class="keyword">if</span> (existingClass.isImported()) &#123;</span><br><span class="line">                <span class="comment">// 如果新的旧的 isImported 均为 true，合并 ImportedBy 集合</span></span><br><span class="line">                existingClass.mergeImportedBy(configClass);</span><br><span class="line">            &#125;</span><br><span class="line">            <span class="comment">// Otherwise ignore new imported config class; existing non-imported class overrides it.</span></span><br><span class="line">            <span class="keyword">return</span>;</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="keyword">else</span> &#123;</span><br><span class="line">            <span class="comment">// 可能找到了一个显式定义的配置类，用于代替导入的，直接移除旧的</span></span><br><span class="line">            <span class="built_in">this</span>.configurationClasses.remove(configClass);</span><br><span class="line">            <span class="keyword">for</span> (Iterator&lt;ConfigurationClass&gt; it = <span class="built_in">this</span>.knownSuperclasses.values().iterator(); it.hasNext();) &#123;</span><br><span class="line">                <span class="keyword">if</span> (configClass.equals(it.next())) &#123;</span><br><span class="line">                    it.remove();</span><br><span class="line">                &#125;</span><br><span class="line">            &#125;</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 递归处理配置类和它的父类</span></span><br><span class="line">    <span class="type">SourceClass</span> <span class="variable">sourceClass</span> <span class="operator">=</span> asSourceClass(configClass);</span><br><span class="line">    <span class="keyword">do</span> &#123;</span><br><span class="line">        sourceClass = doProcessConfigurationClass(configClass, sourceClass);</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="keyword">while</span> (sourceClass != <span class="literal">null</span>);</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 保存处理过的配置模型</span></span><br><span class="line">    <span class="built_in">this</span>.configurationClasses.put(configClass, configClass);</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+<h2 id="正向代理和反向代理"><a href="#正向代理和反向代理" class="headerlink" title="正向代理和反向代理"></a>正向代理和反向代理</h2><h3 id="代理（正向代理）"><a href="#代理（正向代理）" class="headerlink" title="代理（正向代理）"></a>代理（正向代理）</h3><p><strong>代理</strong>（Proxy）也称为网络代理，是一种特殊的网络服务，允许一个终端通过这个服务与另一个终端进行非直接的连接。一般认为代理服务有利于保障网络终端的隐私或安全，在一定程度上能够阻止网络攻击。</p>
+<img src="/2023/12/01/Nginx-reverse-proxy-for-home-networks/Pasted%20image%2020231201202645.png" class="" title="正向代理">
 
-<p>注意 <code>ConfigurationClass</code> 重写了 <code>equals</code> 和 <code>hashCode</code> 方法，<code>metadata</code> 的 <code>className</code> 相同代表配置模型也相同。</p>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="type">boolean</span> <span class="title function_">equals</span><span class="params">(Object other)</span> &#123;</span><br><span class="line">    <span class="keyword">return</span> (<span class="built_in">this</span> == other || (other <span class="keyword">instanceof</span> ConfigurationClass &amp;&amp;</span><br><span class="line">            getMetadata().getClassName().equals(((ConfigurationClass) other).getMetadata().getClassName())));</span><br><span class="line">&#125;</span><br><span class="line"></span><br><span class="line"><span class="keyword">public</span> <span class="type">int</span> <span class="title function_">hashCode</span><span class="params">()</span> &#123;</span><br><span class="line">    <span class="keyword">return</span> getMetadata().getClassName().hashCode();</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+<h4 id="功能"><a href="#功能" class="headerlink" title="功能"></a>功能</h4><ul>
+<li>提高访问速度</li>
+<li>隐藏真实IP</li>
+<li>突破网站的区域限制</li>
+<li>突破网络审查</li>
+<li>……</li>
+</ul>
+<h3 id="反向代理"><a href="#反向代理" class="headerlink" title="反向代理"></a>反向代理</h3><p>反向代理（Reverse Proxy）在电脑网络中是代理服务器的一种。服务器根据客户端的请求，从其关联的一组或多组后端服务器上获取资源，然后再将这些资源返回给客户端，客户端只会得知反向代理的 <code>IP</code> 地址，而不知道在代理服务器后面的服务器集群的存在。</p>
+<img src="/2023/12/01/Nginx-reverse-proxy-for-home-networks/Pasted%20image%2020231201202654.png" class="" title="反向代理">
 
-<p>真正处理配置模型的方法，根据注释很容易知道，如果配置类携带了 <code>PropertySource</code>、<code>ComponentScan</code>、<code>Import</code>、<code>ImportResource</code>、<code>Bean</code> 等注解，就是在这里被处理的。<br>比如示例中被 <code>Bean</code> 注解标注的方法，<code>configClass.addBeanMethod(new BeanMethod(methodMetadata, configClass))</code> 将它以 <code>BeanMethod</code> 的形式添加到配置模型中。</p>
-<ol>
-<li>先递归的处理成员（嵌套）类</li>
-<li>处理 <code>@PropertySource</code></li>
-<li>处理 <code>@ComponentScan</code></li>
-<li>处理 <code>@Import</code></li>
-<li>处理 <code>@ImportResource</code></li>
-<li>处理 <code>@Bean</code>，<strong>使用 <code>ASM</code> 代替 <code>JVM</code> 反射，以获得确定性的声明顺序</strong></li>
-<li>处理接口的默认方法</li>
-<li>检查是否有父类</li>
-</ol>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">protected</span> <span class="keyword">final</span> SourceClass <span class="title function_">doProcessConfigurationClass</span><span class="params">(ConfigurationClass configClass, SourceClass sourceClass)</span></span><br><span class="line">        <span class="keyword">throws</span> IOException &#123;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// Recursively process any member (nested) classes first</span></span><br><span class="line">    processMemberClasses(configClass, sourceClass);</span><br><span class="line"></span><br><span class="line">    <span class="comment">// Process any @PropertySource annotations</span></span><br><span class="line">    <span class="keyword">for</span> (AnnotationAttributes propertySource : AnnotationConfigUtils.attributesForRepeatable(</span><br><span class="line">            sourceClass.getMetadata(), PropertySources.class,</span><br><span class="line">            org.springframework.context.annotation.PropertySource.class)) &#123;</span><br><span class="line">        <span class="keyword">if</span> (<span class="built_in">this</span>.environment <span class="keyword">instanceof</span> ConfigurableEnvironment) &#123;</span><br><span class="line">            processPropertySource(propertySource);</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="keyword">else</span> &#123;</span><br><span class="line">            logger.warn(<span class="string">&quot;Ignoring @PropertySource annotation on [&quot;</span> + sourceClass.getMetadata().getClassName() +</span><br><span class="line">                    <span class="string">&quot;]. Reason: Environment must implement ConfigurableEnvironment&quot;</span>);</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// Process any @ComponentScan annotations</span></span><br><span class="line">    Set&lt;AnnotationAttributes&gt; componentScans = AnnotationConfigUtils.attributesForRepeatable(</span><br><span class="line">            sourceClass.getMetadata(), ComponentScans.class, ComponentScan.class);</span><br><span class="line">    <span class="keyword">if</span> (!componentScans.isEmpty() &amp;&amp;</span><br><span class="line">            !<span class="built_in">this</span>.conditionEvaluator.shouldSkip(sourceClass.getMetadata(), ConfigurationPhase.REGISTER_BEAN)) &#123;</span><br><span class="line">        <span class="keyword">for</span> (AnnotationAttributes componentScan : componentScans) &#123;</span><br><span class="line">            <span class="comment">// The config class is annotated with @ComponentScan -&gt; perform the scan immediately</span></span><br><span class="line">            Set&lt;BeanDefinitionHolder&gt; scannedBeanDefinitions =</span><br><span class="line">                    <span class="built_in">this</span>.componentScanParser.parse(componentScan, sourceClass.getMetadata().getClassName());</span><br><span class="line">            <span class="comment">// Check the set of scanned definitions for any further config classes and parse recursively if needed</span></span><br><span class="line">            <span class="keyword">for</span> (BeanDefinitionHolder holder : scannedBeanDefinitions) &#123;</span><br><span class="line">                <span class="keyword">if</span> (ConfigurationClassUtils.checkConfigurationClassCandidate(</span><br><span class="line">                        holder.getBeanDefinition(), <span class="built_in">this</span>.metadataReaderFactory)) &#123;</span><br><span class="line">                    parse(holder.getBeanDefinition().getBeanClassName(), holder.getBeanName());</span><br><span class="line">                &#125;</span><br><span class="line">            &#125;</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// Process any @Import annotations</span></span><br><span class="line">    processImports(configClass, sourceClass, getImports(sourceClass), <span class="literal">true</span>);</span><br><span class="line"></span><br><span class="line">    <span class="comment">// Process any @ImportResource annotations</span></span><br><span class="line">    <span class="keyword">if</span> (sourceClass.getMetadata().isAnnotated(ImportResource.class.getName())) &#123;</span><br><span class="line">        <span class="type">AnnotationAttributes</span> <span class="variable">importResource</span> <span class="operator">=</span></span><br><span class="line">                AnnotationConfigUtils.attributesFor(sourceClass.getMetadata(), ImportResource.class);</span><br><span class="line">        String[] resources = importResource.getStringArray(<span class="string">&quot;locations&quot;</span>);</span><br><span class="line">        Class&lt;? <span class="keyword">extends</span> <span class="title class_">BeanDefinitionReader</span>&gt; readerClass = importResource.getClass(<span class="string">&quot;reader&quot;</span>);</span><br><span class="line">        <span class="keyword">for</span> (String resource : resources) &#123;</span><br><span class="line">            <span class="type">String</span> <span class="variable">resolvedResource</span> <span class="operator">=</span> <span class="built_in">this</span>.environment.resolveRequiredPlaceholders(resource);</span><br><span class="line">            configClass.addImportedResource(resolvedResource, readerClass);</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// Process individual @Bean methods</span></span><br><span class="line">    Set&lt;MethodMetadata&gt; beanMethods = retrieveBeanMethodMetadata(sourceClass);</span><br><span class="line">    <span class="keyword">for</span> (MethodMetadata methodMetadata : beanMethods) &#123;</span><br><span class="line">        configClass.addBeanMethod(<span class="keyword">new</span> <span class="title class_">BeanMethod</span>(methodMetadata, configClass));</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// Process default methods on interfaces</span></span><br><span class="line">    processInterfaces(configClass, sourceClass);</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 如果有父类，且之前没有处理过，返回父类继续处理</span></span><br><span class="line">    <span class="keyword">if</span> (sourceClass.getMetadata().hasSuperClass()) &#123;</span><br><span class="line">        <span class="type">String</span> <span class="variable">superclass</span> <span class="operator">=</span> sourceClass.getMetadata().getSuperClassName();</span><br><span class="line">        <span class="keyword">if</span> (!superclass.startsWith(<span class="string">&quot;java&quot;</span>) &amp;&amp; !<span class="built_in">this</span>.knownSuperclasses.containsKey(superclass)) &#123;</span><br><span class="line">            <span class="built_in">this</span>.knownSuperclasses.put(superclass, configClass);</span><br><span class="line">            <span class="comment">// Superclass found, return its annotation metadata and recurse</span></span><br><span class="line">            <span class="keyword">return</span> sourceClass.getSuperClass();</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// No superclass -&gt; processing is complete</span></span><br><span class="line">    <span class="keyword">return</span> <span class="literal">null</span>;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
-
-<h3 id="读取配置模型，加载-Bean-定义"><a href="#读取配置模型，加载-Bean-定义" class="headerlink" title="读取配置模型，加载 Bean 定义"></a>读取配置模型，加载 Bean 定义</h3><p><code>this.reader.loadBeanDefinitions(configClasses)</code> 读取配置模型的内容，注册 <code>BeanDefinitions</code> 到 <code>BeanDefinition Registry</code>（也就是 <code>BeanFactory</code>）。</p>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title function_">loadBeanDefinitions</span><span class="params">(Set&lt;ConfigurationClass&gt; configurationModel)</span> &#123;</span><br><span class="line">    <span class="type">TrackedConditionEvaluator</span> <span class="variable">trackedConditionEvaluator</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">TrackedConditionEvaluator</span>();</span><br><span class="line">    <span class="comment">// 叫 ConfigurationModel 多好啊，ConfigurationClass 真让人容易误解</span></span><br><span class="line">    <span class="keyword">for</span> (ConfigurationClass configClass : configurationModel) &#123;</span><br><span class="line">        loadBeanDefinitionsForConfigurationClass(configClass, trackedConditionEvaluator);</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
-
-<p>处理单独的一个配置模型。</p>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">private</span> <span class="keyword">void</span> <span class="title function_">loadBeanDefinitionsForConfigurationClass</span><span class="params">(ConfigurationClass configClass,</span></span><br><span class="line"><span class="params">        TrackedConditionEvaluator trackedConditionEvaluator)</span> &#123;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">if</span> (trackedConditionEvaluator.shouldSkip(configClass)) &#123;</span><br><span class="line">        <span class="type">String</span> <span class="variable">beanName</span> <span class="operator">=</span> configClass.getBeanName();</span><br><span class="line">        <span class="keyword">if</span> (StringUtils.hasLength(beanName) &amp;&amp; <span class="built_in">this</span>.registry.containsBeanDefinition(beanName)) &#123;</span><br><span class="line">            <span class="built_in">this</span>.registry.removeBeanDefinition(beanName);</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="built_in">this</span>.importRegistry.removeImportingClass(configClass.getMetadata().getClassName());</span><br><span class="line">        <span class="keyword">return</span>;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">if</span> (configClass.isImported()) &#123;</span><br><span class="line">        registerBeanDefinitionForImportedConfigurationClass(configClass);</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="keyword">for</span> (BeanMethod beanMethod : configClass.getBeanMethods()) &#123;</span><br><span class="line">        loadBeanDefinitionsForBeanMethod(beanMethod);</span><br><span class="line">    &#125;</span><br><span class="line">    loadBeanDefinitionsFromImportedResources(configClass.getImportedResources());</span><br><span class="line">    loadBeanDefinitionsFromRegistrars(configClass.getImportBeanDefinitionRegistrars());</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
-
-<h2 id="增强配置类"><a href="#增强配置类" class="headerlink" title="增强配置类"></a>增强配置类</h2><p>我们在介绍 <code>ConfigurationClassPostProcessor</code> 时提过，它既实现了接口 <code>BeanDefinitionRegistryPostProcessor</code>，也因此同时实现了接口 <code>BeanFactoryPostProcessor</code>。在 <code>invokeBeanFactoryPostProcessors(beanFactory)</code> 阶段，调用 <code>postProcessBeanDefinitionRegistry</code> 方法，成功注册配置类引入的 <code>Bean</code> 后，紧接着会调用 <code>postProcessBeanFactory</code> 方法，增强配置类本身。</p>
-<blockquote>
-<p><code>ConfigurationClasses</code> 在之前还是指配置模型，这里就又指配置类了。。。真让人头秃。</p>
-</blockquote>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title function_">postProcessBeanFactory</span><span class="params">(ConfigurableListableBeanFactory beanFactory)</span> &#123;</span><br><span class="line">    <span class="comment">// ...</span></span><br><span class="line"></span><br><span class="line">    <span class="comment">// 增强配置类</span></span><br><span class="line">    enhanceConfigurationClasses(beanFactory);</span><br><span class="line">    <span class="comment">// 添加后处理器 ImportAwareBeanPostProcessor</span></span><br><span class="line">    beanFactory.addBeanPostProcessor(<span class="keyword">new</span> <span class="title class_">ImportAwareBeanPostProcessor</span>(beanFactory));</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
-
-<h3 id="增强所有-Full-类型配置类"><a href="#增强所有-Full-类型配置类" class="headerlink" title="增强所有 Full 类型配置类"></a>增强所有 Full 类型配置类</h3><ol>
-<li>查找所有 <code>Full</code> 类型的配置类</li>
-<li>依次使用 <code>ConfigurationClassEnhancer</code> 增强目标类，成功则替换 <code>BeanClass</code>（不成功的情况是已经增强过）</li>
-</ol>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title function_">enhanceConfigurationClasses</span><span class="params">(ConfigurableListableBeanFactory beanFactory)</span> &#123;</span><br><span class="line">    Map&lt;String, AbstractBeanDefinition&gt; configBeanDefs = <span class="keyword">new</span> <span class="title class_">LinkedHashMap</span>&lt;String, AbstractBeanDefinition&gt;();</span><br><span class="line">    <span class="comment">// 获取全部的 BeanDefinitions 检查是否存在全配置类（FullConfigurationClass）</span></span><br><span class="line">    <span class="keyword">for</span> (String beanName : beanFactory.getBeanDefinitionNames()) &#123;</span><br><span class="line">        <span class="type">BeanDefinition</span> <span class="variable">beanDef</span> <span class="operator">=</span> beanFactory.getBeanDefinition(beanName);</span><br><span class="line">        <span class="keyword">if</span> (ConfigurationClassUtils.isFullConfigurationClass(beanDef)) &#123;</span><br><span class="line">            <span class="keyword">if</span> (!(beanDef <span class="keyword">instanceof</span> AbstractBeanDefinition)) &#123;</span><br><span class="line">                <span class="keyword">throw</span> <span class="keyword">new</span> <span class="title class_">BeanDefinitionStoreException</span>(<span class="string">&quot;Cannot enhance @Configuration bean definition &#x27;&quot;</span> +</span><br><span class="line">                        beanName + <span class="string">&quot;&#x27; since it is not stored in an AbstractBeanDefinition subclass&quot;</span>);</span><br><span class="line">            &#125;</span><br><span class="line">            <span class="keyword">else</span> <span class="keyword">if</span> (logger.isWarnEnabled() &amp;&amp; beanFactory.containsSingleton(beanName)) &#123;</span><br><span class="line">                logger.warn(<span class="string">&quot;Cannot enhance @Configuration bean definition &#x27;&quot;</span> + beanName +</span><br><span class="line">                        <span class="string">&quot;&#x27; since its singleton instance has been created too early. The typical cause &quot;</span> +</span><br><span class="line">                        <span class="string">&quot;is a non-static @Bean method with a BeanDefinitionRegistryPostProcessor &quot;</span> +</span><br><span class="line">                        <span class="string">&quot;return type: Consider declaring such methods as &#x27;static&#x27;.&quot;</span>);</span><br><span class="line">            &#125;</span><br><span class="line">            configBeanDefs.put(beanName, (AbstractBeanDefinition) beanDef);</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="keyword">if</span> (configBeanDefs.isEmpty()) &#123;</span><br><span class="line">        <span class="keyword">return</span>;</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="comment">// 通过 CGLib 增强</span></span><br><span class="line">    <span class="type">ConfigurationClassEnhancer</span> <span class="variable">enhancer</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">ConfigurationClassEnhancer</span>();</span><br><span class="line">    <span class="keyword">for</span> (Map.Entry&lt;String, AbstractBeanDefinition&gt; entry : configBeanDefs.entrySet()) &#123;</span><br><span class="line">        <span class="type">AbstractBeanDefinition</span> <span class="variable">beanDef</span> <span class="operator">=</span> entry.getValue();</span><br><span class="line">        <span class="comment">// 如果被 @Configuration 注解的类被代理，则始终代理目标类（proxy target class），在 Attributes 中标记</span></span><br><span class="line">        beanDef.setAttribute(AutoProxyUtils.PRESERVE_TARGET_CLASS_ATTRIBUTE, Boolean.TRUE);</span><br><span class="line">        <span class="keyword">try</span> &#123;</span><br><span class="line">            Class&lt;?&gt; configClass = beanDef.resolveBeanClass(<span class="built_in">this</span>.beanClassLoader);</span><br><span class="line">            Class&lt;?&gt; enhancedClass = enhancer.enhance(configClass, <span class="built_in">this</span>.beanClassLoader);</span><br><span class="line">            <span class="keyword">if</span> (configClass != enhancedClass) &#123;</span><br><span class="line">                <span class="keyword">if</span> (logger.isDebugEnabled()) &#123;</span><br><span class="line">                    logger.debug(String.format(<span class="string">&quot;Replacing bean definition &#x27;%s&#x27; existing class &#x27;%s&#x27; with &quot;</span> +</span><br><span class="line">                            <span class="string">&quot;enhanced class &#x27;%s&#x27;&quot;</span>, entry.getKey(), configClass.getName(), enhancedClass.getName()));</span><br><span class="line">                &#125;</span><br><span class="line">                <span class="comment">// 如果成功增强，则替换掉 BeanClass</span></span><br><span class="line">                beanDef.setBeanClass(enhancedClass);</span><br><span class="line">            &#125;</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="keyword">catch</span> (Throwable ex) &#123;</span><br><span class="line">            <span class="keyword">throw</span> <span class="keyword">new</span> <span class="title class_">IllegalStateException</span>(<span class="string">&quot;Cannot load configuration class: &quot;</span> + beanDef.getBeanClassName(), ex);</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
-
-<ol>
-<li>如果增强过则不再处理。这往往代表容器中存在多个 <code>ConfigurationClassPostProcessor</code>，虽然无害，但是建议调整配置</li>
-<li>如果未曾增强过，则创建增强类</li>
-</ol>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> Class&lt;?&gt; enhance(Class&lt;?&gt; configClass, ClassLoader classLoader) &#123;</span><br><span class="line">    <span class="comment">// 增强过的类都实现了 EnhancedConfiguration，因此可以起到标识作用</span></span><br><span class="line">    <span class="keyword">if</span> (EnhancedConfiguration.class.isAssignableFrom(configClass)) &#123;</span><br><span class="line">        <span class="keyword">if</span> (logger.isDebugEnabled()) &#123;</span><br><span class="line">            logger.debug(String.format(<span class="string">&quot;Ignoring request to enhance %s as it has &quot;</span> +</span><br><span class="line">                    <span class="string">&quot;already been enhanced. This usually indicates that more than one &quot;</span> +</span><br><span class="line">                    <span class="string">&quot;ConfigurationClassPostProcessor has been registered (e.g. via &quot;</span> +</span><br><span class="line">                    <span class="string">&quot;&lt;context:annotation-config&gt;). This is harmless, but you may &quot;</span> +</span><br><span class="line">                    <span class="string">&quot;want check your configuration and remove one CCPP if possible&quot;</span>,</span><br><span class="line">                    configClass.getName()));</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="keyword">return</span> configClass;</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="comment">// 创建增强类</span></span><br><span class="line">    Class&lt;?&gt; enhancedClass = createClass(newEnhancer(configClass, classLoader));</span><br><span class="line">    <span class="keyword">if</span> (logger.isDebugEnabled()) &#123;</span><br><span class="line">        logger.debug(String.format(<span class="string">&quot;Successfully enhanced %s; enhanced class name is: %s&quot;</span>,</span><br><span class="line">                configClass.getName(), enhancedClass.getName()));</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="keyword">return</span> enhancedClass;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
-
-<h3 id="创建-CGLib-子类"><a href="#创建-CGLib-子类" class="headerlink" title="创建 CGLib 子类"></a>创建 CGLib 子类</h3><blockquote>
-<p>如果完全不熟悉 <code>CGLib</code>，可以单独查阅一下相关资料，稍作了解。</p>
-</blockquote>
-<p>创建 <code>Enhancer</code>，并设置属性。</p>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">private</span> Enhancer <span class="title function_">newEnhancer</span><span class="params">(Class&lt;?&gt; superclass, ClassLoader classLoader)</span> &#123;</span><br><span class="line">    <span class="type">Enhancer</span> <span class="variable">enhancer</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">Enhancer</span>();</span><br><span class="line">    <span class="comment">// 设置被增强的类为父类</span></span><br><span class="line">    enhancer.setSuperclass(superclass);</span><br><span class="line">    <span class="comment">// 设置接口，可以用于标识类被增强过</span></span><br><span class="line">    enhancer.setInterfaces(<span class="keyword">new</span> <span class="title class_">Class</span>&lt;?&gt;[] &#123;EnhancedConfiguration.class&#125;);</span><br><span class="line">    enhancer.setUseFactory(<span class="literal">false</span>);</span><br><span class="line">    <span class="comment">// 设置命名策略，BySpringCGLIB 后缀</span></span><br><span class="line">    enhancer.setNamingPolicy(SpringNamingPolicy.INSTANCE);</span><br><span class="line">    <span class="comment">// 设置生成策略，这里为 CGLib 子类新增一个 $$beanFactory 属性</span></span><br><span class="line">    enhancer.setStrategy(<span class="keyword">new</span> <span class="title class_">BeanFactoryAwareGeneratorStrategy</span>(classLoader));</span><br><span class="line">    <span class="comment">// 设置 CallbackFilter，用于方法匹配</span></span><br><span class="line">    enhancer.setCallbackFilter(CALLBACK_FILTER);</span><br><span class="line">    enhancer.setCallbackTypes(CALLBACK_FILTER.getCallbackTypes());</span><br><span class="line">    <span class="keyword">return</span> enhancer;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
-
-<ul>
-<li>所有因为 <code>Configuration</code> 注解而被增强的配置类，它的 <code>CGLib</code> 子类都实现了这个标记接口，用于检查候选类是否已经增强过，避免重复增强。</li>
-<li>该接口继承了 <code>BeanFactoryAware</code>。**创建得到的 <code>CGLib</code> 子类必须能够访问 <code>BeanFactory</code>**，用以在工厂方法交叉调用时获取已经创建的 <code>Bean</code> 而非真正执行。</li>
+<h4 id="功能-1"><a href="#功能-1" class="headerlink" title="功能"></a>功能</h4><ul>
+<li>对客户端隐藏服务器（集群）的 IP 地址</li>
+<li>安全，可作为应用层防火墙</li>
+<li><strong>负载均衡</strong></li>
+<li>缓存服务，缓存静态内容和短时间内大量访问请求的动态内容</li>
+<li>压缩内容，节省带宽</li>
+<li>……</li>
 </ul>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">interface</span> <span class="title class_">EnhancedConfiguration</span> <span class="keyword">extends</span> <span class="title class_">BeanFactoryAware</span> &#123;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
-
-<p>创建子类，并注册静态回调。</p>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">private</span> Class&lt;?&gt; createClass(Enhancer enhancer) &#123;</span><br><span class="line">    Class&lt;?&gt; subclass = enhancer.createClass();</span><br><span class="line">    <span class="comment">// 注册静态回调（虽然注释不太理解）</span></span><br><span class="line">    Enhancer.registerStaticCallbacks(subclass, CALLBACKS);</span><br><span class="line">    <span class="keyword">return</span> subclass;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
-
-<p><code>CALLBACKS</code>、<code>CALLBACK_FILTER</code> 和 <code>$$beanFactory</code> 属性名都是 <code>ConfigurationClassEnhancer</code> 的静态属性。</p>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">class</span> <span class="title class_">ConfigurationClassEnhancer</span> &#123;</span><br><span class="line">    <span class="comment">// The callbacks to use. Note that these callbacks must be stateless.</span></span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">static</span> <span class="keyword">final</span> Callback[] CALLBACKS = <span class="keyword">new</span> <span class="title class_">Callback</span>[] &#123;</span><br><span class="line">            <span class="keyword">new</span> <span class="title class_">BeanMethodInterceptor</span>(),</span><br><span class="line">            <span class="keyword">new</span> <span class="title class_">BeanFactoryAwareMethodInterceptor</span>(),</span><br><span class="line">            NoOp.INSTANCE</span><br><span class="line">    &#125;;</span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">static</span> <span class="keyword">final</span> <span class="type">ConditionalCallbackFilter</span> <span class="variable">CALLBACK_FILTER</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">ConditionalCallbackFilter</span>(CALLBACKS);</span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">static</span> <span class="keyword">final</span> <span class="type">String</span> <span class="variable">BEAN_FACTORY_FIELD</span> <span class="operator">=</span> <span class="string">&quot;$$beanFactory&quot;</span>;</span><br><span class="line">    <span class="comment">// ...</span></span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
-
-<h3 id="匹配回调-ConditionalCallbackFilter"><a href="#匹配回调-ConditionalCallbackFilter" class="headerlink" title="匹配回调 ConditionalCallbackFilter"></a>匹配回调 ConditionalCallbackFilter</h3><p><code>ConditionalCallbackFilter</code> 实现了 <code>CGLib</code> 的 <code>CallbackFilter</code> 接口，<code>accept</code> 方法返回准备使用的 <code>Callback</code> 的索引。匹配规则如下：</p>
-<ol>
-<li>遍历 <code>callbacks</code>，依次判断<ol>
-<li>如果 <code>this.callbacks[i]</code> 不是 <code>ConditionalCallback</code> 类型，直接返回。根据 <code>CALLBACKS</code> 的值，这意味着没有匹配到合适的 <code>MethodInterceptor</code>，选择 <code>NoOp.INSTANCE</code>。</li>
-<li>如果 <code>this.callbacks[i]</code> 是 <code>ConditionalCallback</code> 类型，使用 <code>isMatch</code> 方法判断是否匹配，匹配成功返回对应索引</li>
-</ol>
-</li>
-</ol>
-<p><code>Callback</code> 中除了 <code>NoOp.INSTANCE</code>，还有 <code>BeanFactoryAwareMethodInterceptor</code> 用于拦截 <code>setBeanFactory</code> 方法，以及 <code>BeanMethodInterceptor</code> 拦截 <code>@Bean</code> 方法。</p>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">private</span> <span class="keyword">static</span> <span class="keyword">class</span> <span class="title class_">ConditionalCallbackFilter</span> <span class="keyword">implements</span> <span class="title class_">CallbackFilter</span> &#123;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">final</span> Callback[] callbacks;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">final</span> Class&lt;?&gt;[] callbackTypes;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">public</span> <span class="title function_">ConditionalCallbackFilter</span><span class="params">(Callback[] callbacks)</span> &#123;</span><br><span class="line">        <span class="built_in">this</span>.callbacks = callbacks;</span><br><span class="line">        <span class="built_in">this</span>.callbackTypes = <span class="keyword">new</span> <span class="title class_">Class</span>&lt;?&gt;[callbacks.length];</span><br><span class="line">        <span class="keyword">for</span> (<span class="type">int</span> <span class="variable">i</span> <span class="operator">=</span> <span class="number">0</span>; i &lt; callbacks.length; i++) &#123;</span><br><span class="line">            <span class="built_in">this</span>.callbackTypes[i] = callbacks[i].getClass();</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="meta">@Override</span></span><br><span class="line">    <span class="keyword">public</span> <span class="type">int</span> <span class="title function_">accept</span><span class="params">(Method method)</span> &#123;</span><br><span class="line">        <span class="keyword">for</span> (<span class="type">int</span> <span class="variable">i</span> <span class="operator">=</span> <span class="number">0</span>; i &lt; <span class="built_in">this</span>.callbacks.length; i++) &#123;</span><br><span class="line">            <span class="keyword">if</span> (!(<span class="built_in">this</span>.callbacks[i] <span class="keyword">instanceof</span> ConditionalCallback) ||</span><br><span class="line">                    ((ConditionalCallback) <span class="built_in">this</span>.callbacks[i]).isMatch(method)) &#123;</span><br><span class="line">                <span class="keyword">return</span> i;</span><br><span class="line">            &#125;</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="keyword">throw</span> <span class="keyword">new</span> <span class="title class_">IllegalStateException</span>(<span class="string">&quot;No callback available for method &quot;</span> + method.getName());</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">public</span> Class&lt;?&gt;[] getCallbackTypes() &#123;</span><br><span class="line">        <span class="keyword">return</span> <span class="built_in">this</span>.callbackTypes;</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
-
-<h3 id="拦截-setBeanFactory-方法"><a href="#拦截-setBeanFactory-方法" class="headerlink" title="拦截 setBeanFactory 方法"></a>拦截 setBeanFactory 方法</h3><p><code>BeanFactoryAwareMethodInterceptor</code> 实现了 <code>MethodInterceptor</code> 和 <code>ConditionalCallback</code> 接口。<code>isMatch</code> 匹配到 <code>BeanFactoryAware</code> 接口的 <code>setBeanFactory</code> 方法，则调用 <code>intercept</code> 方法，为 <code>$$beanFactory</code> 属性赋值。<code>$$beanFactory</code> 是 <code>CGLib</code> 生成的 <code>BeanFactory</code> 类型的属性。这个属性是通过设置 <code>enhancer.setStrategy(new BeanFactoryAwareGeneratorStrategy(classLoader))</code> 生成的。</p>
-<p>这样，当配置类 <code>Bean</code> 被创建时，会因为实现了 <code>BeanFactoryAware</code>，在初始化阶段被调用 <code>setBeanFactory</code> 方法而被拦截。拦截后将获得的 <code>beanFactory</code> 实例保存在 <code>CGlib</code> 生成的属性 <code>$$beanFactory</code> 中。</p>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">private</span> <span class="keyword">static</span> <span class="keyword">class</span> <span class="title class_">BeanFactoryAwareMethodInterceptor</span> <span class="keyword">implements</span> <span class="title class_">MethodInterceptor</span>, ConditionalCallback &#123;</span><br><span class="line"></span><br><span class="line">    <span class="meta">@Override</span></span><br><span class="line">    <span class="keyword">public</span> Object <span class="title function_">intercept</span><span class="params">(Object obj, Method method, Object[] args, MethodProxy proxy)</span> <span class="keyword">throws</span> Throwable &#123;</span><br><span class="line">        <span class="type">Field</span> <span class="variable">field</span> <span class="operator">=</span> ReflectionUtils.findField(obj.getClass(), BEAN_FACTORY_FIELD);</span><br><span class="line">        Assert.state(field != <span class="literal">null</span>, <span class="string">&quot;Unable to find generated BeanFactory field&quot;</span>);</span><br><span class="line">        <span class="comment">// 设置 beanFactory 的值</span></span><br><span class="line">        field.set(obj, args[<span class="number">0</span>]);</span><br><span class="line"></span><br><span class="line">        <span class="comment">// Does the actual (non-CGLIB) superclass implement BeanFactoryAware?</span></span><br><span class="line">        <span class="comment">// If so, call its setBeanFactory() method. If not, just exit.</span></span><br><span class="line">        <span class="comment">// 如果实际的（non-CGLIB）父类实现了 BeanFactoryAware 接口，调用它的 setBeanFactory() 方法</span></span><br><span class="line">        <span class="keyword">if</span> (BeanFactoryAware.class.isAssignableFrom(ClassUtils.getUserClass(obj.getClass().getSuperclass()))) &#123;</span><br><span class="line">            <span class="keyword">return</span> proxy.invokeSuper(obj, args);</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="keyword">return</span> <span class="literal">null</span>;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 根据方法名、参数数量、参数类型、方法所在的类判断</span></span><br><span class="line">    <span class="meta">@Override</span></span><br><span class="line">    <span class="keyword">public</span> <span class="type">boolean</span> <span class="title function_">isMatch</span><span class="params">(Method candidateMethod)</span> &#123;</span><br><span class="line">        <span class="keyword">return</span> (candidateMethod.getName().equals(<span class="string">&quot;setBeanFactory&quot;</span>) &amp;&amp;</span><br><span class="line">                candidateMethod.getParameterTypes().length == <span class="number">1</span> &amp;&amp;</span><br><span class="line">                BeanFactory.class == candidateMethod.getParameterTypes()[<span class="number">0</span>] &amp;&amp;</span><br><span class="line">                BeanFactoryAware.class.isAssignableFrom(candidateMethod.getDeclaringClass()));</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
-
-<h4 id="生成-beanFactory-属性"><a href="#生成-beanFactory-属性" class="headerlink" title="生成 $$beanFactory 属性"></a>生成 $$beanFactory 属性</h4><p><code>BeanFactoryAwareGeneratorStrategy</code> 为配置的 <code>CGLib</code> 子类生成一个访问控制符为 <code>public</code>、类型为 <code>BeanFactory</code>、名称为 <code>$$beanFactory</code> 的属性。</p>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">private</span> <span class="keyword">static</span> <span class="keyword">class</span> <span class="title class_">BeanFactoryAwareGeneratorStrategy</span> <span class="keyword">extends</span> <span class="title class_">DefaultGeneratorStrategy</span> &#123;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">final</span> ClassLoader classLoader;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">public</span> <span class="title function_">BeanFactoryAwareGeneratorStrategy</span><span class="params">(ClassLoader classLoader)</span> &#123;</span><br><span class="line">        <span class="built_in">this</span>.classLoader = classLoader;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="meta">@Override</span></span><br><span class="line">    <span class="keyword">protected</span> ClassGenerator <span class="title function_">transform</span><span class="params">(ClassGenerator cg)</span> <span class="keyword">throws</span> Exception &#123;</span><br><span class="line">        <span class="type">ClassEmitterTransformer</span> <span class="variable">transformer</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">ClassEmitterTransformer</span>() &#123;</span><br><span class="line">            <span class="meta">@Override</span></span><br><span class="line">            <span class="keyword">public</span> <span class="keyword">void</span> <span class="title function_">end_class</span><span class="params">()</span> &#123;</span><br><span class="line">                <span class="comment">// 新增一个访问控制符为 public、类型为 BeanFactory、名称为 $$beanFactory 的属性</span></span><br><span class="line">                declare_field(Constants.ACC_PUBLIC, BEAN_FACTORY_FIELD, Type.getType(BeanFactory.class), <span class="literal">null</span>);</span><br><span class="line">                <span class="built_in">super</span>.end_class();</span><br><span class="line">            &#125;</span><br><span class="line">        &#125;;</span><br><span class="line">        <span class="keyword">return</span> <span class="keyword">new</span> <span class="title class_">TransformingClassGenerator</span>(cg, transformer);</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 处理逻辑是清晰的，作用和影响不清楚</span></span><br><span class="line">    <span class="meta">@Override</span></span><br><span class="line">    <span class="keyword">public</span> <span class="type">byte</span>[] generate(ClassGenerator cg) <span class="keyword">throws</span> Exception &#123;</span><br><span class="line">        <span class="keyword">if</span> (<span class="built_in">this</span>.classLoader == <span class="literal">null</span>) &#123;</span><br><span class="line">            <span class="keyword">return</span> <span class="built_in">super</span>.generate(cg);</span><br><span class="line">        &#125;</span><br><span class="line"></span><br><span class="line">        <span class="type">Thread</span> <span class="variable">currentThread</span> <span class="operator">=</span> Thread.currentThread();</span><br><span class="line">        ClassLoader threadContextClassLoader;</span><br><span class="line">        <span class="keyword">try</span> &#123;</span><br><span class="line">            threadContextClassLoader = currentThread.getContextClassLoader();</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="keyword">catch</span> (Throwable ex) &#123;</span><br><span class="line">            <span class="comment">// Cannot access thread context ClassLoader - falling back...</span></span><br><span class="line">            <span class="keyword">return</span> <span class="built_in">super</span>.generate(cg);</span><br><span class="line">        &#125;</span><br><span class="line"></span><br><span class="line">        <span class="type">boolean</span> <span class="variable">overrideClassLoader</span> <span class="operator">=</span> !<span class="built_in">this</span>.classLoader.equals(threadContextClassLoader);</span><br><span class="line">        <span class="keyword">if</span> (overrideClassLoader) &#123;</span><br><span class="line">            currentThread.setContextClassLoader(<span class="built_in">this</span>.classLoader);</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="keyword">try</span> &#123;</span><br><span class="line">            <span class="keyword">return</span> <span class="built_in">super</span>.generate(cg);</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="keyword">finally</span> &#123;</span><br><span class="line">            <span class="keyword">if</span> (overrideClassLoader) &#123;</span><br><span class="line">                <span class="comment">// Reset original thread context ClassLoader.</span></span><br><span class="line">                currentThread.setContextClassLoader(threadContextClassLoader);</span><br><span class="line">            &#125;</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
-
-<h3 id="核心：拦截-Bean-方法"><a href="#核心：拦截-Bean-方法" class="headerlink" title="核心：拦截 @Bean 方法"></a>核心：拦截 @Bean 方法</h3><p><code>BeanMethodInterceptor</code> 实现了 <code>MethodInterceptor</code> 和 <code>ConditionalCallback</code> 接口。<code>isMatch</code> 匹配到被 <code>Bean</code> 注解标注的方法，则调用 <code>intercept</code> 方法。被 <code>Configuration</code> 注解标注的配置类，它定义的被 <code>Bean</code> 注解标注的方法，只会在第一次被调用时真正地执行并创建实例，后续不会再执行的“魔法”就在这里。即使你手动地调用配置类的方法，或是被 <code>Bean</code> 注解标注的方法间互相调用，都是如此。</p>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> Object <span class="title function_">intercept</span><span class="params">(Object enhancedConfigInstance, Method beanMethod, Object[] beanMethodArgs,</span></span><br><span class="line"><span class="params">            MethodProxy cglibMethodProxy)</span> <span class="keyword">throws</span> Throwable &#123;</span><br><span class="line">    <span class="comment">// 通过反射，获得 beanFactory 实例</span></span><br><span class="line">    <span class="type">ConfigurableBeanFactory</span> <span class="variable">beanFactory</span> <span class="operator">=</span> getBeanFactory(enhancedConfigInstance);</span><br><span class="line">    <span class="comment">// 获取 beanName，默认是方法名，可以自定义</span></span><br><span class="line">    <span class="type">String</span> <span class="variable">beanName</span> <span class="operator">=</span> BeanAnnotationHelper.determineBeanNameFor(beanMethod);</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 确定这个 bean 是否属于 scoped-proxy（不了解）</span></span><br><span class="line">    <span class="type">Scope</span> <span class="variable">scope</span> <span class="operator">=</span> AnnotatedElementUtils.findMergedAnnotation(beanMethod, Scope.class);</span><br><span class="line">    <span class="keyword">if</span> (scope != <span class="literal">null</span> &amp;&amp; scope.proxyMode() != ScopedProxyMode.NO) &#123;</span><br><span class="line">        <span class="type">String</span> <span class="variable">scopedBeanName</span> <span class="operator">=</span> ScopedProxyCreator.getTargetBeanName(beanName);</span><br><span class="line">        <span class="keyword">if</span> (beanFactory.isCurrentlyInCreation(scopedBeanName)) &#123;</span><br><span class="line">            beanName = scopedBeanName;</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// To handle the case of an inter-bean method reference, we must explicitly check the</span></span><br><span class="line">    <span class="comment">// container for already cached instances.</span></span><br><span class="line"></span><br><span class="line">    <span class="comment">// First, check to see if the requested bean is a FactoryBean. If so, create a subclass</span></span><br><span class="line">    <span class="comment">// proxy that intercepts calls to getObject() and returns any cached bean instance.</span></span><br><span class="line">    <span class="comment">// This ensures that the semantics of calling a FactoryBean from within @Bean methods</span></span><br><span class="line">    <span class="comment">// is the same as that of referring to a FactoryBean within XML. See SPR-6602.</span></span><br><span class="line">    <span class="keyword">if</span> (factoryContainsBean(beanFactory, BeanFactory.FACTORY_BEAN_PREFIX + beanName) &amp;&amp;</span><br><span class="line">            factoryContainsBean(beanFactory, beanName)) &#123;</span><br><span class="line">        <span class="type">Object</span> <span class="variable">factoryBean</span> <span class="operator">=</span> beanFactory.getBean(BeanFactory.FACTORY_BEAN_PREFIX + beanName);</span><br><span class="line">        <span class="keyword">if</span> (factoryBean <span class="keyword">instanceof</span> ScopedProxyFactoryBean) &#123;</span><br><span class="line">            <span class="comment">// Scoped proxy factory beans are a special case and should not be further proxied</span></span><br><span class="line">        &#125;</span><br><span class="line">        <span class="keyword">else</span> &#123;</span><br><span class="line">            <span class="comment">// It is a candidate FactoryBean - go ahead with enhancement</span></span><br><span class="line">            <span class="comment">// 处理 FactoryBean 类型</span></span><br><span class="line">            <span class="keyword">return</span> enhanceFactoryBean(factoryBean, beanMethod.getReturnType(), beanFactory, beanName);</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 检查 beanMethod 是不是当前正在被调用的 FactoryMethod</span></span><br><span class="line">    <span class="keyword">if</span> (isCurrentlyInvokedFactoryMethod(beanMethod)) &#123;</span><br><span class="line">        <span class="comment">// The factory is calling the bean method in order to instantiate and register the bean</span></span><br><span class="line">        <span class="comment">// (i.e. via a getBean() call) -&gt; invoke the super implementation of the method to actually</span></span><br><span class="line">        <span class="comment">// create the bean instance.</span></span><br><span class="line">        <span class="keyword">if</span> (logger.isWarnEnabled() &amp;&amp;</span><br><span class="line">                BeanFactoryPostProcessor.class.isAssignableFrom(beanMethod.getReturnType())) &#123;</span><br><span class="line">            logger.warn(String.format(<span class="string">&quot;@Bean method %s.%s is non-static and returns an object &quot;</span> +</span><br><span class="line">                            <span class="string">&quot;assignable to Spring&#x27;s BeanFactoryPostProcessor interface. This will &quot;</span> +</span><br><span class="line">                            <span class="string">&quot;result in a failure to process annotations such as @Autowired, &quot;</span> +</span><br><span class="line">                            <span class="string">&quot;@Resource and @PostConstruct within the method&#x27;s declaring &quot;</span> +</span><br><span class="line">                            <span class="string">&quot;@Configuration class. Add the &#x27;static&#x27; modifier to this method to avoid &quot;</span> +</span><br><span class="line">                            <span class="string">&quot;these container lifecycle issues; see @Bean javadoc for complete details.&quot;</span>,</span><br><span class="line">                    beanMethod.getDeclaringClass().getSimpleName(), beanMethod.getName()));</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="comment">// 调用实际的父类方法，创建 Bean 实例</span></span><br><span class="line">        <span class="keyword">return</span> cglibMethodProxy.invokeSuper(enhancedConfigInstance, beanMethodArgs);</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 从 BeanFactory 里获取</span></span><br><span class="line">    <span class="keyword">return</span> obtainBeanInstanceFromFactory(beanMethod, beanMethodArgs, beanFactory, beanName);</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
-
-<ol>
-<li><code>isCurrentlyInvokedFactoryMethod(beanMethod)</code> 检查 <code>beanMethod</code> 是不是当前正在被调用的 <code>FactoryMethod</code></li>
-<li>如果是，则调用实际的父类方法，创建 <code>Bean</code> 实例</li>
-<li>如果不是，则从 <code>BeanFactory</code> 中获取</li>
-</ol>
-<p>以本文示例进行说明。</p>
-<ol>
-<li>调用 <code>lisi()</code> 前，设置当前正在调用的 <code>FactoryMethod</code> 为 <code>lisi()</code><ol>
-<li>lisi() 调用被拦截后，查询获知当前正在调用的 <code>FactoryMethod</code> 确实是 <code>lisi()</code>，调用父类方法创建</li>
-</ol>
-</li>
-<li>调用 <code>person()</code> 前，设置当前正在调用的 <code>FactoryMethod</code> 为 <code>person()</code><ol>
-<li><code>person()</code> 调用被拦截后，查询获知当前正在调用的 <code>FactoryMethod</code> 确实是 <code>person()</code>，调用父类方法创建</li>
-<li>父类方法内调用了 <code>lisi()</code><ol>
-<li><code>lisi()</code> 调用被拦截后，查询获知当前正在调用的 <code>FactoryMethod</code> 是 <code>person()</code>，从 <code>BeanFactory</code> 中获取</li>
-<li>从 <code>BeanFactory</code> 中获取得到已经创建的 <code>lisi</code></li>
-</ol>
-</li>
-<li>继续创建并返回</li>
-</ol>
-</li>
-</ol>
-<p>以上处理的过程是比较清晰简单的，但是当前正在被调用的 <code>FactoryMethod</code> 是什么时候保存的，怎么处理的，还未明朗。</p>
-<h4 id="isCurrentlyInvokedFactoryMethod"><a href="#isCurrentlyInvokedFactoryMethod" class="headerlink" title="isCurrentlyInvokedFactoryMethod"></a>isCurrentlyInvokedFactoryMethod</h4><p>判断是否是当前正在被调用的 <code>FactoryMethod</code>。</p>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">private</span> <span class="type">boolean</span> <span class="title function_">isCurrentlyInvokedFactoryMethod</span><span class="params">(Method method)</span> &#123;</span><br><span class="line">    <span class="type">Method</span> <span class="variable">currentlyInvoked</span> <span class="operator">=</span> SimpleInstantiationStrategy.getCurrentlyInvokedFactoryMethod();</span><br><span class="line">    <span class="keyword">return</span> (currentlyInvoked != <span class="literal">null</span> &amp;&amp; method.getName().equals(currentlyInvoked.getName()) &amp;&amp;</span><br><span class="line">            Arrays.equals(method.getParameterTypes(), currentlyInvoked.getParameterTypes()));</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
-
-<p>原理是通过 <code>ThreadLocal</code> 记录正在调用的 <code>FactoryMethod</code>。</p>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">class</span> <span class="title class_">SimpleInstantiationStrategy</span> <span class="keyword">implements</span> <span class="title class_">InstantiationStrategy</span> &#123;</span><br><span class="line"></span><br><span class="line">	<span class="keyword">private</span> <span class="keyword">static</span> <span class="keyword">final</span> ThreadLocal&lt;Method&gt; currentlyInvokedFactoryMethod = <span class="keyword">new</span> <span class="title class_">ThreadLocal</span>&lt;Method&gt;();</span><br><span class="line"></span><br><span class="line">	<span class="comment">/**</span></span><br><span class="line"><span class="comment">	 * Return the factory method currently being invoked or &#123;<span class="doctag">@code</span> null&#125; if none.</span></span><br><span class="line"><span class="comment">	 * &lt;p&gt;Allows factory method implementations to determine whether the current</span></span><br><span class="line"><span class="comment">	 * caller is the container itself as opposed to user code.</span></span><br><span class="line"><span class="comment">	 */</span></span><br><span class="line">	<span class="keyword">public</span> <span class="keyword">static</span> Method <span class="title function_">getCurrentlyInvokedFactoryMethod</span><span class="params">()</span> &#123;</span><br><span class="line">		<span class="keyword">return</span> currentlyInvokedFactoryMethod.get();</span><br><span class="line">	&#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
-
-<p>这里只是通过 <code>get</code> 获取 <code>currentlyInvokedFactoryMethod</code> 的值，我们还不知道它是在哪更新的。</p>
-<h3 id="currentlyInvokedFactoryMethod-的“来龙去脉”"><a href="#currentlyInvokedFactoryMethod-的“来龙去脉”" class="headerlink" title="currentlyInvokedFactoryMethod 的“来龙去脉”"></a>currentlyInvokedFactoryMethod 的“来龙去脉”</h3><p>当 <code>BeanFactory</code> 创建 <code>Bean</code> 实例时，被 <code>Bean</code> 注解标注的方法注册的 <code>Bean</code> 在实例化时是使用工厂方法而不是构造器方法。</p>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">protected</span> BeanWrapper <span class="title function_">createBeanInstance</span><span class="params">(String beanName, RootBeanDefinition mbd, Object[] args)</span> &#123;</span><br><span class="line">    <span class="comment">// ...</span></span><br><span class="line">    <span class="keyword">if</span> (mbd.getFactoryMethodName() != <span class="literal">null</span>)  &#123;</span><br><span class="line">        <span class="comment">// 如果 FactoryMethodName 不为 null，则通过工厂方法实例化</span></span><br><span class="line">        <span class="keyword">return</span> instantiateUsingFactoryMethod(beanName, mbd, args);</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="comment">// ...</span></span><br><span class="line">&#125;</span><br><span class="line"></span><br><span class="line"><span class="keyword">protected</span> BeanWrapper <span class="title function_">instantiateUsingFactoryMethod</span><span class="params">(</span></span><br><span class="line"><span class="params">        String beanName, RootBeanDefinition mbd, Object[] explicitArgs)</span> &#123;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">return</span> <span class="keyword">new</span> <span class="title class_">ConstructorResolver</span>(<span class="built_in">this</span>).instantiateUsingFactoryMethod(beanName, mbd, explicitArgs);</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
-
-<p><code>BeanFactory</code> 委托给 <code>ConstructorResolver</code>。</p>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> BeanWrapper <span class="title function_">instantiateUsingFactoryMethod</span><span class="params">(</span></span><br><span class="line"><span class="params">		<span class="keyword">final</span> String beanName, <span class="keyword">final</span> RootBeanDefinition mbd, <span class="keyword">final</span> Object[] explicitArgs)</span> &#123;</span><br><span class="line">    <span class="comment">// ...</span></span><br><span class="line">    beanInstance = <span class="built_in">this</span>.beanFactory.getInstantiationStrategy().instantiate(</span><br><span class="line">			mbd, beanName, <span class="built_in">this</span>.beanFactory, factoryBean, factoryMethodToUse, argsToUse);</span><br><span class="line">    <span class="comment">// ...</span></span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
-
-<p><code>AbstractAutowireCapableBeanFactory</code> 的 <code>instantiationStrategy</code> 类型是 <code>CglibSubclassingInstantiationStrategy</code>，继承自 <code>SimpleInstantiationStrategy</code>。</p>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">private</span> <span class="type">InstantiationStrategy</span> <span class="variable">instantiationStrategy</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">CglibSubclassingInstantiationStrategy</span>();</span><br></pre></td></tr></table></figure>
-
-<p><code>SimpleInstantiationStrategy</code> 的 <code>instantiate</code> 方法在通过反射调用 <code>factoryBean</code> 对应的 <code>method</code> 前后，会处理 <code>currentlyInvokedFactoryMethod</code> 的值。</p>
-<blockquote>
-<p>被 <code>Bean</code> 注解标注的方法，对应的 <code>Bean</code> 就是一个 <code>FactoryBean</code>。</p>
-</blockquote>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">class</span> <span class="title class_">SimpleInstantiationStrategy</span> <span class="keyword">implements</span> <span class="title class_">InstantiationStrategy</span> &#123;</span><br><span class="line">    <span class="comment">// ...</span></span><br><span class="line">    <span class="meta">@Override</span></span><br><span class="line">    <span class="keyword">public</span> Object <span class="title function_">instantiate</span><span class="params">(RootBeanDefinition bd, String beanName, BeanFactory owner,</span></span><br><span class="line"><span class="params">            Object factoryBean, <span class="keyword">final</span> Method factoryMethod, Object... args)</span> &#123;</span><br><span class="line">        <span class="keyword">try</span> &#123;</span><br><span class="line">            <span class="keyword">if</span> (System.getSecurityManager() != <span class="literal">null</span>) &#123;</span><br><span class="line">                AccessController.doPrivileged(<span class="keyword">new</span> <span class="title class_">PrivilegedAction</span>&lt;Object&gt;() &#123;</span><br><span class="line">                    <span class="meta">@Override</span></span><br><span class="line">                    <span class="keyword">public</span> Object <span class="title function_">run</span><span class="params">()</span> &#123;</span><br><span class="line">                        ReflectionUtils.makeAccessible(factoryMethod);</span><br><span class="line">                        <span class="keyword">return</span> <span class="literal">null</span>;</span><br><span class="line">                    &#125;</span><br><span class="line">                &#125;);</span><br><span class="line">            &#125;</span><br><span class="line">            <span class="keyword">else</span> &#123;</span><br><span class="line">                ReflectionUtils.makeAccessible(factoryMethod);</span><br><span class="line">            &#125;</span><br><span class="line">            </span><br><span class="line">            <span class="comment">// 获取之前正在被调用的 FactoryMethod</span></span><br><span class="line">            <span class="type">Method</span> <span class="variable">priorInvokedFactoryMethod</span> <span class="operator">=</span> currentlyInvokedFactoryMethod.get();</span><br><span class="line">            <span class="keyword">try</span> &#123;</span><br><span class="line">                <span class="comment">// 将当前正在被调用的 FactoryMethod 保存</span></span><br><span class="line">                currentlyInvokedFactoryMethod.set(factoryMethod);</span><br><span class="line">                <span class="comment">// 调用 FactoryMethod</span></span><br><span class="line">                <span class="keyword">return</span> factoryMethod.invoke(factoryBean, args);</span><br><span class="line">            &#125;</span><br><span class="line">            <span class="keyword">finally</span> &#123;</span><br><span class="line">                <span class="keyword">if</span> (priorInvokedFactoryMethod != <span class="literal">null</span>) &#123;</span><br><span class="line">                    <span class="comment">// 如果之前正在被调用的 FactoryMethod 不为 null，复原</span></span><br><span class="line">                    currentlyInvokedFactoryMethod.set(priorInvokedFactoryMethod);</span><br><span class="line">                &#125;</span><br><span class="line">                <span class="keyword">else</span> &#123;</span><br><span class="line">                    <span class="comment">// 否则移除</span></span><br><span class="line">                    currentlyInvokedFactoryMethod.remove();</span><br><span class="line">                &#125;</span><br><span class="line">            &#125;</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="keyword">catch</span> (IllegalArgumentException ex) &#123;</span><br><span class="line">            <span class="keyword">throw</span> <span class="keyword">new</span> <span class="title class_">BeanInstantiationException</span>(factoryMethod,</span><br><span class="line">                    <span class="string">&quot;Illegal arguments to factory method &#x27;&quot;</span> + factoryMethod.getName() + <span class="string">&quot;&#x27;; &quot;</span> +</span><br><span class="line">                    <span class="string">&quot;args: &quot;</span> + StringUtils.arrayToCommaDelimitedString(args), ex);</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="keyword">catch</span> (IllegalAccessException ex) &#123;</span><br><span class="line">            <span class="keyword">throw</span> <span class="keyword">new</span> <span class="title class_">BeanInstantiationException</span>(factoryMethod,</span><br><span class="line">                    <span class="string">&quot;Cannot access factory method &#x27;&quot;</span> + factoryMethod.getName() + <span class="string">&quot;&#x27;; is it public?&quot;</span>, ex);</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="keyword">catch</span> (InvocationTargetException ex) &#123;</span><br><span class="line">            <span class="type">String</span> <span class="variable">msg</span> <span class="operator">=</span> <span class="string">&quot;Factory method &#x27;&quot;</span> + factoryMethod.getName() + <span class="string">&quot;&#x27; threw exception&quot;</span>;</span><br><span class="line">            <span class="keyword">if</span> (bd.getFactoryBeanName() != <span class="literal">null</span> &amp;&amp; owner <span class="keyword">instanceof</span> ConfigurableBeanFactory &amp;&amp;</span><br><span class="line">                    ((ConfigurableBeanFactory) owner).isCurrentlyInCreation(bd.getFactoryBeanName())) &#123;</span><br><span class="line">                msg = <span class="string">&quot;Circular reference involving containing bean &#x27;&quot;</span> + bd.getFactoryBeanName() + <span class="string">&quot;&#x27; - consider &quot;</span> +</span><br><span class="line">                    <span class="string">&quot;declaring the factory method as static for independence from its containing instance. &quot;</span> + msg;</span><br><span class="line">            &#125;</span><br><span class="line">            <span class="keyword">throw</span> <span class="keyword">new</span> <span class="title class_">BeanInstantiationException</span>(factoryMethod, msg, ex.getTargetException());</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
-
-<h3 id="从-BeanFactory-获取-Bean"><a href="#从-BeanFactory-获取-Bean" class="headerlink" title="从 BeanFactory 获取 Bean"></a>从 BeanFactory 获取 Bean</h3><figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">private</span> Object <span class="title function_">obtainBeanInstanceFromFactory</span><span class="params">(Method beanMethod, Object[] beanMethodArgs,</span></span><br><span class="line"><span class="params">        ConfigurableBeanFactory beanFactory, String beanName)</span> &#123;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// bean 可能已经在创建中</span></span><br><span class="line">    <span class="type">boolean</span> <span class="variable">alreadyInCreation</span> <span class="operator">=</span> beanFactory.isCurrentlyInCreation(beanName);</span><br><span class="line">    <span class="keyword">try</span> &#123;</span><br><span class="line">        <span class="keyword">if</span> (alreadyInCreation) &#123;</span><br><span class="line">            <span class="comment">// 暂时添加到 inCreationCheckExclusions，不再检查是否在创建中</span></span><br><span class="line">            beanFactory.setCurrentlyInCreation(beanName, <span class="literal">false</span>);</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="type">boolean</span> <span class="variable">useArgs</span> <span class="operator">=</span> !ObjectUtils.isEmpty(beanMethodArgs);</span><br><span class="line">        <span class="keyword">if</span> (useArgs &amp;&amp; beanFactory.isSingleton(beanName)) &#123;</span><br><span class="line">            <span class="comment">// 检查参数是否存在 null</span></span><br><span class="line">            <span class="keyword">for</span> (Object arg : beanMethodArgs) &#123;</span><br><span class="line">                <span class="keyword">if</span> (arg == <span class="literal">null</span>) &#123;</span><br><span class="line">                    useArgs = <span class="literal">false</span>;</span><br><span class="line">                    <span class="keyword">break</span>;</span><br><span class="line">                &#125;</span><br><span class="line">            &#125;</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="comment">// 从 beanFactory 获取 Bean</span></span><br><span class="line">        <span class="type">Object</span> <span class="variable">beanInstance</span> <span class="operator">=</span> (useArgs ? beanFactory.getBean(beanName, beanMethodArgs) :</span><br><span class="line">                beanFactory.getBean(beanName));</span><br><span class="line">        <span class="keyword">if</span> (beanInstance != <span class="literal">null</span> &amp;&amp; !ClassUtils.isAssignableValue(beanMethod.getReturnType(), beanInstance)) &#123;</span><br><span class="line">            <span class="type">String</span> <span class="variable">msg</span> <span class="operator">=</span> String.format(<span class="string">&quot;@Bean method %s.%s called as a bean reference &quot;</span> +</span><br><span class="line">                        <span class="string">&quot;for type [%s] but overridden by non-compatible bean instance of type [%s].&quot;</span>,</span><br><span class="line">                        beanMethod.getDeclaringClass().getSimpleName(), beanMethod.getName(),</span><br><span class="line">                        beanMethod.getReturnType().getName(), beanInstance.getClass().getName());</span><br><span class="line">            <span class="keyword">try</span> &#123;</span><br><span class="line">                <span class="type">BeanDefinition</span> <span class="variable">beanDefinition</span> <span class="operator">=</span> beanFactory.getMergedBeanDefinition(beanName);</span><br><span class="line">                msg += <span class="string">&quot; Overriding bean of same name declared in: &quot;</span> + beanDefinition.getResourceDescription();</span><br><span class="line">            &#125;</span><br><span class="line">            <span class="keyword">catch</span> (NoSuchBeanDefinitionException ex) &#123;</span><br><span class="line">                <span class="comment">// Ignore - simply no detailed message then.</span></span><br><span class="line">            &#125;</span><br><span class="line">            <span class="keyword">throw</span> <span class="keyword">new</span> <span class="title class_">IllegalStateException</span>(msg);</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="comment">// 注册依赖关系</span></span><br><span class="line">        <span class="type">Method</span> <span class="variable">currentlyInvoked</span> <span class="operator">=</span> SimpleInstantiationStrategy.getCurrentlyInvokedFactoryMethod();</span><br><span class="line">        <span class="keyword">if</span> (currentlyInvoked != <span class="literal">null</span>) &#123;</span><br><span class="line">            <span class="type">String</span> <span class="variable">outerBeanName</span> <span class="operator">=</span> BeanAnnotationHelper.determineBeanNameFor(currentlyInvoked);</span><br><span class="line">            beanFactory.registerDependentBean(beanName, outerBeanName);</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="keyword">return</span> beanInstance;</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="keyword">finally</span> &#123;</span><br><span class="line">        <span class="keyword">if</span> (alreadyInCreation) &#123;</span><br><span class="line">            <span class="comment">// 复原状态</span></span><br><span class="line">            beanFactory.setCurrentlyInCreation(beanName, <span class="literal">true</span>);</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
-
-<p>延续自本文的文章：</p>
-<ul>
-<li><a href="/2023/12/11/the-truth-about-override-of-ComponentScan-basePackages/" title="ComponentScan 扫描路径覆盖的真相">ComponentScan 扫描路径覆盖的真相</a></li>
-<li><a href="/2023/12/04/use-and-analysis-of-Import-annotation-in-Spring/" title="Spring 中 @Import 注解的使用和源码分析">Spring 中 @Import 注解的使用和源码分析</a></li>
+<h3 id="对比"><a href="#对比" class="headerlink" title="对比"></a>对比</h3><table>
+<thead>
+<tr>
+<th>正向代理</th>
+<th>反向代理</th>
+</tr>
+</thead>
+<tbody><tr>
+<td>客户端的代理</td>
+<td>服务端的代理</td>
+</tr>
+<tr>
+<td>客户端一般需要特别设置</td>
+<td>客户端不用做任何设置</td>
+</tr>
+<tr>
+<td>请求发向目标服务器</td>
+<td>请求发向代理</td>
+</tr>
+<tr>
+<td>服务端知道代理不知道客户端</td>
+<td>客户端知道代理不知道服务器</td>
+</tr>
+</tbody></table>
+<h2 id="参考文章"><a href="#参考文章" class="headerlink" title="参考文章"></a>参考文章</h2><ul>
+<li><a href="https://zh.wikipedia.org/wiki/%E4%BB%A3%E7%90%86%E6%9C%8D%E5%8A%A1%E5%99%A8">代理服务器</a></li>
+<li><a href="https://zh.wikipedia.org/wiki/%E5%8F%8D%E5%90%91%E4%BB%A3%E7%90%86">反向代理</a></li>
 </ul>
 ]]></content>
       <tags>
-        <tag>java</tag>
-        <tag>spring</tag>
+        <tag>nginx</tag>
+        <tag>reverse proxy</tag>
       </tags>
   </entry>
   <entry>
-    <title>Dubbo SPI 的工作原理</title>
-    <url>/2023/11/28/how-does-Dubbo-SPI-works/</url>
-    <content><![CDATA[<p><code>SPI</code> 作为一种服务发现机制，允许程序在运行时动态地加载具体实现类。因其强大的可拓展性，<code>SPI</code> 被广泛应用于各类技术框架中，例如 <code>JDBC</code> 驱动、<code>Spring</code> 和 <code>Dubbo</code> 等等。<code>Dubbo</code> 并未使用原生的 <code>Java SPI</code>，而是重新实现了一套更加强大的 <strong><code>Dubbo SPI</code><strong>。本文将简单介绍 <code>SPI</code> 的设计理念，通过示例带你体会 <code>SPI</code> 的作用，通过 <strong><code>Dubbo</code> 获取拓展的流程图</strong>和</strong>源码分析</strong>带你理解 <code>Dubbo SPI</code> 的工作原理。深入了解 <code>Dubbo SPI</code>，你将能更好地利用这一机制为你的程序提供灵活的拓展功能。</p>
+    <title>使用 logrotate 滚动 Docker 容器内的 Nginx 的日志</title>
+    <url>/2023/12/02/rotating-nginx-logs-in-docker-container-with-logrotate/</url>
+    <content><![CDATA[<p><code>Nginx</code> 没有提供开箱即用的日志滚动功能，而是将其交给使用者自己实现。你既可以按照官方文档的建议通过编写脚本实现，也可以使用 <code>logrotate</code> 管理日志。但是和在普通场景下不同，在使用 <code>Docker</code> 运行 <code>Nginx</code> 时，你可能需要额外考虑一点细节。本文记录了在为 <code>Docker</code> 中的 <code>Nginx</code> 的日志文件配置滚动功能过程中遇到的一些问题和思考。</p>
 <span id="more"></span>
 
-<h2 id="SPI-简介"><a href="#SPI-简介" class="headerlink" title="SPI 简介"></a>SPI 简介</h2><p><code>SPI</code> 的全称是 <code>Service Provider Interface</code>，是一种服务发现机制。一般情况下，一项服务的接口和具体实现，都是服务提供者编写的。在 <code>SPI</code> 机制中，一项服务的接口是服务使用者编写的，不同的服务提供者编写不同的具体实现。在程序运行时，服务加载器动态地为接口加载具体实现类。因为 <code>SPI</code> 具备“动态加载”的特性，我们很容易通过它为程序提供拓展功能。以 <code>Java</code> 的 <code>JDBC</code> 驱动为例，JDK 提供了 <code>java.sql.Driver</code> 接口，各个数据库厂商，例如 <code>MySQL</code>、<code>Oracle</code> 提供具体的实现。</p>
-<img src="/2023/11/28/how-does-Dubbo-SPI-works/Pasted%20image%2020231129010505.png" class="" title="SPI 机制">
+<h2 id="Nginx-滚动日志"><a href="#Nginx-滚动日志" class="headerlink" title="Nginx 滚动日志"></a>Nginx 滚动日志</h2><h3 id="官方文档"><a href="#官方文档" class="headerlink" title="官方文档"></a>官方文档</h3><blockquote>
+<p>In order to rotate log files, they need to be renamed first. After that USR1 signal should be sent to the master process. The master process will then re-open all currently open log files and assign them an unprivileged user under which the worker processes are running, as an owner. After successful re-opening, the master process closes all open files and sends the message to worker process to ask them to re-open files. Worker processes also open new files and close old files right away. As a result, old files are almost immediately available for post processing, such as compression.</p>
+</blockquote>
+<p>根据官方文档的解释，滚动日志文件的流程应如下，你可以自己编写 <code>Shell</code> 脚本配合 <code>crontab</code> 实现定时滚动功能。</p>
+<ol>
+<li>首先重命名日志文件</li>
+<li>之后发送 <code>USR1</code> 信号给 <code>Nginx</code> 主进程，<code>Nginx</code> 将重新打开日志文件</li>
+<li>对日志文件进行后处理，比如压缩（可选）</li>
+</ol>
+<figure class="highlight shell"><table><tr><td class="code"><pre><span class="line"><span class="meta prompt_">$ </span><span class="language-bash"><span class="built_in">mv</span> access.log access.log.0</span></span><br><span class="line"><span class="meta prompt_">$ </span><span class="language-bash"><span class="built_in">kill</span> -USR1 `<span class="built_in">cat</span> master.nginx.pid`</span></span><br><span class="line"><span class="meta prompt_">$ </span><span class="language-bash"><span class="built_in">sleep</span> 1</span></span><br><span class="line"><span class="meta prompt_">$ </span><span class="language-bash">gzip access.log.0    <span class="comment"># do something with access.log.0</span></span></span><br></pre></td></tr></table></figure>
 
-<p>目前 <strong>SPI 的实现方式</strong>大多是将接口实现类的全限定名配置在文件中，并由服务加载器读取配置文件，加载实现类：</p>
-<ul>
-<li>Java SPI：<code>META-INF/services/full.qualified.interface.name</code></li>
-<li>Dubbo SPI：<code>META-INF/dubbo/full.qualified.interface.name</code>（还有其他目录可供选择）</li>
-<li>Spring SPI: <code>META-INF/spring.factories</code></li>
-</ul>
-<h2 id="SPI-示例"><a href="#SPI-示例" class="headerlink" title="SPI 示例"></a>SPI 示例</h2><h3 id="Java-SPI-示例"><a href="#Java-SPI-示例" class="headerlink" title="Java SPI 示例"></a>Java SPI 示例</h3><p>定义一个接口 <code>Animal</code>。</p>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">interface</span> <span class="title class_">Animal</span> &#123;</span><br><span class="line">    <span class="keyword">void</span> <span class="title function_">bark</span><span class="params">()</span>;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+<h4 id="说明"><a href="#说明" class="headerlink" title="说明"></a>说明</h4><ol>
+<li>在没有执行 <code>kill</code> 命令前，即便已经重命名了日志文件，<code>Nginx</code> 还是会向重命名后的文件写入日志。因为在 <code>Linux</code> 系统中，系统内核是根据文件描述符定位文件的。</li>
+<li><code>USR1</code> 是自定义信号，软件的作者自己确定收到该信号后做什么。在 <code>Nginx</code> 中，主进程收到信号后，会重新打开所有当前打开的日志文件并将它们分配给一个非特权用户作为所有者，工作进程就是在该所有者下运行的。成功重新打开后，主进程关闭所有打开的文件并向工作进程发送消息，要求它们重新打开文件。工作进程也打开新文件并立即关闭旧文件。</li>
+</ol>
+<h3 id="使用-logrotate"><a href="#使用-logrotate" class="headerlink" title="使用 logrotate"></a>使用 logrotate</h3><blockquote>
+<p>logrotate is designed to ease administration of systems that generate large numbers of log files. It allows automatic rotation, compression, removal, and mailing of log files. Each log file may be handled daily, weekly, monthly, or when it grows too large.</p>
+</blockquote>
+<p><code>logrotate</code> 旨在简化生成大量日志文件的系统的管理。它允许自动滚动、压缩、删除和邮寄日志文件。每个日志文件可以在每天、每周、每月或当它变得太大时处理。<code>Linux</code> 一般默认安装了 <code>logrotate</code>。</p>
+<h4 id="默认配置文件"><a href="#默认配置文件" class="headerlink" title="默认配置文件"></a>默认配置文件</h4><p>查看默认配置文件：<code>cat /etc/logrotate.conf</code>。</p>
+<figure class="highlight plaintext"><table><tr><td class="code"><pre><span class="line"># see &quot;man logrotate&quot; for details</span><br><span class="line"># 每周滚动日志文件</span><br><span class="line">weekly</span><br><span class="line"></span><br><span class="line"># 默认使用 adm group，因为这是 /var/log/syslog 的所属组</span><br><span class="line">su root adm</span><br><span class="line"></span><br><span class="line"># 保留 4 周的备份（其实是保留 4 个备份，对应 weekly 的设置，就是保留 4 周）</span><br><span class="line">rotate 4</span><br><span class="line"></span><br><span class="line"># 在滚动旧日志文件后，创建新的空日志文件</span><br><span class="line">create</span><br><span class="line"></span><br><span class="line"># 使用日期作为滚动日志文件的后缀</span><br><span class="line">#dateext</span><br><span class="line"></span><br><span class="line"># 如果你希望压缩日志文件，请取消注释</span><br><span class="line">#compress</span><br><span class="line"></span><br><span class="line"># 软件包将日志滚动的配置信息放入此目录中</span><br><span class="line">include /etc/logrotate.d</span><br><span class="line"></span><br><span class="line"># system-specific logs may be also be configured here.</span><br></pre></td></tr></table></figure>
 
-<p>定义两个实现类 <code>Dog</code> 和 <code>Cat</code>。</p>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">class</span> <span class="title class_">Dog</span> <span class="keyword">implements</span> <span class="title class_">Animal</span> &#123;</span><br><span class="line">    <span class="meta">@Override</span></span><br><span class="line">    <span class="keyword">public</span> <span class="keyword">void</span> <span class="title function_">bark</span><span class="params">()</span> &#123;</span><br><span class="line">        System.out.println(<span class="string">&quot;Dog bark...&quot;</span>);</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br><span class="line"></span><br><span class="line"><span class="keyword">public</span> <span class="keyword">class</span> <span class="title class_">Cat</span> <span class="keyword">implements</span> <span class="title class_">Animal</span> &#123;</span><br><span class="line">    <span class="meta">@Override</span></span><br><span class="line">    <span class="keyword">public</span> <span class="keyword">void</span> <span class="title function_">bark</span><span class="params">()</span> &#123;</span><br><span class="line">        System.out.println(<span class="string">&quot;Cat bark...&quot;</span>);</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+<h4 id="配置信息所在目录"><a href="#配置信息所在目录" class="headerlink" title="配置信息所在目录"></a>配置信息所在目录</h4><p>查看日志滚动的配置信息所在的目录：<code>ls /etc/logrotate.d/</code>。</p>
+<figure class="highlight console"><table><tr><td class="code"><pre><span class="line">alternatives  apport  apt  bootlog  btmp  dpkg  rsyslog  ubuntu-advantage-tools  ufw  unattended-upgrades  wtmp</span><br></pre></td></tr></table></figure>
 
-<p>在 <strong><code>META-INF/services</code></strong> 文件夹下创建一个文件，名称为 <code>Animal</code> 的全限定名 <code>com.moralok.dubbo.spi.test.Animal</code>，文件内容为实现类的全限定名，实现类的全限定名之间用换行符分隔。</p>
-<figure class="highlight plaintext"><table><tr><td class="code"><pre><span class="line">com.moralok.dubbo.spi.test.Dog</span><br><span class="line">com.moralok.dubbo.spi.test.Cat</span><br></pre></td></tr></table></figure>
+<h4 id="为-Nginx-新增配置"><a href="#为-Nginx-新增配置" class="headerlink" title="为 Nginx 新增配置"></a>为 Nginx 新增配置</h4><p>为 <code>Nginx</code> 新增日志滚动配置，<code>vim /etc/logrotate.d/nginx</code>。</p>
+<figure class="highlight plaintext"><table><tr><td class="code"><pre><span class="line">/path/to/your/nginx/logs/*.log &#123;</span><br><span class="line">    # 切换用户</span><br><span class="line">    su moralok moralok</span><br><span class="line">    # 每天滚动日志文件</span><br><span class="line">    daily</span><br><span class="line">    # 使用日期作为滚动日志文件的后缀</span><br><span class="line">    dateext</span><br><span class="line">    # 如果日志丢失，不报错继续滚动下一个日志</span><br><span class="line">    missingok</span><br><span class="line">    # 保留 31 个备份</span><br><span class="line">    rotate 31</span><br><span class="line">    # 不压缩</span><br><span class="line">    nocompress</span><br><span class="line">    # 整个日志组运行一次的脚本</span><br><span class="line">    sharedscripts</span><br><span class="line">    # 滚动后的处理</span><br><span class="line">    postrotate</span><br><span class="line">        # 重新打开日志文件        </span><br><span class="line">        docker exec nginx sh -c &quot;[ ! -f /var/run/nginx.pid ] || (kill -USR1 `docker exec nginx cat /var/run/nginx.pid`; echo &#x27;Successfully rotating nginx logs.&#x27;)&quot;</span><br><span class="line">    endscript</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
 
-<p>进行测试。</p>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">class</span> <span class="title class_">JavaSPITest</span> &#123;</span><br><span class="line">    <span class="meta">@Test</span></span><br><span class="line">    <span class="keyword">void</span> <span class="title function_">bark</span><span class="params">()</span> &#123;</span><br><span class="line">        System.out.println(<span class="string">&quot;Java SPI&quot;</span>);</span><br><span class="line">        System.out.println(<span class="string">&quot;============&quot;</span>);</span><br><span class="line">        ServiceLoader&lt;Animal&gt; serviceLoader = ServiceLoader.load(Animal.class);</span><br><span class="line">        serviceLoader.forEach(Animal::bark);</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+<h4 id="验证配置和测试"><a href="#验证配置和测试" class="headerlink" title="验证配置和测试"></a>验证配置和测试</h4><p>测试配置文件是否有错误，<code>logrotate -d /etc/logrotate.d/nginx</code>。</p>
+<p>强制滚动：<code>logrotate -f /etc/logrotate.d/nginx</code></p>
+<h2 id="一些坑"><a href="#一些坑" class="headerlink" title="一些坑"></a>一些坑</h2><h3 id="var-lib-logrotate-权限问题"><a href="#var-lib-logrotate-权限问题" class="headerlink" title="&#x2F;var&#x2F;lib&#x2F;logrotate&#x2F; 权限问题"></a>&#x2F;var&#x2F;lib&#x2F;logrotate&#x2F; 权限问题</h3><p>当你使用校验过配置文件的正确性后，尝试强制滚动时，可能会遇到报错。</p>
+<figure class="highlight console"><table><tr><td class="code"><pre><span class="line"><span class="meta prompt_">$ </span><span class="language-bash">logrotate -f /etc/logrotate.d/nginx</span> </span><br><span class="line">error: error creating output file /var/lib/logrotate/status.tmp: Permission denied</span><br></pre></td></tr></table></figure>
 
-<p>测试结果</p>
-<figure class="highlight console"><table><tr><td class="code"><pre><span class="line">Java SPI</span><br><span class="line">============</span><br><span class="line">Dog bark...</span><br><span class="line">Cat bark...</span><br></pre></td></tr></table></figure>
+<p>这是因为 logrotate 会在 <code>/var/lib/logrotate/</code> 目录下创建 <code>status</code> 文件。查看目录权限可知，需要以 <code>root</code> 身份运行 <code>logrotate</code>。</p>
+<figure class="highlight console"><table><tr><td class="code"><pre><span class="line"><span class="meta prompt_">$ </span><span class="language-bash">ll /var/lib/logrotate</span></span><br><span class="line">total 12</span><br><span class="line">drwxr-xr-x  2 root root 4096 Dec  2 08:35 ./</span><br><span class="line">drwxr-xr-x 44 root root 4096 Jun 26 09:02 ../</span><br><span class="line">-rw-r--r--  1 root root 1395 Dec  2 08:35 status</span><br></pre></td></tr></table></figure>
 
-<h3 id="Dubbo-SPI-示例"><a href="#Dubbo-SPI-示例" class="headerlink" title="Dubbo SPI 示例"></a>Dubbo SPI 示例</h3><p><code>Dubbo</code> 并未使用原生的 <code>Java SPI</code>，而是重新实现了一套功能更加强大的 <code>SPI</code> 机制。<code>Dubbo SPI</code> 的配置文件放在 <strong><code>META-INF/dubbo</code></strong> 文件夹下，名称仍然是接口的全限定名，但是内容是“名称-&gt;实现类的全限定名”的键值对，另外接口需要标注 <code>SPI</code> 注解。</p>
-<figure class="highlight plaintext"><table><tr><td class="code"><pre><span class="line">dog = com.moralok.dubbo.spi.test.Dog</span><br><span class="line">cat = com.moralok.dubbo.spi.test.Cat</span><br></pre></td></tr></table></figure>
+<p>事实上，<code>logrotate -d /etc/logrotate.d/nginx</code> 命令也会读取 <code>/var/lib/logrotate/status</code>，但是 <code>other</code> 对该目录也有 <code>r</code> 读取权限，所以没有报错。</p>
+<figure class="highlight console"><table><tr><td class="code"><pre><span class="line"><span class="meta prompt_">$ </span><span class="language-bash">logrotate -d /etc/logrotate.d/nginx</span> </span><br><span class="line">WARNING: logrotate in debug mode does nothing except printing debug messages!  Consider using verbose mode (-v) instead if this is not what you want.</span><br><span class="line"></span><br><span class="line">reading config file /etc/logrotate.d/nginx</span><br><span class="line">Reading state from file: /var/lib/logrotate/status</span><br><span class="line">...</span><br></pre></td></tr></table></figure>
 
-<p>进行测试。</p>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">class</span> <span class="title class_">DubboSPITest</span> &#123;</span><br><span class="line"></span><br><span class="line">    <span class="meta">@Test</span></span><br><span class="line">    <span class="keyword">void</span> <span class="title function_">bark</span><span class="params">()</span> &#123;</span><br><span class="line">        System.out.println(<span class="string">&quot;Dubbo SPI&quot;</span>);</span><br><span class="line">        System.out.println(<span class="string">&quot;============&quot;</span>);</span><br><span class="line">        ExtensionLoader&lt;Animal&gt; extensionLoader = ExtensionLoader.getExtensionLoader(Animal.class);</span><br><span class="line">        <span class="type">Animal</span> <span class="variable">dog</span> <span class="operator">=</span> extensionLoader.getExtension(<span class="string">&quot;dog&quot;</span>);</span><br><span class="line">        dog.bark();</span><br><span class="line">        <span class="type">Animal</span> <span class="variable">cat</span> <span class="operator">=</span> extensionLoader.getExtension(<span class="string">&quot;cat&quot;</span>);</span><br><span class="line">        cat.bark();</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+<h3 id="日志文件夹的权限"><a href="#日志文件夹的权限" class="headerlink" title="日志文件夹的权限"></a>日志文件夹的权限</h3><p>即使你使用 <code>root</code> 身份运行 <code>logrotate</code>，你可能还会遇到以下报错</p>
+<figure class="highlight console"><table><tr><td class="code"><pre><span class="line"><span class="meta prompt_">$ </span><span class="language-bash">logrotate -f /etc/logrotate.d/nginx</span> </span><br><span class="line">error: skipping &quot;/path/to/your/nginx/logs/*.log&quot; because parent directory has insecure permissions (It&#x27;s world writable or writable by group which is not &quot;root&quot;) Set &quot;su&quot; directive in config file to tell logrotate which user/group should be used for rotation.</span><br></pre></td></tr></table></figure>
 
-<p>测试结果</p>
-<figure class="highlight console"><table><tr><td class="code"><pre><span class="line">Dubbo SPI</span><br><span class="line">============</span><br><span class="line">Dog bark...</span><br><span class="line">Cat bark...</span><br></pre></td></tr></table></figure>
+<p>你需要在配置文件中，使用 <code>su &lt;user&gt; &lt;group&gt;</code> 指定日志所在文件夹所属的用户和组，<code>logrotate</code> 才能正确读写。</p>
+<h3 id="由宿主机还是容器主导"><a href="#由宿主机还是容器主导" class="headerlink" title="由宿主机还是容器主导"></a>由宿主机还是容器主导</h3><p>首先 <code>Nginx</code> 的日志文件夹通过挂载映射到宿主机，日志滚动既可以由宿主机主导，也可以由容器主导，不过不论如何我们都需要向 <code>Docker</code> 容器内的 <code>Nginx</code> 发送 <code>USR1</code> 信号。有人倾向于在容器内完成所有工作，和宿主机几乎完全隔离；我个人更青睐于由宿主机主导，因为容器内的环境并不总是拥有你想要使用的软件（除非你总是定制自己使用的镜像），甚至标准镜像往往非常精简。</p>
+<p>在 <code>logrotate</code> 配置中的 <code>postrotate</code> 部分添加脚本，使用 <code>docker exec</code> 在容器内执行命令，完成向 <code>Nginx</code> 发送信号的工作。脚本的处理逻辑大概是“如果存在 <code>/var/run/nginx.pid</code>，就执行 <code>kill -USR1 \`cat /var/run/nginx.pid\`</code> 命令，并打印成功的消息”。但是我看到很多文章中分享的配置类似下面这样：</p>
+<figure class="highlight shell"><table><tr><td class="code"><pre><span class="line">docker exec nginx sh -c &quot;if [ -f /var/run/nginx.pid ]; then kill -USR1 $(docker exec nginx cat /var/run/nginx.pid); fi&quot;</span><br><span class="line"></span><br><span class="line">docker exec nginx sh -c &quot;[ ! -f /var/run/nginx.pid ] || kill -USR1 `cat /var/run/nginx.pid`;&quot;</span><br></pre></td></tr></table></figure>
 
-<h2 id="Dubbo-获取扩展流程图"><a href="#Dubbo-获取扩展流程图" class="headerlink" title="Dubbo 获取扩展流程图"></a>Dubbo 获取扩展流程图</h2><img src="/2023/11/28/how-does-Dubbo-SPI-works/Pasted%20image%2020231129204920.png" class="" title="Dubbo 获取扩展流程图">
+<p>经过测试都会有以下报错，我不清楚是否大多是抓取发布的文章，也不清楚他们是否测试过，对于 <code>Shell</code> 脚本写得不多的我来说，半夜测试反复排查错误真是头昏脑胀。在我原先的理解里，<code>-c</code> 后面的脚本是整体发到容器内部执行的，后来我才意识到，我对脚本内部的命令在宿主机还是容器里执行的理解是错误的。</p>
+<figure class="highlight console"><table><tr><td class="code"><pre><span class="line">cat: /var/run/nginx.pid: No such file or directory</span><br></pre></td></tr></table></figure>
 
-<h2 id="Dubbo-SPI-源码分析"><a href="#Dubbo-SPI-源码分析" class="headerlink" title="Dubbo SPI 源码分析"></a>Dubbo SPI 源码分析</h2><h3 id="获取-ExtensionLoader"><a href="#获取-ExtensionLoader" class="headerlink" title="获取 ExtensionLoader"></a>获取 ExtensionLoader</h3><figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">private</span> <span class="keyword">static</span> <span class="keyword">final</span> ConcurrentMap&lt;Class&lt;?&gt;, ExtensionLoader&lt;?&gt;&gt; EXTENSION_LOADERS = <span class="keyword">new</span> <span class="title class_">ConcurrentHashMap</span>&lt;&gt;(<span class="number">64</span>);</span><br><span class="line"></span><br><span class="line"><span class="keyword">public</span> <span class="keyword">static</span> &lt;T&gt; ExtensionLoader&lt;T&gt; <span class="title function_">getExtensionLoader</span><span class="params">(Class&lt;T&gt; type)</span> &#123;</span><br><span class="line">    <span class="keyword">if</span> (type == <span class="literal">null</span>) &#123;</span><br><span class="line">        <span class="keyword">throw</span> <span class="keyword">new</span> <span class="title class_">IllegalArgumentException</span>(<span class="string">&quot;Extension type == null&quot;</span>);</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="keyword">if</span> (!type.isInterface()) &#123;</span><br><span class="line">        <span class="keyword">throw</span> <span class="keyword">new</span> <span class="title class_">IllegalArgumentException</span>(<span class="string">&quot;Extension type (&quot;</span> + type + <span class="string">&quot;) is not an interface!&quot;</span>);</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="keyword">if</span> (!withExtensionAnnotation(type)) &#123;</span><br><span class="line">        <span class="keyword">throw</span> <span class="keyword">new</span> <span class="title class_">IllegalArgumentException</span>(<span class="string">&quot;Extension type (&quot;</span> + type +</span><br><span class="line">                <span class="string">&quot;) is not an extension, because it is NOT annotated with @&quot;</span> + SPI.class.getSimpleName() + <span class="string">&quot;!&quot;</span>);</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 从缓存中获取，如果缓存未命中，则创建，保存到缓存并返回</span></span><br><span class="line">    ExtensionLoader&lt;T&gt; loader = (ExtensionLoader&lt;T&gt;) EXTENSION_LOADERS.get(type);</span><br><span class="line">    <span class="keyword">if</span> (loader == <span class="literal">null</span>) &#123;</span><br><span class="line">        EXTENSION_LOADERS.putIfAbsent(type, <span class="keyword">new</span> <span class="title class_">ExtensionLoader</span>&lt;T&gt;(type));</span><br><span class="line">        loader = (ExtensionLoader&lt;T&gt;) EXTENSION_LOADERS.get(type);</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="keyword">return</span> loader;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+<h3 id="继续写入旧日志文件"><a href="#继续写入旧日志文件" class="headerlink" title="继续写入旧日志文件"></a>继续写入旧日志文件</h3><p>在使用 <code>logrotate -f /etc/logrotate.d/nginx</code> 测试通过后的第二天，发现虽然创建了新的日志文件，但是 <code>Nginx</code> 继续写入到旧的日志文件。这不同于网上很多文章提到的“没有发送 <code>USR1</code> 信号给 <code>Nginx</code> ”的情况。</p>
+<p>尝试手动发送信号，观察效果。</p>
+<figure class="highlight shell"><table><tr><td class="code"><pre><span class="line">docker exec nginx sh -c &quot;kill -USR1 `docker exec nginx cat /var/run/nginx.pid`&quot;</span><br></pre></td></tr></table></figure>
 
-<p>这个方法包含了如下步骤：</p>
-<ol>
-<li>参数校验。</li>
-<li>从缓存 <code>EXTENSION_LOADERS</code> 中获取与拓展类对应的 <code>ExtensionLoader</code>，如果缓存未命中，则创建一个新的实例，保存到缓存并返回。</li>
-</ol>
+<p>发现虽然终止了继续写入到旧的文件，但是在宿主机读取日志时，提示没有权限。</p>
+<figure class="highlight console"><table><tr><td class="code"><pre><span class="line"><span class="meta prompt_">$ </span><span class="language-bash"><span class="built_in">cat</span> access.log</span></span><br><span class="line">cat: access.log: Permission denied</span><br></pre></td></tr></table></figure>
+
+<p>查看日志文件权限，发现不对劲。新建的 <code>access.log</code> 的权限为 <code>600</code>，所属用户从 <code>moralok</code> 变为 <code>systemd-resolve</code>，失去了只有所属用户才拥有的 <code>rw</code> 权限。</p>
 <blockquote>
-<p>“<strong>从缓存中获取，如果缓存未命中，则创建，保存到缓存并返回</strong>”，类似的 <code>getOrCreate</code> 的处理模式在 <code>Dubbo</code> 的源码中经常出现。</p>
+<p>此时虽然注意到没有成功创建新的 <code>error.log</code>，但是只是以为对于空的日志文件不滚动。并且在后续重现问题时发现此时其实可以在容器里看到日志开始写入新的日志文件。</p>
 </blockquote>
-<p><code>EXTENSION_LOADERS</code> 是 <code>ExtensionLoader</code> 的静态变量，保存了“拓展类-&gt;<code>ExtensionLoader</code>”的映射关系。</p>
-<h3 id="根据-name-获取-Extension"><a href="#根据-name-获取-Extension" class="headerlink" title="根据 name 获取 Extension"></a>根据 name 获取 Extension</h3><figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> T <span class="title function_">getExtension</span><span class="params">(String name)</span> &#123;</span><br><span class="line">    <span class="keyword">return</span> getExtension(name, <span class="literal">true</span>);</span><br><span class="line">&#125;</span><br><span class="line"></span><br><span class="line"><span class="keyword">public</span> T <span class="title function_">getExtension</span><span class="params">(String name, <span class="type">boolean</span> wrap)</span> &#123;</span><br><span class="line">    <span class="keyword">if</span> (StringUtils.isEmpty(name)) &#123;</span><br><span class="line">        <span class="keyword">throw</span> <span class="keyword">new</span> <span class="title class_">IllegalArgumentException</span>(<span class="string">&quot;Extension name == null&quot;</span>);</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="keyword">if</span> (<span class="string">&quot;true&quot;</span>.equals(name)) &#123;</span><br><span class="line">        <span class="comment">// 获取默认的拓展实现</span></span><br><span class="line">        <span class="keyword">return</span> getDefaultExtension();</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="comment">// Holder，用于持有目标对象</span></span><br><span class="line">    <span class="keyword">final</span> Holder&lt;Object&gt; holder = getOrCreateHolder(name);</span><br><span class="line">    <span class="comment">// 双重检查</span></span><br><span class="line">    <span class="type">Object</span> <span class="variable">instance</span> <span class="operator">=</span> holder.get();</span><br><span class="line">    <span class="keyword">if</span> (instance == <span class="literal">null</span>) &#123;</span><br><span class="line">        <span class="keyword">synchronized</span> (holder) &#123;</span><br><span class="line">            instance = holder.get();</span><br><span class="line">            <span class="keyword">if</span> (instance == <span class="literal">null</span>) &#123;</span><br><span class="line">                <span class="comment">// 创建拓展实例，设置到 holder 中。</span></span><br><span class="line">                instance = createExtension(name, wrap);</span><br><span class="line">                holder.set(instance);</span><br><span class="line">            &#125;</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="keyword">return</span> (T) instance;</span><br><span class="line">&#125;</span><br><span class="line"></span><br><span class="line"><span class="keyword">private</span> <span class="keyword">final</span> ConcurrentMap&lt;String, Holder&lt;Object&gt;&gt; cachedInstances = <span class="keyword">new</span> <span class="title class_">ConcurrentHashMap</span>&lt;&gt;();</span><br><span class="line"></span><br><span class="line"><span class="keyword">private</span> Holder&lt;Object&gt; <span class="title function_">getOrCreateHolder</span><span class="params">(String name)</span> &#123;</span><br><span class="line">    Holder&lt;Object&gt; holder = cachedInstances.get(name);</span><br><span class="line">    <span class="keyword">if</span> (holder == <span class="literal">null</span>) &#123;</span><br><span class="line">        cachedInstances.putIfAbsent(name, <span class="keyword">new</span> <span class="title class_">Holder</span>&lt;&gt;());</span><br><span class="line">        holder = cachedInstances.get(name);</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="keyword">return</span> holder;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+<figure class="highlight console"><table><tr><td class="code"><pre><span class="line"><span class="meta prompt_">$ </span><span class="language-bash">ll</span></span><br><span class="line">total 136</span><br><span class="line">drwxrwxr-x 2 moralok         moralok 4096 Dec  3 00:00 ./</span><br><span class="line">drwxrwxr-x 4 moralok         moralok 4096 Nov 30 17:25 ../</span><br><span class="line">-rw------- 1 moralok         moralok    0 Dec  3 00:00 access.log</span><br><span class="line">-rw-r--r-- 1 systemd-resolve root  109200 Dec  3 07:01 access.log-20231203</span><br><span class="line">-rw-r--r-- 1 systemd-resolve root       0 Dec  2 19:07 error.log</span><br></pre></td></tr></table></figure>
 
-<p>这个方法中获取 <code>Holder</code> 和获取拓展实例都是使用 <code>getOrCreate</code> 的模式。</p>
-<p><code>Holder</code> 用于持有拓展实例。<code>cachedInstances</code> 是 <code>ExtensionLoader</code> 的成员变量，保存了“<code>name-&gt;Holder</code>(拓展实例)”的映射关系。</p>
-<h3 id="创建-Extension"><a href="#创建-Extension" class="headerlink" title="创建 Extension"></a>创建 Extension</h3><figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">private</span> T <span class="title function_">createExtension</span><span class="params">(String name, <span class="type">boolean</span> wrap)</span> &#123;</span><br><span class="line">    <span class="comment">// 从配置文件中加载所有的拓展类，可得到“name-&gt;拓展实现类”的映射关系表</span></span><br><span class="line">    Class&lt;?&gt; clazz = getExtensionClasses().get(name);</span><br><span class="line">    <span class="keyword">if</span> (clazz == <span class="literal">null</span> || unacceptableExceptions.contains(name)) &#123;</span><br><span class="line">        <span class="keyword">throw</span> findException(name);</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="keyword">try</span> &#123;</span><br><span class="line">        <span class="comment">// 使用 getOrCreate 模式获取拓展实例</span></span><br><span class="line">        <span class="type">T</span> <span class="variable">instance</span> <span class="operator">=</span> (T) EXTENSION_INSTANCES.get(clazz);</span><br><span class="line">        <span class="keyword">if</span> (instance == <span class="literal">null</span>) &#123;</span><br><span class="line">            EXTENSION_INSTANCES.putIfAbsent(clazz, clazz.getDeclaredConstructor().newInstance());</span><br><span class="line">            instance = (T) EXTENSION_INSTANCES.get(clazz);</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="comment">// 向拓展实例中注入依赖</span></span><br><span class="line">        injectExtension(instance);</span><br><span class="line"></span><br><span class="line">        <span class="comment">// 是否包装默认为 true</span></span><br><span class="line">        <span class="keyword">if</span> (wrap) &#123;</span><br><span class="line"></span><br><span class="line">            List&lt;Class&lt;?&gt;&gt; wrapperClassesList = <span class="keyword">new</span> <span class="title class_">ArrayList</span>&lt;&gt;();</span><br><span class="line">            <span class="keyword">if</span> (cachedWrapperClasses != <span class="literal">null</span>) &#123;</span><br><span class="line">                wrapperClassesList.addAll(cachedWrapperClasses);</span><br><span class="line">                wrapperClassesList.sort(WrapperComparator.COMPARATOR);</span><br><span class="line">                Collections.reverse(wrapperClassesList);</span><br><span class="line">            &#125;</span><br><span class="line"></span><br><span class="line">            <span class="keyword">if</span> (CollectionUtils.isNotEmpty(wrapperClassesList)) &#123;</span><br><span class="line">                <span class="comment">// 遍历包装类</span></span><br><span class="line">                <span class="keyword">for</span> (Class&lt;?&gt; wrapperClass : wrapperClassesList) &#123;</span><br><span class="line">                    <span class="type">Wrapper</span> <span class="variable">wrapper</span> <span class="operator">=</span> wrapperClass.getAnnotation(Wrapper.class);</span><br><span class="line">                    <span class="comment">// 区别于旧版本：支持使用 Wrapper 注解进行匹配</span></span><br><span class="line">                    <span class="keyword">if</span> (wrapper == <span class="literal">null</span></span><br><span class="line">                            || (ArrayUtils.contains(wrapper.matches(), name) &amp;&amp; !ArrayUtils.contains(wrapper.mismatches(), name))) &#123;</span><br><span class="line">                        <span class="comment">// 如果有匹配的包装类，包装拓展实例</span></span><br><span class="line">                        instance = injectExtension((T) wrapperClass.getConstructor(type).newInstance(instance));</span><br><span class="line">                    &#125;</span><br><span class="line">                &#125;</span><br><span class="line">            &#125;</span><br><span class="line">        &#125;</span><br><span class="line"></span><br><span class="line">        <span class="comment">// 初始化拓展实例</span></span><br><span class="line">        initExtension(instance);</span><br><span class="line">        <span class="keyword">return</span> instance;</span><br><span class="line">    &#125; <span class="keyword">catch</span> (Throwable t) &#123;</span><br><span class="line">        <span class="keyword">throw</span> <span class="keyword">new</span> <span class="title class_">IllegalStateException</span>(<span class="string">&quot;Extension instance (name: &quot;</span> + name + <span class="string">&quot;, class: &quot;</span> +</span><br><span class="line">                type + <span class="string">&quot;) couldn&#x27;t be instantiated: &quot;</span> + t.getMessage(), t);</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
-
-<p>这个方法包含如下步骤：</p>
-<ol>
-<li>通过 <code>getExtensionClasses</code> 获取所有拓展类</li>
-<li>通过反射创建拓展实例</li>
-<li>向拓展实例中注入依赖</li>
-<li>将拓展实例包装在适配的 <code>Wrapper</code> 对象中</li>
-<li>初始化拓展实例</li>
-</ol>
-<p>第一步是加载拓展类的关键，第三步和第四步是 <strong><code>Dubbo IOC</code></strong> 和 <strong><code>AOP</code></strong> 的具体实现。</p>
-<p>最后拓展实例的结构如下图。</p>
-<img src="/2023/11/28/how-does-Dubbo-SPI-works/Pasted%20image%2020231129024723.png" class="" title="拓展实例被包装后的结构图">
-
-<h3 id="加载-Extension-Class"><a href="#加载-Extension-Class" class="headerlink" title="加载 Extension Class"></a>加载 Extension Class</h3><figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">private</span> Map&lt;String, Class&lt;?&gt;&gt; getExtensionClasses() &#123;</span><br><span class="line">    <span class="comment">// 使用 getOrCreate 模式获取所有拓展类</span></span><br><span class="line">    Map&lt;String, Class&lt;?&gt;&gt; classes = cachedClasses.get();</span><br><span class="line">    <span class="keyword">if</span> (classes == <span class="literal">null</span>) &#123;</span><br><span class="line">        <span class="keyword">synchronized</span> (cachedClasses) &#123;</span><br><span class="line">            classes = cachedClasses.get();</span><br><span class="line">            <span class="keyword">if</span> (classes == <span class="literal">null</span>) &#123;</span><br><span class="line">                classes = loadExtensionClasses();</span><br><span class="line">                cachedClasses.set(classes);</span><br><span class="line">            &#125;</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="keyword">return</span> classes;</span><br><span class="line">&#125;</span><br><span class="line"></span><br><span class="line"><span class="keyword">private</span> Map&lt;String, Class&lt;?&gt;&gt; loadExtensionClasses() &#123;</span><br><span class="line">    <span class="comment">// 1. 缓存默认拓展名</span></span><br><span class="line">    cacheDefaultExtensionName();</span><br><span class="line"></span><br><span class="line">    Map&lt;String, Class&lt;?&gt;&gt; extensionClasses = <span class="keyword">new</span> <span class="title class_">HashMap</span>&lt;&gt;();</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 遍历加载策略，加载各个策略的目录下的配置文件，获取拓展类</span></span><br><span class="line">    <span class="keyword">for</span> (LoadingStrategy strategy : strategies) &#123;</span><br><span class="line">        loadDirectory(extensionClasses, strategy.directory(), type.getName(), strategy.preferExtensionClassLoader(),</span><br><span class="line">                strategy.overridden(), strategy.excludedPackages());</span><br><span class="line">        loadDirectory(extensionClasses, strategy.directory(), type.getName().replace(<span class="string">&quot;org.apache&quot;</span>, <span class="string">&quot;com.alibaba&quot;</span>),</span><br><span class="line">                strategy.preferExtensionClassLoader(), strategy.overridden(), strategy.excludedPackages());</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">return</span> extensionClasses;</span><br><span class="line">&#125;</span><br><span class="line"></span><br><span class="line"><span class="comment">// 如果存在默认拓展名，提取并缓存</span></span><br><span class="line"><span class="keyword">private</span> <span class="keyword">void</span> <span class="title function_">cacheDefaultExtensionName</span><span class="params">()</span> &#123;</span><br><span class="line">    <span class="comment">// 获取 SPI 注解</span></span><br><span class="line">    <span class="keyword">final</span> <span class="type">SPI</span> <span class="variable">defaultAnnotation</span> <span class="operator">=</span> type.getAnnotation(SPI.class);</span><br><span class="line">    <span class="keyword">if</span> (defaultAnnotation == <span class="literal">null</span>) &#123;</span><br><span class="line">        <span class="keyword">return</span>;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="type">String</span> <span class="variable">value</span> <span class="operator">=</span> defaultAnnotation.value();</span><br><span class="line">    <span class="keyword">if</span> ((value = value.trim()).length() &gt; <span class="number">0</span>) &#123;</span><br><span class="line">        <span class="comment">// 对 SPI 的 value 内容进行切分</span></span><br><span class="line">        String[] names = NAME_SEPARATOR.split(value);</span><br><span class="line">        <span class="comment">// 检测 name 是否合法</span></span><br><span class="line">        <span class="keyword">if</span> (names.length &gt; <span class="number">1</span>) &#123;</span><br><span class="line">            <span class="keyword">throw</span> <span class="keyword">new</span> <span class="title class_">IllegalStateException</span>(<span class="string">&quot;More than 1 default extension name on extension &quot;</span> + type.getName()</span><br><span class="line">                    + <span class="string">&quot;: &quot;</span> + Arrays.toString(names));</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="keyword">if</span> (names.length == <span class="number">1</span>) &#123;</span><br><span class="line">            <span class="comment">// 缓存默认拓展名，用于 getDefaultExtension</span></span><br><span class="line">            cachedDefaultName = names[<span class="number">0</span>];</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
-
-<h4 id="依次处理特定目录"><a href="#依次处理特定目录" class="headerlink" title="依次处理特定目录"></a>依次处理特定目录</h4><p>代码参考旧版本更容易理解。处理过程在本质上就是依次加载 <code>META-INF/dubbo/internal/</code>、<code>META-INF/dubbo/</code>、<code>META-INF/services/</code> 三个目录下的配置文件，获取拓展类。</p>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line">loadDirectory(extensionClasses, DUBBO_INTERNAL_DIRECTORY);</span><br><span class="line">loadDirectory(extensionClasses, DUBBO_DIRECTORY);</span><br><span class="line">loadDirectory(extensionClasses, SERVICES_DIRECTORY);</span><br></pre></td></tr></table></figure>
-
-<p>新版本使用原生的 <code>Java SPI</code> 加载 <code>LoadingStrategy</code>，允许用户自定义加载策略。</p>
-<ol>
-<li><code>DubboInternalLoadingStrategy</code>，目录 <code>META-INF/dubbo/internal/</code>，优先级最高</li>
-<li><code>DubboLoadingStrategy</code>，目录 <code>META-INF/dubbo/</code>，优先级普通</li>
-<li><code>ServicesLoadingStrategy</code>，目录 <code>META-INF/services/</code>，优先级最低</li>
-</ol>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">private</span> <span class="keyword">static</span> <span class="keyword">volatile</span> LoadingStrategy[] strategies = loadLoadingStrategies();</span><br><span class="line"></span><br><span class="line"><span class="keyword">private</span> <span class="keyword">static</span> LoadingStrategy[] loadLoadingStrategies() &#123;</span><br><span class="line">    <span class="comment">// 通过 Java SPI 加载 LoadingStrategy </span></span><br><span class="line">    <span class="keyword">return</span> stream(load(LoadingStrategy.class).spliterator(), <span class="literal">false</span>)</span><br><span class="line">            .sorted()</span><br><span class="line">            .toArray(LoadingStrategy[]::<span class="keyword">new</span>);</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
-
-<p><code>LoadingStrategy</code> 的 <code>Java SPI</code> 配置文件</p>
-<img src="/2023/11/28/how-does-Dubbo-SPI-works/Snipaste_2023-11-29_03-25-54.png" class="" title="LoadingStrategy 的 Java SPI 配置文件">
-
-<h4 id="loadDirectory-方法"><a href="#loadDirectory-方法" class="headerlink" title="loadDirectory 方法"></a>loadDirectory 方法</h4><p><code>loadDirectory</code> 方法先通过 <code>classLoader</code> 获取所有的资源链接，然后再通过 <code>loadResource</code> 方法加载资源。</p>
-<p>新版本中 <code>extensionLoaderClassLoaderFirst</code> 可以设置是否优先使用 <code>ExtensionLoader&#39;s ClassLoader</code> 获取资源链接。</p>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">private</span> <span class="keyword">void</span> <span class="title function_">loadDirectory</span><span class="params">(Map&lt;String, Class&lt;?&gt;&gt; extensionClasses, String dir, String type,</span></span><br><span class="line"><span class="params">                            <span class="type">boolean</span> extensionLoaderClassLoaderFirst, <span class="type">boolean</span> overridden, String... excludedPackages)</span> &#123;</span><br><span class="line">    <span class="comment">// filename = 文件夹路径 + type 的全限定名</span></span><br><span class="line">    <span class="type">String</span> <span class="variable">fileName</span> <span class="operator">=</span> dir + type;</span><br><span class="line">    <span class="keyword">try</span> &#123;</span><br><span class="line">        Enumeration&lt;java.net.URL&gt; urls = <span class="literal">null</span>;</span><br><span class="line">        <span class="type">ClassLoader</span> <span class="variable">classLoader</span> <span class="operator">=</span> findClassLoader();</span><br><span class="line"></span><br><span class="line">        <span class="comment">// 区别于旧版本：先从 ExtensionLoader&#x27;s ClassLoader 获取资源链接，默认为 false</span></span><br><span class="line">        <span class="keyword">if</span> (extensionLoaderClassLoaderFirst) &#123;</span><br><span class="line">            <span class="type">ClassLoader</span> <span class="variable">extensionLoaderClassLoader</span> <span class="operator">=</span> ExtensionLoader.class.getClassLoader();</span><br><span class="line">            <span class="keyword">if</span> (ClassLoader.getSystemClassLoader() != extensionLoaderClassLoader) &#123;</span><br><span class="line">                urls = extensionLoaderClassLoader.getResources(fileName);</span><br><span class="line">            &#125;</span><br><span class="line">        &#125;</span><br><span class="line"></span><br><span class="line">        <span class="comment">// 根据文件名加载所有同名文件</span></span><br><span class="line">        <span class="keyword">if</span> (urls == <span class="literal">null</span> || !urls.hasMoreElements()) &#123;</span><br><span class="line">            <span class="keyword">if</span> (classLoader != <span class="literal">null</span>) &#123;</span><br><span class="line">                urls = classLoader.getResources(fileName);</span><br><span class="line">            &#125; <span class="keyword">else</span> &#123;</span><br><span class="line">                urls = ClassLoader.getSystemResources(fileName);</span><br><span class="line">            &#125;</span><br><span class="line">        &#125;</span><br><span class="line"></span><br><span class="line">        <span class="keyword">if</span> (urls != <span class="literal">null</span>) &#123;</span><br><span class="line">            <span class="keyword">while</span> (urls.hasMoreElements()) &#123;</span><br><span class="line">                java.net.<span class="type">URL</span> <span class="variable">resourceURL</span> <span class="operator">=</span> urls.nextElement();</span><br><span class="line">                <span class="comment">// 加载资源</span></span><br><span class="line">                loadResource(extensionClasses, classLoader, resourceURL, overridden, excludedPackages);</span><br><span class="line">            &#125;</span><br><span class="line">        &#125;</span><br><span class="line">    &#125; <span class="keyword">catch</span> (Throwable t) &#123;</span><br><span class="line">        logger.error(<span class="string">&quot;Exception occurred when loading extension class (interface: &quot;</span> +</span><br><span class="line">                type + <span class="string">&quot;, description file: &quot;</span> + fileName + <span class="string">&quot;).&quot;</span>, t);</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
-
-<h4 id="loadResource-方法"><a href="#loadResource-方法" class="headerlink" title="loadResource 方法"></a>loadResource 方法</h4><p><code>loadResource</code> 方法用于读取和解析配置文件，并通过反射加载类，最后调用 <code>loadClass</code> 方法进行其他操作。<code>loadClass</code> 方法用于操作缓存。</p>
-<p>新版本中 <code>excludedPackages</code> 可以设置将指定包内的类都排除。</p>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">private</span> <span class="keyword">void</span> <span class="title function_">loadResource</span><span class="params">(Map&lt;String, Class&lt;?&gt;&gt; extensionClasses, ClassLoader classLoader,</span></span><br><span class="line"><span class="params">                            java.net.URL resourceURL, <span class="type">boolean</span> overridden, String... excludedPackages)</span> &#123;</span><br><span class="line">    <span class="keyword">try</span> &#123;</span><br><span class="line">        <span class="keyword">try</span> (<span class="type">BufferedReader</span> <span class="variable">reader</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">BufferedReader</span>(<span class="keyword">new</span> <span class="title class_">InputStreamReader</span>(resourceURL.openStream(), StandardCharsets.UTF_8))) &#123;</span><br><span class="line">            String line;</span><br><span class="line">            <span class="type">String</span> <span class="variable">clazz</span> <span class="operator">=</span> <span class="literal">null</span>;</span><br><span class="line">            <span class="comment">// 按行读取配置内容</span></span><br><span class="line">            <span class="keyword">while</span> ((line = reader.readLine()) != <span class="literal">null</span>) &#123;</span><br><span class="line">                <span class="comment">// 定位 # 字符，截取 # 字符之前的内容，# 字符之后的内容为注释，需要忽略</span></span><br><span class="line">                <span class="keyword">final</span> <span class="type">int</span> <span class="variable">ci</span> <span class="operator">=</span> line.indexOf(<span class="string">&#x27;#&#x27;</span>);</span><br><span class="line">                <span class="keyword">if</span> (ci &gt;= <span class="number">0</span>) &#123;</span><br><span class="line">                    line = line.substring(<span class="number">0</span>, ci);</span><br><span class="line">                &#125;</span><br><span class="line">                line = line.trim();</span><br><span class="line">                <span class="keyword">if</span> (line.length() &gt; <span class="number">0</span>) &#123;</span><br><span class="line">                    <span class="keyword">try</span> &#123;</span><br><span class="line">                        <span class="type">String</span> <span class="variable">name</span> <span class="operator">=</span> <span class="literal">null</span>;</span><br><span class="line">                        <span class="comment">// 定位 = 字符，以 = 字符为界，截取键值对</span></span><br><span class="line">                        <span class="type">int</span> <span class="variable">i</span> <span class="operator">=</span> line.indexOf(<span class="string">&#x27;=&#x27;</span>);</span><br><span class="line">                        <span class="keyword">if</span> (i &gt; <span class="number">0</span>) &#123;</span><br><span class="line">                            name = line.substring(<span class="number">0</span>, i).trim();</span><br><span class="line">                            clazz = line.substring(i + <span class="number">1</span>).trim();</span><br><span class="line">                        &#125; <span class="keyword">else</span> &#123;</span><br><span class="line">                            clazz = line;</span><br><span class="line">                        &#125;</span><br><span class="line">                        <span class="keyword">if</span> (StringUtils.isNotEmpty(clazz) &amp;&amp; !isExcluded(clazz, excludedPackages)) &#123;</span><br><span class="line">                            <span class="comment">// 加载类，并通过 loadClass 进行缓存</span></span><br><span class="line">                            <span class="comment">// 区别于旧版本：根据 excludedPackages 判断是否排除</span></span><br><span class="line">                            loadClass(extensionClasses, resourceURL, Class.forName(clazz, <span class="literal">true</span>, classLoader), name, overridden);</span><br><span class="line">                        &#125;</span><br><span class="line">                    &#125; <span class="keyword">catch</span> (Throwable t) &#123;</span><br><span class="line">                        <span class="type">IllegalStateException</span> <span class="variable">e</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">IllegalStateException</span>(</span><br><span class="line">                                <span class="string">&quot;Failed to load extension class (interface: &quot;</span> + type + <span class="string">&quot;, class line: &quot;</span> + line + <span class="string">&quot;) in &quot;</span> + resourceURL +</span><br><span class="line">                                        <span class="string">&quot;, cause: &quot;</span> + t.getMessage(), t);</span><br><span class="line">                        exceptions.put(line, e);</span><br><span class="line">                    &#125;</span><br><span class="line">                &#125;</span><br><span class="line">            &#125;</span><br><span class="line">        &#125;</span><br><span class="line">    &#125; <span class="keyword">catch</span> (Throwable t) &#123;</span><br><span class="line">        logger.error(<span class="string">&quot;Exception occurred when loading extension class (interface: &quot;</span> +</span><br><span class="line">                type + <span class="string">&quot;, class file: &quot;</span> + resourceURL + <span class="string">&quot;) in &quot;</span> + resourceURL, t);</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
-
-<h4 id="loadClass-方法"><a href="#loadClass-方法" class="headerlink" title="loadClass 方法"></a>loadClass 方法</h4><p><code>loadClass</code> 方法设置了多个缓存，比如 <code>cachedAdaptiveClass</code>、<code>cachedWrapperClasses</code>、<code>cachedNames</code> 和 <code>cachedClasses</code>。</p>
-<p>新版本中 <code>overridden</code> 可以设置是否覆盖 <code>cachedAdaptiveClass</code>、<code>cachedClasses</code> 的 <code>name-&gt;clazz</code>。</p>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">private</span> <span class="keyword">void</span> <span class="title function_">loadClass</span><span class="params">(Map&lt;String, Class&lt;?&gt;&gt; extensionClasses, java.net.URL resourceURL, Class&lt;?&gt; clazz, String name,</span></span><br><span class="line"><span class="params">                        <span class="type">boolean</span> overridden)</span> <span class="keyword">throws</span> NoSuchMethodException &#123;</span><br><span class="line">    <span class="comment">// 检测 clazz 是否合法</span></span><br><span class="line">    <span class="keyword">if</span> (!type.isAssignableFrom(clazz)) &#123;</span><br><span class="line">        <span class="keyword">throw</span> <span class="keyword">new</span> <span class="title class_">IllegalStateException</span>(<span class="string">&quot;Error occurred when loading extension class (interface: &quot;</span> +</span><br><span class="line">                type + <span class="string">&quot;, class line: &quot;</span> + clazz.getName() + <span class="string">&quot;), class &quot;</span></span><br><span class="line">                + clazz.getName() + <span class="string">&quot; is not subtype of interface.&quot;</span>);</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="keyword">if</span> (clazz.isAnnotationPresent(Adaptive.class)) &#123;</span><br><span class="line">        <span class="comment">// 检测 clazz 是否有 Adaptive 注解，有则设置 cachedAdaptiveClass 缓存</span></span><br><span class="line">        <span class="comment">// 区别于旧版本：根据 overriden 判断是否可覆盖</span></span><br><span class="line">        cacheAdaptiveClass(clazz, overridden);</span><br><span class="line">    &#125; <span class="keyword">else</span> <span class="keyword">if</span> (isWrapperClass(clazz)) &#123;</span><br><span class="line">        <span class="comment">// 检测 clazz 是否是 Wrapper 类型，是则添加到 cachedWrapperClasses 缓存</span></span><br><span class="line">        cacheWrapperClass(clazz);</span><br><span class="line">    &#125; <span class="keyword">else</span> &#123;</span><br><span class="line">        <span class="comment">// 检测 clazz 是否有默认的构造器方法，如果没有，则抛出异常</span></span><br><span class="line">        clazz.getConstructor();</span><br><span class="line">        <span class="keyword">if</span> (StringUtils.isEmpty(name)) &#123;</span><br><span class="line">            <span class="comment">// 如果 name 为空，则尝试从 Extension 注解中获取 name，或者使用小写的类名（可能截取 type 后缀）作为 name</span></span><br><span class="line">            name = findAnnotationName(clazz);</span><br><span class="line">            <span class="keyword">if</span> (name.length() == <span class="number">0</span>) &#123;</span><br><span class="line">                <span class="keyword">throw</span> <span class="keyword">new</span> <span class="title class_">IllegalStateException</span>(</span><br><span class="line">                        <span class="string">&quot;No such extension name for the class &quot;</span> + clazz.getName() + <span class="string">&quot; in the config &quot;</span> + resourceURL);</span><br><span class="line">            &#125;</span><br><span class="line">        &#125;</span><br><span class="line"></span><br><span class="line">        <span class="comment">// 切分 name</span></span><br><span class="line">        String[] names = NAME_SEPARATOR.split(name);</span><br><span class="line">        <span class="keyword">if</span> (ArrayUtils.isNotEmpty(names)) &#123;</span><br><span class="line">            <span class="comment">// 如果 clazz 有 Activate 注解，则缓存 names[0]-&gt;Activate 的映射关系</span></span><br><span class="line">            cacheActivateClass(clazz, names[<span class="number">0</span>]);</span><br><span class="line">            <span class="keyword">for</span> (String n : names) &#123;</span><br><span class="line">                <span class="comment">// 缓存 clazz-&gt;n 的映射关系</span></span><br><span class="line">                cacheName(clazz, n);</span><br><span class="line">                <span class="comment">// 缓存 n-&gt;clazz 的映射关系，传递到最后，终于轮到 extensionClasses</span></span><br><span class="line">                <span class="comment">// 区别于旧版本：根据 overriden 判断是否可覆盖</span></span><br><span class="line">                saveInExtensionClass(extensionClasses, clazz, n, overridden);</span><br><span class="line">            &#125;</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br><span class="line"></span><br><span class="line"><span class="keyword">private</span> <span class="keyword">void</span> <span class="title function_">cacheAdaptiveClass</span><span class="params">(Class&lt;?&gt; clazz, <span class="type">boolean</span> overridden)</span> &#123;</span><br><span class="line">    <span class="keyword">if</span> (cachedAdaptiveClass == <span class="literal">null</span> || overridden) &#123;</span><br><span class="line">        <span class="comment">// 可以设置是否覆盖</span></span><br><span class="line">        cachedAdaptiveClass = clazz;</span><br><span class="line">    &#125; <span class="keyword">else</span> <span class="keyword">if</span> (!cachedAdaptiveClass.equals(clazz)) &#123;</span><br><span class="line">        <span class="keyword">throw</span> <span class="keyword">new</span> <span class="title class_">IllegalStateException</span>(<span class="string">&quot;More than 1 adaptive class found: &quot;</span></span><br><span class="line">                + cachedAdaptiveClass.getName()</span><br><span class="line">                + <span class="string">&quot;, &quot;</span> + clazz.getName());</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br><span class="line"></span><br><span class="line"><span class="keyword">private</span> <span class="keyword">void</span> <span class="title function_">cacheWrapperClass</span><span class="params">(Class&lt;?&gt; clazz)</span> &#123;</span><br><span class="line">    <span class="keyword">if</span> (cachedWrapperClasses == <span class="literal">null</span>) &#123;</span><br><span class="line">        cachedWrapperClasses = <span class="keyword">new</span> <span class="title class_">ConcurrentHashSet</span>&lt;&gt;();</span><br><span class="line">    &#125;</span><br><span class="line">    cachedWrapperClasses.add(clazz);</span><br><span class="line">&#125;</span><br><span class="line"></span><br><span class="line"><span class="keyword">private</span> <span class="keyword">void</span> <span class="title function_">cacheActivateClass</span><span class="params">(Class&lt;?&gt; clazz, String name)</span> &#123;</span><br><span class="line">    <span class="type">Activate</span> <span class="variable">activate</span> <span class="operator">=</span> clazz.getAnnotation(Activate.class);</span><br><span class="line">    <span class="keyword">if</span> (activate != <span class="literal">null</span>) &#123;</span><br><span class="line">        cachedActivates.put(name, activate);</span><br><span class="line">    &#125; <span class="keyword">else</span> &#123;</span><br><span class="line">        <span class="comment">// support com.alibaba.dubbo.common.extension.Activate</span></span><br><span class="line">        com.alibaba.dubbo.common.extension.<span class="type">Activate</span> <span class="variable">oldActivate</span> <span class="operator">=</span></span><br><span class="line">                clazz.getAnnotation(com.alibaba.dubbo.common.extension.Activate.class);</span><br><span class="line">        <span class="keyword">if</span> (oldActivate != <span class="literal">null</span>) &#123;</span><br><span class="line">            cachedActivates.put(name, oldActivate);</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
-
-<h3 id="Dubbo-IOC"><a href="#Dubbo-IOC" class="headerlink" title="Dubbo IOC"></a>Dubbo IOC</h3><p><code>Dubbo IOC</code> 是通过 <code>setter</code> 方法注入依赖。<code>Dubbo</code> 首先通过反射获取目标类的所有方法，然后遍历方法列表，检测方法名是否具有 <code>setter</code> 方法特征并满足条件，若有，则通过 <code>objectFactory</code> 获取依赖对象，最后通过反射调用 <code>setter</code> 方法将依赖设置到目标对象中。</p>
-<blockquote>
-<p>与 <code>Spring IOC</code> 相比，<code>Dubbo IOC</code> 实现的依赖注入功能更加简单，代码也更加容易理解。</p>
-</blockquote>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">private</span> T <span class="title function_">injectExtension</span><span class="params">(T instance)</span> &#123;</span><br><span class="line">    <span class="comment">// 检测是否有 objectFactory</span></span><br><span class="line">    <span class="keyword">if</span> (objectFactory == <span class="literal">null</span>) &#123;</span><br><span class="line">        <span class="keyword">return</span> instance;</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="keyword">try</span> &#123;</span><br><span class="line">        <span class="comment">// 遍历目标类的所有方法</span></span><br><span class="line">        <span class="comment">// 区别于旧版本：增加了对 DisbaleInject、Inject 注解的处理</span></span><br><span class="line">        <span class="keyword">for</span> (Method method : instance.getClass().getMethods()) &#123;</span><br><span class="line">            <span class="comment">// 检测是否是 setter 方法</span></span><br><span class="line">            <span class="keyword">if</span> (!isSetter(method)) &#123;</span><br><span class="line">                <span class="keyword">continue</span>;</span><br><span class="line">            &#125;</span><br><span class="line"></span><br><span class="line">            <span class="comment">// 检测是否标注 DisableInject 注解</span></span><br><span class="line">            <span class="keyword">if</span> (method.getAnnotation(DisableInject.class) != <span class="literal">null</span>) &#123;</span><br><span class="line">                <span class="keyword">continue</span>;</span><br><span class="line">            &#125;</span><br><span class="line"></span><br><span class="line">            <span class="comment">// 检测参数类型是否是原始类型</span></span><br><span class="line">            Class&lt;?&gt; pt = method.getParameterTypes()[<span class="number">0</span>];</span><br><span class="line">            <span class="keyword">if</span> (ReflectUtils.isPrimitives(pt)) &#123;</span><br><span class="line">                <span class="keyword">continue</span>;</span><br><span class="line">            &#125;</span><br><span class="line"></span><br><span class="line">            <span class="comment">// 获取属性名</span></span><br><span class="line">            <span class="type">String</span> <span class="variable">property</span> <span class="operator">=</span> getSetterProperty(method);</span><br><span class="line">            <span class="comment">// 检测是否标注 Inject 注解</span></span><br><span class="line">            <span class="type">Inject</span> <span class="variable">inject</span> <span class="operator">=</span> method.getAnnotation(Inject.class);</span><br><span class="line">            <span class="keyword">if</span> (inject == <span class="literal">null</span>) &#123;</span><br><span class="line">                injectValue(instance, method, pt, property);</span><br><span class="line">            &#125; <span class="keyword">else</span> &#123;</span><br><span class="line">                <span class="comment">// 检测 Inject 是否启动、是否按照类型注入</span></span><br><span class="line">                <span class="keyword">if</span> (!inject.enable()) &#123;</span><br><span class="line">                    <span class="keyword">continue</span>;</span><br><span class="line">                &#125;</span><br><span class="line"></span><br><span class="line">                <span class="keyword">if</span> (inject.type() == Inject.InjectType.ByType) &#123;</span><br><span class="line">                    injectValue(instance, method, pt, <span class="literal">null</span>);</span><br><span class="line">                &#125; <span class="keyword">else</span> &#123;</span><br><span class="line">                    injectValue(instance, method, pt, property);</span><br><span class="line">                &#125;</span><br><span class="line">            &#125;</span><br><span class="line">        &#125;</span><br><span class="line">    &#125; <span class="keyword">catch</span> (Exception e) &#123;</span><br><span class="line">        logger.error(e.getMessage(), e);</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="keyword">return</span> instance;</span><br><span class="line">&#125;</span><br><span class="line"></span><br><span class="line"><span class="comment">// 获取属性名</span></span><br><span class="line"><span class="keyword">private</span> String <span class="title function_">getSetterProperty</span><span class="params">(Method method)</span> &#123;</span><br><span class="line">    <span class="keyword">return</span> method.getName().length() &gt; <span class="number">3</span> ? method.getName().substring(<span class="number">3</span>, <span class="number">4</span>).toLowerCase() + method.getName().substring(<span class="number">4</span>) : <span class="string">&quot;&quot;</span>;</span><br><span class="line">&#125;</span><br><span class="line"></span><br><span class="line"><span class="comment">// public、set 开头、只有一个参数</span></span><br><span class="line"><span class="keyword">private</span> <span class="type">boolean</span> <span class="title function_">isSetter</span><span class="params">(Method method)</span> &#123;</span><br><span class="line">    <span class="keyword">return</span> method.getName().startsWith(<span class="string">&quot;set&quot;</span>)</span><br><span class="line">            &amp;&amp; method.getParameterTypes().length == <span class="number">1</span></span><br><span class="line">            &amp;&amp; Modifier.isPublic(method.getModifiers());</span><br><span class="line">&#125;</span><br><span class="line"></span><br><span class="line"><span class="keyword">private</span> <span class="keyword">void</span> <span class="title function_">injectValue</span><span class="params">(T instance, Method method, Class&lt;?&gt; pt, String property)</span> &#123;</span><br><span class="line">    <span class="keyword">try</span> &#123;</span><br><span class="line">        <span class="comment">// 从 ObjectFactory 中获取依赖对象</span></span><br><span class="line">        <span class="type">Object</span> <span class="variable">object</span> <span class="operator">=</span> objectFactory.getExtension(pt, property);</span><br><span class="line">        <span class="keyword">if</span> (object != <span class="literal">null</span>) &#123;</span><br><span class="line">            <span class="comment">// 通过反射调用 setter 方法设置依赖</span></span><br><span class="line">            method.invoke(instance, object);</span><br><span class="line">        &#125;</span><br><span class="line">    &#125; <span class="keyword">catch</span> (Exception e) &#123;</span><br><span class="line">        logger.error(<span class="string">&quot;Failed to inject via method &quot;</span> + method.getName()</span><br><span class="line">                + <span class="string">&quot; of interface &quot;</span> + type.getName() + <span class="string">&quot;: &quot;</span> + e.getMessage(), e);</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
-
-<p><code>objectFactory</code> 是 <code>ExtensionFactory</code> 的自适应拓展，通过它获取依赖对象，本质上是根据目标拓展类获取 <code>ExtensionLoader</code>，然后获取其自适应拓展，过程代码如下。具体我们不再深入分析，可以参考<a href="/2023/11/29/how-does-Dubbo-SPI-adaptive-extension-works/" title="Dubbo SPI 自适应拓展的工作原理">Dubbo SPI 自适应拓展的工作原理</a>。</p>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> &lt;T&gt; T <span class="title function_">getExtension</span><span class="params">(Class&lt;T&gt; type, String name)</span> &#123;</span><br><span class="line">    <span class="keyword">if</span> (type.isInterface() &amp;&amp; type.isAnnotationPresent(SPI.class)) &#123;</span><br><span class="line">        ExtensionLoader&lt;T&gt; loader = ExtensionLoader.getExtensionLoader(type);</span><br><span class="line">        <span class="keyword">if</span> (!loader.getSupportedExtensions().isEmpty()) &#123;</span><br><span class="line">            <span class="keyword">return</span> loader.getAdaptiveExtension();</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="keyword">return</span> <span class="literal">null</span>;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
-
-<h2 id="参考文章"><a href="#参考文章" class="headerlink" title="参考文章"></a>参考文章</h2><ul>
-<li><a href="https://cn.dubbo.apache.org/zh-cn/docsv2.7/dev/source/dubbo-spi/">Dubbo SPI</a></li>
-</ul>
-]]></content>
-      <tags>
-        <tag>java</tag>
-        <tag>dubbo</tag>
-        <tag>spi</tag>
-      </tags>
-  </entry>
-  <entry>
-    <title>Nginx 反向代理在家庭网络中的应用</title>
-    <url>/2023/12/01/Nginx-reverse-proxy-for-home-networks/</url>
-    <content><![CDATA[<p>原先在使用 <code>Cloudflare Tunnel</code> 访问家庭网络中的服务时，是直接将域名解析到相应服务。尽管 <code>Cloudflare</code> 已经提供相关的请求统计和安全防护功能，部分服务自身也有访问日志，但是为了更好地监控和跟踪对外服务的使用情况，采集 <code>Cloudlfare</code> 统计中缺少的新，决定使用 <code>Nginx</code> 反向代理内部服务，统一内部服务的访问入口。简而言之就是，又折腾一些有的没的。以上修改带来的一个附加好处是在局域网内访问服务时，通过在 <code>hosts</code> 文件中添加域名映射，可以用更加容易记忆的域名代替 <code>IP + port</code> 的形式去访问。</p>
-<span id="more"></span>
+<p>这个时候我的想法是，既然成功创建了新的日志文件，肯定是 <code>Nginx</code> 接收到了 <code>USR1</code> 信号。怎么会出现“<code>crontab</code> 触发时发送信号有问题，手动发送却没问题”的情况呢？难道是两者触发的执行方式有所不同？还是说宿主机创建的文件会有问题？注意到新的日志文件所属的用户和组和原日志文件所属的用户和组不同，我开始怀疑创建文件的过程有问题。在反复测试尝试重现问题后，我把关注点放到了 <code>create</code> 配置上。其实在最开始，我就关注了它，我想既然在默认的配置文件中已经设置而且我也不修改，那么就不在 <code>/etc/logrotate.d/nginx</code> 添加了。我甚至花了很多时间浏览文档，确认它在缺省后面的权限属性时会使用原日志文件的权限属性。当时我还专门记录了一个疑问，“文档说在运行 <code>postrotate</code> 脚本前创建新文件，可是在测试验证时，新文件是 <code>Nginx</code> 接收 <code>USR1</code> 信号后重新打开文件时创建的，在脚本执行报错或者脚本中并不发送信号时，不会产生新文件”。现在想来，都是坑，坑里注定要灌满眼泪！</p>
+<p>在 <code>/etc/logrotate.d/nginx</code> 添加 <code>create</code> 后，成功重现问题。</p>
+<figure class="highlight console"><table><tr><td class="code"><pre><span class="line">...</span><br><span class="line">renaming /path/to/your/nginx/logs/access.log to /path/to/your/nginx/logs/access.log-20231203</span><br><span class="line">creating new /path/to/your/nginx/logs/access.log mode = 0644 uid = 101 gid = 0</span><br><span class="line">error: error setting owner of /path/to/your/nginx/logs/access.log to uid 101 and gid 0: Operation not permitted</span><br><span class="line">switching euid to 0 and egid to 0</span><br></pre></td></tr></table></figure>
 
+<p>可见 <code>logrotate -f /etc/logrotate.d/nginx</code>，并没有使用到默认配置 <code>/etc/logrotate.conf</code>，而 <code>crontab</code> 触发 <code>logrotate</code> 时使用到了。修改为 <code>create 0644 moralok moralok</code>，成功解决问题。可以确认 <code>create</code> 在缺省权限属性的时候，如果日志文件因为挂载到容器中而被修改了所属用户，<code>logrotate</code> 按照原文件的权限属性创建新文件时会报错，从而导致脚本不能正常执行，<code>Nginx</code> 不会收到信号，<code>error.log</code> 也不会继续滚动。按此原因推理，在配置文件中，加入 <code>nocreate</code> 也可以解决问题，并且更加符合官方文档建议的流程。</p>
 <blockquote>
-<p><code>Cloudflare Tunnel</code> 相较于 <code>Zerotier</code> 和 <code>OpenVPN</code>，尽管它们三者都能避免直接开放家庭网络，但前者可以让用户直接使用域名访问到局域网中的服务，便于分享。但它的速度和延迟并不理想，还有人反馈存在网络不稳定的现象，但作为个人玩具还是够用的。有朋友使用公网服务器配合打洞软件和家庭网络中的服务器组网，实现相同目标的同时效果更好。</p>
+<p>枯坐一下午，百思不得其解，想到抓狂。不得不说真的很讨厌这类问题，特定条件下奇怪的问题，食之无味，弃之还不行！如果照着网上的文章，一开始就添加配置真的不会遇到啊。可是不喜欢不明不白地修改配置来解决问题，也不喜欢一次性加很多设置却不知道各个配置的功能，特别是在我的理解里这个默认配置似乎没问题的情况下。明明想要克制住不知重点还不断深入探索细节的坏习惯，却还是被一个 <code>Bug</code> 带着花费了大量的时间和精力，解决了一个照着抄就不会遇到的问题。虽然真的有收获，真的解决了前一晚留下的疑问，可是不甘心啊，气气气！而且为什么这样会有问题，我还是不懂！</p>
 </blockquote>
-<h2 id="网络结构示意图"><a href="#网络结构示意图" class="headerlink" title="网络结构示意图"></a>网络结构示意图</h2><p>客户端发起请求，请求经 <code>Cloudflare</code> 转发到局域网中的 <code>Tunnel</code>。原先，<code>Tunnel</code> 如虚线箭头所示，直接将请求发向目标服务，如今改为发向 <code>Nginx</code>，由 <code>Nginx</code> 反向代理，发向目标服务。</p>
-<img src="/2023/12/01/Nginx-reverse-proxy-for-home-networks/Pasted%20image%2020231201202859.png" class="" title="网络结构示意图">
-
-<h2 id="配置"><a href="#配置" class="headerlink" title="配置"></a>配置</h2><h3 id="docker-compose-yml"><a href="#docker-compose-yml" class="headerlink" title="docker-compose.yml"></a>docker-compose.yml</h3><p><code>Nginx</code> 和 <code>Tunnel</code> 还有其他内部服务应处于同一个网络中。</p>
-<figure class="highlight yaml"><table><tr><td class="code"><pre><span class="line"><span class="attr">version:</span> <span class="string">&quot;1.0&quot;</span></span><br><span class="line"><span class="attr">services:</span></span><br><span class="line">  <span class="attr">nginx:</span></span><br><span class="line">    <span class="attr">image:</span> <span class="string">nginx:1.25.3</span></span><br><span class="line">    <span class="attr">container_name:</span> <span class="string">nginx</span></span><br><span class="line">    <span class="attr">ports:</span></span><br><span class="line">      <span class="bullet">-</span> <span class="number">80</span><span class="string">:80</span></span><br><span class="line">    <span class="attr">volumes:</span></span><br><span class="line">      <span class="bullet">-</span> <span class="string">$PWD/etc/nginx/conf.d:/etc/nginx/conf.d</span></span><br><span class="line">      <span class="bullet">-</span> <span class="string">$PWD/etc/nginx/nginx.conf:/etc/nginx/nginx.conf</span></span><br><span class="line">      <span class="bullet">-</span> <span class="string">$PWD/log:/var/log/nginx</span></span><br><span class="line">    <span class="attr">networks:</span></span><br><span class="line">      <span class="bullet">-</span> <span class="string">my-network</span></span><br><span class="line">    <span class="attr">restart:</span> <span class="string">unless-stopped</span></span><br><span class="line"></span><br><span class="line"><span class="attr">networks:</span></span><br><span class="line">  <span class="attr">my-network:</span></span><br><span class="line">    <span class="attr">external:</span> <span class="literal">true</span></span><br></pre></td></tr></table></figure>
-
-<h3 id="etc-nginx-nginx-conf"><a href="#etc-nginx-nginx-conf" class="headerlink" title="&#x2F;etc&#x2F;nginx&#x2F;nginx.conf"></a>&#x2F;etc&#x2F;nginx&#x2F;nginx.conf</h3><p>在最后新增了拒绝未匹配成功的域名，在 <code>Cloudflare Tunnel</code> 的使用场景中，其实用处不大，因为未经配置的域名也无法解析到 <code>Nginx</code> 服务。</p>
-<figure class="highlight plaintext"><table><tr><td class="code"><pre><span class="line">user  nginx;</span><br><span class="line">worker_processes  auto;</span><br><span class="line"></span><br><span class="line">error_log  /var/log/nginx/error.log notice;</span><br><span class="line">pid        /var/run/nginx.pid;</span><br><span class="line"></span><br><span class="line"></span><br><span class="line">events &#123;</span><br><span class="line">    worker_connections  1024;</span><br><span class="line">&#125;</span><br><span class="line"></span><br><span class="line"></span><br><span class="line">http &#123;</span><br><span class="line">    include       /etc/nginx/mime.types;</span><br><span class="line">    default_type  application/octet-stream;</span><br><span class="line"></span><br><span class="line">    log_format  main  &#x27;$remote_addr - $remote_user [$time_local] &quot;$request&quot; &#x27;</span><br><span class="line">                      &#x27;$status $body_bytes_sent &quot;$http_referer&quot; &#x27;</span><br><span class="line">                      &#x27;&quot;$http_user_agent&quot; &quot;$http_x_forwarded_for&quot;&#x27;;</span><br><span class="line"></span><br><span class="line">    access_log  /var/log/nginx/access.log  main;</span><br><span class="line"></span><br><span class="line">    sendfile        on;</span><br><span class="line">    #tcp_nopush     on;</span><br><span class="line"></span><br><span class="line">    keepalive_timeout  65;</span><br><span class="line"></span><br><span class="line">    #gzip  on;</span><br><span class="line"></span><br><span class="line">    include /etc/nginx/conf.d/*.conf;</span><br><span class="line"></span><br><span class="line">    #以上是默认的配置内容，新增拒绝未匹配成功的域名</span><br><span class="line">    server &#123;</span><br><span class="line">        listen 80 default_server;</span><br><span class="line">        server_name _;</span><br><span class="line"></span><br><span class="line">        return 404;</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
-
-<h3 id="etc-nginx-conf-d"><a href="#etc-nginx-conf-d" class="headerlink" title="&#x2F;etc&#x2F;nginx&#x2F;conf.d"></a>&#x2F;etc&#x2F;nginx&#x2F;conf.d</h3><p>本目录下，配置 server 块。</p>
-<figure class="highlight plaintext"><table><tr><td class="code"><pre><span class="line">server &#123;</span><br><span class="line">    listen       80;</span><br><span class="line">    listen  [::]:80;</span><br><span class="line">    server_name  your.domain.com;</span><br><span class="line"></span><br><span class="line">    location / &#123;</span><br><span class="line">        #转发请求</span><br><span class="line">        proxy_pass http://your-service;</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
-
-<h2 id="正向代理和反向代理"><a href="#正向代理和反向代理" class="headerlink" title="正向代理和反向代理"></a>正向代理和反向代理</h2><h3 id="代理（正向代理）"><a href="#代理（正向代理）" class="headerlink" title="代理（正向代理）"></a>代理（正向代理）</h3><p><strong>代理</strong>（Proxy）也称为网络代理，是一种特殊的网络服务，允许一个终端通过这个服务与另一个终端进行非直接的连接。一般认为代理服务有利于保障网络终端的隐私或安全，在一定程度上能够阻止网络攻击。</p>
-<img src="/2023/12/01/Nginx-reverse-proxy-for-home-networks/Pasted%20image%2020231201202645.png" class="" title="正向代理">
-
-<h4 id="功能"><a href="#功能" class="headerlink" title="功能"></a>功能</h4><ul>
-<li>提高访问速度</li>
-<li>隐藏真实IP</li>
-<li>突破网站的区域限制</li>
-<li>突破网络审查</li>
-<li>……</li>
-</ul>
-<h3 id="反向代理"><a href="#反向代理" class="headerlink" title="反向代理"></a>反向代理</h3><p>反向代理（Reverse Proxy）在电脑网络中是代理服务器的一种。服务器根据客户端的请求，从其关联的一组或多组后端服务器上获取资源，然后再将这些资源返回给客户端，客户端只会得知反向代理的 <code>IP</code> 地址，而不知道在代理服务器后面的服务器集群的存在。</p>
-<img src="/2023/12/01/Nginx-reverse-proxy-for-home-networks/Pasted%20image%2020231201202654.png" class="" title="反向代理">
+<h2 id="logrotate-备忘"><a href="#logrotate-备忘" class="headerlink" title="logrotate 备忘"></a>logrotate 备忘</h2><p><a href="https://linux.die.net/man/8/logrotate">帮助文档</a></p>
+<h3 id="命令参数"><a href="#命令参数" class="headerlink" title="命令参数"></a>命令参数</h3><figure class="highlight shell"><table><tr><td class="code"><pre><span class="line">-d, --debug : 打开调试模式，这意味着不会对日志进行任何更改，并且 logrotate 状态文件不会更新。仅打印调试消息。</span><br><span class="line">-f, --force : 告诉 logrotate 强制滚动，即使它认为这没有必要。有时，在将新条目添加到 logrotate 配置文件后，或者如果已手动删除旧日志文件，这会很有用，因为将创建新文件，并且正确地继续记录日志。</span><br><span class="line">-m, --mail &lt;command&gt; : 告诉 logrotate 在邮寄日志时使用哪个命令。此命令应接受两个参数：消息的主题，收件人。然后，该命令必须读取标准输入上的消息并将其邮寄给收件人。默认邮件命令是 /bin/mail -s。</span><br><span class="line">-s, --state &lt;statefile&gt; : 告诉 logrotate 使用备用状态文件。如果 logrotate 以不同用户身份运行不同的日志文件集，这会非常有用。默认状态文件是 /var/lib/logrotate/status。</span><br><span class="line">--usage : 打印简短的用法信息。</span><br><span class="line">--?, --help : 打印帮助信息。</span><br><span class="line">-v, --verbose : 打开详细模式，例如在滚动期间显示消息。</span><br></pre></td></tr></table></figure>
 
-<h4 id="功能-1"><a href="#功能-1" class="headerlink" title="功能"></a>功能</h4><ul>
-<li>对客户端隐藏服务器（集群）的 IP 地址</li>
-<li>安全，可作为应用层防火墙</li>
-<li><strong>负载均衡</strong></li>
-<li>缓存服务，缓存静态内容和短时间内大量访问请求的动态内容</li>
-<li>压缩内容，节省带宽</li>
-<li>……</li>
-</ul>
-<h3 id="对比"><a href="#对比" class="headerlink" title="对比"></a>对比</h3><table>
+<h3 id="常用配置文件参数"><a href="#常用配置文件参数" class="headerlink" title="常用配置文件参数"></a>常用配置文件参数</h3><table>
 <thead>
 <tr>
-<th>正向代理</th>
-<th>反向代理</th>
+<th>参数</th>
+<th>说明</th>
 </tr>
 </thead>
 <tbody><tr>
-<td>客户端的代理</td>
-<td>服务端的代理</td>
+<td>daily</td>
+<td>周期：每天</td>
 </tr>
 <tr>
-<td>客户端一般需要特别设置</td>
-<td>客户端不用做任何设置</td>
+<td>weekly</td>
+<td>周期：每周</td>
 </tr>
 <tr>
-<td>请求发向目标服务器</td>
-<td>请求发向代理</td>
+<td>monthly</td>
+<td>周期：每月</td>
 </tr>
 <tr>
-<td>服务端知道代理不知道客户端</td>
-<td>客户端知道代理不知道服务器</td>
+<td>yearly</td>
+<td>周期：每年</td>
+</tr>
+<tr>
+<td>dateext</td>
+<td>使用日期代替数字作为扩展名（YYYYMMDD），如：access.log-20231202</td>
+</tr>
+<tr>
+<td>dateformat</td>
+<td>必须配合 dateext 使用，只支持 %Y %m %d %s 这四个参数</td>
+</tr>
+<tr>
+<td>compress</td>
+<td>使用 gzip 压缩旧版本日志文件</td>
+</tr>
+<tr>
+<td>nocompress</td>
+<td>不压缩</td>
+</tr>
+<tr>
+<td>delaycompress</td>
+<td>延迟到下一次滚动周期再压缩</td>
+</tr>
+<tr>
+<td>nodelaycompress</td>
+<td>不延迟压缩，覆盖 delaycompress</td>
+</tr>
+<tr>
+<td>create mode owner group</td>
+<td>滚动后（运行 postrotate 脚本前），立即创建日志文件，指定权限属性</td>
+</tr>
+<tr>
+<td>nocreate</td>
+<td>不创建新的日志文件，覆盖 create</td>
+</tr>
+<tr>
+<td>copytruncate</td>
+<td>创建副本后就地截断原始日志文件，用于一些无法被告知关闭日志文件的程序，可能会丢失复制和截断之间的日志</td>
+</tr>
+<tr>
+<td>nocopytruncate</td>
+<td>不截断始日志文件，覆盖 copytruncate</td>
+</tr>
+<tr>
+<td>ifempty</td>
+<td>即使是空文件也滚动（默认），覆盖 notifempty</td>
+</tr>
+<tr>
+<td>missingok</td>
+<td>如果日志丢失，不报错继续滚动下一个日志</td>
+</tr>
+<tr>
+<td>notifempty</td>
+<td>如果是空文件，不滚动，覆盖 ifempty</td>
+</tr>
+<tr>
+<td>sharedscripts</td>
+<td>在所有日志都滚动后统一执行一次脚本。如果没有配置，每个日志滚动后都会执行一次脚本</td>
+</tr>
+<tr>
+<td>prerotate&#x2F;endscript</td>
+<td>存放在滚动以前需要执行的脚本，两者必须单独成行</td>
+</tr>
+<tr>
+<td>postrotate&#x2F;endscript</td>
+<td>存放在滚动以后需要执行的脚本，两者必须单独成行</td>
+</tr>
+<tr>
+<td>rotate count</td>
+<td>日志文件在删除或邮寄前滚动的次数，0 指没有备份</td>
+</tr>
+<tr>
+<td>size log-size</td>
+<td>当日志文件到达指定的大小时才滚动，默认单位 byte，可以使用 k、M、G</td>
 </tr>
 </tbody></table>
 <h2 id="参考文章"><a href="#参考文章" class="headerlink" title="参考文章"></a>参考文章</h2><ul>
-<li><a href="https://zh.wikipedia.org/wiki/%E4%BB%A3%E7%90%86%E6%9C%8D%E5%8A%A1%E5%99%A8">代理服务器</a></li>
-<li><a href="https://zh.wikipedia.org/wiki/%E5%8F%8D%E5%90%91%E4%BB%A3%E7%90%86">反向代理</a></li>
+<li><a href="https://nginx.org/en/docs/control.html#logs">Rotating Log-files</a></li>
+<li><a href="https://www.nginx.com/resources/wiki/start/topics/examples/logrotation/">Log Rotation</a></li>
+<li><a href="https://linux.die.net/man/8/logrotate">logrotate(8) - Linux man page</a></li>
+<li><a href="https://serverfault.com/questions/1023555/error-error-creating-output-file-var-lib-logrotate-status-tmp-permission-deni">error: error creating output file &#x2F;var&#x2F;lib&#x2F;logrotate.status.tmp: Permission denied</a></li>
+<li><a href="https://stackoverflow.com/questions/26482773/apache-and-logrotate-configuration">apache-and-logrotate-configuration</a></li>
+<li><a href="https://blog.slogra.com/post-792.html">docker nginx&#x2F;openresty容器使用logrotate日志切割</a></li>
 </ul>
 ]]></content>
       <tags>
+        <tag>docker</tag>
         <tag>nginx</tag>
-        <tag>reverse proxy</tag>
+        <tag>logrotate</tag>
       </tags>
   </entry>
   <entry>
@@ -4003,226 +3835,35 @@
       </tags>
   </entry>
   <entry>
-    <title>使用 logrotate 滚动 Docker 容器内的 Nginx 的日志</title>
-    <url>/2023/12/02/rotating-nginx-logs-in-docker-container-with-logrotate/</url>
-    <content><![CDATA[<p><code>Nginx</code> 没有提供开箱即用的日志滚动功能，而是将其交给使用者自己实现。你既可以按照官方文档的建议通过编写脚本实现，也可以使用 <code>logrotate</code> 管理日志。但是和在普通场景下不同，在使用 <code>Docker</code> 运行 <code>Nginx</code> 时，你可能需要额外考虑一点细节。本文记录了在为 <code>Docker</code> 中的 <code>Nginx</code> 的日志文件配置滚动功能过程中遇到的一些问题和思考。</p>
+    <title>Spring 中 @Import 注解的使用和源码分析</title>
+    <url>/2023/12/04/use-and-analysis-of-Import-annotation-in-Spring/</url>
+    <content><![CDATA[<p><code>Import</code> 注解是 <code>Spring</code> 基于 <code>Java</code> 注解配置的重要组成部分，处理 <code>Import</code> 注解是处理 <code>Configuration</code> 注解的子过程之一，本文将介绍 <code>Import</code> 注解的 <code>3</code> 种使用方式，然后通过分析源码和处理过程示意图解释它是如何导入（注册） <code>BeanDefinition</code> 的。</p>
 <span id="more"></span>
 
-<h2 id="Nginx-滚动日志"><a href="#Nginx-滚动日志" class="headerlink" title="Nginx 滚动日志"></a>Nginx 滚动日志</h2><h3 id="官方文档"><a href="#官方文档" class="headerlink" title="官方文档"></a>官方文档</h3><blockquote>
-<p>In order to rotate log files, they need to be renamed first. After that USR1 signal should be sent to the master process. The master process will then re-open all currently open log files and assign them an unprivileged user under which the worker processes are running, as an owner. After successful re-opening, the master process closes all open files and sends the message to worker process to ask them to re-open files. Worker processes also open new files and close old files right away. As a result, old files are almost immediately available for post processing, such as compression.</p>
-</blockquote>
-<p>根据官方文档的解释，滚动日志文件的流程应如下，你可以自己编写 <code>Shell</code> 脚本配合 <code>crontab</code> 实现定时滚动功能。</p>
+<ul>
+<li>本文的写作动机继承自<a href="/2023/11/23/source-code-analysis-of-Spring-Configuration-annotation/" title="Spring @Configuration 注解的源码分析">Spring @Configuration 注解的源码分析</a>，处理 <code>@Import</code> 是处理 <code>@Configuration</code> 过程的一部分。</li>
+</ul>
+<h2 id="使用方式"><a href="#使用方式" class="headerlink" title="使用方式"></a>使用方式</h2><p><code>Import</code> 注解有 <code>3</code> 种导入（注册） <code>BeanDefinition</code> 的方式：</p>
 <ol>
-<li>首先重命名日志文件</li>
-<li>之后发送 <code>USR1</code> 信号给 <code>Nginx</code> 主进程，<code>Nginx</code> 将重新打开日志文件</li>
-<li>对日志文件进行后处理，比如压缩（可选）</li>
+<li>使用 <code>Import</code> 将目标类的 <code>Class</code> 对象，解析为 <code>BeanDefinition</code> 并注册。</li>
+<li>使用 <code>Import</code> 配合 <code>ImportSelector</code> 的实现类，将 <code>selectImports</code> 方法返回的所有全限定类名字符串，解析为 <code>BeanDefinition</code> 并注册。</li>
+<li>使用 <code>Import</code> 配合 <code>ImportBeanDefinitionRegistra</code>r 的实现类，在 <code>registerBeanDefinitions</code> 方法中，直接向 <code>BeanDefinitionRegistry</code> 中注册 <code>BeanDefinition</code>。</li>
 </ol>
-<figure class="highlight shell"><table><tr><td class="code"><pre><span class="line"><span class="meta prompt_">$ </span><span class="language-bash"><span class="built_in">mv</span> access.log access.log.0</span></span><br><span class="line"><span class="meta prompt_">$ </span><span class="language-bash"><span class="built_in">kill</span> -USR1 `<span class="built_in">cat</span> master.nginx.pid`</span></span><br><span class="line"><span class="meta prompt_">$ </span><span class="language-bash"><span class="built_in">sleep</span> 1</span></span><br><span class="line"><span class="meta prompt_">$ </span><span class="language-bash">gzip access.log.0    <span class="comment"># do something with access.log.0</span></span></span><br></pre></td></tr></table></figure>
-
-<h4 id="说明"><a href="#说明" class="headerlink" title="说明"></a>说明</h4><ol>
-<li>在没有执行 <code>kill</code> 命令前，即便已经重命名了日志文件，<code>Nginx</code> 还是会向重命名后的文件写入日志。因为在 <code>Linux</code> 系统中，系统内核是根据文件描述符定位文件的。</li>
-<li><code>USR1</code> 是自定义信号，软件的作者自己确定收到该信号后做什么。在 <code>Nginx</code> 中，主进程收到信号后，会重新打开所有当前打开的日志文件并将它们分配给一个非特权用户作为所有者，工作进程就是在该所有者下运行的。成功重新打开后，主进程关闭所有打开的文件并向工作进程发送消息，要求它们重新打开文件。工作进程也打开新文件并立即关闭旧文件。</li>
+<h2 id="测试用例"><a href="#测试用例" class="headerlink" title="测试用例"></a>测试用例</h2><p>测试了使用 <code>Import</code> 注解的 <code>3</code> 种方式：</p>
+<ol>
+<li>使用 <code>Import</code> 直接导入（注册） <code>Red</code>。</li>
+<li>配合 <code>ImportBeanDefinitionRegistrar</code> 间接注册 <code>Color</code>。</li>
+<li>配合 <code>ImportSelector</code> 间接导入（注册） <code>Blue</code>。</li>
 </ol>
-<h3 id="使用-logrotate"><a href="#使用-logrotate" class="headerlink" title="使用 logrotate"></a>使用 logrotate</h3><blockquote>
-<p>logrotate is designed to ease administration of systems that generate large numbers of log files. It allows automatic rotation, compression, removal, and mailing of log files. Each log file may be handled daily, weekly, monthly, or when it grows too large.</p>
-</blockquote>
-<p><code>logrotate</code> 旨在简化生成大量日志文件的系统的管理。它允许自动滚动、压缩、删除和邮寄日志文件。每个日志文件可以在每天、每周、每月或当它变得太大时处理。<code>Linux</code> 一般默认安装了 <code>logrotate</code>。</p>
-<h4 id="默认配置文件"><a href="#默认配置文件" class="headerlink" title="默认配置文件"></a>默认配置文件</h4><p>查看默认配置文件：<code>cat /etc/logrotate.conf</code>。</p>
-<figure class="highlight plaintext"><table><tr><td class="code"><pre><span class="line"># see &quot;man logrotate&quot; for details</span><br><span class="line"># 每周滚动日志文件</span><br><span class="line">weekly</span><br><span class="line"></span><br><span class="line"># 默认使用 adm group，因为这是 /var/log/syslog 的所属组</span><br><span class="line">su root adm</span><br><span class="line"></span><br><span class="line"># 保留 4 周的备份（其实是保留 4 个备份，对应 weekly 的设置，就是保留 4 周）</span><br><span class="line">rotate 4</span><br><span class="line"></span><br><span class="line"># 在滚动旧日志文件后，创建新的空日志文件</span><br><span class="line">create</span><br><span class="line"></span><br><span class="line"># 使用日期作为滚动日志文件的后缀</span><br><span class="line">#dateext</span><br><span class="line"></span><br><span class="line"># 如果你希望压缩日志文件，请取消注释</span><br><span class="line">#compress</span><br><span class="line"></span><br><span class="line"># 软件包将日志滚动的配置信息放入此目录中</span><br><span class="line">include /etc/logrotate.d</span><br><span class="line"></span><br><span class="line"># system-specific logs may be also be configured here.</span><br></pre></td></tr></table></figure>
-
-<h4 id="配置信息所在目录"><a href="#配置信息所在目录" class="headerlink" title="配置信息所在目录"></a>配置信息所在目录</h4><p>查看日志滚动的配置信息所在的目录：<code>ls /etc/logrotate.d/</code>。</p>
-<figure class="highlight console"><table><tr><td class="code"><pre><span class="line">alternatives  apport  apt  bootlog  btmp  dpkg  rsyslog  ubuntu-advantage-tools  ufw  unattended-upgrades  wtmp</span><br></pre></td></tr></table></figure>
+<p>用例中的特别地测试了以下两种情况：</p>
+<ol>
+<li>使用 <code>Import</code> 直接导入和配合 <code>ImportSelector</code> 间接导入相同的类 <code>Red</code> 只会注册一个 <code>BeanDefinition</code>。</li>
+<li>尽管 <code>MyImportSelector</code> 书面顺序在 <code>MyImportBeanDefinitionRegistrar</code> 之后，但是 <code>MyImportBeanDefinitionRegistrar</code> 判断 <code>registry</code> 是否包含在 <code>MyImportSelector</code> 导入的类 <code>Blue</code> 时，不受顺序影响。</li>
+</ol>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="meta">@Configuration</span></span><br><span class="line"><span class="meta">@Import(&#123;Red.class, MyImportBeanDefinitionRegistrar.class, MyImportSelector.class,&#125;)</span></span><br><span class="line"><span class="keyword">public</span> <span class="keyword">class</span> <span class="title class_">ImportConfig</span> &#123;</span><br><span class="line">&#125;</span><br><span class="line"></span><br><span class="line"><span class="keyword">public</span> <span class="keyword">class</span> <span class="title class_">MyImportBeanDefinitionRegistrar</span> <span class="keyword">implements</span> <span class="title class_">ImportBeanDefinitionRegistrar</span> &#123;</span><br><span class="line"></span><br><span class="line">    <span class="meta">@Override</span></span><br><span class="line">    <span class="keyword">public</span> <span class="keyword">void</span> <span class="title function_">registerBeanDefinitions</span><span class="params">(AnnotationMetadata importingClassMetadata, BeanDefinitionRegistry registry)</span> &#123;</span><br><span class="line">        <span class="type">boolean</span> <span class="variable">hasRed</span> <span class="operator">=</span> registry.containsBeanDefinition(<span class="string">&quot;com.moralok.bean.Red&quot;</span>);</span><br><span class="line">        <span class="type">boolean</span> <span class="variable">hasBlue</span> <span class="operator">=</span> registry.containsBeanDefinition(<span class="string">&quot;com.moralok.bean.Blue&quot;</span>);</span><br><span class="line">        <span class="keyword">if</span> (hasRed &amp;&amp; hasBlue) &#123;</span><br><span class="line">            <span class="type">BeanDefinition</span> <span class="variable">beanDefinition</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">RootBeanDefinition</span>(Color.class);</span><br><span class="line">            registry.registerBeanDefinition(<span class="string">&quot;color&quot;</span>, beanDefinition);</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br><span class="line"></span><br><span class="line"><span class="keyword">public</span> <span class="keyword">class</span> <span class="title class_">MyImportSelector</span> <span class="keyword">implements</span> <span class="title class_">ImportSelector</span> &#123;</span><br><span class="line"></span><br><span class="line">    <span class="meta">@Override</span></span><br><span class="line">    <span class="keyword">public</span> String[] selectImports(AnnotationMetadata annotationMetadata) &#123;</span><br><span class="line">        <span class="keyword">return</span> <span class="keyword">new</span> <span class="title class_">String</span>[] &#123;<span class="string">&quot;com.moralok.bean.Blue&quot;</span>, <span class="string">&quot;com.moralok.bean.Red&quot;</span>&#125;;</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br><span class="line"></span><br><span class="line"><span class="keyword">public</span> <span class="keyword">class</span> <span class="title class_">Color</span> &#123;</span><br><span class="line">&#125;</span><br><span class="line"></span><br><span class="line"><span class="keyword">public</span> <span class="keyword">class</span> <span class="title class_">Red</span> &#123;</span><br><span class="line">&#125;</span><br><span class="line"></span><br><span class="line"><span class="keyword">public</span> <span class="keyword">class</span> <span class="title class_">Blue</span> &#123;</span><br><span class="line">&#125;</span><br><span class="line"></span><br><span class="line"><span class="keyword">public</span> <span class="keyword">class</span> <span class="title class_">IocTest</span> &#123;</span><br><span class="line">    <span class="meta">@Test</span></span><br><span class="line">    <span class="keyword">public</span> <span class="keyword">void</span> <span class="title function_">importTest</span><span class="params">()</span> &#123;</span><br><span class="line">        <span class="type">ApplicationContext</span> <span class="variable">ac</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">AnnotationConfigApplicationContext</span>(ImportConfig.class);</span><br><span class="line">        String[] beanDefinitionNames = ac.getBeanDefinitionNames();</span><br><span class="line">        <span class="keyword">for</span> (String name : beanDefinitionNames) &#123;</span><br><span class="line">            System.out.println(<span class="string">&quot;beanDefinitionName..........&quot;</span> + name);</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
 
-<h4 id="为-Nginx-新增配置"><a href="#为-Nginx-新增配置" class="headerlink" title="为 Nginx 新增配置"></a>为 Nginx 新增配置</h4><p>为 <code>Nginx</code> 新增日志滚动配置，<code>vim /etc/logrotate.d/nginx</code>。</p>
-<figure class="highlight plaintext"><table><tr><td class="code"><pre><span class="line">/path/to/your/nginx/logs/*.log &#123;</span><br><span class="line">    # 切换用户</span><br><span class="line">    su moralok moralok</span><br><span class="line">    # 每天滚动日志文件</span><br><span class="line">    daily</span><br><span class="line">    # 使用日期作为滚动日志文件的后缀</span><br><span class="line">    dateext</span><br><span class="line">    # 如果日志丢失，不报错继续滚动下一个日志</span><br><span class="line">    missingok</span><br><span class="line">    # 保留 31 个备份</span><br><span class="line">    rotate 31</span><br><span class="line">    # 不压缩</span><br><span class="line">    nocompress</span><br><span class="line">    # 整个日志组运行一次的脚本</span><br><span class="line">    sharedscripts</span><br><span class="line">    # 滚动后的处理</span><br><span class="line">    postrotate</span><br><span class="line">        # 重新打开日志文件        </span><br><span class="line">        docker exec nginx sh -c &quot;[ ! -f /var/run/nginx.pid ] || (kill -USR1 `docker exec nginx cat /var/run/nginx.pid`; echo &#x27;Successfully rotating nginx logs.&#x27;)&quot;</span><br><span class="line">    endscript</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
-
-<h4 id="验证配置和测试"><a href="#验证配置和测试" class="headerlink" title="验证配置和测试"></a>验证配置和测试</h4><p>测试配置文件是否有错误，<code>logrotate -d /etc/logrotate.d/nginx</code>。</p>
-<p>强制滚动：<code>logrotate -f /etc/logrotate.d/nginx</code></p>
-<h2 id="一些坑"><a href="#一些坑" class="headerlink" title="一些坑"></a>一些坑</h2><h3 id="var-lib-logrotate-权限问题"><a href="#var-lib-logrotate-权限问题" class="headerlink" title="&#x2F;var&#x2F;lib&#x2F;logrotate&#x2F; 权限问题"></a>&#x2F;var&#x2F;lib&#x2F;logrotate&#x2F; 权限问题</h3><p>当你使用校验过配置文件的正确性后，尝试强制滚动时，可能会遇到报错。</p>
-<figure class="highlight console"><table><tr><td class="code"><pre><span class="line"><span class="meta prompt_">$ </span><span class="language-bash">logrotate -f /etc/logrotate.d/nginx</span> </span><br><span class="line">error: error creating output file /var/lib/logrotate/status.tmp: Permission denied</span><br></pre></td></tr></table></figure>
-
-<p>这是因为 logrotate 会在 <code>/var/lib/logrotate/</code> 目录下创建 <code>status</code> 文件。查看目录权限可知，需要以 <code>root</code> 身份运行 <code>logrotate</code>。</p>
-<figure class="highlight console"><table><tr><td class="code"><pre><span class="line"><span class="meta prompt_">$ </span><span class="language-bash">ll /var/lib/logrotate</span></span><br><span class="line">total 12</span><br><span class="line">drwxr-xr-x  2 root root 4096 Dec  2 08:35 ./</span><br><span class="line">drwxr-xr-x 44 root root 4096 Jun 26 09:02 ../</span><br><span class="line">-rw-r--r--  1 root root 1395 Dec  2 08:35 status</span><br></pre></td></tr></table></figure>
-
-<p>事实上，<code>logrotate -d /etc/logrotate.d/nginx</code> 命令也会读取 <code>/var/lib/logrotate/status</code>，但是 <code>other</code> 对该目录也有 <code>r</code> 读取权限，所以没有报错。</p>
-<figure class="highlight console"><table><tr><td class="code"><pre><span class="line"><span class="meta prompt_">$ </span><span class="language-bash">logrotate -d /etc/logrotate.d/nginx</span> </span><br><span class="line">WARNING: logrotate in debug mode does nothing except printing debug messages!  Consider using verbose mode (-v) instead if this is not what you want.</span><br><span class="line"></span><br><span class="line">reading config file /etc/logrotate.d/nginx</span><br><span class="line">Reading state from file: /var/lib/logrotate/status</span><br><span class="line">...</span><br></pre></td></tr></table></figure>
-
-<h3 id="日志文件夹的权限"><a href="#日志文件夹的权限" class="headerlink" title="日志文件夹的权限"></a>日志文件夹的权限</h3><p>即使你使用 <code>root</code> 身份运行 <code>logrotate</code>，你可能还会遇到以下报错</p>
-<figure class="highlight console"><table><tr><td class="code"><pre><span class="line"><span class="meta prompt_">$ </span><span class="language-bash">logrotate -f /etc/logrotate.d/nginx</span> </span><br><span class="line">error: skipping &quot;/path/to/your/nginx/logs/*.log&quot; because parent directory has insecure permissions (It&#x27;s world writable or writable by group which is not &quot;root&quot;) Set &quot;su&quot; directive in config file to tell logrotate which user/group should be used for rotation.</span><br></pre></td></tr></table></figure>
-
-<p>你需要在配置文件中，使用 <code>su &lt;user&gt; &lt;group&gt;</code> 指定日志所在文件夹所属的用户和组，<code>logrotate</code> 才能正确读写。</p>
-<h3 id="由宿主机还是容器主导"><a href="#由宿主机还是容器主导" class="headerlink" title="由宿主机还是容器主导"></a>由宿主机还是容器主导</h3><p>首先 <code>Nginx</code> 的日志文件夹通过挂载映射到宿主机，日志滚动既可以由宿主机主导，也可以由容器主导，不过不论如何我们都需要向 <code>Docker</code> 容器内的 <code>Nginx</code> 发送 <code>USR1</code> 信号。有人倾向于在容器内完成所有工作，和宿主机几乎完全隔离；我个人更青睐于由宿主机主导，因为容器内的环境并不总是拥有你想要使用的软件（除非你总是定制自己使用的镜像），甚至标准镜像往往非常精简。</p>
-<p>在 <code>logrotate</code> 配置中的 <code>postrotate</code> 部分添加脚本，使用 <code>docker exec</code> 在容器内执行命令，完成向 <code>Nginx</code> 发送信号的工作。脚本的处理逻辑大概是“如果存在 <code>/var/run/nginx.pid</code>，就执行 <code>kill -USR1 \`cat /var/run/nginx.pid\`</code> 命令，并打印成功的消息”。但是我看到很多文章中分享的配置类似下面这样：</p>
-<figure class="highlight shell"><table><tr><td class="code"><pre><span class="line">docker exec nginx sh -c &quot;if [ -f /var/run/nginx.pid ]; then kill -USR1 $(docker exec nginx cat /var/run/nginx.pid); fi&quot;</span><br><span class="line"></span><br><span class="line">docker exec nginx sh -c &quot;[ ! -f /var/run/nginx.pid ] || kill -USR1 `cat /var/run/nginx.pid`;&quot;</span><br></pre></td></tr></table></figure>
-
-<p>经过测试都会有以下报错，我不清楚是否大多是抓取发布的文章，也不清楚他们是否测试过，对于 <code>Shell</code> 脚本写得不多的我来说，半夜测试反复排查错误真是头昏脑胀。在我原先的理解里，<code>-c</code> 后面的脚本是整体发到容器内部执行的，后来我才意识到，我对脚本内部的命令在宿主机还是容器里执行的理解是错误的。</p>
-<figure class="highlight console"><table><tr><td class="code"><pre><span class="line">cat: /var/run/nginx.pid: No such file or directory</span><br></pre></td></tr></table></figure>
-
-<h3 id="继续写入旧日志文件"><a href="#继续写入旧日志文件" class="headerlink" title="继续写入旧日志文件"></a>继续写入旧日志文件</h3><p>在使用 <code>logrotate -f /etc/logrotate.d/nginx</code> 测试通过后的第二天，发现虽然创建了新的日志文件，但是 <code>Nginx</code> 继续写入到旧的日志文件。这不同于网上很多文章提到的“没有发送 <code>USR1</code> 信号给 <code>Nginx</code> ”的情况。</p>
-<p>尝试手动发送信号，观察效果。</p>
-<figure class="highlight shell"><table><tr><td class="code"><pre><span class="line">docker exec nginx sh -c &quot;kill -USR1 `docker exec nginx cat /var/run/nginx.pid`&quot;</span><br></pre></td></tr></table></figure>
-
-<p>发现虽然终止了继续写入到旧的文件，但是在宿主机读取日志时，提示没有权限。</p>
-<figure class="highlight console"><table><tr><td class="code"><pre><span class="line"><span class="meta prompt_">$ </span><span class="language-bash"><span class="built_in">cat</span> access.log</span></span><br><span class="line">cat: access.log: Permission denied</span><br></pre></td></tr></table></figure>
-
-<p>查看日志文件权限，发现不对劲。新建的 <code>access.log</code> 的权限为 <code>600</code>，所属用户从 <code>moralok</code> 变为 <code>systemd-resolve</code>，失去了只有所属用户才拥有的 <code>rw</code> 权限。</p>
-<blockquote>
-<p>此时虽然注意到没有成功创建新的 <code>error.log</code>，但是只是以为对于空的日志文件不滚动。并且在后续重现问题时发现此时其实可以在容器里看到日志开始写入新的日志文件。</p>
-</blockquote>
-<figure class="highlight console"><table><tr><td class="code"><pre><span class="line"><span class="meta prompt_">$ </span><span class="language-bash">ll</span></span><br><span class="line">total 136</span><br><span class="line">drwxrwxr-x 2 moralok         moralok 4096 Dec  3 00:00 ./</span><br><span class="line">drwxrwxr-x 4 moralok         moralok 4096 Nov 30 17:25 ../</span><br><span class="line">-rw------- 1 moralok         moralok    0 Dec  3 00:00 access.log</span><br><span class="line">-rw-r--r-- 1 systemd-resolve root  109200 Dec  3 07:01 access.log-20231203</span><br><span class="line">-rw-r--r-- 1 systemd-resolve root       0 Dec  2 19:07 error.log</span><br></pre></td></tr></table></figure>
-
-<p>这个时候我的想法是，既然成功创建了新的日志文件，肯定是 <code>Nginx</code> 接收到了 <code>USR1</code> 信号。怎么会出现“<code>crontab</code> 触发时发送信号有问题，手动发送却没问题”的情况呢？难道是两者触发的执行方式有所不同？还是说宿主机创建的文件会有问题？注意到新的日志文件所属的用户和组和原日志文件所属的用户和组不同，我开始怀疑创建文件的过程有问题。在反复测试尝试重现问题后，我把关注点放到了 <code>create</code> 配置上。其实在最开始，我就关注了它，我想既然在默认的配置文件中已经设置而且我也不修改，那么就不在 <code>/etc/logrotate.d/nginx</code> 添加了。我甚至花了很多时间浏览文档，确认它在缺省后面的权限属性时会使用原日志文件的权限属性。当时我还专门记录了一个疑问，“文档说在运行 <code>postrotate</code> 脚本前创建新文件，可是在测试验证时，新文件是 <code>Nginx</code> 接收 <code>USR1</code> 信号后重新打开文件时创建的，在脚本执行报错或者脚本中并不发送信号时，不会产生新文件”。现在想来，都是坑，坑里注定要灌满眼泪！</p>
-<p>在 <code>/etc/logrotate.d/nginx</code> 添加 <code>create</code> 后，成功重现问题。</p>
-<figure class="highlight console"><table><tr><td class="code"><pre><span class="line">...</span><br><span class="line">renaming /path/to/your/nginx/logs/access.log to /path/to/your/nginx/logs/access.log-20231203</span><br><span class="line">creating new /path/to/your/nginx/logs/access.log mode = 0644 uid = 101 gid = 0</span><br><span class="line">error: error setting owner of /path/to/your/nginx/logs/access.log to uid 101 and gid 0: Operation not permitted</span><br><span class="line">switching euid to 0 and egid to 0</span><br></pre></td></tr></table></figure>
-
-<p>可见 <code>logrotate -f /etc/logrotate.d/nginx</code>，并没有使用到默认配置 <code>/etc/logrotate.conf</code>，而 <code>crontab</code> 触发 <code>logrotate</code> 时使用到了。修改为 <code>create 0644 moralok moralok</code>，成功解决问题。可以确认 <code>create</code> 在缺省权限属性的时候，如果日志文件因为挂载到容器中而被修改了所属用户，<code>logrotate</code> 按照原文件的权限属性创建新文件时会报错，从而导致脚本不能正常执行，<code>Nginx</code> 不会收到信号，<code>error.log</code> 也不会继续滚动。按此原因推理，在配置文件中，加入 <code>nocreate</code> 也可以解决问题，并且更加符合官方文档建议的流程。</p>
-<blockquote>
-<p>枯坐一下午，百思不得其解，想到抓狂。不得不说真的很讨厌这类问题，特定条件下奇怪的问题，食之无味，弃之还不行！如果照着网上的文章，一开始就添加配置真的不会遇到啊。可是不喜欢不明不白地修改配置来解决问题，也不喜欢一次性加很多设置却不知道各个配置的功能，特别是在我的理解里这个默认配置似乎没问题的情况下。明明想要克制住不知重点还不断深入探索细节的坏习惯，却还是被一个 <code>Bug</code> 带着花费了大量的时间和精力，解决了一个照着抄就不会遇到的问题。虽然真的有收获，真的解决了前一晚留下的疑问，可是不甘心啊，气气气！而且为什么这样会有问题，我还是不懂！</p>
-</blockquote>
-<h2 id="logrotate-备忘"><a href="#logrotate-备忘" class="headerlink" title="logrotate 备忘"></a>logrotate 备忘</h2><p><a href="https://linux.die.net/man/8/logrotate">帮助文档</a></p>
-<h3 id="命令参数"><a href="#命令参数" class="headerlink" title="命令参数"></a>命令参数</h3><figure class="highlight shell"><table><tr><td class="code"><pre><span class="line">-d, --debug : 打开调试模式，这意味着不会对日志进行任何更改，并且 logrotate 状态文件不会更新。仅打印调试消息。</span><br><span class="line">-f, --force : 告诉 logrotate 强制滚动，即使它认为这没有必要。有时，在将新条目添加到 logrotate 配置文件后，或者如果已手动删除旧日志文件，这会很有用，因为将创建新文件，并且正确地继续记录日志。</span><br><span class="line">-m, --mail &lt;command&gt; : 告诉 logrotate 在邮寄日志时使用哪个命令。此命令应接受两个参数：消息的主题，收件人。然后，该命令必须读取标准输入上的消息并将其邮寄给收件人。默认邮件命令是 /bin/mail -s。</span><br><span class="line">-s, --state &lt;statefile&gt; : 告诉 logrotate 使用备用状态文件。如果 logrotate 以不同用户身份运行不同的日志文件集，这会非常有用。默认状态文件是 /var/lib/logrotate/status。</span><br><span class="line">--usage : 打印简短的用法信息。</span><br><span class="line">--?, --help : 打印帮助信息。</span><br><span class="line">-v, --verbose : 打开详细模式，例如在滚动期间显示消息。</span><br></pre></td></tr></table></figure>
-
-<h3 id="常用配置文件参数"><a href="#常用配置文件参数" class="headerlink" title="常用配置文件参数"></a>常用配置文件参数</h3><table>
-<thead>
-<tr>
-<th>参数</th>
-<th>说明</th>
-</tr>
-</thead>
-<tbody><tr>
-<td>daily</td>
-<td>周期：每天</td>
-</tr>
-<tr>
-<td>weekly</td>
-<td>周期：每周</td>
-</tr>
-<tr>
-<td>monthly</td>
-<td>周期：每月</td>
-</tr>
-<tr>
-<td>yearly</td>
-<td>周期：每年</td>
-</tr>
-<tr>
-<td>dateext</td>
-<td>使用日期代替数字作为扩展名（YYYYMMDD），如：access.log-20231202</td>
-</tr>
-<tr>
-<td>dateformat</td>
-<td>必须配合 dateext 使用，只支持 %Y %m %d %s 这四个参数</td>
-</tr>
-<tr>
-<td>compress</td>
-<td>使用 gzip 压缩旧版本日志文件</td>
-</tr>
-<tr>
-<td>nocompress</td>
-<td>不压缩</td>
-</tr>
-<tr>
-<td>delaycompress</td>
-<td>延迟到下一次滚动周期再压缩</td>
-</tr>
-<tr>
-<td>nodelaycompress</td>
-<td>不延迟压缩，覆盖 delaycompress</td>
-</tr>
-<tr>
-<td>create mode owner group</td>
-<td>滚动后（运行 postrotate 脚本前），立即创建日志文件，指定权限属性</td>
-</tr>
-<tr>
-<td>nocreate</td>
-<td>不创建新的日志文件，覆盖 create</td>
-</tr>
-<tr>
-<td>copytruncate</td>
-<td>创建副本后就地截断原始日志文件，用于一些无法被告知关闭日志文件的程序，可能会丢失复制和截断之间的日志</td>
-</tr>
-<tr>
-<td>nocopytruncate</td>
-<td>不截断始日志文件，覆盖 copytruncate</td>
-</tr>
-<tr>
-<td>ifempty</td>
-<td>即使是空文件也滚动（默认），覆盖 notifempty</td>
-</tr>
-<tr>
-<td>missingok</td>
-<td>如果日志丢失，不报错继续滚动下一个日志</td>
-</tr>
-<tr>
-<td>notifempty</td>
-<td>如果是空文件，不滚动，覆盖 ifempty</td>
-</tr>
-<tr>
-<td>sharedscripts</td>
-<td>在所有日志都滚动后统一执行一次脚本。如果没有配置，每个日志滚动后都会执行一次脚本</td>
-</tr>
-<tr>
-<td>prerotate&#x2F;endscript</td>
-<td>存放在滚动以前需要执行的脚本，两者必须单独成行</td>
-</tr>
-<tr>
-<td>postrotate&#x2F;endscript</td>
-<td>存放在滚动以后需要执行的脚本，两者必须单独成行</td>
-</tr>
-<tr>
-<td>rotate count</td>
-<td>日志文件在删除或邮寄前滚动的次数，0 指没有备份</td>
-</tr>
-<tr>
-<td>size log-size</td>
-<td>当日志文件到达指定的大小时才滚动，默认单位 byte，可以使用 k、M、G</td>
-</tr>
-</tbody></table>
-<h2 id="参考文章"><a href="#参考文章" class="headerlink" title="参考文章"></a>参考文章</h2><ul>
-<li><a href="https://nginx.org/en/docs/control.html#logs">Rotating Log-files</a></li>
-<li><a href="https://www.nginx.com/resources/wiki/start/topics/examples/logrotation/">Log Rotation</a></li>
-<li><a href="https://linux.die.net/man/8/logrotate">logrotate(8) - Linux man page</a></li>
-<li><a href="https://serverfault.com/questions/1023555/error-error-creating-output-file-var-lib-logrotate-status-tmp-permission-deni">error: error creating output file &#x2F;var&#x2F;lib&#x2F;logrotate.status.tmp: Permission denied</a></li>
-<li><a href="https://stackoverflow.com/questions/26482773/apache-and-logrotate-configuration">apache-and-logrotate-configuration</a></li>
-<li><a href="https://blog.slogra.com/post-792.html">docker nginx&#x2F;openresty容器使用logrotate日志切割</a></li>
-</ul>
-]]></content>
-      <tags>
-        <tag>docker</tag>
-        <tag>nginx</tag>
-        <tag>logrotate</tag>
-      </tags>
-  </entry>
-  <entry>
-    <title>Spring 中 @Import 注解的使用和源码分析</title>
-    <url>/2023/12/04/use-and-analysis-of-Import-annotation-in-Spring/</url>
-    <content><![CDATA[<p><code>Import</code> 注解是 <code>Spring</code> 基于 <code>Java</code> 注解配置的重要组成部分，处理 <code>Import</code> 注解是处理 <code>Configuration</code> 注解的子过程之一，本文将介绍 <code>Import</code> 注解的 <code>3</code> 种使用方式，然后通过分析源码和处理过程示意图解释它是如何导入（注册） <code>BeanDefinition</code> 的。</p>
-<span id="more"></span>
-
-<ul>
-<li>本文的写作动机继承自<a href="/2023/11/23/source-code-analysis-of-Spring-Configuration-annotation/" title="Spring @Configuration 注解的源码分析">Spring @Configuration 注解的源码分析</a>，处理 <code>@Import</code> 是处理 <code>@Configuration</code> 过程的一部分。</li>
-</ul>
-<h2 id="使用方式"><a href="#使用方式" class="headerlink" title="使用方式"></a>使用方式</h2><p><code>Import</code> 注解有 <code>3</code> 种导入（注册） <code>BeanDefinition</code> 的方式：</p>
-<ol>
-<li>使用 <code>Import</code> 将目标类的 <code>Class</code> 对象，解析为 <code>BeanDefinition</code> 并注册。</li>
-<li>使用 <code>Import</code> 配合 <code>ImportSelector</code> 的实现类，将 <code>selectImports</code> 方法返回的所有全限定类名字符串，解析为 <code>BeanDefinition</code> 并注册。</li>
-<li>使用 <code>Import</code> 配合 <code>ImportBeanDefinitionRegistra</code>r 的实现类，在 <code>registerBeanDefinitions</code> 方法中，直接向 <code>BeanDefinitionRegistry</code> 中注册 <code>BeanDefinition</code>。</li>
-</ol>
-<h2 id="测试用例"><a href="#测试用例" class="headerlink" title="测试用例"></a>测试用例</h2><p>测试了使用 <code>Import</code> 注解的 <code>3</code> 种方式：</p>
-<ol>
-<li>使用 <code>Import</code> 直接导入（注册） <code>Red</code>。</li>
-<li>配合 <code>ImportBeanDefinitionRegistrar</code> 间接注册 <code>Color</code>。</li>
-<li>配合 <code>ImportSelector</code> 间接导入（注册） <code>Blue</code>。</li>
-</ol>
-<p>用例中的特别地测试了以下两种情况：</p>
-<ol>
-<li>使用 <code>Import</code> 直接导入和配合 <code>ImportSelector</code> 间接导入相同的类 <code>Red</code> 只会注册一个 <code>BeanDefinition</code>。</li>
-<li>尽管 <code>MyImportSelector</code> 书面顺序在 <code>MyImportBeanDefinitionRegistrar</code> 之后，但是 <code>MyImportBeanDefinitionRegistrar</code> 判断 <code>registry</code> 是否包含在 <code>MyImportSelector</code> 导入的类 <code>Blue</code> 时，不受顺序影响。</li>
-</ol>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="meta">@Configuration</span></span><br><span class="line"><span class="meta">@Import(&#123;Red.class, MyImportBeanDefinitionRegistrar.class, MyImportSelector.class,&#125;)</span></span><br><span class="line"><span class="keyword">public</span> <span class="keyword">class</span> <span class="title class_">ImportConfig</span> &#123;</span><br><span class="line">&#125;</span><br><span class="line"></span><br><span class="line"><span class="keyword">public</span> <span class="keyword">class</span> <span class="title class_">MyImportBeanDefinitionRegistrar</span> <span class="keyword">implements</span> <span class="title class_">ImportBeanDefinitionRegistrar</span> &#123;</span><br><span class="line"></span><br><span class="line">    <span class="meta">@Override</span></span><br><span class="line">    <span class="keyword">public</span> <span class="keyword">void</span> <span class="title function_">registerBeanDefinitions</span><span class="params">(AnnotationMetadata importingClassMetadata, BeanDefinitionRegistry registry)</span> &#123;</span><br><span class="line">        <span class="type">boolean</span> <span class="variable">hasRed</span> <span class="operator">=</span> registry.containsBeanDefinition(<span class="string">&quot;com.moralok.bean.Red&quot;</span>);</span><br><span class="line">        <span class="type">boolean</span> <span class="variable">hasBlue</span> <span class="operator">=</span> registry.containsBeanDefinition(<span class="string">&quot;com.moralok.bean.Blue&quot;</span>);</span><br><span class="line">        <span class="keyword">if</span> (hasRed &amp;&amp; hasBlue) &#123;</span><br><span class="line">            <span class="type">BeanDefinition</span> <span class="variable">beanDefinition</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">RootBeanDefinition</span>(Color.class);</span><br><span class="line">            registry.registerBeanDefinition(<span class="string">&quot;color&quot;</span>, beanDefinition);</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br><span class="line"></span><br><span class="line"><span class="keyword">public</span> <span class="keyword">class</span> <span class="title class_">MyImportSelector</span> <span class="keyword">implements</span> <span class="title class_">ImportSelector</span> &#123;</span><br><span class="line"></span><br><span class="line">    <span class="meta">@Override</span></span><br><span class="line">    <span class="keyword">public</span> String[] selectImports(AnnotationMetadata annotationMetadata) &#123;</span><br><span class="line">        <span class="keyword">return</span> <span class="keyword">new</span> <span class="title class_">String</span>[] &#123;<span class="string">&quot;com.moralok.bean.Blue&quot;</span>, <span class="string">&quot;com.moralok.bean.Red&quot;</span>&#125;;</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br><span class="line"></span><br><span class="line"><span class="keyword">public</span> <span class="keyword">class</span> <span class="title class_">Color</span> &#123;</span><br><span class="line">&#125;</span><br><span class="line"></span><br><span class="line"><span class="keyword">public</span> <span class="keyword">class</span> <span class="title class_">Red</span> &#123;</span><br><span class="line">&#125;</span><br><span class="line"></span><br><span class="line"><span class="keyword">public</span> <span class="keyword">class</span> <span class="title class_">Blue</span> &#123;</span><br><span class="line">&#125;</span><br><span class="line"></span><br><span class="line"><span class="keyword">public</span> <span class="keyword">class</span> <span class="title class_">IocTest</span> &#123;</span><br><span class="line">    <span class="meta">@Test</span></span><br><span class="line">    <span class="keyword">public</span> <span class="keyword">void</span> <span class="title function_">importTest</span><span class="params">()</span> &#123;</span><br><span class="line">        <span class="type">ApplicationContext</span> <span class="variable">ac</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">AnnotationConfigApplicationContext</span>(ImportConfig.class);</span><br><span class="line">        String[] beanDefinitionNames = ac.getBeanDefinitionNames();</span><br><span class="line">        <span class="keyword">for</span> (String name : beanDefinitionNames) &#123;</span><br><span class="line">            System.out.println(<span class="string">&quot;beanDefinitionName..........&quot;</span> + name);</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
-
-<p>测试结果</p>
-<figure class="highlight console"><table><tr><td class="code"><pre><span class="line">......</span><br><span class="line">beanDefinitionName..........importConfig</span><br><span class="line">beanDefinitionName..........com.moralok.bean.Red</span><br><span class="line">beanDefinitionName..........com.moralok.bean.Blue</span><br><span class="line">beanDefinitionName..........color</span><br></pre></td></tr></table></figure>
+<p>测试结果</p>
+<figure class="highlight console"><table><tr><td class="code"><pre><span class="line">......</span><br><span class="line">beanDefinitionName..........importConfig</span><br><span class="line">beanDefinitionName..........com.moralok.bean.Red</span><br><span class="line">beanDefinitionName..........com.moralok.bean.Blue</span><br><span class="line">beanDefinitionName..........color</span><br></pre></td></tr></table></figure>
 
 <h2 id="源码分析"><a href="#源码分析" class="headerlink" title="源码分析"></a>源码分析</h2><p>关于 <code>Import</code> 注解的源码分析需要建立在对关于 <code>Configuration</code> 注解的源码的了解基础上，因为前者是 <code>Spring</code> 解析配置类处理过程的一部分，可以参考文章:</p>
 <ul>
@@ -4548,65 +4189,6 @@
         <tag>spring</tag>
       </tags>
   </entry>
-  <entry>
-    <title>ConfigurationProperties 一定要搭配 EnableConfigurationProperties 使用吗</title>
-    <url>/2023/12/10/is-it-necessary-to-use-ConfigurationProperties-with-EnableConfigurationProperties/</url>
-    <content><![CDATA[<p><code>@ConfigurationProperties</code> 和 <code>@EnableConfigurationProperties</code> 是 <code>Spring Boot</code> 中常用的注解，提供了方便和强大的外部化配置支持。尽管它们常常一起出现，但是它们真的必须一起使用吗？<code>Spring Boot</code> 的灵活性常常让我们忽略配置背后产生的作用究竟是什么？本文将从源码角度出发分析两个注解的<strong>作用时机</strong>和<strong>工作原理</strong>。</p>
-<span id="more"></span>
-
-<ul>
-<li>本文的写作动机继承自<a href="/2023/12/07/use-and-analysis-of-PropertySource-annotation-in-Spring/" title="Spring 中 @PropertySource 注解的使用和源码分析">Spring 中 @PropertySource 注解的使用和源码分析</a>，两者有点相似并且常被一起提及，都通过外部配置管理运行时的属性值，但实际的工作原理却并不相同。</li>
-<li>本文没有介绍它们的使用方式，如有需要可以参考 <a href="https://www.baeldung.com/configuration-properties-in-spring-boot">Guide to @ConfigurationProperties in Spring Boot</a>。</li>
-<li>理解 <code>@Import</code> 的工作原理对阅读本文的源码有非常大的帮助，可以参考<a href="/2023/12/04/use-and-analysis-of-Import-annotation-in-Spring/" title="Spring 中 @Import 注解的使用和源码分析">Spring 中 @Import 注解的使用和源码分析</a>。</li>
-</ul>
-<h2 id="注解"><a href="#注解" class="headerlink" title="注解"></a>注解</h2><p><code>ConfigurationProperties</code> 是用于<strong>外部化配置</strong>的注解。如果你想<strong>绑定</strong>和<strong>验证</strong>某些外部属性（例如来自 <code>.properties</code> 文件），就将其添加到<strong>类定义或 <code>@Configuration</code> 类中的 <code>@Bean</code> 方法</strong>。请注意，和 <code>@Value</code> 相反，<code>SpEL</code> 表达式不会被求值，因为属性值是外部化的。查看 <code>ConfigurationProperties</code> 注解的源码可知，该注解主要起到标记和存储一些信息的作用。</p>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="meta">@Target(&#123; ElementType.TYPE, ElementType.METHOD &#125;)</span></span><br><span class="line"><span class="meta">@Retention(RetentionPolicy.RUNTIME)</span></span><br><span class="line"><span class="meta">@Documented</span></span><br><span class="line"><span class="keyword">public</span> <span class="meta">@interface</span> ConfigurationProperties &#123;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 可有效绑定到此对象的属性的名称前缀</span></span><br><span class="line">    <span class="meta">@AliasFor(&quot;prefix&quot;)</span></span><br><span class="line">    String <span class="title function_">value</span><span class="params">()</span> <span class="keyword">default</span> <span class="string">&quot;&quot;</span>;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 可有效绑定到此对象的属性的名称前缀</span></span><br><span class="line">    <span class="meta">@AliasFor(&quot;value&quot;)</span></span><br><span class="line">    String <span class="title function_">prefix</span><span class="params">()</span> <span class="keyword">default</span> <span class="string">&quot;&quot;</span>;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 绑定到此对象时是否忽略无效字段</span></span><br><span class="line">    <span class="type">boolean</span> <span class="title function_">ignoreInvalidFields</span><span class="params">()</span> <span class="keyword">default</span> <span class="literal">false</span>;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 绑定到此对象时是否忽略未知字段</span></span><br><span class="line">    <span class="type">boolean</span> <span class="title function_">ignoreUnknownFields</span><span class="params">()</span> <span class="keyword">default</span> <span class="literal">true</span>;</span><br><span class="line"></span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
-
-<p>查看 <code>EnableConfigurationProperties</code> 的源码，我们注意到它通过 <code>@Import</code> 导入了 <code>EnableConfigurationPropertiesImportSelector</code>。</p>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="meta">@Target(ElementType.TYPE)</span></span><br><span class="line"><span class="meta">@Retention(RetentionPolicy.RUNTIME)</span></span><br><span class="line"><span class="meta">@Documented</span></span><br><span class="line"><span class="meta">@Import(EnableConfigurationPropertiesImportSelector.class)</span></span><br><span class="line"><span class="keyword">public</span> <span class="meta">@interface</span> EnableConfigurationProperties &#123;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 使用 Spring 快速注册标注了 @ConfigurationProperties 的 bean。无论 value 如何，标准的 Spring Bean 也将被扫描。</span></span><br><span class="line">    Class&lt;?&gt;[] value() <span class="keyword">default</span> &#123;&#125;;</span><br><span class="line"></span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
-
-<h2 id="注解的作用"><a href="#注解的作用" class="headerlink" title="注解的作用"></a>注解的作用</h2><p>查看 <code>EnableConfigurationPropertiesImportSelector</code> 的源码，关注 <code>selectImports</code> 方法。该方法返回了 <code>ConfigurationPropertiesBeanRegistrar</code> 和 <code>ConfigurationPropertiesBindingPostProcessorRegistrar</code> 的全限定类名，<code>Spring</code> 将注册它们。</p>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">class</span> <span class="title class_">EnableConfigurationPropertiesImportSelector</span> <span class="keyword">implements</span> <span class="title class_">ImportSelector</span> &#123;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">static</span> <span class="keyword">final</span> String[] IMPORTS = &#123;</span><br><span class="line">            ConfigurationPropertiesBeanRegistrar.class.getName(),</span><br><span class="line">            ConfigurationPropertiesBindingPostProcessorRegistrar.class.getName() &#125;;</span><br><span class="line"></span><br><span class="line">    <span class="meta">@Override</span></span><br><span class="line">    <span class="keyword">public</span> String[] selectImports(AnnotationMetadata metadata) &#123;</span><br><span class="line">        <span class="keyword">return</span> IMPORTS;</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
-
-<h3 id="注册目标类"><a href="#注册目标类" class="headerlink" title="注册目标类"></a>注册目标类</h3><p><code>ConfigurationPropertiesBeanRegistrar</code> 是一个内部类，查看 <code>ConfigurationPropertiesBeanRegistrar</code> 的源码，关注 <code>registerBeanDefinitions</code> 方法。注册的目标来自于：</p>
-<ul>
-<li><code>@EnableConfigurationProperties</code> 的 <code>value</code> 所指定的类中</li>
-<li>且标注了 <code>@ConfigurationProperties</code> 的类</li>
-</ul>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">class</span> <span class="title class_">ConfigurationPropertiesBeanRegistrar</span></span><br><span class="line">        <span class="keyword">implements</span> <span class="title class_">ImportBeanDefinitionRegistrar</span> &#123;</span><br><span class="line"></span><br><span class="line">    <span class="meta">@Override</span></span><br><span class="line">    <span class="keyword">public</span> <span class="keyword">void</span> <span class="title function_">registerBeanDefinitions</span><span class="params">(AnnotationMetadata metadata,</span></span><br><span class="line"><span class="params">            BeanDefinitionRegistry registry)</span> &#123;</span><br><span class="line">        <span class="comment">// 1. 获取要注册的 Class</span></span><br><span class="line">        <span class="comment">// 2. 遍历获取的结果进行注册</span></span><br><span class="line">        getTypes(metadata).forEach((type) -&gt; register(registry,</span><br><span class="line">                (ConfigurableListableBeanFactory) registry, type));</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line"></span><br><span class="line">    <span class="keyword">private</span> List&lt;Class&lt;?&gt;&gt; getTypes(AnnotationMetadata metadata) &#123;</span><br><span class="line">        <span class="comment">// 获取所有 @EnableConfigurationProperties 的属性</span></span><br><span class="line">        MultiValueMap&lt;String, Object&gt; attributes = metadata</span><br><span class="line">                .getAllAnnotationAttributes(</span><br><span class="line">                        EnableConfigurationProperties.class.getName(), <span class="literal">false</span>);</span><br><span class="line">        <span class="comment">// 获取属性 value 的值，处理后返回</span></span><br><span class="line">        <span class="keyword">return</span> collectClasses(attributes == <span class="literal">null</span> ? Collections.emptyList()</span><br><span class="line">                : attributes.get(<span class="string">&quot;value&quot;</span>));</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 收集 Class</span></span><br><span class="line">    <span class="keyword">private</span> List&lt;Class&lt;?&gt;&gt; collectClasses(List&lt;?&gt; values) &#123;</span><br><span class="line">        <span class="keyword">return</span> values.stream().flatMap((value) -&gt; Arrays.stream((Object[]) value))</span><br><span class="line">                .map((o) -&gt; (Class&lt;?&gt;) o).filter((type) -&gt; <span class="keyword">void</span>.class != type)</span><br><span class="line">                .collect(Collectors.toList());</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 注册 Bean 定义</span></span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">void</span> <span class="title function_">register</span><span class="params">(BeanDefinitionRegistry registry,</span></span><br><span class="line"><span class="params">            ConfigurableListableBeanFactory beanFactory, Class&lt;?&gt; type)</span> &#123;</span><br><span class="line">        <span class="type">String</span> <span class="variable">name</span> <span class="operator">=</span> getName(type);</span><br><span class="line">        <span class="comment">// 检测是否包含 Bean 定义</span></span><br><span class="line">        <span class="keyword">if</span> (!containsBeanDefinition(beanFactory, name)) &#123;</span><br><span class="line">            <span class="comment">// 如果没找到，则注册</span></span><br><span class="line">            registerBeanDefinition(registry, name, type);</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// beanName = prefix + 全限定类名 or 全限定类名</span></span><br><span class="line">    <span class="keyword">private</span> String <span class="title function_">getName</span><span class="params">(Class&lt;?&gt; type)</span> &#123;</span><br><span class="line">        <span class="type">ConfigurationProperties</span> <span class="variable">annotation</span> <span class="operator">=</span> AnnotationUtils.findAnnotation(type,</span><br><span class="line">                ConfigurationProperties.class);</span><br><span class="line">        <span class="type">String</span> <span class="variable">prefix</span> <span class="operator">=</span> (annotation != <span class="literal">null</span> ? annotation.prefix() : <span class="string">&quot;&quot;</span>);</span><br><span class="line">        <span class="keyword">return</span> (StringUtils.hasText(prefix) ? prefix + <span class="string">&quot;-&quot;</span> + type.getName()</span><br><span class="line">                : type.getName());</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 检测是否包含 Bean 定义</span></span><br><span class="line">    <span class="keyword">private</span> <span class="type">boolean</span> <span class="title function_">containsBeanDefinition</span><span class="params">(</span></span><br><span class="line"><span class="params">            ConfigurableListableBeanFactory beanFactory, String name)</span> &#123;</span><br><span class="line">        <span class="comment">// 先检测当前工厂中是否包含</span></span><br><span class="line">        <span class="keyword">if</span> (beanFactory.containsBeanDefinition(name)) &#123;</span><br><span class="line">            <span class="keyword">return</span> <span class="literal">true</span>;</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="comment">// 如果没找到则检测父工厂是否包含</span></span><br><span class="line">        <span class="type">BeanFactory</span> <span class="variable">parent</span> <span class="operator">=</span> beanFactory.getParentBeanFactory();</span><br><span class="line">        <span class="keyword">if</span> (parent <span class="keyword">instanceof</span> ConfigurableListableBeanFactory) &#123;</span><br><span class="line">            <span class="keyword">return</span> containsBeanDefinition((ConfigurableListableBeanFactory) parent,</span><br><span class="line">                    name);</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="keyword">return</span> <span class="literal">false</span>;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 注册 Bean 定义</span></span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">void</span> <span class="title function_">registerBeanDefinition</span><span class="params">(BeanDefinitionRegistry registry, String name,</span></span><br><span class="line"><span class="params">            Class&lt;?&gt; type)</span> &#123;</span><br><span class="line">        <span class="comment">// 断言目标类标注了 @ConfigurationProperties</span></span><br><span class="line">        assertHasAnnotation(type);</span><br><span class="line">        <span class="type">GenericBeanDefinition</span> <span class="variable">definition</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">GenericBeanDefinition</span>();</span><br><span class="line">        definition.setBeanClass(type);</span><br><span class="line">        <span class="comment">// registry 注册 Bean 定义</span></span><br><span class="line">        registry.registerBeanDefinition(name, definition);</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 断言目标类标注了 @ConfigurationProperties</span></span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">void</span> <span class="title function_">assertHasAnnotation</span><span class="params">(Class&lt;?&gt; type)</span> &#123;</span><br><span class="line">        Assert.notNull(</span><br><span class="line">                AnnotationUtils.findAnnotation(type, ConfigurationProperties.class),</span><br><span class="line">                <span class="string">&quot;No &quot;</span> + ConfigurationProperties.class.getSimpleName()</span><br><span class="line">                        + <span class="string">&quot; annotation found on  &#x27;&quot;</span> + type.getName() + <span class="string">&quot;&#x27;.&quot;</span>);</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
-
-<h3 id="注册后处理器"><a href="#注册后处理器" class="headerlink" title="注册后处理器"></a>注册后处理器</h3><p>查看 <code>ConfigurationPropertiesBindingPostProcessorRegistrar</code> 的源码，关注 <code>registerBeanDefinitions</code> 方法。该方法注册了 <code>ConfigurationPropertiesBindingPostProcessor</code> 和 <code>ConfigurationBeanFactoryMetadata</code>。</p>
-<ul>
-<li>前者顾名思义，用于处理 <code>ConfigurationProperties</code> 的绑定</li>
-<li>后者是用于在 <code>Bean</code> 工厂初始化期间记住 <code>@Bean</code> 定义元数据的实用程序类</li>
-</ul>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">class</span> <span class="title class_">ConfigurationPropertiesBindingPostProcessorRegistrar</span></span><br><span class="line">        <span class="keyword">implements</span> <span class="title class_">ImportBeanDefinitionRegistrar</span> &#123;</span><br><span class="line"></span><br><span class="line">    <span class="meta">@Override</span></span><br><span class="line">    <span class="keyword">public</span> <span class="keyword">void</span> <span class="title function_">registerBeanDefinitions</span><span class="params">(AnnotationMetadata importingClassMetadata,</span></span><br><span class="line"><span class="params">            BeanDefinitionRegistry registry)</span> &#123;</span><br><span class="line">        <span class="keyword">if</span> (!registry.containsBeanDefinition(</span><br><span class="line">                ConfigurationPropertiesBindingPostProcessor.BEAN_NAME)) &#123;</span><br><span class="line">            registerConfigurationPropertiesBindingPostProcessor(registry);</span><br><span class="line">            registerConfigurationBeanFactoryMetadata(registry);</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">void</span> <span class="title function_">registerConfigurationPropertiesBindingPostProcessor</span><span class="params">(</span></span><br><span class="line"><span class="params">            BeanDefinitionRegistry registry)</span> &#123;</span><br><span class="line">        <span class="type">GenericBeanDefinition</span> <span class="variable">definition</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">GenericBeanDefinition</span>();</span><br><span class="line">        definition.setBeanClass(ConfigurationPropertiesBindingPostProcessor.class);</span><br><span class="line">        <span class="comment">// Bean 定义的角色为基础设施</span></span><br><span class="line">        definition.setRole(BeanDefinition.ROLE_INFRASTRUCTURE);</span><br><span class="line">        registry.registerBeanDefinition(</span><br><span class="line">                ConfigurationPropertiesBindingPostProcessor.BEAN_NAME, definition);</span><br><span class="line"></span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">void</span> <span class="title function_">registerConfigurationBeanFactoryMetadata</span><span class="params">(</span></span><br><span class="line"><span class="params">            BeanDefinitionRegistry registry)</span> &#123;</span><br><span class="line">        <span class="type">GenericBeanDefinition</span> <span class="variable">definition</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">GenericBeanDefinition</span>();</span><br><span class="line">        definition.setBeanClass(ConfigurationBeanFactoryMetadata.class);</span><br><span class="line">        definition.setRole(BeanDefinition.ROLE_INFRASTRUCTURE);</span><br><span class="line">        registry.registerBeanDefinition(ConfigurationBeanFactoryMetadata.BEAN_NAME,</span><br><span class="line">                definition);</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
-
-<h2 id="绑定"><a href="#绑定" class="headerlink" title="绑定"></a>绑定</h2><p><code>ConfigurationPropertiesBindingPostProcessor</code> 是用于 <code>ConfigurationProperties</code> 绑定的后处理器，关注 <code>afterPropertiesSet</code> 方法还有核心方法 <code>postProcessBeforeInitialization</code>。</p>
-<ul>
-<li>在 <code>afterPropertiesSet</code> 方法中，它获取到了和自己一起注册的 <code>ConfigurationBeanFactoryMetadata</code>。</li>
-<li>在 <code>postProcessBeforeInitialization</code> 方法中，先获取 <code>@ConfigurationProperties</code>，再进行绑定。</li>
-</ul>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">class</span> <span class="title class_">ConfigurationPropertiesBindingPostProcessor</span> <span class="keyword">implements</span> <span class="title class_">BeanPostProcessor</span>,</span><br><span class="line">        PriorityOrdered, ApplicationContextAware, InitializingBean &#123;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">final</span> <span class="type">String</span> <span class="variable">BEAN_NAME</span> <span class="operator">=</span> ConfigurationPropertiesBindingPostProcessor.class</span><br><span class="line">            .getName();</span><br><span class="line"></span><br><span class="line">    <span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">final</span> <span class="type">String</span> <span class="variable">VALIDATOR_BEAN_NAME</span> <span class="operator">=</span> <span class="string">&quot;configurationPropertiesValidator&quot;</span>;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">private</span> ConfigurationBeanFactoryMetadata beanFactoryMetadata;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">private</span> ApplicationContext applicationContext;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">private</span> ConfigurationPropertiesBinder configurationPropertiesBinder;</span><br><span class="line"></span><br><span class="line">    <span class="meta">@Override</span></span><br><span class="line">    <span class="keyword">public</span> <span class="keyword">void</span> <span class="title function_">setApplicationContext</span><span class="params">(ApplicationContext applicationContext)</span></span><br><span class="line">            <span class="keyword">throws</span> BeansException &#123;</span><br><span class="line">        <span class="built_in">this</span>.applicationContext = applicationContext;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="meta">@Override</span></span><br><span class="line">    <span class="keyword">public</span> <span class="keyword">void</span> <span class="title function_">afterPropertiesSet</span><span class="params">()</span> <span class="keyword">throws</span> Exception &#123;</span><br><span class="line">        <span class="comment">// We can&#x27;t use constructor injection of the application context because</span></span><br><span class="line">        <span class="comment">// it causes eager factory bean initialization</span></span><br><span class="line">        <span class="comment">// 注入了 ConfigurationBeanFactoryMetadata（不理解注解描述的情况？）</span></span><br><span class="line">        <span class="built_in">this</span>.beanFactoryMetadata = <span class="built_in">this</span>.applicationContext.getBean(</span><br><span class="line">                ConfigurationBeanFactoryMetadata.BEAN_NAME,</span><br><span class="line">                ConfigurationBeanFactoryMetadata.class);</span><br><span class="line">        <span class="built_in">this</span>.configurationPropertiesBinder = <span class="keyword">new</span> <span class="title class_">ConfigurationPropertiesBinder</span>(</span><br><span class="line">                <span class="built_in">this</span>.applicationContext, VALIDATOR_BEAN_NAME);</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="meta">@Override</span></span><br><span class="line">    <span class="keyword">public</span> <span class="type">int</span> <span class="title function_">getOrder</span><span class="params">()</span> &#123;</span><br><span class="line">        <span class="keyword">return</span> Ordered.HIGHEST_PRECEDENCE + <span class="number">1</span>;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="meta">@Override</span></span><br><span class="line">    <span class="keyword">public</span> Object <span class="title function_">postProcessBeforeInitialization</span><span class="params">(Object bean, String beanName)</span></span><br><span class="line">            <span class="keyword">throws</span> BeansException &#123;</span><br><span class="line">        <span class="comment">// 获取 @ConfigurationProperties</span></span><br><span class="line">        <span class="type">ConfigurationProperties</span> <span class="variable">annotation</span> <span class="operator">=</span> getAnnotation(bean, beanName,</span><br><span class="line">                ConfigurationProperties.class);</span><br><span class="line">        <span class="keyword">if</span> (annotation != <span class="literal">null</span>) &#123;</span><br><span class="line">            <span class="comment">// 绑定</span></span><br><span class="line">            bind(bean, beanName, annotation);</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="keyword">return</span> bean;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">void</span> <span class="title function_">bind</span><span class="params">(Object bean, String beanName, ConfigurationProperties annotation)</span> &#123;</span><br><span class="line">        <span class="comment">// 获取 Bean 的类型</span></span><br><span class="line">        <span class="type">ResolvableType</span> <span class="variable">type</span> <span class="operator">=</span> getBeanType(bean, beanName);</span><br><span class="line">        <span class="comment">// 获取 @Validated 用于校验</span></span><br><span class="line">        <span class="type">Validated</span> <span class="variable">validated</span> <span class="operator">=</span> getAnnotation(bean, beanName, Validated.class);</span><br><span class="line">        Annotation[] annotations = (validated == <span class="literal">null</span> ? <span class="keyword">new</span> <span class="title class_">Annotation</span>[] &#123; annotation &#125;</span><br><span class="line">                : <span class="keyword">new</span> <span class="title class_">Annotation</span>[] &#123; annotation, validated &#125;);</span><br><span class="line">        <span class="comment">// 创建 Bindable 对象</span></span><br><span class="line">        Bindable&lt;?&gt; target = Bindable.of(type).withExistingValue(bean)</span><br><span class="line">                .withAnnotations(annotations);</span><br><span class="line">        <span class="keyword">try</span> &#123;</span><br><span class="line">            <span class="comment">// 绑定</span></span><br><span class="line">            <span class="built_in">this</span>.configurationPropertiesBinder.bind(target);</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="keyword">catch</span> (Exception ex) &#123;</span><br><span class="line">            <span class="keyword">throw</span> <span class="keyword">new</span> <span class="title class_">ConfigurationPropertiesBindException</span>(beanName, bean, annotation,</span><br><span class="line">                    ex);</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">private</span> ResolvableType <span class="title function_">getBeanType</span><span class="params">(Object bean, String beanName)</span> &#123;</span><br><span class="line">        <span class="comment">// 先查找工厂方法</span></span><br><span class="line">        <span class="type">Method</span> <span class="variable">factoryMethod</span> <span class="operator">=</span> <span class="built_in">this</span>.beanFactoryMetadata.findFactoryMethod(beanName);</span><br><span class="line">        <span class="keyword">if</span> (factoryMethod != <span class="literal">null</span>) &#123;</span><br><span class="line">            <span class="comment">// 如果存在，返回工厂方法的返回值类型</span></span><br><span class="line">            <span class="keyword">return</span> ResolvableType.forMethodReturnType(factoryMethod);</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="comment">// 否则返回 bean 的类型（难道 bean 的类型不是工厂方法的返回值类型吗？）</span></span><br><span class="line">        <span class="keyword">return</span> ResolvableType.forClass(bean.getClass());</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">private</span> &lt;A <span class="keyword">extends</span> <span class="title class_">Annotation</span>&gt; A <span class="title function_">getAnnotation</span><span class="params">(Object bean, String beanName,</span></span><br><span class="line"><span class="params">            Class&lt;A&gt; type)</span> &#123;</span><br><span class="line">        <span class="comment">// 先到 @Bean 方法中获取</span></span><br><span class="line">        <span class="type">A</span> <span class="variable">annotation</span> <span class="operator">=</span> <span class="built_in">this</span>.beanFactoryMetadata.findFactoryAnnotation(beanName, type);</span><br><span class="line">        <span class="keyword">if</span> (annotation == <span class="literal">null</span>) &#123;</span><br><span class="line">            <span class="comment">// 如果没有，再到类上获取</span></span><br><span class="line">            annotation = AnnotationUtils.findAnnotation(bean.getClass(), type);</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="keyword">return</span> annotation;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
-
-<p><code>ConfigurationBeanFactoryMetadata</code> 是用于在 <code>Bean</code> 工厂初始化期间记住 <code>@Bean</code> 定义元数据的实用程序类。在前面我们介绍过 <code>@ConfigurationProperties</code> 不仅可以添加到类定义，还可以用于标注 <code>@Bean</code> 方法，<code>ConfigurationBeanFactoryMetadata</code> 正是应用于在后者这类情况下获取 <code>@ConfigurationProperties</code>。</p>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">class</span> <span class="title class_">ConfigurationBeanFactoryMetadata</span> <span class="keyword">implements</span> <span class="title class_">BeanFactoryPostProcessor</span> &#123;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">final</span> Map&lt;String, FactoryMetadata&gt; beansFactoryMetadata = <span class="keyword">new</span> <span class="title class_">HashMap</span>&lt;&gt;();</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 后处理 BeanFactory</span></span><br><span class="line">    <span class="meta">@Override</span></span><br><span class="line">    <span class="keyword">public</span> <span class="keyword">void</span> <span class="title function_">postProcessBeanFactory</span><span class="params">(ConfigurableListableBeanFactory beanFactory)</span></span><br><span class="line">            <span class="keyword">throws</span> BeansException &#123;</span><br><span class="line">        <span class="built_in">this</span>.beanFactory = beanFactory;</span><br><span class="line">        <span class="comment">// 遍历 Bean 定义</span></span><br><span class="line">        <span class="keyword">for</span> (String name : beanFactory.getBeanDefinitionNames()) &#123;</span><br><span class="line">            <span class="type">BeanDefinition</span> <span class="variable">definition</span> <span class="operator">=</span> beanFactory.getBeanDefinition(name);</span><br><span class="line">            <span class="type">String</span> <span class="variable">method</span> <span class="operator">=</span> definition.getFactoryMethodName();</span><br><span class="line">            <span class="type">String</span> <span class="variable">bean</span> <span class="operator">=</span> definition.getFactoryBeanName();、</span><br><span class="line">            <span class="comment">// 检测是否是一个 @Bean 方法对应的 Bean 定义</span></span><br><span class="line">            <span class="keyword">if</span> (method != <span class="literal">null</span> &amp;&amp; bean != <span class="literal">null</span>) &#123;</span><br><span class="line">                <span class="built_in">this</span>.beansFactoryMetadata.put(name, <span class="keyword">new</span> <span class="title class_">FactoryMetadata</span>(bean, method));</span><br><span class="line">            &#125;</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 获取工厂方法上的注解</span></span><br><span class="line">    <span class="keyword">public</span> &lt;A <span class="keyword">extends</span> <span class="title class_">Annotation</span>&gt; A <span class="title function_">findFactoryAnnotation</span><span class="params">(String beanName,</span></span><br><span class="line"><span class="params">			Class&lt;A&gt; type)</span> &#123;</span><br><span class="line">		<span class="type">Method</span> <span class="variable">method</span> <span class="operator">=</span> findFactoryMethod(beanName);</span><br><span class="line">		<span class="keyword">return</span> (method == <span class="literal">null</span> ? <span class="literal">null</span> : AnnotationUtils.findAnnotation(method, type));</span><br><span class="line">	&#125;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 获取工厂方法</span></span><br><span class="line">	<span class="keyword">public</span> Method <span class="title function_">findFactoryMethod</span><span class="params">(String beanName)</span> &#123;</span><br><span class="line">		<span class="keyword">if</span> (!<span class="built_in">this</span>.beansFactoryMetadata.containsKey(beanName)) &#123;</span><br><span class="line">			<span class="keyword">return</span> <span class="literal">null</span>;</span><br><span class="line">		&#125;</span><br><span class="line">		AtomicReference&lt;Method&gt; found = <span class="keyword">new</span> <span class="title class_">AtomicReference</span>&lt;&gt;(<span class="literal">null</span>);</span><br><span class="line">		<span class="type">FactoryMetadata</span> <span class="variable">metadata</span> <span class="operator">=</span> <span class="built_in">this</span>.beansFactoryMetadata.get(beanName);</span><br><span class="line">		Class&lt;?&gt; factoryType = <span class="built_in">this</span>.beanFactory.getType(metadata.getBean());</span><br><span class="line">		<span class="type">String</span> <span class="variable">factoryMethod</span> <span class="operator">=</span> metadata.getMethod();</span><br><span class="line">        <span class="comment">// 如果是代理类，获取其父类</span></span><br><span class="line">		<span class="keyword">if</span> (ClassUtils.isCglibProxyClass(factoryType)) &#123;</span><br><span class="line">			factoryType = factoryType.getSuperclass();</span><br><span class="line">		&#125;</span><br><span class="line">        <span class="comment">// 遍历声明的方法进行匹配（名字相同即可没问题吗？）</span></span><br><span class="line">		ReflectionUtils.doWithMethods(factoryType, (method) -&gt; &#123;</span><br><span class="line">			<span class="keyword">if</span> (method.getName().equals(factoryMethod)) &#123;</span><br><span class="line">				found.compareAndSet(<span class="literal">null</span>, method);</span><br><span class="line">			&#125;</span><br><span class="line">		&#125;);</span><br><span class="line">		<span class="keyword">return</span> found.get();</span><br><span class="line">	&#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
-
-<h2 id="总结"><a href="#总结" class="headerlink" title="总结"></a>总结</h2><p><code>@EnableConfigurationProperties</code> 的目的有两个：</p>
-<ul>
-<li>注册目标</li>
-<li>注册后处理器用于在目标进行 <code>Bean</code> 初始化工作时，介入进行绑定</li>
-</ul>
-<p>尽管注册目标时的操作有些巧妙，但是还是要明白 <code>ConfigurationProperties</code> 类只是单纯的被注册了而已。对于后处理器而言，无论一个 <code>ConfigurationProperties</code> 类是不是通过注解注册，后处理器都会一视同仁地进行绑定。但同时，你又要知道后处理器也是通过 <code>@EnableConfigurationProperties</code> 注册的，因此你需要保证至少有一个 <code>@EnableConfigurationProperties</code> 标注的类被注册（并被处理了 <code>@Import</code>）。<br>在 <code>Spring Boot</code> 中，<code>@SpringBootApplication</code> 通过 <code>@EnableAutoConfiguration</code> 启用了自动配置，从而注册了 <code>ConfigurationPropertiesAutoConfiguration</code>，<code>ConfigurationPropertiesAutoConfiguration</code> 标注了 <code>@EnableConfigurationProperties</code>。因此，对于 <code>Spring Boot</code> 而言，扫描范围内的所有 <code>ConfigurationProperties</code> 类，其实都不需要 <code>@EnableAutoConfiguration</code>。事实上，由于默认生成的 <code>beanName</code> 不同，多余的配置还会重复注册两个 <code>Bean</code> 定义。</p>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="meta">@Configuration</span></span><br><span class="line"><span class="meta">@EnableConfigurationProperties</span></span><br><span class="line"><span class="keyword">public</span> <span class="keyword">class</span> <span class="title class_">ConfigurationPropertiesAutoConfiguration</span> &#123;</span><br><span class="line"></span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
-
-]]></content>
-      <tags>
-        <tag>java</tag>
-        <tag>spring</tag>
-        <tag>spring boot</tag>
-      </tags>
-  </entry>
   <entry>
     <title>Spring AutowiredAnnotationBeanPostProcessor 的源码分析</title>
     <url>/2023/12/08/source-code-analysis-of-AutowiredAnnotationBeanPostProcessor-in-Spring/</url>
@@ -4723,17 +4305,193 @@
       </tags>
   </entry>
   <entry>
-    <title>当 MySQL 以 skip-name-resolve 模式启动时如何使用 grant 命令</title>
-    <url>/2023/12/13/how-to-grant-when-MySQL-started-with-skip-name-resolve-mode/</url>
-    <content><![CDATA[<p>本文介绍了 <code>MySQL</code> 中 <code>skip-name-resolve</code> 参数<strong>对连接的优化作用</strong>，随之而来的权限表<strong>仅可使用 <code>IP</code> 的限制</strong>，以及如何在无法提前确定 <code>IP</code> 的情况下使用 <code>grant</code> 命令<strong>搭配通配符 <code>%</code> 进行授权</strong>。</p>
+    <title>ConfigurationProperties 一定要搭配 EnableConfigurationProperties 使用吗</title>
+    <url>/2023/12/10/is-it-necessary-to-use-ConfigurationProperties-with-EnableConfigurationProperties/</url>
+    <content><![CDATA[<p><code>@ConfigurationProperties</code> 和 <code>@EnableConfigurationProperties</code> 是 <code>Spring Boot</code> 中常用的注解，提供了方便和强大的外部化配置支持。尽管它们常常一起出现，但是它们真的必须一起使用吗？<code>Spring Boot</code> 的灵活性常常让我们忽略配置背后产生的作用究竟是什么？本文将从源码角度出发分析两个注解的<strong>作用时机</strong>和<strong>工作原理</strong>。</p>
 <span id="more"></span>
 
-<h2 id="背景介绍"><a href="#背景介绍" class="headerlink" title="背景介绍"></a>背景介绍</h2><p>在 <code>MySQL</code> 新建一个用户 <code>exporter</code> 给 <code>mysqld-exporter</code> 使用，然后通过 <code>grant</code> 命令授予该用户部分权限。执行命令如下：</p>
-<figure class="highlight sql"><table><tr><td class="code"><pre><span class="line"><span class="keyword">CREATE</span> <span class="keyword">USER</span> <span class="string">&#x27;exporter&#x27;</span>@<span class="string">&#x27;localhost&#x27;</span> IDENTIFIED <span class="keyword">BY</span> <span class="string">&#x27;XXXXXXXX&#x27;</span> <span class="keyword">WITH</span> MAX_USER_CONNECTIONS <span class="number">3</span>;</span><br><span class="line"><span class="keyword">GRANT</span> PROCESS, REPLICATION CLIENT, <span class="keyword">SELECT</span> <span class="keyword">ON</span> <span class="operator">*</span>.<span class="operator">*</span> <span class="keyword">TO</span> <span class="string">&#x27;exporter&#x27;</span>@<span class="string">&#x27;localhost&#x27;</span>;</span><br></pre></td></tr></table></figure>
-
-<p>在执行时提示“这次 <code>grant</code> 需要关闭 <code>skip-name-resolve</code> 参数然后重启 <code>MySQL</code> 才能生效”。</p>
-<figure class="highlight console"><table><tr><td class="code"><pre><span class="line">0 row(s) affected, 1 warning(s): 1285 MySQL is started in --skip-name-resolve mode; you must restart it without this switch for this grant to work</span><br></pre></td></tr></table></figure>
-
+<ul>
+<li>本文的写作动机继承自<a href="/2023/12/07/use-and-analysis-of-PropertySource-annotation-in-Spring/" title="Spring 中 @PropertySource 注解的使用和源码分析">Spring 中 @PropertySource 注解的使用和源码分析</a>，两者有点相似并且常被一起提及，都通过外部配置管理运行时的属性值，但实际的工作原理却并不相同。</li>
+<li>本文没有介绍它们的使用方式，如有需要可以参考 <a href="https://www.baeldung.com/configuration-properties-in-spring-boot">Guide to @ConfigurationProperties in Spring Boot</a>。</li>
+<li>理解 <code>@Import</code> 的工作原理对阅读本文的源码有非常大的帮助，可以参考<a href="/2023/12/04/use-and-analysis-of-Import-annotation-in-Spring/" title="Spring 中 @Import 注解的使用和源码分析">Spring 中 @Import 注解的使用和源码分析</a>。</li>
+</ul>
+<h2 id="注解"><a href="#注解" class="headerlink" title="注解"></a>注解</h2><p><code>ConfigurationProperties</code> 是用于<strong>外部化配置</strong>的注解。如果你想<strong>绑定</strong>和<strong>验证</strong>某些外部属性（例如来自 <code>.properties</code> 文件），就将其添加到<strong>类定义或 <code>@Configuration</code> 类中的 <code>@Bean</code> 方法</strong>。请注意，和 <code>@Value</code> 相反，<code>SpEL</code> 表达式不会被求值，因为属性值是外部化的。查看 <code>ConfigurationProperties</code> 注解的源码可知，该注解主要起到标记和存储一些信息的作用。</p>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="meta">@Target(&#123; ElementType.TYPE, ElementType.METHOD &#125;)</span></span><br><span class="line"><span class="meta">@Retention(RetentionPolicy.RUNTIME)</span></span><br><span class="line"><span class="meta">@Documented</span></span><br><span class="line"><span class="keyword">public</span> <span class="meta">@interface</span> ConfigurationProperties &#123;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 可有效绑定到此对象的属性的名称前缀</span></span><br><span class="line">    <span class="meta">@AliasFor(&quot;prefix&quot;)</span></span><br><span class="line">    String <span class="title function_">value</span><span class="params">()</span> <span class="keyword">default</span> <span class="string">&quot;&quot;</span>;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 可有效绑定到此对象的属性的名称前缀</span></span><br><span class="line">    <span class="meta">@AliasFor(&quot;value&quot;)</span></span><br><span class="line">    String <span class="title function_">prefix</span><span class="params">()</span> <span class="keyword">default</span> <span class="string">&quot;&quot;</span>;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 绑定到此对象时是否忽略无效字段</span></span><br><span class="line">    <span class="type">boolean</span> <span class="title function_">ignoreInvalidFields</span><span class="params">()</span> <span class="keyword">default</span> <span class="literal">false</span>;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 绑定到此对象时是否忽略未知字段</span></span><br><span class="line">    <span class="type">boolean</span> <span class="title function_">ignoreUnknownFields</span><span class="params">()</span> <span class="keyword">default</span> <span class="literal">true</span>;</span><br><span class="line"></span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<p>查看 <code>EnableConfigurationProperties</code> 的源码，我们注意到它通过 <code>@Import</code> 导入了 <code>EnableConfigurationPropertiesImportSelector</code>。</p>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="meta">@Target(ElementType.TYPE)</span></span><br><span class="line"><span class="meta">@Retention(RetentionPolicy.RUNTIME)</span></span><br><span class="line"><span class="meta">@Documented</span></span><br><span class="line"><span class="meta">@Import(EnableConfigurationPropertiesImportSelector.class)</span></span><br><span class="line"><span class="keyword">public</span> <span class="meta">@interface</span> EnableConfigurationProperties &#123;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 使用 Spring 快速注册标注了 @ConfigurationProperties 的 bean。无论 value 如何，标准的 Spring Bean 也将被扫描。</span></span><br><span class="line">    Class&lt;?&gt;[] value() <span class="keyword">default</span> &#123;&#125;;</span><br><span class="line"></span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<h2 id="注解的作用"><a href="#注解的作用" class="headerlink" title="注解的作用"></a>注解的作用</h2><p>查看 <code>EnableConfigurationPropertiesImportSelector</code> 的源码，关注 <code>selectImports</code> 方法。该方法返回了 <code>ConfigurationPropertiesBeanRegistrar</code> 和 <code>ConfigurationPropertiesBindingPostProcessorRegistrar</code> 的全限定类名，<code>Spring</code> 将注册它们。</p>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">class</span> <span class="title class_">EnableConfigurationPropertiesImportSelector</span> <span class="keyword">implements</span> <span class="title class_">ImportSelector</span> &#123;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">static</span> <span class="keyword">final</span> String[] IMPORTS = &#123;</span><br><span class="line">            ConfigurationPropertiesBeanRegistrar.class.getName(),</span><br><span class="line">            ConfigurationPropertiesBindingPostProcessorRegistrar.class.getName() &#125;;</span><br><span class="line"></span><br><span class="line">    <span class="meta">@Override</span></span><br><span class="line">    <span class="keyword">public</span> String[] selectImports(AnnotationMetadata metadata) &#123;</span><br><span class="line">        <span class="keyword">return</span> IMPORTS;</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<h3 id="注册目标类"><a href="#注册目标类" class="headerlink" title="注册目标类"></a>注册目标类</h3><p><code>ConfigurationPropertiesBeanRegistrar</code> 是一个内部类，查看 <code>ConfigurationPropertiesBeanRegistrar</code> 的源码，关注 <code>registerBeanDefinitions</code> 方法。注册的目标来自于：</p>
+<ul>
+<li><code>@EnableConfigurationProperties</code> 的 <code>value</code> 所指定的类中</li>
+<li>且标注了 <code>@ConfigurationProperties</code> 的类</li>
+</ul>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">class</span> <span class="title class_">ConfigurationPropertiesBeanRegistrar</span></span><br><span class="line">        <span class="keyword">implements</span> <span class="title class_">ImportBeanDefinitionRegistrar</span> &#123;</span><br><span class="line"></span><br><span class="line">    <span class="meta">@Override</span></span><br><span class="line">    <span class="keyword">public</span> <span class="keyword">void</span> <span class="title function_">registerBeanDefinitions</span><span class="params">(AnnotationMetadata metadata,</span></span><br><span class="line"><span class="params">            BeanDefinitionRegistry registry)</span> &#123;</span><br><span class="line">        <span class="comment">// 1. 获取要注册的 Class</span></span><br><span class="line">        <span class="comment">// 2. 遍历获取的结果进行注册</span></span><br><span class="line">        getTypes(metadata).forEach((type) -&gt; register(registry,</span><br><span class="line">                (ConfigurableListableBeanFactory) registry, type));</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line"></span><br><span class="line">    <span class="keyword">private</span> List&lt;Class&lt;?&gt;&gt; getTypes(AnnotationMetadata metadata) &#123;</span><br><span class="line">        <span class="comment">// 获取所有 @EnableConfigurationProperties 的属性</span></span><br><span class="line">        MultiValueMap&lt;String, Object&gt; attributes = metadata</span><br><span class="line">                .getAllAnnotationAttributes(</span><br><span class="line">                        EnableConfigurationProperties.class.getName(), <span class="literal">false</span>);</span><br><span class="line">        <span class="comment">// 获取属性 value 的值，处理后返回</span></span><br><span class="line">        <span class="keyword">return</span> collectClasses(attributes == <span class="literal">null</span> ? Collections.emptyList()</span><br><span class="line">                : attributes.get(<span class="string">&quot;value&quot;</span>));</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 收集 Class</span></span><br><span class="line">    <span class="keyword">private</span> List&lt;Class&lt;?&gt;&gt; collectClasses(List&lt;?&gt; values) &#123;</span><br><span class="line">        <span class="keyword">return</span> values.stream().flatMap((value) -&gt; Arrays.stream((Object[]) value))</span><br><span class="line">                .map((o) -&gt; (Class&lt;?&gt;) o).filter((type) -&gt; <span class="keyword">void</span>.class != type)</span><br><span class="line">                .collect(Collectors.toList());</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 注册 Bean 定义</span></span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">void</span> <span class="title function_">register</span><span class="params">(BeanDefinitionRegistry registry,</span></span><br><span class="line"><span class="params">            ConfigurableListableBeanFactory beanFactory, Class&lt;?&gt; type)</span> &#123;</span><br><span class="line">        <span class="type">String</span> <span class="variable">name</span> <span class="operator">=</span> getName(type);</span><br><span class="line">        <span class="comment">// 检测是否包含 Bean 定义</span></span><br><span class="line">        <span class="keyword">if</span> (!containsBeanDefinition(beanFactory, name)) &#123;</span><br><span class="line">            <span class="comment">// 如果没找到，则注册</span></span><br><span class="line">            registerBeanDefinition(registry, name, type);</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// beanName = prefix + 全限定类名 or 全限定类名</span></span><br><span class="line">    <span class="keyword">private</span> String <span class="title function_">getName</span><span class="params">(Class&lt;?&gt; type)</span> &#123;</span><br><span class="line">        <span class="type">ConfigurationProperties</span> <span class="variable">annotation</span> <span class="operator">=</span> AnnotationUtils.findAnnotation(type,</span><br><span class="line">                ConfigurationProperties.class);</span><br><span class="line">        <span class="type">String</span> <span class="variable">prefix</span> <span class="operator">=</span> (annotation != <span class="literal">null</span> ? annotation.prefix() : <span class="string">&quot;&quot;</span>);</span><br><span class="line">        <span class="keyword">return</span> (StringUtils.hasText(prefix) ? prefix + <span class="string">&quot;-&quot;</span> + type.getName()</span><br><span class="line">                : type.getName());</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 检测是否包含 Bean 定义</span></span><br><span class="line">    <span class="keyword">private</span> <span class="type">boolean</span> <span class="title function_">containsBeanDefinition</span><span class="params">(</span></span><br><span class="line"><span class="params">            ConfigurableListableBeanFactory beanFactory, String name)</span> &#123;</span><br><span class="line">        <span class="comment">// 先检测当前工厂中是否包含</span></span><br><span class="line">        <span class="keyword">if</span> (beanFactory.containsBeanDefinition(name)) &#123;</span><br><span class="line">            <span class="keyword">return</span> <span class="literal">true</span>;</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="comment">// 如果没找到则检测父工厂是否包含</span></span><br><span class="line">        <span class="type">BeanFactory</span> <span class="variable">parent</span> <span class="operator">=</span> beanFactory.getParentBeanFactory();</span><br><span class="line">        <span class="keyword">if</span> (parent <span class="keyword">instanceof</span> ConfigurableListableBeanFactory) &#123;</span><br><span class="line">            <span class="keyword">return</span> containsBeanDefinition((ConfigurableListableBeanFactory) parent,</span><br><span class="line">                    name);</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="keyword">return</span> <span class="literal">false</span>;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 注册 Bean 定义</span></span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">void</span> <span class="title function_">registerBeanDefinition</span><span class="params">(BeanDefinitionRegistry registry, String name,</span></span><br><span class="line"><span class="params">            Class&lt;?&gt; type)</span> &#123;</span><br><span class="line">        <span class="comment">// 断言目标类标注了 @ConfigurationProperties</span></span><br><span class="line">        assertHasAnnotation(type);</span><br><span class="line">        <span class="type">GenericBeanDefinition</span> <span class="variable">definition</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">GenericBeanDefinition</span>();</span><br><span class="line">        definition.setBeanClass(type);</span><br><span class="line">        <span class="comment">// registry 注册 Bean 定义</span></span><br><span class="line">        registry.registerBeanDefinition(name, definition);</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 断言目标类标注了 @ConfigurationProperties</span></span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">void</span> <span class="title function_">assertHasAnnotation</span><span class="params">(Class&lt;?&gt; type)</span> &#123;</span><br><span class="line">        Assert.notNull(</span><br><span class="line">                AnnotationUtils.findAnnotation(type, ConfigurationProperties.class),</span><br><span class="line">                <span class="string">&quot;No &quot;</span> + ConfigurationProperties.class.getSimpleName()</span><br><span class="line">                        + <span class="string">&quot; annotation found on  &#x27;&quot;</span> + type.getName() + <span class="string">&quot;&#x27;.&quot;</span>);</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<h3 id="注册后处理器"><a href="#注册后处理器" class="headerlink" title="注册后处理器"></a>注册后处理器</h3><p>查看 <code>ConfigurationPropertiesBindingPostProcessorRegistrar</code> 的源码，关注 <code>registerBeanDefinitions</code> 方法。该方法注册了 <code>ConfigurationPropertiesBindingPostProcessor</code> 和 <code>ConfigurationBeanFactoryMetadata</code>。</p>
+<ul>
+<li>前者顾名思义，用于处理 <code>ConfigurationProperties</code> 的绑定</li>
+<li>后者是用于在 <code>Bean</code> 工厂初始化期间记住 <code>@Bean</code> 定义元数据的实用程序类</li>
+</ul>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">class</span> <span class="title class_">ConfigurationPropertiesBindingPostProcessorRegistrar</span></span><br><span class="line">        <span class="keyword">implements</span> <span class="title class_">ImportBeanDefinitionRegistrar</span> &#123;</span><br><span class="line"></span><br><span class="line">    <span class="meta">@Override</span></span><br><span class="line">    <span class="keyword">public</span> <span class="keyword">void</span> <span class="title function_">registerBeanDefinitions</span><span class="params">(AnnotationMetadata importingClassMetadata,</span></span><br><span class="line"><span class="params">            BeanDefinitionRegistry registry)</span> &#123;</span><br><span class="line">        <span class="keyword">if</span> (!registry.containsBeanDefinition(</span><br><span class="line">                ConfigurationPropertiesBindingPostProcessor.BEAN_NAME)) &#123;</span><br><span class="line">            registerConfigurationPropertiesBindingPostProcessor(registry);</span><br><span class="line">            registerConfigurationBeanFactoryMetadata(registry);</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">void</span> <span class="title function_">registerConfigurationPropertiesBindingPostProcessor</span><span class="params">(</span></span><br><span class="line"><span class="params">            BeanDefinitionRegistry registry)</span> &#123;</span><br><span class="line">        <span class="type">GenericBeanDefinition</span> <span class="variable">definition</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">GenericBeanDefinition</span>();</span><br><span class="line">        definition.setBeanClass(ConfigurationPropertiesBindingPostProcessor.class);</span><br><span class="line">        <span class="comment">// Bean 定义的角色为基础设施</span></span><br><span class="line">        definition.setRole(BeanDefinition.ROLE_INFRASTRUCTURE);</span><br><span class="line">        registry.registerBeanDefinition(</span><br><span class="line">                ConfigurationPropertiesBindingPostProcessor.BEAN_NAME, definition);</span><br><span class="line"></span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">void</span> <span class="title function_">registerConfigurationBeanFactoryMetadata</span><span class="params">(</span></span><br><span class="line"><span class="params">            BeanDefinitionRegistry registry)</span> &#123;</span><br><span class="line">        <span class="type">GenericBeanDefinition</span> <span class="variable">definition</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">GenericBeanDefinition</span>();</span><br><span class="line">        definition.setBeanClass(ConfigurationBeanFactoryMetadata.class);</span><br><span class="line">        definition.setRole(BeanDefinition.ROLE_INFRASTRUCTURE);</span><br><span class="line">        registry.registerBeanDefinition(ConfigurationBeanFactoryMetadata.BEAN_NAME,</span><br><span class="line">                definition);</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<h2 id="绑定"><a href="#绑定" class="headerlink" title="绑定"></a>绑定</h2><p><code>ConfigurationPropertiesBindingPostProcessor</code> 是用于 <code>ConfigurationProperties</code> 绑定的后处理器，关注 <code>afterPropertiesSet</code> 方法还有核心方法 <code>postProcessBeforeInitialization</code>。</p>
+<ul>
+<li>在 <code>afterPropertiesSet</code> 方法中，它获取到了和自己一起注册的 <code>ConfigurationBeanFactoryMetadata</code>。</li>
+<li>在 <code>postProcessBeforeInitialization</code> 方法中，先获取 <code>@ConfigurationProperties</code>，再进行绑定。</li>
+</ul>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">class</span> <span class="title class_">ConfigurationPropertiesBindingPostProcessor</span> <span class="keyword">implements</span> <span class="title class_">BeanPostProcessor</span>,</span><br><span class="line">        PriorityOrdered, ApplicationContextAware, InitializingBean &#123;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">final</span> <span class="type">String</span> <span class="variable">BEAN_NAME</span> <span class="operator">=</span> ConfigurationPropertiesBindingPostProcessor.class</span><br><span class="line">            .getName();</span><br><span class="line"></span><br><span class="line">    <span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">final</span> <span class="type">String</span> <span class="variable">VALIDATOR_BEAN_NAME</span> <span class="operator">=</span> <span class="string">&quot;configurationPropertiesValidator&quot;</span>;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">private</span> ConfigurationBeanFactoryMetadata beanFactoryMetadata;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">private</span> ApplicationContext applicationContext;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">private</span> ConfigurationPropertiesBinder configurationPropertiesBinder;</span><br><span class="line"></span><br><span class="line">    <span class="meta">@Override</span></span><br><span class="line">    <span class="keyword">public</span> <span class="keyword">void</span> <span class="title function_">setApplicationContext</span><span class="params">(ApplicationContext applicationContext)</span></span><br><span class="line">            <span class="keyword">throws</span> BeansException &#123;</span><br><span class="line">        <span class="built_in">this</span>.applicationContext = applicationContext;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="meta">@Override</span></span><br><span class="line">    <span class="keyword">public</span> <span class="keyword">void</span> <span class="title function_">afterPropertiesSet</span><span class="params">()</span> <span class="keyword">throws</span> Exception &#123;</span><br><span class="line">        <span class="comment">// We can&#x27;t use constructor injection of the application context because</span></span><br><span class="line">        <span class="comment">// it causes eager factory bean initialization</span></span><br><span class="line">        <span class="comment">// 注入了 ConfigurationBeanFactoryMetadata（不理解注解描述的情况？）</span></span><br><span class="line">        <span class="built_in">this</span>.beanFactoryMetadata = <span class="built_in">this</span>.applicationContext.getBean(</span><br><span class="line">                ConfigurationBeanFactoryMetadata.BEAN_NAME,</span><br><span class="line">                ConfigurationBeanFactoryMetadata.class);</span><br><span class="line">        <span class="built_in">this</span>.configurationPropertiesBinder = <span class="keyword">new</span> <span class="title class_">ConfigurationPropertiesBinder</span>(</span><br><span class="line">                <span class="built_in">this</span>.applicationContext, VALIDATOR_BEAN_NAME);</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="meta">@Override</span></span><br><span class="line">    <span class="keyword">public</span> <span class="type">int</span> <span class="title function_">getOrder</span><span class="params">()</span> &#123;</span><br><span class="line">        <span class="keyword">return</span> Ordered.HIGHEST_PRECEDENCE + <span class="number">1</span>;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="meta">@Override</span></span><br><span class="line">    <span class="keyword">public</span> Object <span class="title function_">postProcessBeforeInitialization</span><span class="params">(Object bean, String beanName)</span></span><br><span class="line">            <span class="keyword">throws</span> BeansException &#123;</span><br><span class="line">        <span class="comment">// 获取 @ConfigurationProperties</span></span><br><span class="line">        <span class="type">ConfigurationProperties</span> <span class="variable">annotation</span> <span class="operator">=</span> getAnnotation(bean, beanName,</span><br><span class="line">                ConfigurationProperties.class);</span><br><span class="line">        <span class="keyword">if</span> (annotation != <span class="literal">null</span>) &#123;</span><br><span class="line">            <span class="comment">// 绑定</span></span><br><span class="line">            bind(bean, beanName, annotation);</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="keyword">return</span> bean;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">void</span> <span class="title function_">bind</span><span class="params">(Object bean, String beanName, ConfigurationProperties annotation)</span> &#123;</span><br><span class="line">        <span class="comment">// 获取 Bean 的类型</span></span><br><span class="line">        <span class="type">ResolvableType</span> <span class="variable">type</span> <span class="operator">=</span> getBeanType(bean, beanName);</span><br><span class="line">        <span class="comment">// 获取 @Validated 用于校验</span></span><br><span class="line">        <span class="type">Validated</span> <span class="variable">validated</span> <span class="operator">=</span> getAnnotation(bean, beanName, Validated.class);</span><br><span class="line">        Annotation[] annotations = (validated == <span class="literal">null</span> ? <span class="keyword">new</span> <span class="title class_">Annotation</span>[] &#123; annotation &#125;</span><br><span class="line">                : <span class="keyword">new</span> <span class="title class_">Annotation</span>[] &#123; annotation, validated &#125;);</span><br><span class="line">        <span class="comment">// 创建 Bindable 对象</span></span><br><span class="line">        Bindable&lt;?&gt; target = Bindable.of(type).withExistingValue(bean)</span><br><span class="line">                .withAnnotations(annotations);</span><br><span class="line">        <span class="keyword">try</span> &#123;</span><br><span class="line">            <span class="comment">// 绑定</span></span><br><span class="line">            <span class="built_in">this</span>.configurationPropertiesBinder.bind(target);</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="keyword">catch</span> (Exception ex) &#123;</span><br><span class="line">            <span class="keyword">throw</span> <span class="keyword">new</span> <span class="title class_">ConfigurationPropertiesBindException</span>(beanName, bean, annotation,</span><br><span class="line">                    ex);</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">private</span> ResolvableType <span class="title function_">getBeanType</span><span class="params">(Object bean, String beanName)</span> &#123;</span><br><span class="line">        <span class="comment">// 先查找工厂方法</span></span><br><span class="line">        <span class="type">Method</span> <span class="variable">factoryMethod</span> <span class="operator">=</span> <span class="built_in">this</span>.beanFactoryMetadata.findFactoryMethod(beanName);</span><br><span class="line">        <span class="keyword">if</span> (factoryMethod != <span class="literal">null</span>) &#123;</span><br><span class="line">            <span class="comment">// 如果存在，返回工厂方法的返回值类型</span></span><br><span class="line">            <span class="keyword">return</span> ResolvableType.forMethodReturnType(factoryMethod);</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="comment">// 否则返回 bean 的类型（难道 bean 的类型不是工厂方法的返回值类型吗？）</span></span><br><span class="line">        <span class="keyword">return</span> ResolvableType.forClass(bean.getClass());</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">private</span> &lt;A <span class="keyword">extends</span> <span class="title class_">Annotation</span>&gt; A <span class="title function_">getAnnotation</span><span class="params">(Object bean, String beanName,</span></span><br><span class="line"><span class="params">            Class&lt;A&gt; type)</span> &#123;</span><br><span class="line">        <span class="comment">// 先到 @Bean 方法中获取</span></span><br><span class="line">        <span class="type">A</span> <span class="variable">annotation</span> <span class="operator">=</span> <span class="built_in">this</span>.beanFactoryMetadata.findFactoryAnnotation(beanName, type);</span><br><span class="line">        <span class="keyword">if</span> (annotation == <span class="literal">null</span>) &#123;</span><br><span class="line">            <span class="comment">// 如果没有，再到类上获取</span></span><br><span class="line">            annotation = AnnotationUtils.findAnnotation(bean.getClass(), type);</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="keyword">return</span> annotation;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<p><code>ConfigurationBeanFactoryMetadata</code> 是用于在 <code>Bean</code> 工厂初始化期间记住 <code>@Bean</code> 定义元数据的实用程序类。在前面我们介绍过 <code>@ConfigurationProperties</code> 不仅可以添加到类定义，还可以用于标注 <code>@Bean</code> 方法，<code>ConfigurationBeanFactoryMetadata</code> 正是应用于在后者这类情况下获取 <code>@ConfigurationProperties</code>。</p>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">class</span> <span class="title class_">ConfigurationBeanFactoryMetadata</span> <span class="keyword">implements</span> <span class="title class_">BeanFactoryPostProcessor</span> &#123;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">final</span> Map&lt;String, FactoryMetadata&gt; beansFactoryMetadata = <span class="keyword">new</span> <span class="title class_">HashMap</span>&lt;&gt;();</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 后处理 BeanFactory</span></span><br><span class="line">    <span class="meta">@Override</span></span><br><span class="line">    <span class="keyword">public</span> <span class="keyword">void</span> <span class="title function_">postProcessBeanFactory</span><span class="params">(ConfigurableListableBeanFactory beanFactory)</span></span><br><span class="line">            <span class="keyword">throws</span> BeansException &#123;</span><br><span class="line">        <span class="built_in">this</span>.beanFactory = beanFactory;</span><br><span class="line">        <span class="comment">// 遍历 Bean 定义</span></span><br><span class="line">        <span class="keyword">for</span> (String name : beanFactory.getBeanDefinitionNames()) &#123;</span><br><span class="line">            <span class="type">BeanDefinition</span> <span class="variable">definition</span> <span class="operator">=</span> beanFactory.getBeanDefinition(name);</span><br><span class="line">            <span class="type">String</span> <span class="variable">method</span> <span class="operator">=</span> definition.getFactoryMethodName();</span><br><span class="line">            <span class="type">String</span> <span class="variable">bean</span> <span class="operator">=</span> definition.getFactoryBeanName();、</span><br><span class="line">            <span class="comment">// 检测是否是一个 @Bean 方法对应的 Bean 定义</span></span><br><span class="line">            <span class="keyword">if</span> (method != <span class="literal">null</span> &amp;&amp; bean != <span class="literal">null</span>) &#123;</span><br><span class="line">                <span class="built_in">this</span>.beansFactoryMetadata.put(name, <span class="keyword">new</span> <span class="title class_">FactoryMetadata</span>(bean, method));</span><br><span class="line">            &#125;</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 获取工厂方法上的注解</span></span><br><span class="line">    <span class="keyword">public</span> &lt;A <span class="keyword">extends</span> <span class="title class_">Annotation</span>&gt; A <span class="title function_">findFactoryAnnotation</span><span class="params">(String beanName,</span></span><br><span class="line"><span class="params">			Class&lt;A&gt; type)</span> &#123;</span><br><span class="line">		<span class="type">Method</span> <span class="variable">method</span> <span class="operator">=</span> findFactoryMethod(beanName);</span><br><span class="line">		<span class="keyword">return</span> (method == <span class="literal">null</span> ? <span class="literal">null</span> : AnnotationUtils.findAnnotation(method, type));</span><br><span class="line">	&#125;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 获取工厂方法</span></span><br><span class="line">	<span class="keyword">public</span> Method <span class="title function_">findFactoryMethod</span><span class="params">(String beanName)</span> &#123;</span><br><span class="line">		<span class="keyword">if</span> (!<span class="built_in">this</span>.beansFactoryMetadata.containsKey(beanName)) &#123;</span><br><span class="line">			<span class="keyword">return</span> <span class="literal">null</span>;</span><br><span class="line">		&#125;</span><br><span class="line">		AtomicReference&lt;Method&gt; found = <span class="keyword">new</span> <span class="title class_">AtomicReference</span>&lt;&gt;(<span class="literal">null</span>);</span><br><span class="line">		<span class="type">FactoryMetadata</span> <span class="variable">metadata</span> <span class="operator">=</span> <span class="built_in">this</span>.beansFactoryMetadata.get(beanName);</span><br><span class="line">		Class&lt;?&gt; factoryType = <span class="built_in">this</span>.beanFactory.getType(metadata.getBean());</span><br><span class="line">		<span class="type">String</span> <span class="variable">factoryMethod</span> <span class="operator">=</span> metadata.getMethod();</span><br><span class="line">        <span class="comment">// 如果是代理类，获取其父类</span></span><br><span class="line">		<span class="keyword">if</span> (ClassUtils.isCglibProxyClass(factoryType)) &#123;</span><br><span class="line">			factoryType = factoryType.getSuperclass();</span><br><span class="line">		&#125;</span><br><span class="line">        <span class="comment">// 遍历声明的方法进行匹配（名字相同即可没问题吗？）</span></span><br><span class="line">		ReflectionUtils.doWithMethods(factoryType, (method) -&gt; &#123;</span><br><span class="line">			<span class="keyword">if</span> (method.getName().equals(factoryMethod)) &#123;</span><br><span class="line">				found.compareAndSet(<span class="literal">null</span>, method);</span><br><span class="line">			&#125;</span><br><span class="line">		&#125;);</span><br><span class="line">		<span class="keyword">return</span> found.get();</span><br><span class="line">	&#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<h2 id="总结"><a href="#总结" class="headerlink" title="总结"></a>总结</h2><p><code>@EnableConfigurationProperties</code> 的目的有两个：</p>
+<ul>
+<li>注册目标</li>
+<li>注册后处理器用于在目标进行 <code>Bean</code> 初始化工作时，介入进行绑定</li>
+</ul>
+<p>尽管注册目标时的操作有些巧妙，但是还是要明白 <code>ConfigurationProperties</code> 类只是单纯的被注册了而已。对于后处理器而言，无论一个 <code>ConfigurationProperties</code> 类是不是通过注解注册，后处理器都会一视同仁地进行绑定。但同时，你又要知道后处理器也是通过 <code>@EnableConfigurationProperties</code> 注册的，因此你需要保证至少有一个 <code>@EnableConfigurationProperties</code> 标注的类被注册（并被处理了 <code>@Import</code>）。<br>在 <code>Spring Boot</code> 中，<code>@SpringBootApplication</code> 通过 <code>@EnableAutoConfiguration</code> 启用了自动配置，从而注册了 <code>ConfigurationPropertiesAutoConfiguration</code>，<code>ConfigurationPropertiesAutoConfiguration</code> 标注了 <code>@EnableConfigurationProperties</code>。因此，对于 <code>Spring Boot</code> 而言，扫描范围内的所有 <code>ConfigurationProperties</code> 类，其实都不需要 <code>@EnableAutoConfiguration</code>。事实上，由于默认生成的 <code>beanName</code> 不同，多余的配置还会重复注册两个 <code>Bean</code> 定义。</p>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="meta">@Configuration</span></span><br><span class="line"><span class="meta">@EnableConfigurationProperties</span></span><br><span class="line"><span class="keyword">public</span> <span class="keyword">class</span> <span class="title class_">ConfigurationPropertiesAutoConfiguration</span> &#123;</span><br><span class="line"></span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+]]></content>
+      <tags>
+        <tag>java</tag>
+        <tag>spring</tag>
+        <tag>spring boot</tag>
+      </tags>
+  </entry>
+  <entry>
+    <title>Dubbo SPI 的工作原理</title>
+    <url>/2023/11/28/how-does-Dubbo-SPI-works/</url>
+    <content><![CDATA[<p><code>SPI</code> 作为一种服务发现机制，允许程序在运行时动态地加载具体实现类。因其强大的可拓展性，<code>SPI</code> 被广泛应用于各类技术框架中，例如 <code>JDBC</code> 驱动、<code>Spring</code> 和 <code>Dubbo</code> 等等。<code>Dubbo</code> 并未使用原生的 <code>Java SPI</code>，而是重新实现了一套更加强大的 <strong><code>Dubbo SPI</code><strong>。本文将简单介绍 <code>SPI</code> 的设计理念，通过示例带你体会 <code>SPI</code> 的作用，通过 <strong><code>Dubbo</code> 获取拓展的流程图</strong>和</strong>源码分析</strong>带你理解 <code>Dubbo SPI</code> 的工作原理。深入了解 <code>Dubbo SPI</code>，你将能更好地利用这一机制为你的程序提供灵活的拓展功能。</p>
+<span id="more"></span>
+
+<h2 id="SPI-简介"><a href="#SPI-简介" class="headerlink" title="SPI 简介"></a>SPI 简介</h2><p><code>SPI</code> 的全称是 <code>Service Provider Interface</code>，是一种服务发现机制。一般情况下，一项服务的接口和具体实现，都是服务提供者编写的。在 <code>SPI</code> 机制中，一项服务的接口是服务使用者编写的，不同的服务提供者编写不同的具体实现。在程序运行时，服务加载器动态地为接口加载具体实现类。因为 <code>SPI</code> 具备“动态加载”的特性，我们很容易通过它为程序提供拓展功能。以 <code>Java</code> 的 <code>JDBC</code> 驱动为例，JDK 提供了 <code>java.sql.Driver</code> 接口，各个数据库厂商，例如 <code>MySQL</code>、<code>Oracle</code> 提供具体的实现。</p>
+<img src="/2023/11/28/how-does-Dubbo-SPI-works/Pasted%20image%2020231129010505.png" class="" title="SPI 机制">
+
+<p>目前 <strong>SPI 的实现方式</strong>大多是将接口实现类的全限定名配置在文件中，并由服务加载器读取配置文件，加载实现类：</p>
+<ul>
+<li>Java SPI：<code>META-INF/services/full.qualified.interface.name</code></li>
+<li>Dubbo SPI：<code>META-INF/dubbo/full.qualified.interface.name</code>（还有其他目录可供选择）</li>
+<li>Spring SPI: <code>META-INF/spring.factories</code></li>
+</ul>
+<h2 id="SPI-示例"><a href="#SPI-示例" class="headerlink" title="SPI 示例"></a>SPI 示例</h2><h3 id="Java-SPI-示例"><a href="#Java-SPI-示例" class="headerlink" title="Java SPI 示例"></a>Java SPI 示例</h3><p>定义一个接口 <code>Animal</code>。</p>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">interface</span> <span class="title class_">Animal</span> &#123;</span><br><span class="line">    <span class="keyword">void</span> <span class="title function_">bark</span><span class="params">()</span>;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<p>定义两个实现类 <code>Dog</code> 和 <code>Cat</code>。</p>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">class</span> <span class="title class_">Dog</span> <span class="keyword">implements</span> <span class="title class_">Animal</span> &#123;</span><br><span class="line">    <span class="meta">@Override</span></span><br><span class="line">    <span class="keyword">public</span> <span class="keyword">void</span> <span class="title function_">bark</span><span class="params">()</span> &#123;</span><br><span class="line">        System.out.println(<span class="string">&quot;Dog bark...&quot;</span>);</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br><span class="line"></span><br><span class="line"><span class="keyword">public</span> <span class="keyword">class</span> <span class="title class_">Cat</span> <span class="keyword">implements</span> <span class="title class_">Animal</span> &#123;</span><br><span class="line">    <span class="meta">@Override</span></span><br><span class="line">    <span class="keyword">public</span> <span class="keyword">void</span> <span class="title function_">bark</span><span class="params">()</span> &#123;</span><br><span class="line">        System.out.println(<span class="string">&quot;Cat bark...&quot;</span>);</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<p>在 <strong><code>META-INF/services</code></strong> 文件夹下创建一个文件，名称为 <code>Animal</code> 的全限定名 <code>com.moralok.dubbo.spi.test.Animal</code>，文件内容为实现类的全限定名，实现类的全限定名之间用换行符分隔。</p>
+<figure class="highlight plaintext"><table><tr><td class="code"><pre><span class="line">com.moralok.dubbo.spi.test.Dog</span><br><span class="line">com.moralok.dubbo.spi.test.Cat</span><br></pre></td></tr></table></figure>
+
+<p>进行测试。</p>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">class</span> <span class="title class_">JavaSPITest</span> &#123;</span><br><span class="line">    <span class="meta">@Test</span></span><br><span class="line">    <span class="keyword">void</span> <span class="title function_">bark</span><span class="params">()</span> &#123;</span><br><span class="line">        System.out.println(<span class="string">&quot;Java SPI&quot;</span>);</span><br><span class="line">        System.out.println(<span class="string">&quot;============&quot;</span>);</span><br><span class="line">        ServiceLoader&lt;Animal&gt; serviceLoader = ServiceLoader.load(Animal.class);</span><br><span class="line">        serviceLoader.forEach(Animal::bark);</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<p>测试结果</p>
+<figure class="highlight console"><table><tr><td class="code"><pre><span class="line">Java SPI</span><br><span class="line">============</span><br><span class="line">Dog bark...</span><br><span class="line">Cat bark...</span><br></pre></td></tr></table></figure>
+
+<h3 id="Dubbo-SPI-示例"><a href="#Dubbo-SPI-示例" class="headerlink" title="Dubbo SPI 示例"></a>Dubbo SPI 示例</h3><p><code>Dubbo</code> 并未使用原生的 <code>Java SPI</code>，而是重新实现了一套功能更加强大的 <code>SPI</code> 机制。<code>Dubbo SPI</code> 的配置文件放在 <strong><code>META-INF/dubbo</code></strong> 文件夹下，名称仍然是接口的全限定名，但是内容是“名称-&gt;实现类的全限定名”的键值对，另外接口需要标注 <code>SPI</code> 注解。</p>
+<figure class="highlight plaintext"><table><tr><td class="code"><pre><span class="line">dog = com.moralok.dubbo.spi.test.Dog</span><br><span class="line">cat = com.moralok.dubbo.spi.test.Cat</span><br></pre></td></tr></table></figure>
+
+<p>进行测试。</p>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">class</span> <span class="title class_">DubboSPITest</span> &#123;</span><br><span class="line"></span><br><span class="line">    <span class="meta">@Test</span></span><br><span class="line">    <span class="keyword">void</span> <span class="title function_">bark</span><span class="params">()</span> &#123;</span><br><span class="line">        System.out.println(<span class="string">&quot;Dubbo SPI&quot;</span>);</span><br><span class="line">        System.out.println(<span class="string">&quot;============&quot;</span>);</span><br><span class="line">        ExtensionLoader&lt;Animal&gt; extensionLoader = ExtensionLoader.getExtensionLoader(Animal.class);</span><br><span class="line">        <span class="type">Animal</span> <span class="variable">dog</span> <span class="operator">=</span> extensionLoader.getExtension(<span class="string">&quot;dog&quot;</span>);</span><br><span class="line">        dog.bark();</span><br><span class="line">        <span class="type">Animal</span> <span class="variable">cat</span> <span class="operator">=</span> extensionLoader.getExtension(<span class="string">&quot;cat&quot;</span>);</span><br><span class="line">        cat.bark();</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<p>测试结果</p>
+<figure class="highlight console"><table><tr><td class="code"><pre><span class="line">Dubbo SPI</span><br><span class="line">============</span><br><span class="line">Dog bark...</span><br><span class="line">Cat bark...</span><br></pre></td></tr></table></figure>
+
+<h2 id="Dubbo-获取扩展流程图"><a href="#Dubbo-获取扩展流程图" class="headerlink" title="Dubbo 获取扩展流程图"></a>Dubbo 获取扩展流程图</h2><img src="/2023/11/28/how-does-Dubbo-SPI-works/Pasted%20image%2020231129204920.png" class="" title="Dubbo 获取扩展流程图">
+
+<h2 id="Dubbo-SPI-源码分析"><a href="#Dubbo-SPI-源码分析" class="headerlink" title="Dubbo SPI 源码分析"></a>Dubbo SPI 源码分析</h2><h3 id="获取-ExtensionLoader"><a href="#获取-ExtensionLoader" class="headerlink" title="获取 ExtensionLoader"></a>获取 ExtensionLoader</h3><figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">private</span> <span class="keyword">static</span> <span class="keyword">final</span> ConcurrentMap&lt;Class&lt;?&gt;, ExtensionLoader&lt;?&gt;&gt; EXTENSION_LOADERS = <span class="keyword">new</span> <span class="title class_">ConcurrentHashMap</span>&lt;&gt;(<span class="number">64</span>);</span><br><span class="line"></span><br><span class="line"><span class="keyword">public</span> <span class="keyword">static</span> &lt;T&gt; ExtensionLoader&lt;T&gt; <span class="title function_">getExtensionLoader</span><span class="params">(Class&lt;T&gt; type)</span> &#123;</span><br><span class="line">    <span class="keyword">if</span> (type == <span class="literal">null</span>) &#123;</span><br><span class="line">        <span class="keyword">throw</span> <span class="keyword">new</span> <span class="title class_">IllegalArgumentException</span>(<span class="string">&quot;Extension type == null&quot;</span>);</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="keyword">if</span> (!type.isInterface()) &#123;</span><br><span class="line">        <span class="keyword">throw</span> <span class="keyword">new</span> <span class="title class_">IllegalArgumentException</span>(<span class="string">&quot;Extension type (&quot;</span> + type + <span class="string">&quot;) is not an interface!&quot;</span>);</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="keyword">if</span> (!withExtensionAnnotation(type)) &#123;</span><br><span class="line">        <span class="keyword">throw</span> <span class="keyword">new</span> <span class="title class_">IllegalArgumentException</span>(<span class="string">&quot;Extension type (&quot;</span> + type +</span><br><span class="line">                <span class="string">&quot;) is not an extension, because it is NOT annotated with @&quot;</span> + SPI.class.getSimpleName() + <span class="string">&quot;!&quot;</span>);</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 从缓存中获取，如果缓存未命中，则创建，保存到缓存并返回</span></span><br><span class="line">    ExtensionLoader&lt;T&gt; loader = (ExtensionLoader&lt;T&gt;) EXTENSION_LOADERS.get(type);</span><br><span class="line">    <span class="keyword">if</span> (loader == <span class="literal">null</span>) &#123;</span><br><span class="line">        EXTENSION_LOADERS.putIfAbsent(type, <span class="keyword">new</span> <span class="title class_">ExtensionLoader</span>&lt;T&gt;(type));</span><br><span class="line">        loader = (ExtensionLoader&lt;T&gt;) EXTENSION_LOADERS.get(type);</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="keyword">return</span> loader;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<p>这个方法包含了如下步骤：</p>
+<ol>
+<li>参数校验。</li>
+<li>从缓存 <code>EXTENSION_LOADERS</code> 中获取与拓展类对应的 <code>ExtensionLoader</code>，如果缓存未命中，则创建一个新的实例，保存到缓存并返回。</li>
+</ol>
+<blockquote>
+<p>“<strong>从缓存中获取，如果缓存未命中，则创建，保存到缓存并返回</strong>”，类似的 <code>getOrCreate</code> 的处理模式在 <code>Dubbo</code> 的源码中经常出现。</p>
+</blockquote>
+<p><code>EXTENSION_LOADERS</code> 是 <code>ExtensionLoader</code> 的静态变量，保存了“拓展类-&gt;<code>ExtensionLoader</code>”的映射关系。</p>
+<h3 id="根据-name-获取-Extension"><a href="#根据-name-获取-Extension" class="headerlink" title="根据 name 获取 Extension"></a>根据 name 获取 Extension</h3><figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> T <span class="title function_">getExtension</span><span class="params">(String name)</span> &#123;</span><br><span class="line">    <span class="keyword">return</span> getExtension(name, <span class="literal">true</span>);</span><br><span class="line">&#125;</span><br><span class="line"></span><br><span class="line"><span class="keyword">public</span> T <span class="title function_">getExtension</span><span class="params">(String name, <span class="type">boolean</span> wrap)</span> &#123;</span><br><span class="line">    <span class="keyword">if</span> (StringUtils.isEmpty(name)) &#123;</span><br><span class="line">        <span class="keyword">throw</span> <span class="keyword">new</span> <span class="title class_">IllegalArgumentException</span>(<span class="string">&quot;Extension name == null&quot;</span>);</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="keyword">if</span> (<span class="string">&quot;true&quot;</span>.equals(name)) &#123;</span><br><span class="line">        <span class="comment">// 获取默认的拓展实现</span></span><br><span class="line">        <span class="keyword">return</span> getDefaultExtension();</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="comment">// Holder，用于持有目标对象</span></span><br><span class="line">    <span class="keyword">final</span> Holder&lt;Object&gt; holder = getOrCreateHolder(name);</span><br><span class="line">    <span class="comment">// 双重检查</span></span><br><span class="line">    <span class="type">Object</span> <span class="variable">instance</span> <span class="operator">=</span> holder.get();</span><br><span class="line">    <span class="keyword">if</span> (instance == <span class="literal">null</span>) &#123;</span><br><span class="line">        <span class="keyword">synchronized</span> (holder) &#123;</span><br><span class="line">            instance = holder.get();</span><br><span class="line">            <span class="keyword">if</span> (instance == <span class="literal">null</span>) &#123;</span><br><span class="line">                <span class="comment">// 创建拓展实例，设置到 holder 中。</span></span><br><span class="line">                instance = createExtension(name, wrap);</span><br><span class="line">                holder.set(instance);</span><br><span class="line">            &#125;</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="keyword">return</span> (T) instance;</span><br><span class="line">&#125;</span><br><span class="line"></span><br><span class="line"><span class="keyword">private</span> <span class="keyword">final</span> ConcurrentMap&lt;String, Holder&lt;Object&gt;&gt; cachedInstances = <span class="keyword">new</span> <span class="title class_">ConcurrentHashMap</span>&lt;&gt;();</span><br><span class="line"></span><br><span class="line"><span class="keyword">private</span> Holder&lt;Object&gt; <span class="title function_">getOrCreateHolder</span><span class="params">(String name)</span> &#123;</span><br><span class="line">    Holder&lt;Object&gt; holder = cachedInstances.get(name);</span><br><span class="line">    <span class="keyword">if</span> (holder == <span class="literal">null</span>) &#123;</span><br><span class="line">        cachedInstances.putIfAbsent(name, <span class="keyword">new</span> <span class="title class_">Holder</span>&lt;&gt;());</span><br><span class="line">        holder = cachedInstances.get(name);</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="keyword">return</span> holder;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<p>这个方法中获取 <code>Holder</code> 和获取拓展实例都是使用 <code>getOrCreate</code> 的模式。</p>
+<p><code>Holder</code> 用于持有拓展实例。<code>cachedInstances</code> 是 <code>ExtensionLoader</code> 的成员变量，保存了“<code>name-&gt;Holder</code>(拓展实例)”的映射关系。</p>
+<h3 id="创建-Extension"><a href="#创建-Extension" class="headerlink" title="创建 Extension"></a>创建 Extension</h3><figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">private</span> T <span class="title function_">createExtension</span><span class="params">(String name, <span class="type">boolean</span> wrap)</span> &#123;</span><br><span class="line">    <span class="comment">// 从配置文件中加载所有的拓展类，可得到“name-&gt;拓展实现类”的映射关系表</span></span><br><span class="line">    Class&lt;?&gt; clazz = getExtensionClasses().get(name);</span><br><span class="line">    <span class="keyword">if</span> (clazz == <span class="literal">null</span> || unacceptableExceptions.contains(name)) &#123;</span><br><span class="line">        <span class="keyword">throw</span> findException(name);</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="keyword">try</span> &#123;</span><br><span class="line">        <span class="comment">// 使用 getOrCreate 模式获取拓展实例</span></span><br><span class="line">        <span class="type">T</span> <span class="variable">instance</span> <span class="operator">=</span> (T) EXTENSION_INSTANCES.get(clazz);</span><br><span class="line">        <span class="keyword">if</span> (instance == <span class="literal">null</span>) &#123;</span><br><span class="line">            EXTENSION_INSTANCES.putIfAbsent(clazz, clazz.getDeclaredConstructor().newInstance());</span><br><span class="line">            instance = (T) EXTENSION_INSTANCES.get(clazz);</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="comment">// 向拓展实例中注入依赖</span></span><br><span class="line">        injectExtension(instance);</span><br><span class="line"></span><br><span class="line">        <span class="comment">// 是否包装默认为 true</span></span><br><span class="line">        <span class="keyword">if</span> (wrap) &#123;</span><br><span class="line"></span><br><span class="line">            List&lt;Class&lt;?&gt;&gt; wrapperClassesList = <span class="keyword">new</span> <span class="title class_">ArrayList</span>&lt;&gt;();</span><br><span class="line">            <span class="keyword">if</span> (cachedWrapperClasses != <span class="literal">null</span>) &#123;</span><br><span class="line">                wrapperClassesList.addAll(cachedWrapperClasses);</span><br><span class="line">                wrapperClassesList.sort(WrapperComparator.COMPARATOR);</span><br><span class="line">                Collections.reverse(wrapperClassesList);</span><br><span class="line">            &#125;</span><br><span class="line"></span><br><span class="line">            <span class="keyword">if</span> (CollectionUtils.isNotEmpty(wrapperClassesList)) &#123;</span><br><span class="line">                <span class="comment">// 遍历包装类</span></span><br><span class="line">                <span class="keyword">for</span> (Class&lt;?&gt; wrapperClass : wrapperClassesList) &#123;</span><br><span class="line">                    <span class="type">Wrapper</span> <span class="variable">wrapper</span> <span class="operator">=</span> wrapperClass.getAnnotation(Wrapper.class);</span><br><span class="line">                    <span class="comment">// 区别于旧版本：支持使用 Wrapper 注解进行匹配</span></span><br><span class="line">                    <span class="keyword">if</span> (wrapper == <span class="literal">null</span></span><br><span class="line">                            || (ArrayUtils.contains(wrapper.matches(), name) &amp;&amp; !ArrayUtils.contains(wrapper.mismatches(), name))) &#123;</span><br><span class="line">                        <span class="comment">// 如果有匹配的包装类，包装拓展实例</span></span><br><span class="line">                        instance = injectExtension((T) wrapperClass.getConstructor(type).newInstance(instance));</span><br><span class="line">                    &#125;</span><br><span class="line">                &#125;</span><br><span class="line">            &#125;</span><br><span class="line">        &#125;</span><br><span class="line"></span><br><span class="line">        <span class="comment">// 初始化拓展实例</span></span><br><span class="line">        initExtension(instance);</span><br><span class="line">        <span class="keyword">return</span> instance;</span><br><span class="line">    &#125; <span class="keyword">catch</span> (Throwable t) &#123;</span><br><span class="line">        <span class="keyword">throw</span> <span class="keyword">new</span> <span class="title class_">IllegalStateException</span>(<span class="string">&quot;Extension instance (name: &quot;</span> + name + <span class="string">&quot;, class: &quot;</span> +</span><br><span class="line">                type + <span class="string">&quot;) couldn&#x27;t be instantiated: &quot;</span> + t.getMessage(), t);</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<p>这个方法包含如下步骤：</p>
+<ol>
+<li>通过 <code>getExtensionClasses</code> 获取所有拓展类</li>
+<li>通过反射创建拓展实例</li>
+<li>向拓展实例中注入依赖</li>
+<li>将拓展实例包装在适配的 <code>Wrapper</code> 对象中</li>
+<li>初始化拓展实例</li>
+</ol>
+<p>第一步是加载拓展类的关键，第三步和第四步是 <strong><code>Dubbo IOC</code></strong> 和 <strong><code>AOP</code></strong> 的具体实现。</p>
+<p>最后拓展实例的结构如下图。</p>
+<img src="/2023/11/28/how-does-Dubbo-SPI-works/Pasted%20image%2020231129024723.png" class="" title="拓展实例被包装后的结构图">
+
+<h3 id="加载-Extension-Class"><a href="#加载-Extension-Class" class="headerlink" title="加载 Extension Class"></a>加载 Extension Class</h3><figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">private</span> Map&lt;String, Class&lt;?&gt;&gt; getExtensionClasses() &#123;</span><br><span class="line">    <span class="comment">// 使用 getOrCreate 模式获取所有拓展类</span></span><br><span class="line">    Map&lt;String, Class&lt;?&gt;&gt; classes = cachedClasses.get();</span><br><span class="line">    <span class="keyword">if</span> (classes == <span class="literal">null</span>) &#123;</span><br><span class="line">        <span class="keyword">synchronized</span> (cachedClasses) &#123;</span><br><span class="line">            classes = cachedClasses.get();</span><br><span class="line">            <span class="keyword">if</span> (classes == <span class="literal">null</span>) &#123;</span><br><span class="line">                classes = loadExtensionClasses();</span><br><span class="line">                cachedClasses.set(classes);</span><br><span class="line">            &#125;</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="keyword">return</span> classes;</span><br><span class="line">&#125;</span><br><span class="line"></span><br><span class="line"><span class="keyword">private</span> Map&lt;String, Class&lt;?&gt;&gt; loadExtensionClasses() &#123;</span><br><span class="line">    <span class="comment">// 1. 缓存默认拓展名</span></span><br><span class="line">    cacheDefaultExtensionName();</span><br><span class="line"></span><br><span class="line">    Map&lt;String, Class&lt;?&gt;&gt; extensionClasses = <span class="keyword">new</span> <span class="title class_">HashMap</span>&lt;&gt;();</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 遍历加载策略，加载各个策略的目录下的配置文件，获取拓展类</span></span><br><span class="line">    <span class="keyword">for</span> (LoadingStrategy strategy : strategies) &#123;</span><br><span class="line">        loadDirectory(extensionClasses, strategy.directory(), type.getName(), strategy.preferExtensionClassLoader(),</span><br><span class="line">                strategy.overridden(), strategy.excludedPackages());</span><br><span class="line">        loadDirectory(extensionClasses, strategy.directory(), type.getName().replace(<span class="string">&quot;org.apache&quot;</span>, <span class="string">&quot;com.alibaba&quot;</span>),</span><br><span class="line">                strategy.preferExtensionClassLoader(), strategy.overridden(), strategy.excludedPackages());</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">return</span> extensionClasses;</span><br><span class="line">&#125;</span><br><span class="line"></span><br><span class="line"><span class="comment">// 如果存在默认拓展名，提取并缓存</span></span><br><span class="line"><span class="keyword">private</span> <span class="keyword">void</span> <span class="title function_">cacheDefaultExtensionName</span><span class="params">()</span> &#123;</span><br><span class="line">    <span class="comment">// 获取 SPI 注解</span></span><br><span class="line">    <span class="keyword">final</span> <span class="type">SPI</span> <span class="variable">defaultAnnotation</span> <span class="operator">=</span> type.getAnnotation(SPI.class);</span><br><span class="line">    <span class="keyword">if</span> (defaultAnnotation == <span class="literal">null</span>) &#123;</span><br><span class="line">        <span class="keyword">return</span>;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="type">String</span> <span class="variable">value</span> <span class="operator">=</span> defaultAnnotation.value();</span><br><span class="line">    <span class="keyword">if</span> ((value = value.trim()).length() &gt; <span class="number">0</span>) &#123;</span><br><span class="line">        <span class="comment">// 对 SPI 的 value 内容进行切分</span></span><br><span class="line">        String[] names = NAME_SEPARATOR.split(value);</span><br><span class="line">        <span class="comment">// 检测 name 是否合法</span></span><br><span class="line">        <span class="keyword">if</span> (names.length &gt; <span class="number">1</span>) &#123;</span><br><span class="line">            <span class="keyword">throw</span> <span class="keyword">new</span> <span class="title class_">IllegalStateException</span>(<span class="string">&quot;More than 1 default extension name on extension &quot;</span> + type.getName()</span><br><span class="line">                    + <span class="string">&quot;: &quot;</span> + Arrays.toString(names));</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="keyword">if</span> (names.length == <span class="number">1</span>) &#123;</span><br><span class="line">            <span class="comment">// 缓存默认拓展名，用于 getDefaultExtension</span></span><br><span class="line">            cachedDefaultName = names[<span class="number">0</span>];</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<h4 id="依次处理特定目录"><a href="#依次处理特定目录" class="headerlink" title="依次处理特定目录"></a>依次处理特定目录</h4><p>代码参考旧版本更容易理解。处理过程在本质上就是依次加载 <code>META-INF/dubbo/internal/</code>、<code>META-INF/dubbo/</code>、<code>META-INF/services/</code> 三个目录下的配置文件，获取拓展类。</p>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line">loadDirectory(extensionClasses, DUBBO_INTERNAL_DIRECTORY);</span><br><span class="line">loadDirectory(extensionClasses, DUBBO_DIRECTORY);</span><br><span class="line">loadDirectory(extensionClasses, SERVICES_DIRECTORY);</span><br></pre></td></tr></table></figure>
+
+<p>新版本使用原生的 <code>Java SPI</code> 加载 <code>LoadingStrategy</code>，允许用户自定义加载策略。</p>
+<ol>
+<li><code>DubboInternalLoadingStrategy</code>，目录 <code>META-INF/dubbo/internal/</code>，优先级最高</li>
+<li><code>DubboLoadingStrategy</code>，目录 <code>META-INF/dubbo/</code>，优先级普通</li>
+<li><code>ServicesLoadingStrategy</code>，目录 <code>META-INF/services/</code>，优先级最低</li>
+</ol>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">private</span> <span class="keyword">static</span> <span class="keyword">volatile</span> LoadingStrategy[] strategies = loadLoadingStrategies();</span><br><span class="line"></span><br><span class="line"><span class="keyword">private</span> <span class="keyword">static</span> LoadingStrategy[] loadLoadingStrategies() &#123;</span><br><span class="line">    <span class="comment">// 通过 Java SPI 加载 LoadingStrategy </span></span><br><span class="line">    <span class="keyword">return</span> stream(load(LoadingStrategy.class).spliterator(), <span class="literal">false</span>)</span><br><span class="line">            .sorted()</span><br><span class="line">            .toArray(LoadingStrategy[]::<span class="keyword">new</span>);</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<p><code>LoadingStrategy</code> 的 <code>Java SPI</code> 配置文件</p>
+<img src="/2023/11/28/how-does-Dubbo-SPI-works/Snipaste_2023-11-29_03-25-54.png" class="" title="LoadingStrategy 的 Java SPI 配置文件">
+
+<h4 id="loadDirectory-方法"><a href="#loadDirectory-方法" class="headerlink" title="loadDirectory 方法"></a>loadDirectory 方法</h4><p><code>loadDirectory</code> 方法先通过 <code>classLoader</code> 获取所有的资源链接，然后再通过 <code>loadResource</code> 方法加载资源。</p>
+<p>新版本中 <code>extensionLoaderClassLoaderFirst</code> 可以设置是否优先使用 <code>ExtensionLoader&#39;s ClassLoader</code> 获取资源链接。</p>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">private</span> <span class="keyword">void</span> <span class="title function_">loadDirectory</span><span class="params">(Map&lt;String, Class&lt;?&gt;&gt; extensionClasses, String dir, String type,</span></span><br><span class="line"><span class="params">                            <span class="type">boolean</span> extensionLoaderClassLoaderFirst, <span class="type">boolean</span> overridden, String... excludedPackages)</span> &#123;</span><br><span class="line">    <span class="comment">// filename = 文件夹路径 + type 的全限定名</span></span><br><span class="line">    <span class="type">String</span> <span class="variable">fileName</span> <span class="operator">=</span> dir + type;</span><br><span class="line">    <span class="keyword">try</span> &#123;</span><br><span class="line">        Enumeration&lt;java.net.URL&gt; urls = <span class="literal">null</span>;</span><br><span class="line">        <span class="type">ClassLoader</span> <span class="variable">classLoader</span> <span class="operator">=</span> findClassLoader();</span><br><span class="line"></span><br><span class="line">        <span class="comment">// 区别于旧版本：先从 ExtensionLoader&#x27;s ClassLoader 获取资源链接，默认为 false</span></span><br><span class="line">        <span class="keyword">if</span> (extensionLoaderClassLoaderFirst) &#123;</span><br><span class="line">            <span class="type">ClassLoader</span> <span class="variable">extensionLoaderClassLoader</span> <span class="operator">=</span> ExtensionLoader.class.getClassLoader();</span><br><span class="line">            <span class="keyword">if</span> (ClassLoader.getSystemClassLoader() != extensionLoaderClassLoader) &#123;</span><br><span class="line">                urls = extensionLoaderClassLoader.getResources(fileName);</span><br><span class="line">            &#125;</span><br><span class="line">        &#125;</span><br><span class="line"></span><br><span class="line">        <span class="comment">// 根据文件名加载所有同名文件</span></span><br><span class="line">        <span class="keyword">if</span> (urls == <span class="literal">null</span> || !urls.hasMoreElements()) &#123;</span><br><span class="line">            <span class="keyword">if</span> (classLoader != <span class="literal">null</span>) &#123;</span><br><span class="line">                urls = classLoader.getResources(fileName);</span><br><span class="line">            &#125; <span class="keyword">else</span> &#123;</span><br><span class="line">                urls = ClassLoader.getSystemResources(fileName);</span><br><span class="line">            &#125;</span><br><span class="line">        &#125;</span><br><span class="line"></span><br><span class="line">        <span class="keyword">if</span> (urls != <span class="literal">null</span>) &#123;</span><br><span class="line">            <span class="keyword">while</span> (urls.hasMoreElements()) &#123;</span><br><span class="line">                java.net.<span class="type">URL</span> <span class="variable">resourceURL</span> <span class="operator">=</span> urls.nextElement();</span><br><span class="line">                <span class="comment">// 加载资源</span></span><br><span class="line">                loadResource(extensionClasses, classLoader, resourceURL, overridden, excludedPackages);</span><br><span class="line">            &#125;</span><br><span class="line">        &#125;</span><br><span class="line">    &#125; <span class="keyword">catch</span> (Throwable t) &#123;</span><br><span class="line">        logger.error(<span class="string">&quot;Exception occurred when loading extension class (interface: &quot;</span> +</span><br><span class="line">                type + <span class="string">&quot;, description file: &quot;</span> + fileName + <span class="string">&quot;).&quot;</span>, t);</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<h4 id="loadResource-方法"><a href="#loadResource-方法" class="headerlink" title="loadResource 方法"></a>loadResource 方法</h4><p><code>loadResource</code> 方法用于读取和解析配置文件，并通过反射加载类，最后调用 <code>loadClass</code> 方法进行其他操作。<code>loadClass</code> 方法用于操作缓存。</p>
+<p>新版本中 <code>excludedPackages</code> 可以设置将指定包内的类都排除。</p>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">private</span> <span class="keyword">void</span> <span class="title function_">loadResource</span><span class="params">(Map&lt;String, Class&lt;?&gt;&gt; extensionClasses, ClassLoader classLoader,</span></span><br><span class="line"><span class="params">                            java.net.URL resourceURL, <span class="type">boolean</span> overridden, String... excludedPackages)</span> &#123;</span><br><span class="line">    <span class="keyword">try</span> &#123;</span><br><span class="line">        <span class="keyword">try</span> (<span class="type">BufferedReader</span> <span class="variable">reader</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">BufferedReader</span>(<span class="keyword">new</span> <span class="title class_">InputStreamReader</span>(resourceURL.openStream(), StandardCharsets.UTF_8))) &#123;</span><br><span class="line">            String line;</span><br><span class="line">            <span class="type">String</span> <span class="variable">clazz</span> <span class="operator">=</span> <span class="literal">null</span>;</span><br><span class="line">            <span class="comment">// 按行读取配置内容</span></span><br><span class="line">            <span class="keyword">while</span> ((line = reader.readLine()) != <span class="literal">null</span>) &#123;</span><br><span class="line">                <span class="comment">// 定位 # 字符，截取 # 字符之前的内容，# 字符之后的内容为注释，需要忽略</span></span><br><span class="line">                <span class="keyword">final</span> <span class="type">int</span> <span class="variable">ci</span> <span class="operator">=</span> line.indexOf(<span class="string">&#x27;#&#x27;</span>);</span><br><span class="line">                <span class="keyword">if</span> (ci &gt;= <span class="number">0</span>) &#123;</span><br><span class="line">                    line = line.substring(<span class="number">0</span>, ci);</span><br><span class="line">                &#125;</span><br><span class="line">                line = line.trim();</span><br><span class="line">                <span class="keyword">if</span> (line.length() &gt; <span class="number">0</span>) &#123;</span><br><span class="line">                    <span class="keyword">try</span> &#123;</span><br><span class="line">                        <span class="type">String</span> <span class="variable">name</span> <span class="operator">=</span> <span class="literal">null</span>;</span><br><span class="line">                        <span class="comment">// 定位 = 字符，以 = 字符为界，截取键值对</span></span><br><span class="line">                        <span class="type">int</span> <span class="variable">i</span> <span class="operator">=</span> line.indexOf(<span class="string">&#x27;=&#x27;</span>);</span><br><span class="line">                        <span class="keyword">if</span> (i &gt; <span class="number">0</span>) &#123;</span><br><span class="line">                            name = line.substring(<span class="number">0</span>, i).trim();</span><br><span class="line">                            clazz = line.substring(i + <span class="number">1</span>).trim();</span><br><span class="line">                        &#125; <span class="keyword">else</span> &#123;</span><br><span class="line">                            clazz = line;</span><br><span class="line">                        &#125;</span><br><span class="line">                        <span class="keyword">if</span> (StringUtils.isNotEmpty(clazz) &amp;&amp; !isExcluded(clazz, excludedPackages)) &#123;</span><br><span class="line">                            <span class="comment">// 加载类，并通过 loadClass 进行缓存</span></span><br><span class="line">                            <span class="comment">// 区别于旧版本：根据 excludedPackages 判断是否排除</span></span><br><span class="line">                            loadClass(extensionClasses, resourceURL, Class.forName(clazz, <span class="literal">true</span>, classLoader), name, overridden);</span><br><span class="line">                        &#125;</span><br><span class="line">                    &#125; <span class="keyword">catch</span> (Throwable t) &#123;</span><br><span class="line">                        <span class="type">IllegalStateException</span> <span class="variable">e</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">IllegalStateException</span>(</span><br><span class="line">                                <span class="string">&quot;Failed to load extension class (interface: &quot;</span> + type + <span class="string">&quot;, class line: &quot;</span> + line + <span class="string">&quot;) in &quot;</span> + resourceURL +</span><br><span class="line">                                        <span class="string">&quot;, cause: &quot;</span> + t.getMessage(), t);</span><br><span class="line">                        exceptions.put(line, e);</span><br><span class="line">                    &#125;</span><br><span class="line">                &#125;</span><br><span class="line">            &#125;</span><br><span class="line">        &#125;</span><br><span class="line">    &#125; <span class="keyword">catch</span> (Throwable t) &#123;</span><br><span class="line">        logger.error(<span class="string">&quot;Exception occurred when loading extension class (interface: &quot;</span> +</span><br><span class="line">                type + <span class="string">&quot;, class file: &quot;</span> + resourceURL + <span class="string">&quot;) in &quot;</span> + resourceURL, t);</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<h4 id="loadClass-方法"><a href="#loadClass-方法" class="headerlink" title="loadClass 方法"></a>loadClass 方法</h4><p><code>loadClass</code> 方法设置了多个缓存，比如 <code>cachedAdaptiveClass</code>、<code>cachedWrapperClasses</code>、<code>cachedNames</code> 和 <code>cachedClasses</code>。</p>
+<p>新版本中 <code>overridden</code> 可以设置是否覆盖 <code>cachedAdaptiveClass</code>、<code>cachedClasses</code> 的 <code>name-&gt;clazz</code>。</p>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">private</span> <span class="keyword">void</span> <span class="title function_">loadClass</span><span class="params">(Map&lt;String, Class&lt;?&gt;&gt; extensionClasses, java.net.URL resourceURL, Class&lt;?&gt; clazz, String name,</span></span><br><span class="line"><span class="params">                        <span class="type">boolean</span> overridden)</span> <span class="keyword">throws</span> NoSuchMethodException &#123;</span><br><span class="line">    <span class="comment">// 检测 clazz 是否合法</span></span><br><span class="line">    <span class="keyword">if</span> (!type.isAssignableFrom(clazz)) &#123;</span><br><span class="line">        <span class="keyword">throw</span> <span class="keyword">new</span> <span class="title class_">IllegalStateException</span>(<span class="string">&quot;Error occurred when loading extension class (interface: &quot;</span> +</span><br><span class="line">                type + <span class="string">&quot;, class line: &quot;</span> + clazz.getName() + <span class="string">&quot;), class &quot;</span></span><br><span class="line">                + clazz.getName() + <span class="string">&quot; is not subtype of interface.&quot;</span>);</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="keyword">if</span> (clazz.isAnnotationPresent(Adaptive.class)) &#123;</span><br><span class="line">        <span class="comment">// 检测 clazz 是否有 Adaptive 注解，有则设置 cachedAdaptiveClass 缓存</span></span><br><span class="line">        <span class="comment">// 区别于旧版本：根据 overriden 判断是否可覆盖</span></span><br><span class="line">        cacheAdaptiveClass(clazz, overridden);</span><br><span class="line">    &#125; <span class="keyword">else</span> <span class="keyword">if</span> (isWrapperClass(clazz)) &#123;</span><br><span class="line">        <span class="comment">// 检测 clazz 是否是 Wrapper 类型，是则添加到 cachedWrapperClasses 缓存</span></span><br><span class="line">        cacheWrapperClass(clazz);</span><br><span class="line">    &#125; <span class="keyword">else</span> &#123;</span><br><span class="line">        <span class="comment">// 检测 clazz 是否有默认的构造器方法，如果没有，则抛出异常</span></span><br><span class="line">        clazz.getConstructor();</span><br><span class="line">        <span class="keyword">if</span> (StringUtils.isEmpty(name)) &#123;</span><br><span class="line">            <span class="comment">// 如果 name 为空，则尝试从 Extension 注解中获取 name，或者使用小写的类名（可能截取 type 后缀）作为 name</span></span><br><span class="line">            name = findAnnotationName(clazz);</span><br><span class="line">            <span class="keyword">if</span> (name.length() == <span class="number">0</span>) &#123;</span><br><span class="line">                <span class="keyword">throw</span> <span class="keyword">new</span> <span class="title class_">IllegalStateException</span>(</span><br><span class="line">                        <span class="string">&quot;No such extension name for the class &quot;</span> + clazz.getName() + <span class="string">&quot; in the config &quot;</span> + resourceURL);</span><br><span class="line">            &#125;</span><br><span class="line">        &#125;</span><br><span class="line"></span><br><span class="line">        <span class="comment">// 切分 name</span></span><br><span class="line">        String[] names = NAME_SEPARATOR.split(name);</span><br><span class="line">        <span class="keyword">if</span> (ArrayUtils.isNotEmpty(names)) &#123;</span><br><span class="line">            <span class="comment">// 如果 clazz 有 Activate 注解，则缓存 names[0]-&gt;Activate 的映射关系</span></span><br><span class="line">            cacheActivateClass(clazz, names[<span class="number">0</span>]);</span><br><span class="line">            <span class="keyword">for</span> (String n : names) &#123;</span><br><span class="line">                <span class="comment">// 缓存 clazz-&gt;n 的映射关系</span></span><br><span class="line">                cacheName(clazz, n);</span><br><span class="line">                <span class="comment">// 缓存 n-&gt;clazz 的映射关系，传递到最后，终于轮到 extensionClasses</span></span><br><span class="line">                <span class="comment">// 区别于旧版本：根据 overriden 判断是否可覆盖</span></span><br><span class="line">                saveInExtensionClass(extensionClasses, clazz, n, overridden);</span><br><span class="line">            &#125;</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br><span class="line"></span><br><span class="line"><span class="keyword">private</span> <span class="keyword">void</span> <span class="title function_">cacheAdaptiveClass</span><span class="params">(Class&lt;?&gt; clazz, <span class="type">boolean</span> overridden)</span> &#123;</span><br><span class="line">    <span class="keyword">if</span> (cachedAdaptiveClass == <span class="literal">null</span> || overridden) &#123;</span><br><span class="line">        <span class="comment">// 可以设置是否覆盖</span></span><br><span class="line">        cachedAdaptiveClass = clazz;</span><br><span class="line">    &#125; <span class="keyword">else</span> <span class="keyword">if</span> (!cachedAdaptiveClass.equals(clazz)) &#123;</span><br><span class="line">        <span class="keyword">throw</span> <span class="keyword">new</span> <span class="title class_">IllegalStateException</span>(<span class="string">&quot;More than 1 adaptive class found: &quot;</span></span><br><span class="line">                + cachedAdaptiveClass.getName()</span><br><span class="line">                + <span class="string">&quot;, &quot;</span> + clazz.getName());</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br><span class="line"></span><br><span class="line"><span class="keyword">private</span> <span class="keyword">void</span> <span class="title function_">cacheWrapperClass</span><span class="params">(Class&lt;?&gt; clazz)</span> &#123;</span><br><span class="line">    <span class="keyword">if</span> (cachedWrapperClasses == <span class="literal">null</span>) &#123;</span><br><span class="line">        cachedWrapperClasses = <span class="keyword">new</span> <span class="title class_">ConcurrentHashSet</span>&lt;&gt;();</span><br><span class="line">    &#125;</span><br><span class="line">    cachedWrapperClasses.add(clazz);</span><br><span class="line">&#125;</span><br><span class="line"></span><br><span class="line"><span class="keyword">private</span> <span class="keyword">void</span> <span class="title function_">cacheActivateClass</span><span class="params">(Class&lt;?&gt; clazz, String name)</span> &#123;</span><br><span class="line">    <span class="type">Activate</span> <span class="variable">activate</span> <span class="operator">=</span> clazz.getAnnotation(Activate.class);</span><br><span class="line">    <span class="keyword">if</span> (activate != <span class="literal">null</span>) &#123;</span><br><span class="line">        cachedActivates.put(name, activate);</span><br><span class="line">    &#125; <span class="keyword">else</span> &#123;</span><br><span class="line">        <span class="comment">// support com.alibaba.dubbo.common.extension.Activate</span></span><br><span class="line">        com.alibaba.dubbo.common.extension.<span class="type">Activate</span> <span class="variable">oldActivate</span> <span class="operator">=</span></span><br><span class="line">                clazz.getAnnotation(com.alibaba.dubbo.common.extension.Activate.class);</span><br><span class="line">        <span class="keyword">if</span> (oldActivate != <span class="literal">null</span>) &#123;</span><br><span class="line">            cachedActivates.put(name, oldActivate);</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<h3 id="Dubbo-IOC"><a href="#Dubbo-IOC" class="headerlink" title="Dubbo IOC"></a>Dubbo IOC</h3><p><code>Dubbo IOC</code> 是通过 <code>setter</code> 方法注入依赖。<code>Dubbo</code> 首先通过反射获取目标类的所有方法，然后遍历方法列表，检测方法名是否具有 <code>setter</code> 方法特征并满足条件，若有，则通过 <code>objectFactory</code> 获取依赖对象，最后通过反射调用 <code>setter</code> 方法将依赖设置到目标对象中。</p>
+<blockquote>
+<p>与 <code>Spring IOC</code> 相比，<code>Dubbo IOC</code> 实现的依赖注入功能更加简单，代码也更加容易理解。</p>
+</blockquote>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">private</span> T <span class="title function_">injectExtension</span><span class="params">(T instance)</span> &#123;</span><br><span class="line">    <span class="comment">// 检测是否有 objectFactory</span></span><br><span class="line">    <span class="keyword">if</span> (objectFactory == <span class="literal">null</span>) &#123;</span><br><span class="line">        <span class="keyword">return</span> instance;</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="keyword">try</span> &#123;</span><br><span class="line">        <span class="comment">// 遍历目标类的所有方法</span></span><br><span class="line">        <span class="comment">// 区别于旧版本：增加了对 DisbaleInject、Inject 注解的处理</span></span><br><span class="line">        <span class="keyword">for</span> (Method method : instance.getClass().getMethods()) &#123;</span><br><span class="line">            <span class="comment">// 检测是否是 setter 方法</span></span><br><span class="line">            <span class="keyword">if</span> (!isSetter(method)) &#123;</span><br><span class="line">                <span class="keyword">continue</span>;</span><br><span class="line">            &#125;</span><br><span class="line"></span><br><span class="line">            <span class="comment">// 检测是否标注 DisableInject 注解</span></span><br><span class="line">            <span class="keyword">if</span> (method.getAnnotation(DisableInject.class) != <span class="literal">null</span>) &#123;</span><br><span class="line">                <span class="keyword">continue</span>;</span><br><span class="line">            &#125;</span><br><span class="line"></span><br><span class="line">            <span class="comment">// 检测参数类型是否是原始类型</span></span><br><span class="line">            Class&lt;?&gt; pt = method.getParameterTypes()[<span class="number">0</span>];</span><br><span class="line">            <span class="keyword">if</span> (ReflectUtils.isPrimitives(pt)) &#123;</span><br><span class="line">                <span class="keyword">continue</span>;</span><br><span class="line">            &#125;</span><br><span class="line"></span><br><span class="line">            <span class="comment">// 获取属性名</span></span><br><span class="line">            <span class="type">String</span> <span class="variable">property</span> <span class="operator">=</span> getSetterProperty(method);</span><br><span class="line">            <span class="comment">// 检测是否标注 Inject 注解</span></span><br><span class="line">            <span class="type">Inject</span> <span class="variable">inject</span> <span class="operator">=</span> method.getAnnotation(Inject.class);</span><br><span class="line">            <span class="keyword">if</span> (inject == <span class="literal">null</span>) &#123;</span><br><span class="line">                injectValue(instance, method, pt, property);</span><br><span class="line">            &#125; <span class="keyword">else</span> &#123;</span><br><span class="line">                <span class="comment">// 检测 Inject 是否启动、是否按照类型注入</span></span><br><span class="line">                <span class="keyword">if</span> (!inject.enable()) &#123;</span><br><span class="line">                    <span class="keyword">continue</span>;</span><br><span class="line">                &#125;</span><br><span class="line"></span><br><span class="line">                <span class="keyword">if</span> (inject.type() == Inject.InjectType.ByType) &#123;</span><br><span class="line">                    injectValue(instance, method, pt, <span class="literal">null</span>);</span><br><span class="line">                &#125; <span class="keyword">else</span> &#123;</span><br><span class="line">                    injectValue(instance, method, pt, property);</span><br><span class="line">                &#125;</span><br><span class="line">            &#125;</span><br><span class="line">        &#125;</span><br><span class="line">    &#125; <span class="keyword">catch</span> (Exception e) &#123;</span><br><span class="line">        logger.error(e.getMessage(), e);</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="keyword">return</span> instance;</span><br><span class="line">&#125;</span><br><span class="line"></span><br><span class="line"><span class="comment">// 获取属性名</span></span><br><span class="line"><span class="keyword">private</span> String <span class="title function_">getSetterProperty</span><span class="params">(Method method)</span> &#123;</span><br><span class="line">    <span class="keyword">return</span> method.getName().length() &gt; <span class="number">3</span> ? method.getName().substring(<span class="number">3</span>, <span class="number">4</span>).toLowerCase() + method.getName().substring(<span class="number">4</span>) : <span class="string">&quot;&quot;</span>;</span><br><span class="line">&#125;</span><br><span class="line"></span><br><span class="line"><span class="comment">// public、set 开头、只有一个参数</span></span><br><span class="line"><span class="keyword">private</span> <span class="type">boolean</span> <span class="title function_">isSetter</span><span class="params">(Method method)</span> &#123;</span><br><span class="line">    <span class="keyword">return</span> method.getName().startsWith(<span class="string">&quot;set&quot;</span>)</span><br><span class="line">            &amp;&amp; method.getParameterTypes().length == <span class="number">1</span></span><br><span class="line">            &amp;&amp; Modifier.isPublic(method.getModifiers());</span><br><span class="line">&#125;</span><br><span class="line"></span><br><span class="line"><span class="keyword">private</span> <span class="keyword">void</span> <span class="title function_">injectValue</span><span class="params">(T instance, Method method, Class&lt;?&gt; pt, String property)</span> &#123;</span><br><span class="line">    <span class="keyword">try</span> &#123;</span><br><span class="line">        <span class="comment">// 从 ObjectFactory 中获取依赖对象</span></span><br><span class="line">        <span class="type">Object</span> <span class="variable">object</span> <span class="operator">=</span> objectFactory.getExtension(pt, property);</span><br><span class="line">        <span class="keyword">if</span> (object != <span class="literal">null</span>) &#123;</span><br><span class="line">            <span class="comment">// 通过反射调用 setter 方法设置依赖</span></span><br><span class="line">            method.invoke(instance, object);</span><br><span class="line">        &#125;</span><br><span class="line">    &#125; <span class="keyword">catch</span> (Exception e) &#123;</span><br><span class="line">        logger.error(<span class="string">&quot;Failed to inject via method &quot;</span> + method.getName()</span><br><span class="line">                + <span class="string">&quot; of interface &quot;</span> + type.getName() + <span class="string">&quot;: &quot;</span> + e.getMessage(), e);</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<p><code>objectFactory</code> 是 <code>ExtensionFactory</code> 的自适应拓展，通过它获取依赖对象，本质上是根据目标拓展类获取 <code>ExtensionLoader</code>，然后获取其自适应拓展，过程代码如下。具体我们不再深入分析，可以参考<a href="/2023/11/29/how-does-Dubbo-SPI-adaptive-extension-works/" title="Dubbo SPI 自适应拓展的工作原理">Dubbo SPI 自适应拓展的工作原理</a>。</p>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> &lt;T&gt; T <span class="title function_">getExtension</span><span class="params">(Class&lt;T&gt; type, String name)</span> &#123;</span><br><span class="line">    <span class="keyword">if</span> (type.isInterface() &amp;&amp; type.isAnnotationPresent(SPI.class)) &#123;</span><br><span class="line">        ExtensionLoader&lt;T&gt; loader = ExtensionLoader.getExtensionLoader(type);</span><br><span class="line">        <span class="keyword">if</span> (!loader.getSupportedExtensions().isEmpty()) &#123;</span><br><span class="line">            <span class="keyword">return</span> loader.getAdaptiveExtension();</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="keyword">return</span> <span class="literal">null</span>;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<h2 id="参考文章"><a href="#参考文章" class="headerlink" title="参考文章"></a>参考文章</h2><ul>
+<li><a href="https://cn.dubbo.apache.org/zh-cn/docsv2.7/dev/source/dubbo-spi/">Dubbo SPI</a></li>
+</ul>
+]]></content>
+      <tags>
+        <tag>java</tag>
+        <tag>dubbo</tag>
+        <tag>spi</tag>
+      </tags>
+  </entry>
+  <entry>
+    <title>当 MySQL 以 skip-name-resolve 模式启动时如何使用 grant 命令</title>
+    <url>/2023/12/13/how-to-grant-when-MySQL-started-with-skip-name-resolve-mode/</url>
+    <content><![CDATA[<p>本文介绍了 <code>MySQL</code> 中 <code>skip-name-resolve</code> 参数<strong>对连接的优化作用</strong>，随之而来的权限表<strong>仅可使用 <code>IP</code> 的限制</strong>，以及如何在无法提前确定 <code>IP</code> 的情况下使用 <code>grant</code> 命令<strong>搭配通配符 <code>%</code> 进行授权</strong>。</p>
+<span id="more"></span>
+
+<h2 id="背景介绍"><a href="#背景介绍" class="headerlink" title="背景介绍"></a>背景介绍</h2><p>在 <code>MySQL</code> 新建一个用户 <code>exporter</code> 给 <code>mysqld-exporter</code> 使用，然后通过 <code>grant</code> 命令授予该用户部分权限。执行命令如下：</p>
+<figure class="highlight sql"><table><tr><td class="code"><pre><span class="line"><span class="keyword">CREATE</span> <span class="keyword">USER</span> <span class="string">&#x27;exporter&#x27;</span>@<span class="string">&#x27;localhost&#x27;</span> IDENTIFIED <span class="keyword">BY</span> <span class="string">&#x27;XXXXXXXX&#x27;</span> <span class="keyword">WITH</span> MAX_USER_CONNECTIONS <span class="number">3</span>;</span><br><span class="line"><span class="keyword">GRANT</span> PROCESS, REPLICATION CLIENT, <span class="keyword">SELECT</span> <span class="keyword">ON</span> <span class="operator">*</span>.<span class="operator">*</span> <span class="keyword">TO</span> <span class="string">&#x27;exporter&#x27;</span>@<span class="string">&#x27;localhost&#x27;</span>;</span><br></pre></td></tr></table></figure>
+
+<p>在执行时提示“这次 <code>grant</code> 需要关闭 <code>skip-name-resolve</code> 参数然后重启 <code>MySQL</code> 才能生效”。</p>
+<figure class="highlight console"><table><tr><td class="code"><pre><span class="line">0 row(s) affected, 1 warning(s): 1285 MySQL is started in --skip-name-resolve mode; you must restart it without this switch for this grant to work</span><br></pre></td></tr></table></figure>
+
 <p>本着默认的参数不随便修改的想法，我们来看一看 <code>skip-name-resolve</code> 参数究竟有什么用。</p>
 <h2 id="skip-name-resolve-的作用"><a href="#skip-name-resolve-的作用" class="headerlink" title="skip-name-resolve 的作用"></a>skip-name-resolve 的作用</h2><p><code>MySQL</code> 在启动时默认使用 <code>skip-name-resolve</code> 参数。顾名思义，该参数用于跳过 <code>MySQL</code> 的 <code>DNS</code> 解析。关于 <code>MySQL</code> 是如何使用 <code>DNS</code> 的，官方文档是这样介绍的：</p>
 <p>当一个新线程连接到 <code>mysqld</code>，<code>mysqld</code> 会生成一个新线程去处理该请求。该线程首先检查主机名是否在主机名缓存中，如果没有那么该线程会调用 <code>gethostbyaddr_r()</code> 和 <code>gethostbyname_r()</code> 来解析主机名。如果操作系统不支持上述线程安全的调用，那么该线程会加锁然后调用 <code>gethostbyaddr()</code> 和 <code>gethostbyname()</code>。这种情况下，在第一个线程准备好之前，没有其他线程可以解析不在主机名缓存中的其他主机名。<code>MySQL</code> 允许通过 <code>skip-name-resolve</code> 参数禁用 <code>DNS</code> 解析，但是如果禁用的话，在 <code>MySQL</code> 的权限表中就只能使用 <code>IP</code>。</p>
@@ -4894,50 +4652,164 @@
       </tags>
   </entry>
   <entry>
-    <title>synchronized 锁机制的分析和验证</title>
-    <url>/2023/12/19/analysis-and-verification-of-the-synchronized-lock-mechanism/</url>
-    <content><![CDATA[<p>本文详细介绍了 <code>Java</code> 中 <code>synchronized</code> 锁的机制、存储结构、优化措施以及升级过程，并通过 <code>jol-core</code> 演示 <code>Mark Word</code> 的变化来验证锁升级的多个 <code>case</code>。</p>
+    <title>ComponentScan 扫描路径覆盖的真相</title>
+    <url>/2023/12/11/the-truth-about-override-of-ComponentScan-basePackages/</url>
+    <content><![CDATA[<p><code>@ComponentScan</code> 注解是 <code>Spring</code> 中很常用的注解，用于扫描并加载指定类路径下的 <code>Bean</code>，而 <code>Spring Boot</code> 为了便捷使用 <code>@SpringBootApplication</code> 组合注解集成了 <code>@ComponentScan</code> 的能力。也许你听说过使用后者会覆盖前者中关于包扫描的设置，但你是否质疑过这个“不合常理”的结论？是否好奇过为什么它们不像其他注解在嵌套使用时可以同时生效？又是否好奇过 <code>@SpringBootApplication</code> 可以间接设置 <code>@ComponentScan</code> 属性的原因？本文从源码角度分析 <code>@ComponentScan</code> 的工作原理，揭示它独特的检索算法和注解层次结构中的属性覆盖机制。</p>
 <span id="more"></span>
 
+<ul>
+<li>本文的写作动机继承自<a href="/2023/11/23/source-code-analysis-of-Spring-Configuration-annotation/" title="Spring @Configuration 注解的源码分析">Spring @Configuration 注解的源码分析</a>，处理 <code>@ComponentScan</code> 是处理 <code>@Configuration</code> 过程的一部分。</li>
+</ul>
+<h2 id="入口"><a href="#入口" class="headerlink" title="入口"></a>入口</h2><p>对于标注了 <code>@ComponentScan</code> 注解的配置类，处理过程如下：</p>
+<ul>
+<li>获取 <code>@ComponentScan</code> 的注解属性</li>
+<li>遍历注解属性集合，依次根据其中的信息进行扫描，获取 <code>Bean</code> 定义</li>
+<li>如果获取到的 <code>Bean</code> 定义中有任何其他配置类，将递归解析（处理配置类）</li>
+</ul>
 <blockquote>
-<p>待完善</p>
+<p>这里和处理 <code>@Import</code> 的过程很像，都出现了递归解析新获得的配置类。</p>
 </blockquote>
-<p>利用 <code>synchronized</code> 实现同步的基础：<code>Java</code> 中的每一个对象都可以作为锁。具体表现为以下 <code>3</code> 种形式。</p>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">protected</span> <span class="keyword">final</span> SourceClass <span class="title function_">doProcessConfigurationClass</span><span class="params">(ConfigurationClass configClass, SourceClass sourceClass)</span></span><br><span class="line">        <span class="keyword">throws</span> IOException &#123;</span><br><span class="line">    <span class="comment">// ...</span></span><br><span class="line">    <span class="comment">// 处理任何 @ComponentScan 注解</span></span><br><span class="line">    <span class="comment">// 获取 @ComponentScan 的注解属性，该注解是可重复的</span></span><br><span class="line">    Set&lt;AnnotationAttributes&gt; componentScans = AnnotationConfigUtils.attributesForRepeatable(</span><br><span class="line">            sourceClass.getMetadata(), ComponentScans.class, ComponentScan.class);</span><br><span class="line">    <span class="keyword">if</span> (!componentScans.isEmpty() &amp;&amp;</span><br><span class="line">            !<span class="built_in">this</span>.conditionEvaluator.shouldSkip(sourceClass.getMetadata(), ConfigurationPhase.REGISTER_BEAN)) &#123;</span><br><span class="line">        <span class="comment">// 遍历</span></span><br><span class="line">        <span class="keyword">for</span> (AnnotationAttributes componentScan : componentScans) &#123;</span><br><span class="line">            <span class="comment">// 如果配置类被标注了 @ComponentScan -&gt; 立即扫描</span></span><br><span class="line">            Set&lt;BeanDefinitionHolder&gt; scannedBeanDefinitions =</span><br><span class="line">                    <span class="built_in">this</span>.componentScanParser.parse(componentScan, sourceClass.getMetadata().getClassName());</span><br><span class="line">            <span class="comment">// 检测被扫描到的 Bean 定义中是否有任何其他配置类，如有需要递归解析</span></span><br><span class="line">            <span class="keyword">for</span> (BeanDefinitionHolder holder : scannedBeanDefinitions) &#123;</span><br><span class="line">                <span class="keyword">if</span> (ConfigurationClassUtils.checkConfigurationClassCandidate(</span><br><span class="line">                        holder.getBeanDefinition(), <span class="built_in">this</span>.metadataReaderFactory)) &#123;</span><br><span class="line">                    <span class="comment">// 递归解析配置类</span></span><br><span class="line">                    parse(holder.getBeanDefinition().getBeanClassName(), holder.getBeanName());</span><br><span class="line">                &#125;</span><br><span class="line">            &#125;</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="comment">// ...</span></span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<h2 id="扫描获取-Bean-定义"><a href="#扫描获取-Bean-定义" class="headerlink" title="扫描获取 Bean 定义"></a>扫描获取 Bean 定义</h2><p>我们先跳过“获取 <code>@ComponentScan</code> 的注解属性”的过程，来看“扫描获取 <code>Bean</code> 定义”的过程。扫描是通过 <code>ComponentScanAnnotationParser</code> 的 <code>parse</code> 方法完成的，这个方法很长，但逻辑并不复杂，主要是为 <code>ClassPathBeanDefinitionScanner</code> 设置一些来自 <code>@ComponentScan</code> 的注解属性值，最终执行扫描。<code>ClassPathBeanDefinitionScanner</code> 顾名思义是基于类路径的 <code>Bean</code> 定义扫描器，真正的扫描工作全部委托给了它。在这些设置过程中，我们需要关注 <code>basePackages</code> 的设置：</p>
 <ul>
-<li>对于普通同步方法，锁是当前实例对象。</li>
-<li>对于静态同步方法，锁是当前类的 <code>Class</code> 对象。</li>
-<li>对于同步方法块，锁是 <code>synchronized</code> 括号里配置的对象。</li>
+<li>使用 Set 存储合并结果，用于去重</li>
+<li>获取设置的 <code>basePackages</code> 值并添加</li>
+<li>获取设置的 <code>basePackageClasses</code> 值，转换为它们所在的包名并添加</li>
+<li>如果结果集现在还是空的，获取被标注的配置类所在的包名并添加</li>
 </ul>
-<p>当一个线程试图访问同步代码块时，它首先必须得到锁，退出或抛出异常时必须释放锁。</p>
+<blockquote>
+<p>最后一条规则就是“默认情况下扫描配置类所在的包”的说法由来，并且根据代码可知，如果主动设置了值，这条规则就不起作用了。</p>
+</blockquote>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> Set&lt;BeanDefinitionHolder&gt; <span class="title function_">parse</span><span class="params">(AnnotationAttributes componentScan, <span class="keyword">final</span> String declaringClass)</span> &#123;</span><br><span class="line">    Assert.state(<span class="built_in">this</span>.environment != <span class="literal">null</span>, <span class="string">&quot;Environment must not be null&quot;</span>);</span><br><span class="line">    Assert.state(<span class="built_in">this</span>.resourceLoader != <span class="literal">null</span>, <span class="string">&quot;ResourceLoader must not be null&quot;</span>);</span><br><span class="line">    <span class="comment">// 创建 ClassPathBeanDefinitionScanner</span></span><br><span class="line">    <span class="type">ClassPathBeanDefinitionScanner</span> <span class="variable">scanner</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">ClassPathBeanDefinitionScanner</span>(<span class="built_in">this</span>.registry,</span><br><span class="line">            componentScan.getBoolean(<span class="string">&quot;useDefaultFilters&quot;</span>), <span class="built_in">this</span>.environment, <span class="built_in">this</span>.resourceLoader);</span><br><span class="line">    <span class="comment">// Bean 名称生成器</span></span><br><span class="line">    Class&lt;? <span class="keyword">extends</span> <span class="title class_">BeanNameGenerator</span>&gt; generatorClass = componentScan.getClass(<span class="string">&quot;nameGenerator&quot;</span>);</span><br><span class="line">    <span class="type">boolean</span> <span class="variable">useInheritedGenerator</span> <span class="operator">=</span> (BeanNameGenerator.class == generatorClass);</span><br><span class="line">    scanner.setBeanNameGenerator(useInheritedGenerator ? <span class="built_in">this</span>.beanNameGenerator :</span><br><span class="line">            BeanUtils.instantiateClass(generatorClass));</span><br><span class="line"></span><br><span class="line">    <span class="type">ScopedProxyMode</span> <span class="variable">scopedProxyMode</span> <span class="operator">=</span> componentScan.getEnum(<span class="string">&quot;scopedProxy&quot;</span>);</span><br><span class="line">    <span class="keyword">if</span> (scopedProxyMode != ScopedProxyMode.DEFAULT) &#123;</span><br><span class="line">        scanner.setScopedProxyMode(scopedProxyMode);</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="keyword">else</span> &#123;</span><br><span class="line">        Class&lt;? <span class="keyword">extends</span> <span class="title class_">ScopeMetadataResolver</span>&gt; resolverClass = componentScan.getClass(<span class="string">&quot;scopeResolver&quot;</span>);</span><br><span class="line">        scanner.setScopeMetadataResolver(BeanUtils.instantiateClass(resolverClass));</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    scanner.setResourcePattern(componentScan.getString(<span class="string">&quot;resourcePattern&quot;</span>));</span><br><span class="line">    <span class="comment">// 设置 Filter</span></span><br><span class="line">    <span class="keyword">for</span> (AnnotationAttributes filter : componentScan.getAnnotationArray(<span class="string">&quot;includeFilters&quot;</span>)) &#123;</span><br><span class="line">        <span class="keyword">for</span> (TypeFilter typeFilter : typeFiltersFor(filter)) &#123;</span><br><span class="line">            scanner.addIncludeFilter(typeFilter);</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="keyword">for</span> (AnnotationAttributes filter : componentScan.getAnnotationArray(<span class="string">&quot;excludeFilters&quot;</span>)) &#123;</span><br><span class="line">        <span class="keyword">for</span> (TypeFilter typeFilter : typeFiltersFor(filter)) &#123;</span><br><span class="line">            scanner.addExcludeFilter(typeFilter);</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="comment">// 是否懒加载</span></span><br><span class="line">    <span class="type">boolean</span> <span class="variable">lazyInit</span> <span class="operator">=</span> componentScan.getBoolean(<span class="string">&quot;lazyInit&quot;</span>);</span><br><span class="line">    <span class="keyword">if</span> (lazyInit) &#123;</span><br><span class="line">        scanner.getBeanDefinitionDefaults().setLazyInit(<span class="literal">true</span>);</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="comment">// 设置 basePackages（使用 Set 去重）</span></span><br><span class="line">    Set&lt;String&gt; basePackages = <span class="keyword">new</span> <span class="title class_">LinkedHashSet</span>&lt;String&gt;();</span><br><span class="line">    <span class="comment">// 获取设置的 basePackages 值</span></span><br><span class="line">    String[] basePackagesArray = componentScan.getStringArray(<span class="string">&quot;basePackages&quot;</span>);</span><br><span class="line">    <span class="keyword">for</span> (String pkg : basePackagesArray) &#123;</span><br><span class="line">        <span class="comment">// 允许占位符</span></span><br><span class="line">        String[] tokenized = StringUtils.tokenizeToStringArray(<span class="built_in">this</span>.environment.resolvePlaceholders(pkg),</span><br><span class="line">                ConfigurableApplicationContext.CONFIG_LOCATION_DELIMITERS);</span><br><span class="line">        basePackages.addAll(Arrays.asList(tokenized));</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="comment">// 获取 basePackageClasses，本质上是为了获取它们所在的包名</span></span><br><span class="line">    <span class="keyword">for</span> (Class&lt;?&gt; clazz : componentScan.getClassArray(<span class="string">&quot;basePackageClasses&quot;</span>)) &#123;</span><br><span class="line">        basePackages.add(ClassUtils.getPackageName(clazz));</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="comment">// 如果为空，获取被标注的配置类所在的包名</span></span><br><span class="line">    <span class="keyword">if</span> (basePackages.isEmpty()) &#123;</span><br><span class="line">        basePackages.add(ClassUtils.getPackageName(declaringClass));</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="comment">// 排除被标注的配置类本身</span></span><br><span class="line">    scanner.addExcludeFilter(<span class="keyword">new</span> <span class="title class_">AbstractTypeHierarchyTraversingFilter</span>(<span class="literal">false</span>, <span class="literal">false</span>) &#123;</span><br><span class="line">        <span class="meta">@Override</span></span><br><span class="line">        <span class="keyword">protected</span> <span class="type">boolean</span> <span class="title function_">matchClassName</span><span class="params">(String className)</span> &#123;</span><br><span class="line">            <span class="keyword">return</span> declaringClass.equals(className);</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;);</span><br><span class="line">    <span class="comment">// 执行扫描</span></span><br><span class="line">    <span class="keyword">return</span> scanner.doScan(StringUtils.toStringArray(basePackages));</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<p><code>parse</code> 方法与其说是解析，不如说是封装了一些设置并最终调用 <code>ClassPathBeanDefinitionScanner</code>，而设置的属性值来源于 <code>@ComponentScan</code> 的注解属性。关于获取 <code>@ComponentScan</code> 的注解属性的方法 <code>AnnotationConfigUtils.attributesForRepeatable</code> 在分析 <code>@PropertySource</code> 时也曾经遇到过，顾名思义我们知道它应该是用于获取可重复的注解的属性。可是它和直接获取注解对象有什么区别呢？</p>
+<blockquote>
+<p>我们知道 <code>@SpringBootApplication</code> 拥有和 <code>@ComponentScan</code> 具备相似的功能，并且可以使用 <code>scanBasePackages</code> 和 <code>scanBasePackageClasses</code> 这两个属性设置扫描的包。也许你还知道 <code>@SpringBootApplication</code> 之所以如此是因为它被标注了 <code>@ComponentScan</code>，<code>scanBasePackages</code> 和 <code>scanBasePackageClasses</code> 分别是它的元注解 <code>@ComponentScan</code> 中 <code>basePackages</code> 和 <code>basePackageClasses</code> 的别名。你甚至可能知道<strong>如果在配置类上使用 <code>@ComponentScan</code> 设置包扫描后会导致 <code>@SpringBootApplication</code> 设置的包扫描失效</strong>。<br><strong>可是为什么呢？</strong>在 <code>Spring</code> 中我们会看到从指定类上直接获取目标注解的代码，我们还会看到递归地从元注解上获取目标注解的代码，我们使用 <code>@ComponentScan</code> 的经验告诉我们可重复注解不是覆盖彼此而是共同生效，那么为什么 <code>@SpringBootApplication</code> 上的 <code>@ComponentScan</code> 就被覆盖了呢？<strong>想当然的认为 <code>@SpringBootApplication</code> 上标注了 <code>@ComponentScan</code> 是一切的原因是不够的</strong>。</p>
+</blockquote>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="meta">@Target(ElementType.TYPE)</span></span><br><span class="line"><span class="meta">@Retention(RetentionPolicy.RUNTIME)</span></span><br><span class="line"><span class="meta">@Documented</span></span><br><span class="line"><span class="meta">@Inherited</span></span><br><span class="line"><span class="meta">@SpringBootConfiguration</span></span><br><span class="line"><span class="meta">@EnableAutoConfiguration</span></span><br><span class="line"><span class="meta">@ComponentScan(excludeFilters = &#123;</span></span><br><span class="line"><span class="meta">		@Filter(type = FilterType.CUSTOM, classes = TypeExcludeFilter.class),</span></span><br><span class="line"><span class="meta">		@Filter(type = FilterType.CUSTOM, classes = AutoConfigurationExcludeFilter.class) &#125;)</span></span><br><span class="line"><span class="keyword">public</span> <span class="meta">@interface</span> SpringBootApplication &#123;</span><br><span class="line"></span><br><span class="line">	<span class="meta">@AliasFor(annotation = EnableAutoConfiguration.class)</span></span><br><span class="line">	Class&lt;?&gt;[] exclude() <span class="keyword">default</span> &#123;&#125;;</span><br><span class="line"></span><br><span class="line">	<span class="meta">@AliasFor(annotation = EnableAutoConfiguration.class)</span></span><br><span class="line">	String[] excludeName() <span class="keyword">default</span> &#123;&#125;;</span><br><span class="line"></span><br><span class="line">	<span class="meta">@AliasFor(annotation = ComponentScan.class, attribute = &quot;basePackages&quot;)</span></span><br><span class="line">	String[] scanBasePackages() <span class="keyword">default</span> &#123;&#125;;</span><br><span class="line"></span><br><span class="line">	<span class="meta">@AliasFor(annotation = ComponentScan.class, attribute = &quot;basePackageClasses&quot;)</span></span><br><span class="line">	Class&lt;?&gt;[] scanBasePackageClasses() <span class="keyword">default</span> &#123;&#125;;</span><br><span class="line"></span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<h2 id="获取注解属性"><a href="#获取注解属性" class="headerlink" title="获取注解属性"></a>获取注解属性</h2><p><code>attributesForRepeatable</code> 方法有两个重载方法，最终调用的版本如下。先后处理了 <code>@ComponentScan</code> 和 <code>@ComponentScans</code>。</p>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">static</span> Set&lt;AnnotationAttributes&gt; <span class="title function_">attributesForRepeatable</span><span class="params">(AnnotationMetadata metadata,</span></span><br><span class="line"><span class="params">        String containerClassName, String annotationClassName)</span> &#123;</span><br><span class="line">    <span class="comment">// Set 用于存储结果</span></span><br><span class="line">    Set&lt;AnnotationAttributes&gt; result = <span class="keyword">new</span> <span class="title class_">LinkedHashSet</span>&lt;AnnotationAttributes&gt;();</span><br><span class="line">    <span class="comment">// 处理 @ComponentScan</span></span><br><span class="line">    addAttributesIfNotNull(result, metadata.getAnnotationAttributes(annotationClassName, <span class="literal">false</span>));</span><br><span class="line">    <span class="comment">// 处理 @ComponentScans</span></span><br><span class="line">    Map&lt;String, Object&gt; container = metadata.getAnnotationAttributes(containerClassName, <span class="literal">false</span>);</span><br><span class="line">    <span class="keyword">if</span> (container != <span class="literal">null</span> &amp;&amp; container.containsKey(<span class="string">&quot;value&quot;</span>)) &#123;</span><br><span class="line">        <span class="keyword">for</span> (Map&lt;String, Object&gt; containedAttributes : (Map&lt;String, Object&gt;[]) container.get(<span class="string">&quot;value&quot;</span>)) &#123;</span><br><span class="line">            addAttributesIfNotNull(result, containedAttributes);</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="keyword">return</span> Collections.unmodifiableSet(result);</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<h3 id="检索注解的规则"><a href="#检索注解的规则" class="headerlink" title="检索注解的规则"></a>检索注解的规则</h3><p>根据注释，<code>getAnnotationAttributes</code> 方法检索给定类型的注解的属性，<strong>检索的目标可以是直接注解也可以是元注解</strong>，同时考虑<strong>组合注解上的属性覆盖</strong>。</p>
 <ul>
-<li>在 <code>JVM</code> 层面，<code>synchronized</code> 锁是基于进入和退出 <code>Monitor</code> 来实现的，每一个对象都有一个 <code>Monitor</code> 与之相关联。</li>
-<li>在字节码层面，同步方法块是使用 <code>monitorenter</code> 和 <code>monitorexit</code> 指令实现的，前者在编译后插入到同步方法块的开始位置，后者插入到同步方法块的结束位置和异常位置。</li>
+<li>元注解指的是标注在其他注解上的注解，用于对被标注的注解进行说明，比如 <code>@SpringBootApplication</code> 上的 <code>@ComponentScan</code> 就被称为元注解，此时 <code>@SpringBootApplication</code> 被称为组合注解</li>
+<li>组合注解中存在属性覆盖现象</li>
 </ul>
-<h2 id="存储结构"><a href="#存储结构" class="headerlink" title="存储结构"></a>存储结构</h2><blockquote>
-<p>锁存在哪里呢？锁里面又会存储什么信息呢？</p>
+<blockquote>
+<p>其实这两点分别对应了我们想要探究的两个问题：<code>@ComponentScan</code> 究竟是如何被检索的？注解属性比如 <code>basePackages</code> 又是如何被覆盖的？</p>
 </blockquote>
-<h3 id="对象头"><a href="#对象头" class="headerlink" title="对象头"></a>对象头</h3><p><code>synchronized</code> 用的锁是存在 <code>Java</code> 对象头（<code>object header</code>）里的。如果对象是数组类型，则虚拟机用 <code>3</code> 字宽（<code>Word</code>）存储对象头，如果对象是非数组类型，则用 <code>2</code> 字宽存储对象头。在 <code>32</code> 位虚拟机中，<code>1</code> 字宽等于 <code>4</code> 字节，即 <code>32bit</code>。在 <code>64</code> 位虚拟机中，<code>1</code> 字宽等于 <code>8</code> 字节，即 <code>64bit</code>。</p>
-<p><code>Java</code> 对象头的组成结构如下：</p>
-<table>
-<thead>
-<tr>
-<th>长度</th>
-<th>内容</th>
-<th>说明</th>
-</tr>
-</thead>
-<tbody><tr>
-<td><code>32/64bit</code></td>
-<td><code>Mark Word</code></td>
-<td><strong>存储对象的 <code>hashCode</code> 或锁信息</strong></td>
-</tr>
-<tr>
-<td><code>32/64bit</code></td>
-<td><code>Class Metadata Address</code></td>
-<td>存储指向对象类型数据的指针</td>
-</tr>
-<tr>
-<td><code>32/64bit</code></td>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> Map&lt;String, Object&gt; <span class="title function_">getAnnotationAttributes</span><span class="params">(String annotationName, <span class="type">boolean</span> classValuesAsString)</span> &#123;</span><br><span class="line">    <span class="comment">// 获取合并的注解属性</span></span><br><span class="line">    <span class="keyword">return</span> (<span class="built_in">this</span>.annotations.length &gt; <span class="number">0</span> ? AnnotatedElementUtils.getMergedAnnotationAttributes(</span><br><span class="line">            getIntrospectedClass(), annotationName, classValuesAsString, <span class="built_in">this</span>.nestedAnnotationsAsMap) : <span class="literal">null</span>);</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<p>根据注释，<code>getMergedAnnotationAttributes</code> 方法获取所提供元素上方的注解层次结构中指定的 <code>annotationName</code> 的第一个注解，并将该注解的属性与注解层次结构较低级别中的注解中的匹配属性合并。注解层次结构中较低级别的属性会覆盖较高级别中的同名属性，并且完全支持单个注解中或是注解层次结构中的 <code>@AliasFor</code> 语义。与 <code>getAllAnnotationAttributes</code> 方法相反，一旦找到指定 <code>annotationName</code> 的第一个注解，此方法使用的搜索算法将停止搜索注解层次结构。因此，指定的 <code>annotationName</code> 的附加注解将被忽略。</p>
+<blockquote>
+<p>这注释有点太抽象了，理解代码后再来回味吧。</p>
+</blockquote>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">static</span> AnnotationAttributes <span class="title function_">getMergedAnnotationAttributes</span><span class="params">(AnnotatedElement element,</span></span><br><span class="line"><span class="params">        String annotationName, <span class="type">boolean</span> classValuesAsString, <span class="type">boolean</span> nestedAnnotationsAsMap)</span> &#123;</span><br><span class="line">    <span class="comment">// 以 get 语义进行搜索（是指找到即终止搜索？）</span></span><br><span class="line">    <span class="type">AnnotationAttributes</span> <span class="variable">attributes</span> <span class="operator">=</span> searchWithGetSemantics(element, <span class="literal">null</span>, annotationName,</span><br><span class="line">            <span class="keyword">new</span> <span class="title class_">MergedAnnotationAttributesProcessor</span>(classValuesAsString, nestedAnnotationsAsMap));</span><br><span class="line">    <span class="comment">// 后处理注解属性</span></span><br><span class="line">    AnnotationUtils.postProcessAnnotationAttributes(element, attributes, classValuesAsString, nestedAnnotationsAsMap);</span><br><span class="line">    <span class="keyword">return</span> attributes;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<p><code>searchWithGetSemantics</code> 方法有多个重载方法，最终调用的版本如下：</p>
+<ul>
+<li>先获取 <code>element</code> 上的所有注解（包括重复的，不包括继承的），<strong>这意味着可重复注解 <code>@ComponentScan</code> 标注了多个就会有多个实例</strong></li>
+<li>在注解中搜索</li>
+<li>如果没找到，就从继承的注解中继续搜索</li>
+</ul>
+<blockquote>
+<p>本方法是一个会被递归调用的方法，在第一次调用时 <code>element</code> 是配置类，之后就是注解。</p>
+</blockquote>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">private</span> <span class="keyword">static</span> &lt;T&gt; T <span class="title function_">searchWithGetSemantics</span><span class="params">(AnnotatedElement element,</span></span><br><span class="line"><span class="params">        <span class="meta">@Nullable</span> Class&lt;? extends Annotation&gt; annotationType, <span class="meta">@Nullable</span> String annotationName,</span></span><br><span class="line"><span class="params">        <span class="meta">@Nullable</span> Class&lt;? extends Annotation&gt; containerType, Processor&lt;T&gt; processor,</span></span><br><span class="line"><span class="params">        Set&lt;AnnotatedElement&gt; visited, <span class="type">int</span> metaDepth)</span> &#123;</span><br><span class="line">    <span class="comment">// 防止无限递归</span></span><br><span class="line">    <span class="keyword">if</span> (visited.add(element)) &#123;</span><br><span class="line">        <span class="keyword">try</span> &#123;</span><br><span class="line">            <span class="comment">// 获取 element 上的所有注解（包括重复，不包括继承的）</span></span><br><span class="line">            List&lt;Annotation&gt; declaredAnnotations = Arrays.asList(element.getDeclaredAnnotations());</span><br><span class="line">            <span class="comment">// 在获得的注解中搜索</span></span><br><span class="line">            <span class="type">T</span> <span class="variable">result</span> <span class="operator">=</span> searchWithGetSemanticsInAnnotations(element, declaredAnnotations,</span><br><span class="line">                    annotationType, annotationName, containerType, processor, visited, metaDepth);</span><br><span class="line">            <span class="keyword">if</span> (result != <span class="literal">null</span>) &#123;</span><br><span class="line">                <span class="keyword">return</span> result;</span><br><span class="line">            &#125;</span><br><span class="line">            <span class="comment">// 表明在直接声明的注解中没有找到</span></span><br><span class="line">            <span class="comment">// 如果 element 是一个类</span></span><br><span class="line">            <span class="keyword">if</span> (element <span class="keyword">instanceof</span> Class) &#123;</span><br><span class="line">                <span class="comment">// 获取所有的注解（包括重复的和继承的）</span></span><br><span class="line">                List&lt;Annotation&gt; inheritedAnnotations = <span class="keyword">new</span> <span class="title class_">ArrayList</span>&lt;&gt;();</span><br><span class="line">                <span class="keyword">for</span> (Annotation annotation : element.getAnnotations()) &#123;</span><br><span class="line">                    <span class="comment">// 排除已经搜索过的，只留下继承的注解</span></span><br><span class="line">                    <span class="keyword">if</span> (!declaredAnnotations.contains(annotation)) &#123;</span><br><span class="line">                        inheritedAnnotations.add(annotation);</span><br><span class="line">                    &#125;</span><br><span class="line">                &#125;</span><br><span class="line">                <span class="comment">// 继续搜索</span></span><br><span class="line">                result = searchWithGetSemanticsInAnnotations(element, inheritedAnnotations,</span><br><span class="line">                        annotationType, annotationName, containerType, processor, visited, metaDepth);</span><br><span class="line">                <span class="keyword">if</span> (result != <span class="literal">null</span>) &#123;</span><br><span class="line">                    <span class="keyword">return</span> result;</span><br><span class="line">                &#125;</span><br><span class="line">            &#125;</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="keyword">catch</span> (Throwable ex) &#123;</span><br><span class="line">            AnnotationUtils.handleIntrospectionFailure(element, ex);</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">return</span> <span class="literal">null</span>;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<p>遍历注解进行搜索。</p>
+<ul>
+<li>先在注解中搜索，<strong>这意味着如果配置类标注了 <code>@ComponentScan</code>，直接就找到了</strong></li>
+<li>如果没找到再在元注解中搜索，如果配置类只标注了 <code>@SpringBootApplication</code>，就是在这部分找到元注解 <code>@ComponentScan</code></li>
+</ul>
+<blockquote>
+<p>严格意义上说，并不是直接标注的 <code>@ComponentScan</code> 会覆盖 <code>@SpringBootApplication</code> 上间接标注的 <code>@ComponentScan</code>，而是搜索在找到第一个注解后终止没有继续查找。这解答了我们的第一个疑问。</p>
+</blockquote>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">private</span> <span class="keyword">static</span> &lt;T&gt; T <span class="title function_">searchWithGetSemanticsInAnnotations</span><span class="params">(<span class="meta">@Nullable</span> AnnotatedElement element,</span></span><br><span class="line"><span class="params">        List&lt;Annotation&gt; annotations, <span class="meta">@Nullable</span> Class&lt;? extends Annotation&gt; annotationType,</span></span><br><span class="line"><span class="params">        <span class="meta">@Nullable</span> String annotationName, <span class="meta">@Nullable</span> Class&lt;? extends Annotation&gt; containerType,</span></span><br><span class="line"><span class="params">        Processor&lt;T&gt; processor, Set&lt;AnnotatedElement&gt; visited, <span class="type">int</span> metaDepth)</span> &#123;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 遍历注解进行查找，如果同时标注 @SpringBootApplication 和 @ComponentScan，在这部分就会找到 @ComponentScan 就返回了</span></span><br><span class="line">    <span class="keyword">for</span> (Annotation annotation : annotations) &#123;</span><br><span class="line">        <span class="comment">// 获取注解的 Class</span></span><br><span class="line">        Class&lt;? <span class="keyword">extends</span> <span class="title class_">Annotation</span>&gt; currentAnnotationType = annotation.annotationType();</span><br><span class="line">        <span class="comment">// 检测是否属于 Java 语言注解包中（以 java.lang.annotation 开头）的注解，例如 @Documented，是的话跳过</span></span><br><span class="line">        <span class="keyword">if</span> (!AnnotationUtils.isInJavaLangAnnotationPackage(currentAnnotationType)) &#123;</span><br><span class="line">            <span class="comment">// 检测是否满足条件：等于 annotationType（传入 null），或者和目标的名字（@ComponentScan 全限定类名）相同，或者属于总是处理（默认 false）</span></span><br><span class="line">            <span class="keyword">if</span> (currentAnnotationType == annotationType ||</span><br><span class="line">                    currentAnnotationType.getName().equals(annotationName) ||</span><br><span class="line">                    processor.alwaysProcesses()) &#123;</span><br><span class="line">                <span class="comment">// 处理注解获得注解属性</span></span><br><span class="line">                <span class="type">T</span> <span class="variable">result</span> <span class="operator">=</span> processor.process(element, annotation, metaDepth);</span><br><span class="line">                <span class="keyword">if</span> (result != <span class="literal">null</span>) &#123;</span><br><span class="line">                    <span class="comment">// processor.aggregates() 默认返回 false</span></span><br><span class="line">                    <span class="keyword">if</span> (processor.aggregates() &amp;&amp; metaDepth == <span class="number">0</span>) &#123;</span><br><span class="line">                        processor.getAggregatedResults().add(result);</span><br><span class="line">                    &#125;</span><br><span class="line">                    <span class="keyword">else</span> &#123;</span><br><span class="line">                        <span class="comment">// 注意：难道标注多个 @ComponentScan 也只找到一个就返回了？</span></span><br><span class="line">                        <span class="keyword">return</span> result;</span><br><span class="line">                    &#125;</span><br><span class="line">                &#125;</span><br><span class="line">            &#125;</span><br><span class="line">            <span class="comment">// 容器里的可重复注解，因为 containerType 为 null，跳过</span></span><br><span class="line">            <span class="keyword">else</span> <span class="keyword">if</span> (currentAnnotationType == containerType) &#123;</span><br><span class="line">                <span class="keyword">for</span> (Annotation contained : getRawAnnotationsFromContainer(element, annotation)) &#123;</span><br><span class="line">                    <span class="type">T</span> <span class="variable">result</span> <span class="operator">=</span> processor.process(element, contained, metaDepth);</span><br><span class="line">                    <span class="keyword">if</span> (result != <span class="literal">null</span>) &#123;</span><br><span class="line">                        <span class="comment">// No need to post-process since repeatable annotations within a</span></span><br><span class="line">                        <span class="comment">// container cannot be composed annotations.</span></span><br><span class="line">                        processor.getAggregatedResults().add(result);</span><br><span class="line">                    &#125;</span><br><span class="line">                &#125;</span><br><span class="line">            &#125;</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 在元注解中递归的搜索，@SpringBootApplication 中的 @ComponentScan 就是在这找到的</span></span><br><span class="line">    <span class="keyword">for</span> (Annotation annotation : annotations) &#123;</span><br><span class="line">        <span class="comment">// 获取注解的 Class</span></span><br><span class="line">        Class&lt;? <span class="keyword">extends</span> <span class="title class_">Annotation</span>&gt; currentAnnotationType = annotation.annotationType();</span><br><span class="line">        <span class="comment">// 检测是否属于 Java 语言注解包中</span></span><br><span class="line">        <span class="keyword">if</span> (!AnnotationUtils.isInJavaLangAnnotationPackage(currentAnnotationType)) &#123;</span><br><span class="line">            <span class="comment">// 递归到元注解中搜索，深度加 1</span></span><br><span class="line">            <span class="type">T</span> <span class="variable">result</span> <span class="operator">=</span> searchWithGetSemantics(currentAnnotationType, annotationType,</span><br><span class="line">                    annotationName, containerType, processor, visited, metaDepth + <span class="number">1</span>);</span><br><span class="line">            <span class="keyword">if</span> (result != <span class="literal">null</span>) &#123;</span><br><span class="line">                <span class="comment">// 进行后处理，注解层次结构中较低级别的属性会覆盖较高级别中的同名属性就是在这发生的</span></span><br><span class="line">                processor.postProcess(element, annotation, result);</span><br><span class="line">                <span class="keyword">if</span> (processor.aggregates() &amp;&amp; metaDepth == <span class="number">0</span>) &#123;</span><br><span class="line">                    processor.getAggregatedResults().add(result);</span><br><span class="line">                &#125;</span><br><span class="line">                <span class="keyword">else</span> &#123;</span><br><span class="line">                    <span class="keyword">return</span> result;</span><br><span class="line">                &#125;</span><br><span class="line">            &#125;</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">return</span> <span class="literal">null</span>;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<p>处理 <code>@ComponentScan</code> 获得 <code>AnnotationAttributes</code>。</p>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> AnnotationAttributes <span class="title function_">process</span><span class="params">(<span class="meta">@Nullable</span> AnnotatedElement annotatedElement, Annotation annotation, <span class="type">int</span> metaDepth)</span> &#123;</span><br><span class="line">    <span class="keyword">return</span> AnnotationUtils.retrieveAnnotationAttributes(annotatedElement, annotation,</span><br><span class="line">            <span class="built_in">this</span>.classValuesAsString, <span class="built_in">this</span>.nestedAnnotationsAsMap);</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<p>以 <code>AnnotationAttributes</code> 映射的形式检索给定注解的属性。</p>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">static</span> AnnotationAttributes <span class="title function_">retrieveAnnotationAttributes</span><span class="params">(<span class="meta">@Nullable</span> Object annotatedElement, Annotation annotation,</span></span><br><span class="line"><span class="params">        <span class="type">boolean</span> classValuesAsString, <span class="type">boolean</span> nestedAnnotationsAsMap)</span> &#123;</span><br><span class="line"></span><br><span class="line">    Class&lt;? <span class="keyword">extends</span> <span class="title class_">Annotation</span>&gt; annotationType = annotation.annotationType();</span><br><span class="line">    <span class="type">AnnotationAttributes</span> <span class="variable">attributes</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">AnnotationAttributes</span>(annotationType);</span><br><span class="line">    <span class="comment">// 遍历属性方法</span></span><br><span class="line">    <span class="keyword">for</span> (Method method : getAttributeMethods(annotationType)) &#123;</span><br><span class="line">        <span class="keyword">try</span> &#123;</span><br><span class="line">            <span class="comment">// 获取属性值</span></span><br><span class="line">            <span class="type">Object</span> <span class="variable">attributeValue</span> <span class="operator">=</span> method.invoke(annotation);</span><br><span class="line">            <span class="comment">// 获取默认值</span></span><br><span class="line">            <span class="type">Object</span> <span class="variable">defaultValue</span> <span class="operator">=</span> method.getDefaultValue();</span><br><span class="line">            <span class="comment">// 如果默认值不为 null 且和属性值相同</span></span><br><span class="line">            <span class="keyword">if</span> (defaultValue != <span class="literal">null</span> &amp;&amp; ObjectUtils.nullSafeEquals(attributeValue, defaultValue)) &#123;</span><br><span class="line">                attributeValue = <span class="keyword">new</span> <span class="title class_">DefaultValueHolder</span>(defaultValue);</span><br><span class="line">            &#125;</span><br><span class="line">            <span class="comment">// 属性名 -&gt; 属性值</span></span><br><span class="line">            attributes.put(method.getName(),</span><br><span class="line">                    adaptValue(annotatedElement, attributeValue, classValuesAsString, nestedAnnotationsAsMap));</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="keyword">catch</span> (Throwable ex) &#123;</span><br><span class="line">            <span class="keyword">if</span> (ex <span class="keyword">instanceof</span> InvocationTargetException) &#123;</span><br><span class="line">                <span class="type">Throwable</span> <span class="variable">targetException</span> <span class="operator">=</span> ((InvocationTargetException) ex).getTargetException();</span><br><span class="line">                rethrowAnnotationConfigurationException(targetException);</span><br><span class="line">            &#125;</span><br><span class="line">            <span class="keyword">throw</span> <span class="keyword">new</span> <span class="title class_">IllegalStateException</span>(<span class="string">&quot;Could not obtain annotation attribute value for &quot;</span> + method, ex);</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">return</span> attributes;</span><br><span class="line">&#125;</span><br><span class="line"></span><br><span class="line"><span class="comment">// 获取在所提供的 annotationType 中声明的与 Java 对注释属性的要求相匹配的所有方法</span></span><br><span class="line"><span class="keyword">static</span> List&lt;Method&gt; <span class="title function_">getAttributeMethods</span><span class="params">(Class&lt;? extends Annotation&gt; annotationType)</span> &#123;</span><br><span class="line">    <span class="comment">// 先从缓存中获取</span></span><br><span class="line">    List&lt;Method&gt; methods = attributeMethodsCache.get(annotationType);</span><br><span class="line">    <span class="keyword">if</span> (methods != <span class="literal">null</span>) &#123;</span><br><span class="line">        <span class="keyword">return</span> methods;</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="comment">// 遍历方法筛选</span></span><br><span class="line">    methods = <span class="keyword">new</span> <span class="title class_">ArrayList</span>&lt;&gt;();</span><br><span class="line">    <span class="keyword">for</span> (Method method : annotationType.getDeclaredMethods()) &#123;</span><br><span class="line">        <span class="keyword">if</span> (isAttributeMethod(method)) &#123;</span><br><span class="line">            ReflectionUtils.makeAccessible(method);</span><br><span class="line">            methods.add(method);</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="comment">// 存入缓存</span></span><br><span class="line">    attributeMethodsCache.put(annotationType, methods);</span><br><span class="line">    <span class="keyword">return</span> methods;</span><br><span class="line">&#125;</span><br><span class="line"></span><br><span class="line"><span class="comment">// 确定提供的方法是否是注解的属性方法。</span></span><br><span class="line"><span class="keyword">static</span> <span class="type">boolean</span> <span class="title function_">isAttributeMethod</span><span class="params">(<span class="meta">@Nullable</span> Method method)</span> &#123;</span><br><span class="line">    <span class="comment">// 无参数 &amp;&amp; 返回值非 void</span></span><br><span class="line">    <span class="keyword">return</span> (method != <span class="literal">null</span> &amp;&amp; method.getParameterCount() == <span class="number">0</span> &amp;&amp; method.getReturnType() != <span class="keyword">void</span>.class);</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<h3 id="组合注解的属性覆盖"><a href="#组合注解的属性覆盖" class="headerlink" title="组合注解的属性覆盖"></a>组合注解的属性覆盖</h3><p>在获得注解属性后还要进行后处理，使用注解层次结构中较低级别的属性覆盖较高级别中的同名（包括 <code>@AliasFor</code> 指定的）属性。比如使用 <code>@SpringBootApplication</code> 中的 <code>scanBasePackages</code> 的值覆盖 <code>@ComponentScan</code> 中的 <code>basePackages</code> 的值。</p>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title function_">postProcess</span><span class="params">(<span class="meta">@Nullable</span> AnnotatedElement element, Annotation annotation, AnnotationAttributes attributes)</span> &#123;</span><br><span class="line">    annotation = AnnotationUtils.synthesizeAnnotation(annotation, element);</span><br><span class="line">    <span class="comment">// 获取 AnnotationAttributes 的注解类型（@ComponentScan）</span></span><br><span class="line">    Class&lt;? <span class="keyword">extends</span> <span class="title class_">Annotation</span>&gt; targetAnnotationType = attributes.annotationType();</span><br><span class="line"></span><br><span class="line">    <span class="comment">// Track which attribute values have already been replaced so that we can short</span></span><br><span class="line">    <span class="comment">// circuit the search algorithms.</span></span><br><span class="line">    Set&lt;String&gt; valuesAlreadyReplaced = <span class="keyword">new</span> <span class="title class_">HashSet</span>&lt;&gt;();</span><br><span class="line">    <span class="comment">// 获取注解的属性方法（SpringBootApplication）</span></span><br><span class="line">    <span class="keyword">for</span> (Method attributeMethod : AnnotationUtils.getAttributeMethods(annotation.annotationType())) &#123;</span><br><span class="line">        <span class="type">String</span> <span class="variable">attributeName</span> <span class="operator">=</span> attributeMethod.getName();</span><br><span class="line">        <span class="comment">// 获取被覆盖的别名</span></span><br><span class="line">        <span class="type">String</span> <span class="variable">attributeOverrideName</span> <span class="operator">=</span> AnnotationUtils.getAttributeOverrideName(attributeMethod, targetAnnotationType);</span><br><span class="line"></span><br><span class="line">        <span class="comment">// Explicit annotation attribute override declared via @AliasFor</span></span><br><span class="line">        <span class="keyword">if</span> (attributeOverrideName != <span class="literal">null</span>) &#123;</span><br><span class="line">            <span class="comment">// 被覆盖的属性的值是否已经被替换</span></span><br><span class="line">            <span class="keyword">if</span> (valuesAlreadyReplaced.contains(attributeOverrideName)) &#123;</span><br><span class="line">                <span class="keyword">continue</span>;</span><br><span class="line">            &#125;</span><br><span class="line"></span><br><span class="line">            List&lt;String&gt; targetAttributeNames = <span class="keyword">new</span> <span class="title class_">ArrayList</span>&lt;&gt;();</span><br><span class="line">            targetAttributeNames.add(attributeOverrideName);</span><br><span class="line">            valuesAlreadyReplaced.add(attributeOverrideName);</span><br><span class="line"></span><br><span class="line">            <span class="comment">// 确保覆盖目标注解中的所有别名属性。 (SPR-14069)</span></span><br><span class="line">            List&lt;String&gt; aliases = AnnotationUtils.getAttributeAliasMap(targetAnnotationType).get(attributeOverrideName);</span><br><span class="line">            <span class="keyword">if</span> (aliases != <span class="literal">null</span>) &#123;</span><br><span class="line">                <span class="keyword">for</span> (String alias : aliases) &#123;</span><br><span class="line">                    <span class="keyword">if</span> (!valuesAlreadyReplaced.contains(alias)) &#123;</span><br><span class="line">                        targetAttributeNames.add(alias);</span><br><span class="line">                        valuesAlreadyReplaced.add(alias);</span><br><span class="line">                    &#125;</span><br><span class="line">                &#125;</span><br><span class="line">            &#125;</span><br><span class="line"></span><br><span class="line">            overrideAttributes(element, annotation, attributes, attributeName, targetAttributeNames);</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="comment">// Implicit annotation attribute override based on convention</span></span><br><span class="line">        <span class="keyword">else</span> <span class="keyword">if</span> (!AnnotationUtils.VALUE.equals(attributeName) &amp;&amp; attributes.containsKey(attributeName)) &#123;</span><br><span class="line">            overrideAttribute(element, annotation, attributes, attributeName, attributeName);</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br><span class="line"></span><br><span class="line"><span class="comment">// 根据提供的注解属性方法的 @AliasFor，获取被覆盖的属性的名称</span></span><br><span class="line"><span class="keyword">static</span> String <span class="title function_">getAttributeOverrideName</span><span class="params">(Method attribute, <span class="meta">@Nullable</span> Class&lt;? extends Annotation&gt; metaAnnotationType)</span> &#123;</span><br><span class="line">    <span class="comment">// 获取别名描述符</span></span><br><span class="line">    <span class="type">AliasDescriptor</span> <span class="variable">descriptor</span> <span class="operator">=</span> AliasDescriptor.from(attribute);</span><br><span class="line">    <span class="comment">// 从元注解中被覆盖的属性名</span></span><br><span class="line">    <span class="keyword">return</span> (descriptor != <span class="literal">null</span> &amp;&amp; metaAnnotationType != <span class="literal">null</span> ?</span><br><span class="line">            descriptor.getAttributeOverrideName(metaAnnotationType) : <span class="literal">null</span>);</span><br><span class="line">&#125;</span><br><span class="line"></span><br><span class="line"><span class="comment">// 获取在提供的注解类型中通过 @AliasFor 声明的所有属性别名的映射。该映射由属性名称作为键，每个值代表别名属性的名称列表。空返回值意味着注解没有声明任何属性别名。</span></span><br><span class="line"><span class="keyword">static</span> Map&lt;String, List&lt;String&gt;&gt; <span class="title function_">getAttributeAliasMap</span><span class="params">(<span class="meta">@Nullable</span> Class&lt;? extends Annotation&gt; annotationType)</span> &#123;</span><br><span class="line">    <span class="keyword">if</span> (annotationType == <span class="literal">null</span>) &#123;</span><br><span class="line">        <span class="keyword">return</span> Collections.emptyMap();</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="comment">// 从缓存中获取</span></span><br><span class="line">    Map&lt;String, List&lt;String&gt;&gt; map = attributeAliasesCache.get(annotationType);</span><br><span class="line">    <span class="keyword">if</span> (map != <span class="literal">null</span>) &#123;</span><br><span class="line">        <span class="keyword">return</span> map;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    map = <span class="keyword">new</span> <span class="title class_">LinkedHashMap</span>&lt;&gt;();</span><br><span class="line">    <span class="comment">// 遍历属性方法</span></span><br><span class="line">    <span class="keyword">for</span> (Method attribute : getAttributeMethods(annotationType)) &#123;</span><br><span class="line">        <span class="comment">// 获取别名列表</span></span><br><span class="line">        List&lt;String&gt; aliasNames = getAttributeAliasNames(attribute);</span><br><span class="line">        <span class="keyword">if</span> (!aliasNames.isEmpty()) &#123;</span><br><span class="line">            map.put(attribute.getName(), aliasNames);</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="comment">// 存入缓存</span></span><br><span class="line">    attributeAliasesCache.put(annotationType, map);</span><br><span class="line">    <span class="keyword">return</span> map;</span><br><span class="line">&#125;</span><br><span class="line"></span><br><span class="line"><span class="comment">// 获取通过提供的注解属性的 @AliasFor 配置的别名属性的名称列表</span></span><br><span class="line"><span class="keyword">static</span> List&lt;String&gt; <span class="title function_">getAttributeAliasNames</span><span class="params">(Method attribute)</span> &#123;</span><br><span class="line">    <span class="type">AliasDescriptor</span> <span class="variable">descriptor</span> <span class="operator">=</span> AliasDescriptor.from(attribute);</span><br><span class="line">    <span class="keyword">return</span> (descriptor != <span class="literal">null</span> ? descriptor.getAttributeAliasNames() : Collections.&lt;String&gt; emptyList());</span><br><span class="line">&#125;</span><br><span class="line"></span><br><span class="line"><span class="comment">// 覆盖属性</span></span><br><span class="line"><span class="keyword">private</span> <span class="keyword">void</span> <span class="title function_">overrideAttributes</span><span class="params">(<span class="meta">@Nullable</span> AnnotatedElement element, Annotation annotation,</span></span><br><span class="line"><span class="params">        AnnotationAttributes attributes, String sourceAttributeName, List&lt;String&gt; targetAttributeNames)</span> &#123;</span><br><span class="line"></span><br><span class="line">    <span class="type">Object</span> <span class="variable">adaptedValue</span> <span class="operator">=</span> getAdaptedValue(element, annotation, sourceAttributeName);</span><br><span class="line">    <span class="comment">// 遍历目标属性中的所有应被覆盖的属性（本尊+别名）</span></span><br><span class="line">    <span class="keyword">for</span> (String targetAttributeName : targetAttributeNames) &#123;</span><br><span class="line">        attributes.put(targetAttributeName, adaptedValue);</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<p>在代码的注释中我们留下过一个疑问，如果找到了第一个注解就立即返回，那么标注了多个 <code>@ComponentScan</code> 呢？当你 <code>Debug</code> 时，你会发现并没有走出现直接标注了 <code>@ComponentScan</code> 的处理，其实看到反编译后的代码你就知道了，多个 <code>@ComponentScan</code> 被合成了一个 <code>@ComponentScans</code>，甚至此时设置的三个 <code>basePackages</code> 都是生效的。在 <code>JDK 8</code> 引入的重复注解机制，并非一个语言层面上的改动，而是编译器层面的改动。在编译后，多个可重复注解 <code>@ComponentScan</code> 会被合并到一个容器注解 <code>@ComponentScans</code> 中。</p>
+<blockquote>
+<p>因此，“<code>@ComponentScan</code> 的配置会覆盖 <code>@SpringBootApplication</code> 关于包扫描的配置”这句话既对又不对，它在一个常见的个例上表现出的现象是对的，在更普遍的情况中以及本质上是错误的。你也许可以再根据一些情况罗列出类似的“<code>@ComponentScan</code> 使用规则”，但是如果你不明白背后的本质，那么这些只是一些死记硬背的陈述，甚至会带给你错误的认知。</p>
+</blockquote>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="comment">// 标注了两个 `@ComponentScan`，对编译后的字节码进行反编译</span></span><br><span class="line"><span class="meta">@SpringBootApplication(</span></span><br><span class="line"><span class="meta">    scanBasePackages = &#123;&quot;com.example&quot;&#125;</span></span><br><span class="line"><span class="meta">)</span></span><br><span class="line"><span class="meta">@ComponentScans(&#123;@ComponentScan(</span></span><br><span class="line"><span class="meta">    basePackages = &#123;&quot;com.example.demo&quot;&#125;</span></span><br><span class="line"><span class="meta">), @ComponentScan(&#123;&quot;com&quot;&#125;)&#125;)</span></span><br><span class="line"><span class="keyword">public</span> <span class="keyword">class</span> <span class="title class_">DemoApplication</span> &#123;</span><br><span class="line">    <span class="keyword">public</span> <span class="title function_">DemoApplication</span><span class="params">()</span> &#123;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">main</span><span class="params">(String[] args)</span> &#123;</span><br><span class="line">        SpringApplication.run(DemoApplication.class, args);</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<h3 id="注解内的别名属性"><a href="#注解内的别名属性" class="headerlink" title="注解内的别名属性"></a>注解内的别名属性</h3><p><code>postProcess</code> 方法完成了组合注解的属性覆盖，可是对于 <code>@ComponentScan</code> 注解而言，它没有被 <code>postProcess</code> 方法处理，它又是如何做到设置 <code>basePackages</code> 等于设置 <code>value</code> 呢？其实这发生在后处理注解属性方法中，该方法会对注解中标注了 <code>@AliasFor</code> 的属性强制执行别名语义。通俗地讲，就是<strong>统一</strong>或<strong>校验</strong>互为别名的属性值，要么只设置了其中一个属性的值，其他别名属性会被赋值为相同的值，要么设置为相同的值，否则会报错。</p>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">static</span> AnnotationAttributes <span class="title function_">getMergedAnnotationAttributes</span><span class="params">(AnnotatedElement element,</span></span><br><span class="line"><span class="params">        String annotationName, <span class="type">boolean</span> classValuesAsString, <span class="type">boolean</span> nestedAnnotationsAsMap)</span> &#123;</span><br><span class="line">    <span class="comment">// 以 get 语义进行搜索（是指找到即终止搜索？）</span></span><br><span class="line">    <span class="type">AnnotationAttributes</span> <span class="variable">attributes</span> <span class="operator">=</span> searchWithGetSemantics(element, <span class="literal">null</span>, annotationName,</span><br><span class="line">            <span class="keyword">new</span> <span class="title class_">MergedAnnotationAttributesProcessor</span>(classValuesAsString, nestedAnnotationsAsMap));</span><br><span class="line">    <span class="comment">// 后处理注解属性</span></span><br><span class="line">    AnnotationUtils.postProcessAnnotationAttributes(element, attributes, classValuesAsString, nestedAnnotationsAsMap);</span><br><span class="line">    <span class="keyword">return</span> attributes;</span><br><span class="line">&#125;</span><br><span class="line"></span><br><span class="line"><span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">postProcessAnnotationAttributes</span><span class="params">(<span class="meta">@Nullable</span> Object annotatedElement,</span></span><br><span class="line"><span class="params">        <span class="meta">@Nullable</span> AnnotationAttributes attributes, <span class="type">boolean</span> classValuesAsString, <span class="type">boolean</span> nestedAnnotationsAsMap)</span> &#123;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">if</span> (attributes == <span class="literal">null</span>) &#123;</span><br><span class="line">        <span class="keyword">return</span>;</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="comment">// 获取 AnnotationAttributes 的注解类型（@ComponentScan）</span></span><br><span class="line">    Class&lt;? <span class="keyword">extends</span> <span class="title class_">Annotation</span>&gt; annotationType = attributes.annotationType();</span><br><span class="line"></span><br><span class="line">    <span class="comment">// Track which attribute values have already been replaced so that we can short</span></span><br><span class="line">    <span class="comment">// circuit the search algorithms.</span></span><br><span class="line">    Set&lt;String&gt; valuesAlreadyReplaced = <span class="keyword">new</span> <span class="title class_">HashSet</span>&lt;&gt;();</span><br><span class="line"></span><br><span class="line">    <span class="keyword">if</span> (!attributes.validated) &#123;</span><br><span class="line">        <span class="comment">// 校验 @AliasFor 配置</span></span><br><span class="line">        <span class="comment">// 获取别名映射</span></span><br><span class="line">        Map&lt;String, List&lt;String&gt;&gt; aliasMap = getAttributeAliasMap(annotationType);</span><br><span class="line">        <span class="comment">// 遍历</span></span><br><span class="line">        <span class="keyword">for</span> (String attributeName : aliasMap.keySet()) &#123;</span><br><span class="line">            <span class="comment">// 跳过已处理的</span></span><br><span class="line">            <span class="keyword">if</span> (valuesAlreadyReplaced.contains(attributeName)) &#123;</span><br><span class="line">                <span class="keyword">continue</span>;</span><br><span class="line">            &#125;</span><br><span class="line">            <span class="type">Object</span> <span class="variable">value</span> <span class="operator">=</span> attributes.get(attributeName);</span><br><span class="line">            <span class="comment">// 属性是否已有值</span></span><br><span class="line">            <span class="type">boolean</span> <span class="variable">valuePresent</span> <span class="operator">=</span> (value != <span class="literal">null</span> &amp;&amp; !(value <span class="keyword">instanceof</span> DefaultValueHolder));</span><br><span class="line">            <span class="comment">// 遍历属性的别名列表</span></span><br><span class="line">            <span class="keyword">for</span> (String aliasedAttributeName : aliasMap.get(attributeName)) &#123;</span><br><span class="line">                <span class="comment">// 跳过已处理的</span></span><br><span class="line">                <span class="keyword">if</span> (valuesAlreadyReplaced.contains(aliasedAttributeName)) &#123;</span><br><span class="line">                    <span class="keyword">continue</span>;</span><br><span class="line">                &#125;</span><br><span class="line">                <span class="comment">// 获取别名属性的值</span></span><br><span class="line">                <span class="type">Object</span> <span class="variable">aliasedValue</span> <span class="operator">=</span> attributes.get(aliasedAttributeName);</span><br><span class="line">                <span class="comment">// 别名属性是否已有值</span></span><br><span class="line">                <span class="type">boolean</span> <span class="variable">aliasPresent</span> <span class="operator">=</span> (aliasedValue != <span class="literal">null</span> &amp;&amp; !(aliasedValue <span class="keyword">instanceof</span> DefaultValueHolder));</span><br><span class="line"></span><br><span class="line">                <span class="comment">// Something to validate or replace with an alias?</span></span><br><span class="line">                <span class="keyword">if</span> (valuePresent || aliasPresent) &#123;</span><br><span class="line">                    <span class="comment">// 如果属性已有值且别名属性也有值，校验是否相等</span></span><br><span class="line">                    <span class="keyword">if</span> (valuePresent &amp;&amp; aliasPresent) &#123;</span><br><span class="line">                        <span class="comment">// Since annotation attributes can be arrays, we must use ObjectUtils.nullSafeEquals().</span></span><br><span class="line">                        <span class="keyword">if</span> (!ObjectUtils.nullSafeEquals(value, aliasedValue)) &#123;</span><br><span class="line">                            <span class="type">String</span> <span class="variable">elementAsString</span> <span class="operator">=</span></span><br><span class="line">                                    (annotatedElement != <span class="literal">null</span> ? annotatedElement.toString() : <span class="string">&quot;unknown element&quot;</span>);</span><br><span class="line">                            <span class="keyword">throw</span> <span class="keyword">new</span> <span class="title class_">AnnotationConfigurationException</span>(String.format(</span><br><span class="line">                                    <span class="string">&quot;In AnnotationAttributes for annotation [%s] declared on %s, &quot;</span> +</span><br><span class="line">                                    <span class="string">&quot;attribute &#x27;%s&#x27; and its alias &#x27;%s&#x27; are declared with values of [%s] and [%s], &quot;</span> +</span><br><span class="line">                                    <span class="string">&quot;but only one is permitted.&quot;</span>, attributes.displayName, elementAsString,</span><br><span class="line">                                    attributeName, aliasedAttributeName, ObjectUtils.nullSafeToString(value),</span><br><span class="line">                                    ObjectUtils.nullSafeToString(aliasedValue)));</span><br><span class="line">                        &#125;</span><br><span class="line">                    &#125;</span><br><span class="line">                    <span class="keyword">else</span> <span class="keyword">if</span> (aliasPresent) &#123;</span><br><span class="line">                        <span class="comment">// 复制别名属性的值给属性</span></span><br><span class="line">                        attributes.put(attributeName,</span><br><span class="line">                                adaptValue(annotatedElement, aliasedValue, classValuesAsString, nestedAnnotationsAsMap));</span><br><span class="line">                        valuesAlreadyReplaced.add(attributeName);</span><br><span class="line">                    &#125;</span><br><span class="line">                    <span class="keyword">else</span> &#123;</span><br><span class="line">                        <span class="comment">// 复制属性的值给别名属性</span></span><br><span class="line">                        attributes.put(aliasedAttributeName,</span><br><span class="line">                                adaptValue(annotatedElement, value, classValuesAsString, nestedAnnotationsAsMap));</span><br><span class="line">                        valuesAlreadyReplaced.add(aliasedAttributeName);</span><br><span class="line">                    &#125;</span><br><span class="line">                &#125;</span><br><span class="line">            &#125;</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="comment">// 校验完毕</span></span><br><span class="line">        attributes.validated = <span class="literal">true</span>;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 将 `value` 从 `DefaultValueHolder` 替换为原始的 `value`</span></span><br><span class="line">    <span class="keyword">for</span> (String attributeName : attributes.keySet()) &#123;</span><br><span class="line">        <span class="keyword">if</span> (valuesAlreadyReplaced.contains(attributeName)) &#123;</span><br><span class="line">            <span class="keyword">continue</span>;</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="type">Object</span> <span class="variable">value</span> <span class="operator">=</span> attributes.get(attributeName);</span><br><span class="line">        <span class="keyword">if</span> (value <span class="keyword">instanceof</span> DefaultValueHolder) &#123;</span><br><span class="line">            value = ((DefaultValueHolder) value).defaultValue;</span><br><span class="line">            attributes.put(attributeName,</span><br><span class="line">                    adaptValue(annotatedElement, value, classValuesAsString, nestedAnnotationsAsMap));</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<h2 id="总结"><a href="#总结" class="headerlink" title="总结"></a>总结</h2><blockquote>
+<p>又是一篇在写之前自认心里有数，以为可以很快总结完，却不知不觉写了很久，也收获了很多的文章。在刚开始，我只是想接续分析 <code>@Configuration</code> 的思路补充关于 <code>@ComponentScan</code> 的内容，但是渐渐地我又想要回应心里的疑问，<code>@ComponentScan</code> 和 <code>@SpringBootApplication</code> 一起使用的问题的本质原因是什么？<code>Spring</code> 框架真的很好用，好用到你不用太关心背后的原理，好用到你有时候用一个本质上不太正确的结论“走遍天下却几乎不会遇到问题”。说实话，研究完也有点索然无味，尤其是花了这么多时间看自己很讨厌的关于解析的代码，只能说解开了一个卡点也算疏通了一口气，但是时间成本好大啊，得多看点能“面试”的技术啊！！！</p>
+</blockquote>
+<p>综上分析，<code>@SpringBootApplication</code> 的包扫描功能本质上还是 <code>@ComponentScan</code> 提供的，但是和常见的嵌套注解不同，检索 <code>@ComponentScan</code> 有一套独特的算法，导致 <code>@SpringBootApplication</code> 和 <code>@ComponentScan</code> 并非简单的叠加效果。</p>
+<ul>
+<li><code>Spring</code> 会先获取 <code>@ComponentScan</code> 的注解属性再获取 <code>@ComponentScans</code> 的注解属性</li>
+<li>以 <code>@ComponentScan</code> 为例，只获取给定配置类上的注解层次结构中的<strong>第一个</strong> <code>@ComponentScan</code></li>
+<li>先从直接标注的注解开始，再递归地搜索元注解，这一点决定了 <code>@ComponentScan</code> 优先级高于 <code>@SpringBootApplication</code></li>
+<li>使用注解层次结构中较低级别的属性覆盖较高级别的同名（支持 <code>@AliasFor</code>）属性，这一点决定了 <code>@SpringBootApplication</code> 可以设置扫描路径</li>
+<li>多个 <code>@ComponentScan</code> 在编译后隐式生成 <code>@ComponentScans</code>，这一点决定多个 <code>@ComponentScan</code> 彼此之间以及和 <code>@SpringBootApplication</code> 互不冲突</li>
+</ul>
+]]></content>
+      <tags>
+        <tag>java</tag>
+        <tag>spring</tag>
+        <tag>spring boot</tag>
+      </tags>
+  </entry>
+  <entry>
+    <title>synchronized 锁机制的分析和验证</title>
+    <url>/2023/12/19/analysis-and-verification-of-the-synchronized-lock-mechanism/</url>
+    <content><![CDATA[<p>本文详细介绍了 <code>Java</code> 中 <code>synchronized</code> 锁的机制、存储结构、优化措施以及升级过程，并通过 <code>jol-core</code> 演示 <code>Mark Word</code> 的变化来验证锁升级的多个 <code>case</code>。</p>
+<span id="more"></span>
+
+<blockquote>
+<p>待完善</p>
+</blockquote>
+<p>利用 <code>synchronized</code> 实现同步的基础：<code>Java</code> 中的每一个对象都可以作为锁。具体表现为以下 <code>3</code> 种形式。</p>
+<ul>
+<li>对于普通同步方法，锁是当前实例对象。</li>
+<li>对于静态同步方法，锁是当前类的 <code>Class</code> 对象。</li>
+<li>对于同步方法块，锁是 <code>synchronized</code> 括号里配置的对象。</li>
+</ul>
+<p>当一个线程试图访问同步代码块时，它首先必须得到锁，退出或抛出异常时必须释放锁。</p>
+<ul>
+<li>在 <code>JVM</code> 层面，<code>synchronized</code> 锁是基于进入和退出 <code>Monitor</code> 来实现的，每一个对象都有一个 <code>Monitor</code> 与之相关联。</li>
+<li>在字节码层面，同步方法块是使用 <code>monitorenter</code> 和 <code>monitorexit</code> 指令实现的，前者在编译后插入到同步方法块的开始位置，后者插入到同步方法块的结束位置和异常位置。</li>
+</ul>
+<h2 id="存储结构"><a href="#存储结构" class="headerlink" title="存储结构"></a>存储结构</h2><blockquote>
+<p>锁存在哪里呢？锁里面又会存储什么信息呢？</p>
+</blockquote>
+<h3 id="对象头"><a href="#对象头" class="headerlink" title="对象头"></a>对象头</h3><p><code>synchronized</code> 用的锁是存在 <code>Java</code> 对象头（<code>object header</code>）里的。如果对象是数组类型，则虚拟机用 <code>3</code> 字宽（<code>Word</code>）存储对象头，如果对象是非数组类型，则用 <code>2</code> 字宽存储对象头。在 <code>32</code> 位虚拟机中，<code>1</code> 字宽等于 <code>4</code> 字节，即 <code>32bit</code>。在 <code>64</code> 位虚拟机中，<code>1</code> 字宽等于 <code>8</code> 字节，即 <code>64bit</code>。</p>
+<p><code>Java</code> 对象头的组成结构如下：</p>
+<table>
+<thead>
+<tr>
+<th>长度</th>
+<th>内容</th>
+<th>说明</th>
+</tr>
+</thead>
+<tbody><tr>
+<td><code>32/64bit</code></td>
+<td><code>Mark Word</code></td>
+<td><strong>存储对象的 <code>hashCode</code> 或锁信息</strong></td>
+</tr>
+<tr>
+<td><code>32/64bit</code></td>
+<td><code>Class Metadata Address</code></td>
+<td>存储指向对象类型数据的指针</td>
+</tr>
+<tr>
+<td><code>32/64bit</code></td>
 <td><code>Array length</code></td>
 <td>数组的长度（如果当前对象是数组）</td>
 </tr>
@@ -5141,587 +5013,349 @@
 <p>偏向锁在 <code>Java 6</code> 之后是默认开启的，可以通过 <code>JVM</code> 参数 <code>-XX:-UseBiasedLocking</code> 关闭偏向锁。尽管偏向锁是默认开启的，但是它在应用程序启动几秒钟之后才激活，延迟时间可以通过 <code>JVM</code> 参数 <code>-XX:BiasedLockingStartupDelay</code> 设置，默认情况下是 <code>4000ms</code>。</p>
 <h4 id="测试偏向锁配置"><a href="#测试偏向锁配置" class="headerlink" title="测试偏向锁配置"></a>测试偏向锁配置</h4><h5 id="延迟偏向"><a href="#延迟偏向" class="headerlink" title="延迟偏向"></a>延迟偏向</h5><p>通过以下示例测试并验证延迟偏向。</p>
 <figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">main</span><span class="params">(String[] args)</span> <span class="keyword">throws</span> IOException, InterruptedException &#123;</span><br><span class="line">    log.info(<span class="string">&quot;测试：偏向锁是延迟激活的&quot;</span>);</span><br><span class="line"></span><br><span class="line">    <span class="type">Object</span> <span class="variable">lock</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">Object</span>();</span><br><span class="line">    log.info(<span class="string">&quot;Mark Word 初始为 =====&gt; 无锁状态（非可偏向的）&quot;</span>);</span><br><span class="line">    log.info(ClassLayout.parseInstance(lock).toPrintable());</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 默认情况下偏向延迟的设置为 -XX:BiasedLockingStartupDelay=4000</span></span><br><span class="line">    log.info(<span class="string">&quot;sleep 4000ms，等待偏向锁激活&quot;</span>);</span><br><span class="line">    TimeUnit.MILLISECONDS.sleep(<span class="number">4000</span>);</span><br><span class="line"></span><br><span class="line">    log.info(<span class="string">&quot;偏向锁激活之后，新创建的对象的对象头的 Mark Word 是 =====&gt; 匿名偏向锁&quot;</span>);</span><br><span class="line">    <span class="type">Object</span> <span class="variable">biasedLock</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">Object</span>();</span><br><span class="line">    log.info(ClassLayout.parseInstance(biasedLock).toPrintable());</span><br><span class="line"></span><br><span class="line">    log.info(<span class="string">&quot;偏向锁激活之前创建的对象的对象头的 Mark Word 仍然是 =====&gt; 无锁状态&quot;</span>);</span><br><span class="line">    log.info(ClassLayout.parseInstance(lock).toPrintable());</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
-
-<p>测试结果如下：</p>
-<figure class="highlight text"><table><tr><td class="code"><pre><span class="line">OFF  SZ   TYPE DESCRIPTION               VALUE</span><br><span class="line">  0   8        (object header: mark)     0x0000000000000001 (non-biasable; age: 0)</span><br><span class="line"></span><br><span class="line">  0   8        (object header: mark)     0x0000000000000005 (biasable; age: 0)</span><br><span class="line"></span><br><span class="line">  0   8        (object header: mark)     0x0000000000000001 (non-biasable; age: 0)</span><br></pre></td></tr></table></figure>
-
-<ul>
-<li><code>JVM</code> 启动后，<strong>偏向锁尚未激活前</strong>，创建的对象的 <code>Mark Word</code> 的末尾 <code>3</code> 位为 <code>0|01</code>，<code>non-biasable</code>，表示无锁状态（非可偏向的）。</li>
-<li>在 <code>4000</code> 毫秒后，<strong>新创建</strong>的对象的 <code>Mark Word</code> 的末尾 <code>3</code> 位为 <code>1|01</code>，<code>biasable</code>，表示匿名偏向锁（可偏向的）。</li>
-<li><strong>偏向锁尚未激活前</strong>创建的对象的对象头的 <code>Mark Word</code> 的末尾 <code>3</code> 位<strong>仍然</strong>是 <code>0|01</code>。</li>
-</ul>
-<blockquote>
-<p>在虚拟机启动后，偏向锁激活前，创建的对象的锁标记位为 <code>1|01</code>，此时记录线程 <code>ID</code> 的 <code>bit</code> 全是 <code>0</code>（代表指向 <code>null</code>），没有偏向任何一个线程，该状态称之为匿名偏向锁。</p>
-</blockquote>
-<h5 id="关闭偏向延迟"><a href="#关闭偏向延迟" class="headerlink" title="关闭偏向延迟"></a>关闭偏向延迟</h5><p>通过以下示例测试关闭偏向延迟：</p>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="comment">// JVM 参数设置为 -XX:BiasedLockingStartupDelay=0</span></span><br><span class="line"><span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">main</span><span class="params">(String[] args)</span> <span class="keyword">throws</span> IOException, InterruptedException &#123;</span><br><span class="line">    log.info(<span class="string">&quot;测试：关闭偏向锁的延迟偏向&quot;</span>);</span><br><span class="line"></span><br><span class="line">    <span class="type">Object</span> <span class="variable">lock</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">Object</span>();</span><br><span class="line">    log.info(<span class="string">&quot;在虚拟机一启动，新创建的对象的对象头的 Mark Word 就是 =====&gt; 匿名偏向锁&quot;</span>);</span><br><span class="line">    log.info(ClassLayout.parseInstance(lock).toPrintable());</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
-
-<h5 id="关闭偏向锁"><a href="#关闭偏向锁" class="headerlink" title="关闭偏向锁"></a>关闭偏向锁</h5><p>通过以下示例测试关闭偏向锁：</p>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="comment">// JVM 参数设置为 -XX:-UseBiasedLocking</span></span><br><span class="line"><span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">main</span><span class="params">(String[] args)</span> <span class="keyword">throws</span> InterruptedException &#123;</span><br><span class="line">    log.info(<span class="string">&quot;测试：关闭偏向锁&quot;</span>);</span><br><span class="line"></span><br><span class="line">    <span class="type">Object</span> <span class="variable">lock</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">Object</span>();</span><br><span class="line">    log.info(<span class="string">&quot;Mark Word 初始为 =====&gt; 无锁状态（非可偏向的）&quot;</span>);</span><br><span class="line">    log.info(ClassLayout.parseInstance(lock).toPrintable());</span><br><span class="line"></span><br><span class="line">    log.info(<span class="string">&quot;sleep 4000ms&quot;</span>);</span><br><span class="line">    TimeUnit.MILLISECONDS.sleep(<span class="number">4000</span>);</span><br><span class="line"></span><br><span class="line">    log.info(<span class="string">&quot;即使过了偏向延迟时间，创建的对象的对象头的 Mark Word 仍然是 =====&gt; 无锁状态（非可偏向的）&quot;</span>);</span><br><span class="line">    log.info(ClassLayout.parseInstance(lock).toPrintable());</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
-
-<p>《Java 并发编程的艺术》中写的是 <code>-XX:-UseBiasedLocking=false</code>，测试中报错：</p>
-<figure class="highlight text"><table><tr><td class="code"><pre><span class="line">Error: Could not create the Java Virtual Machine.</span><br><span class="line">Error: A fatal exception has occurred. Program will exit.</span><br><span class="line">Improperly specified VM option &#x27;UseBiasedLocking=false&#x27;</span><br></pre></td></tr></table></figure>
-
-<p>另外书中说“在关闭偏向锁后程序默认会进入轻量级锁状态”，个人认为可能会让人产生误解，默认在未获取锁时为无锁状态，获取锁将变为轻量级锁状态。</p>
-<h4 id="偏向锁加锁"><a href="#偏向锁加锁" class="headerlink" title="偏向锁加锁"></a>偏向锁加锁</h4><p>当一个线程访问同步块时，先测试 <code>Mark Word</code> 里是否存储着当前线程 <code>ID</code>：</p>
-<ul>
-<li>如果否，则再测试 <code>Mark Word</code> 中偏向锁的标识是否设置成 <code>1</code><ul>
-<li>如果为 <code>0</code>，则说明不是偏向锁状态 &#x3D;&#x3D;&#x3D;&#x3D;&#x3D;&gt; <em>获取偏向锁失败后续处理一</em></li>
-<li>如果为 <code>1</code>，则说明是偏向锁状态，<strong>通过 <code>CAS</code> 操作设置偏向锁</strong><ul>
-<li>如果成功，说明获得偏向锁</li>
-<li>如果失败，说明发生竞争 &#x3D;&#x3D;&#x3D;&#x3D;&#x3D;&gt; <em>获取偏向锁失败后续处理二</em></li>
-</ul>
-</li>
-</ul>
-</li>
-<li>如果是，则说明当前线程就是之前获得偏向锁的线程，此刻再次获得锁</li>
-</ul>
-<blockquote>
-<p>在<strong>通过 <code>CAS</code> 操作设置偏向锁</strong>中，<code>Compare</code> 操作是“测试 <code>Mark Word</code> 存储线程 <code>ID</code> 的 <code>bit</code> 是否全部为 <code>0</code>，代表偏向的线程 <code>ID</code> 为 <code>null</code>”，<code>Swap</code> 操作是将当前线程 <code>ID</code> 设置到 <code>Mark Word</code> 的相应位置。</p>
-</blockquote>
-<p>补充思考：</p>
-<ul>
-<li>“通过 <code>CAS</code> 操作将当前线程 <code>ID</code> 设置到 <code>Mark Word</code>”在偏向锁状态下是有且仅有一次的“偏向”动作。（此观点存疑，在《Java 并发编程的艺术》一书中有“重新偏向于其他线程”这样的描述，但是关于竞争偏向锁部分的原理难以理解。个人在测试中，不论是持有偏向锁的线程仍存活但已离开同步块，还是已死亡，后续线程都无法再获取到偏向锁，唯一一种不同线程获取到同一个偏向锁的情况是两个线程可以复用同一个局部变量表槽位，它们的 <code>tid</code> 相同，这代表着本质上 <code>Mark Word</code> 并无变化）</li>
-<li>当获得偏向锁的线程离开同步块时，没有“解锁操作”，<code>Mark Word</code> 维持不变。个人也不知道如何更准确地描述这个现象，从 <code>synchronized</code> 的语义来说，进出同步块代表着获取锁和释放锁；但是从偏向锁的实现来说，即便离开同步方法块，它仍然偏向原先获得锁的线程，甚至在讨论偏向锁发生竞争时，书中提到“检查持有偏向锁的线程是否存活”。个人更倾向于使用“撤销锁”一词描述偏向锁面临竞争时的处理，使用“释放锁”描述线程离开同步块时的处理。</li>
-<li>当获得偏向锁的线程再次访问同步块时，简单测试 <code>Mark Word</code> 里存储着当前线程 <code>ID</code>，如果成功即可进入同步块。</li>
-<li>计算过 <code>hashCode</code> 后偏向锁状态会变为其他状态，比如无锁状态，或者升级为轻量级锁甚至重量级锁，这符合 <code>CAS</code> 操作的判断条件。</li>
-</ul>
-<h4 id="偏向锁撤销"><a href="#偏向锁撤销" class="headerlink" title="偏向锁撤销"></a>偏向锁撤销</h4><p>偏向锁使用了一种等到竞争出现才撤销的机制，当获得偏向锁的线程离开同步块时，并没有“解锁操作”，<code>Mark Word</code> 将维持不变。当竞争出现时，从现象上说，如果持有偏向锁的线程已经离开同步块，则锁升级为轻量级锁；如果持有锁的线程尚未离开同步块，则锁直接升级为重量级锁。</p>
-<blockquote>
-<p>关于偏向锁的撤销，其原理晦涩难懂，个人仍有很多疑问：锁记录中存储偏向的线程 <code>ID</code> 的作用，检查持有偏向锁的线程是否存活的作用不符合测试结果，重新偏向于其他线程的复现条件。因为理解有限，不多赘述。</p>
-</blockquote>
-<h4 id="测试偏向锁升级"><a href="#测试偏向锁升级" class="headerlink" title="测试偏向锁升级"></a>测试偏向锁升级</h4><h5 id="匿名偏向锁-偏向锁"><a href="#匿名偏向锁-偏向锁" class="headerlink" title="匿名偏向锁-&gt;偏向锁"></a>匿名偏向锁-&gt;偏向锁</h5><blockquote>
-<p>在一个匿名偏向锁状态的对象第一次被作为锁获取时，<code>Mark Word</code> 就会从匿名偏向锁变成偏向锁，并且再也不会变回到匿名偏向锁。</p>
-</blockquote>
-<p>测试在匿名偏向锁状态下获取锁将变成偏向锁状态：</p>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">main</span><span class="params">(String[] args)</span> <span class="keyword">throws</span> IOException, InterruptedException &#123;</span><br><span class="line">    log.info(<span class="string">&quot;偏向锁基础测试：匿名偏向锁 -&gt; 偏向锁&quot;</span>);</span><br><span class="line"></span><br><span class="line">    log.info(<span class="string">&quot;sleep 4000ms，等待偏向锁激活&quot;</span>);</span><br><span class="line">    TimeUnit.MILLISECONDS.sleep(<span class="number">4000</span>);</span><br><span class="line"></span><br><span class="line">    <span class="type">Object</span> <span class="variable">lock</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">Object</span>();</span><br><span class="line">    log.info(<span class="string">&quot;Mark Word 初始为 =====&gt; 匿名偏向锁&quot;</span>);</span><br><span class="line">    log.info(ClassLayout.parseInstance(lock).toPrintable());</span><br><span class="line"></span><br><span class="line">    <span class="keyword">synchronized</span> (lock) &#123;</span><br><span class="line">        log.info(<span class="string">&quot;&#123;&#125; 获取锁 =====&gt; 偏向锁&quot;</span>, Thread.currentThread().getName());</span><br><span class="line">        log.info(ClassLayout.parseInstance(lock).toPrintable());</span><br><span class="line"></span><br><span class="line">        log.info(<span class="string">&quot;暂停，输入任意字符回车继续，可以使用 jstack 查看线程 tid 和 Mark Word 进行对比&quot;</span>);</span><br><span class="line">        scanner.next();</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    log.info(<span class="string">&quot;偏向锁等到竞争出现才释放锁，因此离开同步方法块后，Mark Word 仍然不变&quot;</span>);</span><br><span class="line">    log.info(ClassLayout.parseInstance(lock).toPrintable());</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
-
-<p>测试结果如下：</p>
-<figure class="highlight text"><table><tr><td class="code"><pre><span class="line">2023-12-21 00:34:39 - 偏向锁基础测试：匿名偏向锁 -&gt; 偏向锁</span><br><span class="line">2023-12-21 00:34:39 - sleep 4000ms，等待偏向锁激活</span><br><span class="line">2023-12-21 00:34:43 - Mark Word 初始为 =====&gt; 匿名偏向锁</span><br><span class="line">2023-12-21 00:34:45 - java.lang.Object object internals:</span><br><span class="line">OFF  SZ   TYPE DESCRIPTION               VALUE</span><br><span class="line">  0   8        (object header: mark)     0x0000000000000005 (biasable; age: 0)</span><br><span class="line">  8   4        (object header: class)    0xf80001e5</span><br><span class="line"> 12   4        (object alignment gap)    </span><br><span class="line">Instance size: 16 bytes</span><br><span class="line">Space losses: 0 bytes internal + 4 bytes external = 4 bytes total</span><br><span class="line"></span><br><span class="line">2023-12-21 00:34:45 - main 获取锁 =====&gt; 偏向锁</span><br><span class="line">2023-12-21 00:34:45 - java.lang.Object object internals:</span><br><span class="line">OFF  SZ   TYPE DESCRIPTION               VALUE</span><br><span class="line">  0   8        (object header: mark)     0x0000028761af3005 (biased: 0x00000000a1d86bcc; epoch: 0; age: 0)</span><br><span class="line">  8   4        (object header: class)    0xf80001e5</span><br><span class="line"> 12   4        (object alignment gap)    </span><br><span class="line">Instance size: 16 bytes</span><br><span class="line">Space losses: 0 bytes internal + 4 bytes external = 4 bytes total</span><br><span class="line"></span><br><span class="line">2023-12-21 00:34:45 - 暂停，输入任意字符回车继续，可以使用 jstack 查看线程 tid 和 Mark Word 进行对比</span><br><span class="line">2023-12-21 00:34:55 - 偏向锁等到竞争出现才释放锁，因此离开同步方法块后，Mark Word 仍然不变</span><br><span class="line">2023-12-21 00:34:55 - java.lang.Object object internals:</span><br><span class="line">OFF  SZ   TYPE DESCRIPTION               VALUE</span><br><span class="line">  0   8        (object header: mark)     0x0000028761af3005 (biased: 0x00000000a1d86bcc; epoch: 0; age: 0)</span><br><span class="line">  8   4        (object header: class)    0xf80001e5</span><br><span class="line"> 12   4        (object alignment gap)    </span><br><span class="line">Instance size: 16 bytes</span><br><span class="line">Space losses: 0 bytes internal + 4 bytes external = 4 bytes total</span><br></pre></td></tr></table></figure>
-
-<p>通过 <code>jstack</code> 获取线程 <code>tid</code>（以 <code>Windows</code> 为例）：</p>
-<figure class="highlight shell"><table><tr><td class="code"><pre><span class="line">jps | findstr &quot;BiasedLockingBaseTest&quot; | ForEach-Object &#123; jstack $_.Split()[0]&#125; | findstr &quot;main&quot;</span><br><span class="line">&quot;main&quot; #1 prio=5 os_prio=0 tid=0x0000028761af3000 nid=0x8668 waiting on condition [0x000000ff7b8ff000]</span><br><span class="line">        at com.moralok.concurrency.ch2.BiasedLockingBaseTest.main(BiasedLockingBaseTest.java:27)</span><br></pre></td></tr></table></figure>
-
-<p>关注 <code>Mark Word</code> 并转换为二进制表达：</p>
-<table>
-<thead>
-<tr>
-<th></th>
-<th>二进制表达</th>
-</tr>
-</thead>
-<tbody><tr>
-<td>匿名偏向锁 <code>Mark Word</code></td>
-<td>00000000000000000000000000000000000000000101</td>
-</tr>
-<tr>
-<td>偏向锁状态 <code>Mark Word</code></td>
-<td>00101000011101100001101011110011000000000101</td>
-</tr>
-<tr>
-<td><code>biased</code></td>
-<td>00000000000010100001110110000110101111001100</td>
-</tr>
-<tr>
-<td><code>main</code> 线程 <code>tid</code></td>
-<td>00101000011101100001101011110011000000000000</td>
-</tr>
-</tbody></table>
-<ul>
-<li><strong>注意</strong>：存储的所谓“线程 <code>ID</code>”并非平时所说的线程 <code>ID</code>，该值左移可以得到 <code>jstack</code> 的返回结果中的 <code>tid</code>，<code>jol-core</code> 打印了一个名为 <code>biased</code> 的值与之相同</li>
-<li>在离开同步方法块后，<code>Mark Word</code> 不变</li>
-</ul>
-<h5 id="偏向锁-轻量级锁"><a href="#偏向锁-轻量级锁" class="headerlink" title="偏向锁-&gt;轻量级锁"></a>偏向锁-&gt;轻量级锁</h5><p>测试当拥有偏向锁的线程已经离开同步块，其他线程尝试获取偏向锁（弱竞争），锁将升级为轻量级锁。</p>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">main</span><span class="params">(String[] args)</span> <span class="keyword">throws</span> InterruptedException &#123;</span><br><span class="line">    <span class="type">Scanner</span> <span class="variable">scanner</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">Scanner</span>(System.in);</span><br><span class="line">    log.info(<span class="string">&quot;测试：当持有偏向锁的线程已经离开同步块，其他线程尝试获取偏向锁时，将获得轻量级锁&quot;</span>);</span><br><span class="line"></span><br><span class="line">    log.info(<span class="string">&quot;sleep 4000ms，等待偏向锁激活&quot;</span>);</span><br><span class="line">    TimeUnit.SECONDS.sleep(<span class="number">4</span>);</span><br><span class="line"></span><br><span class="line">    <span class="type">Object</span> <span class="variable">lock</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">Object</span>();</span><br><span class="line">    log.info(<span class="string">&quot;Mark Word 初始为 =====&gt; 匿名偏向锁&quot;</span>);</span><br><span class="line">    log.info(ClassLayout.parseInstance(lock).toPrintable());</span><br><span class="line"></span><br><span class="line">    <span class="keyword">synchronized</span> (lock) &#123;</span><br><span class="line">        log.info(<span class="string">&quot;第一个线程 &#123;&#125; 获取锁 =====&gt; 偏向锁&quot;</span>, Thread.currentThread().getName());</span><br><span class="line">        log.info(ClassLayout.parseInstance(lock).toPrintable());</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="type">Thread</span> <span class="variable">thread</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">Thread</span>(() -&gt; &#123;</span><br><span class="line">        log.info(<span class="string">&quot;第二个线程 &#123;&#125; 尝试获取锁&quot;</span>, Thread.currentThread().getName());</span><br><span class="line">        log.info(ClassLayout.parseInstance(lock).toPrintable());</span><br><span class="line">        <span class="keyword">synchronized</span> (lock) &#123;</span><br><span class="line">            log.info(<span class="string">&quot;第二个线程 &#123;&#125; 获取锁 =====&gt; 轻量级锁&quot;</span>, Thread.currentThread().getName());</span><br><span class="line">            log.info(ClassLayout.parseInstance(lock).toPrintable());</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;, <span class="string">&quot;thread1&quot;</span>);</span><br><span class="line">    thread.start();</span><br><span class="line">    thread.join();</span><br><span class="line"></span><br><span class="line">    log.info(<span class="string">&quot;离开同步块后轻量级锁释放 =====&gt; 无锁状态（可偏向的）&quot;</span>);</span><br><span class="line">    log.info(ClassLayout.parseInstance(lock).toPrintable());</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
-
-<p>有相关资料提到在拥有偏向锁的线程死亡后，锁可以偏向新的线程，但是验证失败。</p>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">main</span><span class="params">(String[] args)</span> <span class="keyword">throws</span> IOException, InterruptedException &#123;</span><br><span class="line">    log.info(<span class="string">&quot;测试：之前获得偏向锁的线程已死时，新线程获得的仍然是偏向锁&quot;</span>);</span><br><span class="line"></span><br><span class="line">    log.info(<span class="string">&quot;sleep 4000ms，等待偏向锁激活&quot;</span>);</span><br><span class="line">    TimeUnit.MILLISECONDS.sleep(<span class="number">4000</span>);</span><br><span class="line"></span><br><span class="line">    <span class="type">Object</span> <span class="variable">lock</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">Object</span>();</span><br><span class="line">    log.info(<span class="string">&quot;Mark Word 初始为 =====&gt; 匿名偏向锁&quot;</span>);</span><br><span class="line">    log.info(ClassLayout.parseInstance(lock).toPrintable());</span><br><span class="line"></span><br><span class="line">    <span class="type">Thread</span> <span class="variable">thread1</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">Thread</span>(() -&gt; &#123;</span><br><span class="line">        <span class="keyword">synchronized</span> (lock) &#123;</span><br><span class="line">            log.info(<span class="string">&quot;第一个线程 &#123;&#125; 获取锁 =====&gt; 偏向锁&quot;</span>, Thread.currentThread().getName());</span><br><span class="line">            log.info(ClassLayout.parseInstance(lock).toPrintable());</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;, <span class="string">&quot;thread1&quot;</span>);</span><br><span class="line">    thread1.start();</span><br><span class="line"></span><br><span class="line">    <span class="type">Thread</span> <span class="variable">thread2</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">Thread</span>(() -&gt; &#123;</span><br><span class="line">        <span class="keyword">try</span> &#123;</span><br><span class="line">            thread1.join();</span><br><span class="line">        &#125; <span class="keyword">catch</span> (InterruptedException e) &#123;</span><br><span class="line">            <span class="keyword">throw</span> <span class="keyword">new</span> <span class="title class_">RuntimeException</span>(e);</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="type">boolean</span> <span class="variable">alive</span> <span class="operator">=</span> thread1.isAlive();</span><br><span class="line">        log.info(<span class="string">&quot;第一个线程 &#123;&#125; 是否存活 &#123;&#125;&quot;</span>, thread1.getName(), alive);</span><br><span class="line">        log.info(ClassLayout.parseInstance(lock).toPrintable());</span><br><span class="line">        <span class="keyword">synchronized</span> (lock) &#123;</span><br><span class="line">            log.info(<span class="string">&quot;即使第一个线程已死亡，第二个线程 &#123;&#125; 获取锁 =====&gt; 轻量级锁&quot;</span>, Thread.currentThread().getName());</span><br><span class="line">            log.info(ClassLayout.parseInstance(lock).toPrintable());</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;, <span class="string">&quot;thread2&quot;</span>);</span><br><span class="line">    thread2.start();</span><br><span class="line">    thread2.join();</span><br><span class="line"></span><br><span class="line">    log.info(<span class="string">&quot;离开同步块后轻量级锁释放 =====&gt; 无锁状态（可偏向的）&quot;</span>);</span><br><span class="line">    log.info(ClassLayout.parseInstance(lock).toPrintable());</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
-
-<h5 id="偏向锁-重量级锁"><a href="#偏向锁-重量级锁" class="headerlink" title="偏向锁-&gt;重量级锁"></a>偏向锁-&gt;重量级锁</h5><p>测试当拥有偏向锁的线程尚未离开同步块，其他线程尝试获取偏向锁（强竞争），锁将升级为重量级锁。</p>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">main</span><span class="params">(String[] args)</span> <span class="keyword">throws</span> InterruptedException &#123;</span><br><span class="line">    <span class="type">Scanner</span> <span class="variable">scanner</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">Scanner</span>(System.in);</span><br><span class="line">    log.info(<span class="string">&quot;测试：当持有偏向锁的线程尚未离开同步块，其他线程尝试获取偏向锁时，将升级为重量级锁&quot;</span>);</span><br><span class="line"></span><br><span class="line">    log.info(<span class="string">&quot;sleep 4000ms，等待偏向锁激活&quot;</span>);</span><br><span class="line">    TimeUnit.SECONDS.sleep(<span class="number">4</span>);</span><br><span class="line"></span><br><span class="line">    <span class="type">Object</span> <span class="variable">lock</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">Object</span>();</span><br><span class="line">    log.info(<span class="string">&quot;Mark Word 初始为 =====&gt; 匿名偏向锁&quot;</span>);</span><br><span class="line">    log.info(ClassLayout.parseInstance(lock).toPrintable());</span><br><span class="line"></span><br><span class="line">    <span class="type">Thread</span> <span class="variable">thread1</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">Thread</span>(() -&gt; &#123;</span><br><span class="line">        <span class="keyword">synchronized</span> (lock) &#123;</span><br><span class="line">            log.info(<span class="string">&quot;第一个线程 &#123;&#125; 获取锁 =====&gt; 偏向锁&quot;</span>, Thread.currentThread().getName());</span><br><span class="line">            log.info(ClassLayout.parseInstance(lock).toPrintable());</span><br><span class="line"></span><br><span class="line">            log.info(<span class="string">&quot;暂停，输入任意字符回车继续&quot;</span>);</span><br><span class="line">            scanner.next();</span><br><span class="line"></span><br><span class="line">            log.info(<span class="string">&quot;第一个线程 &#123;&#125; 持有偏向锁，在同步块内发生竞争 =====&gt; 升级为重量级锁&quot;</span>, Thread.currentThread().getName());</span><br><span class="line">            log.info(ClassLayout.parseInstance(lock).toPrintable());</span><br><span class="line">        &#125;</span><br><span class="line">        log.info(<span class="string">&quot;第一个线程 &#123;&#125; 结束&quot;</span>, Thread.currentThread().getName());</span><br><span class="line">    &#125;, <span class="string">&quot;thread1&quot;</span>);</span><br><span class="line">    thread1.start();</span><br><span class="line"></span><br><span class="line">    TimeUnit.SECONDS.sleep(<span class="number">1</span>);</span><br><span class="line"></span><br><span class="line">    <span class="type">Thread</span> <span class="variable">thread2</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">Thread</span>(() -&gt; &#123;</span><br><span class="line">        log.info(<span class="string">&quot;第二个线程 &#123;&#125; 尝试获取偏向锁失败&quot;</span>, Thread.currentThread().getName());</span><br><span class="line">        <span class="keyword">synchronized</span> (lock) &#123;</span><br><span class="line">            log.info(<span class="string">&quot;第二个线程 &#123;&#125; 获取锁 =====&gt; 重量级锁&quot;</span>, Thread.currentThread().getName());</span><br><span class="line">            log.info(ClassLayout.parseInstance(lock).toPrintable());</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;, <span class="string">&quot;thread2&quot;</span>);</span><br><span class="line">    thread2.start();</span><br><span class="line">    thread2.join();</span><br><span class="line"></span><br><span class="line">    log.info(<span class="string">&quot;即使离开同步块后 =====&gt; 重量级锁&quot;</span>);</span><br><span class="line">    log.info(ClassLayout.parseInstance(lock).toPrintable());</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
-
-<h5 id="偏向锁-偏向锁（特例）"><a href="#偏向锁-偏向锁（特例）" class="headerlink" title="偏向锁-&gt;偏向锁（特例）"></a>偏向锁-&gt;偏向锁（特例）</h5><p>这是一个很奇怪的测试用例，它是在测试中唯一发生不同线程对同一个锁获得偏向锁的情况。但是排查过程中发现两个线程的 <code>tid</code> 相同，猜测是局部变量表槽位复用时有什么优化机制。</p>
-<blockquote>
-<p>卡了我好久，也没有探究到实质的新信息。</p>
-</blockquote>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">main</span><span class="params">(String[] args)</span> <span class="keyword">throws</span> IOException, InterruptedException &#123;</span><br><span class="line">    log.info(<span class="string">&quot;测试：之前获得偏向锁的线程已死时，新线程获得的仍然是偏向锁&quot;</span>);</span><br><span class="line"></span><br><span class="line">    log.info(<span class="string">&quot;sleep 4000ms，等待偏向锁激活&quot;</span>);</span><br><span class="line">    TimeUnit.MILLISECONDS.sleep(<span class="number">4000</span>);</span><br><span class="line"></span><br><span class="line">    <span class="type">Object</span> <span class="variable">lock</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">Object</span>();</span><br><span class="line">    log.info(<span class="string">&quot;Mark Word 初始为 =====&gt; 匿名偏向锁&quot;</span>);</span><br><span class="line">    log.info(ClassLayout.parseInstance(lock).toPrintable());</span><br><span class="line"></span><br><span class="line">    <span class="type">Thread</span> <span class="variable">thread1</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">Thread</span>(() -&gt; &#123;</span><br><span class="line">        <span class="keyword">synchronized</span> (lock) &#123;</span><br><span class="line">            log.info(<span class="string">&quot;第一个线程 &#123;&#125; 获取锁 =====&gt; 偏向锁&quot;</span>, Thread.currentThread().getName());</span><br><span class="line">            log.info(ClassLayout.parseInstance(lock).toPrintable());</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;, <span class="string">&quot;thread1&quot;</span>);</span><br><span class="line">    thread1.start();</span><br><span class="line">    thread1.join();</span><br><span class="line"></span><br><span class="line">    <span class="type">Thread</span> <span class="variable">thread2</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">Thread</span>(() -&gt; &#123;</span><br><span class="line">        <span class="keyword">synchronized</span> (lock) &#123;</span><br><span class="line">            log.info(<span class="string">&quot;第二个线程 &#123;&#125; 获取锁，=====&gt; 偏向锁&quot;</span>, Thread.currentThread().getName());</span><br><span class="line">            log.info(<span class="string">&quot;震惊！！！为什么两个 tid 相同啊，有什么复用机制吗&quot;</span>);</span><br><span class="line">            log.info(ClassLayout.parseInstance(lock).toPrintable());</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;, <span class="string">&quot;thread2&quot;</span>);</span><br><span class="line">    thread2.start();</span><br><span class="line">    thread2.join();</span><br><span class="line"></span><br><span class="line">    log.info(<span class="string">&quot;偏向锁等到竞争出现才释放锁，因此离开同步方法块后，Mark Word 不变&quot;</span>);</span><br><span class="line">    log.info(ClassLayout.parseInstance(lock).toPrintable());</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
-
-<h5 id="匿名偏向锁状态计算-hashCode"><a href="#匿名偏向锁状态计算-hashCode" class="headerlink" title="匿名偏向锁状态计算 hashCode"></a>匿名偏向锁状态计算 hashCode</h5><p>在匿名偏向锁状态计算 <code>hashCode</code>，锁将变为无锁状态。</p>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">main</span><span class="params">(String[] args)</span> <span class="keyword">throws</span> InterruptedException &#123;</span><br><span class="line">    log.info(<span class="string">&quot;测试：在匿名偏向锁状态计算 hashCode&quot;</span>);</span><br><span class="line"></span><br><span class="line">    log.info(<span class="string">&quot;sleep 4000ms，等待偏向锁激活&quot;</span>);</span><br><span class="line">    TimeUnit.MILLISECONDS.sleep(<span class="number">4000</span>);</span><br><span class="line"></span><br><span class="line">    <span class="type">Object</span> <span class="variable">lock</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">Object</span>();</span><br><span class="line">    log.info(<span class="string">&quot;Mark Word 初始为 =====&gt; 匿名偏向锁&quot;</span>);</span><br><span class="line">    log.info(ClassLayout.parseInstance(lock).toPrintable());</span><br><span class="line"></span><br><span class="line">    <span class="type">int</span> <span class="variable">hashCode</span> <span class="operator">=</span> lock.hashCode();</span><br><span class="line">    log.info(<span class="string">&quot;在计算 hashCode 后：Mark Word =====&gt; 无锁状态（hash|age|0|01）&quot;</span>);</span><br><span class="line">    log.info(ClassLayout.parseInstance(lock).toPrintable());</span><br><span class="line"></span><br><span class="line">    <span class="keyword">synchronized</span> (lock) &#123;</span><br><span class="line">        log.info(<span class="string">&quot;获取锁 =====&gt; 轻量级锁&quot;</span>);</span><br><span class="line">        log.info(ClassLayout.parseInstance(lock).toPrintable());</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    log.info(<span class="string">&quot;离开同步块后轻量级锁释放 =====&gt; 无锁状态（hash|age|0|01）&quot;</span>);</span><br><span class="line">    log.info(ClassLayout.parseInstance(lock).toPrintable());</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
-
-<h5 id="偏向锁状态无锁时计算-hashCode"><a href="#偏向锁状态无锁时计算-hashCode" class="headerlink" title="偏向锁状态无锁时计算 hashCode"></a>偏向锁状态无锁时计算 hashCode</h5><p>在偏向锁状态无锁时计算 <code>hashCode</code>，锁将变为无锁状态。</p>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">main</span><span class="params">(String[] args)</span> <span class="keyword">throws</span> InterruptedException &#123;</span><br><span class="line">    log.info(<span class="string">&quot;测试：在偏向锁状态无锁时计算 hashCode&quot;</span>);</span><br><span class="line"></span><br><span class="line">    log.info(<span class="string">&quot;sleep 4000ms，等待偏向锁激活&quot;</span>);</span><br><span class="line">    TimeUnit.MILLISECONDS.sleep(<span class="number">4000</span>);</span><br><span class="line"></span><br><span class="line">    <span class="type">Object</span> <span class="variable">lock</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">Object</span>();</span><br><span class="line">    log.info(<span class="string">&quot;Mark Word 初始为 =====&gt; 匿名偏向锁&quot;</span>);</span><br><span class="line">    log.info(ClassLayout.parseInstance(lock).toPrintable());</span><br><span class="line"></span><br><span class="line">    <span class="keyword">synchronized</span> (lock) &#123;</span><br><span class="line">        log.info(<span class="string">&quot;获取锁 =====&gt; 偏向锁&quot;</span>);</span><br><span class="line">        log.info(ClassLayout.parseInstance(lock).toPrintable());</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="type">int</span> <span class="variable">hashCode</span> <span class="operator">=</span> lock.hashCode();</span><br><span class="line">    log.info(<span class="string">&quot;离开同步块后再计算 hashCode：Mark Word =====&gt; 无锁状态&quot;</span>);</span><br><span class="line">    log.info(ClassLayout.parseInstance(lock).toPrintable());</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
-
-<h5 id="偏向锁状态加锁时计算-hashCode"><a href="#偏向锁状态加锁时计算-hashCode" class="headerlink" title="偏向锁状态加锁时计算 hashCode"></a>偏向锁状态加锁时计算 hashCode</h5><p>在偏向锁状态加锁时计算 <code>hashCode</code>，锁将升级为重量级锁状态。</p>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">main</span><span class="params">(String[] args)</span> <span class="keyword">throws</span> InterruptedException &#123;</span><br><span class="line">    log.info(<span class="string">&quot;测试：在偏向锁状态计算 hashCode&quot;</span>);</span><br><span class="line"></span><br><span class="line">    log.info(<span class="string">&quot;sleep 4000ms，等待偏向锁激活&quot;</span>);</span><br><span class="line">    TimeUnit.MILLISECONDS.sleep(<span class="number">4000</span>);</span><br><span class="line"></span><br><span class="line">    <span class="type">Object</span> <span class="variable">lock</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">Object</span>();</span><br><span class="line">    log.info(<span class="string">&quot;Mark Word 初始为 =====&gt; 匿名偏向锁&quot;</span>);</span><br><span class="line">    log.info(ClassLayout.parseInstance(lock).toPrintable());</span><br><span class="line"></span><br><span class="line">    <span class="keyword">synchronized</span> (lock) &#123;</span><br><span class="line">        log.info(<span class="string">&quot;获取锁 =====&gt; 偏向锁&quot;</span>);</span><br><span class="line">        log.info(ClassLayout.parseInstance(lock).toPrintable());</span><br><span class="line"></span><br><span class="line">        <span class="type">int</span> <span class="variable">hashCode</span> <span class="operator">=</span> lock.hashCode();</span><br><span class="line">        log.info(<span class="string">&quot;在计算 hashCode 后：Mark Word =====&gt; 重量级锁&quot;</span>);</span><br><span class="line">        log.info(ClassLayout.parseInstance(lock).toPrintable());</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    log.info(<span class="string">&quot;即使离开同步块后 =====&gt; 重量级锁&quot;</span>);</span><br><span class="line">    log.info(ClassLayout.parseInstance(lock).toPrintable());</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
-
-<h3 id="轻量级锁"><a href="#轻量级锁" class="headerlink" title="轻量级锁"></a>轻量级锁</h3><h4 id="轻量级锁加锁"><a href="#轻量级锁加锁" class="headerlink" title="轻量级锁加锁"></a>轻量级锁加锁</h4><p>获取偏向锁失败后续处理一（是否是偏向锁为 <code>0</code>）：</p>
-<ul>
-<li>检测锁标志位是否为 <code>01</code> 或者 <code>00</code><ul>
-<li>如果否，则说明是重量级锁状态 &#x3D;&#x3D;&#x3D;&#x3D;&#x3D;&gt; <em>获取轻量级锁失败后续处理一</em></li>
-<li>如果是，则说明是无锁状态或者轻量级锁状态，尝试<strong>通过 <code>CAS</code> 操作设置轻量级锁</strong><ul>
-<li>如果成功，说明获得轻量级锁</li>
-<li>如果失败，说明发生竞争 &#x3D;&#x3D;&#x3D;&#x3D;&#x3D;&gt; <em>获取轻量级锁失败后续处理二</em></li>
-</ul>
-</li>
-</ul>
-</li>
-</ul>
-<blockquote>
-<p>在<strong>通过 <code>CAS</code> 操作设置轻量级锁</strong>中，<code>Compare</code> 操作是“测试 <code>Mark Word</code> 的锁标志位是否为 <code>01</code>，代表处于无锁状态”，<code>Swap</code> 操作是将 <code>Mark Word</code> 复制到栈中锁记录，并将指向栈中锁记录的指针设置到 <code>Mark Word</code> 的相应位置以及修改锁标志位。所谓“栈中锁记录”又称为 <code>Displaced Mark Word</code>，<code>JVM</code> 会在当前线程的栈帧中创建用于存储锁记录的空间，用于在轻量级锁状态下临时存放 <code>Mark Word</code>。</p>
-</blockquote>
-<blockquote>
-<p>在轻量级锁状态下，明确提及了锁记录的作用，但偏向锁状态下，提及锁记录却并未加以解释。</p>
-</blockquote>
-<p>获取偏向锁失败后续处理一：</p>
-<ul>
-<li>已经升级为重量级锁</li>
-</ul>
-<p>获取偏向锁失败后续处理二（通过 <code>CAS</code> 加偏向锁失败）：</p>
-<ul>
-<li>获取锁失败的线程将锁升级为重量级锁，修改 <code>Mark Word</code> 为<code>指向互斥量（重量级锁）的指针|10</code>（这个操作将影响到持有轻量级锁的线程的解锁）</li>
-<li>线程阻塞，等待唤醒</li>
-</ul>
-<p>补充思考：</p>
-<ul>
-<li>有相关资料提及偏向锁并非直接升级到重量级锁，无法验证是否总是有轻量级锁作为中间状态</li>
-<li>轻量级锁面临竞争时升级为重量级锁的过程相比于偏向锁面临竞争时的升级过程，更加容易理解，后者好多细节没有找到令人信服的答案。</li>
-</ul>
-<h4 id="轻量级锁解锁"><a href="#轻量级锁解锁" class="headerlink" title="轻量级锁解锁"></a>轻量级锁解锁</h4><p>轻量级锁解锁时，会通过 <code>CAS</code> 操作解锁，<code>Compare</code> 操作是“测试 <code>Mark Word</code> 的锁标志位是否为 <code>00</code>，代表处于轻量级锁状态，<code>Swap</code> 操作是将栈中锁记录 <code>Dispaced Mark Word</code> 替换回对象头的 <code>Mark Word</code> 以及修改锁标志位。<br>如果 <code>Compare</code> 操作失败，则代表发生竞争，此时锁已经被其他线程升级为重量级锁以及 <code>Mark Word</code> 被修改为<code>指向互斥量（重量级锁）的指针|10</code>。持有轻量级锁的线程会释放锁（直接将 <code>Dispaced Mark Word</code> 替换回 <code>Mark Word</code>？）并唤醒等待的线程，开启新的一轮争抢。</p>
-<h4 id="测试轻量级锁升级"><a href="#测试轻量级锁升级" class="headerlink" title="测试轻量级锁升级"></a>测试轻量级锁升级</h4><h5 id="无锁-轻量级锁"><a href="#无锁-轻量级锁" class="headerlink" title="无锁-&gt;轻量级锁"></a>无锁-&gt;轻量级锁</h5><p>测试在无锁状态下获取锁，锁将变成轻量级锁状态。</p>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">main</span><span class="params">(String[] args)</span> <span class="keyword">throws</span> IOException, InterruptedException &#123;</span><br><span class="line">    <span class="type">Scanner</span> <span class="variable">scanner</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">Scanner</span>(System.in);</span><br><span class="line">    log.info(<span class="string">&quot;轻量级锁基础测试：无锁状态 -&gt; 轻量级锁&quot;</span>);</span><br><span class="line"></span><br><span class="line">    <span class="type">Object</span> <span class="variable">lock</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">Object</span>();</span><br><span class="line">    log.info(<span class="string">&quot;在偏向锁激活之前创建的对象为 =====&gt; 无锁状态（可偏向额）&quot;</span>);</span><br><span class="line">    log.info(ClassLayout.parseInstance(lock).toPrintable());</span><br><span class="line"></span><br><span class="line">    <span class="keyword">synchronized</span> (lock) &#123;</span><br><span class="line">        log.info(<span class="string">&quot;即使是单线程无竞争获取锁，=====&gt; 轻量级锁&quot;</span>);</span><br><span class="line">        log.info(ClassLayout.parseInstance(lock).toPrintable());</span><br><span class="line">        log.info(<span class="string">&quot;暂停，回车继续&quot;</span>);</span><br><span class="line">        scanner.nextLine();</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    log.info(<span class="string">&quot;离开同步块后，-&gt; 无锁状态（可偏向的）&quot;</span>);</span><br><span class="line">    log.info(ClassLayout.parseInstance(lock).toPrintable());</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
-
-<h5 id="无锁状态计算-hashCode"><a href="#无锁状态计算-hashCode" class="headerlink" title="无锁状态计算 hashCode"></a>无锁状态计算 hashCode</h5><p>在无锁状态计算 <code>hashCode</code>，仍然是无锁状态。</p>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">main</span><span class="params">(String[] args)</span> <span class="keyword">throws</span> InterruptedException &#123;</span><br><span class="line">    log.info(<span class="string">&quot;测试：在无锁状态计算 hashCode&quot;</span>);</span><br><span class="line"></span><br><span class="line">    <span class="type">Object</span> <span class="variable">lock</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">Object</span>();</span><br><span class="line">    log.info(<span class="string">&quot;Mark Word 初始为 =====&gt; 无锁状态&quot;</span>);</span><br><span class="line">    log.info(ClassLayout.parseInstance(lock).toPrintable());</span><br><span class="line"></span><br><span class="line">    <span class="type">int</span> <span class="variable">hashCode</span> <span class="operator">=</span> lock.hashCode();</span><br><span class="line">    log.info(<span class="string">&quot;在计算 hashCode 后：Mark Word =====&gt; 无锁状态（hash|age|0|01）&quot;</span>);</span><br><span class="line">    log.info(ClassLayout.parseInstance(lock).toPrintable());</span><br><span class="line"></span><br><span class="line">    <span class="keyword">synchronized</span> (lock) &#123;</span><br><span class="line">        log.info(<span class="string">&quot;获取锁 =====&gt; 轻量级锁&quot;</span>);</span><br><span class="line">        log.info(ClassLayout.parseInstance(lock).toPrintable());</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    log.info(<span class="string">&quot;离开同步块后轻量级锁释放 =====&gt; 无锁状态（hash|age|0|01）&quot;</span>);</span><br><span class="line">    log.info(ClassLayout.parseInstance(lock).toPrintable());</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
-
-<h5 id="轻量级锁加锁时计算-hashCode"><a href="#轻量级锁加锁时计算-hashCode" class="headerlink" title="轻量级锁加锁时计算 hashCode"></a>轻量级锁加锁时计算 hashCode</h5><p>在轻量级锁状态加锁时计算 <code>hashCode</code>，锁将升级为重量级锁状态。</p>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">main</span><span class="params">(String[] args)</span> <span class="keyword">throws</span> InterruptedException &#123;</span><br><span class="line">    log.info(<span class="string">&quot;测试：在轻量级锁状态计算 hashCode&quot;</span>);</span><br><span class="line"></span><br><span class="line">    <span class="type">Object</span> <span class="variable">lock</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">Object</span>();</span><br><span class="line">    log.info(<span class="string">&quot;Mark Word 初始为 =====&gt; 无锁状态&quot;</span>);</span><br><span class="line">    log.info(ClassLayout.parseInstance(lock).toPrintable());</span><br><span class="line"></span><br><span class="line">    <span class="keyword">synchronized</span> (lock) &#123;</span><br><span class="line">        log.info(<span class="string">&quot;获取锁 =====&gt; 轻量级锁&quot;</span>);</span><br><span class="line">        log.info(ClassLayout.parseInstance(lock).toPrintable());</span><br><span class="line"></span><br><span class="line">        <span class="type">int</span> <span class="variable">hashCode</span> <span class="operator">=</span> lock.hashCode();</span><br><span class="line">        log.info(<span class="string">&quot;在计算 hashCode 后：Mark Word =====&gt; 重量级锁&quot;</span>);</span><br><span class="line">        log.info(ClassLayout.parseInstance(lock).toPrintable());</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    log.info(<span class="string">&quot;即使离开同步块后 =====&gt; 重量级锁&quot;</span>);</span><br><span class="line">    log.info(ClassLayout.parseInstance(lock).toPrintable());</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
-
-<h2 id="参考文章"><a href="#参考文章" class="headerlink" title="参考文章"></a>参考文章</h2><ul>
-<li>《Java 并发编程的艺术》</li>
-<li><a href="https://www.cnblogs.com/FraserYu/p/15743542.html">难搞的偏向锁终于被 Java 移除了</a></li>
-<li><a href="https://stackoverflow.com/questions/60985782/details-about-mark-word-of-java-object-header">Details about mark word of java object header</a></li>
-</ul>
-]]></content>
-      <tags>
-        <tag>java</tag>
-        <tag>lock</tag>
-        <tag>synchronized</tag>
-      </tags>
-  </entry>
-  <entry>
-    <title>Unsafe，一个“反 Java”的 class</title>
-    <url>/2023/12/25/Unsafe-an-anti-Java-class/</url>
-    <content><![CDATA[<p><code>Unsafe</code> 类位于 <code>sun.misc</code> 包中，它提供了一组用于执行低级别、不安全操作的方法。尽管 <code>Unsafe</code> 类及其所有方法都是公共的，但它的使用受到限制，因为只有受信任的代码才能获取其实例。这个类通常被用于一些底层的、对性能敏感的操作，比如直接内存访问、<code>CAS</code>（<code>Compare and Swap</code>）操作等。本文将介绍这个“反 <code>Java</code>”的类及其方法的典型使用场景。</p>
-<span id="more"></span>
-
-<blockquote>
-<p>由于 <code>Unsafe</code> 类涉及到直接内存访问和其他底层操作，使用它需要极大的谨慎，因为它可以绕过 <code>Java</code> 语言的一些安全性和健壮性检查。在正常的应用程序代码中，最好避免直接使用 <code>Unsafe</code> 类，以确保代码的可读性和可维护性。在一些特殊情况下，比如一些高性能库的实现，可能会使用 <code>Unsafe</code> 类来进行一些性能优化。</p>
-</blockquote>
-<blockquote>
-<p>尽管在生产中需要谨慎使用 <code>Unsafe</code>，但是可以在测试中使用它来更真实地接触 <code>Java</code> 对象在内存中的存储结构，验证自己的理论知识。</p>
-</blockquote>
-<h2 id="获取-Unsafe-实例"><a href="#获取-Unsafe-实例" class="headerlink" title="获取 Unsafe 实例"></a>获取 Unsafe 实例</h2><blockquote>
-<p>在 <code>Java 9</code> 及之后的版本中，<code>Unsafe</code> 类中的 <code>getUnsafe()</code> 方法被标记为不安全（<code>Unsafe</code>），不再允许普通的 <code>Java</code> 应用程序代码通过此方法获取 <code>Unsafe</code> 实例。这是为了提高 <code>Java</code> 的安全性，防止滥用 <code>Unsafe</code> 类的功能。</p>
-</blockquote>
-<p>在正常的 <code>Java</code> 应用程序中，获取 <code>Unsafe</code> 实例是不被推荐的，因为它违反了 <code>Java</code> 语言的安全性和封装原则。<code>Unsafe</code> 类的设计本意是为了 <code>Java</code> 库和虚拟机的实现使用，而不是为了普通应用程序开发者使用。<code>Unsafe</code> 对象为调用者提供了执行不安全操作的能力，它可用于在任意内存地址读取和写入数据，因此返回的 <code>Unsafe</code> 对象应由调用者仔细保护。它绝不能传递给不受信任的代码。此类中的大多数方法都是非常低级的，并且对应于少量硬件指令。</p>
-<p>获取 <code>Unsafe</code> 实例的静态方法如下：</p>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="meta">@CallerSensitive</span></span><br><span class="line"><span class="keyword">public</span> <span class="keyword">static</span> Unsafe <span class="title function_">getUnsafe</span><span class="params">()</span> &#123;</span><br><span class="line">    Class&lt;?&gt; caller = Reflection.getCallerClass();</span><br><span class="line">    <span class="comment">// 检查调用方法的类是被引导类加载器所加载</span></span><br><span class="line">    <span class="keyword">if</span> (!VM.isSystemDomainLoader(caller.getClassLoader()))</span><br><span class="line">        <span class="keyword">throw</span> <span class="keyword">new</span> <span class="title class_">SecurityException</span>(<span class="string">&quot;Unsafe&quot;</span>);</span><br><span class="line">    <span class="keyword">return</span> theUnsafe;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
-
-<p><code>Unsafe</code> 使用单例模式，可以通过静态方法 <code>getUnsafe</code> 获取 <code>Unsafe</code> 实例，并且调用方法的类为启动类加载器所加载才不会抛出异常。获取 <code>Unsafe</code> 实例有以下两种可行方案：</p>
-<ol>
-<li>通过 <code>-Xbootclasspath/a:$&#123;path&#125;</code> 把调用方法的类所在的 <code>jar</code> 包路径追加到启动类路径中，使该类被启动类加载器加载。关于启动类路径的信息可以参考<a href="https://www.moralok.com/2023/07/13/Java-class-loader-source-code-analysis/#ClassLoader-%E7%9A%84%E6%90%9C%E7%B4%A2%E8%B7%AF%E5%BE%84">Java 类加载器源码分析 | ClassLoader 的搜索路径</a></li>
-<li>通过反射获取 <code>Unsafe</code> 类中的 <code>Unsafe</code> 实例<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">private</span> <span class="keyword">static</span> Unsafe <span class="title function_">getUnsafe</span><span class="params">()</span> &#123;</span><br><span class="line">    <span class="keyword">try</span> &#123;</span><br><span class="line">        <span class="type">Field</span> <span class="variable">f</span> <span class="operator">=</span> Unsafe.class.getDeclaredField(<span class="string">&quot;theUnsafe&quot;</span>);</span><br><span class="line">        f.setAccessible(<span class="literal">true</span>);</span><br><span class="line">        <span class="keyword">return</span> (Unsafe) f.get(<span class="literal">null</span>);</span><br><span class="line">    &#125; <span class="keyword">catch</span> (NoSuchFieldException | IllegalAccessException e) &#123;</span><br><span class="line">        <span class="keyword">throw</span> <span class="keyword">new</span> <span class="title class_">RuntimeException</span>(e);</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure></li>
-</ol>
-<h2 id="内存操作"><a href="#内存操作" class="headerlink" title="内存操作"></a>内存操作</h2><p><code>Unsafe</code> 类中包含了一些关于内存操作的方法，这些方法通常被认为是不安全的，因为它们可以绕过 <code>Java</code> 语言的内置安全性和类型检查。以下是一些常见的 <code>Unsafe</code> 类中关于内存操作的方法：</p>
-<ul>
-<li><code>allocateMemory</code>: 分配一个给定大小（以字节为单位）的本地内存块，内容未初始化，通常是垃圾。生成的本地指针永远不会为零，并且将针对所有类型进行对齐。<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">native</span> <span class="type">long</span> <span class="title function_">allocateMemory</span><span class="params">(<span class="type">long</span> bytes)</span>;</span><br></pre></td></tr></table></figure></li>
-<li><code>reallocateMemory</code>: 将本地内存块的大小调整为给定大小（以字节为单位），超过旧内存块大小的内容未初始化，通常是垃圾。当且仅当请求的大小为零时，生成的本地指针才为零。传递给此方法的地址可能为空，在这种情况下将执行分配。<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">native</span> <span class="type">long</span> <span class="title function_">reallocateMemory</span><span class="params">(<span class="type">long</span> address, <span class="type">long</span> bytes)</span>;</span><br></pre></td></tr></table></figure></li>
-<li><code>freeMemory</code>: 释放之前由 <code>allocateMemory</code> 或 <code>reallocateMemory</code> 分配的内存。<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">native</span> <span class="keyword">void</span> <span class="title function_">freeMemory</span><span class="params">(<span class="type">long</span> address)</span>;</span><br></pre></td></tr></table></figure></li>
-<li><code>setMemory</code>: 将给定内存块中的所有字节设置为固定值（通常为零）。<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">native</span> <span class="keyword">void</span> <span class="title function_">setMemory</span><span class="params">(Object o, <span class="type">long</span> offset, <span class="type">long</span> bytes, <span class="type">byte</span> value)</span>;</span><br><span class="line"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title function_">setMemory</span><span class="params">(<span class="type">long</span> address, <span class="type">long</span> bytes, <span class="type">byte</span> value)</span> &#123;</span><br><span class="line">    setMemory(<span class="literal">null</span>, address, bytes, value);</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure></li>
-<li><code>copyMemory</code>: 复制指定长度的内存块<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">native</span> <span class="keyword">void</span> <span class="title function_">copyMemory</span><span class="params">(Object srcBase, <span class="type">long</span> srcOffset, Object destBase, <span class="type">long</span> destOffset, <span class="type">long</span> bytes)</span>;</span><br></pre></td></tr></table></figure></li>
-<li><code>putXxx</code>: 将指定偏移量处的内存设置为指定的值，其中 <code>Xxx</code> 可以是 <code>Object</code>、<code>int</code>、<code>long</code>、<code>float</code> 和 <code>double</code> 等。<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">native</span> <span class="keyword">void</span> <span class="title function_">putObject</span><span class="params">(Object o, <span class="type">long</span> offset, Object x)</span>;</span><br></pre></td></tr></table></figure></li>
-<li><code>getXxx</code>: 从指定偏移量处的内存读取值，其中 <code>Xxx</code> 可以是 <code>Object</code>、<code>int</code>、<code>long</code>、<code>float</code> 和 <code>double</code> 等。<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">native</span> Object <span class="title function_">getObject</span><span class="params">(Object o, <span class="type">long</span> offset)</span>;</span><br></pre></td></tr></table></figure></li>
-<li><code>putXxx</code> 和 <code>getXxx</code> 也提供了按绝对基地址操作内存的方法。<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">native</span> <span class="type">byte</span> <span class="title function_">getByte</span><span class="params">(<span class="type">long</span> address)</span>;</span><br><span class="line"><span class="keyword">public</span> <span class="keyword">native</span> <span class="keyword">void</span> <span class="title function_">putByte</span><span class="params">(<span class="type">long</span> address, <span class="type">byte</span> x)</span>;</span><br></pre></td></tr></table></figure></li>
-</ul>
-<p>从内存读取值时，除非满足以下情况之一，否则结果不确定：</p>
-<ol>
-<li>偏移量是通过 <code>objectFieldOffset</code> 从字段的 <code>Field</code> 对象获取的，<code>o</code> 指向的对象的类与字段所属的类兼容。</li>
-<li>偏移量和 <code>o</code> 指向的对象（无论是否为 <code>null</code>）分别是通过 <code>staticFieldOffset</code> 和 <code>staticFieldBase</code> 从 <code>Field</code> 对象获得的。</li>
-<li><code>o</code> 指向的是一个数组，偏移量是一个形式为 <code>B+N*S</code> 的整数，其中 <code>N</code> 是数组的有效索引，<code>B</code> 和 <code>S</code> 分别是通过 <code>arrayBaseOffset</code> 和 <code>arrayIndexScale</code> 获得的值。</li>
-</ol>
-<blockquote>
-<p>做一些“不确定”的测试，比如使用 <code>byte</code> 相关的方法操作 <code>int</code> 所在的内存块，是有意思且有帮助的，了解如何破坏，也可以更好地学习如何保护。</p>
-</blockquote>
-<h3 id="分配堆外内存"><a href="#分配堆外内存" class="headerlink" title="分配堆外内存"></a>分配堆外内存</h3><p>在 <code>Java NIO</code>（<code>New I/O</code>）中，分配堆外内存使用了 <code>Unsafe</code> 类的 <code>allocateMemory</code> 方法。堆外内存是一种在 <code>Java</code> 虚拟机之外分配的内存，它不受 <code>Java</code> 堆内存管理机制的控制。这种内存分配的主要目的是提高 <code>I/O</code> 操作的性能，因为它可以直接与底层操作系统进行交互，而不涉及 <code>Java</code> 堆内存的复杂性。Java 虚拟机的垃圾回收器虽然不直接管理这块内存，但是它通过一种称为“引用清理”（<code>Reference Counting</code>）的机制来处理。</p>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line">DirectByteBuffer(<span class="type">int</span> cap) &#123;</span><br><span class="line">    <span class="built_in">super</span>(-<span class="number">1</span>, <span class="number">0</span>, cap, cap);</span><br><span class="line">    <span class="type">boolean</span> <span class="variable">pa</span> <span class="operator">=</span> VM.isDirectMemoryPageAligned();</span><br><span class="line">    <span class="type">int</span> <span class="variable">ps</span> <span class="operator">=</span> Bits.pageSize();</span><br><span class="line">    <span class="type">long</span> <span class="variable">size</span> <span class="operator">=</span> Math.max(<span class="number">1L</span>, (<span class="type">long</span>)cap + (pa ? ps : <span class="number">0</span>));</span><br><span class="line">    Bits.reserveMemory(size, cap);</span><br><span class="line"></span><br><span class="line">    <span class="type">long</span> <span class="variable">base</span> <span class="operator">=</span> <span class="number">0</span>;</span><br><span class="line">    <span class="keyword">try</span> &#123;</span><br><span class="line">        <span class="comment">// 分配本地内存</span></span><br><span class="line">        base = unsafe.allocateMemory(size);</span><br><span class="line">    &#125; <span class="keyword">catch</span> (OutOfMemoryError x) &#123;</span><br><span class="line">        Bits.unreserveMemory(size, cap);</span><br><span class="line">        <span class="keyword">throw</span> x;</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="comment">// 初始化本地内存</span></span><br><span class="line">    unsafe.setMemory(base, size, (<span class="type">byte</span>) <span class="number">0</span>);</span><br><span class="line">    <span class="keyword">if</span> (pa &amp;&amp; (base % ps != <span class="number">0</span>)) &#123;</span><br><span class="line">        <span class="comment">// Round up to page boundary</span></span><br><span class="line">        address = base + ps - (base &amp; (ps - <span class="number">1</span>));</span><br><span class="line">    &#125; <span class="keyword">else</span> &#123;</span><br><span class="line">        address = base;</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="comment">// 使用虚引用 Cleaner 对象跟踪 DirectByteBuffer 对象的垃圾回收</span></span><br><span class="line">    cleaner = Cleaner.create(<span class="built_in">this</span>, <span class="keyword">new</span> <span class="title class_">Deallocator</span>(base, size, cap));</span><br><span class="line">    att = <span class="literal">null</span>;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
-
-<p>当 <code>DirectByteBuffer</code> 对象仅被 <code>Cleaner</code> 对象（虚引用）引用时，它可以在任意一次 <code>GC</code> 中被垃圾回收。在 <code>DirectByteBuffer</code> 对象被垃圾回收后，<code>Cleaner</code> 对象会被加入到引用队列，<code>ReferenceHandler</code> 线程将调用 <code>Deallocator</code> 对象的 <code>run</code> 方法，从而实现本地内存的自动释放。</p>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">private</span> <span class="keyword">static</span> <span class="keyword">class</span> <span class="title class_">Deallocator</span> <span class="keyword">implements</span> <span class="title class_">Runnable</span> &#123;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">static</span> <span class="type">Unsafe</span> <span class="variable">unsafe</span> <span class="operator">=</span> Unsafe.getUnsafe();</span><br><span class="line"></span><br><span class="line">    <span class="keyword">private</span> <span class="type">long</span> address;</span><br><span class="line">    <span class="keyword">private</span> <span class="type">long</span> size;</span><br><span class="line">    <span class="keyword">private</span> <span class="type">int</span> capacity;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">private</span> <span class="title function_">Deallocator</span><span class="params">(<span class="type">long</span> address, <span class="type">long</span> size, <span class="type">int</span> capacity)</span> &#123;</span><br><span class="line">        <span class="keyword">assert</span> (address != <span class="number">0</span>);</span><br><span class="line">        <span class="built_in">this</span>.address = address;</span><br><span class="line">        <span class="built_in">this</span>.size = size;</span><br><span class="line">        <span class="built_in">this</span>.capacity = capacity;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">public</span> <span class="keyword">void</span> <span class="title function_">run</span><span class="params">()</span> &#123;</span><br><span class="line">        <span class="keyword">if</span> (address == <span class="number">0</span>) &#123;</span><br><span class="line">            <span class="comment">// Paranoia</span></span><br><span class="line">            <span class="keyword">return</span>;</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="comment">// 释放本地内存</span></span><br><span class="line">        unsafe.freeMemory(address);</span><br><span class="line">        address = <span class="number">0</span>;</span><br><span class="line">        Bits.unreserveMemory(size, capacity);</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
-
-<h2 id="CAS-相关"><a href="#CAS-相关" class="headerlink" title="CAS 相关"></a>CAS 相关</h2><p><code>Unsafe</code> 提供了 <code>3</code> 个 <code>CAS</code> 相关操作的方法，方法将内存位置的值与预期原值比较，如果相匹配，则 <code>CPU</code> 会自动将该位置更新为新值，否则，<code>CPU</code> 不做任何操作。这些方法的底层实现对应着 <code>CPU</code> 指令 <code>cmpxchg</code>。</p>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="comment">// 如果 Java 变量当前符合预期，则自动将其更新为 x。</span></span><br><span class="line"><span class="keyword">public</span> <span class="keyword">final</span> <span class="keyword">native</span> <span class="type">boolean</span> <span class="title function_">compareAndSwapObject</span><span class="params">(Object o, <span class="type">long</span> offset, Object expected, Object x)</span>;</span><br><span class="line"><span class="keyword">public</span> <span class="keyword">final</span> <span class="keyword">native</span> <span class="type">boolean</span> <span class="title function_">compareAndSwapInt</span><span class="params">(Object o, <span class="type">long</span> offset, <span class="type">int</span> expected, <span class="type">int</span> x)</span>;</span><br><span class="line"><span class="keyword">public</span> <span class="keyword">final</span> <span class="keyword">native</span> <span class="type">boolean</span> <span class="title function_">compareAndSwapLong</span><span class="params">(Object o, <span class="type">long</span> offset, <span class="type">long</span> expected, <span class="type">long</span> x)</span>;</span><br></pre></td></tr></table></figure>
-
-<p>在 <code>AtomicInteger</code> 的实现中，静态字段 <code>valueOffset</code> 即为字段 <code>value</code> 的内存偏移地址，<code>valueOffset</code> 的值在 <code>AtomicInteger</code> 初始化时，在静态代码块中通过 <code>Unsafe</code> 的 <code>objectFieldOffset</code> 方法获取。</p>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">class</span> <span class="title class_">AtomicInteger</span> <span class="keyword">extends</span> <span class="title class_">Number</span> <span class="keyword">implements</span> <span class="title class_">java</span>.io.Serializable &#123;</span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">static</span> <span class="keyword">final</span> <span class="type">long</span> <span class="variable">serialVersionUID</span> <span class="operator">=</span> <span class="number">6214790243416807050L</span>;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// setup to use Unsafe.compareAndSwapInt for updates</span></span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">static</span> <span class="keyword">final</span> <span class="type">Unsafe</span> <span class="variable">unsafe</span> <span class="operator">=</span> Unsafe.getUnsafe();</span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">static</span> <span class="keyword">final</span> <span class="type">long</span> valueOffset;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">static</span> &#123;</span><br><span class="line">        <span class="keyword">try</span> &#123;</span><br><span class="line">            valueOffset = unsafe.objectFieldOffset</span><br><span class="line">                (AtomicInteger.class.getDeclaredField(<span class="string">&quot;value&quot;</span>));</span><br><span class="line">        &#125; <span class="keyword">catch</span> (Exception ex) &#123; <span class="keyword">throw</span> <span class="keyword">new</span> <span class="title class_">Error</span>(ex); &#125;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">volatile</span> <span class="type">int</span> value;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
-
-<p>CAS 更新变量的值的内存变化如下：</p>
-<div style="width:80%;margin:auto"><img src="/2023/12/25/Unsafe-an-anti-Java-class/Pasted%20image%2020231226005107.png" class="" title="CAS 更新变量的值"></div>
-
-<p>配合 <code>ClassLayout</code> 打印 <code>AtomicInteger</code> 的内部结构更直观地感受 <code>offset</code> 的含义：</p>
-<figure class="highlight text"><table><tr><td class="code"><pre><span class="line">java.util.concurrent.atomic.AtomicInteger object internals:</span><br><span class="line">OFF  SZ   TYPE DESCRIPTION               VALUE</span><br><span class="line">  0   8        (object header: mark)     0x0000000000000001 (non-biasable; age: 0)</span><br><span class="line">  8   4        (object header: class)    0xf8003dbc</span><br><span class="line"> 12   4    int AtomicInteger.value       1</span><br><span class="line">Instance size: 16 bytes</span><br><span class="line">Space losses: 0 bytes internal + 0 bytes external = 0 bytes total</span><br></pre></td></tr></table></figure>
-
-
-
-<h2 id="参考文章"><a href="#参考文章" class="headerlink" title="参考文章"></a>参考文章</h2><ul>
-<li><a href="https://tech.meituan.com/2019/02/14/talk-about-java-magic-class-unsafe.html">Java魔法类：Unsafe应用解析</a></li>
-</ul>
-]]></content>
-      <tags>
-        <tag>java</tag>
-      </tags>
-  </entry>
-  <entry>
-    <title>Java 类 Reference 的源码分析</title>
-    <url>/2023/12/27/source-code-analysis-of-Java-class-Reference/</url>
-    <content><![CDATA[<p>我们知道 <code>Java</code> 扩充了“引用”的概念，引入了软引用、弱引用和虚引用，它们都属于 <code>Reference</code> 类型，也都可以配合 <code>ReferenceQueue</code> 使用。你是否好奇常常被一笔带过的“<code>引用对象</code>的处理过程”？你是否在探究 <code>NIO</code> 堆外内存的自动释放时看到了 <code>Cleaner</code> 的关键代码但不太能梳理整个过程？你是否好奇在研究 <code>JVM</code> 时偶尔看到的 <code>Reference Handler</code> 线程？本文将分析 <code>Reference</code> 和 <code>ReferenceQueue</code> 的源码带你理解<code>引用对象</code>的工作机制。</p>
-<span id="more"></span>
-
-<blockquote>
-<p>事实上，个人感觉在无相关前置知识的情况下，单纯看 <code>JDK</code> 的 <code>Java</code> 代码是没办法很好地理解<code>引用对象</code>是如何被添加到<code>引用队列</code>中的。因为 <code>Reference</code> 的 <code>pending</code> 字段的含义和赋值操作是隐藏在 <code>JVM</code> 的 <code>C++</code> 代码中，本文搁置了其中的细节，仅分析 <code>JDK</code> 中相关的 <code>Java</code> 代码。</p>
-</blockquote>
-<h2 id="Reference"><a href="#Reference" class="headerlink" title="Reference"></a>Reference</h2><p><code>Reference</code> 是<code>引用对象</code>的抽象基类。此类定义了所有引用对象通用的操作。由于引用对象是与垃圾收集器密切合作实现的，因此该类可能无法直接子类化。</p>
-<div style="width:70%;margin:auto"><img src="/2023/12/27/source-code-analysis-of-Java-class-Reference/Pasted%20image%2020231227230915.png" class="" title="Reference 相关类图"></div>
-
-<h3 id="构造函数"><a href="#构造函数" class="headerlink" title="构造函数"></a>构造函数</h3><ul>
-<li><code>referent</code>: <code>引用对象</code>关联的对象</li>
-<li><code>queue</code>: <code>引用对象</code>准备注册到的<code>引用队列</code></li>
-</ul>
-<p><code>Reference</code> 提供了两个构造函数，一个需要传入<code>引用队列</code>（<code>ReferenceQueue</code>），一个不需要。如果一个<code>引用对象</code>（<code>Reference</code>）注册到一个<code>引用队列</code>，在检测到关联对象有适当的可达性变化后，垃圾收集器将把该<code>引用对象</code>添加到该引用队列。</p>
-<blockquote>
-<p>“关联对象有适当的可达性变化”并不容易理解，在很多表述中它很容易被简化为“可以被回收”，但是同时我们又拥有另一条规则，即“一个对象是否可回收的判断依据是是否从 <code>Root</code> 对象可达”。在面对 <code>Reference</code> 的子类时，我们有种割裂感，好像一条和谐的规则出现了特殊条例。<a href="/2023/12/28/explore-the-Java-classes-Cleaner-and-Finalizer/" title="探索 Java 类 Cleaner 和 Finalizer">探索 Java 类 Cleaner 和 Finalizer</a></p>
-</blockquote>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line">Reference(T referent) &#123;</span><br><span class="line">    <span class="built_in">this</span>(referent, <span class="literal">null</span>);</span><br><span class="line">&#125;</span><br><span class="line"></span><br><span class="line">Reference(T referent, ReferenceQueue&lt;? <span class="built_in">super</span> T&gt; queue) &#123;</span><br><span class="line">    <span class="built_in">this</span>.referent = referent;</span><br><span class="line">    <span class="comment">// ReferenceQueue.NULL 表示没有注册到引用队列</span></span><br><span class="line">    <span class="built_in">this</span>.queue = (queue == <span class="literal">null</span>) ? ReferenceQueue.NULL : queue;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
-
-<h3 id="属性"><a href="#属性" class="headerlink" title="属性"></a>属性</h3><h4 id="成员变量"><a href="#成员变量" class="headerlink" title="成员变量"></a>成员变量</h4><ul>
-<li><code>referent</code>: <code>引用对象</code>关联的对象，<strong>该对象将被垃圾收集器特殊对待</strong>。我们很难直观地感受何谓“被垃圾收集器特殊对待”，它对应着“在检测到关联对象有适当的可达性变化后，垃圾收集器将把<code>引用对象</code>添加到该引用队列”。</li>
-<li><code>queue</code>: <code>引用对象</code>注册到的<code>引用队列</code></li>
-<li><code>next</code>: 用于指向下一个<code>引用对象</code>，当<code>引用对象</code>已经添加到<code>引用队列</code>中，<code>next</code> 指向<code>引用队列</code>中的下一个<code>引用对象</code></li>
-<li><code>discovered</code>: 用于指向下一个<code>引用对象</code>，用于在全局的 <code>pending</code> 链表中，指向下一个待添加到<code>引用队列</code>的<code>引用对象</code></li>
-</ul>
-<div style="width:60%;margin:auto"><img src="/2023/12/27/source-code-analysis-of-Java-class-Reference/Pasted%20image%2020231227192404.png" class="" title="引用对象"></div>
-
-<h4 id="静态变量"><a href="#静态变量" class="headerlink" title="静态变量"></a>静态变量</h4><blockquote>
-<p>注意：<code>lock</code> 和 <code>pending</code> 是全局共享的。</p>
-</blockquote>
-<ul>
-<li><code>lock</code>: 用于与垃圾收集器同步的对象，<strong>垃圾收集器必须在每个收集周期开始时获取此锁</strong>。因此至关重要的是持有此锁的任何代码必须尽快运行完，不分配新对象并避免调用用户代码。</li>
-<li><code>pending</code>: 等待加入<code>引用队列</code>的<code>引用对象</code>链表。垃圾收集器将<code>引用对象</code>添加到 <code>pending</code> 链表中，而 <code>Reference-Handler</code> 线程将删除它们，并做清理或入队操作。<code>pending</code> 链表受上述 <code>lock</code> 对象的保护，并使用 <code>discovered</code> 字段来链接下一个元素。</li>
-</ul>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">abstract</span> <span class="keyword">class</span> <span class="title class_">Reference</span>&lt;T&gt; &#123;</span><br><span class="line">    <span class="keyword">private</span> T referent;         <span class="comment">/* Treated specially by GC */</span></span><br><span class="line"></span><br><span class="line">    <span class="keyword">volatile</span> ReferenceQueue&lt;? <span class="built_in">super</span> T&gt; queue;</span><br><span class="line">    <span class="meta">@SuppressWarnings(&quot;rawtypes&quot;)</span></span><br><span class="line">    <span class="keyword">volatile</span> Reference next;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">transient</span> <span class="keyword">private</span> Reference&lt;T&gt; discovered;  <span class="comment">/* used by VM */</span></span><br><span class="line"></span><br><span class="line">    <span class="keyword">static</span> <span class="keyword">private</span> <span class="keyword">class</span> <span class="title class_">Lock</span> &#123; &#125;</span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">static</span> <span class="type">Lock</span> <span class="variable">lock</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">Lock</span>();</span><br><span class="line"></span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">static</span> Reference&lt;Object&gt; pending = <span class="literal">null</span>;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
-
-<blockquote>
-<p><code>Reference</code> 其实可以理解为单链表中的一个节点，除了核心的 <code>referent</code> 和 <code>queue</code>，<code>next</code> 和 <code>discovered</code> 都用于指向下一个<code>引用对象</code>，只是分别用于两条不同的单链表上。</p>
-</blockquote>
-<p><code>pending</code> 链表：</p>
-<div style="width:70%;margin:auto"><img src="/2023/12/27/source-code-analysis-of-Java-class-Reference/Pasted%20image%2020231227191324.png" class="" title="pending 链表"></div>
-
-<p><code>ReferenceQueue</code>：</p>
-<div style="width:70%;margin:auto"><img src="/2023/12/27/source-code-analysis-of-Java-class-Reference/Pasted%20image%2020231227191330.png" class="" title="ReferenceQueue"></div>
-
-<h3 id="ReferenceHandler-线程"><a href="#ReferenceHandler-线程" class="headerlink" title="ReferenceHandler 线程"></a>ReferenceHandler 线程</h3><p>启动任意一个非常简单的 <code>Java</code> 程序，通过 <code>JVM</code> 相关的工具，比如 <code>JConsole</code>，你都能看到一个名为 <code>Reference Handler</code> 的线程。</p>
-<div style="width:60%;margin:auto"><img src="/2023/12/27/source-code-analysis-of-Java-class-Reference/Snipaste_2023-12-27_19-41-19.png" class="" title="Reference-Handler 线程"></div>
-
-<p><code>ReferenceHandler</code> 类本身的代码并不复杂。</p>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">private</span> <span class="keyword">static</span> <span class="keyword">class</span> <span class="title class_">ReferenceHandler</span> <span class="keyword">extends</span> <span class="title class_">Thread</span> &#123;</span><br><span class="line">    <span class="comment">// 确保类已经初始化</span></span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">ensureClassInitialized</span><span class="params">(Class&lt;?&gt; clazz)</span> &#123;</span><br><span class="line">        <span class="keyword">try</span> &#123;</span><br><span class="line">            Class.forName(clazz.getName(), <span class="literal">true</span>, clazz.getClassLoader());</span><br><span class="line">        &#125; <span class="keyword">catch</span> (ClassNotFoundException e) &#123;</span><br><span class="line">            <span class="keyword">throw</span> (Error) <span class="keyword">new</span> <span class="title class_">NoClassDefFoundError</span>(e.getMessage()).initCause(e);</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">static</span> &#123;</span><br><span class="line">        <span class="comment">// 预加载和初始化 InterruptedException 和 Cleaner，以避免在 run 方法中懒加载发生内存不足时陷入麻烦（咱也不知道具体啥麻烦）</span></span><br><span class="line">        ensureClassInitialized(InterruptedException.class);</span><br><span class="line">        ensureClassInitialized(Cleaner.class);</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    ReferenceHandler(ThreadGroup g, String name) &#123;</span><br><span class="line">        <span class="built_in">super</span>(g, name);</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">public</span> <span class="keyword">void</span> <span class="title function_">run</span><span class="params">()</span> &#123;</span><br><span class="line">        <span class="comment">// run 方法循环调用 tryHandlePending</span></span><br><span class="line">        <span class="keyword">while</span> (<span class="literal">true</span>) &#123;</span><br><span class="line">            tryHandlePending(<span class="literal">true</span>);</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
-
-<h4 id="创建线程并启动"><a href="#创建线程并启动" class="headerlink" title="创建线程并启动"></a>创建线程并启动</h4><p><code>Reference-Handler</code> 线程是通过静态代码块创建并启动的。</p>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">static</span> &#123;</span><br><span class="line">    <span class="comment">// 不断获取父线程组，直到最高的系统线程组</span></span><br><span class="line">    <span class="type">ThreadGroup</span> <span class="variable">tg</span> <span class="operator">=</span> Thread.currentThread().getThreadGroup();</span><br><span class="line">    <span class="keyword">for</span> (<span class="type">ThreadGroup</span> <span class="variable">tgn</span> <span class="operator">=</span> tg;</span><br><span class="line">            tgn != <span class="literal">null</span>;</span><br><span class="line">            tg = tgn, tgn = tg.getParent());</span><br><span class="line">    <span class="type">Thread</span> <span class="variable">handler</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">ReferenceHandler</span>(tg, <span class="string">&quot;Reference Handler&quot;</span>);</span><br><span class="line">    <span class="comment">// 设置为最高优先级</span></span><br><span class="line">    handler.setPriority(Thread.MAX_PRIORITY);</span><br><span class="line">    <span class="comment">// 设置为守护线程</span></span><br><span class="line">    handler.setDaemon(<span class="literal">true</span>);</span><br><span class="line">    handler.start();</span><br><span class="line"></span><br><span class="line">    <span class="comment">// provide access in SharedSecrets</span></span><br><span class="line">    <span class="comment">// 不懂，看到一个说法覆盖 JVM 的默认处理方式</span></span><br><span class="line">    SharedSecrets.setJavaLangRefAccess(<span class="keyword">new</span> <span class="title class_">JavaLangRefAccess</span>() &#123;</span><br><span class="line">        <span class="meta">@Override</span></span><br><span class="line">        <span class="keyword">public</span> <span class="type">boolean</span> <span class="title function_">tryHandlePendingReference</span><span class="params">()</span> &#123;</span><br><span class="line">            <span class="keyword">return</span> tryHandlePending(<span class="literal">false</span>);</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;);</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
-
-<h4 id="run-处理逻辑"><a href="#run-处理逻辑" class="headerlink" title="run 处理逻辑"></a>run 处理逻辑</h4><p><code>run</code> 方法的核心处理逻辑。本质上，<code>ReferenceHandler</code> 线程将 <code>pending</code> 链表上的<code>引用对象</code>分发到各自注册的<code>引用队列</code>中。如果理解了 <code>Reference</code> 作为单链表节点的一面，这部分代码不难理解，反而是其中应对 <code>OOME</code> 的处理很值得关注，但更多的可能是看了个寂寞，不好重现问题并验证。</p>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">static</span> <span class="type">boolean</span> <span class="title function_">tryHandlePending</span><span class="params">(<span class="type">boolean</span> waitForNotify)</span> &#123;</span><br><span class="line">    Reference&lt;Object&gt; r;</span><br><span class="line">    Cleaner c;</span><br><span class="line">    <span class="keyword">try</span> &#123;</span><br><span class="line">        <span class="comment">// 加锁（和垃圾回收共用一个锁）</span></span><br><span class="line">        <span class="keyword">synchronized</span> (lock) &#123;</span><br><span class="line">            <span class="comment">// 如果不为 null</span></span><br><span class="line">            <span class="keyword">if</span> (pending != <span class="literal">null</span>) &#123;</span><br><span class="line">                <span class="comment">// 获取头节点</span></span><br><span class="line">                r = pending;</span><br><span class="line">                <span class="comment">// instanceof 可能抛出 OutOfMemoryError，因此在把 r 从 pending 链表中移除前进行</span></span><br><span class="line">                <span class="comment">// 如果是 Cleaner 类型，进行类型转换，后续有特殊处理</span></span><br><span class="line">                c = r <span class="keyword">instanceof</span> Cleaner ? (Cleaner) r : <span class="literal">null</span>;</span><br><span class="line">                <span class="comment">// 从 pending 链表移除 r</span></span><br><span class="line">                pending = r.discovered;</span><br><span class="line">                r.discovered = <span class="literal">null</span>;</span><br><span class="line">            &#125; <span class="keyword">else</span> &#123;</span><br><span class="line">                <span class="comment">// 等待锁可能抛出 OutOfMemoryError，因为可能需要分配 exception 对象</span></span><br><span class="line">                <span class="keyword">if</span> (waitForNotify) &#123;</span><br><span class="line">                    lock.wait();</span><br><span class="line">                &#125;</span><br><span class="line">                <span class="comment">// retry if waited</span></span><br><span class="line">                <span class="keyword">return</span> waitForNotify;</span><br><span class="line">            &#125;</span><br><span class="line">        &#125;</span><br><span class="line">    &#125; <span class="keyword">catch</span> (OutOfMemoryError x) &#123;</span><br><span class="line">        <span class="comment">// 给其他线程 CPU 时间，以便它们能够丢弃一些存活的引用，然后通过 GC 回收一些空间</span></span><br><span class="line">        <span class="comment">// 还可以防止 CPU 密集运行以至于上面的“r instanceof Cleaner”在一段时间内持续抛出 OOME</span></span><br><span class="line">        Thread.<span class="keyword">yield</span>();</span><br><span class="line">        <span class="comment">// retry</span></span><br><span class="line">        <span class="keyword">return</span> <span class="literal">true</span>;</span><br><span class="line">    &#125; <span class="keyword">catch</span> (InterruptedException x) &#123;</span><br><span class="line">        <span class="comment">// retry</span></span><br><span class="line">        <span class="keyword">return</span> <span class="literal">true</span>;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 如果是 Cleaner 类型，快速清理并返回</span></span><br><span class="line">    <span class="keyword">if</span> (c != <span class="literal">null</span>) &#123;</span><br><span class="line">        c.clean();</span><br><span class="line">        <span class="keyword">return</span> <span class="literal">true</span>;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 如果 Reference 对象关联了引用队列，则添加到队列</span></span><br><span class="line">    ReferenceQueue&lt;? <span class="built_in">super</span> Object&gt; q = r.queue;</span><br><span class="line">    <span class="keyword">if</span> (q != ReferenceQueue.NULL) q.enqueue(r);</span><br><span class="line">    <span class="keyword">return</span> <span class="literal">true</span>;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
-
-<h3 id="关联对象和队列相关方法"><a href="#关联对象和队列相关方法" class="headerlink" title="关联对象和队列相关方法"></a>关联对象和队列相关方法</h3><figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="comment">/* -- Referent accessor and setters -- */</span></span><br><span class="line"></span><br><span class="line"><span class="comment">// 获取关联对象</span></span><br><span class="line"><span class="keyword">public</span> T <span class="title function_">get</span><span class="params">()</span> &#123;</span><br><span class="line">    <span class="keyword">return</span> <span class="built_in">this</span>.referent;</span><br><span class="line">&#125;</span><br><span class="line"></span><br><span class="line"><span class="comment">// 清理关联对象，该操作不会导致引用对象入队</span></span><br><span class="line"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title function_">clear</span><span class="params">()</span> &#123;</span><br><span class="line">    <span class="built_in">this</span>.referent = <span class="literal">null</span>;</span><br><span class="line">&#125;</span><br><span class="line"></span><br><span class="line"><span class="comment">/* -- Queue operations -- */</span></span><br><span class="line"></span><br><span class="line"><span class="comment">// 判断引用对象是否已入队，如果未关联引用队列，则返回 false</span></span><br><span class="line"><span class="keyword">public</span> <span class="type">boolean</span> <span class="title function_">isEnqueued</span><span class="params">()</span> &#123;</span><br><span class="line">    <span class="keyword">return</span> (<span class="built_in">this</span>.queue == ReferenceQueue.ENQUEUED);</span><br><span class="line">&#125;</span><br><span class="line"></span><br><span class="line"><span class="comment">// 将引用对象添加到其注册的引用队列中，该方法仅 Java 代码调用，JVM 不需要调用本方法可以直接进行入队操作（什么情况下？）</span></span><br><span class="line"><span class="keyword">public</span> <span class="type">boolean</span> <span class="title function_">enqueue</span><span class="params">()</span> &#123;</span><br><span class="line">    <span class="keyword">return</span> <span class="built_in">this</span>.queue.enqueue(<span class="built_in">this</span>);</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
-
-<h2 id="ReferenceQueue"><a href="#ReferenceQueue" class="headerlink" title="ReferenceQueue"></a>ReferenceQueue</h2><p><code>引用队列</code>，在检测到适当的可达性更改后，垃圾收集器将已注册的<code>引用对象</code>添加到该队列。</p>
-<h3 id="属性-1"><a href="#属性-1" class="headerlink" title="属性"></a>属性</h3><figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">class</span> <span class="title class_">ReferenceQueue</span>&lt;T&gt; &#123;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 构造函数</span></span><br><span class="line">    <span class="keyword">public</span> <span class="title function_">ReferenceQueue</span><span class="params">()</span> &#123; &#125;</span><br><span class="line">    </span><br><span class="line">    <span class="comment">// 一个不可入队的队列</span></span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">static</span> <span class="keyword">class</span> <span class="title class_">Null</span>&lt;S&gt; <span class="keyword">extends</span> <span class="title class_">ReferenceQueue</span>&lt;S&gt; &#123;</span><br><span class="line">        <span class="type">boolean</span> <span class="title function_">enqueue</span><span class="params">(Reference&lt;? extends S&gt; r)</span> &#123;</span><br><span class="line">            <span class="keyword">return</span> <span class="literal">false</span>;</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="comment">// 用于表示一个引用对象没有注册到引用队列</span></span><br><span class="line">    <span class="keyword">static</span> ReferenceQueue&lt;Object&gt; NULL = <span class="keyword">new</span> <span class="title class_">Null</span>&lt;&gt;();</span><br><span class="line">    <span class="comment">// 用于表示一个引用对象已经添加到引用队列</span></span><br><span class="line">    <span class="keyword">static</span> ReferenceQueue&lt;Object&gt; ENQUEUED = <span class="keyword">new</span> <span class="title class_">Null</span>&lt;&gt;();</span><br><span class="line">    </span><br><span class="line">    <span class="comment">// 锁对象</span></span><br><span class="line">    <span class="keyword">static</span> <span class="keyword">private</span> <span class="keyword">class</span> <span class="title class_">Lock</span> &#123; &#125;;</span><br><span class="line">    <span class="keyword">private</span> <span class="type">Lock</span> <span class="variable">lock</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">Lock</span>();</span><br><span class="line">    <span class="comment">// 头节点</span></span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">volatile</span> Reference&lt;? <span class="keyword">extends</span> <span class="title class_">T</span>&gt; head = <span class="literal">null</span>;</span><br><span class="line">    <span class="comment">// 队列长度</span></span><br><span class="line">    <span class="keyword">private</span> <span class="type">long</span> <span class="variable">queueLength</span> <span class="operator">=</span> <span class="number">0</span>;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
-
-<h3 id="入队"><a href="#入队" class="headerlink" title="入队"></a>入队</h3><p><code>enqueue</code> 只能由 <code>Reference</code> 类调用。</p>
-<p><code>引用对象</code>的 <code>queue</code> 字段可以表达<code>引用对象</code>的状态：</p>
-<ul>
-<li><code>NULL</code>：表示没有注册到<code>引用队列</code>或者已经从<code>引用队列</code>中移除</li>
-<li><code>ENQUEUED</code>：表示已经添加到<code>引用队列</code></li>
-</ul>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="type">boolean</span> <span class="title function_">enqueue</span><span class="params">(Reference&lt;? extends T&gt; r)</span> &#123;</span><br><span class="line">    <span class="keyword">synchronized</span> (lock) &#123;</span><br><span class="line">        <span class="comment">// 检查引用对象的状态是否可以入队</span></span><br><span class="line">        ReferenceQueue&lt;?&gt; queue = r.queue;</span><br><span class="line">        <span class="keyword">if</span> ((queue == NULL) || (queue == ENQUEUED)) &#123;</span><br><span class="line">            <span class="keyword">return</span> <span class="literal">false</span>;</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="comment">// 检查注册的 queue 和调用的 queue 是否相同</span></span><br><span class="line">        <span class="keyword">assert</span> queue == <span class="built_in">this</span>;</span><br><span class="line">        <span class="comment">// 标记为已入队</span></span><br><span class="line">        r.queue = ENQUEUED;</span><br><span class="line">        <span class="comment">// 头插法，最后一个节点的 next 指向自身（为什么？）</span></span><br><span class="line">        r.next = (head == <span class="literal">null</span>) ? r : head;</span><br><span class="line">        head = r;</span><br><span class="line">        <span class="comment">// 队列长度加一</span></span><br><span class="line">        queueLength++;</span><br><span class="line">        <span class="keyword">if</span> (r <span class="keyword">instanceof</span> FinalReference) &#123;</span><br><span class="line">            sun.misc.VM.addFinalRefCount(<span class="number">1</span>);</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="comment">// 通知等待的线程</span></span><br><span class="line">        lock.notifyAll();</span><br><span class="line">        <span class="keyword">return</span> <span class="literal">true</span>;</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
-
-<h3 id="出队"><a href="#出队" class="headerlink" title="出队"></a>出队</h3><p>轮询队列以查看是否有引用对象可用，如果存在可用的引用对象则将其从队列中删除并返回，否则该方法立即返回 <code>null</code>。</p>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> Reference&lt;? <span class="keyword">extends</span> <span class="title class_">T</span>&gt; poll() &#123;</span><br><span class="line">    <span class="comment">// 缩小锁的范围</span></span><br><span class="line">    <span class="keyword">if</span> (head == <span class="literal">null</span>)</span><br><span class="line">        <span class="keyword">return</span> <span class="literal">null</span>;</span><br><span class="line">    <span class="keyword">synchronized</span> (lock) &#123;</span><br><span class="line">        <span class="keyword">return</span> reallyPoll();</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br><span class="line"></span><br><span class="line"><span class="keyword">private</span> Reference&lt;? <span class="keyword">extends</span> <span class="title class_">T</span>&gt; reallyPoll() &#123;</span><br><span class="line">    Reference&lt;? <span class="keyword">extends</span> <span class="title class_">T</span>&gt; r = head;</span><br><span class="line">    <span class="keyword">if</span> (r != <span class="literal">null</span>) &#123;</span><br><span class="line">        <span class="meta">@SuppressWarnings(&quot;unchecked&quot;)</span></span><br><span class="line">        Reference&lt;? <span class="keyword">extends</span> <span class="title class_">T</span>&gt; rn = r.next;</span><br><span class="line">        <span class="comment">// 因为尾节点的 next 指向自身</span></span><br><span class="line">        head = (rn == r) ? <span class="literal">null</span> : rn;</span><br><span class="line">        <span class="comment">// 标记为 NULL，避免再次入队</span></span><br><span class="line">        r.queue = NULL;</span><br><span class="line">        <span class="comment">// next 指向自己</span></span><br><span class="line">        r.next = r;</span><br><span class="line">        <span class="comment">// 队列长度减一</span></span><br><span class="line">        queueLength--;</span><br><span class="line">        <span class="keyword">if</span> (r <span class="keyword">instanceof</span> FinalReference) &#123;</span><br><span class="line">            sun.misc.VM.addFinalRefCount(-<span class="number">1</span>);</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="keyword">return</span> r;</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="keyword">return</span> <span class="literal">null</span>;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
-
-<p>出队操作提供了等待的选项。</p>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="comment">// 从队列中移除下一个元素，阻塞直到有元素可用。</span></span><br><span class="line"><span class="keyword">public</span> Reference&lt;? <span class="keyword">extends</span> <span class="title class_">T</span>&gt; remove() <span class="keyword">throws</span> InterruptedException &#123;</span><br><span class="line">    <span class="keyword">return</span> remove(<span class="number">0</span>);</span><br><span class="line">&#125;</span><br><span class="line"></span><br><span class="line"><span class="comment">// 从队列中移除下一个元素，阻塞直到超时或有元素可用，timeout 以毫秒为单位。</span></span><br><span class="line"><span class="keyword">public</span> Reference&lt;? <span class="keyword">extends</span> <span class="title class_">T</span>&gt; remove(<span class="type">long</span> timeout)</span><br><span class="line">    <span class="keyword">throws</span> IllegalArgumentException, InterruptedException</span><br><span class="line">&#123;</span><br><span class="line">    <span class="keyword">if</span> (timeout &lt; <span class="number">0</span>) &#123;</span><br><span class="line">        <span class="keyword">throw</span> <span class="keyword">new</span> <span class="title class_">IllegalArgumentException</span>(<span class="string">&quot;Negative timeout value&quot;</span>);</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="keyword">synchronized</span> (lock) &#123;</span><br><span class="line">        Reference&lt;? <span class="keyword">extends</span> <span class="title class_">T</span>&gt; r = reallyPoll();</span><br><span class="line">        <span class="keyword">if</span> (r != <span class="literal">null</span>) <span class="keyword">return</span> r;</span><br><span class="line">        <span class="type">long</span> <span class="variable">start</span> <span class="operator">=</span> (timeout == <span class="number">0</span>) ? <span class="number">0</span> : System.nanoTime();</span><br><span class="line">        <span class="keyword">for</span> (;;) &#123;</span><br><span class="line">            lock.wait(timeout);</span><br><span class="line">            r = reallyPoll();</span><br><span class="line">            <span class="keyword">if</span> (r != <span class="literal">null</span>) <span class="keyword">return</span> r;</span><br><span class="line">            <span class="comment">// 如果 timeout 大于 0</span></span><br><span class="line">            <span class="keyword">if</span> (timeout != <span class="number">0</span>) &#123;</span><br><span class="line">                <span class="type">long</span> <span class="variable">end</span> <span class="operator">=</span> System.nanoTime();</span><br><span class="line">                <span class="comment">// 计算下一轮等待时间</span></span><br><span class="line">                timeout -= (end - start) / <span class="number">1000_000</span>;</span><br><span class="line">                <span class="comment">// 到时间直接返回 null</span></span><br><span class="line">                <span class="keyword">if</span> (timeout &lt;= <span class="number">0</span>) <span class="keyword">return</span> <span class="literal">null</span>;</span><br><span class="line">                <span class="comment">// 更新开始时间</span></span><br><span class="line">                start = end;</span><br><span class="line">            &#125;</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
-
-<h3 id="状态变化"><a href="#状态变化" class="headerlink" title="状态变化"></a>状态变化</h3><p><code>Reference</code> 实例（引用对象）可能处于四种内部状态之一：</p>
-<ul>
-<li><code>Active</code>: 新创建的实例处于 <code>Active</code> 状态，受到垃圾收集器的特殊处理。收集器在检测到<code>关联对象</code>的可达性变为适当状态后的一段时间，会将实例的状态更改为 <code>Pending</code> 或 <code>Inactive</code>，具体取决于实例在创建时是否注册到<code>引用队列</code>中。在前一种情况下，它还会将实例添加到待 <code>pending-Reference</code> 列表中。</li>
-<li><code>Pending</code>: 实例处在 <code>pending-Reference</code> 列表中，等待 <code>Reference-Handler</code> 线程将其加入<code>引用队列</code>。未注册到<code>引用队列</code>的实例永远不会处于这种状态。</li>
-<li><code>Enqueued</code>: 处在创建实例时注册到的<code>引用队列</code>中。当实例从引用队列中删除时，该实例将变为 <code>Inactive</code> 状态。未注册到<code>引用队列</code>的实例永远不会处于这种状态。</li>
-<li><code>Inactive</code>: 没有进一步的操作。一旦实例变为 <code>Inactive</code> 状态，其状态将永远不会再改变。</li>
-</ul>
-<p><code>Reference</code> 实例（引用对象）的状态由 <code>queue</code> 和 <code>next</code> 字段共同表达：</p>
-<ul>
-<li><code>Active</code>: <code>(queue == ReferenceQueue || queue == ReferenceQueue.NULL) &amp;&amp; next == null</code></li>
-<li><code>Pending</code>: <code>queue == ReferenceQueue &amp;&amp; next == this</code></li>
-<li><code>Enqueued</code>: <code>queue == ReferenceQueue.ENQUEUED &amp;&amp; (next == Following || this)</code>（在队列末尾时，<code>next</code> 指向自身，目前没有体现出这么设计的必要性啊？）</li>
-<li><code>Inactive</code>: <code>queue == ReferenceQueue.NULL &amp;&amp; next == this</code></li>
-</ul>
-<div style="width:70%;margin:auto"><img src="/2023/12/27/source-code-analysis-of-Java-class-Reference/Pasted%20image%2020231227235157.png" class="" title="Reference 相关类图"></div>
-
-<h2 id="Reference-的子类"><a href="#Reference-的子类" class="headerlink" title="Reference 的子类"></a>Reference 的子类</h2><h2 id="参考文章"><a href="#参考文章" class="headerlink" title="参考文章"></a>参考文章</h2><ul>
-<li><a href="https://cloud.tencent.com/developer/article/1366147">你不可不知的Java引用类型之——Reference源码解析</a></li>
-<li><a href="https://www.jianshu.com/p/9fd68714c366">Java引用类型之：Reference源码解析</a></li>
-<li><a href="https://juejin.cn/post/6942026483489734693">JVM之Reference源码分析</a></li>
-</ul>
-]]></content>
-      <tags>
-        <tag>java</tag>
-      </tags>
-  </entry>
-  <entry>
-    <title>探索 Java 类 Cleaner 和 Finalizer</title>
-    <url>/2023/12/28/explore-the-Java-classes-Cleaner-and-Finalizer/</url>
-    <content><![CDATA[<p><code>Java</code> 类 <code>Cleaner</code> 和 <code>Finalizer</code> 都实现了一种 <code>finalization</code> 机制，前者更轻量和强大，你可能在了解 <code>NIO</code> 的堆外内存自动释放机制中注意过它；后者为人所诟病，<code>finalize</code> 方法被人强烈反对使用。本文想要解析它们的原因不在于它们实现的功能，而在于它们是 <code>Reference</code> 的具体子类。<br><code>Reference</code> 作为和 <code>GC</code> 紧密联系的类，你可能从很多文字描述中了解过 <code>SoftReference</code>、<code>WeakReference</code> 还有 <code>PhantomReference</code> 但是却很少从代码层面了解过它们，当你牢记“一个对象是否可以被回收的判断依据是它是否从 <code>Root</code> 对象可达”这条规则再面对 <code>Reference</code> 的子类时是否产生过割裂感；你是否好奇过 <code>Finalizer</code> 如何和重写 <code>finalize</code> 方法的类产生联系，本文将从 <code>Cleaner</code> 和 <code>Finalizer</code> 的源码揭示一些你可能已知的结论背后的朴素原理。</p>
-<span id="more"></span>
-
-<blockquote>
-<p>本文的写作动机继承自 <a href="/2023/12/27/source-code-analysis-of-Java-class-Reference/" title="Java 类 Reference 的源码分析">Java 类 Reference 的源码分析</a>，有时候也会自我怀疑研究一个涉及大家极力劝阻使用的 <code>finalize</code> 是否浪费精力，只能说确实如此！要不是半途而废会膈应难受肯定就停了！只能说这个过程确实帮助自己对 <code>Java</code> 引用和 <code>GC</code> 对其的处理有更加深刻的理解。</p>
-</blockquote>
-<h2 id="虚引用之-Cleaner"><a href="#虚引用之-Cleaner" class="headerlink" title="虚引用之 Cleaner"></a>虚引用之 Cleaner</h2><h3 id="虚引用介绍"><a href="#虚引用介绍" class="headerlink" title="虚引用介绍"></a>虚引用介绍</h3><p><code>PhantomReference</code> 对象在垃圾收集器确定其<code>关联对象</code>可以被回收时或可以被回收后一段时间，将被入队。“可以被回收”更明确的描述是“虚引用的<code>关联对象</code>变成 <strong><code>phantom reachable</code></strong> ，即只有虚引用引用了它”。但是和软引用和弱引用不同，<strong>当虚引用入队时并不会被垃圾收集器自动清理（其关联对象）</strong>。一个 <code>phantom reachable</code> 的对象会一直维持原样直到所有虚引用被清理或者它们自身变得不可达。</p>
-<p><code>PhantomReference</code> 的代码非常简单：</p>
-<ol>
-<li><code>PhantomReference</code> 仅提供了一个 <code>public</code> 构造函数，必须提供 <code>ReferenceQueue</code> 参数。它不像 <code>SoftReference</code> 和 <code>WeakReference</code> 可以离开 <code>ReferenceQueue</code> 单独使用，尽管 <code>queue</code> 可以为 <code>null</code>，但是这样做并没有意义。</li>
-<li><code>get()</code> 返回 <code>null</code>，这意味着不能通过 <code>PhantomReference</code> 获取其关联的对象 <code>referent</code>。</li>
-</ol>
-<blockquote>
-<p><code>get()</code> 返回 <code>null</code> 并不是可以随意忽略的事情，它保证了 <code>phantom reachable</code> 对象不会被重新触达和修改（这是为清理工作留出时间吗）。</p>
-</blockquote>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">class</span> <span class="title class_">PhantomReference</span>&lt;T&gt; <span class="keyword">extends</span> <span class="title class_">Reference</span>&lt;T&gt; &#123;</span><br><span class="line">    <span class="keyword">public</span> T <span class="title function_">get</span><span class="params">()</span> &#123;</span><br><span class="line">        <span class="keyword">return</span> <span class="literal">null</span>;</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="keyword">public</span> <span class="title function_">PhantomReference</span><span class="params">(T referent, ReferenceQueue&lt;? <span class="built_in">super</span> T&gt; q)</span> &#123;</span><br><span class="line">        <span class="built_in">super</span>(referent, q);</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
-
-<p>通过以下示例验证 <code>GC</code> 不会自动清理虚引用的关联对象：</p>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">main</span><span class="params">(String[] args)</span> <span class="keyword">throws</span> InterruptedException &#123;</span><br><span class="line">    <span class="type">Scanner</span> <span class="variable">scanner</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">Scanner</span>(System.in);</span><br><span class="line"></span><br><span class="line">    <span class="type">byte</span>[] bytes = <span class="keyword">new</span> <span class="title class_">byte</span>[<span class="number">100</span> * <span class="number">1024</span> * <span class="number">1024</span>];</span><br><span class="line">    ReferenceQueue&lt;<span class="type">byte</span>[]&gt; queue = <span class="keyword">new</span> <span class="title class_">ReferenceQueue</span>&lt;&gt;();</span><br><span class="line">    PhantomReference&lt;<span class="type">byte</span>[]&gt; phantomReference = <span class="keyword">new</span> <span class="title class_">PhantomReference</span>&lt;&gt;(bytes, queue);</span><br><span class="line"></span><br><span class="line">    <span class="type">Thread</span> <span class="variable">thread</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">Thread</span>(() -&gt; &#123;</span><br><span class="line">        <span class="keyword">for</span> (; ; ) &#123;</span><br><span class="line">            <span class="keyword">try</span> &#123;</span><br><span class="line">                Reference&lt;? <span class="keyword">extends</span> <span class="title class_">byte</span>[]&gt; remove = queue.remove(<span class="number">0</span>);</span><br><span class="line">                System.out.println(remove + <span class="string">&quot; enqueued&quot;</span>);</span><br><span class="line">                <span class="comment">// 需要调用 clear 主动清理关联对象，可以验证 gc 后总堆内存占用下降</span></span><br><span class="line">                <span class="comment">// remove.clear();</span></span><br><span class="line">                <span class="comment">// System.gc();</span></span><br><span class="line">            &#125; <span class="keyword">catch</span> (InterruptedException e) &#123;</span><br><span class="line">                System.out.println(Thread.currentThread().getName() + <span class="string">&quot; interrupt&quot;</span>);</span><br><span class="line">                <span class="keyword">break</span>;</span><br><span class="line">            &#125;</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;);</span><br><span class="line">    thread.start();</span><br><span class="line"></span><br><span class="line">    System.out.println(<span class="string">&quot;暂停查看堆内存占用&quot;</span>);</span><br><span class="line">    scanner.next();</span><br><span class="line"></span><br><span class="line">    bytes = <span class="literal">null</span>;</span><br><span class="line">    System.gc();</span><br><span class="line">    System.out.println(<span class="string">&quot;gc 后 sleep 3s，查看总堆内存占用未下降&quot;</span>);</span><br><span class="line">    TimeUnit.SECONDS.sleep(<span class="number">3</span>);</span><br><span class="line"></span><br><span class="line">    scanner.next();</span><br><span class="line">    thread.interrupt();</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
-
-<h3 id="Cleaner-介绍"><a href="#Cleaner-介绍" class="headerlink" title="Cleaner 介绍"></a>Cleaner 介绍</h3><p>虚引用最常用于以比 <code>finalization</code> 更灵活的方式安排清理工作，比如其子类 <code>Cleaner</code> 就是一种基于虚引用的清理器，它比 <code>finalization</code> 更轻量但更强大。<code>Cleaner</code> 追踪其<code>关联对象</code>并封装任意的清理代码，在 <code>GC</code> 检测到其<code>关联对象</code>变成 <code>phantom reachable</code> 后一段时间，<code>Reference-Handler</code> 线程将运行清理代码。同时 <code>Cleaner</code> 可以被直接调用，它是线程安全的并且可以保证清理代码最多运行一次。但是 <code>Cleaner</code> 不是 <code>finalization</code> 的替代品，为了避免阻塞 <code>Reference-Handler</code> 线程，清理代码应极其简单和直接。</p>
-<h3 id="构造函数"><a href="#构造函数" class="headerlink" title="构造函数"></a>构造函数</h3><p><code>Cleaner</code> 的构造函数为 <code>private</code>，仅可通过 <code>create</code> 方法创建实例。</p>
-<ul>
-<li><code>referent</code>: <code>关联对象</code></li>
-<li><code>dummyQueue</code>: 假队列，需要它仅仅是因为 <code>PhantomReference</code> 的构造函数需要一个 <code>queue</code> 参数，但是这个 <code>queue</code> 完全没用，在 <code>Reference</code> 中 <code>Reference-Handler</code> 线程会显式调用 <code>cleaners</code> 而不会执行入队操作。</li>
-</ul>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">class</span> <span class="title class_">Cleaner</span> <span class="keyword">extends</span> <span class="title class_">PhantomReference</span>&lt;Object&gt; &#123;</span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">static</span> <span class="keyword">final</span> ReferenceQueue&lt;Object&gt; dummyQueue = <span class="keyword">new</span> <span class="title class_">ReferenceQueue</span>&lt;&gt;();</span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">final</span> Runnable thunk;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">private</span> <span class="title function_">Cleaner</span><span class="params">(Object referent, Runnable thunk)</span> &#123;</span><br><span class="line">        <span class="built_in">super</span>(referent, dummyQueue);</span><br><span class="line">        <span class="built_in">this</span>.thunk = thunk;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">public</span> <span class="keyword">static</span> Cleaner <span class="title function_">create</span><span class="params">(Object ob, Runnable thunk)</span> &#123;</span><br><span class="line">        <span class="keyword">if</span> (thunk == <span class="literal">null</span>)</span><br><span class="line">            <span class="keyword">return</span> <span class="literal">null</span>;</span><br><span class="line">        <span class="comment">// 添加到 Cleaner 自身维护的双链表</span></span><br><span class="line">        <span class="keyword">return</span> add(<span class="keyword">new</span> <span class="title class_">Cleaner</span>(ob, thunk));</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
-
-<h3 id="添加-cleaner"><a href="#添加-cleaner" class="headerlink" title="添加 cleaner"></a>添加 <code>cleaner</code></h3><ul>
-<li>使用 <code>synchronized</code> 同步</li>
-<li><code>Cleaner</code> 自身维护一个双向链表存储 <code>cleaners</code>，通过静态变量 <code>first</code> 存储头节点，以防止 <code>cleaners</code> 比其<code>关联对象</code>更早被 <code>GC</code>。</li>
-</ul>
-<div style="width:70%;margin:auto"><img src="/2023/12/28/explore-the-Java-classes-Cleaner-and-Finalizer/Pasted%20image%2020231228220806.png" class="" title="Cleaner 双向链表"></div>
-
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="comment">// 头节点</span></span><br><span class="line"><span class="keyword">static</span> <span class="keyword">private</span> <span class="type">Cleaner</span> <span class="variable">first</span> <span class="operator">=</span> <span class="literal">null</span>;</span><br><span class="line"><span class="comment">// 双向指针</span></span><br><span class="line"><span class="keyword">private</span> <span class="type">Cleaner</span> <span class="variable">next</span> <span class="operator">=</span> <span class="literal">null</span>, prev = <span class="literal">null</span>;</span><br><span class="line"><span class="keyword">private</span> <span class="keyword">static</span> <span class="keyword">synchronized</span> Cleaner <span class="title function_">add</span><span class="params">(Cleaner cl)</span> &#123;</span><br><span class="line">    <span class="comment">// 头插法</span></span><br><span class="line">    <span class="keyword">if</span> (first != <span class="literal">null</span>) &#123;</span><br><span class="line">        cl.next = first;</span><br><span class="line">        first.prev = cl;</span><br><span class="line">    &#125;</span><br><span class="line">    first = cl;</span><br><span class="line">    <span class="keyword">return</span> cl;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
-
-<h3 id="clean-方法"><a href="#clean-方法" class="headerlink" title="clean 方法"></a>clean 方法</h3><p>在 <code>Reference</code> 中 <code>Reference-Handler</code> 线程对于 <code>Cleaner</code> 类型的对象，会显式地调用其 <code>clean</code> 方法并返回，而不会将其入队。</p>
-<ol>
-<li>使用 <code>synchronized</code> 同步，从双链表上移除自身</li>
-<li>调用 <code>thunk</code> 的 <code>run</code> 方法</li>
-</ol>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title function_">clean</span><span class="params">()</span> &#123;</span><br><span class="line">    <span class="keyword">if</span> (!remove(<span class="built_in">this</span>))</span><br><span class="line">        <span class="keyword">return</span>;</span><br><span class="line">    <span class="keyword">try</span> &#123;</span><br><span class="line">        thunk.run();</span><br><span class="line">    &#125; <span class="keyword">catch</span> (<span class="keyword">final</span> Throwable x) &#123;</span><br><span class="line">        AccessController.doPrivileged(<span class="keyword">new</span> <span class="title class_">PrivilegedAction</span>&lt;Void&gt;() &#123;</span><br><span class="line">            <span class="keyword">public</span> Void <span class="title function_">run</span><span class="params">()</span> &#123;</span><br><span class="line">                <span class="keyword">if</span> (System.err != <span class="literal">null</span>)</span><br><span class="line">                    <span class="keyword">new</span> <span class="title class_">Error</span>(<span class="string">&quot;Cleaner terminated abnormally&quot;</span>, x).printStackTrace();</span><br><span class="line">                System.exit(<span class="number">1</span>);</span><br><span class="line">                <span class="keyword">return</span> <span class="literal">null</span>;</span><br><span class="line">            &#125;</span><br><span class="line">        &#125;);</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br><span class="line"></span><br><span class="line"><span class="keyword">private</span> <span class="keyword">static</span> <span class="keyword">synchronized</span> <span class="type">boolean</span> <span class="title function_">remove</span><span class="params">(Cleaner cl)</span> &#123;</span><br><span class="line">    <span class="comment">// next 指针指向自身代表已经移除，可以避免重复移除和执行</span></span><br><span class="line">    <span class="keyword">if</span> (cl.next == cl)</span><br><span class="line">        <span class="keyword">return</span> <span class="literal">false</span>;</span><br><span class="line">    <span class="comment">// 更新双链表</span></span><br><span class="line">    <span class="keyword">if</span> (first == cl) &#123;</span><br><span class="line">        <span class="keyword">if</span> (cl.next != <span class="literal">null</span>)</span><br><span class="line">            first = cl.next;</span><br><span class="line">        <span class="keyword">else</span></span><br><span class="line">            first = cl.prev;</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="keyword">if</span> (cl.next != <span class="literal">null</span>)</span><br><span class="line">        cl.next.prev = cl.prev;</span><br><span class="line">    <span class="keyword">if</span> (cl.prev != <span class="literal">null</span>)</span><br><span class="line">        cl.prev.next = cl.next;</span><br><span class="line">    <span class="comment">// 通过将 next 指针指向自身表示已经被移除</span></span><br><span class="line">    cl.next = cl;</span><br><span class="line">    cl.prev = cl;</span><br><span class="line">    <span class="keyword">return</span> <span class="literal">true</span>;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
-
-<h3 id="Cleaner-处理流程"><a href="#Cleaner-处理流程" class="headerlink" title="Cleaner 处理流程"></a>Cleaner 处理流程</h3><ul>
-<li>创建的 <code>Cleaner</code> 对象被 <code>Cleaner</code> 类的双链表直接或间接引用（强引用），因此不会被垃圾回收</li>
-<li>一切的起点仍然是 <code>GC</code> 特殊地对待虚引用的关联对象，当关联对象从 <code>reachable</code> 变成 <code>phantom reachable</code>，<code>GC</code> 将 <code>Cleaner</code> 对象将加入 <code>pending-list</code></li>
-<li><code>Reference-Handler</code> 线程又将其移除并调用 <code>clean</code> 方法</li>
-<li>在调用完毕后，<code>Cleaner</code> 对象变成 <code>unreachable</code> 并最终被垃圾回收，其关联对象也被垃圾回收</li>
+
+<p>测试结果如下：</p>
+<figure class="highlight text"><table><tr><td class="code"><pre><span class="line">OFF  SZ   TYPE DESCRIPTION               VALUE</span><br><span class="line">  0   8        (object header: mark)     0x0000000000000001 (non-biasable; age: 0)</span><br><span class="line"></span><br><span class="line">  0   8        (object header: mark)     0x0000000000000005 (biasable; age: 0)</span><br><span class="line"></span><br><span class="line">  0   8        (object header: mark)     0x0000000000000001 (non-biasable; age: 0)</span><br></pre></td></tr></table></figure>
+
+<ul>
+<li><code>JVM</code> 启动后，<strong>偏向锁尚未激活前</strong>，创建的对象的 <code>Mark Word</code> 的末尾 <code>3</code> 位为 <code>0|01</code>，<code>non-biasable</code>，表示无锁状态（非可偏向的）。</li>
+<li>在 <code>4000</code> 毫秒后，<strong>新创建</strong>的对象的 <code>Mark Word</code> 的末尾 <code>3</code> 位为 <code>1|01</code>，<code>biasable</code>，表示匿名偏向锁（可偏向的）。</li>
+<li><strong>偏向锁尚未激活前</strong>创建的对象的对象头的 <code>Mark Word</code> 的末尾 <code>3</code> 位<strong>仍然</strong>是 <code>0|01</code>。</li>
 </ul>
 <blockquote>
-<p>注意，Cleaner 对象本身在被调用完毕之前始终是被静态变量引用，是 <code>reachable</code> 的，我们讨论的被判定为可回收的、变成 <code>phantom reachable</code> 状态的是关联对象。</p>
+<p>在虚拟机启动后，偏向锁激活前，创建的对象的锁标记位为 <code>1|01</code>，此时记录线程 <code>ID</code> 的 <code>bit</code> 全是 <code>0</code>（代表指向 <code>null</code>），没有偏向任何一个线程，该状态称之为匿名偏向锁。</p>
 </blockquote>
-<div style="width:70%;margin:auto"><img src="/2023/12/28/explore-the-Java-classes-Cleaner-and-Finalizer/Pasted%20image%2020231229012917.png" class="" title="Cleaner 处理流程"></div>
+<h5 id="关闭偏向延迟"><a href="#关闭偏向延迟" class="headerlink" title="关闭偏向延迟"></a>关闭偏向延迟</h5><p>通过以下示例测试关闭偏向延迟：</p>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="comment">// JVM 参数设置为 -XX:BiasedLockingStartupDelay=0</span></span><br><span class="line"><span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">main</span><span class="params">(String[] args)</span> <span class="keyword">throws</span> IOException, InterruptedException &#123;</span><br><span class="line">    log.info(<span class="string">&quot;测试：关闭偏向锁的延迟偏向&quot;</span>);</span><br><span class="line"></span><br><span class="line">    <span class="type">Object</span> <span class="variable">lock</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">Object</span>();</span><br><span class="line">    log.info(<span class="string">&quot;在虚拟机一启动，新创建的对象的对象头的 Mark Word 就是 =====&gt; 匿名偏向锁&quot;</span>);</span><br><span class="line">    log.info(ClassLayout.parseInstance(lock).toPrintable());</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
 
-<blockquote>
-<p>事实上，个人猜测“虚引用的关联对象不像软引用和弱引用会被自动清理”描述的仅仅是一个表象，判断是否要被垃圾回收的根本法则仍然是“对象是否从 <code>Root</code> 对象可达”，软引用和弱引用的<code>关联对象</code>之所以会被垃圾回收是因为它们在加入 <code>pending-list</code> 时被从<code>引用对象</code>断开，否则当<code>引用对象</code>被添加到<code>引用队列</code>时，<code>引用队列</code>如果从 <code>Root</code> 对象可达，将导致<code>关联对象</code>也从 <code>Root</code> 对象可达。在 <code>Reference</code> 的 <code>clear()</code> 的注释中提及该方法只被 <code>Java</code> 代码调用，<code>GC</code> 不需要调用该方法就可以直接清理，肯定是 <code>GC</code> 有直接清理<code>关联对象</code>的场景。同时 <code>Reference</code> 类有一句注释“<code>GC</code> 在检测到<code>关联对象</code>有特定的可达性变化后，将把<code>引用对象</code>添加到<code>引用队列</code>”，它并未将特定的可达性变化直接描述为<code>关联对象</code>变为不可达。目前尚未从 <code>JVM</code> 源代码验证该猜测。</p>
-</blockquote>
-<h2 id="终结引用之-Finalizer"><a href="#终结引用之-Finalizer" class="headerlink" title="终结引用之 Finalizer"></a>终结引用之 Finalizer</h2><p><code>FinalReference</code> 用于实现 <code>finalization</code>，其代码很简单。</p>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">class</span> <span class="title class_">FinalReference</span>&lt;T&gt; <span class="keyword">extends</span> <span class="title class_">Reference</span>&lt;T&gt; &#123;</span><br><span class="line">    <span class="keyword">public</span> <span class="title function_">FinalReference</span><span class="params">(T referent, ReferenceQueue&lt;? <span class="built_in">super</span> T&gt; q)</span> &#123;</span><br><span class="line">        <span class="built_in">super</span>(referent, q);</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+<h5 id="关闭偏向锁"><a href="#关闭偏向锁" class="headerlink" title="关闭偏向锁"></a>关闭偏向锁</h5><p>通过以下示例测试关闭偏向锁：</p>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="comment">// JVM 参数设置为 -XX:-UseBiasedLocking</span></span><br><span class="line"><span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">main</span><span class="params">(String[] args)</span> <span class="keyword">throws</span> InterruptedException &#123;</span><br><span class="line">    log.info(<span class="string">&quot;测试：关闭偏向锁&quot;</span>);</span><br><span class="line"></span><br><span class="line">    <span class="type">Object</span> <span class="variable">lock</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">Object</span>();</span><br><span class="line">    log.info(<span class="string">&quot;Mark Word 初始为 =====&gt; 无锁状态（非可偏向的）&quot;</span>);</span><br><span class="line">    log.info(ClassLayout.parseInstance(lock).toPrintable());</span><br><span class="line"></span><br><span class="line">    log.info(<span class="string">&quot;sleep 4000ms&quot;</span>);</span><br><span class="line">    TimeUnit.MILLISECONDS.sleep(<span class="number">4000</span>);</span><br><span class="line"></span><br><span class="line">    log.info(<span class="string">&quot;即使过了偏向延迟时间，创建的对象的对象头的 Mark Word 仍然是 =====&gt; 无锁状态（非可偏向的）&quot;</span>);</span><br><span class="line">    log.info(ClassLayout.parseInstance(lock).toPrintable());</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
 
-<p>其子类 <code>Finalizer</code> 继承自 <code>FinalReference</code>，<code>Cleaner</code> 在代码设计上和它非常相似。</p>
-<h3 id="构造函数-1"><a href="#构造函数-1" class="headerlink" title="构造函数"></a>构造函数</h3><p><code>Finalizer</code> 的构造函数为 <code>private</code>，仅可通过 <code>register</code> 方法创建实例。</p>
+<p>《Java 并发编程的艺术》中写的是 <code>-XX:-UseBiasedLocking=false</code>，测试中报错：</p>
+<figure class="highlight text"><table><tr><td class="code"><pre><span class="line">Error: Could not create the Java Virtual Machine.</span><br><span class="line">Error: A fatal exception has occurred. Program will exit.</span><br><span class="line">Improperly specified VM option &#x27;UseBiasedLocking=false&#x27;</span><br></pre></td></tr></table></figure>
+
+<p>另外书中说“在关闭偏向锁后程序默认会进入轻量级锁状态”，个人认为可能会让人产生误解，默认在未获取锁时为无锁状态，获取锁将变为轻量级锁状态。</p>
+<h4 id="偏向锁加锁"><a href="#偏向锁加锁" class="headerlink" title="偏向锁加锁"></a>偏向锁加锁</h4><p>当一个线程访问同步块时，先测试 <code>Mark Word</code> 里是否存储着当前线程 <code>ID</code>：</p>
 <ul>
-<li><code>finalizee</code>: <code>关联对象</code>，即重写了 <code>finalize</code> 方法的类的实例</li>
-<li><code>queue</code>: 引用队列</li>
+<li>如果否，则再测试 <code>Mark Word</code> 中偏向锁的标识是否设置成 <code>1</code><ul>
+<li>如果为 <code>0</code>，则说明不是偏向锁状态 &#x3D;&#x3D;&#x3D;&#x3D;&#x3D;&gt; <em>获取偏向锁失败后续处理一</em></li>
+<li>如果为 <code>1</code>，则说明是偏向锁状态，<strong>通过 <code>CAS</code> 操作设置偏向锁</strong><ul>
+<li>如果成功，说明获得偏向锁</li>
+<li>如果失败，说明发生竞争 &#x3D;&#x3D;&#x3D;&#x3D;&#x3D;&gt; <em>获取偏向锁失败后续处理二</em></li>
+</ul>
+</li>
+</ul>
+</li>
+<li>如果是，则说明当前线程就是之前获得偏向锁的线程，此刻再次获得锁</li>
 </ul>
 <blockquote>
-<p>根据注释 <code>register</code> 由 <code>VM</code> 调用，我们可以合理猜测，这里就是重写了 <code>finalize</code> 方法的类的实例和 <code>Finalizer</code> 对象关联的起点。</p>
+<p>在<strong>通过 <code>CAS</code> 操作设置偏向锁</strong>中，<code>Compare</code> 操作是“测试 <code>Mark Word</code> 存储线程 <code>ID</code> 的 <code>bit</code> 是否全部为 <code>0</code>，代表偏向的线程 <code>ID</code> 为 <code>null</code>”，<code>Swap</code> 操作是将当前线程 <code>ID</code> 设置到 <code>Mark Word</code> 的相应位置。</p>
 </blockquote>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">final</span> <span class="keyword">class</span> <span class="title class_">Finalizer</span> <span class="keyword">extends</span> <span class="title class_">FinalReference</span>&lt;Object&gt; &#123;</span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">static</span> ReferenceQueue&lt;Object&gt; queue = <span class="keyword">new</span> <span class="title class_">ReferenceQueue</span>&lt;&gt;();</span><br><span class="line"></span><br><span class="line">    <span class="keyword">private</span> <span class="title function_">Finalizer</span><span class="params">(Object finalizee)</span> &#123;</span><br><span class="line">        <span class="built_in">super</span>(finalizee, queue);</span><br><span class="line">        add();</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="comment">// 由 VM 调用</span></span><br><span class="line">    <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">register</span><span class="params">(Object finalizee)</span> &#123;</span><br><span class="line">        <span class="keyword">new</span> <span class="title class_">Finalizer</span>(finalizee);</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
-
-<h3 id="添加-Finalizer"><a href="#添加-Finalizer" class="headerlink" title="添加 Finalizer"></a>添加 <code>Finalizer</code></h3><ul>
-<li>使用 <code>synchronized</code> 同步</li>
-<li><code>Finalizer</code> 自身维护一个双向链表存储 <code>finalizers</code>，通过静态变量 <code>unfinalized</code> 存储头节点</li>
+<p>补充思考：</p>
+<ul>
+<li>“通过 <code>CAS</code> 操作将当前线程 <code>ID</code> 设置到 <code>Mark Word</code>”在偏向锁状态下是有且仅有一次的“偏向”动作。（此观点存疑，在《Java 并发编程的艺术》一书中有“重新偏向于其他线程”这样的描述，但是关于竞争偏向锁部分的原理难以理解。个人在测试中，不论是持有偏向锁的线程仍存活但已离开同步块，还是已死亡，后续线程都无法再获取到偏向锁，唯一一种不同线程获取到同一个偏向锁的情况是两个线程可以复用同一个局部变量表槽位，它们的 <code>tid</code> 相同，这代表着本质上 <code>Mark Word</code> 并无变化）</li>
+<li>当获得偏向锁的线程离开同步块时，没有“解锁操作”，<code>Mark Word</code> 维持不变。个人也不知道如何更准确地描述这个现象，从 <code>synchronized</code> 的语义来说，进出同步块代表着获取锁和释放锁；但是从偏向锁的实现来说，即便离开同步方法块，它仍然偏向原先获得锁的线程，甚至在讨论偏向锁发生竞争时，书中提到“检查持有偏向锁的线程是否存活”。个人更倾向于使用“撤销锁”一词描述偏向锁面临竞争时的处理，使用“释放锁”描述线程离开同步块时的处理。</li>
+<li>当获得偏向锁的线程再次访问同步块时，简单测试 <code>Mark Word</code> 里存储着当前线程 <code>ID</code>，如果成功即可进入同步块。</li>
+<li>计算过 <code>hashCode</code> 后偏向锁状态会变为其他状态，比如无锁状态，或者升级为轻量级锁甚至重量级锁，这符合 <code>CAS</code> 操作的判断条件。</li>
 </ul>
-<div style="width:70%;margin:auto"><img src="/2023/12/28/explore-the-Java-classes-Cleaner-and-Finalizer/Pasted%20image%2020231228230444.png" class="" title="Finalizer 双向链表"></div>
+<h4 id="偏向锁撤销"><a href="#偏向锁撤销" class="headerlink" title="偏向锁撤销"></a>偏向锁撤销</h4><p>偏向锁使用了一种等到竞争出现才撤销的机制，当获得偏向锁的线程离开同步块时，并没有“解锁操作”，<code>Mark Word</code> 将维持不变。当竞争出现时，从现象上说，如果持有偏向锁的线程已经离开同步块，则锁升级为轻量级锁；如果持有锁的线程尚未离开同步块，则锁直接升级为重量级锁。</p>
+<blockquote>
+<p>关于偏向锁的撤销，其原理晦涩难懂，个人仍有很多疑问：锁记录中存储偏向的线程 <code>ID</code> 的作用，检查持有偏向锁的线程是否存活的作用不符合测试结果，重新偏向于其他线程的复现条件。因为理解有限，不多赘述。</p>
+</blockquote>
+<h4 id="测试偏向锁升级"><a href="#测试偏向锁升级" class="headerlink" title="测试偏向锁升级"></a>测试偏向锁升级</h4><h5 id="匿名偏向锁-偏向锁"><a href="#匿名偏向锁-偏向锁" class="headerlink" title="匿名偏向锁-&gt;偏向锁"></a>匿名偏向锁-&gt;偏向锁</h5><blockquote>
+<p>在一个匿名偏向锁状态的对象第一次被作为锁获取时，<code>Mark Word</code> 就会从匿名偏向锁变成偏向锁，并且再也不会变回到匿名偏向锁。</p>
+</blockquote>
+<p>测试在匿名偏向锁状态下获取锁将变成偏向锁状态：</p>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">main</span><span class="params">(String[] args)</span> <span class="keyword">throws</span> IOException, InterruptedException &#123;</span><br><span class="line">    log.info(<span class="string">&quot;偏向锁基础测试：匿名偏向锁 -&gt; 偏向锁&quot;</span>);</span><br><span class="line"></span><br><span class="line">    log.info(<span class="string">&quot;sleep 4000ms，等待偏向锁激活&quot;</span>);</span><br><span class="line">    TimeUnit.MILLISECONDS.sleep(<span class="number">4000</span>);</span><br><span class="line"></span><br><span class="line">    <span class="type">Object</span> <span class="variable">lock</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">Object</span>();</span><br><span class="line">    log.info(<span class="string">&quot;Mark Word 初始为 =====&gt; 匿名偏向锁&quot;</span>);</span><br><span class="line">    log.info(ClassLayout.parseInstance(lock).toPrintable());</span><br><span class="line"></span><br><span class="line">    <span class="keyword">synchronized</span> (lock) &#123;</span><br><span class="line">        log.info(<span class="string">&quot;&#123;&#125; 获取锁 =====&gt; 偏向锁&quot;</span>, Thread.currentThread().getName());</span><br><span class="line">        log.info(ClassLayout.parseInstance(lock).toPrintable());</span><br><span class="line"></span><br><span class="line">        log.info(<span class="string">&quot;暂停，输入任意字符回车继续，可以使用 jstack 查看线程 tid 和 Mark Word 进行对比&quot;</span>);</span><br><span class="line">        scanner.next();</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    log.info(<span class="string">&quot;偏向锁等到竞争出现才释放锁，因此离开同步方法块后，Mark Word 仍然不变&quot;</span>);</span><br><span class="line">    log.info(ClassLayout.parseInstance(lock).toPrintable());</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
 
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">private</span> <span class="keyword">static</span> <span class="type">Finalizer</span> <span class="variable">unfinalized</span> <span class="operator">=</span> <span class="literal">null</span>;</span><br><span class="line"><span class="keyword">private</span> <span class="keyword">static</span> <span class="keyword">final</span> <span class="type">Object</span> <span class="variable">lock</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">Object</span>();</span><br><span class="line"><span class="keyword">private</span> <span class="type">Finalizer</span> <span class="variable">next</span> <span class="operator">=</span> <span class="literal">null</span>, prev = <span class="literal">null</span>;</span><br><span class="line"></span><br><span class="line"><span class="keyword">private</span> <span class="keyword">void</span> <span class="title function_">add</span><span class="params">()</span> &#123;</span><br><span class="line">    <span class="keyword">synchronized</span> (lock) &#123;</span><br><span class="line">        <span class="keyword">if</span> (unfinalized != <span class="literal">null</span>) &#123;</span><br><span class="line">            <span class="built_in">this</span>.next = unfinalized;</span><br><span class="line">            unfinalized.prev = <span class="built_in">this</span>;</span><br><span class="line">        &#125;</span><br><span class="line">        unfinalized = <span class="built_in">this</span>;</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+<p>测试结果如下：</p>
+<figure class="highlight text"><table><tr><td class="code"><pre><span class="line">2023-12-21 00:34:39 - 偏向锁基础测试：匿名偏向锁 -&gt; 偏向锁</span><br><span class="line">2023-12-21 00:34:39 - sleep 4000ms，等待偏向锁激活</span><br><span class="line">2023-12-21 00:34:43 - Mark Word 初始为 =====&gt; 匿名偏向锁</span><br><span class="line">2023-12-21 00:34:45 - java.lang.Object object internals:</span><br><span class="line">OFF  SZ   TYPE DESCRIPTION               VALUE</span><br><span class="line">  0   8        (object header: mark)     0x0000000000000005 (biasable; age: 0)</span><br><span class="line">  8   4        (object header: class)    0xf80001e5</span><br><span class="line"> 12   4        (object alignment gap)    </span><br><span class="line">Instance size: 16 bytes</span><br><span class="line">Space losses: 0 bytes internal + 4 bytes external = 4 bytes total</span><br><span class="line"></span><br><span class="line">2023-12-21 00:34:45 - main 获取锁 =====&gt; 偏向锁</span><br><span class="line">2023-12-21 00:34:45 - java.lang.Object object internals:</span><br><span class="line">OFF  SZ   TYPE DESCRIPTION               VALUE</span><br><span class="line">  0   8        (object header: mark)     0x0000028761af3005 (biased: 0x00000000a1d86bcc; epoch: 0; age: 0)</span><br><span class="line">  8   4        (object header: class)    0xf80001e5</span><br><span class="line"> 12   4        (object alignment gap)    </span><br><span class="line">Instance size: 16 bytes</span><br><span class="line">Space losses: 0 bytes internal + 4 bytes external = 4 bytes total</span><br><span class="line"></span><br><span class="line">2023-12-21 00:34:45 - 暂停，输入任意字符回车继续，可以使用 jstack 查看线程 tid 和 Mark Word 进行对比</span><br><span class="line">2023-12-21 00:34:55 - 偏向锁等到竞争出现才释放锁，因此离开同步方法块后，Mark Word 仍然不变</span><br><span class="line">2023-12-21 00:34:55 - java.lang.Object object internals:</span><br><span class="line">OFF  SZ   TYPE DESCRIPTION               VALUE</span><br><span class="line">  0   8        (object header: mark)     0x0000028761af3005 (biased: 0x00000000a1d86bcc; epoch: 0; age: 0)</span><br><span class="line">  8   4        (object header: class)    0xf80001e5</span><br><span class="line"> 12   4        (object alignment gap)    </span><br><span class="line">Instance size: 16 bytes</span><br><span class="line">Space losses: 0 bytes internal + 4 bytes external = 4 bytes total</span><br></pre></td></tr></table></figure>
 
-<h3 id="Finalizer-线程"><a href="#Finalizer-线程" class="headerlink" title="Finalizer 线程"></a><code>Finalizer</code> 线程</h3><p><code>finalizers</code> 的清理通常是由一条名为 <code>Finalizer</code> 的线程处理。启动任意一个非常简单的 <code>Java</code> 程序，通过 <code>JVM</code> 相关的工具，比如 <code>JConsole</code>，你都能看到一个名为 <code>Finalizer</code> 的线程。</p>
-<div style="width:70%;margin:auto"><img src="/2023/12/28/explore-the-Java-classes-Cleaner-and-Finalizer/Snipaste_2023-12-28_23-09-21.png" class="" title="Finalizer 线程"></div>
+<p>通过 <code>jstack</code> 获取线程 <code>tid</code>（以 <code>Windows</code> 为例）：</p>
+<figure class="highlight shell"><table><tr><td class="code"><pre><span class="line">jps | findstr &quot;BiasedLockingBaseTest&quot; | ForEach-Object &#123; jstack $_.Split()[0]&#125; | findstr &quot;main&quot;</span><br><span class="line">&quot;main&quot; #1 prio=5 os_prio=0 tid=0x0000028761af3000 nid=0x8668 waiting on condition [0x000000ff7b8ff000]</span><br><span class="line">        at com.moralok.concurrency.ch2.BiasedLockingBaseTest.main(BiasedLockingBaseTest.java:27)</span><br></pre></td></tr></table></figure>
 
-<h4 id="run-方法"><a href="#run-方法" class="headerlink" title="run 方法"></a>run 方法</h4><figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">private</span> <span class="keyword">static</span> <span class="keyword">class</span> <span class="title class_">FinalizerThread</span> <span class="keyword">extends</span> <span class="title class_">Thread</span> &#123;</span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">volatile</span> <span class="type">boolean</span> running;</span><br><span class="line">    FinalizerThread(ThreadGroup g) &#123;</span><br><span class="line">        <span class="built_in">super</span>(g, <span class="string">&quot;Finalizer&quot;</span>);</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="keyword">public</span> <span class="keyword">void</span> <span class="title function_">run</span><span class="params">()</span> &#123;</span><br><span class="line">        <span class="comment">// 防止递归调用 run（什么场景？）</span></span><br><span class="line">        <span class="keyword">if</span> (running)</span><br><span class="line">            <span class="keyword">return</span>;</span><br><span class="line">        <span class="comment">// Finalizer thread 在 System.initializeSystemClass 被调用前启动，等待 JavaLangAccess 可用</span></span><br><span class="line">        <span class="keyword">while</span> (!VM.isBooted()) &#123;</span><br><span class="line">            <span class="comment">// 推迟直到 VM 初始化完成</span></span><br><span class="line">            <span class="keyword">try</span> &#123;</span><br><span class="line">                VM.awaitBooted();</span><br><span class="line">            &#125; <span class="keyword">catch</span> (InterruptedException x) &#123;</span><br><span class="line">                <span class="comment">// 忽略并继续</span></span><br><span class="line">            &#125;</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="keyword">final</span> <span class="type">JavaLangAccess</span> <span class="variable">jla</span> <span class="operator">=</span> SharedSecrets.getJavaLangAccess();</span><br><span class="line">        <span class="comment">// 标记为运行中</span></span><br><span class="line">        running = <span class="literal">true</span>;</span><br><span class="line">        <span class="keyword">for</span> (;;) &#123;</span><br><span class="line">            <span class="keyword">try</span> &#123;</span><br><span class="line">                <span class="comment">// 从队列中移除</span></span><br><span class="line">                <span class="type">Finalizer</span> <span class="variable">f</span> <span class="operator">=</span> (Finalizer)queue.remove();</span><br><span class="line">                <span class="comment">// 调用 runFinalizer</span></span><br><span class="line">                f.runFinalizer(jla);</span><br><span class="line">            &#125; <span class="keyword">catch</span> (InterruptedException x) &#123;</span><br><span class="line">                <span class="comment">// 忽略并继续</span></span><br><span class="line">            &#125;</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+<p>关注 <code>Mark Word</code> 并转换为二进制表达：</p>
+<table>
+<thead>
+<tr>
+<th></th>
+<th>二进制表达</th>
+</tr>
+</thead>
+<tbody><tr>
+<td>匿名偏向锁 <code>Mark Word</code></td>
+<td>00000000000000000000000000000000000000000101</td>
+</tr>
+<tr>
+<td>偏向锁状态 <code>Mark Word</code></td>
+<td>00101000011101100001101011110011000000000101</td>
+</tr>
+<tr>
+<td><code>biased</code></td>
+<td>00000000000010100001110110000110101111001100</td>
+</tr>
+<tr>
+<td><code>main</code> 线程 <code>tid</code></td>
+<td>00101000011101100001101011110011000000000000</td>
+</tr>
+</tbody></table>
+<ul>
+<li><strong>注意</strong>：存储的所谓“线程 <code>ID</code>”并非平时所说的线程 <code>ID</code>，该值左移可以得到 <code>jstack</code> 的返回结果中的 <code>tid</code>，<code>jol-core</code> 打印了一个名为 <code>biased</code> 的值与之相同</li>
+<li>在离开同步方法块后，<code>Mark Word</code> 不变</li>
+</ul>
+<h5 id="偏向锁-轻量级锁"><a href="#偏向锁-轻量级锁" class="headerlink" title="偏向锁-&gt;轻量级锁"></a>偏向锁-&gt;轻量级锁</h5><p>测试当拥有偏向锁的线程已经离开同步块，其他线程尝试获取偏向锁（弱竞争），锁将升级为轻量级锁。</p>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">main</span><span class="params">(String[] args)</span> <span class="keyword">throws</span> InterruptedException &#123;</span><br><span class="line">    <span class="type">Scanner</span> <span class="variable">scanner</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">Scanner</span>(System.in);</span><br><span class="line">    log.info(<span class="string">&quot;测试：当持有偏向锁的线程已经离开同步块，其他线程尝试获取偏向锁时，将获得轻量级锁&quot;</span>);</span><br><span class="line"></span><br><span class="line">    log.info(<span class="string">&quot;sleep 4000ms，等待偏向锁激活&quot;</span>);</span><br><span class="line">    TimeUnit.SECONDS.sleep(<span class="number">4</span>);</span><br><span class="line"></span><br><span class="line">    <span class="type">Object</span> <span class="variable">lock</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">Object</span>();</span><br><span class="line">    log.info(<span class="string">&quot;Mark Word 初始为 =====&gt; 匿名偏向锁&quot;</span>);</span><br><span class="line">    log.info(ClassLayout.parseInstance(lock).toPrintable());</span><br><span class="line"></span><br><span class="line">    <span class="keyword">synchronized</span> (lock) &#123;</span><br><span class="line">        log.info(<span class="string">&quot;第一个线程 &#123;&#125; 获取锁 =====&gt; 偏向锁&quot;</span>, Thread.currentThread().getName());</span><br><span class="line">        log.info(ClassLayout.parseInstance(lock).toPrintable());</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="type">Thread</span> <span class="variable">thread</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">Thread</span>(() -&gt; &#123;</span><br><span class="line">        log.info(<span class="string">&quot;第二个线程 &#123;&#125; 尝试获取锁&quot;</span>, Thread.currentThread().getName());</span><br><span class="line">        log.info(ClassLayout.parseInstance(lock).toPrintable());</span><br><span class="line">        <span class="keyword">synchronized</span> (lock) &#123;</span><br><span class="line">            log.info(<span class="string">&quot;第二个线程 &#123;&#125; 获取锁 =====&gt; 轻量级锁&quot;</span>, Thread.currentThread().getName());</span><br><span class="line">            log.info(ClassLayout.parseInstance(lock).toPrintable());</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;, <span class="string">&quot;thread1&quot;</span>);</span><br><span class="line">    thread.start();</span><br><span class="line">    thread.join();</span><br><span class="line"></span><br><span class="line">    log.info(<span class="string">&quot;离开同步块后轻量级锁释放 =====&gt; 无锁状态（可偏向的）&quot;</span>);</span><br><span class="line">    log.info(ClassLayout.parseInstance(lock).toPrintable());</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
 
-<h4 id="创建和启动"><a href="#创建和启动" class="headerlink" title="创建和启动"></a>创建和启动</h4><p><code>Finalizer</code> 线程是通过静态代码块创建和启动的。</p>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">static</span> &#123;</span><br><span class="line">    <span class="comment">// 向上获取父线程组，直到系统线程组</span></span><br><span class="line">    <span class="type">ThreadGroup</span> <span class="variable">tg</span> <span class="operator">=</span> Thread.currentThread().getThreadGroup();</span><br><span class="line">    <span class="keyword">for</span> (<span class="type">ThreadGroup</span> <span class="variable">tgn</span> <span class="operator">=</span> tg;</span><br><span class="line">            tgn != <span class="literal">null</span>;</span><br><span class="line">            tg = tgn, tgn = tg.getParent());</span><br><span class="line">    <span class="comment">// 创建 FinalizerThread 并启动</span></span><br><span class="line">    <span class="type">Thread</span> <span class="variable">finalizer</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">FinalizerThread</span>(tg);</span><br><span class="line">    <span class="comment">// 设置优先级为最高减 2</span></span><br><span class="line">    finalizer.setPriority(Thread.MAX_PRIORITY - <span class="number">2</span>);</span><br><span class="line">    finalizer.setDaemon(<span class="literal">true</span>);</span><br><span class="line">    finalizer.start();</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+<p>有相关资料提到在拥有偏向锁的线程死亡后，锁可以偏向新的线程，但是验证失败。</p>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">main</span><span class="params">(String[] args)</span> <span class="keyword">throws</span> IOException, InterruptedException &#123;</span><br><span class="line">    log.info(<span class="string">&quot;测试：之前获得偏向锁的线程已死时，新线程获得的仍然是偏向锁&quot;</span>);</span><br><span class="line"></span><br><span class="line">    log.info(<span class="string">&quot;sleep 4000ms，等待偏向锁激活&quot;</span>);</span><br><span class="line">    TimeUnit.MILLISECONDS.sleep(<span class="number">4000</span>);</span><br><span class="line"></span><br><span class="line">    <span class="type">Object</span> <span class="variable">lock</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">Object</span>();</span><br><span class="line">    log.info(<span class="string">&quot;Mark Word 初始为 =====&gt; 匿名偏向锁&quot;</span>);</span><br><span class="line">    log.info(ClassLayout.parseInstance(lock).toPrintable());</span><br><span class="line"></span><br><span class="line">    <span class="type">Thread</span> <span class="variable">thread1</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">Thread</span>(() -&gt; &#123;</span><br><span class="line">        <span class="keyword">synchronized</span> (lock) &#123;</span><br><span class="line">            log.info(<span class="string">&quot;第一个线程 &#123;&#125; 获取锁 =====&gt; 偏向锁&quot;</span>, Thread.currentThread().getName());</span><br><span class="line">            log.info(ClassLayout.parseInstance(lock).toPrintable());</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;, <span class="string">&quot;thread1&quot;</span>);</span><br><span class="line">    thread1.start();</span><br><span class="line"></span><br><span class="line">    <span class="type">Thread</span> <span class="variable">thread2</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">Thread</span>(() -&gt; &#123;</span><br><span class="line">        <span class="keyword">try</span> &#123;</span><br><span class="line">            thread1.join();</span><br><span class="line">        &#125; <span class="keyword">catch</span> (InterruptedException e) &#123;</span><br><span class="line">            <span class="keyword">throw</span> <span class="keyword">new</span> <span class="title class_">RuntimeException</span>(e);</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="type">boolean</span> <span class="variable">alive</span> <span class="operator">=</span> thread1.isAlive();</span><br><span class="line">        log.info(<span class="string">&quot;第一个线程 &#123;&#125; 是否存活 &#123;&#125;&quot;</span>, thread1.getName(), alive);</span><br><span class="line">        log.info(ClassLayout.parseInstance(lock).toPrintable());</span><br><span class="line">        <span class="keyword">synchronized</span> (lock) &#123;</span><br><span class="line">            log.info(<span class="string">&quot;即使第一个线程已死亡，第二个线程 &#123;&#125; 获取锁 =====&gt; 轻量级锁&quot;</span>, Thread.currentThread().getName());</span><br><span class="line">            log.info(ClassLayout.parseInstance(lock).toPrintable());</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;, <span class="string">&quot;thread2&quot;</span>);</span><br><span class="line">    thread2.start();</span><br><span class="line">    thread2.join();</span><br><span class="line"></span><br><span class="line">    log.info(<span class="string">&quot;离开同步块后轻量级锁释放 =====&gt; 无锁状态（可偏向的）&quot;</span>);</span><br><span class="line">    log.info(ClassLayout.parseInstance(lock).toPrintable());</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
 
-<h4 id="获取-Finalizer-并调用"><a href="#获取-Finalizer-并调用" class="headerlink" title="获取 Finalizer 并调用"></a>获取 Finalizer 并调用</h4><figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">private</span> <span class="keyword">void</span> <span class="title function_">runFinalizer</span><span class="params">(JavaLangAccess jla)</span> &#123;</span><br><span class="line">    <span class="keyword">synchronized</span> (<span class="built_in">this</span>) &#123;</span><br><span class="line">        <span class="comment">// 判断是否已经终结过</span></span><br><span class="line">        <span class="keyword">if</span> (hasBeenFinalized()) <span class="keyword">return</span>;</span><br><span class="line">        <span class="comment">// 从双链表上移除</span></span><br><span class="line">        remove();</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="keyword">try</span> &#123;</span><br><span class="line">        <span class="comment">// 获取关联的 finalizee</span></span><br><span class="line">        <span class="type">Object</span> <span class="variable">finalizee</span> <span class="operator">=</span> <span class="built_in">this</span>.get();</span><br><span class="line">        <span class="comment">// 如果不为 null 且不是 Enum 类型</span></span><br><span class="line">        <span class="keyword">if</span> (finalizee != <span class="literal">null</span> &amp;&amp; !(finalizee <span class="keyword">instanceof</span> java.lang.Enum)) &#123;</span><br><span class="line">            <span class="comment">// 调用 invokeFinalize</span></span><br><span class="line">            jla.invokeFinalize(finalizee);</span><br><span class="line">            <span class="comment">// 清理栈槽以降低保守 GC 时误保留的可能性</span></span><br><span class="line">            finalizee = <span class="literal">null</span>;</span><br><span class="line">        &#125;</span><br><span class="line">    &#125; <span class="keyword">catch</span> (Throwable x) &#123; &#125;</span><br><span class="line">    <span class="comment">// 清理关联对象</span></span><br><span class="line">    <span class="built_in">super</span>.clear();</span><br><span class="line">&#125;</span><br><span class="line"></span><br><span class="line"><span class="comment">// 和 Cleaner 类似，使用 next 指向自身表示已被移除</span></span><br><span class="line"><span class="keyword">private</span> <span class="type">boolean</span> <span class="title function_">hasBeenFinalized</span><span class="params">()</span> &#123;</span><br><span class="line">    <span class="keyword">return</span> (next == <span class="built_in">this</span>);</span><br><span class="line">&#125;</span><br><span class="line"></span><br><span class="line"><span class="comment">// 和 Cleaner 类似的处理</span></span><br><span class="line"><span class="keyword">private</span> <span class="keyword">void</span> <span class="title function_">remove</span><span class="params">()</span> &#123;</span><br><span class="line">    <span class="keyword">synchronized</span> (lock) &#123;</span><br><span class="line">        <span class="keyword">if</span> (unfinalized == <span class="built_in">this</span>) &#123;</span><br><span class="line">            <span class="keyword">if</span> (<span class="built_in">this</span>.next != <span class="literal">null</span>) &#123;</span><br><span class="line">                unfinalized = <span class="built_in">this</span>.next;</span><br><span class="line">            &#125; <span class="keyword">else</span> &#123;</span><br><span class="line">                unfinalized = <span class="built_in">this</span>.prev;</span><br><span class="line">            &#125;</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="keyword">if</span> (<span class="built_in">this</span>.next != <span class="literal">null</span>) &#123;</span><br><span class="line">            <span class="built_in">this</span>.next.prev = <span class="built_in">this</span>.prev;</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="keyword">if</span> (<span class="built_in">this</span>.prev != <span class="literal">null</span>) &#123;</span><br><span class="line">            <span class="built_in">this</span>.prev.next = <span class="built_in">this</span>.next;</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="built_in">this</span>.next = <span class="built_in">this</span>;</span><br><span class="line">        <span class="built_in">this</span>.prev = <span class="built_in">this</span>;</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+<h5 id="偏向锁-重量级锁"><a href="#偏向锁-重量级锁" class="headerlink" title="偏向锁-&gt;重量级锁"></a>偏向锁-&gt;重量级锁</h5><p>测试当拥有偏向锁的线程尚未离开同步块，其他线程尝试获取偏向锁（强竞争），锁将升级为重量级锁。</p>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">main</span><span class="params">(String[] args)</span> <span class="keyword">throws</span> InterruptedException &#123;</span><br><span class="line">    <span class="type">Scanner</span> <span class="variable">scanner</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">Scanner</span>(System.in);</span><br><span class="line">    log.info(<span class="string">&quot;测试：当持有偏向锁的线程尚未离开同步块，其他线程尝试获取偏向锁时，将升级为重量级锁&quot;</span>);</span><br><span class="line"></span><br><span class="line">    log.info(<span class="string">&quot;sleep 4000ms，等待偏向锁激活&quot;</span>);</span><br><span class="line">    TimeUnit.SECONDS.sleep(<span class="number">4</span>);</span><br><span class="line"></span><br><span class="line">    <span class="type">Object</span> <span class="variable">lock</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">Object</span>();</span><br><span class="line">    log.info(<span class="string">&quot;Mark Word 初始为 =====&gt; 匿名偏向锁&quot;</span>);</span><br><span class="line">    log.info(ClassLayout.parseInstance(lock).toPrintable());</span><br><span class="line"></span><br><span class="line">    <span class="type">Thread</span> <span class="variable">thread1</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">Thread</span>(() -&gt; &#123;</span><br><span class="line">        <span class="keyword">synchronized</span> (lock) &#123;</span><br><span class="line">            log.info(<span class="string">&quot;第一个线程 &#123;&#125; 获取锁 =====&gt; 偏向锁&quot;</span>, Thread.currentThread().getName());</span><br><span class="line">            log.info(ClassLayout.parseInstance(lock).toPrintable());</span><br><span class="line"></span><br><span class="line">            log.info(<span class="string">&quot;暂停，输入任意字符回车继续&quot;</span>);</span><br><span class="line">            scanner.next();</span><br><span class="line"></span><br><span class="line">            log.info(<span class="string">&quot;第一个线程 &#123;&#125; 持有偏向锁，在同步块内发生竞争 =====&gt; 升级为重量级锁&quot;</span>, Thread.currentThread().getName());</span><br><span class="line">            log.info(ClassLayout.parseInstance(lock).toPrintable());</span><br><span class="line">        &#125;</span><br><span class="line">        log.info(<span class="string">&quot;第一个线程 &#123;&#125; 结束&quot;</span>, Thread.currentThread().getName());</span><br><span class="line">    &#125;, <span class="string">&quot;thread1&quot;</span>);</span><br><span class="line">    thread1.start();</span><br><span class="line"></span><br><span class="line">    TimeUnit.SECONDS.sleep(<span class="number">1</span>);</span><br><span class="line"></span><br><span class="line">    <span class="type">Thread</span> <span class="variable">thread2</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">Thread</span>(() -&gt; &#123;</span><br><span class="line">        log.info(<span class="string">&quot;第二个线程 &#123;&#125; 尝试获取偏向锁失败&quot;</span>, Thread.currentThread().getName());</span><br><span class="line">        <span class="keyword">synchronized</span> (lock) &#123;</span><br><span class="line">            log.info(<span class="string">&quot;第二个线程 &#123;&#125; 获取锁 =====&gt; 重量级锁&quot;</span>, Thread.currentThread().getName());</span><br><span class="line">            log.info(ClassLayout.parseInstance(lock).toPrintable());</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;, <span class="string">&quot;thread2&quot;</span>);</span><br><span class="line">    thread2.start();</span><br><span class="line">    thread2.join();</span><br><span class="line"></span><br><span class="line">    log.info(<span class="string">&quot;即使离开同步块后 =====&gt; 重量级锁&quot;</span>);</span><br><span class="line">    log.info(ClassLayout.parseInstance(lock).toPrintable());</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
 
-<h3 id="finalize-的调用原理"><a href="#finalize-的调用原理" class="headerlink" title="finalize 的调用原理"></a>finalize 的调用原理</h3><p>关于如何调用 <code>finalize</code> 方法涉及不少平时接触不到的代码。</p>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="comment">// 获取 JavaLangAccess</span></span><br><span class="line"><span class="keyword">final</span> <span class="type">JavaLangAccess</span> <span class="variable">jla</span> <span class="operator">=</span> SharedSecrets.getJavaLangAccess();</span><br><span class="line"><span class="comment">// 通过 JavaLangAccess 调用 finalizee 的 finalize 方法</span></span><br><span class="line">jla.invokeFinalize(finalizee);</span><br><span class="line"><span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">setJavaLangAccess</span><span class="params">(JavaLangAccess jla)</span> &#123;</span><br><span class="line">    javaLangAccess = jla;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+<h5 id="偏向锁-偏向锁（特例）"><a href="#偏向锁-偏向锁（特例）" class="headerlink" title="偏向锁-&gt;偏向锁（特例）"></a>偏向锁-&gt;偏向锁（特例）</h5><p>这是一个很奇怪的测试用例，它是在测试中唯一发生不同线程对同一个锁获得偏向锁的情况。但是排查过程中发现两个线程的 <code>tid</code> 相同，猜测是局部变量表槽位复用时有什么优化机制。</p>
+<blockquote>
+<p>卡了我好久，也没有探究到实质的新信息。</p>
+</blockquote>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">main</span><span class="params">(String[] args)</span> <span class="keyword">throws</span> IOException, InterruptedException &#123;</span><br><span class="line">    log.info(<span class="string">&quot;测试：之前获得偏向锁的线程已死时，新线程获得的仍然是偏向锁&quot;</span>);</span><br><span class="line"></span><br><span class="line">    log.info(<span class="string">&quot;sleep 4000ms，等待偏向锁激活&quot;</span>);</span><br><span class="line">    TimeUnit.MILLISECONDS.sleep(<span class="number">4000</span>);</span><br><span class="line"></span><br><span class="line">    <span class="type">Object</span> <span class="variable">lock</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">Object</span>();</span><br><span class="line">    log.info(<span class="string">&quot;Mark Word 初始为 =====&gt; 匿名偏向锁&quot;</span>);</span><br><span class="line">    log.info(ClassLayout.parseInstance(lock).toPrintable());</span><br><span class="line"></span><br><span class="line">    <span class="type">Thread</span> <span class="variable">thread1</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">Thread</span>(() -&gt; &#123;</span><br><span class="line">        <span class="keyword">synchronized</span> (lock) &#123;</span><br><span class="line">            log.info(<span class="string">&quot;第一个线程 &#123;&#125; 获取锁 =====&gt; 偏向锁&quot;</span>, Thread.currentThread().getName());</span><br><span class="line">            log.info(ClassLayout.parseInstance(lock).toPrintable());</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;, <span class="string">&quot;thread1&quot;</span>);</span><br><span class="line">    thread1.start();</span><br><span class="line">    thread1.join();</span><br><span class="line"></span><br><span class="line">    <span class="type">Thread</span> <span class="variable">thread2</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">Thread</span>(() -&gt; &#123;</span><br><span class="line">        <span class="keyword">synchronized</span> (lock) &#123;</span><br><span class="line">            log.info(<span class="string">&quot;第二个线程 &#123;&#125; 获取锁，=====&gt; 偏向锁&quot;</span>, Thread.currentThread().getName());</span><br><span class="line">            log.info(<span class="string">&quot;震惊！！！为什么两个 tid 相同啊，有什么复用机制吗&quot;</span>);</span><br><span class="line">            log.info(ClassLayout.parseInstance(lock).toPrintable());</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;, <span class="string">&quot;thread2&quot;</span>);</span><br><span class="line">    thread2.start();</span><br><span class="line">    thread2.join();</span><br><span class="line"></span><br><span class="line">    log.info(<span class="string">&quot;偏向锁等到竞争出现才释放锁，因此离开同步方法块后，Mark Word 不变&quot;</span>);</span><br><span class="line">    log.info(ClassLayout.parseInstance(lock).toPrintable());</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
 
-<p><code>SharedSecrets</code> 的 <code>javaLangAccess</code> 通过 <code>setJavaLangAccess</code> 设置</p>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">setJavaLangAccess</span><span class="params">(JavaLangAccess jla)</span> &#123;</span><br><span class="line">    javaLangAccess = jla;</span><br><span class="line">&#125;</span><br><span class="line"><span class="keyword">public</span> <span class="keyword">static</span> JavaLangAccess <span class="title function_">getJavaLangAccess</span><span class="params">()</span> &#123;</span><br><span class="line">    <span class="keyword">return</span> javaLangAccess;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+<h5 id="匿名偏向锁状态计算-hashCode"><a href="#匿名偏向锁状态计算-hashCode" class="headerlink" title="匿名偏向锁状态计算 hashCode"></a>匿名偏向锁状态计算 hashCode</h5><p>在匿名偏向锁状态计算 <code>hashCode</code>，锁将变为无锁状态。</p>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">main</span><span class="params">(String[] args)</span> <span class="keyword">throws</span> InterruptedException &#123;</span><br><span class="line">    log.info(<span class="string">&quot;测试：在匿名偏向锁状态计算 hashCode&quot;</span>);</span><br><span class="line"></span><br><span class="line">    log.info(<span class="string">&quot;sleep 4000ms，等待偏向锁激活&quot;</span>);</span><br><span class="line">    TimeUnit.MILLISECONDS.sleep(<span class="number">4000</span>);</span><br><span class="line"></span><br><span class="line">    <span class="type">Object</span> <span class="variable">lock</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">Object</span>();</span><br><span class="line">    log.info(<span class="string">&quot;Mark Word 初始为 =====&gt; 匿名偏向锁&quot;</span>);</span><br><span class="line">    log.info(ClassLayout.parseInstance(lock).toPrintable());</span><br><span class="line"></span><br><span class="line">    <span class="type">int</span> <span class="variable">hashCode</span> <span class="operator">=</span> lock.hashCode();</span><br><span class="line">    log.info(<span class="string">&quot;在计算 hashCode 后：Mark Word =====&gt; 无锁状态（hash|age|0|01）&quot;</span>);</span><br><span class="line">    log.info(ClassLayout.parseInstance(lock).toPrintable());</span><br><span class="line"></span><br><span class="line">    <span class="keyword">synchronized</span> (lock) &#123;</span><br><span class="line">        log.info(<span class="string">&quot;获取锁 =====&gt; 轻量级锁&quot;</span>);</span><br><span class="line">        log.info(ClassLayout.parseInstance(lock).toPrintable());</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    log.info(<span class="string">&quot;离开同步块后轻量级锁释放 =====&gt; 无锁状态（hash|age|0|01）&quot;</span>);</span><br><span class="line">    log.info(ClassLayout.parseInstance(lock).toPrintable());</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
 
-<p><code>setJavaLangAccess</code> 方法在 <code>System</code> 中被调用，<code>javaLangAccess</code> 被设置为一个匿名类实例，其中 <code>invokeFinalize</code> 方法间接调用了传入对象的 <code>finalize</code> 方法。</p>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">private</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">setJavaLangAccess</span><span class="params">()</span> &#123;</span><br><span class="line">    <span class="comment">// Allow privileged classes outside of java.lang</span></span><br><span class="line">    sun.misc.SharedSecrets.setJavaLangAccess(<span class="keyword">new</span> <span class="title class_">sun</span>.misc.JavaLangAccess()&#123;</span><br><span class="line">        <span class="comment">// ...</span></span><br><span class="line">        <span class="keyword">public</span> <span class="keyword">void</span> <span class="title function_">invokeFinalize</span><span class="params">(Object o)</span> <span class="keyword">throws</span> Throwable &#123;</span><br><span class="line">            o.finalize();</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;);</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+<h5 id="偏向锁状态无锁时计算-hashCode"><a href="#偏向锁状态无锁时计算-hashCode" class="headerlink" title="偏向锁状态无锁时计算 hashCode"></a>偏向锁状态无锁时计算 hashCode</h5><p>在偏向锁状态无锁时计算 <code>hashCode</code>，锁将变为无锁状态。</p>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">main</span><span class="params">(String[] args)</span> <span class="keyword">throws</span> InterruptedException &#123;</span><br><span class="line">    log.info(<span class="string">&quot;测试：在偏向锁状态无锁时计算 hashCode&quot;</span>);</span><br><span class="line"></span><br><span class="line">    log.info(<span class="string">&quot;sleep 4000ms，等待偏向锁激活&quot;</span>);</span><br><span class="line">    TimeUnit.MILLISECONDS.sleep(<span class="number">4000</span>);</span><br><span class="line"></span><br><span class="line">    <span class="type">Object</span> <span class="variable">lock</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">Object</span>();</span><br><span class="line">    log.info(<span class="string">&quot;Mark Word 初始为 =====&gt; 匿名偏向锁&quot;</span>);</span><br><span class="line">    log.info(ClassLayout.parseInstance(lock).toPrintable());</span><br><span class="line"></span><br><span class="line">    <span class="keyword">synchronized</span> (lock) &#123;</span><br><span class="line">        log.info(<span class="string">&quot;获取锁 =====&gt; 偏向锁&quot;</span>);</span><br><span class="line">        log.info(ClassLayout.parseInstance(lock).toPrintable());</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="type">int</span> <span class="variable">hashCode</span> <span class="operator">=</span> lock.hashCode();</span><br><span class="line">    log.info(<span class="string">&quot;离开同步块后再计算 hashCode：Mark Word =====&gt; 无锁状态&quot;</span>);</span><br><span class="line">    log.info(ClassLayout.parseInstance(lock).toPrintable());</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
 
-<p><code>System</code> 的 <code>setJavaLangAccess</code> 方法在 <code>initializeSystemClass</code> 方法中被调用。这里正对应着 <code>FinalizerThread</code> 的 <code>run</code> 方法中等待 <code>VM</code> 初始化完成的处理。</p>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="comment">// 初始化 System class，在线程初始化之后调用</span></span><br><span class="line"><span class="keyword">private</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">initializeSystemClass</span><span class="params">()</span> &#123;</span><br><span class="line">    <span class="comment">// ...</span></span><br><span class="line">    <span class="comment">// register shared secrets</span></span><br><span class="line">    setJavaLangAccess();</span><br><span class="line">    <span class="comment">// 通知 wait 的线程</span></span><br><span class="line">    sun.misc.VM.booted();</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+<h5 id="偏向锁状态加锁时计算-hashCode"><a href="#偏向锁状态加锁时计算-hashCode" class="headerlink" title="偏向锁状态加锁时计算 hashCode"></a>偏向锁状态加锁时计算 hashCode</h5><p>在偏向锁状态加锁时计算 <code>hashCode</code>，锁将升级为重量级锁状态。</p>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">main</span><span class="params">(String[] args)</span> <span class="keyword">throws</span> InterruptedException &#123;</span><br><span class="line">    log.info(<span class="string">&quot;测试：在偏向锁状态计算 hashCode&quot;</span>);</span><br><span class="line"></span><br><span class="line">    log.info(<span class="string">&quot;sleep 4000ms，等待偏向锁激活&quot;</span>);</span><br><span class="line">    TimeUnit.MILLISECONDS.sleep(<span class="number">4000</span>);</span><br><span class="line"></span><br><span class="line">    <span class="type">Object</span> <span class="variable">lock</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">Object</span>();</span><br><span class="line">    log.info(<span class="string">&quot;Mark Word 初始为 =====&gt; 匿名偏向锁&quot;</span>);</span><br><span class="line">    log.info(ClassLayout.parseInstance(lock).toPrintable());</span><br><span class="line"></span><br><span class="line">    <span class="keyword">synchronized</span> (lock) &#123;</span><br><span class="line">        log.info(<span class="string">&quot;获取锁 =====&gt; 偏向锁&quot;</span>);</span><br><span class="line">        log.info(ClassLayout.parseInstance(lock).toPrintable());</span><br><span class="line"></span><br><span class="line">        <span class="type">int</span> <span class="variable">hashCode</span> <span class="operator">=</span> lock.hashCode();</span><br><span class="line">        log.info(<span class="string">&quot;在计算 hashCode 后：Mark Word =====&gt; 重量级锁&quot;</span>);</span><br><span class="line">        log.info(ClassLayout.parseInstance(lock).toPrintable());</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    log.info(<span class="string">&quot;即使离开同步块后 =====&gt; 重量级锁&quot;</span>);</span><br><span class="line">    log.info(ClassLayout.parseInstance(lock).toPrintable());</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
 
-<h3 id="Finalizer-的注册时机"><a href="#Finalizer-的注册时机" class="headerlink" title="Finalizer 的注册时机"></a>Finalizer 的注册时机</h3><p>你是否好奇过 <code>JVM</code> 是如何保证 <code>finalize</code> 方法最多被调用一次的？如果曾经猜测过 <code>JVM</code> 可能在对象中留有标记，那么在我们研究过对象的内部结构之后可以确认其中并没有用于记录对象是否已经 <code>finalized</code> 的地方。同时我们注意到 <code>hasBeenFinalized</code> 方法通过 <code>next</code> 指针是否指向自己表示是否已经 <code>finalized</code>。我们可以合理猜测 <code>register</code> 的调用时机是在对象创建时，因此最多仅有一次被注册。</p>
-<p>通过以下示例可以测试：</p>
+<h3 id="轻量级锁"><a href="#轻量级锁" class="headerlink" title="轻量级锁"></a>轻量级锁</h3><h4 id="轻量级锁加锁"><a href="#轻量级锁加锁" class="headerlink" title="轻量级锁加锁"></a>轻量级锁加锁</h4><p>获取偏向锁失败后续处理一（是否是偏向锁为 <code>0</code>）：</p>
 <ul>
-<li>在创建重写了 <code>finalize</code> 方法的类创建对象期间会调用 <code>register</code> 创建并注册 <code>Finalizer</code></li>
-<li>在未重写 <code>finalize</code> 方法的类创建对象期间不会调用<code>register</code></li>
-<li><code>Finalizer</code> 不仅可以保证 <code>finalize</code> 只会被调用一次，甚至不会第二次被添加到 <code>pending-list</code>，因为 <code>runFinalizer</code> 最后调用了 <code>super.clear()</code>，<code>JVM</code> 不会特殊对待复活的对象</li>
+<li>检测锁标志位是否为 <code>01</code> 或者 <code>00</code><ul>
+<li>如果否，则说明是重量级锁状态 &#x3D;&#x3D;&#x3D;&#x3D;&#x3D;&gt; <em>获取轻量级锁失败后续处理一</em></li>
+<li>如果是，则说明是无锁状态或者轻量级锁状态，尝试<strong>通过 <code>CAS</code> 操作设置轻量级锁</strong><ul>
+<li>如果成功，说明获得轻量级锁</li>
+<li>如果失败，说明发生竞争 &#x3D;&#x3D;&#x3D;&#x3D;&#x3D;&gt; <em>获取轻量级锁失败后续处理二</em></li>
 </ul>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">class</span> <span class="title class_">FinalReferenceTest_1</span> &#123;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">static</span> <span class="type">FinalizeObj</span> <span class="variable">save</span> <span class="operator">=</span> <span class="literal">null</span>;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">main</span><span class="params">(String[] args)</span> <span class="keyword">throws</span> InterruptedException &#123;</span><br><span class="line">        System.out.println(<span class="string">&quot;创建 finalize obj，使用 Debug 强制运行到 Finalizer.register&quot;</span>);</span><br><span class="line">        <span class="type">FinalizeObj</span> <span class="variable">finalizeObj</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">FinalizeObj</span>();</span><br><span class="line"></span><br><span class="line">        System.out.println(<span class="string">&quot;gc&quot;</span>);</span><br><span class="line">        finalizeObj = <span class="literal">null</span>;</span><br><span class="line">        System.gc();</span><br><span class="line">        System.out.println(<span class="string">&quot;sleep 1s&quot;</span>);</span><br><span class="line">        TimeUnit.SECONDS.sleep(<span class="number">1</span>);</span><br><span class="line">        save.echo();</span><br><span class="line"></span><br><span class="line">        save = <span class="literal">null</span>;</span><br><span class="line">        System.gc();</span><br><span class="line">        System.out.println(<span class="string">&quot;sleep 1s&quot;</span>);</span><br><span class="line">        TimeUnit.SECONDS.sleep(<span class="number">1</span>);</span><br><span class="line">        System.out.println(save == <span class="literal">null</span>);</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">static</span> <span class="keyword">class</span> <span class="title class_">FinalizeObj</span> &#123;</span><br><span class="line">        FinalizeObj() &#123;</span><br><span class="line">            System.out.println(<span class="string">&quot;SaveSelf created&quot;</span>);</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="meta">@Override</span></span><br><span class="line">        <span class="keyword">protected</span> <span class="keyword">void</span> <span class="title function_">finalize</span><span class="params">()</span> <span class="keyword">throws</span> Throwable &#123;</span><br><span class="line">            System.out.println(<span class="string">&quot;finalized&quot;</span>);</span><br><span class="line">            save = <span class="built_in">this</span>;</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="keyword">public</span> <span class="keyword">void</span> <span class="title function_">echo</span><span class="params">()</span> &#123;</span><br><span class="line">            System.out.println(<span class="string">&quot;I am alive.&quot;</span>);</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
-
+</li>
+</ul>
+</li>
+</ul>
+<blockquote>
+<p>在<strong>通过 <code>CAS</code> 操作设置轻量级锁</strong>中，<code>Compare</code> 操作是“测试 <code>Mark Word</code> 的锁标志位是否为 <code>01</code>，代表处于无锁状态”，<code>Swap</code> 操作是将 <code>Mark Word</code> 复制到栈中锁记录，并将指向栈中锁记录的指针设置到 <code>Mark Word</code> 的相应位置以及修改锁标志位。所谓“栈中锁记录”又称为 <code>Displaced Mark Word</code>，<code>JVM</code> 会在当前线程的栈帧中创建用于存储锁记录的空间，用于在轻量级锁状态下临时存放 <code>Mark Word</code>。</p>
+</blockquote>
+<blockquote>
+<p>在轻量级锁状态下，明确提及了锁记录的作用，但偏向锁状态下，提及锁记录却并未加以解释。</p>
+</blockquote>
+<p>获取偏向锁失败后续处理一：</p>
+<ul>
+<li>已经升级为重量级锁</li>
+</ul>
+<p>获取偏向锁失败后续处理二（通过 <code>CAS</code> 加偏向锁失败）：</p>
+<ul>
+<li>获取锁失败的线程将锁升级为重量级锁，修改 <code>Mark Word</code> 为<code>指向互斥量（重量级锁）的指针|10</code>（这个操作将影响到持有轻量级锁的线程的解锁）</li>
+<li>线程阻塞，等待唤醒</li>
+</ul>
+<p>补充思考：</p>
+<ul>
+<li>有相关资料提及偏向锁并非直接升级到重量级锁，无法验证是否总是有轻量级锁作为中间状态</li>
+<li>轻量级锁面临竞争时升级为重量级锁的过程相比于偏向锁面临竞争时的升级过程，更加容易理解，后者好多细节没有找到令人信服的答案。</li>
+</ul>
+<h4 id="轻量级锁解锁"><a href="#轻量级锁解锁" class="headerlink" title="轻量级锁解锁"></a>轻量级锁解锁</h4><p>轻量级锁解锁时，会通过 <code>CAS</code> 操作解锁，<code>Compare</code> 操作是“测试 <code>Mark Word</code> 的锁标志位是否为 <code>00</code>，代表处于轻量级锁状态，<code>Swap</code> 操作是将栈中锁记录 <code>Dispaced Mark Word</code> 替换回对象头的 <code>Mark Word</code> 以及修改锁标志位。<br>如果 <code>Compare</code> 操作失败，则代表发生竞争，此时锁已经被其他线程升级为重量级锁以及 <code>Mark Word</code> 被修改为<code>指向互斥量（重量级锁）的指针|10</code>。持有轻量级锁的线程会释放锁（直接将 <code>Dispaced Mark Word</code> 替换回 <code>Mark Word</code>？）并唤醒等待的线程，开启新的一轮争抢。</p>
+<h4 id="测试轻量级锁升级"><a href="#测试轻量级锁升级" class="headerlink" title="测试轻量级锁升级"></a>测试轻量级锁升级</h4><h5 id="无锁-轻量级锁"><a href="#无锁-轻量级锁" class="headerlink" title="无锁-&gt;轻量级锁"></a>无锁-&gt;轻量级锁</h5><p>测试在无锁状态下获取锁，锁将变成轻量级锁状态。</p>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">main</span><span class="params">(String[] args)</span> <span class="keyword">throws</span> IOException, InterruptedException &#123;</span><br><span class="line">    <span class="type">Scanner</span> <span class="variable">scanner</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">Scanner</span>(System.in);</span><br><span class="line">    log.info(<span class="string">&quot;轻量级锁基础测试：无锁状态 -&gt; 轻量级锁&quot;</span>);</span><br><span class="line"></span><br><span class="line">    <span class="type">Object</span> <span class="variable">lock</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">Object</span>();</span><br><span class="line">    log.info(<span class="string">&quot;在偏向锁激活之前创建的对象为 =====&gt; 无锁状态（可偏向额）&quot;</span>);</span><br><span class="line">    log.info(ClassLayout.parseInstance(lock).toPrintable());</span><br><span class="line"></span><br><span class="line">    <span class="keyword">synchronized</span> (lock) &#123;</span><br><span class="line">        log.info(<span class="string">&quot;即使是单线程无竞争获取锁，=====&gt; 轻量级锁&quot;</span>);</span><br><span class="line">        log.info(ClassLayout.parseInstance(lock).toPrintable());</span><br><span class="line">        log.info(<span class="string">&quot;暂停，回车继续&quot;</span>);</span><br><span class="line">        scanner.nextLine();</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    log.info(<span class="string">&quot;离开同步块后，-&gt; 无锁状态（可偏向的）&quot;</span>);</span><br><span class="line">    log.info(ClassLayout.parseInstance(lock).toPrintable());</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
 
+<h5 id="无锁状态计算-hashCode"><a href="#无锁状态计算-hashCode" class="headerlink" title="无锁状态计算 hashCode"></a>无锁状态计算 hashCode</h5><p>在无锁状态计算 <code>hashCode</code>，仍然是无锁状态。</p>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">main</span><span class="params">(String[] args)</span> <span class="keyword">throws</span> InterruptedException &#123;</span><br><span class="line">    log.info(<span class="string">&quot;测试：在无锁状态计算 hashCode&quot;</span>);</span><br><span class="line"></span><br><span class="line">    <span class="type">Object</span> <span class="variable">lock</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">Object</span>();</span><br><span class="line">    log.info(<span class="string">&quot;Mark Word 初始为 =====&gt; 无锁状态&quot;</span>);</span><br><span class="line">    log.info(ClassLayout.parseInstance(lock).toPrintable());</span><br><span class="line"></span><br><span class="line">    <span class="type">int</span> <span class="variable">hashCode</span> <span class="operator">=</span> lock.hashCode();</span><br><span class="line">    log.info(<span class="string">&quot;在计算 hashCode 后：Mark Word =====&gt; 无锁状态（hash|age|0|01）&quot;</span>);</span><br><span class="line">    log.info(ClassLayout.parseInstance(lock).toPrintable());</span><br><span class="line"></span><br><span class="line">    <span class="keyword">synchronized</span> (lock) &#123;</span><br><span class="line">        log.info(<span class="string">&quot;获取锁 =====&gt; 轻量级锁&quot;</span>);</span><br><span class="line">        log.info(ClassLayout.parseInstance(lock).toPrintable());</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    log.info(<span class="string">&quot;离开同步块后轻量级锁释放 =====&gt; 无锁状态（hash|age|0|01）&quot;</span>);</span><br><span class="line">    log.info(ClassLayout.parseInstance(lock).toPrintable());</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
 
+<h5 id="轻量级锁加锁时计算-hashCode"><a href="#轻量级锁加锁时计算-hashCode" class="headerlink" title="轻量级锁加锁时计算 hashCode"></a>轻量级锁加锁时计算 hashCode</h5><p>在轻量级锁状态加锁时计算 <code>hashCode</code>，锁将升级为重量级锁状态。</p>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">main</span><span class="params">(String[] args)</span> <span class="keyword">throws</span> InterruptedException &#123;</span><br><span class="line">    log.info(<span class="string">&quot;测试：在轻量级锁状态计算 hashCode&quot;</span>);</span><br><span class="line"></span><br><span class="line">    <span class="type">Object</span> <span class="variable">lock</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">Object</span>();</span><br><span class="line">    log.info(<span class="string">&quot;Mark Word 初始为 =====&gt; 无锁状态&quot;</span>);</span><br><span class="line">    log.info(ClassLayout.parseInstance(lock).toPrintable());</span><br><span class="line"></span><br><span class="line">    <span class="keyword">synchronized</span> (lock) &#123;</span><br><span class="line">        log.info(<span class="string">&quot;获取锁 =====&gt; 轻量级锁&quot;</span>);</span><br><span class="line">        log.info(ClassLayout.parseInstance(lock).toPrintable());</span><br><span class="line"></span><br><span class="line">        <span class="type">int</span> <span class="variable">hashCode</span> <span class="operator">=</span> lock.hashCode();</span><br><span class="line">        log.info(<span class="string">&quot;在计算 hashCode 后：Mark Word =====&gt; 重量级锁&quot;</span>);</span><br><span class="line">        log.info(ClassLayout.parseInstance(lock).toPrintable());</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    log.info(<span class="string">&quot;即使离开同步块后 =====&gt; 重量级锁&quot;</span>);</span><br><span class="line">    log.info(ClassLayout.parseInstance(lock).toPrintable());</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
 
 <h2 id="参考文章"><a href="#参考文章" class="headerlink" title="参考文章"></a>参考文章</h2><ul>
-<li><a href="https://stackoverflow.com/questions/21809922/how-is-an-object-marked-as-finalized-in-java-so-that-the-finalize-method-wouldn">How is an object marked as finalized in Java (so that the finalize method wouldn’t be called the second time)?</a></li>
+<li>《Java 并发编程的艺术》</li>
+<li><a href="https://www.cnblogs.com/FraserYu/p/15743542.html">难搞的偏向锁终于被 Java 移除了</a></li>
+<li><a href="https://stackoverflow.com/questions/60985782/details-about-mark-word-of-java-object-header">Details about mark word of java object header</a></li>
 </ul>
 ]]></content>
       <tags>
         <tag>java</tag>
+        <tag>lock</tag>
+        <tag>synchronized</tag>
       </tags>
   </entry>
   <entry>
-    <title>ComponentScan 扫描路径覆盖的真相</title>
-    <url>/2023/12/11/the-truth-about-override-of-ComponentScan-basePackages/</url>
-    <content><![CDATA[<p><code>@ComponentScan</code> 注解是 <code>Spring</code> 中很常用的注解，用于扫描并加载指定类路径下的 <code>Bean</code>，而 <code>Spring Boot</code> 为了便捷使用 <code>@SpringBootApplication</code> 组合注解集成了 <code>@ComponentScan</code> 的能力。也许你听说过使用后者会覆盖前者中关于包扫描的设置，但你是否质疑过这个“不合常理”的结论？是否好奇过为什么它们不像其他注解在嵌套使用时可以同时生效？又是否好奇过 <code>@SpringBootApplication</code> 可以间接设置 <code>@ComponentScan</code> 属性的原因？本文从源码角度分析 <code>@ComponentScan</code> 的工作原理，揭示它独特的检索算法和注解层次结构中的属性覆盖机制。</p>
+    <title>Unsafe，一个“反 Java”的 class</title>
+    <url>/2023/12/25/Unsafe-an-anti-Java-class/</url>
+    <content><![CDATA[<p><code>Unsafe</code> 类位于 <code>sun.misc</code> 包中，它提供了一组用于执行低级别、不安全操作的方法。尽管 <code>Unsafe</code> 类及其所有方法都是公共的，但它的使用受到限制，因为只有受信任的代码才能获取其实例。这个类通常被用于一些底层的、对性能敏感的操作，比如直接内存访问、<code>CAS</code>（<code>Compare and Swap</code>）操作等。本文将介绍这个“反 <code>Java</code>”的类及其方法的典型使用场景。</p>
 <span id="more"></span>
 
-<ul>
-<li>本文的写作动机继承自<a href="/2023/11/23/source-code-analysis-of-Spring-Configuration-annotation/" title="Spring @Configuration 注解的源码分析">Spring @Configuration 注解的源码分析</a>，处理 <code>@ComponentScan</code> 是处理 <code>@Configuration</code> 过程的一部分。</li>
-</ul>
-<h2 id="入口"><a href="#入口" class="headerlink" title="入口"></a>入口</h2><p>对于标注了 <code>@ComponentScan</code> 注解的配置类，处理过程如下：</p>
-<ul>
-<li>获取 <code>@ComponentScan</code> 的注解属性</li>
-<li>遍历注解属性集合，依次根据其中的信息进行扫描，获取 <code>Bean</code> 定义</li>
-<li>如果获取到的 <code>Bean</code> 定义中有任何其他配置类，将递归解析（处理配置类）</li>
-</ul>
 <blockquote>
-<p>这里和处理 <code>@Import</code> 的过程很像，都出现了递归解析新获得的配置类。</p>
+<p>由于 <code>Unsafe</code> 类涉及到直接内存访问和其他底层操作，使用它需要极大的谨慎，因为它可以绕过 <code>Java</code> 语言的一些安全性和健壮性检查。在正常的应用程序代码中，最好避免直接使用 <code>Unsafe</code> 类，以确保代码的可读性和可维护性。在一些特殊情况下，比如一些高性能库的实现，可能会使用 <code>Unsafe</code> 类来进行一些性能优化。</p>
 </blockquote>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">protected</span> <span class="keyword">final</span> SourceClass <span class="title function_">doProcessConfigurationClass</span><span class="params">(ConfigurationClass configClass, SourceClass sourceClass)</span></span><br><span class="line">        <span class="keyword">throws</span> IOException &#123;</span><br><span class="line">    <span class="comment">// ...</span></span><br><span class="line">    <span class="comment">// 处理任何 @ComponentScan 注解</span></span><br><span class="line">    <span class="comment">// 获取 @ComponentScan 的注解属性，该注解是可重复的</span></span><br><span class="line">    Set&lt;AnnotationAttributes&gt; componentScans = AnnotationConfigUtils.attributesForRepeatable(</span><br><span class="line">            sourceClass.getMetadata(), ComponentScans.class, ComponentScan.class);</span><br><span class="line">    <span class="keyword">if</span> (!componentScans.isEmpty() &amp;&amp;</span><br><span class="line">            !<span class="built_in">this</span>.conditionEvaluator.shouldSkip(sourceClass.getMetadata(), ConfigurationPhase.REGISTER_BEAN)) &#123;</span><br><span class="line">        <span class="comment">// 遍历</span></span><br><span class="line">        <span class="keyword">for</span> (AnnotationAttributes componentScan : componentScans) &#123;</span><br><span class="line">            <span class="comment">// 如果配置类被标注了 @ComponentScan -&gt; 立即扫描</span></span><br><span class="line">            Set&lt;BeanDefinitionHolder&gt; scannedBeanDefinitions =</span><br><span class="line">                    <span class="built_in">this</span>.componentScanParser.parse(componentScan, sourceClass.getMetadata().getClassName());</span><br><span class="line">            <span class="comment">// 检测被扫描到的 Bean 定义中是否有任何其他配置类，如有需要递归解析</span></span><br><span class="line">            <span class="keyword">for</span> (BeanDefinitionHolder holder : scannedBeanDefinitions) &#123;</span><br><span class="line">                <span class="keyword">if</span> (ConfigurationClassUtils.checkConfigurationClassCandidate(</span><br><span class="line">                        holder.getBeanDefinition(), <span class="built_in">this</span>.metadataReaderFactory)) &#123;</span><br><span class="line">                    <span class="comment">// 递归解析配置类</span></span><br><span class="line">                    parse(holder.getBeanDefinition().getBeanClassName(), holder.getBeanName());</span><br><span class="line">                &#125;</span><br><span class="line">            &#125;</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="comment">// ...</span></span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+<blockquote>
+<p>尽管在生产中需要谨慎使用 <code>Unsafe</code>，但是可以在测试中使用它来更真实地接触 <code>Java</code> 对象在内存中的存储结构，验证自己的理论知识。</p>
+</blockquote>
+<h2 id="获取-Unsafe-实例"><a href="#获取-Unsafe-实例" class="headerlink" title="获取 Unsafe 实例"></a>获取 Unsafe 实例</h2><blockquote>
+<p>在 <code>Java 9</code> 及之后的版本中，<code>Unsafe</code> 类中的 <code>getUnsafe()</code> 方法被标记为不安全（<code>Unsafe</code>），不再允许普通的 <code>Java</code> 应用程序代码通过此方法获取 <code>Unsafe</code> 实例。这是为了提高 <code>Java</code> 的安全性，防止滥用 <code>Unsafe</code> 类的功能。</p>
+</blockquote>
+<p>在正常的 <code>Java</code> 应用程序中，获取 <code>Unsafe</code> 实例是不被推荐的，因为它违反了 <code>Java</code> 语言的安全性和封装原则。<code>Unsafe</code> 类的设计本意是为了 <code>Java</code> 库和虚拟机的实现使用，而不是为了普通应用程序开发者使用。<code>Unsafe</code> 对象为调用者提供了执行不安全操作的能力，它可用于在任意内存地址读取和写入数据，因此返回的 <code>Unsafe</code> 对象应由调用者仔细保护。它绝不能传递给不受信任的代码。此类中的大多数方法都是非常低级的，并且对应于少量硬件指令。</p>
+<p>获取 <code>Unsafe</code> 实例的静态方法如下：</p>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="meta">@CallerSensitive</span></span><br><span class="line"><span class="keyword">public</span> <span class="keyword">static</span> Unsafe <span class="title function_">getUnsafe</span><span class="params">()</span> &#123;</span><br><span class="line">    Class&lt;?&gt; caller = Reflection.getCallerClass();</span><br><span class="line">    <span class="comment">// 检查调用方法的类是被引导类加载器所加载</span></span><br><span class="line">    <span class="keyword">if</span> (!VM.isSystemDomainLoader(caller.getClassLoader()))</span><br><span class="line">        <span class="keyword">throw</span> <span class="keyword">new</span> <span class="title class_">SecurityException</span>(<span class="string">&quot;Unsafe&quot;</span>);</span><br><span class="line">    <span class="keyword">return</span> theUnsafe;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
 
-<h2 id="扫描获取-Bean-定义"><a href="#扫描获取-Bean-定义" class="headerlink" title="扫描获取 Bean 定义"></a>扫描获取 Bean 定义</h2><p>我们先跳过“获取 <code>@ComponentScan</code> 的注解属性”的过程，来看“扫描获取 <code>Bean</code> 定义”的过程。扫描是通过 <code>ComponentScanAnnotationParser</code> 的 <code>parse</code> 方法完成的，这个方法很长，但逻辑并不复杂，主要是为 <code>ClassPathBeanDefinitionScanner</code> 设置一些来自 <code>@ComponentScan</code> 的注解属性值，最终执行扫描。<code>ClassPathBeanDefinitionScanner</code> 顾名思义是基于类路径的 <code>Bean</code> 定义扫描器，真正的扫描工作全部委托给了它。在这些设置过程中，我们需要关注 <code>basePackages</code> 的设置：</p>
+<p><code>Unsafe</code> 使用单例模式，可以通过静态方法 <code>getUnsafe</code> 获取 <code>Unsafe</code> 实例，并且调用方法的类为启动类加载器所加载才不会抛出异常。获取 <code>Unsafe</code> 实例有以下两种可行方案：</p>
+<ol>
+<li>通过 <code>-Xbootclasspath/a:$&#123;path&#125;</code> 把调用方法的类所在的 <code>jar</code> 包路径追加到启动类路径中，使该类被启动类加载器加载。关于启动类路径的信息可以参考<a href="https://www.moralok.com/2023/07/13/Java-class-loader-source-code-analysis/#ClassLoader-%E7%9A%84%E6%90%9C%E7%B4%A2%E8%B7%AF%E5%BE%84">Java 类加载器源码分析 | ClassLoader 的搜索路径</a></li>
+<li>通过反射获取 <code>Unsafe</code> 类中的 <code>Unsafe</code> 实例<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">private</span> <span class="keyword">static</span> Unsafe <span class="title function_">getUnsafe</span><span class="params">()</span> &#123;</span><br><span class="line">    <span class="keyword">try</span> &#123;</span><br><span class="line">        <span class="type">Field</span> <span class="variable">f</span> <span class="operator">=</span> Unsafe.class.getDeclaredField(<span class="string">&quot;theUnsafe&quot;</span>);</span><br><span class="line">        f.setAccessible(<span class="literal">true</span>);</span><br><span class="line">        <span class="keyword">return</span> (Unsafe) f.get(<span class="literal">null</span>);</span><br><span class="line">    &#125; <span class="keyword">catch</span> (NoSuchFieldException | IllegalAccessException e) &#123;</span><br><span class="line">        <span class="keyword">throw</span> <span class="keyword">new</span> <span class="title class_">RuntimeException</span>(e);</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure></li>
+</ol>
+<h2 id="内存操作"><a href="#内存操作" class="headerlink" title="内存操作"></a>内存操作</h2><p><code>Unsafe</code> 类中包含了一些关于内存操作的方法，这些方法通常被认为是不安全的，因为它们可以绕过 <code>Java</code> 语言的内置安全性和类型检查。以下是一些常见的 <code>Unsafe</code> 类中关于内存操作的方法：</p>
 <ul>
-<li>使用 Set 存储合并结果，用于去重</li>
-<li>获取设置的 <code>basePackages</code> 值并添加</li>
-<li>获取设置的 <code>basePackageClasses</code> 值，转换为它们所在的包名并添加</li>
-<li>如果结果集现在还是空的，获取被标注的配置类所在的包名并添加</li>
+<li><code>allocateMemory</code>: 分配一个给定大小（以字节为单位）的本地内存块，内容未初始化，通常是垃圾。生成的本地指针永远不会为零，并且将针对所有类型进行对齐。<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">native</span> <span class="type">long</span> <span class="title function_">allocateMemory</span><span class="params">(<span class="type">long</span> bytes)</span>;</span><br></pre></td></tr></table></figure></li>
+<li><code>reallocateMemory</code>: 将本地内存块的大小调整为给定大小（以字节为单位），超过旧内存块大小的内容未初始化，通常是垃圾。当且仅当请求的大小为零时，生成的本地指针才为零。传递给此方法的地址可能为空，在这种情况下将执行分配。<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">native</span> <span class="type">long</span> <span class="title function_">reallocateMemory</span><span class="params">(<span class="type">long</span> address, <span class="type">long</span> bytes)</span>;</span><br></pre></td></tr></table></figure></li>
+<li><code>freeMemory</code>: 释放之前由 <code>allocateMemory</code> 或 <code>reallocateMemory</code> 分配的内存。<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">native</span> <span class="keyword">void</span> <span class="title function_">freeMemory</span><span class="params">(<span class="type">long</span> address)</span>;</span><br></pre></td></tr></table></figure></li>
+<li><code>setMemory</code>: 将给定内存块中的所有字节设置为固定值（通常为零）。<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">native</span> <span class="keyword">void</span> <span class="title function_">setMemory</span><span class="params">(Object o, <span class="type">long</span> offset, <span class="type">long</span> bytes, <span class="type">byte</span> value)</span>;</span><br><span class="line"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title function_">setMemory</span><span class="params">(<span class="type">long</span> address, <span class="type">long</span> bytes, <span class="type">byte</span> value)</span> &#123;</span><br><span class="line">    setMemory(<span class="literal">null</span>, address, bytes, value);</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure></li>
+<li><code>copyMemory</code>: 复制指定长度的内存块<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">native</span> <span class="keyword">void</span> <span class="title function_">copyMemory</span><span class="params">(Object srcBase, <span class="type">long</span> srcOffset, Object destBase, <span class="type">long</span> destOffset, <span class="type">long</span> bytes)</span>;</span><br></pre></td></tr></table></figure></li>
+<li><code>putXxx</code>: 将指定偏移量处的内存设置为指定的值，其中 <code>Xxx</code> 可以是 <code>Object</code>、<code>int</code>、<code>long</code>、<code>float</code> 和 <code>double</code> 等。<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">native</span> <span class="keyword">void</span> <span class="title function_">putObject</span><span class="params">(Object o, <span class="type">long</span> offset, Object x)</span>;</span><br></pre></td></tr></table></figure></li>
+<li><code>getXxx</code>: 从指定偏移量处的内存读取值，其中 <code>Xxx</code> 可以是 <code>Object</code>、<code>int</code>、<code>long</code>、<code>float</code> 和 <code>double</code> 等。<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">native</span> Object <span class="title function_">getObject</span><span class="params">(Object o, <span class="type">long</span> offset)</span>;</span><br></pre></td></tr></table></figure></li>
+<li><code>putXxx</code> 和 <code>getXxx</code> 也提供了按绝对基地址操作内存的方法。<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">native</span> <span class="type">byte</span> <span class="title function_">getByte</span><span class="params">(<span class="type">long</span> address)</span>;</span><br><span class="line"><span class="keyword">public</span> <span class="keyword">native</span> <span class="keyword">void</span> <span class="title function_">putByte</span><span class="params">(<span class="type">long</span> address, <span class="type">byte</span> x)</span>;</span><br></pre></td></tr></table></figure></li>
 </ul>
+<p>从内存读取值时，除非满足以下情况之一，否则结果不确定：</p>
+<ol>
+<li>偏移量是通过 <code>objectFieldOffset</code> 从字段的 <code>Field</code> 对象获取的，<code>o</code> 指向的对象的类与字段所属的类兼容。</li>
+<li>偏移量和 <code>o</code> 指向的对象（无论是否为 <code>null</code>）分别是通过 <code>staticFieldOffset</code> 和 <code>staticFieldBase</code> 从 <code>Field</code> 对象获得的。</li>
+<li><code>o</code> 指向的是一个数组，偏移量是一个形式为 <code>B+N*S</code> 的整数，其中 <code>N</code> 是数组的有效索引，<code>B</code> 和 <code>S</code> 分别是通过 <code>arrayBaseOffset</code> 和 <code>arrayIndexScale</code> 获得的值。</li>
+</ol>
 <blockquote>
-<p>最后一条规则就是“默认情况下扫描配置类所在的包”的说法由来，并且根据代码可知，如果主动设置了值，这条规则就不起作用了。</p>
+<p>做一些“不确定”的测试，比如使用 <code>byte</code> 相关的方法操作 <code>int</code> 所在的内存块，是有意思且有帮助的，了解如何破坏，也可以更好地学习如何保护。</p>
 </blockquote>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> Set&lt;BeanDefinitionHolder&gt; <span class="title function_">parse</span><span class="params">(AnnotationAttributes componentScan, <span class="keyword">final</span> String declaringClass)</span> &#123;</span><br><span class="line">    Assert.state(<span class="built_in">this</span>.environment != <span class="literal">null</span>, <span class="string">&quot;Environment must not be null&quot;</span>);</span><br><span class="line">    Assert.state(<span class="built_in">this</span>.resourceLoader != <span class="literal">null</span>, <span class="string">&quot;ResourceLoader must not be null&quot;</span>);</span><br><span class="line">    <span class="comment">// 创建 ClassPathBeanDefinitionScanner</span></span><br><span class="line">    <span class="type">ClassPathBeanDefinitionScanner</span> <span class="variable">scanner</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">ClassPathBeanDefinitionScanner</span>(<span class="built_in">this</span>.registry,</span><br><span class="line">            componentScan.getBoolean(<span class="string">&quot;useDefaultFilters&quot;</span>), <span class="built_in">this</span>.environment, <span class="built_in">this</span>.resourceLoader);</span><br><span class="line">    <span class="comment">// Bean 名称生成器</span></span><br><span class="line">    Class&lt;? <span class="keyword">extends</span> <span class="title class_">BeanNameGenerator</span>&gt; generatorClass = componentScan.getClass(<span class="string">&quot;nameGenerator&quot;</span>);</span><br><span class="line">    <span class="type">boolean</span> <span class="variable">useInheritedGenerator</span> <span class="operator">=</span> (BeanNameGenerator.class == generatorClass);</span><br><span class="line">    scanner.setBeanNameGenerator(useInheritedGenerator ? <span class="built_in">this</span>.beanNameGenerator :</span><br><span class="line">            BeanUtils.instantiateClass(generatorClass));</span><br><span class="line"></span><br><span class="line">    <span class="type">ScopedProxyMode</span> <span class="variable">scopedProxyMode</span> <span class="operator">=</span> componentScan.getEnum(<span class="string">&quot;scopedProxy&quot;</span>);</span><br><span class="line">    <span class="keyword">if</span> (scopedProxyMode != ScopedProxyMode.DEFAULT) &#123;</span><br><span class="line">        scanner.setScopedProxyMode(scopedProxyMode);</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="keyword">else</span> &#123;</span><br><span class="line">        Class&lt;? <span class="keyword">extends</span> <span class="title class_">ScopeMetadataResolver</span>&gt; resolverClass = componentScan.getClass(<span class="string">&quot;scopeResolver&quot;</span>);</span><br><span class="line">        scanner.setScopeMetadataResolver(BeanUtils.instantiateClass(resolverClass));</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    scanner.setResourcePattern(componentScan.getString(<span class="string">&quot;resourcePattern&quot;</span>));</span><br><span class="line">    <span class="comment">// 设置 Filter</span></span><br><span class="line">    <span class="keyword">for</span> (AnnotationAttributes filter : componentScan.getAnnotationArray(<span class="string">&quot;includeFilters&quot;</span>)) &#123;</span><br><span class="line">        <span class="keyword">for</span> (TypeFilter typeFilter : typeFiltersFor(filter)) &#123;</span><br><span class="line">            scanner.addIncludeFilter(typeFilter);</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="keyword">for</span> (AnnotationAttributes filter : componentScan.getAnnotationArray(<span class="string">&quot;excludeFilters&quot;</span>)) &#123;</span><br><span class="line">        <span class="keyword">for</span> (TypeFilter typeFilter : typeFiltersFor(filter)) &#123;</span><br><span class="line">            scanner.addExcludeFilter(typeFilter);</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="comment">// 是否懒加载</span></span><br><span class="line">    <span class="type">boolean</span> <span class="variable">lazyInit</span> <span class="operator">=</span> componentScan.getBoolean(<span class="string">&quot;lazyInit&quot;</span>);</span><br><span class="line">    <span class="keyword">if</span> (lazyInit) &#123;</span><br><span class="line">        scanner.getBeanDefinitionDefaults().setLazyInit(<span class="literal">true</span>);</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="comment">// 设置 basePackages（使用 Set 去重）</span></span><br><span class="line">    Set&lt;String&gt; basePackages = <span class="keyword">new</span> <span class="title class_">LinkedHashSet</span>&lt;String&gt;();</span><br><span class="line">    <span class="comment">// 获取设置的 basePackages 值</span></span><br><span class="line">    String[] basePackagesArray = componentScan.getStringArray(<span class="string">&quot;basePackages&quot;</span>);</span><br><span class="line">    <span class="keyword">for</span> (String pkg : basePackagesArray) &#123;</span><br><span class="line">        <span class="comment">// 允许占位符</span></span><br><span class="line">        String[] tokenized = StringUtils.tokenizeToStringArray(<span class="built_in">this</span>.environment.resolvePlaceholders(pkg),</span><br><span class="line">                ConfigurableApplicationContext.CONFIG_LOCATION_DELIMITERS);</span><br><span class="line">        basePackages.addAll(Arrays.asList(tokenized));</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="comment">// 获取 basePackageClasses，本质上是为了获取它们所在的包名</span></span><br><span class="line">    <span class="keyword">for</span> (Class&lt;?&gt; clazz : componentScan.getClassArray(<span class="string">&quot;basePackageClasses&quot;</span>)) &#123;</span><br><span class="line">        basePackages.add(ClassUtils.getPackageName(clazz));</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="comment">// 如果为空，获取被标注的配置类所在的包名</span></span><br><span class="line">    <span class="keyword">if</span> (basePackages.isEmpty()) &#123;</span><br><span class="line">        basePackages.add(ClassUtils.getPackageName(declaringClass));</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="comment">// 排除被标注的配置类本身</span></span><br><span class="line">    scanner.addExcludeFilter(<span class="keyword">new</span> <span class="title class_">AbstractTypeHierarchyTraversingFilter</span>(<span class="literal">false</span>, <span class="literal">false</span>) &#123;</span><br><span class="line">        <span class="meta">@Override</span></span><br><span class="line">        <span class="keyword">protected</span> <span class="type">boolean</span> <span class="title function_">matchClassName</span><span class="params">(String className)</span> &#123;</span><br><span class="line">            <span class="keyword">return</span> declaringClass.equals(className);</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;);</span><br><span class="line">    <span class="comment">// 执行扫描</span></span><br><span class="line">    <span class="keyword">return</span> scanner.doScan(StringUtils.toStringArray(basePackages));</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+<h3 id="分配堆外内存"><a href="#分配堆外内存" class="headerlink" title="分配堆外内存"></a>分配堆外内存</h3><p>在 <code>Java NIO</code>（<code>New I/O</code>）中，分配堆外内存使用了 <code>Unsafe</code> 类的 <code>allocateMemory</code> 方法。堆外内存是一种在 <code>Java</code> 虚拟机之外分配的内存，它不受 <code>Java</code> 堆内存管理机制的控制。这种内存分配的主要目的是提高 <code>I/O</code> 操作的性能，因为它可以直接与底层操作系统进行交互，而不涉及 <code>Java</code> 堆内存的复杂性。Java 虚拟机的垃圾回收器虽然不直接管理这块内存，但是它通过一种称为“引用清理”（<code>Reference Counting</code>）的机制来处理。</p>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line">DirectByteBuffer(<span class="type">int</span> cap) &#123;</span><br><span class="line">    <span class="built_in">super</span>(-<span class="number">1</span>, <span class="number">0</span>, cap, cap);</span><br><span class="line">    <span class="type">boolean</span> <span class="variable">pa</span> <span class="operator">=</span> VM.isDirectMemoryPageAligned();</span><br><span class="line">    <span class="type">int</span> <span class="variable">ps</span> <span class="operator">=</span> Bits.pageSize();</span><br><span class="line">    <span class="type">long</span> <span class="variable">size</span> <span class="operator">=</span> Math.max(<span class="number">1L</span>, (<span class="type">long</span>)cap + (pa ? ps : <span class="number">0</span>));</span><br><span class="line">    Bits.reserveMemory(size, cap);</span><br><span class="line"></span><br><span class="line">    <span class="type">long</span> <span class="variable">base</span> <span class="operator">=</span> <span class="number">0</span>;</span><br><span class="line">    <span class="keyword">try</span> &#123;</span><br><span class="line">        <span class="comment">// 分配本地内存</span></span><br><span class="line">        base = unsafe.allocateMemory(size);</span><br><span class="line">    &#125; <span class="keyword">catch</span> (OutOfMemoryError x) &#123;</span><br><span class="line">        Bits.unreserveMemory(size, cap);</span><br><span class="line">        <span class="keyword">throw</span> x;</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="comment">// 初始化本地内存</span></span><br><span class="line">    unsafe.setMemory(base, size, (<span class="type">byte</span>) <span class="number">0</span>);</span><br><span class="line">    <span class="keyword">if</span> (pa &amp;&amp; (base % ps != <span class="number">0</span>)) &#123;</span><br><span class="line">        <span class="comment">// Round up to page boundary</span></span><br><span class="line">        address = base + ps - (base &amp; (ps - <span class="number">1</span>));</span><br><span class="line">    &#125; <span class="keyword">else</span> &#123;</span><br><span class="line">        address = base;</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="comment">// 使用虚引用 Cleaner 对象跟踪 DirectByteBuffer 对象的垃圾回收</span></span><br><span class="line">    cleaner = Cleaner.create(<span class="built_in">this</span>, <span class="keyword">new</span> <span class="title class_">Deallocator</span>(base, size, cap));</span><br><span class="line">    att = <span class="literal">null</span>;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<p>当 <code>DirectByteBuffer</code> 对象仅被 <code>Cleaner</code> 对象（虚引用）引用时，它可以在任意一次 <code>GC</code> 中被垃圾回收。在 <code>DirectByteBuffer</code> 对象被垃圾回收后，<code>Cleaner</code> 对象会被加入到引用队列，<code>ReferenceHandler</code> 线程将调用 <code>Deallocator</code> 对象的 <code>run</code> 方法，从而实现本地内存的自动释放。</p>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">private</span> <span class="keyword">static</span> <span class="keyword">class</span> <span class="title class_">Deallocator</span> <span class="keyword">implements</span> <span class="title class_">Runnable</span> &#123;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">static</span> <span class="type">Unsafe</span> <span class="variable">unsafe</span> <span class="operator">=</span> Unsafe.getUnsafe();</span><br><span class="line"></span><br><span class="line">    <span class="keyword">private</span> <span class="type">long</span> address;</span><br><span class="line">    <span class="keyword">private</span> <span class="type">long</span> size;</span><br><span class="line">    <span class="keyword">private</span> <span class="type">int</span> capacity;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">private</span> <span class="title function_">Deallocator</span><span class="params">(<span class="type">long</span> address, <span class="type">long</span> size, <span class="type">int</span> capacity)</span> &#123;</span><br><span class="line">        <span class="keyword">assert</span> (address != <span class="number">0</span>);</span><br><span class="line">        <span class="built_in">this</span>.address = address;</span><br><span class="line">        <span class="built_in">this</span>.size = size;</span><br><span class="line">        <span class="built_in">this</span>.capacity = capacity;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">public</span> <span class="keyword">void</span> <span class="title function_">run</span><span class="params">()</span> &#123;</span><br><span class="line">        <span class="keyword">if</span> (address == <span class="number">0</span>) &#123;</span><br><span class="line">            <span class="comment">// Paranoia</span></span><br><span class="line">            <span class="keyword">return</span>;</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="comment">// 释放本地内存</span></span><br><span class="line">        unsafe.freeMemory(address);</span><br><span class="line">        address = <span class="number">0</span>;</span><br><span class="line">        Bits.unreserveMemory(size, capacity);</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<h2 id="CAS-相关"><a href="#CAS-相关" class="headerlink" title="CAS 相关"></a>CAS 相关</h2><p><code>Unsafe</code> 提供了 <code>3</code> 个 <code>CAS</code> 相关操作的方法，方法将内存位置的值与预期原值比较，如果相匹配，则 <code>CPU</code> 会自动将该位置更新为新值，否则，<code>CPU</code> 不做任何操作。这些方法的底层实现对应着 <code>CPU</code> 指令 <code>cmpxchg</code>。</p>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="comment">// 如果 Java 变量当前符合预期，则自动将其更新为 x。</span></span><br><span class="line"><span class="keyword">public</span> <span class="keyword">final</span> <span class="keyword">native</span> <span class="type">boolean</span> <span class="title function_">compareAndSwapObject</span><span class="params">(Object o, <span class="type">long</span> offset, Object expected, Object x)</span>;</span><br><span class="line"><span class="keyword">public</span> <span class="keyword">final</span> <span class="keyword">native</span> <span class="type">boolean</span> <span class="title function_">compareAndSwapInt</span><span class="params">(Object o, <span class="type">long</span> offset, <span class="type">int</span> expected, <span class="type">int</span> x)</span>;</span><br><span class="line"><span class="keyword">public</span> <span class="keyword">final</span> <span class="keyword">native</span> <span class="type">boolean</span> <span class="title function_">compareAndSwapLong</span><span class="params">(Object o, <span class="type">long</span> offset, <span class="type">long</span> expected, <span class="type">long</span> x)</span>;</span><br></pre></td></tr></table></figure>
+
+<p>在 <code>AtomicInteger</code> 的实现中，静态字段 <code>valueOffset</code> 即为字段 <code>value</code> 的内存偏移地址，<code>valueOffset</code> 的值在 <code>AtomicInteger</code> 初始化时，在静态代码块中通过 <code>Unsafe</code> 的 <code>objectFieldOffset</code> 方法获取。</p>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">class</span> <span class="title class_">AtomicInteger</span> <span class="keyword">extends</span> <span class="title class_">Number</span> <span class="keyword">implements</span> <span class="title class_">java</span>.io.Serializable &#123;</span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">static</span> <span class="keyword">final</span> <span class="type">long</span> <span class="variable">serialVersionUID</span> <span class="operator">=</span> <span class="number">6214790243416807050L</span>;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// setup to use Unsafe.compareAndSwapInt for updates</span></span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">static</span> <span class="keyword">final</span> <span class="type">Unsafe</span> <span class="variable">unsafe</span> <span class="operator">=</span> Unsafe.getUnsafe();</span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">static</span> <span class="keyword">final</span> <span class="type">long</span> valueOffset;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">static</span> &#123;</span><br><span class="line">        <span class="keyword">try</span> &#123;</span><br><span class="line">            valueOffset = unsafe.objectFieldOffset</span><br><span class="line">                (AtomicInteger.class.getDeclaredField(<span class="string">&quot;value&quot;</span>));</span><br><span class="line">        &#125; <span class="keyword">catch</span> (Exception ex) &#123; <span class="keyword">throw</span> <span class="keyword">new</span> <span class="title class_">Error</span>(ex); &#125;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">volatile</span> <span class="type">int</span> value;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<p>CAS 更新变量的值的内存变化如下：</p>
+<div style="width:80%;margin:auto"><img src="/2023/12/25/Unsafe-an-anti-Java-class/Pasted%20image%2020231226005107.png" class="" title="CAS 更新变量的值"></div>
+
+<p>配合 <code>ClassLayout</code> 打印 <code>AtomicInteger</code> 的内部结构更直观地感受 <code>offset</code> 的含义：</p>
+<figure class="highlight text"><table><tr><td class="code"><pre><span class="line">java.util.concurrent.atomic.AtomicInteger object internals:</span><br><span class="line">OFF  SZ   TYPE DESCRIPTION               VALUE</span><br><span class="line">  0   8        (object header: mark)     0x0000000000000001 (non-biasable; age: 0)</span><br><span class="line">  8   4        (object header: class)    0xf8003dbc</span><br><span class="line"> 12   4    int AtomicInteger.value       1</span><br><span class="line">Instance size: 16 bytes</span><br><span class="line">Space losses: 0 bytes internal + 0 bytes external = 0 bytes total</span><br></pre></td></tr></table></figure>
 
-<p><code>parse</code> 方法与其说是解析，不如说是封装了一些设置并最终调用 <code>ClassPathBeanDefinitionScanner</code>，而设置的属性值来源于 <code>@ComponentScan</code> 的注解属性。关于获取 <code>@ComponentScan</code> 的注解属性的方法 <code>AnnotationConfigUtils.attributesForRepeatable</code> 在分析 <code>@PropertySource</code> 时也曾经遇到过，顾名思义我们知道它应该是用于获取可重复的注解的属性。可是它和直接获取注解对象有什么区别呢？</p>
-<blockquote>
-<p>我们知道 <code>@SpringBootApplication</code> 拥有和 <code>@ComponentScan</code> 具备相似的功能，并且可以使用 <code>scanBasePackages</code> 和 <code>scanBasePackageClasses</code> 这两个属性设置扫描的包。也许你还知道 <code>@SpringBootApplication</code> 之所以如此是因为它被标注了 <code>@ComponentScan</code>，<code>scanBasePackages</code> 和 <code>scanBasePackageClasses</code> 分别是它的元注解 <code>@ComponentScan</code> 中 <code>basePackages</code> 和 <code>basePackageClasses</code> 的别名。你甚至可能知道<strong>如果在配置类上使用 <code>@ComponentScan</code> 设置包扫描后会导致 <code>@SpringBootApplication</code> 设置的包扫描失效</strong>。<br><strong>可是为什么呢？</strong>在 <code>Spring</code> 中我们会看到从指定类上直接获取目标注解的代码，我们还会看到递归地从元注解上获取目标注解的代码，我们使用 <code>@ComponentScan</code> 的经验告诉我们可重复注解不是覆盖彼此而是共同生效，那么为什么 <code>@SpringBootApplication</code> 上的 <code>@ComponentScan</code> 就被覆盖了呢？<strong>想当然的认为 <code>@SpringBootApplication</code> 上标注了 <code>@ComponentScan</code> 是一切的原因是不够的</strong>。</p>
-</blockquote>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="meta">@Target(ElementType.TYPE)</span></span><br><span class="line"><span class="meta">@Retention(RetentionPolicy.RUNTIME)</span></span><br><span class="line"><span class="meta">@Documented</span></span><br><span class="line"><span class="meta">@Inherited</span></span><br><span class="line"><span class="meta">@SpringBootConfiguration</span></span><br><span class="line"><span class="meta">@EnableAutoConfiguration</span></span><br><span class="line"><span class="meta">@ComponentScan(excludeFilters = &#123;</span></span><br><span class="line"><span class="meta">		@Filter(type = FilterType.CUSTOM, classes = TypeExcludeFilter.class),</span></span><br><span class="line"><span class="meta">		@Filter(type = FilterType.CUSTOM, classes = AutoConfigurationExcludeFilter.class) &#125;)</span></span><br><span class="line"><span class="keyword">public</span> <span class="meta">@interface</span> SpringBootApplication &#123;</span><br><span class="line"></span><br><span class="line">	<span class="meta">@AliasFor(annotation = EnableAutoConfiguration.class)</span></span><br><span class="line">	Class&lt;?&gt;[] exclude() <span class="keyword">default</span> &#123;&#125;;</span><br><span class="line"></span><br><span class="line">	<span class="meta">@AliasFor(annotation = EnableAutoConfiguration.class)</span></span><br><span class="line">	String[] excludeName() <span class="keyword">default</span> &#123;&#125;;</span><br><span class="line"></span><br><span class="line">	<span class="meta">@AliasFor(annotation = ComponentScan.class, attribute = &quot;basePackages&quot;)</span></span><br><span class="line">	String[] scanBasePackages() <span class="keyword">default</span> &#123;&#125;;</span><br><span class="line"></span><br><span class="line">	<span class="meta">@AliasFor(annotation = ComponentScan.class, attribute = &quot;basePackageClasses&quot;)</span></span><br><span class="line">	Class&lt;?&gt;[] scanBasePackageClasses() <span class="keyword">default</span> &#123;&#125;;</span><br><span class="line"></span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
 
-<h2 id="获取注解属性"><a href="#获取注解属性" class="headerlink" title="获取注解属性"></a>获取注解属性</h2><p><code>attributesForRepeatable</code> 方法有两个重载方法，最终调用的版本如下。先后处理了 <code>@ComponentScan</code> 和 <code>@ComponentScans</code>。</p>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">static</span> Set&lt;AnnotationAttributes&gt; <span class="title function_">attributesForRepeatable</span><span class="params">(AnnotationMetadata metadata,</span></span><br><span class="line"><span class="params">        String containerClassName, String annotationClassName)</span> &#123;</span><br><span class="line">    <span class="comment">// Set 用于存储结果</span></span><br><span class="line">    Set&lt;AnnotationAttributes&gt; result = <span class="keyword">new</span> <span class="title class_">LinkedHashSet</span>&lt;AnnotationAttributes&gt;();</span><br><span class="line">    <span class="comment">// 处理 @ComponentScan</span></span><br><span class="line">    addAttributesIfNotNull(result, metadata.getAnnotationAttributes(annotationClassName, <span class="literal">false</span>));</span><br><span class="line">    <span class="comment">// 处理 @ComponentScans</span></span><br><span class="line">    Map&lt;String, Object&gt; container = metadata.getAnnotationAttributes(containerClassName, <span class="literal">false</span>);</span><br><span class="line">    <span class="keyword">if</span> (container != <span class="literal">null</span> &amp;&amp; container.containsKey(<span class="string">&quot;value&quot;</span>)) &#123;</span><br><span class="line">        <span class="keyword">for</span> (Map&lt;String, Object&gt; containedAttributes : (Map&lt;String, Object&gt;[]) container.get(<span class="string">&quot;value&quot;</span>)) &#123;</span><br><span class="line">            addAttributesIfNotNull(result, containedAttributes);</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="keyword">return</span> Collections.unmodifiableSet(result);</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
 
-<h3 id="检索注解的规则"><a href="#检索注解的规则" class="headerlink" title="检索注解的规则"></a>检索注解的规则</h3><p>根据注释，<code>getAnnotationAttributes</code> 方法检索给定类型的注解的属性，<strong>检索的目标可以是直接注解也可以是元注解</strong>，同时考虑<strong>组合注解上的属性覆盖</strong>。</p>
-<ul>
-<li>元注解指的是标注在其他注解上的注解，用于对被标注的注解进行说明，比如 <code>@SpringBootApplication</code> 上的 <code>@ComponentScan</code> 就被称为元注解，此时 <code>@SpringBootApplication</code> 被称为组合注解</li>
-<li>组合注解中存在属性覆盖现象</li>
+<h2 id="参考文章"><a href="#参考文章" class="headerlink" title="参考文章"></a>参考文章</h2><ul>
+<li><a href="https://tech.meituan.com/2019/02/14/talk-about-java-magic-class-unsafe.html">Java魔法类：Unsafe应用解析</a></li>
 </ul>
-<blockquote>
-<p>其实这两点分别对应了我们想要探究的两个问题：<code>@ComponentScan</code> 究竟是如何被检索的？注解属性比如 <code>basePackages</code> 又是如何被覆盖的？</p>
-</blockquote>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> Map&lt;String, Object&gt; <span class="title function_">getAnnotationAttributes</span><span class="params">(String annotationName, <span class="type">boolean</span> classValuesAsString)</span> &#123;</span><br><span class="line">    <span class="comment">// 获取合并的注解属性</span></span><br><span class="line">    <span class="keyword">return</span> (<span class="built_in">this</span>.annotations.length &gt; <span class="number">0</span> ? AnnotatedElementUtils.getMergedAnnotationAttributes(</span><br><span class="line">            getIntrospectedClass(), annotationName, classValuesAsString, <span class="built_in">this</span>.nestedAnnotationsAsMap) : <span class="literal">null</span>);</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+]]></content>
+      <tags>
+        <tag>java</tag>
+      </tags>
+  </entry>
+  <entry>
+    <title>Java 类 Reference 的源码分析</title>
+    <url>/2023/12/27/source-code-analysis-of-Java-class-Reference/</url>
+    <content><![CDATA[<p>我们知道 <code>Java</code> 扩充了“引用”的概念，引入了软引用、弱引用和虚引用，它们都属于 <code>Reference</code> 类型，也都可以配合 <code>ReferenceQueue</code> 使用。你是否好奇常常被一笔带过的“<code>引用对象</code>的处理过程”？你是否在探究 <code>NIO</code> 堆外内存的自动释放时看到了 <code>Cleaner</code> 的关键代码但不太能梳理整个过程？你是否好奇在研究 <code>JVM</code> 时偶尔看到的 <code>Reference Handler</code> 线程？本文将分析 <code>Reference</code> 和 <code>ReferenceQueue</code> 的源码带你理解<code>引用对象</code>的工作机制。</p>
+<span id="more"></span>
 
-<p>根据注释，<code>getMergedAnnotationAttributes</code> 方法获取所提供元素上方的注解层次结构中指定的 <code>annotationName</code> 的第一个注解，并将该注解的属性与注解层次结构较低级别中的注解中的匹配属性合并。注解层次结构中较低级别的属性会覆盖较高级别中的同名属性，并且完全支持单个注解中或是注解层次结构中的 <code>@AliasFor</code> 语义。与 <code>getAllAnnotationAttributes</code> 方法相反，一旦找到指定 <code>annotationName</code> 的第一个注解，此方法使用的搜索算法将停止搜索注解层次结构。因此，指定的 <code>annotationName</code> 的附加注解将被忽略。</p>
 <blockquote>
-<p>这注释有点太抽象了，理解代码后再来回味吧。</p>
+<p>事实上，个人感觉在无相关前置知识的情况下，单纯看 <code>JDK</code> 的 <code>Java</code> 代码是没办法很好地理解<code>引用对象</code>是如何被添加到<code>引用队列</code>中的。因为 <code>Reference</code> 的 <code>pending</code> 字段的含义和赋值操作是隐藏在 <code>JVM</code> 的 <code>C++</code> 代码中，本文搁置了其中的细节，仅分析 <code>JDK</code> 中相关的 <code>Java</code> 代码。</p>
 </blockquote>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">static</span> AnnotationAttributes <span class="title function_">getMergedAnnotationAttributes</span><span class="params">(AnnotatedElement element,</span></span><br><span class="line"><span class="params">        String annotationName, <span class="type">boolean</span> classValuesAsString, <span class="type">boolean</span> nestedAnnotationsAsMap)</span> &#123;</span><br><span class="line">    <span class="comment">// 以 get 语义进行搜索（是指找到即终止搜索？）</span></span><br><span class="line">    <span class="type">AnnotationAttributes</span> <span class="variable">attributes</span> <span class="operator">=</span> searchWithGetSemantics(element, <span class="literal">null</span>, annotationName,</span><br><span class="line">            <span class="keyword">new</span> <span class="title class_">MergedAnnotationAttributesProcessor</span>(classValuesAsString, nestedAnnotationsAsMap));</span><br><span class="line">    <span class="comment">// 后处理注解属性</span></span><br><span class="line">    AnnotationUtils.postProcessAnnotationAttributes(element, attributes, classValuesAsString, nestedAnnotationsAsMap);</span><br><span class="line">    <span class="keyword">return</span> attributes;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+<h2 id="Reference"><a href="#Reference" class="headerlink" title="Reference"></a>Reference</h2><p><code>Reference</code> 是<code>引用对象</code>的抽象基类。此类定义了所有引用对象通用的操作。由于引用对象是与垃圾收集器密切合作实现的，因此该类可能无法直接子类化。</p>
+<div style="width:70%;margin:auto"><img src="/2023/12/27/source-code-analysis-of-Java-class-Reference/Pasted%20image%2020231227230915.png" class="" title="Reference 相关类图"></div>
 
-<p><code>searchWithGetSemantics</code> 方法有多个重载方法，最终调用的版本如下：</p>
-<ul>
-<li>先获取 <code>element</code> 上的所有注解（包括重复的，不包括继承的），<strong>这意味着可重复注解 <code>@ComponentScan</code> 标注了多个就会有多个实例</strong></li>
-<li>在注解中搜索</li>
-<li>如果没找到，就从继承的注解中继续搜索</li>
+<h3 id="构造函数"><a href="#构造函数" class="headerlink" title="构造函数"></a>构造函数</h3><ul>
+<li><code>referent</code>: <code>引用对象</code>关联的对象</li>
+<li><code>queue</code>: <code>引用对象</code>准备注册到的<code>引用队列</code></li>
 </ul>
+<p><code>Reference</code> 提供了两个构造函数，一个需要传入<code>引用队列</code>（<code>ReferenceQueue</code>），一个不需要。如果一个<code>引用对象</code>（<code>Reference</code>）注册到一个<code>引用队列</code>，在检测到关联对象有适当的可达性变化后，垃圾收集器将把该<code>引用对象</code>添加到该引用队列。</p>
 <blockquote>
-<p>本方法是一个会被递归调用的方法，在第一次调用时 <code>element</code> 是配置类，之后就是注解。</p>
+<p>“关联对象有适当的可达性变化”并不容易理解，在很多表述中它很容易被简化为“可以被回收”，但是同时我们又拥有另一条规则，即“一个对象是否可回收的判断依据是是否从 <code>Root</code> 对象可达”。在面对 <code>Reference</code> 的子类时，我们有种割裂感，好像一条和谐的规则出现了特殊条例。<a href="/2023/12/28/explore-the-Java-classes-Cleaner-and-Finalizer/" title="探索 Java 类 Cleaner 和 Finalizer">探索 Java 类 Cleaner 和 Finalizer</a></p>
 </blockquote>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">private</span> <span class="keyword">static</span> &lt;T&gt; T <span class="title function_">searchWithGetSemantics</span><span class="params">(AnnotatedElement element,</span></span><br><span class="line"><span class="params">        <span class="meta">@Nullable</span> Class&lt;? extends Annotation&gt; annotationType, <span class="meta">@Nullable</span> String annotationName,</span></span><br><span class="line"><span class="params">        <span class="meta">@Nullable</span> Class&lt;? extends Annotation&gt; containerType, Processor&lt;T&gt; processor,</span></span><br><span class="line"><span class="params">        Set&lt;AnnotatedElement&gt; visited, <span class="type">int</span> metaDepth)</span> &#123;</span><br><span class="line">    <span class="comment">// 防止无限递归</span></span><br><span class="line">    <span class="keyword">if</span> (visited.add(element)) &#123;</span><br><span class="line">        <span class="keyword">try</span> &#123;</span><br><span class="line">            <span class="comment">// 获取 element 上的所有注解（包括重复，不包括继承的）</span></span><br><span class="line">            List&lt;Annotation&gt; declaredAnnotations = Arrays.asList(element.getDeclaredAnnotations());</span><br><span class="line">            <span class="comment">// 在获得的注解中搜索</span></span><br><span class="line">            <span class="type">T</span> <span class="variable">result</span> <span class="operator">=</span> searchWithGetSemanticsInAnnotations(element, declaredAnnotations,</span><br><span class="line">                    annotationType, annotationName, containerType, processor, visited, metaDepth);</span><br><span class="line">            <span class="keyword">if</span> (result != <span class="literal">null</span>) &#123;</span><br><span class="line">                <span class="keyword">return</span> result;</span><br><span class="line">            &#125;</span><br><span class="line">            <span class="comment">// 表明在直接声明的注解中没有找到</span></span><br><span class="line">            <span class="comment">// 如果 element 是一个类</span></span><br><span class="line">            <span class="keyword">if</span> (element <span class="keyword">instanceof</span> Class) &#123;</span><br><span class="line">                <span class="comment">// 获取所有的注解（包括重复的和继承的）</span></span><br><span class="line">                List&lt;Annotation&gt; inheritedAnnotations = <span class="keyword">new</span> <span class="title class_">ArrayList</span>&lt;&gt;();</span><br><span class="line">                <span class="keyword">for</span> (Annotation annotation : element.getAnnotations()) &#123;</span><br><span class="line">                    <span class="comment">// 排除已经搜索过的，只留下继承的注解</span></span><br><span class="line">                    <span class="keyword">if</span> (!declaredAnnotations.contains(annotation)) &#123;</span><br><span class="line">                        inheritedAnnotations.add(annotation);</span><br><span class="line">                    &#125;</span><br><span class="line">                &#125;</span><br><span class="line">                <span class="comment">// 继续搜索</span></span><br><span class="line">                result = searchWithGetSemanticsInAnnotations(element, inheritedAnnotations,</span><br><span class="line">                        annotationType, annotationName, containerType, processor, visited, metaDepth);</span><br><span class="line">                <span class="keyword">if</span> (result != <span class="literal">null</span>) &#123;</span><br><span class="line">                    <span class="keyword">return</span> result;</span><br><span class="line">                &#125;</span><br><span class="line">            &#125;</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="keyword">catch</span> (Throwable ex) &#123;</span><br><span class="line">            AnnotationUtils.handleIntrospectionFailure(element, ex);</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">return</span> <span class="literal">null</span>;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line">Reference(T referent) &#123;</span><br><span class="line">    <span class="built_in">this</span>(referent, <span class="literal">null</span>);</span><br><span class="line">&#125;</span><br><span class="line"></span><br><span class="line">Reference(T referent, ReferenceQueue&lt;? <span class="built_in">super</span> T&gt; queue) &#123;</span><br><span class="line">    <span class="built_in">this</span>.referent = referent;</span><br><span class="line">    <span class="comment">// ReferenceQueue.NULL 表示没有注册到引用队列</span></span><br><span class="line">    <span class="built_in">this</span>.queue = (queue == <span class="literal">null</span>) ? ReferenceQueue.NULL : queue;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
 
-<p>遍历注解进行搜索。</p>
+<h3 id="属性"><a href="#属性" class="headerlink" title="属性"></a>属性</h3><h4 id="成员变量"><a href="#成员变量" class="headerlink" title="成员变量"></a>成员变量</h4><ul>
+<li><code>referent</code>: <code>引用对象</code>关联的对象，<strong>该对象将被垃圾收集器特殊对待</strong>。我们很难直观地感受何谓“被垃圾收集器特殊对待”，它对应着“在检测到关联对象有适当的可达性变化后，垃圾收集器将把<code>引用对象</code>添加到该引用队列”。</li>
+<li><code>queue</code>: <code>引用对象</code>注册到的<code>引用队列</code></li>
+<li><code>next</code>: 用于指向下一个<code>引用对象</code>，当<code>引用对象</code>已经添加到<code>引用队列</code>中，<code>next</code> 指向<code>引用队列</code>中的下一个<code>引用对象</code></li>
+<li><code>discovered</code>: 用于指向下一个<code>引用对象</code>，用于在全局的 <code>pending</code> 链表中，指向下一个待添加到<code>引用队列</code>的<code>引用对象</code></li>
+</ul>
+<div style="width:60%;margin:auto"><img src="/2023/12/27/source-code-analysis-of-Java-class-Reference/Pasted%20image%2020231227192404.png" class="" title="引用对象"></div>
+
+<h4 id="静态变量"><a href="#静态变量" class="headerlink" title="静态变量"></a>静态变量</h4><blockquote>
+<p>注意：<code>lock</code> 和 <code>pending</code> 是全局共享的。</p>
+</blockquote>
 <ul>
-<li>先在注解中搜索，<strong>这意味着如果配置类标注了 <code>@ComponentScan</code>，直接就找到了</strong></li>
-<li>如果没找到再在元注解中搜索，如果配置类只标注了 <code>@SpringBootApplication</code>，就是在这部分找到元注解 <code>@ComponentScan</code></li>
+<li><code>lock</code>: 用于与垃圾收集器同步的对象，<strong>垃圾收集器必须在每个收集周期开始时获取此锁</strong>。因此至关重要的是持有此锁的任何代码必须尽快运行完，不分配新对象并避免调用用户代码。</li>
+<li><code>pending</code>: 等待加入<code>引用队列</code>的<code>引用对象</code>链表。垃圾收集器将<code>引用对象</code>添加到 <code>pending</code> 链表中，而 <code>Reference-Handler</code> 线程将删除它们，并做清理或入队操作。<code>pending</code> 链表受上述 <code>lock</code> 对象的保护，并使用 <code>discovered</code> 字段来链接下一个元素。</li>
 </ul>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">abstract</span> <span class="keyword">class</span> <span class="title class_">Reference</span>&lt;T&gt; &#123;</span><br><span class="line">    <span class="keyword">private</span> T referent;         <span class="comment">/* Treated specially by GC */</span></span><br><span class="line"></span><br><span class="line">    <span class="keyword">volatile</span> ReferenceQueue&lt;? <span class="built_in">super</span> T&gt; queue;</span><br><span class="line">    <span class="meta">@SuppressWarnings(&quot;rawtypes&quot;)</span></span><br><span class="line">    <span class="keyword">volatile</span> Reference next;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">transient</span> <span class="keyword">private</span> Reference&lt;T&gt; discovered;  <span class="comment">/* used by VM */</span></span><br><span class="line"></span><br><span class="line">    <span class="keyword">static</span> <span class="keyword">private</span> <span class="keyword">class</span> <span class="title class_">Lock</span> &#123; &#125;</span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">static</span> <span class="type">Lock</span> <span class="variable">lock</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">Lock</span>();</span><br><span class="line"></span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">static</span> Reference&lt;Object&gt; pending = <span class="literal">null</span>;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
 <blockquote>
-<p>严格意义上说，并不是直接标注的 <code>@ComponentScan</code> 会覆盖 <code>@SpringBootApplication</code> 上间接标注的 <code>@ComponentScan</code>，而是搜索在找到第一个注解后终止没有继续查找。这解答了我们的第一个疑问。</p>
+<p><code>Reference</code> 其实可以理解为单链表中的一个节点，除了核心的 <code>referent</code> 和 <code>queue</code>，<code>next</code> 和 <code>discovered</code> 都用于指向下一个<code>引用对象</code>，只是分别用于两条不同的单链表上。</p>
 </blockquote>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">private</span> <span class="keyword">static</span> &lt;T&gt; T <span class="title function_">searchWithGetSemanticsInAnnotations</span><span class="params">(<span class="meta">@Nullable</span> AnnotatedElement element,</span></span><br><span class="line"><span class="params">        List&lt;Annotation&gt; annotations, <span class="meta">@Nullable</span> Class&lt;? extends Annotation&gt; annotationType,</span></span><br><span class="line"><span class="params">        <span class="meta">@Nullable</span> String annotationName, <span class="meta">@Nullable</span> Class&lt;? extends Annotation&gt; containerType,</span></span><br><span class="line"><span class="params">        Processor&lt;T&gt; processor, Set&lt;AnnotatedElement&gt; visited, <span class="type">int</span> metaDepth)</span> &#123;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 遍历注解进行查找，如果同时标注 @SpringBootApplication 和 @ComponentScan，在这部分就会找到 @ComponentScan 就返回了</span></span><br><span class="line">    <span class="keyword">for</span> (Annotation annotation : annotations) &#123;</span><br><span class="line">        <span class="comment">// 获取注解的 Class</span></span><br><span class="line">        Class&lt;? <span class="keyword">extends</span> <span class="title class_">Annotation</span>&gt; currentAnnotationType = annotation.annotationType();</span><br><span class="line">        <span class="comment">// 检测是否属于 Java 语言注解包中（以 java.lang.annotation 开头）的注解，例如 @Documented，是的话跳过</span></span><br><span class="line">        <span class="keyword">if</span> (!AnnotationUtils.isInJavaLangAnnotationPackage(currentAnnotationType)) &#123;</span><br><span class="line">            <span class="comment">// 检测是否满足条件：等于 annotationType（传入 null），或者和目标的名字（@ComponentScan 全限定类名）相同，或者属于总是处理（默认 false）</span></span><br><span class="line">            <span class="keyword">if</span> (currentAnnotationType == annotationType ||</span><br><span class="line">                    currentAnnotationType.getName().equals(annotationName) ||</span><br><span class="line">                    processor.alwaysProcesses()) &#123;</span><br><span class="line">                <span class="comment">// 处理注解获得注解属性</span></span><br><span class="line">                <span class="type">T</span> <span class="variable">result</span> <span class="operator">=</span> processor.process(element, annotation, metaDepth);</span><br><span class="line">                <span class="keyword">if</span> (result != <span class="literal">null</span>) &#123;</span><br><span class="line">                    <span class="comment">// processor.aggregates() 默认返回 false</span></span><br><span class="line">                    <span class="keyword">if</span> (processor.aggregates() &amp;&amp; metaDepth == <span class="number">0</span>) &#123;</span><br><span class="line">                        processor.getAggregatedResults().add(result);</span><br><span class="line">                    &#125;</span><br><span class="line">                    <span class="keyword">else</span> &#123;</span><br><span class="line">                        <span class="comment">// 注意：难道标注多个 @ComponentScan 也只找到一个就返回了？</span></span><br><span class="line">                        <span class="keyword">return</span> result;</span><br><span class="line">                    &#125;</span><br><span class="line">                &#125;</span><br><span class="line">            &#125;</span><br><span class="line">            <span class="comment">// 容器里的可重复注解，因为 containerType 为 null，跳过</span></span><br><span class="line">            <span class="keyword">else</span> <span class="keyword">if</span> (currentAnnotationType == containerType) &#123;</span><br><span class="line">                <span class="keyword">for</span> (Annotation contained : getRawAnnotationsFromContainer(element, annotation)) &#123;</span><br><span class="line">                    <span class="type">T</span> <span class="variable">result</span> <span class="operator">=</span> processor.process(element, contained, metaDepth);</span><br><span class="line">                    <span class="keyword">if</span> (result != <span class="literal">null</span>) &#123;</span><br><span class="line">                        <span class="comment">// No need to post-process since repeatable annotations within a</span></span><br><span class="line">                        <span class="comment">// container cannot be composed annotations.</span></span><br><span class="line">                        processor.getAggregatedResults().add(result);</span><br><span class="line">                    &#125;</span><br><span class="line">                &#125;</span><br><span class="line">            &#125;</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 在元注解中递归的搜索，@SpringBootApplication 中的 @ComponentScan 就是在这找到的</span></span><br><span class="line">    <span class="keyword">for</span> (Annotation annotation : annotations) &#123;</span><br><span class="line">        <span class="comment">// 获取注解的 Class</span></span><br><span class="line">        Class&lt;? <span class="keyword">extends</span> <span class="title class_">Annotation</span>&gt; currentAnnotationType = annotation.annotationType();</span><br><span class="line">        <span class="comment">// 检测是否属于 Java 语言注解包中</span></span><br><span class="line">        <span class="keyword">if</span> (!AnnotationUtils.isInJavaLangAnnotationPackage(currentAnnotationType)) &#123;</span><br><span class="line">            <span class="comment">// 递归到元注解中搜索，深度加 1</span></span><br><span class="line">            <span class="type">T</span> <span class="variable">result</span> <span class="operator">=</span> searchWithGetSemantics(currentAnnotationType, annotationType,</span><br><span class="line">                    annotationName, containerType, processor, visited, metaDepth + <span class="number">1</span>);</span><br><span class="line">            <span class="keyword">if</span> (result != <span class="literal">null</span>) &#123;</span><br><span class="line">                <span class="comment">// 进行后处理，注解层次结构中较低级别的属性会覆盖较高级别中的同名属性就是在这发生的</span></span><br><span class="line">                processor.postProcess(element, annotation, result);</span><br><span class="line">                <span class="keyword">if</span> (processor.aggregates() &amp;&amp; metaDepth == <span class="number">0</span>) &#123;</span><br><span class="line">                    processor.getAggregatedResults().add(result);</span><br><span class="line">                &#125;</span><br><span class="line">                <span class="keyword">else</span> &#123;</span><br><span class="line">                    <span class="keyword">return</span> result;</span><br><span class="line">                &#125;</span><br><span class="line">            &#125;</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">return</span> <span class="literal">null</span>;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+<p><code>pending</code> 链表：</p>
+<div style="width:70%;margin:auto"><img src="/2023/12/27/source-code-analysis-of-Java-class-Reference/Pasted%20image%2020231227191324.png" class="" title="pending 链表"></div>
 
-<p>处理 <code>@ComponentScan</code> 获得 <code>AnnotationAttributes</code>。</p>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> AnnotationAttributes <span class="title function_">process</span><span class="params">(<span class="meta">@Nullable</span> AnnotatedElement annotatedElement, Annotation annotation, <span class="type">int</span> metaDepth)</span> &#123;</span><br><span class="line">    <span class="keyword">return</span> AnnotationUtils.retrieveAnnotationAttributes(annotatedElement, annotation,</span><br><span class="line">            <span class="built_in">this</span>.classValuesAsString, <span class="built_in">this</span>.nestedAnnotationsAsMap);</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+<p><code>ReferenceQueue</code>：</p>
+<div style="width:70%;margin:auto"><img src="/2023/12/27/source-code-analysis-of-Java-class-Reference/Pasted%20image%2020231227191330.png" class="" title="ReferenceQueue"></div>
 
-<p>以 <code>AnnotationAttributes</code> 映射的形式检索给定注解的属性。</p>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">static</span> AnnotationAttributes <span class="title function_">retrieveAnnotationAttributes</span><span class="params">(<span class="meta">@Nullable</span> Object annotatedElement, Annotation annotation,</span></span><br><span class="line"><span class="params">        <span class="type">boolean</span> classValuesAsString, <span class="type">boolean</span> nestedAnnotationsAsMap)</span> &#123;</span><br><span class="line"></span><br><span class="line">    Class&lt;? <span class="keyword">extends</span> <span class="title class_">Annotation</span>&gt; annotationType = annotation.annotationType();</span><br><span class="line">    <span class="type">AnnotationAttributes</span> <span class="variable">attributes</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">AnnotationAttributes</span>(annotationType);</span><br><span class="line">    <span class="comment">// 遍历属性方法</span></span><br><span class="line">    <span class="keyword">for</span> (Method method : getAttributeMethods(annotationType)) &#123;</span><br><span class="line">        <span class="keyword">try</span> &#123;</span><br><span class="line">            <span class="comment">// 获取属性值</span></span><br><span class="line">            <span class="type">Object</span> <span class="variable">attributeValue</span> <span class="operator">=</span> method.invoke(annotation);</span><br><span class="line">            <span class="comment">// 获取默认值</span></span><br><span class="line">            <span class="type">Object</span> <span class="variable">defaultValue</span> <span class="operator">=</span> method.getDefaultValue();</span><br><span class="line">            <span class="comment">// 如果默认值不为 null 且和属性值相同</span></span><br><span class="line">            <span class="keyword">if</span> (defaultValue != <span class="literal">null</span> &amp;&amp; ObjectUtils.nullSafeEquals(attributeValue, defaultValue)) &#123;</span><br><span class="line">                attributeValue = <span class="keyword">new</span> <span class="title class_">DefaultValueHolder</span>(defaultValue);</span><br><span class="line">            &#125;</span><br><span class="line">            <span class="comment">// 属性名 -&gt; 属性值</span></span><br><span class="line">            attributes.put(method.getName(),</span><br><span class="line">                    adaptValue(annotatedElement, attributeValue, classValuesAsString, nestedAnnotationsAsMap));</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="keyword">catch</span> (Throwable ex) &#123;</span><br><span class="line">            <span class="keyword">if</span> (ex <span class="keyword">instanceof</span> InvocationTargetException) &#123;</span><br><span class="line">                <span class="type">Throwable</span> <span class="variable">targetException</span> <span class="operator">=</span> ((InvocationTargetException) ex).getTargetException();</span><br><span class="line">                rethrowAnnotationConfigurationException(targetException);</span><br><span class="line">            &#125;</span><br><span class="line">            <span class="keyword">throw</span> <span class="keyword">new</span> <span class="title class_">IllegalStateException</span>(<span class="string">&quot;Could not obtain annotation attribute value for &quot;</span> + method, ex);</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">return</span> attributes;</span><br><span class="line">&#125;</span><br><span class="line"></span><br><span class="line"><span class="comment">// 获取在所提供的 annotationType 中声明的与 Java 对注释属性的要求相匹配的所有方法</span></span><br><span class="line"><span class="keyword">static</span> List&lt;Method&gt; <span class="title function_">getAttributeMethods</span><span class="params">(Class&lt;? extends Annotation&gt; annotationType)</span> &#123;</span><br><span class="line">    <span class="comment">// 先从缓存中获取</span></span><br><span class="line">    List&lt;Method&gt; methods = attributeMethodsCache.get(annotationType);</span><br><span class="line">    <span class="keyword">if</span> (methods != <span class="literal">null</span>) &#123;</span><br><span class="line">        <span class="keyword">return</span> methods;</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="comment">// 遍历方法筛选</span></span><br><span class="line">    methods = <span class="keyword">new</span> <span class="title class_">ArrayList</span>&lt;&gt;();</span><br><span class="line">    <span class="keyword">for</span> (Method method : annotationType.getDeclaredMethods()) &#123;</span><br><span class="line">        <span class="keyword">if</span> (isAttributeMethod(method)) &#123;</span><br><span class="line">            ReflectionUtils.makeAccessible(method);</span><br><span class="line">            methods.add(method);</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="comment">// 存入缓存</span></span><br><span class="line">    attributeMethodsCache.put(annotationType, methods);</span><br><span class="line">    <span class="keyword">return</span> methods;</span><br><span class="line">&#125;</span><br><span class="line"></span><br><span class="line"><span class="comment">// 确定提供的方法是否是注解的属性方法。</span></span><br><span class="line"><span class="keyword">static</span> <span class="type">boolean</span> <span class="title function_">isAttributeMethod</span><span class="params">(<span class="meta">@Nullable</span> Method method)</span> &#123;</span><br><span class="line">    <span class="comment">// 无参数 &amp;&amp; 返回值非 void</span></span><br><span class="line">    <span class="keyword">return</span> (method != <span class="literal">null</span> &amp;&amp; method.getParameterCount() == <span class="number">0</span> &amp;&amp; method.getReturnType() != <span class="keyword">void</span>.class);</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+<h3 id="ReferenceHandler-线程"><a href="#ReferenceHandler-线程" class="headerlink" title="ReferenceHandler 线程"></a>ReferenceHandler 线程</h3><p>启动任意一个非常简单的 <code>Java</code> 程序，通过 <code>JVM</code> 相关的工具，比如 <code>JConsole</code>，你都能看到一个名为 <code>Reference Handler</code> 的线程。</p>
+<div style="width:60%;margin:auto"><img src="/2023/12/27/source-code-analysis-of-Java-class-Reference/Snipaste_2023-12-27_19-41-19.png" class="" title="Reference-Handler 线程"></div>
 
-<h3 id="组合注解的属性覆盖"><a href="#组合注解的属性覆盖" class="headerlink" title="组合注解的属性覆盖"></a>组合注解的属性覆盖</h3><p>在获得注解属性后还要进行后处理，使用注解层次结构中较低级别的属性覆盖较高级别中的同名（包括 <code>@AliasFor</code> 指定的）属性。比如使用 <code>@SpringBootApplication</code> 中的 <code>scanBasePackages</code> 的值覆盖 <code>@ComponentScan</code> 中的 <code>basePackages</code> 的值。</p>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title function_">postProcess</span><span class="params">(<span class="meta">@Nullable</span> AnnotatedElement element, Annotation annotation, AnnotationAttributes attributes)</span> &#123;</span><br><span class="line">    annotation = AnnotationUtils.synthesizeAnnotation(annotation, element);</span><br><span class="line">    <span class="comment">// 获取 AnnotationAttributes 的注解类型（@ComponentScan）</span></span><br><span class="line">    Class&lt;? <span class="keyword">extends</span> <span class="title class_">Annotation</span>&gt; targetAnnotationType = attributes.annotationType();</span><br><span class="line"></span><br><span class="line">    <span class="comment">// Track which attribute values have already been replaced so that we can short</span></span><br><span class="line">    <span class="comment">// circuit the search algorithms.</span></span><br><span class="line">    Set&lt;String&gt; valuesAlreadyReplaced = <span class="keyword">new</span> <span class="title class_">HashSet</span>&lt;&gt;();</span><br><span class="line">    <span class="comment">// 获取注解的属性方法（SpringBootApplication）</span></span><br><span class="line">    <span class="keyword">for</span> (Method attributeMethod : AnnotationUtils.getAttributeMethods(annotation.annotationType())) &#123;</span><br><span class="line">        <span class="type">String</span> <span class="variable">attributeName</span> <span class="operator">=</span> attributeMethod.getName();</span><br><span class="line">        <span class="comment">// 获取被覆盖的别名</span></span><br><span class="line">        <span class="type">String</span> <span class="variable">attributeOverrideName</span> <span class="operator">=</span> AnnotationUtils.getAttributeOverrideName(attributeMethod, targetAnnotationType);</span><br><span class="line"></span><br><span class="line">        <span class="comment">// Explicit annotation attribute override declared via @AliasFor</span></span><br><span class="line">        <span class="keyword">if</span> (attributeOverrideName != <span class="literal">null</span>) &#123;</span><br><span class="line">            <span class="comment">// 被覆盖的属性的值是否已经被替换</span></span><br><span class="line">            <span class="keyword">if</span> (valuesAlreadyReplaced.contains(attributeOverrideName)) &#123;</span><br><span class="line">                <span class="keyword">continue</span>;</span><br><span class="line">            &#125;</span><br><span class="line"></span><br><span class="line">            List&lt;String&gt; targetAttributeNames = <span class="keyword">new</span> <span class="title class_">ArrayList</span>&lt;&gt;();</span><br><span class="line">            targetAttributeNames.add(attributeOverrideName);</span><br><span class="line">            valuesAlreadyReplaced.add(attributeOverrideName);</span><br><span class="line"></span><br><span class="line">            <span class="comment">// 确保覆盖目标注解中的所有别名属性。 (SPR-14069)</span></span><br><span class="line">            List&lt;String&gt; aliases = AnnotationUtils.getAttributeAliasMap(targetAnnotationType).get(attributeOverrideName);</span><br><span class="line">            <span class="keyword">if</span> (aliases != <span class="literal">null</span>) &#123;</span><br><span class="line">                <span class="keyword">for</span> (String alias : aliases) &#123;</span><br><span class="line">                    <span class="keyword">if</span> (!valuesAlreadyReplaced.contains(alias)) &#123;</span><br><span class="line">                        targetAttributeNames.add(alias);</span><br><span class="line">                        valuesAlreadyReplaced.add(alias);</span><br><span class="line">                    &#125;</span><br><span class="line">                &#125;</span><br><span class="line">            &#125;</span><br><span class="line"></span><br><span class="line">            overrideAttributes(element, annotation, attributes, attributeName, targetAttributeNames);</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="comment">// Implicit annotation attribute override based on convention</span></span><br><span class="line">        <span class="keyword">else</span> <span class="keyword">if</span> (!AnnotationUtils.VALUE.equals(attributeName) &amp;&amp; attributes.containsKey(attributeName)) &#123;</span><br><span class="line">            overrideAttribute(element, annotation, attributes, attributeName, attributeName);</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br><span class="line"></span><br><span class="line"><span class="comment">// 根据提供的注解属性方法的 @AliasFor，获取被覆盖的属性的名称</span></span><br><span class="line"><span class="keyword">static</span> String <span class="title function_">getAttributeOverrideName</span><span class="params">(Method attribute, <span class="meta">@Nullable</span> Class&lt;? extends Annotation&gt; metaAnnotationType)</span> &#123;</span><br><span class="line">    <span class="comment">// 获取别名描述符</span></span><br><span class="line">    <span class="type">AliasDescriptor</span> <span class="variable">descriptor</span> <span class="operator">=</span> AliasDescriptor.from(attribute);</span><br><span class="line">    <span class="comment">// 从元注解中被覆盖的属性名</span></span><br><span class="line">    <span class="keyword">return</span> (descriptor != <span class="literal">null</span> &amp;&amp; metaAnnotationType != <span class="literal">null</span> ?</span><br><span class="line">            descriptor.getAttributeOverrideName(metaAnnotationType) : <span class="literal">null</span>);</span><br><span class="line">&#125;</span><br><span class="line"></span><br><span class="line"><span class="comment">// 获取在提供的注解类型中通过 @AliasFor 声明的所有属性别名的映射。该映射由属性名称作为键，每个值代表别名属性的名称列表。空返回值意味着注解没有声明任何属性别名。</span></span><br><span class="line"><span class="keyword">static</span> Map&lt;String, List&lt;String&gt;&gt; <span class="title function_">getAttributeAliasMap</span><span class="params">(<span class="meta">@Nullable</span> Class&lt;? extends Annotation&gt; annotationType)</span> &#123;</span><br><span class="line">    <span class="keyword">if</span> (annotationType == <span class="literal">null</span>) &#123;</span><br><span class="line">        <span class="keyword">return</span> Collections.emptyMap();</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="comment">// 从缓存中获取</span></span><br><span class="line">    Map&lt;String, List&lt;String&gt;&gt; map = attributeAliasesCache.get(annotationType);</span><br><span class="line">    <span class="keyword">if</span> (map != <span class="literal">null</span>) &#123;</span><br><span class="line">        <span class="keyword">return</span> map;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    map = <span class="keyword">new</span> <span class="title class_">LinkedHashMap</span>&lt;&gt;();</span><br><span class="line">    <span class="comment">// 遍历属性方法</span></span><br><span class="line">    <span class="keyword">for</span> (Method attribute : getAttributeMethods(annotationType)) &#123;</span><br><span class="line">        <span class="comment">// 获取别名列表</span></span><br><span class="line">        List&lt;String&gt; aliasNames = getAttributeAliasNames(attribute);</span><br><span class="line">        <span class="keyword">if</span> (!aliasNames.isEmpty()) &#123;</span><br><span class="line">            map.put(attribute.getName(), aliasNames);</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="comment">// 存入缓存</span></span><br><span class="line">    attributeAliasesCache.put(annotationType, map);</span><br><span class="line">    <span class="keyword">return</span> map;</span><br><span class="line">&#125;</span><br><span class="line"></span><br><span class="line"><span class="comment">// 获取通过提供的注解属性的 @AliasFor 配置的别名属性的名称列表</span></span><br><span class="line"><span class="keyword">static</span> List&lt;String&gt; <span class="title function_">getAttributeAliasNames</span><span class="params">(Method attribute)</span> &#123;</span><br><span class="line">    <span class="type">AliasDescriptor</span> <span class="variable">descriptor</span> <span class="operator">=</span> AliasDescriptor.from(attribute);</span><br><span class="line">    <span class="keyword">return</span> (descriptor != <span class="literal">null</span> ? descriptor.getAttributeAliasNames() : Collections.&lt;String&gt; emptyList());</span><br><span class="line">&#125;</span><br><span class="line"></span><br><span class="line"><span class="comment">// 覆盖属性</span></span><br><span class="line"><span class="keyword">private</span> <span class="keyword">void</span> <span class="title function_">overrideAttributes</span><span class="params">(<span class="meta">@Nullable</span> AnnotatedElement element, Annotation annotation,</span></span><br><span class="line"><span class="params">        AnnotationAttributes attributes, String sourceAttributeName, List&lt;String&gt; targetAttributeNames)</span> &#123;</span><br><span class="line"></span><br><span class="line">    <span class="type">Object</span> <span class="variable">adaptedValue</span> <span class="operator">=</span> getAdaptedValue(element, annotation, sourceAttributeName);</span><br><span class="line">    <span class="comment">// 遍历目标属性中的所有应被覆盖的属性（本尊+别名）</span></span><br><span class="line">    <span class="keyword">for</span> (String targetAttributeName : targetAttributeNames) &#123;</span><br><span class="line">        attributes.put(targetAttributeName, adaptedValue);</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+<p><code>ReferenceHandler</code> 类本身的代码并不复杂。</p>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">private</span> <span class="keyword">static</span> <span class="keyword">class</span> <span class="title class_">ReferenceHandler</span> <span class="keyword">extends</span> <span class="title class_">Thread</span> &#123;</span><br><span class="line">    <span class="comment">// 确保类已经初始化</span></span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">ensureClassInitialized</span><span class="params">(Class&lt;?&gt; clazz)</span> &#123;</span><br><span class="line">        <span class="keyword">try</span> &#123;</span><br><span class="line">            Class.forName(clazz.getName(), <span class="literal">true</span>, clazz.getClassLoader());</span><br><span class="line">        &#125; <span class="keyword">catch</span> (ClassNotFoundException e) &#123;</span><br><span class="line">            <span class="keyword">throw</span> (Error) <span class="keyword">new</span> <span class="title class_">NoClassDefFoundError</span>(e.getMessage()).initCause(e);</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">static</span> &#123;</span><br><span class="line">        <span class="comment">// 预加载和初始化 InterruptedException 和 Cleaner，以避免在 run 方法中懒加载发生内存不足时陷入麻烦（咱也不知道具体啥麻烦）</span></span><br><span class="line">        ensureClassInitialized(InterruptedException.class);</span><br><span class="line">        ensureClassInitialized(Cleaner.class);</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    ReferenceHandler(ThreadGroup g, String name) &#123;</span><br><span class="line">        <span class="built_in">super</span>(g, name);</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">public</span> <span class="keyword">void</span> <span class="title function_">run</span><span class="params">()</span> &#123;</span><br><span class="line">        <span class="comment">// run 方法循环调用 tryHandlePending</span></span><br><span class="line">        <span class="keyword">while</span> (<span class="literal">true</span>) &#123;</span><br><span class="line">            tryHandlePending(<span class="literal">true</span>);</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
 
-<p>在代码的注释中我们留下过一个疑问，如果找到了第一个注解就立即返回，那么标注了多个 <code>@ComponentScan</code> 呢？当你 <code>Debug</code> 时，你会发现并没有走出现直接标注了 <code>@ComponentScan</code> 的处理，其实看到反编译后的代码你就知道了，多个 <code>@ComponentScan</code> 被合成了一个 <code>@ComponentScans</code>，甚至此时设置的三个 <code>basePackages</code> 都是生效的。在 <code>JDK 8</code> 引入的重复注解机制，并非一个语言层面上的改动，而是编译器层面的改动。在编译后，多个可重复注解 <code>@ComponentScan</code> 会被合并到一个容器注解 <code>@ComponentScans</code> 中。</p>
-<blockquote>
-<p>因此，“<code>@ComponentScan</code> 的配置会覆盖 <code>@SpringBootApplication</code> 关于包扫描的配置”这句话既对又不对，它在一个常见的个例上表现出的现象是对的，在更普遍的情况中以及本质上是错误的。你也许可以再根据一些情况罗列出类似的“<code>@ComponentScan</code> 使用规则”，但是如果你不明白背后的本质，那么这些只是一些死记硬背的陈述，甚至会带给你错误的认知。</p>
-</blockquote>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="comment">// 标注了两个 `@ComponentScan`，对编译后的字节码进行反编译</span></span><br><span class="line"><span class="meta">@SpringBootApplication(</span></span><br><span class="line"><span class="meta">    scanBasePackages = &#123;&quot;com.example&quot;&#125;</span></span><br><span class="line"><span class="meta">)</span></span><br><span class="line"><span class="meta">@ComponentScans(&#123;@ComponentScan(</span></span><br><span class="line"><span class="meta">    basePackages = &#123;&quot;com.example.demo&quot;&#125;</span></span><br><span class="line"><span class="meta">), @ComponentScan(&#123;&quot;com&quot;&#125;)&#125;)</span></span><br><span class="line"><span class="keyword">public</span> <span class="keyword">class</span> <span class="title class_">DemoApplication</span> &#123;</span><br><span class="line">    <span class="keyword">public</span> <span class="title function_">DemoApplication</span><span class="params">()</span> &#123;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">main</span><span class="params">(String[] args)</span> &#123;</span><br><span class="line">        SpringApplication.run(DemoApplication.class, args);</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+<h4 id="创建线程并启动"><a href="#创建线程并启动" class="headerlink" title="创建线程并启动"></a>创建线程并启动</h4><p><code>Reference-Handler</code> 线程是通过静态代码块创建并启动的。</p>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">static</span> &#123;</span><br><span class="line">    <span class="comment">// 不断获取父线程组，直到最高的系统线程组</span></span><br><span class="line">    <span class="type">ThreadGroup</span> <span class="variable">tg</span> <span class="operator">=</span> Thread.currentThread().getThreadGroup();</span><br><span class="line">    <span class="keyword">for</span> (<span class="type">ThreadGroup</span> <span class="variable">tgn</span> <span class="operator">=</span> tg;</span><br><span class="line">            tgn != <span class="literal">null</span>;</span><br><span class="line">            tg = tgn, tgn = tg.getParent());</span><br><span class="line">    <span class="type">Thread</span> <span class="variable">handler</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">ReferenceHandler</span>(tg, <span class="string">&quot;Reference Handler&quot;</span>);</span><br><span class="line">    <span class="comment">// 设置为最高优先级</span></span><br><span class="line">    handler.setPriority(Thread.MAX_PRIORITY);</span><br><span class="line">    <span class="comment">// 设置为守护线程</span></span><br><span class="line">    handler.setDaemon(<span class="literal">true</span>);</span><br><span class="line">    handler.start();</span><br><span class="line"></span><br><span class="line">    <span class="comment">// provide access in SharedSecrets</span></span><br><span class="line">    <span class="comment">// 不懂，看到一个说法覆盖 JVM 的默认处理方式</span></span><br><span class="line">    SharedSecrets.setJavaLangRefAccess(<span class="keyword">new</span> <span class="title class_">JavaLangRefAccess</span>() &#123;</span><br><span class="line">        <span class="meta">@Override</span></span><br><span class="line">        <span class="keyword">public</span> <span class="type">boolean</span> <span class="title function_">tryHandlePendingReference</span><span class="params">()</span> &#123;</span><br><span class="line">            <span class="keyword">return</span> tryHandlePending(<span class="literal">false</span>);</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;);</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
 
-<h3 id="注解内的别名属性"><a href="#注解内的别名属性" class="headerlink" title="注解内的别名属性"></a>注解内的别名属性</h3><p><code>postProcess</code> 方法完成了组合注解的属性覆盖，可是对于 <code>@ComponentScan</code> 注解而言，它没有被 <code>postProcess</code> 方法处理，它又是如何做到设置 <code>basePackages</code> 等于设置 <code>value</code> 呢？其实这发生在后处理注解属性方法中，该方法会对注解中标注了 <code>@AliasFor</code> 的属性强制执行别名语义。通俗地讲，就是<strong>统一</strong>或<strong>校验</strong>互为别名的属性值，要么只设置了其中一个属性的值，其他别名属性会被赋值为相同的值，要么设置为相同的值，否则会报错。</p>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">static</span> AnnotationAttributes <span class="title function_">getMergedAnnotationAttributes</span><span class="params">(AnnotatedElement element,</span></span><br><span class="line"><span class="params">        String annotationName, <span class="type">boolean</span> classValuesAsString, <span class="type">boolean</span> nestedAnnotationsAsMap)</span> &#123;</span><br><span class="line">    <span class="comment">// 以 get 语义进行搜索（是指找到即终止搜索？）</span></span><br><span class="line">    <span class="type">AnnotationAttributes</span> <span class="variable">attributes</span> <span class="operator">=</span> searchWithGetSemantics(element, <span class="literal">null</span>, annotationName,</span><br><span class="line">            <span class="keyword">new</span> <span class="title class_">MergedAnnotationAttributesProcessor</span>(classValuesAsString, nestedAnnotationsAsMap));</span><br><span class="line">    <span class="comment">// 后处理注解属性</span></span><br><span class="line">    AnnotationUtils.postProcessAnnotationAttributes(element, attributes, classValuesAsString, nestedAnnotationsAsMap);</span><br><span class="line">    <span class="keyword">return</span> attributes;</span><br><span class="line">&#125;</span><br><span class="line"></span><br><span class="line"><span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">postProcessAnnotationAttributes</span><span class="params">(<span class="meta">@Nullable</span> Object annotatedElement,</span></span><br><span class="line"><span class="params">        <span class="meta">@Nullable</span> AnnotationAttributes attributes, <span class="type">boolean</span> classValuesAsString, <span class="type">boolean</span> nestedAnnotationsAsMap)</span> &#123;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">if</span> (attributes == <span class="literal">null</span>) &#123;</span><br><span class="line">        <span class="keyword">return</span>;</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="comment">// 获取 AnnotationAttributes 的注解类型（@ComponentScan）</span></span><br><span class="line">    Class&lt;? <span class="keyword">extends</span> <span class="title class_">Annotation</span>&gt; annotationType = attributes.annotationType();</span><br><span class="line"></span><br><span class="line">    <span class="comment">// Track which attribute values have already been replaced so that we can short</span></span><br><span class="line">    <span class="comment">// circuit the search algorithms.</span></span><br><span class="line">    Set&lt;String&gt; valuesAlreadyReplaced = <span class="keyword">new</span> <span class="title class_">HashSet</span>&lt;&gt;();</span><br><span class="line"></span><br><span class="line">    <span class="keyword">if</span> (!attributes.validated) &#123;</span><br><span class="line">        <span class="comment">// 校验 @AliasFor 配置</span></span><br><span class="line">        <span class="comment">// 获取别名映射</span></span><br><span class="line">        Map&lt;String, List&lt;String&gt;&gt; aliasMap = getAttributeAliasMap(annotationType);</span><br><span class="line">        <span class="comment">// 遍历</span></span><br><span class="line">        <span class="keyword">for</span> (String attributeName : aliasMap.keySet()) &#123;</span><br><span class="line">            <span class="comment">// 跳过已处理的</span></span><br><span class="line">            <span class="keyword">if</span> (valuesAlreadyReplaced.contains(attributeName)) &#123;</span><br><span class="line">                <span class="keyword">continue</span>;</span><br><span class="line">            &#125;</span><br><span class="line">            <span class="type">Object</span> <span class="variable">value</span> <span class="operator">=</span> attributes.get(attributeName);</span><br><span class="line">            <span class="comment">// 属性是否已有值</span></span><br><span class="line">            <span class="type">boolean</span> <span class="variable">valuePresent</span> <span class="operator">=</span> (value != <span class="literal">null</span> &amp;&amp; !(value <span class="keyword">instanceof</span> DefaultValueHolder));</span><br><span class="line">            <span class="comment">// 遍历属性的别名列表</span></span><br><span class="line">            <span class="keyword">for</span> (String aliasedAttributeName : aliasMap.get(attributeName)) &#123;</span><br><span class="line">                <span class="comment">// 跳过已处理的</span></span><br><span class="line">                <span class="keyword">if</span> (valuesAlreadyReplaced.contains(aliasedAttributeName)) &#123;</span><br><span class="line">                    <span class="keyword">continue</span>;</span><br><span class="line">                &#125;</span><br><span class="line">                <span class="comment">// 获取别名属性的值</span></span><br><span class="line">                <span class="type">Object</span> <span class="variable">aliasedValue</span> <span class="operator">=</span> attributes.get(aliasedAttributeName);</span><br><span class="line">                <span class="comment">// 别名属性是否已有值</span></span><br><span class="line">                <span class="type">boolean</span> <span class="variable">aliasPresent</span> <span class="operator">=</span> (aliasedValue != <span class="literal">null</span> &amp;&amp; !(aliasedValue <span class="keyword">instanceof</span> DefaultValueHolder));</span><br><span class="line"></span><br><span class="line">                <span class="comment">// Something to validate or replace with an alias?</span></span><br><span class="line">                <span class="keyword">if</span> (valuePresent || aliasPresent) &#123;</span><br><span class="line">                    <span class="comment">// 如果属性已有值且别名属性也有值，校验是否相等</span></span><br><span class="line">                    <span class="keyword">if</span> (valuePresent &amp;&amp; aliasPresent) &#123;</span><br><span class="line">                        <span class="comment">// Since annotation attributes can be arrays, we must use ObjectUtils.nullSafeEquals().</span></span><br><span class="line">                        <span class="keyword">if</span> (!ObjectUtils.nullSafeEquals(value, aliasedValue)) &#123;</span><br><span class="line">                            <span class="type">String</span> <span class="variable">elementAsString</span> <span class="operator">=</span></span><br><span class="line">                                    (annotatedElement != <span class="literal">null</span> ? annotatedElement.toString() : <span class="string">&quot;unknown element&quot;</span>);</span><br><span class="line">                            <span class="keyword">throw</span> <span class="keyword">new</span> <span class="title class_">AnnotationConfigurationException</span>(String.format(</span><br><span class="line">                                    <span class="string">&quot;In AnnotationAttributes for annotation [%s] declared on %s, &quot;</span> +</span><br><span class="line">                                    <span class="string">&quot;attribute &#x27;%s&#x27; and its alias &#x27;%s&#x27; are declared with values of [%s] and [%s], &quot;</span> +</span><br><span class="line">                                    <span class="string">&quot;but only one is permitted.&quot;</span>, attributes.displayName, elementAsString,</span><br><span class="line">                                    attributeName, aliasedAttributeName, ObjectUtils.nullSafeToString(value),</span><br><span class="line">                                    ObjectUtils.nullSafeToString(aliasedValue)));</span><br><span class="line">                        &#125;</span><br><span class="line">                    &#125;</span><br><span class="line">                    <span class="keyword">else</span> <span class="keyword">if</span> (aliasPresent) &#123;</span><br><span class="line">                        <span class="comment">// 复制别名属性的值给属性</span></span><br><span class="line">                        attributes.put(attributeName,</span><br><span class="line">                                adaptValue(annotatedElement, aliasedValue, classValuesAsString, nestedAnnotationsAsMap));</span><br><span class="line">                        valuesAlreadyReplaced.add(attributeName);</span><br><span class="line">                    &#125;</span><br><span class="line">                    <span class="keyword">else</span> &#123;</span><br><span class="line">                        <span class="comment">// 复制属性的值给别名属性</span></span><br><span class="line">                        attributes.put(aliasedAttributeName,</span><br><span class="line">                                adaptValue(annotatedElement, value, classValuesAsString, nestedAnnotationsAsMap));</span><br><span class="line">                        valuesAlreadyReplaced.add(aliasedAttributeName);</span><br><span class="line">                    &#125;</span><br><span class="line">                &#125;</span><br><span class="line">            &#125;</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="comment">// 校验完毕</span></span><br><span class="line">        attributes.validated = <span class="literal">true</span>;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 将 `value` 从 `DefaultValueHolder` 替换为原始的 `value`</span></span><br><span class="line">    <span class="keyword">for</span> (String attributeName : attributes.keySet()) &#123;</span><br><span class="line">        <span class="keyword">if</span> (valuesAlreadyReplaced.contains(attributeName)) &#123;</span><br><span class="line">            <span class="keyword">continue</span>;</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="type">Object</span> <span class="variable">value</span> <span class="operator">=</span> attributes.get(attributeName);</span><br><span class="line">        <span class="keyword">if</span> (value <span class="keyword">instanceof</span> DefaultValueHolder) &#123;</span><br><span class="line">            value = ((DefaultValueHolder) value).defaultValue;</span><br><span class="line">            attributes.put(attributeName,</span><br><span class="line">                    adaptValue(annotatedElement, value, classValuesAsString, nestedAnnotationsAsMap));</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+<h4 id="run-处理逻辑"><a href="#run-处理逻辑" class="headerlink" title="run 处理逻辑"></a>run 处理逻辑</h4><p><code>run</code> 方法的核心处理逻辑。本质上，<code>ReferenceHandler</code> 线程将 <code>pending</code> 链表上的<code>引用对象</code>分发到各自注册的<code>引用队列</code>中。如果理解了 <code>Reference</code> 作为单链表节点的一面，这部分代码不难理解，反而是其中应对 <code>OOME</code> 的处理很值得关注，但更多的可能是看了个寂寞，不好重现问题并验证。</p>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">static</span> <span class="type">boolean</span> <span class="title function_">tryHandlePending</span><span class="params">(<span class="type">boolean</span> waitForNotify)</span> &#123;</span><br><span class="line">    Reference&lt;Object&gt; r;</span><br><span class="line">    Cleaner c;</span><br><span class="line">    <span class="keyword">try</span> &#123;</span><br><span class="line">        <span class="comment">// 加锁（和垃圾回收共用一个锁）</span></span><br><span class="line">        <span class="keyword">synchronized</span> (lock) &#123;</span><br><span class="line">            <span class="comment">// 如果不为 null</span></span><br><span class="line">            <span class="keyword">if</span> (pending != <span class="literal">null</span>) &#123;</span><br><span class="line">                <span class="comment">// 获取头节点</span></span><br><span class="line">                r = pending;</span><br><span class="line">                <span class="comment">// instanceof 可能抛出 OutOfMemoryError，因此在把 r 从 pending 链表中移除前进行</span></span><br><span class="line">                <span class="comment">// 如果是 Cleaner 类型，进行类型转换，后续有特殊处理</span></span><br><span class="line">                c = r <span class="keyword">instanceof</span> Cleaner ? (Cleaner) r : <span class="literal">null</span>;</span><br><span class="line">                <span class="comment">// 从 pending 链表移除 r</span></span><br><span class="line">                pending = r.discovered;</span><br><span class="line">                r.discovered = <span class="literal">null</span>;</span><br><span class="line">            &#125; <span class="keyword">else</span> &#123;</span><br><span class="line">                <span class="comment">// 等待锁可能抛出 OutOfMemoryError，因为可能需要分配 exception 对象</span></span><br><span class="line">                <span class="keyword">if</span> (waitForNotify) &#123;</span><br><span class="line">                    lock.wait();</span><br><span class="line">                &#125;</span><br><span class="line">                <span class="comment">// retry if waited</span></span><br><span class="line">                <span class="keyword">return</span> waitForNotify;</span><br><span class="line">            &#125;</span><br><span class="line">        &#125;</span><br><span class="line">    &#125; <span class="keyword">catch</span> (OutOfMemoryError x) &#123;</span><br><span class="line">        <span class="comment">// 给其他线程 CPU 时间，以便它们能够丢弃一些存活的引用，然后通过 GC 回收一些空间</span></span><br><span class="line">        <span class="comment">// 还可以防止 CPU 密集运行以至于上面的“r instanceof Cleaner”在一段时间内持续抛出 OOME</span></span><br><span class="line">        Thread.<span class="keyword">yield</span>();</span><br><span class="line">        <span class="comment">// retry</span></span><br><span class="line">        <span class="keyword">return</span> <span class="literal">true</span>;</span><br><span class="line">    &#125; <span class="keyword">catch</span> (InterruptedException x) &#123;</span><br><span class="line">        <span class="comment">// retry</span></span><br><span class="line">        <span class="keyword">return</span> <span class="literal">true</span>;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 如果是 Cleaner 类型，快速清理并返回</span></span><br><span class="line">    <span class="keyword">if</span> (c != <span class="literal">null</span>) &#123;</span><br><span class="line">        c.clean();</span><br><span class="line">        <span class="keyword">return</span> <span class="literal">true</span>;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 如果 Reference 对象关联了引用队列，则添加到队列</span></span><br><span class="line">    ReferenceQueue&lt;? <span class="built_in">super</span> Object&gt; q = r.queue;</span><br><span class="line">    <span class="keyword">if</span> (q != ReferenceQueue.NULL) q.enqueue(r);</span><br><span class="line">    <span class="keyword">return</span> <span class="literal">true</span>;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
 
-<h2 id="总结"><a href="#总结" class="headerlink" title="总结"></a>总结</h2><blockquote>
-<p>又是一篇在写之前自认心里有数，以为可以很快总结完，却不知不觉写了很久，也收获了很多的文章。在刚开始，我只是想接续分析 <code>@Configuration</code> 的思路补充关于 <code>@ComponentScan</code> 的内容，但是渐渐地我又想要回应心里的疑问，<code>@ComponentScan</code> 和 <code>@SpringBootApplication</code> 一起使用的问题的本质原因是什么？<code>Spring</code> 框架真的很好用，好用到你不用太关心背后的原理，好用到你有时候用一个本质上不太正确的结论“走遍天下却几乎不会遇到问题”。说实话，研究完也有点索然无味，尤其是花了这么多时间看自己很讨厌的关于解析的代码，只能说解开了一个卡点也算疏通了一口气，但是时间成本好大啊，得多看点能“面试”的技术啊！！！</p>
-</blockquote>
-<p>综上分析，<code>@SpringBootApplication</code> 的包扫描功能本质上还是 <code>@ComponentScan</code> 提供的，但是和常见的嵌套注解不同，检索 <code>@ComponentScan</code> 有一套独特的算法，导致 <code>@SpringBootApplication</code> 和 <code>@ComponentScan</code> 并非简单的叠加效果。</p>
+<h3 id="关联对象和队列相关方法"><a href="#关联对象和队列相关方法" class="headerlink" title="关联对象和队列相关方法"></a>关联对象和队列相关方法</h3><figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="comment">/* -- Referent accessor and setters -- */</span></span><br><span class="line"></span><br><span class="line"><span class="comment">// 获取关联对象</span></span><br><span class="line"><span class="keyword">public</span> T <span class="title function_">get</span><span class="params">()</span> &#123;</span><br><span class="line">    <span class="keyword">return</span> <span class="built_in">this</span>.referent;</span><br><span class="line">&#125;</span><br><span class="line"></span><br><span class="line"><span class="comment">// 清理关联对象，该操作不会导致引用对象入队</span></span><br><span class="line"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title function_">clear</span><span class="params">()</span> &#123;</span><br><span class="line">    <span class="built_in">this</span>.referent = <span class="literal">null</span>;</span><br><span class="line">&#125;</span><br><span class="line"></span><br><span class="line"><span class="comment">/* -- Queue operations -- */</span></span><br><span class="line"></span><br><span class="line"><span class="comment">// 判断引用对象是否已入队，如果未关联引用队列，则返回 false</span></span><br><span class="line"><span class="keyword">public</span> <span class="type">boolean</span> <span class="title function_">isEnqueued</span><span class="params">()</span> &#123;</span><br><span class="line">    <span class="keyword">return</span> (<span class="built_in">this</span>.queue == ReferenceQueue.ENQUEUED);</span><br><span class="line">&#125;</span><br><span class="line"></span><br><span class="line"><span class="comment">// 将引用对象添加到其注册的引用队列中，该方法仅 Java 代码调用，JVM 不需要调用本方法可以直接进行入队操作（什么情况下？）</span></span><br><span class="line"><span class="keyword">public</span> <span class="type">boolean</span> <span class="title function_">enqueue</span><span class="params">()</span> &#123;</span><br><span class="line">    <span class="keyword">return</span> <span class="built_in">this</span>.queue.enqueue(<span class="built_in">this</span>);</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<h2 id="ReferenceQueue"><a href="#ReferenceQueue" class="headerlink" title="ReferenceQueue"></a>ReferenceQueue</h2><p><code>引用队列</code>，在检测到适当的可达性更改后，垃圾收集器将已注册的<code>引用对象</code>添加到该队列。</p>
+<h3 id="属性-1"><a href="#属性-1" class="headerlink" title="属性"></a>属性</h3><figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">class</span> <span class="title class_">ReferenceQueue</span>&lt;T&gt; &#123;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 构造函数</span></span><br><span class="line">    <span class="keyword">public</span> <span class="title function_">ReferenceQueue</span><span class="params">()</span> &#123; &#125;</span><br><span class="line">    </span><br><span class="line">    <span class="comment">// 一个不可入队的队列</span></span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">static</span> <span class="keyword">class</span> <span class="title class_">Null</span>&lt;S&gt; <span class="keyword">extends</span> <span class="title class_">ReferenceQueue</span>&lt;S&gt; &#123;</span><br><span class="line">        <span class="type">boolean</span> <span class="title function_">enqueue</span><span class="params">(Reference&lt;? extends S&gt; r)</span> &#123;</span><br><span class="line">            <span class="keyword">return</span> <span class="literal">false</span>;</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="comment">// 用于表示一个引用对象没有注册到引用队列</span></span><br><span class="line">    <span class="keyword">static</span> ReferenceQueue&lt;Object&gt; NULL = <span class="keyword">new</span> <span class="title class_">Null</span>&lt;&gt;();</span><br><span class="line">    <span class="comment">// 用于表示一个引用对象已经添加到引用队列</span></span><br><span class="line">    <span class="keyword">static</span> ReferenceQueue&lt;Object&gt; ENQUEUED = <span class="keyword">new</span> <span class="title class_">Null</span>&lt;&gt;();</span><br><span class="line">    </span><br><span class="line">    <span class="comment">// 锁对象</span></span><br><span class="line">    <span class="keyword">static</span> <span class="keyword">private</span> <span class="keyword">class</span> <span class="title class_">Lock</span> &#123; &#125;;</span><br><span class="line">    <span class="keyword">private</span> <span class="type">Lock</span> <span class="variable">lock</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">Lock</span>();</span><br><span class="line">    <span class="comment">// 头节点</span></span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">volatile</span> Reference&lt;? <span class="keyword">extends</span> <span class="title class_">T</span>&gt; head = <span class="literal">null</span>;</span><br><span class="line">    <span class="comment">// 队列长度</span></span><br><span class="line">    <span class="keyword">private</span> <span class="type">long</span> <span class="variable">queueLength</span> <span class="operator">=</span> <span class="number">0</span>;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<h3 id="入队"><a href="#入队" class="headerlink" title="入队"></a>入队</h3><p><code>enqueue</code> 只能由 <code>Reference</code> 类调用。</p>
+<p><code>引用对象</code>的 <code>queue</code> 字段可以表达<code>引用对象</code>的状态：</p>
 <ul>
-<li><code>Spring</code> 会先获取 <code>@ComponentScan</code> 的注解属性再获取 <code>@ComponentScans</code> 的注解属性</li>
-<li>以 <code>@ComponentScan</code> 为例，只获取给定配置类上的注解层次结构中的<strong>第一个</strong> <code>@ComponentScan</code></li>
-<li>先从直接标注的注解开始，再递归地搜索元注解，这一点决定了 <code>@ComponentScan</code> 优先级高于 <code>@SpringBootApplication</code></li>
-<li>使用注解层次结构中较低级别的属性覆盖较高级别的同名（支持 <code>@AliasFor</code>）属性，这一点决定了 <code>@SpringBootApplication</code> 可以设置扫描路径</li>
-<li>多个 <code>@ComponentScan</code> 在编译后隐式生成 <code>@ComponentScans</code>，这一点决定多个 <code>@ComponentScan</code> 彼此之间以及和 <code>@SpringBootApplication</code> 互不冲突</li>
+<li><code>NULL</code>：表示没有注册到<code>引用队列</code>或者已经从<code>引用队列</code>中移除</li>
+<li><code>ENQUEUED</code>：表示已经添加到<code>引用队列</code></li>
+</ul>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="type">boolean</span> <span class="title function_">enqueue</span><span class="params">(Reference&lt;? extends T&gt; r)</span> &#123;</span><br><span class="line">    <span class="keyword">synchronized</span> (lock) &#123;</span><br><span class="line">        <span class="comment">// 检查引用对象的状态是否可以入队</span></span><br><span class="line">        ReferenceQueue&lt;?&gt; queue = r.queue;</span><br><span class="line">        <span class="keyword">if</span> ((queue == NULL) || (queue == ENQUEUED)) &#123;</span><br><span class="line">            <span class="keyword">return</span> <span class="literal">false</span>;</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="comment">// 检查注册的 queue 和调用的 queue 是否相同</span></span><br><span class="line">        <span class="keyword">assert</span> queue == <span class="built_in">this</span>;</span><br><span class="line">        <span class="comment">// 标记为已入队</span></span><br><span class="line">        r.queue = ENQUEUED;</span><br><span class="line">        <span class="comment">// 头插法，最后一个节点的 next 指向自身（为什么？）</span></span><br><span class="line">        r.next = (head == <span class="literal">null</span>) ? r : head;</span><br><span class="line">        head = r;</span><br><span class="line">        <span class="comment">// 队列长度加一</span></span><br><span class="line">        queueLength++;</span><br><span class="line">        <span class="keyword">if</span> (r <span class="keyword">instanceof</span> FinalReference) &#123;</span><br><span class="line">            sun.misc.VM.addFinalRefCount(<span class="number">1</span>);</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="comment">// 通知等待的线程</span></span><br><span class="line">        lock.notifyAll();</span><br><span class="line">        <span class="keyword">return</span> <span class="literal">true</span>;</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<h3 id="出队"><a href="#出队" class="headerlink" title="出队"></a>出队</h3><p>轮询队列以查看是否有引用对象可用，如果存在可用的引用对象则将其从队列中删除并返回，否则该方法立即返回 <code>null</code>。</p>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> Reference&lt;? <span class="keyword">extends</span> <span class="title class_">T</span>&gt; poll() &#123;</span><br><span class="line">    <span class="comment">// 缩小锁的范围</span></span><br><span class="line">    <span class="keyword">if</span> (head == <span class="literal">null</span>)</span><br><span class="line">        <span class="keyword">return</span> <span class="literal">null</span>;</span><br><span class="line">    <span class="keyword">synchronized</span> (lock) &#123;</span><br><span class="line">        <span class="keyword">return</span> reallyPoll();</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br><span class="line"></span><br><span class="line"><span class="keyword">private</span> Reference&lt;? <span class="keyword">extends</span> <span class="title class_">T</span>&gt; reallyPoll() &#123;</span><br><span class="line">    Reference&lt;? <span class="keyword">extends</span> <span class="title class_">T</span>&gt; r = head;</span><br><span class="line">    <span class="keyword">if</span> (r != <span class="literal">null</span>) &#123;</span><br><span class="line">        <span class="meta">@SuppressWarnings(&quot;unchecked&quot;)</span></span><br><span class="line">        Reference&lt;? <span class="keyword">extends</span> <span class="title class_">T</span>&gt; rn = r.next;</span><br><span class="line">        <span class="comment">// 因为尾节点的 next 指向自身</span></span><br><span class="line">        head = (rn == r) ? <span class="literal">null</span> : rn;</span><br><span class="line">        <span class="comment">// 标记为 NULL，避免再次入队</span></span><br><span class="line">        r.queue = NULL;</span><br><span class="line">        <span class="comment">// next 指向自己</span></span><br><span class="line">        r.next = r;</span><br><span class="line">        <span class="comment">// 队列长度减一</span></span><br><span class="line">        queueLength--;</span><br><span class="line">        <span class="keyword">if</span> (r <span class="keyword">instanceof</span> FinalReference) &#123;</span><br><span class="line">            sun.misc.VM.addFinalRefCount(-<span class="number">1</span>);</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="keyword">return</span> r;</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="keyword">return</span> <span class="literal">null</span>;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<p>出队操作提供了等待的选项。</p>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="comment">// 从队列中移除下一个元素，阻塞直到有元素可用。</span></span><br><span class="line"><span class="keyword">public</span> Reference&lt;? <span class="keyword">extends</span> <span class="title class_">T</span>&gt; remove() <span class="keyword">throws</span> InterruptedException &#123;</span><br><span class="line">    <span class="keyword">return</span> remove(<span class="number">0</span>);</span><br><span class="line">&#125;</span><br><span class="line"></span><br><span class="line"><span class="comment">// 从队列中移除下一个元素，阻塞直到超时或有元素可用，timeout 以毫秒为单位。</span></span><br><span class="line"><span class="keyword">public</span> Reference&lt;? <span class="keyword">extends</span> <span class="title class_">T</span>&gt; remove(<span class="type">long</span> timeout)</span><br><span class="line">    <span class="keyword">throws</span> IllegalArgumentException, InterruptedException</span><br><span class="line">&#123;</span><br><span class="line">    <span class="keyword">if</span> (timeout &lt; <span class="number">0</span>) &#123;</span><br><span class="line">        <span class="keyword">throw</span> <span class="keyword">new</span> <span class="title class_">IllegalArgumentException</span>(<span class="string">&quot;Negative timeout value&quot;</span>);</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="keyword">synchronized</span> (lock) &#123;</span><br><span class="line">        Reference&lt;? <span class="keyword">extends</span> <span class="title class_">T</span>&gt; r = reallyPoll();</span><br><span class="line">        <span class="keyword">if</span> (r != <span class="literal">null</span>) <span class="keyword">return</span> r;</span><br><span class="line">        <span class="type">long</span> <span class="variable">start</span> <span class="operator">=</span> (timeout == <span class="number">0</span>) ? <span class="number">0</span> : System.nanoTime();</span><br><span class="line">        <span class="keyword">for</span> (;;) &#123;</span><br><span class="line">            lock.wait(timeout);</span><br><span class="line">            r = reallyPoll();</span><br><span class="line">            <span class="keyword">if</span> (r != <span class="literal">null</span>) <span class="keyword">return</span> r;</span><br><span class="line">            <span class="comment">// 如果 timeout 大于 0</span></span><br><span class="line">            <span class="keyword">if</span> (timeout != <span class="number">0</span>) &#123;</span><br><span class="line">                <span class="type">long</span> <span class="variable">end</span> <span class="operator">=</span> System.nanoTime();</span><br><span class="line">                <span class="comment">// 计算下一轮等待时间</span></span><br><span class="line">                timeout -= (end - start) / <span class="number">1000_000</span>;</span><br><span class="line">                <span class="comment">// 到时间直接返回 null</span></span><br><span class="line">                <span class="keyword">if</span> (timeout &lt;= <span class="number">0</span>) <span class="keyword">return</span> <span class="literal">null</span>;</span><br><span class="line">                <span class="comment">// 更新开始时间</span></span><br><span class="line">                start = end;</span><br><span class="line">            &#125;</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<h3 id="状态变化"><a href="#状态变化" class="headerlink" title="状态变化"></a>状态变化</h3><p><code>Reference</code> 实例（引用对象）可能处于四种内部状态之一：</p>
+<ul>
+<li><code>Active</code>: 新创建的实例处于 <code>Active</code> 状态，受到垃圾收集器的特殊处理。收集器在检测到<code>关联对象</code>的可达性变为适当状态后的一段时间，会将实例的状态更改为 <code>Pending</code> 或 <code>Inactive</code>，具体取决于实例在创建时是否注册到<code>引用队列</code>中。在前一种情况下，它还会将实例添加到待 <code>pending-Reference</code> 列表中。</li>
+<li><code>Pending</code>: 实例处在 <code>pending-Reference</code> 列表中，等待 <code>Reference-Handler</code> 线程将其加入<code>引用队列</code>。未注册到<code>引用队列</code>的实例永远不会处于这种状态。</li>
+<li><code>Enqueued</code>: 处在创建实例时注册到的<code>引用队列</code>中。当实例从引用队列中删除时，该实例将变为 <code>Inactive</code> 状态。未注册到<code>引用队列</code>的实例永远不会处于这种状态。</li>
+<li><code>Inactive</code>: 没有进一步的操作。一旦实例变为 <code>Inactive</code> 状态，其状态将永远不会再改变。</li>
+</ul>
+<p><code>Reference</code> 实例（引用对象）的状态由 <code>queue</code> 和 <code>next</code> 字段共同表达：</p>
+<ul>
+<li><code>Active</code>: <code>(queue == ReferenceQueue || queue == ReferenceQueue.NULL) &amp;&amp; next == null</code></li>
+<li><code>Pending</code>: <code>queue == ReferenceQueue &amp;&amp; next == this</code></li>
+<li><code>Enqueued</code>: <code>queue == ReferenceQueue.ENQUEUED &amp;&amp; (next == Following || this)</code>（在队列末尾时，<code>next</code> 指向自身，目前没有体现出这么设计的必要性啊？）</li>
+<li><code>Inactive</code>: <code>queue == ReferenceQueue.NULL &amp;&amp; next == this</code></li>
+</ul>
+<div style="width:70%;margin:auto"><img src="/2023/12/27/source-code-analysis-of-Java-class-Reference/Pasted%20image%2020231227235157.png" class="" title="Reference 相关类图"></div>
+
+<h2 id="Reference-的子类"><a href="#Reference-的子类" class="headerlink" title="Reference 的子类"></a>Reference 的子类</h2><h2 id="参考文章"><a href="#参考文章" class="headerlink" title="参考文章"></a>参考文章</h2><ul>
+<li><a href="https://cloud.tencent.com/developer/article/1366147">你不可不知的Java引用类型之——Reference源码解析</a></li>
+<li><a href="https://www.jianshu.com/p/9fd68714c366">Java引用类型之：Reference源码解析</a></li>
+<li><a href="https://juejin.cn/post/6942026483489734693">JVM之Reference源码分析</a></li>
 </ul>
 ]]></content>
       <tags>
         <tag>java</tag>
-        <tag>spring</tag>
-        <tag>spring boot</tag>
       </tags>
   </entry>
   <entry>
@@ -6088,7 +5722,131 @@
 </ul>
 ]]></content>
       <tags>
-        <tag>mysql</tag>
+        <tag>mysql</tag>
+      </tags>
+  </entry>
+  <entry>
+    <title>探索 Java 类 Cleaner 和 Finalizer</title>
+    <url>/2023/12/28/explore-the-Java-classes-Cleaner-and-Finalizer/</url>
+    <content><![CDATA[<p><code>Java</code> 类 <code>Cleaner</code> 和 <code>Finalizer</code> 都实现了一种 <code>finalization</code> 机制，前者更轻量和强大，你可能在了解 <code>NIO</code> 的堆外内存自动释放机制中注意过它；后者为人所诟病，<code>finalize</code> 方法被人强烈反对使用。本文想要解析它们的原因不在于它们实现的功能，而在于它们是 <code>Reference</code> 的具体子类。<br><code>Reference</code> 作为和 <code>GC</code> 紧密联系的类，你可能从很多文字描述中了解过 <code>SoftReference</code>、<code>WeakReference</code> 还有 <code>PhantomReference</code> 但是却很少从代码层面了解过它们，当你牢记“一个对象是否可以被回收的判断依据是它是否从 <code>Root</code> 对象可达”这条规则再面对 <code>Reference</code> 的子类时是否产生过割裂感；你是否好奇过 <code>Finalizer</code> 如何和重写 <code>finalize</code> 方法的类产生联系，本文将从 <code>Cleaner</code> 和 <code>Finalizer</code> 的源码揭示一些你可能已知的结论背后的朴素原理。</p>
+<span id="more"></span>
+
+<blockquote>
+<p>本文的写作动机继承自 <a href="/2023/12/27/source-code-analysis-of-Java-class-Reference/" title="Java 类 Reference 的源码分析">Java 类 Reference 的源码分析</a>，有时候也会自我怀疑研究一个涉及大家极力劝阻使用的 <code>finalize</code> 是否浪费精力，只能说确实如此！要不是半途而废会膈应难受肯定就停了！只能说这个过程确实帮助自己对 <code>Java</code> 引用和 <code>GC</code> 对其的处理有更加深刻的理解。</p>
+</blockquote>
+<h2 id="虚引用之-Cleaner"><a href="#虚引用之-Cleaner" class="headerlink" title="虚引用之 Cleaner"></a>虚引用之 Cleaner</h2><h3 id="虚引用介绍"><a href="#虚引用介绍" class="headerlink" title="虚引用介绍"></a>虚引用介绍</h3><p><code>PhantomReference</code> 对象在垃圾收集器确定其<code>关联对象</code>可以被回收时或可以被回收后一段时间，将被入队。“可以被回收”更明确的描述是“虚引用的<code>关联对象</code>变成 <strong><code>phantom reachable</code></strong> ，即只有虚引用引用了它”。但是和软引用和弱引用不同，<strong>当虚引用入队时并不会被垃圾收集器自动清理（其关联对象）</strong>。一个 <code>phantom reachable</code> 的对象会一直维持原样直到所有虚引用被清理或者它们自身变得不可达。</p>
+<p><code>PhantomReference</code> 的代码非常简单：</p>
+<ol>
+<li><code>PhantomReference</code> 仅提供了一个 <code>public</code> 构造函数，必须提供 <code>ReferenceQueue</code> 参数。它不像 <code>SoftReference</code> 和 <code>WeakReference</code> 可以离开 <code>ReferenceQueue</code> 单独使用，尽管 <code>queue</code> 可以为 <code>null</code>，但是这样做并没有意义。</li>
+<li><code>get()</code> 返回 <code>null</code>，这意味着不能通过 <code>PhantomReference</code> 获取其关联的对象 <code>referent</code>。</li>
+</ol>
+<blockquote>
+<p><code>get()</code> 返回 <code>null</code> 并不是可以随意忽略的事情，它保证了 <code>phantom reachable</code> 对象不会被重新触达和修改（这是为清理工作留出时间吗）。</p>
+</blockquote>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">class</span> <span class="title class_">PhantomReference</span>&lt;T&gt; <span class="keyword">extends</span> <span class="title class_">Reference</span>&lt;T&gt; &#123;</span><br><span class="line">    <span class="keyword">public</span> T <span class="title function_">get</span><span class="params">()</span> &#123;</span><br><span class="line">        <span class="keyword">return</span> <span class="literal">null</span>;</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="keyword">public</span> <span class="title function_">PhantomReference</span><span class="params">(T referent, ReferenceQueue&lt;? <span class="built_in">super</span> T&gt; q)</span> &#123;</span><br><span class="line">        <span class="built_in">super</span>(referent, q);</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<p>通过以下示例验证 <code>GC</code> 不会自动清理虚引用的关联对象：</p>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">main</span><span class="params">(String[] args)</span> <span class="keyword">throws</span> InterruptedException &#123;</span><br><span class="line">    <span class="type">Scanner</span> <span class="variable">scanner</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">Scanner</span>(System.in);</span><br><span class="line"></span><br><span class="line">    <span class="type">byte</span>[] bytes = <span class="keyword">new</span> <span class="title class_">byte</span>[<span class="number">100</span> * <span class="number">1024</span> * <span class="number">1024</span>];</span><br><span class="line">    ReferenceQueue&lt;<span class="type">byte</span>[]&gt; queue = <span class="keyword">new</span> <span class="title class_">ReferenceQueue</span>&lt;&gt;();</span><br><span class="line">    PhantomReference&lt;<span class="type">byte</span>[]&gt; phantomReference = <span class="keyword">new</span> <span class="title class_">PhantomReference</span>&lt;&gt;(bytes, queue);</span><br><span class="line"></span><br><span class="line">    <span class="type">Thread</span> <span class="variable">thread</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">Thread</span>(() -&gt; &#123;</span><br><span class="line">        <span class="keyword">for</span> (; ; ) &#123;</span><br><span class="line">            <span class="keyword">try</span> &#123;</span><br><span class="line">                Reference&lt;? <span class="keyword">extends</span> <span class="title class_">byte</span>[]&gt; remove = queue.remove(<span class="number">0</span>);</span><br><span class="line">                System.out.println(remove + <span class="string">&quot; enqueued&quot;</span>);</span><br><span class="line">                <span class="comment">// 需要调用 clear 主动清理关联对象，可以验证 gc 后总堆内存占用下降</span></span><br><span class="line">                <span class="comment">// remove.clear();</span></span><br><span class="line">                <span class="comment">// System.gc();</span></span><br><span class="line">            &#125; <span class="keyword">catch</span> (InterruptedException e) &#123;</span><br><span class="line">                System.out.println(Thread.currentThread().getName() + <span class="string">&quot; interrupt&quot;</span>);</span><br><span class="line">                <span class="keyword">break</span>;</span><br><span class="line">            &#125;</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;);</span><br><span class="line">    thread.start();</span><br><span class="line"></span><br><span class="line">    System.out.println(<span class="string">&quot;暂停查看堆内存占用&quot;</span>);</span><br><span class="line">    scanner.next();</span><br><span class="line"></span><br><span class="line">    bytes = <span class="literal">null</span>;</span><br><span class="line">    System.gc();</span><br><span class="line">    System.out.println(<span class="string">&quot;gc 后 sleep 3s，查看总堆内存占用未下降&quot;</span>);</span><br><span class="line">    TimeUnit.SECONDS.sleep(<span class="number">3</span>);</span><br><span class="line"></span><br><span class="line">    scanner.next();</span><br><span class="line">    thread.interrupt();</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<h3 id="Cleaner-介绍"><a href="#Cleaner-介绍" class="headerlink" title="Cleaner 介绍"></a>Cleaner 介绍</h3><p>虚引用最常用于以比 <code>finalization</code> 更灵活的方式安排清理工作，比如其子类 <code>Cleaner</code> 就是一种基于虚引用的清理器，它比 <code>finalization</code> 更轻量但更强大。<code>Cleaner</code> 追踪其<code>关联对象</code>并封装任意的清理代码，在 <code>GC</code> 检测到其<code>关联对象</code>变成 <code>phantom reachable</code> 后一段时间，<code>Reference-Handler</code> 线程将运行清理代码。同时 <code>Cleaner</code> 可以被直接调用，它是线程安全的并且可以保证清理代码最多运行一次。但是 <code>Cleaner</code> 不是 <code>finalization</code> 的替代品，为了避免阻塞 <code>Reference-Handler</code> 线程，清理代码应极其简单和直接。</p>
+<h3 id="构造函数"><a href="#构造函数" class="headerlink" title="构造函数"></a>构造函数</h3><p><code>Cleaner</code> 的构造函数为 <code>private</code>，仅可通过 <code>create</code> 方法创建实例。</p>
+<ul>
+<li><code>referent</code>: <code>关联对象</code></li>
+<li><code>dummyQueue</code>: 假队列，需要它仅仅是因为 <code>PhantomReference</code> 的构造函数需要一个 <code>queue</code> 参数，但是这个 <code>queue</code> 完全没用，在 <code>Reference</code> 中 <code>Reference-Handler</code> 线程会显式调用 <code>cleaners</code> 而不会执行入队操作。</li>
+</ul>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">class</span> <span class="title class_">Cleaner</span> <span class="keyword">extends</span> <span class="title class_">PhantomReference</span>&lt;Object&gt; &#123;</span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">static</span> <span class="keyword">final</span> ReferenceQueue&lt;Object&gt; dummyQueue = <span class="keyword">new</span> <span class="title class_">ReferenceQueue</span>&lt;&gt;();</span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">final</span> Runnable thunk;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">private</span> <span class="title function_">Cleaner</span><span class="params">(Object referent, Runnable thunk)</span> &#123;</span><br><span class="line">        <span class="built_in">super</span>(referent, dummyQueue);</span><br><span class="line">        <span class="built_in">this</span>.thunk = thunk;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">public</span> <span class="keyword">static</span> Cleaner <span class="title function_">create</span><span class="params">(Object ob, Runnable thunk)</span> &#123;</span><br><span class="line">        <span class="keyword">if</span> (thunk == <span class="literal">null</span>)</span><br><span class="line">            <span class="keyword">return</span> <span class="literal">null</span>;</span><br><span class="line">        <span class="comment">// 添加到 Cleaner 自身维护的双链表</span></span><br><span class="line">        <span class="keyword">return</span> add(<span class="keyword">new</span> <span class="title class_">Cleaner</span>(ob, thunk));</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<h3 id="添加-cleaner"><a href="#添加-cleaner" class="headerlink" title="添加 cleaner"></a>添加 <code>cleaner</code></h3><ul>
+<li>使用 <code>synchronized</code> 同步</li>
+<li><code>Cleaner</code> 自身维护一个双向链表存储 <code>cleaners</code>，通过静态变量 <code>first</code> 存储头节点，以防止 <code>cleaners</code> 比其<code>关联对象</code>更早被 <code>GC</code>。</li>
+</ul>
+<div style="width:70%;margin:auto"><img src="/2023/12/28/explore-the-Java-classes-Cleaner-and-Finalizer/Pasted%20image%2020231228220806.png" class="" title="Cleaner 双向链表"></div>
+
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="comment">// 头节点</span></span><br><span class="line"><span class="keyword">static</span> <span class="keyword">private</span> <span class="type">Cleaner</span> <span class="variable">first</span> <span class="operator">=</span> <span class="literal">null</span>;</span><br><span class="line"><span class="comment">// 双向指针</span></span><br><span class="line"><span class="keyword">private</span> <span class="type">Cleaner</span> <span class="variable">next</span> <span class="operator">=</span> <span class="literal">null</span>, prev = <span class="literal">null</span>;</span><br><span class="line"><span class="keyword">private</span> <span class="keyword">static</span> <span class="keyword">synchronized</span> Cleaner <span class="title function_">add</span><span class="params">(Cleaner cl)</span> &#123;</span><br><span class="line">    <span class="comment">// 头插法</span></span><br><span class="line">    <span class="keyword">if</span> (first != <span class="literal">null</span>) &#123;</span><br><span class="line">        cl.next = first;</span><br><span class="line">        first.prev = cl;</span><br><span class="line">    &#125;</span><br><span class="line">    first = cl;</span><br><span class="line">    <span class="keyword">return</span> cl;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<h3 id="clean-方法"><a href="#clean-方法" class="headerlink" title="clean 方法"></a>clean 方法</h3><p>在 <code>Reference</code> 中 <code>Reference-Handler</code> 线程对于 <code>Cleaner</code> 类型的对象，会显式地调用其 <code>clean</code> 方法并返回，而不会将其入队。</p>
+<ol>
+<li>使用 <code>synchronized</code> 同步，从双链表上移除自身</li>
+<li>调用 <code>thunk</code> 的 <code>run</code> 方法</li>
+</ol>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title function_">clean</span><span class="params">()</span> &#123;</span><br><span class="line">    <span class="keyword">if</span> (!remove(<span class="built_in">this</span>))</span><br><span class="line">        <span class="keyword">return</span>;</span><br><span class="line">    <span class="keyword">try</span> &#123;</span><br><span class="line">        thunk.run();</span><br><span class="line">    &#125; <span class="keyword">catch</span> (<span class="keyword">final</span> Throwable x) &#123;</span><br><span class="line">        AccessController.doPrivileged(<span class="keyword">new</span> <span class="title class_">PrivilegedAction</span>&lt;Void&gt;() &#123;</span><br><span class="line">            <span class="keyword">public</span> Void <span class="title function_">run</span><span class="params">()</span> &#123;</span><br><span class="line">                <span class="keyword">if</span> (System.err != <span class="literal">null</span>)</span><br><span class="line">                    <span class="keyword">new</span> <span class="title class_">Error</span>(<span class="string">&quot;Cleaner terminated abnormally&quot;</span>, x).printStackTrace();</span><br><span class="line">                System.exit(<span class="number">1</span>);</span><br><span class="line">                <span class="keyword">return</span> <span class="literal">null</span>;</span><br><span class="line">            &#125;</span><br><span class="line">        &#125;);</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br><span class="line"></span><br><span class="line"><span class="keyword">private</span> <span class="keyword">static</span> <span class="keyword">synchronized</span> <span class="type">boolean</span> <span class="title function_">remove</span><span class="params">(Cleaner cl)</span> &#123;</span><br><span class="line">    <span class="comment">// next 指针指向自身代表已经移除，可以避免重复移除和执行</span></span><br><span class="line">    <span class="keyword">if</span> (cl.next == cl)</span><br><span class="line">        <span class="keyword">return</span> <span class="literal">false</span>;</span><br><span class="line">    <span class="comment">// 更新双链表</span></span><br><span class="line">    <span class="keyword">if</span> (first == cl) &#123;</span><br><span class="line">        <span class="keyword">if</span> (cl.next != <span class="literal">null</span>)</span><br><span class="line">            first = cl.next;</span><br><span class="line">        <span class="keyword">else</span></span><br><span class="line">            first = cl.prev;</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="keyword">if</span> (cl.next != <span class="literal">null</span>)</span><br><span class="line">        cl.next.prev = cl.prev;</span><br><span class="line">    <span class="keyword">if</span> (cl.prev != <span class="literal">null</span>)</span><br><span class="line">        cl.prev.next = cl.next;</span><br><span class="line">    <span class="comment">// 通过将 next 指针指向自身表示已经被移除</span></span><br><span class="line">    cl.next = cl;</span><br><span class="line">    cl.prev = cl;</span><br><span class="line">    <span class="keyword">return</span> <span class="literal">true</span>;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<h3 id="Cleaner-处理流程"><a href="#Cleaner-处理流程" class="headerlink" title="Cleaner 处理流程"></a>Cleaner 处理流程</h3><ul>
+<li>创建的 <code>Cleaner</code> 对象被 <code>Cleaner</code> 类的双链表直接或间接引用（强引用），因此不会被垃圾回收</li>
+<li>一切的起点仍然是 <code>GC</code> 特殊地对待虚引用的关联对象，当关联对象从 <code>reachable</code> 变成 <code>phantom reachable</code>，<code>GC</code> 将 <code>Cleaner</code> 对象将加入 <code>pending-list</code></li>
+<li><code>Reference-Handler</code> 线程又将其移除并调用 <code>clean</code> 方法</li>
+<li>在调用完毕后，<code>Cleaner</code> 对象变成 <code>unreachable</code> 并最终被垃圾回收，其关联对象也被垃圾回收</li>
+</ul>
+<blockquote>
+<p>注意，Cleaner 对象本身在被调用完毕之前始终是被静态变量引用，是 <code>reachable</code> 的，我们讨论的被判定为可回收的、变成 <code>phantom reachable</code> 状态的是关联对象。</p>
+</blockquote>
+<div style="width:70%;margin:auto"><img src="/2023/12/28/explore-the-Java-classes-Cleaner-and-Finalizer/Pasted%20image%2020231229012917.png" class="" title="Cleaner 处理流程"></div>
+
+<blockquote>
+<p>事实上，个人猜测“虚引用的关联对象不像软引用和弱引用会被自动清理”描述的仅仅是一个表象，判断是否要被垃圾回收的根本法则仍然是“对象是否从 <code>Root</code> 对象可达”，软引用和弱引用的<code>关联对象</code>之所以会被垃圾回收是因为它们在加入 <code>pending-list</code> 时被从<code>引用对象</code>断开，否则当<code>引用对象</code>被添加到<code>引用队列</code>时，<code>引用队列</code>如果从 <code>Root</code> 对象可达，将导致<code>关联对象</code>也从 <code>Root</code> 对象可达。在 <code>Reference</code> 的 <code>clear()</code> 的注释中提及该方法只被 <code>Java</code> 代码调用，<code>GC</code> 不需要调用该方法就可以直接清理，肯定是 <code>GC</code> 有直接清理<code>关联对象</code>的场景。同时 <code>Reference</code> 类有一句注释“<code>GC</code> 在检测到<code>关联对象</code>有特定的可达性变化后，将把<code>引用对象</code>添加到<code>引用队列</code>”，它并未将特定的可达性变化直接描述为<code>关联对象</code>变为不可达。目前尚未从 <code>JVM</code> 源代码验证该猜测。</p>
+</blockquote>
+<h2 id="终结引用之-Finalizer"><a href="#终结引用之-Finalizer" class="headerlink" title="终结引用之 Finalizer"></a>终结引用之 Finalizer</h2><p><code>FinalReference</code> 用于实现 <code>finalization</code>，其代码很简单。</p>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">class</span> <span class="title class_">FinalReference</span>&lt;T&gt; <span class="keyword">extends</span> <span class="title class_">Reference</span>&lt;T&gt; &#123;</span><br><span class="line">    <span class="keyword">public</span> <span class="title function_">FinalReference</span><span class="params">(T referent, ReferenceQueue&lt;? <span class="built_in">super</span> T&gt; q)</span> &#123;</span><br><span class="line">        <span class="built_in">super</span>(referent, q);</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<p>其子类 <code>Finalizer</code> 继承自 <code>FinalReference</code>，<code>Cleaner</code> 在代码设计上和它非常相似。</p>
+<h3 id="构造函数-1"><a href="#构造函数-1" class="headerlink" title="构造函数"></a>构造函数</h3><p><code>Finalizer</code> 的构造函数为 <code>private</code>，仅可通过 <code>register</code> 方法创建实例。</p>
+<ul>
+<li><code>finalizee</code>: <code>关联对象</code>，即重写了 <code>finalize</code> 方法的类的实例</li>
+<li><code>queue</code>: 引用队列</li>
+</ul>
+<blockquote>
+<p>根据注释 <code>register</code> 由 <code>VM</code> 调用，我们可以合理猜测，这里就是重写了 <code>finalize</code> 方法的类的实例和 <code>Finalizer</code> 对象关联的起点。</p>
+</blockquote>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">final</span> <span class="keyword">class</span> <span class="title class_">Finalizer</span> <span class="keyword">extends</span> <span class="title class_">FinalReference</span>&lt;Object&gt; &#123;</span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">static</span> ReferenceQueue&lt;Object&gt; queue = <span class="keyword">new</span> <span class="title class_">ReferenceQueue</span>&lt;&gt;();</span><br><span class="line"></span><br><span class="line">    <span class="keyword">private</span> <span class="title function_">Finalizer</span><span class="params">(Object finalizee)</span> &#123;</span><br><span class="line">        <span class="built_in">super</span>(finalizee, queue);</span><br><span class="line">        add();</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="comment">// 由 VM 调用</span></span><br><span class="line">    <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">register</span><span class="params">(Object finalizee)</span> &#123;</span><br><span class="line">        <span class="keyword">new</span> <span class="title class_">Finalizer</span>(finalizee);</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<h3 id="添加-Finalizer"><a href="#添加-Finalizer" class="headerlink" title="添加 Finalizer"></a>添加 <code>Finalizer</code></h3><ul>
+<li>使用 <code>synchronized</code> 同步</li>
+<li><code>Finalizer</code> 自身维护一个双向链表存储 <code>finalizers</code>，通过静态变量 <code>unfinalized</code> 存储头节点</li>
+</ul>
+<div style="width:70%;margin:auto"><img src="/2023/12/28/explore-the-Java-classes-Cleaner-and-Finalizer/Pasted%20image%2020231228230444.png" class="" title="Finalizer 双向链表"></div>
+
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">private</span> <span class="keyword">static</span> <span class="type">Finalizer</span> <span class="variable">unfinalized</span> <span class="operator">=</span> <span class="literal">null</span>;</span><br><span class="line"><span class="keyword">private</span> <span class="keyword">static</span> <span class="keyword">final</span> <span class="type">Object</span> <span class="variable">lock</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">Object</span>();</span><br><span class="line"><span class="keyword">private</span> <span class="type">Finalizer</span> <span class="variable">next</span> <span class="operator">=</span> <span class="literal">null</span>, prev = <span class="literal">null</span>;</span><br><span class="line"></span><br><span class="line"><span class="keyword">private</span> <span class="keyword">void</span> <span class="title function_">add</span><span class="params">()</span> &#123;</span><br><span class="line">    <span class="keyword">synchronized</span> (lock) &#123;</span><br><span class="line">        <span class="keyword">if</span> (unfinalized != <span class="literal">null</span>) &#123;</span><br><span class="line">            <span class="built_in">this</span>.next = unfinalized;</span><br><span class="line">            unfinalized.prev = <span class="built_in">this</span>;</span><br><span class="line">        &#125;</span><br><span class="line">        unfinalized = <span class="built_in">this</span>;</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<h3 id="Finalizer-线程"><a href="#Finalizer-线程" class="headerlink" title="Finalizer 线程"></a><code>Finalizer</code> 线程</h3><p><code>finalizers</code> 的清理通常是由一条名为 <code>Finalizer</code> 的线程处理。启动任意一个非常简单的 <code>Java</code> 程序，通过 <code>JVM</code> 相关的工具，比如 <code>JConsole</code>，你都能看到一个名为 <code>Finalizer</code> 的线程。</p>
+<div style="width:70%;margin:auto"><img src="/2023/12/28/explore-the-Java-classes-Cleaner-and-Finalizer/Snipaste_2023-12-28_23-09-21.png" class="" title="Finalizer 线程"></div>
+
+<h4 id="run-方法"><a href="#run-方法" class="headerlink" title="run 方法"></a>run 方法</h4><figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">private</span> <span class="keyword">static</span> <span class="keyword">class</span> <span class="title class_">FinalizerThread</span> <span class="keyword">extends</span> <span class="title class_">Thread</span> &#123;</span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">volatile</span> <span class="type">boolean</span> running;</span><br><span class="line">    FinalizerThread(ThreadGroup g) &#123;</span><br><span class="line">        <span class="built_in">super</span>(g, <span class="string">&quot;Finalizer&quot;</span>);</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="keyword">public</span> <span class="keyword">void</span> <span class="title function_">run</span><span class="params">()</span> &#123;</span><br><span class="line">        <span class="comment">// 防止递归调用 run（什么场景？）</span></span><br><span class="line">        <span class="keyword">if</span> (running)</span><br><span class="line">            <span class="keyword">return</span>;</span><br><span class="line">        <span class="comment">// Finalizer thread 在 System.initializeSystemClass 被调用前启动，等待 JavaLangAccess 可用</span></span><br><span class="line">        <span class="keyword">while</span> (!VM.isBooted()) &#123;</span><br><span class="line">            <span class="comment">// 推迟直到 VM 初始化完成</span></span><br><span class="line">            <span class="keyword">try</span> &#123;</span><br><span class="line">                VM.awaitBooted();</span><br><span class="line">            &#125; <span class="keyword">catch</span> (InterruptedException x) &#123;</span><br><span class="line">                <span class="comment">// 忽略并继续</span></span><br><span class="line">            &#125;</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="keyword">final</span> <span class="type">JavaLangAccess</span> <span class="variable">jla</span> <span class="operator">=</span> SharedSecrets.getJavaLangAccess();</span><br><span class="line">        <span class="comment">// 标记为运行中</span></span><br><span class="line">        running = <span class="literal">true</span>;</span><br><span class="line">        <span class="keyword">for</span> (;;) &#123;</span><br><span class="line">            <span class="keyword">try</span> &#123;</span><br><span class="line">                <span class="comment">// 从队列中移除</span></span><br><span class="line">                <span class="type">Finalizer</span> <span class="variable">f</span> <span class="operator">=</span> (Finalizer)queue.remove();</span><br><span class="line">                <span class="comment">// 调用 runFinalizer</span></span><br><span class="line">                f.runFinalizer(jla);</span><br><span class="line">            &#125; <span class="keyword">catch</span> (InterruptedException x) &#123;</span><br><span class="line">                <span class="comment">// 忽略并继续</span></span><br><span class="line">            &#125;</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<h4 id="创建和启动"><a href="#创建和启动" class="headerlink" title="创建和启动"></a>创建和启动</h4><p><code>Finalizer</code> 线程是通过静态代码块创建和启动的。</p>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">static</span> &#123;</span><br><span class="line">    <span class="comment">// 向上获取父线程组，直到系统线程组</span></span><br><span class="line">    <span class="type">ThreadGroup</span> <span class="variable">tg</span> <span class="operator">=</span> Thread.currentThread().getThreadGroup();</span><br><span class="line">    <span class="keyword">for</span> (<span class="type">ThreadGroup</span> <span class="variable">tgn</span> <span class="operator">=</span> tg;</span><br><span class="line">            tgn != <span class="literal">null</span>;</span><br><span class="line">            tg = tgn, tgn = tg.getParent());</span><br><span class="line">    <span class="comment">// 创建 FinalizerThread 并启动</span></span><br><span class="line">    <span class="type">Thread</span> <span class="variable">finalizer</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">FinalizerThread</span>(tg);</span><br><span class="line">    <span class="comment">// 设置优先级为最高减 2</span></span><br><span class="line">    finalizer.setPriority(Thread.MAX_PRIORITY - <span class="number">2</span>);</span><br><span class="line">    finalizer.setDaemon(<span class="literal">true</span>);</span><br><span class="line">    finalizer.start();</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<h4 id="获取-Finalizer-并调用"><a href="#获取-Finalizer-并调用" class="headerlink" title="获取 Finalizer 并调用"></a>获取 Finalizer 并调用</h4><figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">private</span> <span class="keyword">void</span> <span class="title function_">runFinalizer</span><span class="params">(JavaLangAccess jla)</span> &#123;</span><br><span class="line">    <span class="keyword">synchronized</span> (<span class="built_in">this</span>) &#123;</span><br><span class="line">        <span class="comment">// 判断是否已经终结过</span></span><br><span class="line">        <span class="keyword">if</span> (hasBeenFinalized()) <span class="keyword">return</span>;</span><br><span class="line">        <span class="comment">// 从双链表上移除</span></span><br><span class="line">        remove();</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="keyword">try</span> &#123;</span><br><span class="line">        <span class="comment">// 获取关联的 finalizee</span></span><br><span class="line">        <span class="type">Object</span> <span class="variable">finalizee</span> <span class="operator">=</span> <span class="built_in">this</span>.get();</span><br><span class="line">        <span class="comment">// 如果不为 null 且不是 Enum 类型</span></span><br><span class="line">        <span class="keyword">if</span> (finalizee != <span class="literal">null</span> &amp;&amp; !(finalizee <span class="keyword">instanceof</span> java.lang.Enum)) &#123;</span><br><span class="line">            <span class="comment">// 调用 invokeFinalize</span></span><br><span class="line">            jla.invokeFinalize(finalizee);</span><br><span class="line">            <span class="comment">// 清理栈槽以降低保守 GC 时误保留的可能性</span></span><br><span class="line">            finalizee = <span class="literal">null</span>;</span><br><span class="line">        &#125;</span><br><span class="line">    &#125; <span class="keyword">catch</span> (Throwable x) &#123; &#125;</span><br><span class="line">    <span class="comment">// 清理关联对象</span></span><br><span class="line">    <span class="built_in">super</span>.clear();</span><br><span class="line">&#125;</span><br><span class="line"></span><br><span class="line"><span class="comment">// 和 Cleaner 类似，使用 next 指向自身表示已被移除</span></span><br><span class="line"><span class="keyword">private</span> <span class="type">boolean</span> <span class="title function_">hasBeenFinalized</span><span class="params">()</span> &#123;</span><br><span class="line">    <span class="keyword">return</span> (next == <span class="built_in">this</span>);</span><br><span class="line">&#125;</span><br><span class="line"></span><br><span class="line"><span class="comment">// 和 Cleaner 类似的处理</span></span><br><span class="line"><span class="keyword">private</span> <span class="keyword">void</span> <span class="title function_">remove</span><span class="params">()</span> &#123;</span><br><span class="line">    <span class="keyword">synchronized</span> (lock) &#123;</span><br><span class="line">        <span class="keyword">if</span> (unfinalized == <span class="built_in">this</span>) &#123;</span><br><span class="line">            <span class="keyword">if</span> (<span class="built_in">this</span>.next != <span class="literal">null</span>) &#123;</span><br><span class="line">                unfinalized = <span class="built_in">this</span>.next;</span><br><span class="line">            &#125; <span class="keyword">else</span> &#123;</span><br><span class="line">                unfinalized = <span class="built_in">this</span>.prev;</span><br><span class="line">            &#125;</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="keyword">if</span> (<span class="built_in">this</span>.next != <span class="literal">null</span>) &#123;</span><br><span class="line">            <span class="built_in">this</span>.next.prev = <span class="built_in">this</span>.prev;</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="keyword">if</span> (<span class="built_in">this</span>.prev != <span class="literal">null</span>) &#123;</span><br><span class="line">            <span class="built_in">this</span>.prev.next = <span class="built_in">this</span>.next;</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="built_in">this</span>.next = <span class="built_in">this</span>;</span><br><span class="line">        <span class="built_in">this</span>.prev = <span class="built_in">this</span>;</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<h3 id="finalize-的调用原理"><a href="#finalize-的调用原理" class="headerlink" title="finalize 的调用原理"></a>finalize 的调用原理</h3><p>关于如何调用 <code>finalize</code> 方法涉及不少平时接触不到的代码。</p>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="comment">// 获取 JavaLangAccess</span></span><br><span class="line"><span class="keyword">final</span> <span class="type">JavaLangAccess</span> <span class="variable">jla</span> <span class="operator">=</span> SharedSecrets.getJavaLangAccess();</span><br><span class="line"><span class="comment">// 通过 JavaLangAccess 调用 finalizee 的 finalize 方法</span></span><br><span class="line">jla.invokeFinalize(finalizee);</span><br><span class="line"><span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">setJavaLangAccess</span><span class="params">(JavaLangAccess jla)</span> &#123;</span><br><span class="line">    javaLangAccess = jla;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<p><code>SharedSecrets</code> 的 <code>javaLangAccess</code> 通过 <code>setJavaLangAccess</code> 设置</p>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">setJavaLangAccess</span><span class="params">(JavaLangAccess jla)</span> &#123;</span><br><span class="line">    javaLangAccess = jla;</span><br><span class="line">&#125;</span><br><span class="line"><span class="keyword">public</span> <span class="keyword">static</span> JavaLangAccess <span class="title function_">getJavaLangAccess</span><span class="params">()</span> &#123;</span><br><span class="line">    <span class="keyword">return</span> javaLangAccess;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<p><code>setJavaLangAccess</code> 方法在 <code>System</code> 中被调用，<code>javaLangAccess</code> 被设置为一个匿名类实例，其中 <code>invokeFinalize</code> 方法间接调用了传入对象的 <code>finalize</code> 方法。</p>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">private</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">setJavaLangAccess</span><span class="params">()</span> &#123;</span><br><span class="line">    <span class="comment">// Allow privileged classes outside of java.lang</span></span><br><span class="line">    sun.misc.SharedSecrets.setJavaLangAccess(<span class="keyword">new</span> <span class="title class_">sun</span>.misc.JavaLangAccess()&#123;</span><br><span class="line">        <span class="comment">// ...</span></span><br><span class="line">        <span class="keyword">public</span> <span class="keyword">void</span> <span class="title function_">invokeFinalize</span><span class="params">(Object o)</span> <span class="keyword">throws</span> Throwable &#123;</span><br><span class="line">            o.finalize();</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;);</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<p><code>System</code> 的 <code>setJavaLangAccess</code> 方法在 <code>initializeSystemClass</code> 方法中被调用。这里正对应着 <code>FinalizerThread</code> 的 <code>run</code> 方法中等待 <code>VM</code> 初始化完成的处理。</p>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="comment">// 初始化 System class，在线程初始化之后调用</span></span><br><span class="line"><span class="keyword">private</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">initializeSystemClass</span><span class="params">()</span> &#123;</span><br><span class="line">    <span class="comment">// ...</span></span><br><span class="line">    <span class="comment">// register shared secrets</span></span><br><span class="line">    setJavaLangAccess();</span><br><span class="line">    <span class="comment">// 通知 wait 的线程</span></span><br><span class="line">    sun.misc.VM.booted();</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<h3 id="Finalizer-的注册时机"><a href="#Finalizer-的注册时机" class="headerlink" title="Finalizer 的注册时机"></a>Finalizer 的注册时机</h3><p>你是否好奇过 <code>JVM</code> 是如何保证 <code>finalize</code> 方法最多被调用一次的？如果曾经猜测过 <code>JVM</code> 可能在对象中留有标记，那么在我们研究过对象的内部结构之后可以确认其中并没有用于记录对象是否已经 <code>finalized</code> 的地方。同时我们注意到 <code>hasBeenFinalized</code> 方法通过 <code>next</code> 指针是否指向自己表示是否已经 <code>finalized</code>。我们可以合理猜测 <code>register</code> 的调用时机是在对象创建时，因此最多仅有一次被注册。</p>
+<p>通过以下示例可以测试：</p>
+<ul>
+<li>在创建重写了 <code>finalize</code> 方法的类创建对象期间会调用 <code>register</code> 创建并注册 <code>Finalizer</code></li>
+<li>在未重写 <code>finalize</code> 方法的类创建对象期间不会调用<code>register</code></li>
+<li><code>Finalizer</code> 不仅可以保证 <code>finalize</code> 只会被调用一次，甚至不会第二次被添加到 <code>pending-list</code>，因为 <code>runFinalizer</code> 最后调用了 <code>super.clear()</code>，<code>JVM</code> 不会特殊对待复活的对象</li>
+</ul>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">class</span> <span class="title class_">FinalReferenceTest_1</span> &#123;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">static</span> <span class="type">FinalizeObj</span> <span class="variable">save</span> <span class="operator">=</span> <span class="literal">null</span>;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title function_">main</span><span class="params">(String[] args)</span> <span class="keyword">throws</span> InterruptedException &#123;</span><br><span class="line">        System.out.println(<span class="string">&quot;创建 finalize obj，使用 Debug 强制运行到 Finalizer.register&quot;</span>);</span><br><span class="line">        <span class="type">FinalizeObj</span> <span class="variable">finalizeObj</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">FinalizeObj</span>();</span><br><span class="line"></span><br><span class="line">        System.out.println(<span class="string">&quot;gc&quot;</span>);</span><br><span class="line">        finalizeObj = <span class="literal">null</span>;</span><br><span class="line">        System.gc();</span><br><span class="line">        System.out.println(<span class="string">&quot;sleep 1s&quot;</span>);</span><br><span class="line">        TimeUnit.SECONDS.sleep(<span class="number">1</span>);</span><br><span class="line">        save.echo();</span><br><span class="line"></span><br><span class="line">        save = <span class="literal">null</span>;</span><br><span class="line">        System.gc();</span><br><span class="line">        System.out.println(<span class="string">&quot;sleep 1s&quot;</span>);</span><br><span class="line">        TimeUnit.SECONDS.sleep(<span class="number">1</span>);</span><br><span class="line">        System.out.println(save == <span class="literal">null</span>);</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">static</span> <span class="keyword">class</span> <span class="title class_">FinalizeObj</span> &#123;</span><br><span class="line">        FinalizeObj() &#123;</span><br><span class="line">            System.out.println(<span class="string">&quot;SaveSelf created&quot;</span>);</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="meta">@Override</span></span><br><span class="line">        <span class="keyword">protected</span> <span class="keyword">void</span> <span class="title function_">finalize</span><span class="params">()</span> <span class="keyword">throws</span> Throwable &#123;</span><br><span class="line">            System.out.println(<span class="string">&quot;finalized&quot;</span>);</span><br><span class="line">            save = <span class="built_in">this</span>;</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="keyword">public</span> <span class="keyword">void</span> <span class="title function_">echo</span><span class="params">()</span> &#123;</span><br><span class="line">            System.out.println(<span class="string">&quot;I am alive.&quot;</span>);</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+
+
+
+<h2 id="参考文章"><a href="#参考文章" class="headerlink" title="参考文章"></a>参考文章</h2><ul>
+<li><a href="https://stackoverflow.com/questions/21809922/how-is-an-object-marked-as-finalized-in-java-so-that-the-finalize-method-wouldn">How is an object marked as finalized in Java (so that the finalize method wouldn’t be called the second time)?</a></li>
+</ul>
+]]></content>
+      <tags>
+        <tag>java</tag>
       </tags>
   </entry>
   <entry>
@@ -6365,293 +6123,881 @@
 <h3 id="进入编辑模式"><a href="#进入编辑模式" class="headerlink" title="进入编辑模式"></a>进入编辑模式</h3><table>
 <thead>
 <tr>
-<th>快捷键</th>
-<th>功能</th>
+<th>快捷键</th>
+<th>功能</th>
+</tr>
+</thead>
+<tbody><tr>
+<td><code>i</code></td>
+<td>进入插入模式，从光标所在处开始插入</td>
+</tr>
+<tr>
+<td><code>I</code></td>
+<td>进入插入模式，从光标所在行的第一个非空格开始插入</td>
+</tr>
+<tr>
+<td><code>a</code></td>
+<td>进入插入模式，从光标所在的下一个字符处开始插入</td>
+</tr>
+<tr>
+<td><code>A</code></td>
+<td>进入插入模式，从光标所在行的最后一个字符处开始插入</td>
+</tr>
+<tr>
+<td><code>o</code></td>
+<td>进入插入模式，在光标所在行的下一行插入新的一行</td>
+</tr>
+<tr>
+<td><code>O</code></td>
+<td>进入插入模式，在光标所在行的上一行插入新的一行</td>
+</tr>
+<tr>
+<td><code>r</code></td>
+<td>进入替换模式，只会替换光标所在的字符一次</td>
+</tr>
+<tr>
+<td><code>R</code></td>
+<td>进入替换模式，替换光标所在的字符，直到通过Esc退出</td>
+</tr>
+<tr>
+<td><code>Esc</code></td>
+<td>退出编辑模式，回到一般命令模式</td>
+</tr>
+</tbody></table>
+<h3 id="保存和退出"><a href="#保存和退出" class="headerlink" title="保存和退出"></a>保存和退出</h3><table>
+<thead>
+<tr>
+<th>快捷键</th>
+<th>功能</th>
+</tr>
+</thead>
+<tbody><tr>
+<td><code>:w</code></td>
+<td>保存文件</td>
+</tr>
+<tr>
+<td><code>:w!</code></td>
+<td>若文件为只读，强制保存</td>
+</tr>
+<tr>
+<td><code>:q</code></td>
+<td>退出 Vim，如果文件已修改，将退出失败</td>
+</tr>
+<tr>
+<td><code>:q!</code></td>
+<td>强制退出 Vim，不保存文件修改</td>
+</tr>
+<tr>
+<td><code>:wq</code></td>
+<td>保存文件并退出 Vim</td>
+</tr>
+<tr>
+<td><code>:w filename</code></td>
+<td>另存为新文件</td>
+</tr>
+<tr>
+<td><code>ZZ</code></td>
+<td>退出 Vim，若文件无修改，则不保存退出；如果文件已修改，保存并退出</td>
+</tr>
+<tr>
+<td><code>:r filename</code></td>
+<td>读入另一个文件的数据并添加到光标所在行之后</td>
+</tr>
+</tbody></table>
+<h2 id="额外功能"><a href="#额外功能" class="headerlink" title="额外功能"></a>额外功能</h2><h3 id="可视模式"><a href="#可视模式" class="headerlink" title="可视模式"></a>可视模式</h3><table>
+<thead>
+<tr>
+<th>快捷键</th>
+<th>功能</th>
+</tr>
+</thead>
+<tbody><tr>
+<td><code>v</code></td>
+<td>字符选择，将光标经过的地方反白选择</td>
+</tr>
+<tr>
+<td><code>V</code></td>
+<td>行选择，将光标经过的行反白选择</td>
+</tr>
+<tr>
+<td><code>Ctrl + v</code></td>
+<td>区块选择，用矩形的方式反白选择</td>
+</tr>
+<tr>
+<td><code>y</code></td>
+<td>复制反白选择的地方</td>
+</tr>
+<tr>
+<td><code>d</code></td>
+<td>删除反白选择的地方</td>
+</tr>
+<tr>
+<td><code>~</code></td>
+<td>对反白选择的地方切换大小写</td>
+</tr>
+</tbody></table>
+<h3 id="多文件编辑"><a href="#多文件编辑" class="headerlink" title="多文件编辑"></a>多文件编辑</h3><table>
+<thead>
+<tr>
+<th>快捷键</th>
+<th>功能</th>
+</tr>
+</thead>
+<tbody><tr>
+<td><code>:n</code></td>
+<td>编辑下一个文件</td>
+</tr>
+<tr>
+<td><code>:N</code></td>
+<td>编辑上一个文件</td>
+</tr>
+<tr>
+<td><code>:files</code></td>
+<td>列出当前 Vim 打开的所有文件</td>
+</tr>
+</tbody></table>
+<h3 id="多窗口功能"><a href="#多窗口功能" class="headerlink" title="多窗口功能"></a>多窗口功能</h3><table>
+<thead>
+<tr>
+<th>快捷键</th>
+<th>功能</th>
+</tr>
+</thead>
+<tbody><tr>
+<td><code>:sp [filename]</code></td>
+<td>打开一个新窗口</td>
+</tr>
+<tr>
+<td><code>Ctrl + w</code> + <code>j</code> </br> <code>Ctrl + w</code> + <code>↓</code></td>
+<td>光标移动到下方的窗口</td>
+</tr>
+<tr>
+<td><code>Ctrl + w</code> + <code>k</code> </br> <code>Ctrl + w</code> + <code>↑</code></td>
+<td>光标移动到上方的窗口</td>
+</tr>
+<tr>
+<td><code>Ctrl + w</code> + <code>q</code> </br> <code>:q</code> </br> <code>:close</code></td>
+<td>关闭窗口</td>
+</tr>
+</tbody></table>
+<h3 id="关键词自动补全"><a href="#关键词自动补全" class="headerlink" title="关键词自动补全"></a>关键词自动补全</h3><table>
+<thead>
+<tr>
+<th>快捷键</th>
+<th>功能</th>
+</tr>
+</thead>
+<tbody><tr>
+<td><code>Ctrl + x</code> + <code>Ctrl + n</code></td>
+<td>使用当前文件的内容文字作为关键词，予以补齐</td>
+</tr>
+<tr>
+<td><code>Ctrl + x</code> + <code>Ctrl + f</code></td>
+<td>使用当前目录的文件名作为关键词，予以补齐</td>
+</tr>
+<tr>
+<td><code>Ctrl + x</code> + <code>Ctrl + o</code></td>
+<td>使用扩展名作为语法补充，以 Vim 内置的关键词，予以补齐</td>
+</tr>
+</tbody></table>
+<h2 id="环境配置"><a href="#环境配置" class="headerlink" title="环境配置"></a>环境配置</h2><table>
+<thead>
+<tr>
+<th>设置参数</th>
+<th>功能</th>
+</tr>
+</thead>
+<tbody><tr>
+<td><code>:set nu</code> </br> <code>:set nonu</code></td>
+<td>设置和取消行号</td>
+</tr>
+<tr>
+<td><code>:syntax on</code> </br> <code>:syntax off</code></td>
+<td>是否依据程序相关语法显示不同颜色</td>
+</tr>
+</tbody></table>
+<blockquote>
+<p>可以通过 <code>vim ~/.vimrc</code> 修改配置文件。</p>
+</blockquote>
+<h2 id="参考文章"><a href="#参考文章" class="headerlink" title="参考文章"></a>参考文章</h2><ul>
+<li><a href="https://linux.vbird.org/linux_basic/centos7/0310vi.php">vim 程式編輯器</a></li>
+<li><a href="https://linux.cn/article-8144-1.html">Vim 快捷键速查表</a></li>
+<li><a href="https://www.ruanyifeng.com/blog/2018/09/vimrc.html">Vim 配置入门</a></li>
+</ul>
+]]></content>
+      <tags>
+        <tag>linux</tag>
+        <tag>vim</tag>
+      </tags>
+  </entry>
+  <entry>
+    <title>k3s 的安装和使用</title>
+    <url>/2024/01/30/installation-and-use-of-k3s/</url>
+    <content><![CDATA[<p>本文记录了 <code>k3s</code> 的安装和使用，相较于 <code>minikube</code>，前者是一个完全兼容的 <code>Kubernetes</code> 发行版，安装和使用的体验更佳。</p>
+<span id="more"></span>
+
+<h2 id="安装"><a href="#安装" class="headerlink" title="安装"></a>安装</h2><blockquote>
+<p>参考官方文档-<a href="https://docs.k3s.io/zh/quick-start">快速入门指南</a>，使用默认选项启动集群非常简单方便！！！</p>
+</blockquote>
+<h3 id="步骤"><a href="#步骤" class="headerlink" title="步骤"></a>步骤</h3><ol>
+<li>获取并运行 <code>k3s</code> 安装脚本。官方为中国用户提供了镜像加速支持。<figure class="highlight text"><table><tr><td class="code"><pre><span class="line">$ curl -sfL https://rancher-mirror.rancher.cn/k3s/k3s-install.sh | INSTALL_K3S_MIRROR=cn sh -                                </span><br><span class="line">[sudo] password for moralok:                                                                                                                        </span><br><span class="line">[INFO]  Finding release for channel stable                                                                                                        </span><br><span class="line">[INFO]  Using v1.28.5+k3s1 as release                                                                                                             </span><br><span class="line">[INFO]  Downloading hash rancher-mirror.rancher.cn/k3s/v1.28.5-k3s1/sha256sum-amd64.txt                                                           </span><br><span class="line">[INFO]  Downloading binary rancher-mirror.rancher.cn/k3s/v1.28.5-k3s1/k3s                                                                         </span><br><span class="line">[INFO]  Verifying binary download                                                                                                                 </span><br><span class="line">[INFO]  Installing k3s to /usr/local/bin/k3s                                                                                                      </span><br><span class="line">[INFO]  Skipping installation of SELinux RPM                                                                                                      </span><br><span class="line">[INFO]  Creating /usr/local/bin/kubectl symlink to k3s                                                                                            </span><br><span class="line">[INFO]  Creating /usr/local/bin/crictl symlink to k3s                                                                                             </span><br><span class="line">[INFO]  Skipping /usr/local/bin/ctr symlink to k3s, command exists in PATH at /usr/bin/ctr                                                        </span><br><span class="line">[INFO]  Creating killall script /usr/local/bin/k3s-killall.sh                                                                                     </span><br><span class="line">[INFO]  Creating uninstall script /usr/local/bin/k3s-uninstall.sh                                                                                 </span><br><span class="line">[INFO]  env: Creating environment file /etc/systemd/system/k3s.service.env                                                                        </span><br><span class="line">[INFO]  systemd: Creating service file /etc/systemd/system/k3s.service                                                                            </span><br><span class="line">sh: 1014: restorecon: not found                                                                                                                   </span><br><span class="line">sh: 1015: restorecon: not found                                                                                                                   </span><br><span class="line">[INFO]  systemd: Enabling k3s unit                                                                                                                </span><br><span class="line">Created symlink /etc/systemd/system/multi-user.target.wants/k3s.service → /etc/systemd/system/k3s.service.                                        </span><br><span class="line">[INFO]  systemd: Starting k3s</span><br></pre></td></tr></table></figure></li>
+<li>可以通过使用 <code>kubectl</code> 确认安装成功。刚安装的时候使用 <code>kubectl</code> 需要 <code>root</code> 权限。<figure class="highlight text"><table><tr><td class="code"><pre><span class="line">$ sudo kubectl get node</span><br><span class="line">NAME            STATUS   ROLES                  AGE   VERSION</span><br><span class="line">ubuntu-server   Ready    control-plane,master   52m   v1.28.5+k3s1</span><br></pre></td></tr></table></figure></li>
+<li>实际上安装的就是一个 <code>k3s</code> 可执行文件，<code>kubectl</code> 和 <code>crictl</code> 只是软链接，指向 <code>k3s</code>。<figure class="highlight text"><table><tr><td class="code"><pre><span class="line">$ ls /usr/local/bin/</span><br><span class="line">crictl  k3s  k3s-killall.sh  k3s-uninstall.sh  kubectl</span><br></pre></td></tr></table></figure></li>
+</ol>
+<blockquote>
+<p>安装的信息中显示了 <code>k3s</code> 的 <code>service file</code> 和 <code>environment file</code> 的路径，后续修改启动参数和环境变量需要用到。</p>
+</blockquote>
+<h3 id="配置文件权限问题"><a href="#配置文件权限问题" class="headerlink" title="配置文件权限问题"></a>配置文件权限问题</h3><p>在刚安装完 <code>k3s</code> 的时候，使用 <code>kubectl</code> 需要 <code>root</code> 权限。根据报错信息可知，是因为非 <code>root</code> 用户无法读取配置文件 <code>/etc/rancher/k3s/k3s.yaml</code>。</p>
+<figure class="highlight text"><table><tr><td class="code"><pre><span class="line">$ kubectl get node                                                                                                                                            </span><br><span class="line">WARN[0000] Unable to read /etc/rancher/k3s/k3s.yaml, please start server with --write-kubeconfig-mode to modify kube config permissions           </span><br><span class="line">error: error loading config file &quot;/etc/rancher/k3s/k3s.yaml&quot;: open /etc/rancher/k3s/k3s.yaml: permission denied</span><br></pre></td></tr></table></figure>
+
+<p>查看配置文件的信息可知其权限配置为 <code>600</code>，只有 <code>root</code> 用户具有读写权限。</p>
+<figure class="highlight text"><table><tr><td class="code"><pre><span class="line">$ ll /etc/rancher/k3s/k3s.yaml                                                                                               </span><br><span class="line">-rw------- 1 root root 2961 Jan 30 18:58 /etc/rancher/k3s/k3s.yaml</span><br></pre></td></tr></table></figure>
+
+<p>一般来说，我们希望能够通过非 <code>root</code> 用户使用 <code>kubectl</code>，避免通过 <code>root</code> 用户或者通过 <code>sudo</code> 加输入密码的形式来使用 <code>kubectl</code>。那么如何解决这个问题呢？本质上这是一个 <code>Linux</code> 的文件权限问题，似乎修改文件的权限配置就可以解决。但是提示信息给出的解决方案并不是那么直接，它告诉我们通过修改 <code>k3s server</code> 的启动参数来达到修改配置文件权限的目的。这是因为 <code>k3s</code> 服务在每次重启时会根据启动参数和环境变量重置配置文件 <code>/etc/rancher/k3s/k3s.yaml</code>，手动修改文件的权限配置并不能优雅地解决这个问题，一旦服务重启，修改就会丢失。</p>
+<blockquote>
+<p><a href="https://github.com/k3s-io/k3s/discussions/7278">k3s 的 Github Discussions</a> 中讨论了这个问题，并链接了文档 <a href="https://docs.k3s.io/zh/cli/server#%E7%AE%A1%E7%90%86-kubeconfig-%E9%80%89%E9%A1%B9">管理 Kubeconfig 选项</a>，文档介绍了通过修改启动参数和环境变量达到修改配置文件权限的目的。</p>
+</blockquote>
+<h4 id="修改启动参数"><a href="#修改启动参数" class="headerlink" title="修改启动参数"></a>修改启动参数</h4><p>第一种方式是修改启动参数。</p>
+<ol>
+<li><code>sudo vim /etc/systemd/system/k3s.service</code> 添加 <code>k3s</code> 启动参数 <code>--write-kubeconfig-mode 644</code><figure class="highlight ini"><table><tr><td class="code"><pre><span class="line"><span class="attr">ExecStart</span>=/usr/local/bin/k3s \</span><br><span class="line">    server --write-kubeconfig-mode 644 \</span><br></pre></td></tr></table></figure></li>
+<li><code>systemctl daemon-reload</code> 重新加载 <code>systemd</code> 配置</li>
+<li><code>systemctl restart k3s.service</code> 重启服务</li>
+<li>验证修改生效<figure class="highlight text"><table><tr><td class="code"><pre><span class="line">$ ll /etc/rancher/k3s/k3s.yaml</span><br><span class="line">-rw-r--r-- 1 root root 2961 Jan 30 20:13 /etc/rancher/k3s/k3s.yaml</span><br></pre></td></tr></table></figure></li>
+</ol>
+<h4 id="修改环境变量"><a href="#修改环境变量" class="headerlink" title="修改环境变量"></a>修改环境变量</h4><p>第二种方式是修改环境变量。</p>
+<ol>
+<li><code>sudo vim /etc/systemd/system/k3s.service.env</code> 添加环境变量 <code>K3S_KUBECONFIG_MODE=644</code><figure class="highlight ini"><table><tr><td class="code"><pre><span class="line"><span class="attr">K3S_KUBECONFIG_MODE</span>=<span class="number">644</span></span><br></pre></td></tr></table></figure></li>
+<li><code>systemctl restart k3s.service</code> 重启服务</li>
+</ol>
+<h4 id="修改配置文件路径"><a href="#修改配置文件路径" class="headerlink" title="修改配置文件路径"></a>修改配置文件路径</h4><p>第三种方式是复制配置信息到当前用户目录下，并使用其作为配置文件的路径。</p>
+<ol>
+<li>设置环境变量 <code>export KUBECONFIG=~/.kube/config</code></li>
+<li>创建文件夹 <code>mkdir ~/.kube 2&gt; /dev/null</code></li>
+<li>复制配置信息 <code>sudo k3s kubectl config view --raw &gt; &quot;$KUBECONFIG&quot;</code></li>
+<li>修改配置文件的权限 <code>chmod 600 &quot;$KUBECONFIG&quot;</code></li>
+</ol>
+<h3 id="配置代理"><a href="#配置代理" class="headerlink" title="配置代理"></a>配置代理</h3><p>涉及 <code>k8s</code>，难免需要使用代理，否则在拉取镜像时将寸步难行。官方文档 <a href="https://docs.k3s.io/zh/advanced#%E9%85%8D%E7%BD%AE-http-%E4%BB%A3%E7%90%86">配置 HTTP 代理</a> 介绍了如何配置代理。其中提及 <code>k3s</code> 安装脚本会自动使用当前 <code>shell</code> 中的 <code>HTTP_PROXY</code>、<code>HTTPS_PROXY</code> 和 <code>NO_PROXY</code>，以及 <code>CONTAINERD_HTTP_PROXY</code>、<code>CONTAINERD_HTTPS_PROXY</code> 和 <code>CONTAINERD_NO_PROXY</code> 变量（如果存在），并将它们写入 <code>systemd</code> 服务的环境文件。比如我设置过 <code>shell</code> 变量 <code>HTTP_PROXY</code>、<code>HTTPS_PROXY</code> 和 <code>NO_PROXY</code>，<code>/etc/systemd/system/k3s.service.env</code> 如下，你也可以自行编辑修改。</p>
+<figure class="highlight ini"><table><tr><td class="code"><pre><span class="line"><span class="attr">http_proxy</span>=<span class="string">&#x27;http://127.0.0.1:7890&#x27;</span></span><br><span class="line"><span class="attr">https_proxy</span>=<span class="string">&#x27;http://127.0.0.1:7890&#x27;</span></span><br><span class="line"><span class="attr">no_proxy</span>=<span class="string">&#x27;localhost,127.0.0.1&#x27;</span></span><br><span class="line"><span class="attr">K3S_KUBECONFIG_MODE</span>=<span class="number">644</span></span><br></pre></td></tr></table></figure>
+
+<h2 id="使用"><a href="#使用" class="headerlink" title="使用"></a>使用</h2><blockquote>
+<p>k8s 基础教程可参考官方文档 <a href="https://kubernetes.io/zh-cn/docs/tutorials/kubernetes-basics/">Kubernetes 基础</a>。</p>
+</blockquote>
+<h3 id="创建-Deployment"><a href="#创建-Deployment" class="headerlink" title="创建 Deployment"></a>创建 Deployment</h3><ol>
+<li>使用 <code>kubectl create</code> 命令创建管理 <code>Pod</code> 的 <code>Deployment</code>。该 <code>Pod</code> 根据提供的 <code>Docker</code> 镜像运行容器。<figure class="highlight shell"><table><tr><td class="code"><pre><span class="line">kubectl create deployment hello-node --image=registry.k8s.io/e2e-test-images/agnhost:2.39 -- /agnhost netexec --http-port=8080</span><br></pre></td></tr></table></figure></li>
+<li>查看 <code>Deployment</code>：<figure class="highlight text"><table><tr><td class="code"><pre><span class="line">$ kubectl get pods</span><br><span class="line">NAME                         READY   STATUS    RESTARTS   AGE</span><br><span class="line">hello-node-ccf4b9788-d8k9b   1/1     Running   0          15h</span><br></pre></td></tr></table></figure></li>
+<li>查看 <code>Pod</code> 中容器的应用程序日志。<figure class="highlight text"><table><tr><td class="code"><pre><span class="line">$ kubectl logs hello-node-ccf4b9788-d8k9b</span><br><span class="line">I0130 19:26:57.751131       1 log.go:195] Started HTTP server on port 8080</span><br><span class="line">I0130 19:26:57.751350       1 log.go:195] Started UDP server on port  8081</span><br></pre></td></tr></table></figure></li>
+</ol>
+<h3 id="创建-Service"><a href="#创建-Service" class="headerlink" title="创建 Service"></a>创建 Service</h3><ol>
+<li>使用 <code>kubectl expose</code> 命令将 <code>Pod</code> 暴露给公网：<figure class="highlight shell"><table><tr><td class="code"><pre><span class="line">kubectl expose deployment hello-node --type=LoadBalancer --port=8080</span><br></pre></td></tr></table></figure></li>
+<li>查看你创建的 <code>Service</code>：<figure class="highlight text"><table><tr><td class="code"><pre><span class="line">$ kubectl get services</span><br><span class="line">NAME         TYPE           CLUSTER-IP     EXTERNAL-IP      PORT(S)          AGE</span><br><span class="line">kubernetes   ClusterIP      10.43.0.1      &lt;none&gt;           443/TCP          15h</span><br><span class="line">hello-node   LoadBalancer   10.43.37.170   192.168.46.128   8080:32117/TCP   15h</span><br></pre></td></tr></table></figure></li>
+<li>使用 <code>curl</code> 发起请求：<figure class="highlight text"><table><tr><td class="code"><pre><span class="line">$ curl http://localhost:8080</span><br><span class="line">NOW: 2024-01-31 10:55:14.228709273 +0000 UTC m=+25932.159732511</span><br></pre></td></tr></table></figure></li>
+<li>再次查看 <code>Pod</code> 中容器的应用程序日志。<figure class="highlight text"><table><tr><td class="code"><pre><span class="line">$ kubectl logs hello-node-ccf4b9788-d8k9b</span><br><span class="line">I0130 19:26:57.751131       1 log.go:195] Started HTTP server on port 8080</span><br><span class="line">I0130 19:26:57.751350       1 log.go:195] Started UDP server on port  8081</span><br><span class="line">I0130 19:32:21.074992       1 log.go:195] GET /</span><br></pre></td></tr></table></figure></li>
+</ol>
+<h3 id="清理"><a href="#清理" class="headerlink" title="清理"></a>清理</h3><ol>
+<li>删除 <code>Service</code>：<figure class="highlight shell"><table><tr><td class="code"><pre><span class="line">kubectl delete service hello-node</span><br></pre></td></tr></table></figure></li>
+<li>删除 <code>Deployment</code>：<figure class="highlight shell"><table><tr><td class="code"><pre><span class="line">kubectl delete deployment hello-node</span><br></pre></td></tr></table></figure></li>
+</ol>
+<h2 id="卸载"><a href="#卸载" class="headerlink" title="卸载"></a>卸载</h2><ol>
+<li>从 server 节点卸载 k3s<figure class="highlight plaintext"><table><tr><td class="code"><pre><span class="line">/usr/local/bin/k3s-uninstall.sh</span><br></pre></td></tr></table></figure></li>
+</ol>
+<h2 id="参考文章"><a href="#参考文章" class="headerlink" title="参考文章"></a>参考文章</h2><ul>
+<li><a href="https://docs.k3s.io/zh/quick-start">快速入门指南</a></li>
+<li><a href="https://docs.k3s.io/zh/cli/server#%E7%AE%A1%E7%90%86-kubeconfig-%E9%80%89%E9%A1%B9">管理 Kubeconfig 选项</a></li>
+<li><a href="https://docs.k3s.io/zh/advanced#%E9%85%8D%E7%BD%AE-http-%E4%BB%A3%E7%90%86">配置 HTTP 代理</a></li>
+<li><a href="https://kubernetes.io/zh-cn/docs/tutorials/hello-minikube/">你好，Minikube</a></li>
+<li><a href="https://github.com/k3s-io/k3s/issues/7272">Permission denied on non-existing &#x2F;etc&#x2F;rancher&#x2F;k3s&#x2F;config.yaml after fresh install</a></li>
+<li><a href="https://devops.stackexchange.com/questions/16043/error-error-loading-config-file-etc-rancher-k3s-k3s-yaml-open-etc-rancher">error: error loading config file “&#x2F;etc&#x2F;rancher&#x2F;k3s&#x2F;k3s.yaml”: open &#x2F;etc&#x2F;rancher&#x2F;k3s&#x2F;k3s.yaml: permission denied</a></li>
+<li><a href="https://github.com/k3s-io/k3s/issues/389">&#x2F;etc&#x2F;rancher&#x2F;k3s&#x2F;k3s.yaml is world readable #389</a></li>
+</ul>
+]]></content>
+      <tags>
+        <tag>k8s</tag>
+        <tag>k3s</tag>
+      </tags>
+  </entry>
+  <entry>
+    <title>信息的表示和处理</title>
+    <url>/2024/03/11/representating-and-manipulating-information/</url>
+    <content><![CDATA[<p>(0 &amp; 1) + interpretation = everything.</p>
+<span id="more"></span>
+
+<p>现代计算机存储和处理的信息以<strong>二值信号</strong>表示。二值信号能够<strong>很容易地被表示、存储和传输</strong>。当把位（bit）组合在一起，再加上某种解释（interpretation），即赋予不同的可能位模式以含义，我们就<strong>能够表示任何有限集合的元素</strong>。</p>
+<blockquote>
+<p>“很容易地被表示、存储和传输” =&gt; 高低电压。</p>
+</blockquote>
+<p>通过研究数字的实际表示，我们能够了解<strong>可以表示的值的范围</strong>和<strong>不同算术运算的属性</strong>。为了使编写的程序能在全部数值范围内正确工作，而且具有跨越不同机器、操作系统和编译器组合的可移植性，了解这种属性是非常重要的。大量计算机的安全漏洞都是由于计算机算术运算的微妙细节引发的。在早期，当人们碰巧触发了程序漏洞，只会给人们带来一些不便，但是现在，有众多的黑客企图利用他们能找到的任何漏洞，不经过授权就进入他人的系统。这就要求<strong>程序员有更多的责任和义务，去了解他们的程序如何工作，以及如何被迫产生不良的行为</strong>。</p>
+<blockquote>
+<p>研究的目的。<br>不仅仅需要正向地去了解如何让程序正确地工作，也要反向地去了解如何迫使程序产生不良的行为，这可以更好地帮助理解底层的工作原理。</p>
+</blockquote>
+<p>从编码的基本定义开始，然后得出一些属性，例如可表示的数字的范围、它们的位级表示以及算术运算的属性。<strong>从这样一个抽象的观点来分析是很重要的</strong>，因为程序员需要对计算机运算与更为人熟悉的整数和实数运算之间的关系有清晰的理解。</p>
+<blockquote>
+<p>不仅仅需要了解当前的设计是怎么样的，还要了解为什么这样设计，分开看待具体和抽象。</p>
+</blockquote>
+<h2 id="信息存储"><a href="#信息存储" class="headerlink" title="信息存储"></a>信息存储</h2><p>大多数计算机使用8位的块，或者称为<strong>字节（byte），作为最小的可寻址的内存单位</strong>，而不是访问内存中单独的位。机器级程序将内存视为一个非常大的字节数组，称为<strong>虚拟内存</strong>（virtual memory）。内存的每个字节都由一个唯一的数字来标识，称为它的<strong>地址</strong>（address），所有可能地址的集合就称为<strong>虚拟地址空间</strong>（virtual address space）。</p>
+<p>编译器和运行时系统将存储器空间划分为更可管理的单元，来存放不同的<strong>程序对象</strong>（program object），即程序数据、指令和控制信息。每个程序对象可以简单地视为一个字节块，而程序本身就是一个字节序列。</p>
+<blockquote>
+<p>也许是因为无处不在的局部性原理，在计算机中，很多时候“最小”指向的是一个“连续的块”而非“不可分割的点”。<br>“非常大的字节数组” =&gt; 非常重要的一种视角。</p>
+</blockquote>
+<h3 id="十六进制表示法"><a href="#十六进制表示法" class="headerlink" title="十六进制表示法"></a>十六进制表示法</h3><p>一个字节由8位组成。二进制表示法太冗长，而十进制表示法与位模式的互相转化很麻烦，替代的方法是，以16为基数，或者叫做<strong>十六进制</strong>（hexadecimal，简写为 hex）数，来表示位模式。</p>
+<table>
+<thead>
+<tr>
+<th>十进制</th>
+<th>0</th>
+<th>1</th>
+<th>2</th>
+<th>3</th>
+<th>4</th>
+<th>5</th>
+<th>6</th>
+<th>7</th>
+<th>8</th>
+<th>9</th>
+<th>10</th>
+<th>11</th>
+<th>12</th>
+<th>13</th>
+<th>14</th>
+<th>15</th>
 </tr>
 </thead>
 <tbody><tr>
-<td><code>i</code></td>
-<td>进入插入模式，从光标所在处开始插入</td>
-</tr>
-<tr>
-<td><code>I</code></td>
-<td>进入插入模式，从光标所在行的第一个非空格开始插入</td>
-</tr>
-<tr>
-<td><code>a</code></td>
-<td>进入插入模式，从光标所在的下一个字符处开始插入</td>
-</tr>
-<tr>
-<td><code>A</code></td>
-<td>进入插入模式，从光标所在行的最后一个字符处开始插入</td>
-</tr>
-<tr>
-<td><code>o</code></td>
-<td>进入插入模式，在光标所在行的下一行插入新的一行</td>
-</tr>
-<tr>
-<td><code>O</code></td>
-<td>进入插入模式，在光标所在行的上一行插入新的一行</td>
-</tr>
-<tr>
-<td><code>r</code></td>
-<td>进入替换模式，只会替换光标所在的字符一次</td>
-</tr>
-<tr>
-<td><code>R</code></td>
-<td>进入替换模式，替换光标所在的字符，直到通过Esc退出</td>
-</tr>
-<tr>
-<td><code>Esc</code></td>
-<td>退出编辑模式，回到一般命令模式</td>
+<td>十六进制</td>
+<td>0</td>
+<td>1</td>
+<td>2</td>
+<td>3</td>
+<td>4</td>
+<td>5</td>
+<td>6</td>
+<td>7</td>
+<td>8</td>
+<td>9</td>
+<td>A</td>
+<td>B</td>
+<td>C</td>
+<td>D</td>
+<td>E</td>
+<td>F</td>
+</tr>
+<tr>
+<td>二进制</td>
+<td>0000</td>
+<td>0001</td>
+<td>0010</td>
+<td>0011</td>
+<td>0100</td>
+<td>0101</td>
+<td>0110</td>
+<td>0111</td>
+<td>1000</td>
+<td>1001</td>
+<td>1010</td>
+<td>1011</td>
+<td>1100</td>
+<td>1101</td>
+<td>1110</td>
+<td>1111</td>
 </tr>
 </tbody></table>
-<h3 id="保存和退出"><a href="#保存和退出" class="headerlink" title="保存和退出"></a>保存和退出</h3><table>
+<blockquote>
+<p>十六进制 =&gt; 优秀的替代品。</p>
+</blockquote>
+<h3 id="字数据大小"><a href="#字数据大小" class="headerlink" title="字数据大小"></a>字数据大小</h3><p>每台计算机都有一个<strong>字长</strong>（word size），指明指针数据的标称大小（nominal size）。因为虚拟地址是以这样的一个字来编码的，所以<strong>字长决定的最重要的系统参数就是虚拟地址空间的最大大小</strong>。对于一个字长为w位的机器而言，虚拟地址的范围为0~2^w-1，程序最多访问2^w个字节。32位字长限制虚拟地址空间为4GB，64位字长限制虚拟地址空间为16EB。<br>大多数64位机器也可以运行为32位机器编译的程序，这是一种向后兼容。“32位机器”和“64位机器”区别在于该程序是如何编译的，而不是其运行的机器类型。</p>
+<blockquote>
+<p>字长和虚拟地址空间的最大大小不能完全一概而论。字长是指处理器一次能够处理的二进制数据位数，通常<strong>地址总线</strong>的位数与之保持一致，以保证一次性读取完整的数据并充分发挥寻址能力。但是现代计算机可能采用不同的位数以实现更高的性能和灵活性。</p>
+</blockquote>
+<p>基本C语言数据类型的典型大小（以字节为单位），分配的字节数受程序是如何编译的影响而变化。</p>
+<blockquote>
+<p>字长也会影响数据类型的典型大小。数据总线的位数通常也与字长保持一致，即使读取char类型的数据，CPU也是一次性读取64位的数据再提取8位（这时候小端法似乎更自然）。</p>
+</blockquote>
+<table>
 <thead>
 <tr>
-<th>快捷键</th>
-<th>功能</th>
+<th>有符号</th>
+<th>无符号</th>
+<th>32位</th>
+<th>64位</th>
 </tr>
 </thead>
 <tbody><tr>
-<td><code>:w</code></td>
-<td>保存文件</td>
+<td>[signed] char</td>
+<td>unsigned char</td>
+<td>1</td>
+<td>1</td>
 </tr>
 <tr>
-<td><code>:w!</code></td>
-<td>若文件为只读，强制保存</td>
+<td>short</td>
+<td>unsigned short</td>
+<td>2</td>
+<td>2</td>
 </tr>
 <tr>
-<td><code>:q</code></td>
-<td>退出 Vim，如果文件已修改，将退出失败</td>
+<td>int</td>
+<td>unsigned int</td>
+<td>4</td>
+<td>4</td>
 </tr>
 <tr>
-<td><code>:q!</code></td>
-<td>强制退出 Vim，不保存文件修改</td>
+<td>long</td>
+<td>unsigned long</td>
+<td>4</td>
+<td>8</td>
 </tr>
 <tr>
-<td><code>:wq</code></td>
-<td>保存文件并退出 Vim</td>
+<td>int32_t</td>
+<td>uint32_t</td>
+<td>4</td>
+<td>4</td>
 </tr>
 <tr>
-<td><code>:w filename</code></td>
-<td>另存为新文件</td>
+<td>int64_t</td>
+<td>uint64_t</td>
+<td>8</td>
+<td>8</td>
 </tr>
 <tr>
-<td><code>ZZ</code></td>
-<td>退出 Vim，若文件无修改，则不保存退出；如果文件已修改，保存并退出</td>
+<td>char *</td>
+<td></td>
+<td>4</td>
+<td>8</td>
 </tr>
 <tr>
-<td><code>:r filename</code></td>
-<td>读入另一个文件的数据并添加到光标所在行之后</td>
+<td>float</td>
+<td></td>
+<td>4</td>
+<td>4</td>
+</tr>
+<tr>
+<td>double</td>
+<td></td>
+<td>8</td>
+<td>8</td>
 </tr>
 </tbody></table>
-<h2 id="额外功能"><a href="#额外功能" class="headerlink" title="额外功能"></a>额外功能</h2><h3 id="可视模式"><a href="#可视模式" class="headerlink" title="可视模式"></a>可视模式</h3><table>
+<p><strong>程序员应该力图使他们的程序在不同的机器和编译器上可移植</strong>。可移植性的一个方面就是使程序对不同数据类型的确切大小不敏感。</p>
+<blockquote>
+<p>字长、地址总线、数据总线 =&gt; 处理器一次能够处理的二进制位数、虚拟地址空间的最大大小、数据的最大大小。</p>
+</blockquote>
+<h3 id="寻址和字节顺序"><a href="#寻址和字节顺序" class="headerlink" title="寻址和字节顺序"></a>寻址和字节顺序</h3><p>对于<strong>跨越多字节的程序对象</strong>，我们必须建立两个规则：<strong>这个对象的地址是什么，以及在内存中如何排列这些字节</strong>。</p>
+<ul>
+<li>在几乎所有的机器上，多字节对象都被存储为连续的字节序列，对象的地址为所使用的字节中最小的地址。</li>
+<li>排列表示一个对象的字节有两个通用的规则。最低有效字节在最前面的方式，称为<strong>小端法</strong>（little endian）；最高有效字节在最前面的方式，称为<strong>大端法</strong>（big endian）。大多数 Intel 兼容机都只用小端模式；IBM 和 Oracle 的大多数机器按大端模式操作，个人计算机使用小端法；许多比较新的微处理器使用双端法（bi-endian），比如移动电话上的 ARM 微处理器，但是最常见的 Android 和 iOS 只能运行于小端模式。</li>
+</ul>
+<p><strong>选择何种字节顺序没有技术上的理由</strong>。只要选择了一种规则并且始终如一地坚持，对于哪种字节排序的选择都是任意的。</p>
+<blockquote>
+<p>和《格列佛游记》中的情节类似，争论仍然存在。</p>
+</blockquote>
+<p>对于大多数应用程序员来说，其机器所使用的字节顺序是完全不可见（透明）的。<strong>不过有时候，字节顺序会成为问题</strong>。</p>
+<ol>
+<li>在不同类型的机器之间通过网络传送二进制数据时，网络应用程序的代码编写必须遵守已建立的关于字节顺序的规则。</li>
+<li>当检查机器级程序，阅读表示整数数据的字节序列时字节顺序也很重要。</li>
+<li>当编写规避正常的类型系统的程序时，比如使用强制类型转换来访问和打印不同程序对象的字节表示。</li>
+</ol>
+<h3 id="表示字符串"><a href="#表示字符串" class="headerlink" title="表示字符串"></a>表示字符串</h3><p>C语言中字符串被编码为一个以null（其值为 0）字符结尾的字符数组。每个字符都由某个标准编码来表示，最常见的是 ASCII 字符码。字符串在使用 ASCII 码作为字符码的任何系统上都将得到相同的结果，与字节顺序和字大小规则无关。因而，<strong>文本数据比二进制数据具有更强的平台独立性</strong>。</p>
+<p>可以通过执行命令 <code>man ascii</code> 来得到一张 ASCII 字符码的表。</p>
+<p>文字编码的 <strong>Unicode 标准</strong>：<br>ASCII 字符集适合于编码英语文档，但是在表达一些特殊字符方面并没有太多办法，它完全不适合编码希腊语、俄语和中文等语言的文档。基本编码，称为 Unicode 的“统一字符集”，使用32位来表示字符，每个字符要占用4个字节。不过有一些替代编码，常见的字符只需要1个或2个字节，而不太常用的字符需要多一些的字节数。特别地，UTF-8 表示将每个字符编码为一个字节序列，兼容标准 ASCII。</p>
+<blockquote>
+<p>数字和符号，一一对应。</p>
+</blockquote>
+<h3 id="表示代码"><a href="#表示代码" class="headerlink" title="表示代码"></a>表示代码</h3><p>不同的机器类型使用不同的且不兼容的指令和编码方式。即使是完全一样的进程，运行在不同的操作系统上也会有不同的编码规则，因此二进制代码是不兼容的。二进制代码很少能在不同机器和操作系统组合之间移植。</p>
+<p>计算机系统的一个基本概念就是，<strong>从机器的角度来看，程序仅仅只是字节序列</strong>。机器没有关于原始源程序的任何信息，除了可能有些用来帮助调试的辅助表以外。</p>
+<h3 id="布尔代数简介"><a href="#布尔代数简介" class="headerlink" title="布尔代数简介"></a>布尔代数简介</h3><p>二进制值是计算机编码、存储和操作信息的核心，所以围绕数值 0 和 1 的研究已经演化出了丰富的数学知识体系，称为布尔代数（Boolean algebra）。</p>
+<p>最简单的布尔代数是在二元集合 <code>{0, 1}</code> 基础上的定义。二进制值 1 和 0 表示逻辑值 TRUE 或者 FALSE，而运算符<code>~</code>、<code>&amp;</code>、<code>|</code>和<code>^</code>分别表示逻辑运算 NOT、AND、OR 和 EXCLUSIVE-OR。</p>
+<p>布尔运算可以扩展到位向量的运算。</p>
+<p>布尔运算<code>&amp;</code>对<code>|</code>具有分配律；<code>|</code>对<code>&amp;</code>具有分配律。<br>布尔环：<code>a^a=0</code>，<code>(a^b)^a=b</code>。</p>
+<p><strong>位向量一个很有用的应用就是表示有限集合</strong>。</p>
+<h3 id="C语言中的布尔运算"><a href="#C语言中的布尔运算" class="headerlink" title="C语言中的布尔运算"></a>C语言中的布尔运算</h3><p>C语言的一个很有用的特性就是它支持按位布尔运算。<br>确定一个位级表达式的结果最好的方法，就是将十六进制的参数扩展成二进制表示并执行二进制运算，然后再转换回十六进制。</p>
+<h3 id="C语言中的移位运算"><a href="#C语言中的移位运算" class="headerlink" title="C语言中的移位运算"></a>C语言中的移位运算</h3><p>C语言还提供了一组移位运算，向左（<code>&lt;&lt;</code>）或者向右（<code>&gt;&gt;</code>）移动位模式。移位量应该是一个0~w-1之间的值。移位运算是从左至右可结合的。<br>右移运算 <code>x&gt;&gt;k</code> 的行为有点微妙。一般而言，机器支持两种形式的右移：逻辑右移和算术右移。逻辑右移在左端补k个0，算术右移是在左端补k个最高有效位的值。这种做法看上去可能有点奇特，但是它<strong>对有符号整数数据的运算非常有用</strong>。</p>
+<p>C语言标准并没有明确定义对于有符号数应该使用哪种类型的位移，这意味着可能会遇到可移植性问题。实际上，几乎所有的编译器/机器都对有符号数使用算术位移，对于无符号数使用逻辑右移。<br>与C相比，Java对于如何右移有明确的定义。<code>&gt;&gt;</code> 表示算术右移，<code>&gt;&gt;&gt;</code> 表示逻辑右移。</p>
+<p>对于一个由w位组成的数据类型，C语言标准很小心地规避了说明当移动k≥w位时应该如何做。在许多机器上，实际上位移量是通过<code>k mod w</code>得到的。</p>
+<p><strong>加减法的优先级比位移运算高</strong>。</p>
+<blockquote>
+<p>应该通过使用括号避免容易引起困扰的代码。</p>
+</blockquote>
+<h2 id="整数表示"><a href="#整数表示" class="headerlink" title="整数表示"></a>整数表示</h2><h3 id="整型数据类型"><a href="#整型数据类型" class="headerlink" title="整型数据类型"></a>整型数据类型</h3><p>C语言支持多种整型数据类型——表示有限范围的整数。</p>
+<table>
 <thead>
 <tr>
-<th>快捷键</th>
-<th>功能</th>
+<th>C数据类型</th>
+<th>32位</th>
+<th>64位</th>
 </tr>
 </thead>
 <tbody><tr>
-<td><code>v</code></td>
-<td>字符选择，将光标经过的地方反白选择</td>
-</tr>
-<tr>
-<td><code>V</code></td>
-<td>行选择，将光标经过的行反白选择</td>
+<td>[signed] char</td>
+<td>-128~127</td>
+<td></td>
 </tr>
 <tr>
-<td><code>Ctrl + v</code></td>
-<td>区块选择，用矩形的方式反白选择</td>
+<td>unsigned char</td>
+<td>0~255</td>
+<td></td>
 </tr>
 <tr>
-<td><code>y</code></td>
-<td>复制反白选择的地方</td>
+<td>short</td>
+<td>-32 768~32 767</td>
+<td></td>
 </tr>
 <tr>
-<td><code>d</code></td>
-<td>删除反白选择的地方</td>
+<td>unsigned short</td>
+<td>0~65 535</td>
+<td></td>
 </tr>
 <tr>
-<td><code>~</code></td>
-<td>对反白选择的地方切换大小写</td>
+<td>int</td>
+<td>-2 147 483 648~2 147 483 647</td>
+<td></td>
 </tr>
-</tbody></table>
-<h3 id="多文件编辑"><a href="#多文件编辑" class="headerlink" title="多文件编辑"></a>多文件编辑</h3><table>
-<thead>
 <tr>
-<th>快捷键</th>
-<th>功能</th>
-</tr>
-</thead>
-<tbody><tr>
-<td><code>:n</code></td>
-<td>编辑下一个文件</td>
+<td>unsigned int</td>
+<td>0~4 294 967 295</td>
+<td></td>
 </tr>
 <tr>
-<td><code>:N</code></td>
-<td>编辑上一个文件</td>
+<td>long</td>
+<td>-2 147 483 648~2 147 483 647</td>
+<td>-9 223 372 036 854 775 808~9 223 372 036 854 775 807</td>
 </tr>
 <tr>
-<td><code>:files</code></td>
-<td>列出当前 Vim 打开的所有文件</td>
+<td>unsigned long</td>
+<td>0~4 294 967 295</td>
+<td>0~18 446 744 073 709 551 615</td>
 </tr>
-</tbody></table>
-<h3 id="多窗口功能"><a href="#多窗口功能" class="headerlink" title="多窗口功能"></a>多窗口功能</h3><table>
-<thead>
 <tr>
-<th>快捷键</th>
-<th>功能</th>
-</tr>
-</thead>
-<tbody><tr>
-<td><code>:sp [filename]</code></td>
-<td>打开一个新窗口</td>
+<td>int32_t</td>
+<td>-2 147 483 648~2 147 483 647</td>
+<td></td>
 </tr>
 <tr>
-<td><code>Ctrl + w</code> + <code>j</code> </br> <code>Ctrl + w</code> + <code>↓</code></td>
-<td>光标移动到下方的窗口</td>
+<td>uint32_t</td>
+<td>0~4 294 967 295</td>
+<td></td>
 </tr>
 <tr>
-<td><code>Ctrl + w</code> + <code>k</code> </br> <code>Ctrl + w</code> + <code>↑</code></td>
-<td>光标移动到上方的窗口</td>
+<td>int64_t</td>
+<td>-9 223 372 036 854 775 808~9 223 372 036 854 775 807</td>
+<td></td>
 </tr>
 <tr>
-<td><code>Ctrl + w</code> + <code>q</code> </br> <code>:q</code> </br> <code>:close</code></td>
-<td>关闭窗口</td>
+<td>uint64_t</td>
+<td>0~18 446 744 073 709 551 615</td>
+<td></td>
 </tr>
 </tbody></table>
-<h3 id="关键词自动补全"><a href="#关键词自动补全" class="headerlink" title="关键词自动补全"></a>关键词自动补全</h3><table>
+<p>取值范围并不对称，负数的范围比正数的范围大1。<br>C语言标准定义了每种数据类型必须<strong>能够表示的最小的取值范围</strong>，且char、short、int、long等类型的正数和负数的取值范围是对称的。</p>
+<blockquote>
+<p>将标准和具体实现以及字长分开看待（32位机器也可以支持64位表示的整数数据类型）。</p>
+</blockquote>
+<h3 id="无符号数的编码"><a href="#无符号数的编码" class="headerlink" title="无符号数的编码"></a>无符号数的编码</h3><p>假设有一个整数数据类型有 w 位。将位向量写成 <mjx-container class="MathJax" jax="SVG"><svg style="vertical-align: -0.025ex;" xmlns="http://www.w3.org/2000/svg" width="1.294ex" height="1.937ex" role="img" focusable="false" viewBox="0 -845 572 856"><g stroke="currentColor" fill="currentColor" stroke-width="0" transform="scale(1,-1)"><g data-mml-node="math"><g data-mml-node="TeXAtom" data-mjx-texclass="ORD"><g data-mml-node="mover"><g data-mml-node="mi"><path data-c="1D465" d="M52 289Q59 331 106 386T222 442Q257 442 286 424T329 379Q371 442 430 442Q467 442 494 420T522 361Q522 332 508 314T481 292T458 288Q439 288 427 299T415 328Q415 374 465 391Q454 404 425 404Q412 404 406 402Q368 386 350 336Q290 115 290 78Q290 50 306 38T341 26Q378 26 414 59T463 140Q466 150 469 151T485 153H489Q504 153 504 145Q504 144 502 134Q486 77 440 33T333 -11Q263 -11 227 52Q186 -10 133 -10H127Q78 -10 57 16T35 71Q35 103 54 123T99 143Q142 143 142 101Q142 81 130 66T107 46T94 41L91 40Q91 39 97 36T113 29T132 26Q168 26 194 71Q203 87 217 139T245 247T261 313Q266 340 266 352Q266 380 251 392T217 404Q177 404 142 372T93 290Q91 281 88 280T72 278H58Q52 284 52 289Z"></path></g><g data-mml-node="mo" transform="translate(313.8,31) translate(-250 0)"><path data-c="20D7" d="M377 694Q377 702 382 708T397 714Q404 714 409 709Q414 705 419 690Q429 653 460 633Q471 626 471 615Q471 606 468 603T454 594Q411 572 379 531Q377 529 374 525T369 519T364 517T357 516Q350 516 344 521T337 536Q337 555 384 595H213L42 596Q29 605 29 615Q29 622 42 635H401Q377 673 377 694Z"></path></g></g></g></g></g></svg></mjx-container>，或者写成 <mjx-container class="MathJax" jax="SVG"><svg style="vertical-align: -0.566ex;" xmlns="http://www.w3.org/2000/svg" width="18.93ex" height="2.262ex" role="img" focusable="false" viewBox="0 -750 8367.2 1000"><g stroke="currentColor" fill="currentColor" stroke-width="0" transform="scale(1,-1)"><g data-mml-node="math"><g data-mml-node="mrow"><g data-mml-node="mo"><path data-c="5B" d="M118 -250V750H255V710H158V-210H255V-250H118Z"></path></g><g data-mml-node="msub" transform="translate(278,0)"><g data-mml-node="mi"><path data-c="1D465" d="M52 289Q59 331 106 386T222 442Q257 442 286 424T329 379Q371 442 430 442Q467 442 494 420T522 361Q522 332 508 314T481 292T458 288Q439 288 427 299T415 328Q415 374 465 391Q454 404 425 404Q412 404 406 402Q368 386 350 336Q290 115 290 78Q290 50 306 38T341 26Q378 26 414 59T463 140Q466 150 469 151T485 153H489Q504 153 504 145Q504 144 502 134Q486 77 440 33T333 -11Q263 -11 227 52Q186 -10 133 -10H127Q78 -10 57 16T35 71Q35 103 54 123T99 143Q142 143 142 101Q142 81 130 66T107 46T94 41L91 40Q91 39 97 36T113 29T132 26Q168 26 194 71Q203 87 217 139T245 247T261 313Q266 340 266 352Q266 380 251 392T217 404Q177 404 142 372T93 290Q91 281 88 280T72 278H58Q52 284 52 289Z"></path></g><g data-mml-node="TeXAtom" transform="translate(605,-150) scale(0.707)" data-mjx-texclass="ORD"><g data-mml-node="mi"><path data-c="1D464" d="M580 385Q580 406 599 424T641 443Q659 443 674 425T690 368Q690 339 671 253Q656 197 644 161T609 80T554 12T482 -11Q438 -11 404 5T355 48Q354 47 352 44Q311 -11 252 -11Q226 -11 202 -5T155 14T118 53T104 116Q104 170 138 262T173 379Q173 380 173 381Q173 390 173 393T169 400T158 404H154Q131 404 112 385T82 344T65 302T57 280Q55 278 41 278H27Q21 284 21 287Q21 293 29 315T52 366T96 418T161 441Q204 441 227 416T250 358Q250 340 217 250T184 111Q184 65 205 46T258 26Q301 26 334 87L339 96V119Q339 122 339 128T340 136T341 143T342 152T345 165T348 182T354 206T362 238T373 281Q402 395 406 404Q419 431 449 431Q468 431 475 421T483 402Q483 389 454 274T422 142Q420 131 420 107V100Q420 85 423 71T442 42T487 26Q558 26 600 148Q609 171 620 213T632 273Q632 306 619 325T593 357T580 385Z"></path></g><g data-mml-node="mo" transform="translate(716,0)"><path data-c="2212" d="M84 237T84 250T98 270H679Q694 262 694 250T679 230H98Q84 237 84 250Z"></path></g><g data-mml-node="mn" transform="translate(1494,0)"><path data-c="31" d="M213 578L200 573Q186 568 160 563T102 556H83V602H102Q149 604 189 617T245 641T273 663Q275 666 285 666Q294 666 302 660V361L303 61Q310 54 315 52T339 48T401 46H427V0H416Q395 3 257 3Q121 3 100 0H88V46H114Q136 46 152 46T177 47T193 50T201 52T207 57T213 61V578Z"></path></g></g></g><g data-mml-node="mo" transform="translate(2343,0)"><path data-c="2C" d="M78 35T78 60T94 103T137 121Q165 121 187 96T210 8Q210 -27 201 -60T180 -117T154 -158T130 -185T117 -194Q113 -194 104 -185T95 -172Q95 -168 106 -156T131 -126T157 -76T173 -3V9L172 8Q170 7 167 6T161 3T152 1T140 0Q113 0 96 17Z"></path></g><g data-mml-node="msub" transform="translate(2787.6,0)"><g data-mml-node="mi"><path data-c="1D465" d="M52 289Q59 331 106 386T222 442Q257 442 286 424T329 379Q371 442 430 442Q467 442 494 420T522 361Q522 332 508 314T481 292T458 288Q439 288 427 299T415 328Q415 374 465 391Q454 404 425 404Q412 404 406 402Q368 386 350 336Q290 115 290 78Q290 50 306 38T341 26Q378 26 414 59T463 140Q466 150 469 151T485 153H489Q504 153 504 145Q504 144 502 134Q486 77 440 33T333 -11Q263 -11 227 52Q186 -10 133 -10H127Q78 -10 57 16T35 71Q35 103 54 123T99 143Q142 143 142 101Q142 81 130 66T107 46T94 41L91 40Q91 39 97 36T113 29T132 26Q168 26 194 71Q203 87 217 139T245 247T261 313Q266 340 266 352Q266 380 251 392T217 404Q177 404 142 372T93 290Q91 281 88 280T72 278H58Q52 284 52 289Z"></path></g><g data-mml-node="TeXAtom" transform="translate(605,-150) scale(0.707)" data-mjx-texclass="ORD"><g data-mml-node="mi"><path data-c="1D464" d="M580 385Q580 406 599 424T641 443Q659 443 674 425T690 368Q690 339 671 253Q656 197 644 161T609 80T554 12T482 -11Q438 -11 404 5T355 48Q354 47 352 44Q311 -11 252 -11Q226 -11 202 -5T155 14T118 53T104 116Q104 170 138 262T173 379Q173 380 173 381Q173 390 173 393T169 400T158 404H154Q131 404 112 385T82 344T65 302T57 280Q55 278 41 278H27Q21 284 21 287Q21 293 29 315T52 366T96 418T161 441Q204 441 227 416T250 358Q250 340 217 250T184 111Q184 65 205 46T258 26Q301 26 334 87L339 96V119Q339 122 339 128T340 136T341 143T342 152T345 165T348 182T354 206T362 238T373 281Q402 395 406 404Q419 431 449 431Q468 431 475 421T483 402Q483 389 454 274T422 142Q420 131 420 107V100Q420 85 423 71T442 42T487 26Q558 26 600 148Q609 171 620 213T632 273Q632 306 619 325T593 357T580 385Z"></path></g><g data-mml-node="mo" transform="translate(716,0)"><path data-c="2212" d="M84 237T84 250T98 270H679Q694 262 694 250T679 230H98Q84 237 84 250Z"></path></g><g data-mml-node="mn" transform="translate(1494,0)"><path data-c="32" d="M109 429Q82 429 66 447T50 491Q50 562 103 614T235 666Q326 666 387 610T449 465Q449 422 429 383T381 315T301 241Q265 210 201 149L142 93L218 92Q375 92 385 97Q392 99 409 186V189H449V186Q448 183 436 95T421 3V0H50V19V31Q50 38 56 46T86 81Q115 113 136 137Q145 147 170 174T204 211T233 244T261 278T284 308T305 340T320 369T333 401T340 431T343 464Q343 527 309 573T212 619Q179 619 154 602T119 569T109 550Q109 549 114 549Q132 549 151 535T170 489Q170 464 154 447T109 429Z"></path></g></g></g><g data-mml-node="mo" transform="translate(4852.6,0)"><path data-c="2C" d="M78 35T78 60T94 103T137 121Q165 121 187 96T210 8Q210 -27 201 -60T180 -117T154 -158T130 -185T117 -194Q113 -194 104 -185T95 -172Q95 -168 106 -156T131 -126T157 -76T173 -3V9L172 8Q170 7 167 6T161 3T152 1T140 0Q113 0 96 17Z"></path></g><g data-mml-node="mo" transform="translate(5297.3,0)"><path data-c="2026" d="M78 60Q78 84 95 102T138 120Q162 120 180 104T199 61Q199 36 182 18T139 0T96 17T78 60ZM525 60Q525 84 542 102T585 120Q609 120 627 104T646 61Q646 36 629 18T586 0T543 17T525 60ZM972 60Q972 84 989 102T1032 120Q1056 120 1074 104T1093 61Q1093 36 1076 18T1033 0T990 17T972 60Z"></path></g><g data-mml-node="mo" transform="translate(6635.9,0)"><path data-c="2C" d="M78 35T78 60T94 103T137 121Q165 121 187 96T210 8Q210 -27 201 -60T180 -117T154 -158T130 -185T117 -194Q113 -194 104 -185T95 -172Q95 -168 106 -156T131 -126T157 -76T173 -3V9L172 8Q170 7 167 6T161 3T152 1T140 0Q113 0 96 17Z"></path></g><g data-mml-node="msub" transform="translate(7080.6,0)"><g data-mml-node="mi"><path data-c="1D465" d="M52 289Q59 331 106 386T222 442Q257 442 286 424T329 379Q371 442 430 442Q467 442 494 420T522 361Q522 332 508 314T481 292T458 288Q439 288 427 299T415 328Q415 374 465 391Q454 404 425 404Q412 404 406 402Q368 386 350 336Q290 115 290 78Q290 50 306 38T341 26Q378 26 414 59T463 140Q466 150 469 151T485 153H489Q504 153 504 145Q504 144 502 134Q486 77 440 33T333 -11Q263 -11 227 52Q186 -10 133 -10H127Q78 -10 57 16T35 71Q35 103 54 123T99 143Q142 143 142 101Q142 81 130 66T107 46T94 41L91 40Q91 39 97 36T113 29T132 26Q168 26 194 71Q203 87 217 139T245 247T261 313Q266 340 266 352Q266 380 251 392T217 404Q177 404 142 372T93 290Q91 281 88 280T72 278H58Q52 284 52 289Z"></path></g><g data-mml-node="mn" transform="translate(605,-150) scale(0.707)"><path data-c="30" d="M96 585Q152 666 249 666Q297 666 345 640T423 548Q460 465 460 320Q460 165 417 83Q397 41 362 16T301 -15T250 -22Q224 -22 198 -16T137 16T82 83Q39 165 39 320Q39 494 96 585ZM321 597Q291 629 250 629Q208 629 178 597Q153 571 145 525T137 333Q137 175 145 125T181 46Q209 16 250 16Q290 16 318 46Q347 76 354 130T362 333Q362 478 354 524T321 597Z"></path></g></g><g data-mml-node="mo" transform="translate(8089.2,0)"><path data-c="5D" d="M22 710V750H159V-250H22V-210H119V710H22Z"></path></g></g></g></g></svg></mjx-container> 。</p>
+<p><strong>原理</strong>：无符号数编码的定义</p>
+<p><mjx-container class="MathJax" jax="SVG" display="true"><svg style="vertical-align: -2.819ex;" xmlns="http://www.w3.org/2000/svg" width="19.157ex" height="6.712ex" role="img" focusable="false" viewBox="0 -1720.9 8467.2 2966.8"><g stroke="currentColor" fill="currentColor" stroke-width="0" transform="scale(1,-1)"><g data-mml-node="math"><g data-mml-node="mi"><path data-c="1D435" d="M231 637Q204 637 199 638T194 649Q194 676 205 682Q206 683 335 683Q594 683 608 681Q671 671 713 636T756 544Q756 480 698 429T565 360L555 357Q619 348 660 311T702 219Q702 146 630 78T453 1Q446 0 242 0Q42 0 39 2Q35 5 35 10Q35 17 37 24Q42 43 47 45Q51 46 62 46H68Q95 46 128 49Q142 52 147 61Q150 65 219 339T288 628Q288 635 231 637ZM649 544Q649 574 634 600T585 634Q578 636 493 637Q473 637 451 637T416 636H403Q388 635 384 626Q382 622 352 506Q352 503 351 500L320 374H401Q482 374 494 376Q554 386 601 434T649 544ZM595 229Q595 273 572 302T512 336Q506 337 429 337Q311 337 310 336Q310 334 293 263T258 122L240 52Q240 48 252 48T333 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+<p>映射的范围</p>
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+<p><strong>原理</strong>：无符号数编码的唯一性</p>
+<p>函数 <mjx-container class="MathJax" jax="SVG"><svg style="vertical-align: -0.357ex;" xmlns="http://www.w3.org/2000/svg" width="5.727ex" height="1.902ex" role="img" focusable="false" viewBox="0 -683 2531.3 840.8"><g stroke="currentColor" fill="currentColor" stroke-width="0" transform="scale(1,-1)"><g data-mml-node="math"><g data-mml-node="mi"><path data-c="1D435" d="M231 637Q204 637 199 638T194 649Q194 676 205 682Q206 683 335 683Q594 683 608 681Q671 671 713 636T756 544Q756 480 698 429T565 360L555 357Q619 348 660 311T702 219Q702 146 630 78T453 1Q446 0 242 0Q42 0 39 2Q35 5 35 10Q35 17 37 24Q42 43 47 45Q51 46 62 46H68Q95 46 128 49Q142 52 147 61Q150 65 219 339T288 628Q288 635 231 637ZM649 544Q649 574 634 600T585 634Q578 636 493 637Q473 637 451 637T416 636H403Q388 635 384 626Q382 622 352 506Q352 503 351 500L320 374H401Q482 374 494 376Q554 386 601 434T649 544ZM595 229Q595 273 572 302T512 336Q506 337 429 337Q311 337 310 336Q310 334 293 263T258 122L240 52Q240 48 252 48T333 46Q422 46 429 47Q491 54 543 105T595 229Z"></path></g><g data-mml-node="mn" transform="translate(759,0)"><path data-c="32" d="M109 429Q82 429 66 447T50 491Q50 562 103 614T235 666Q326 666 387 610T449 465Q449 422 429 383T381 315T301 241Q265 210 201 149L142 93L218 92Q375 92 385 97Q392 99 409 186V189H449V186Q448 183 436 95T421 3V0H50V19V31Q50 38 56 46T86 81Q115 113 136 137Q145 147 170 174T204 211T233 244T261 278T284 308T305 340T320 369T333 401T340 431T343 464Q343 527 309 573T212 619Q179 619 154 602T119 569T109 550Q109 549 114 549Q132 549 151 535T170 489Q170 464 154 447T109 429Z"></path></g><g data-mml-node="msub" transform="translate(1259,0)"><g data-mml-node="mi"><path data-c="1D448" d="M107 637Q73 637 71 641Q70 643 70 649Q70 673 81 682Q83 683 98 683Q139 681 234 681Q268 681 297 681T342 682T362 682Q378 682 378 672Q378 670 376 658Q371 641 366 638H364Q362 638 359 638T352 638T343 637T334 637Q295 636 284 634T266 623Q265 621 238 518T184 302T154 169Q152 155 152 140Q152 86 183 55T269 24Q336 24 403 69T501 205L552 406Q599 598 599 606Q599 633 535 637Q511 637 511 648Q511 650 513 660Q517 676 519 679T529 683Q532 683 561 682T645 680Q696 680 723 681T752 682Q767 682 767 672Q767 650 759 642Q756 637 737 637Q666 633 648 597Q646 592 598 404Q557 235 548 205Q515 105 433 42T263 -22Q171 -22 116 34T60 167V183Q60 201 115 421Q164 622 164 628Q164 635 107 637Z"></path></g><g data-mml-node="TeXAtom" transform="translate(716,-150) scale(0.707)" data-mjx-texclass="ORD"><g data-mml-node="mi"><path data-c="1D464" d="M580 385Q580 406 599 424T641 443Q659 443 674 425T690 368Q690 339 671 253Q656 197 644 161T609 80T554 12T482 -11Q438 -11 404 5T355 48Q354 47 352 44Q311 -11 252 -11Q226 -11 202 -5T155 14T118 53T104 116Q104 170 138 262T173 379Q173 380 173 381Q173 390 173 393T169 400T158 404H154Q131 404 112 385T82 344T65 302T57 280Q55 278 41 278H27Q21 284 21 287Q21 293 29 315T52 366T96 418T161 441Q204 441 227 416T250 358Q250 340 217 250T184 111Q184 65 205 46T258 26Q301 26 334 87L339 96V119Q339 122 339 128T340 136T341 143T342 152T345 165T348 182T354 206T362 238T373 281Q402 395 406 404Q419 431 449 431Q468 431 475 421T483 402Q483 389 454 274T422 142Q420 131 420 107V100Q420 85 423 71T442 42T487 26Q558 26 600 148Q609 171 620 213T632 273Q632 306 619 325T593 357T580 385Z"></path></g></g></g></g></g></svg></mjx-container> 是一个双射。</p>
+<p><strong>原理</strong>：补码编码的定义</p>
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+<p>最高有效位 <mjx-container class="MathJax" jax="SVG"><svg style="vertical-align: -0.471ex;" xmlns="http://www.w3.org/2000/svg" width="4.672ex" height="1.471ex" role="img" focusable="false" viewBox="0 -442 2065 650"><g stroke="currentColor" fill="currentColor" stroke-width="0" transform="scale(1,-1)"><g data-mml-node="math"><g data-mml-node="msub"><g data-mml-node="mi"><path data-c="1D465" d="M52 289Q59 331 106 386T222 442Q257 442 286 424T329 379Q371 442 430 442Q467 442 494 420T522 361Q522 332 508 314T481 292T458 288Q439 288 427 299T415 328Q415 374 465 391Q454 404 425 404Q412 404 406 402Q368 386 350 336Q290 115 290 78Q290 50 306 38T341 26Q378 26 414 59T463 140Q466 150 469 151T485 153H489Q504 153 504 145Q504 144 502 134Q486 77 440 33T333 -11Q263 -11 227 52Q186 -10 133 -10H127Q78 -10 57 16T35 71Q35 103 54 123T99 143Q142 143 142 101Q142 81 130 66T107 46T94 41L91 40Q91 39 97 36T113 29T132 26Q168 26 194 71Q203 87 217 139T245 247T261 313Q266 340 266 352Q266 380 251 392T217 404Q177 404 142 372T93 290Q91 281 88 280T72 278H58Q52 284 52 289Z"></path></g><g data-mml-node="TeXAtom" transform="translate(605,-150) scale(0.707)" data-mjx-texclass="ORD"><g data-mml-node="mi"><path data-c="1D464" d="M580 385Q580 406 599 424T641 443Q659 443 674 425T690 368Q690 339 671 253Q656 197 644 161T609 80T554 12T482 -11Q438 -11 404 5T355 48Q354 47 352 44Q311 -11 252 -11Q226 -11 202 -5T155 14T118 53T104 116Q104 170 138 262T173 379Q173 380 173 381Q173 390 173 393T169 400T158 404H154Q131 404 112 385T82 344T65 302T57 280Q55 278 41 278H27Q21 284 21 287Q21 293 29 315T52 366T96 418T161 441Q204 441 227 416T250 358Q250 340 217 250T184 111Q184 65 205 46T258 26Q301 26 334 87L339 96V119Q339 122 339 128T340 136T341 143T342 152T345 165T348 182T354 206T362 238T373 281Q402 395 406 404Q419 431 449 431Q468 431 475 421T483 402Q483 389 454 274T422 142Q420 131 420 107V100Q420 85 423 71T442 42T487 26Q558 26 600 148Q609 171 620 213T632 273Q632 306 619 325T593 357T580 385Z"></path></g><g data-mml-node="mo" transform="translate(716,0)"><path data-c="2212" d="M84 237T84 250T98 270H679Q694 262 694 250T679 230H98Q84 237 84 250Z"></path></g><g data-mml-node="mn" transform="translate(1494,0)"><path data-c="31" d="M213 578L200 573Q186 568 160 563T102 556H83V602H102Q149 604 189 617T245 641T273 663Q275 666 285 666Q294 666 302 660V361L303 61Q310 54 315 52T339 48T401 46H427V0H416Q395 3 257 3Q121 3 100 0H88V46H114Q136 46 152 46T177 47T193 50T201 52T207 57T213 61V578Z"></path></g></g></g></g></g></svg></mjx-container> 称为符号位，权重为 <mjx-container class="MathJax" jax="SVG"><svg style="vertical-align: -0.186ex;" xmlns="http://www.w3.org/2000/svg" width="6.269ex" height="2.072ex" role="img" focusable="false" viewBox="0 -833.9 2771 915.9"><g stroke="currentColor" fill="currentColor" stroke-width="0" transform="scale(1,-1)"><g data-mml-node="math"><g data-mml-node="mo"><path data-c="2212" d="M84 237T84 250T98 270H679Q694 262 694 250T679 230H98Q84 237 84 250Z"></path></g><g data-mml-node="msup" transform="translate(778,0)"><g data-mml-node="mn"><path data-c="32" d="M109 429Q82 429 66 447T50 491Q50 562 103 614T235 666Q326 666 387 610T449 465Q449 422 429 383T381 315T301 241Q265 210 201 149L142 93L218 92Q375 92 385 97Q392 99 409 186V189H449V186Q448 183 436 95T421 3V0H50V19V31Q50 38 56 46T86 81Q115 113 136 137Q145 147 170 174T204 211T233 244T261 278T284 308T305 340T320 369T333 401T340 431T343 464Q343 527 309 573T212 619Q179 619 154 602T119 569T109 550Q109 549 114 549Q132 549 151 535T170 489Q170 464 154 447T109 429Z"></path></g><g data-mml-node="TeXAtom" transform="translate(533,363) scale(0.707)" data-mjx-texclass="ORD"><g data-mml-node="mi"><path data-c="1D464" d="M580 385Q580 406 599 424T641 443Q659 443 674 425T690 368Q690 339 671 253Q656 197 644 161T609 80T554 12T482 -11Q438 -11 404 5T355 48Q354 47 352 44Q311 -11 252 -11Q226 -11 202 -5T155 14T118 53T104 116Q104 170 138 262T173 379Q173 380 173 381Q173 390 173 393T169 400T158 404H154Q131 404 112 385T82 344T65 302T57 280Q55 278 41 278H27Q21 284 21 287Q21 293 29 315T52 366T96 418T161 441Q204 441 227 416T250 358Q250 340 217 250T184 111Q184 65 205 46T258 26Q301 26 334 87L339 96V119Q339 122 339 128T340 136T341 143T342 152T345 165T348 182T354 206T362 238T373 281Q402 395 406 404Q419 431 449 431Q468 431 475 421T483 402Q483 389 454 274T422 142Q420 131 420 107V100Q420 85 423 71T442 42T487 26Q558 26 600 148Q609 171 620 213T632 273Q632 306 619 325T593 357T580 385Z"></path></g><g data-mml-node="mo" transform="translate(716,0)"><path data-c="2212" d="M84 237T84 250T98 270H679Q694 262 694 250T679 230H98Q84 237 84 250Z"></path></g><g data-mml-node="mn" transform="translate(1494,0)"><path data-c="31" d="M213 578L200 573Q186 568 160 563T102 556H83V602H102Q149 604 189 617T245 641T273 663Q275 666 285 666Q294 666 302 660V361L303 61Q310 54 315 52T339 48T401 46H427V0H416Q395 3 257 3Q121 3 100 0H88V46H114Q136 46 152 46T177 47T193 50T201 52T207 57T213 61V578Z"></path></g></g></g></g></g></svg></mjx-container>，符号位被设置为 1 时，表示值为负，当设置为 0 时，值为非负。</p>
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490T641 551Q641 586 628 604T573 629Q568 630 515 631Q469 631 457 630T439 622Q438 621 368 343T298 60Q298 48 386 46Q418 46 427 45T436 36Q436 31 433 22Q429 4 424 1L422 0Q419 0 415 0Q410 0 363 1T228 2Q99 2 64 0H49Q43 6 43 9T45 27Q49 40 55 46H83H94Q174 46 189 55Q190 56 191 56Q196 59 201 76T241 233Q258 301 269 344Q339 619 339 625Q339 630 310 630H279Q212 630 191 624Q146 614 121 583T67 467Q60 445 57 441T43 437H40Z"></path></g><g data-mml-node="mi" transform="translate(14576.6,0)"><path data-c="1D440" d="M289 629Q289 635 232 637Q208 637 201 638T194 648Q194 649 196 659Q197 662 198 666T199 671T201 676T203 679T207 681T212 683T220 683T232 684Q238 684 262 684T307 683Q386 683 398 683T414 678Q415 674 451 396L487 117L510 154Q534 190 574 254T662 394Q837 673 839 675Q840 676 842 678T846 681L852 683H948Q965 683 988 683T1017 684Q1051 684 1051 673Q1051 668 1048 656T1045 643Q1041 637 1008 637Q968 636 957 634T939 623Q936 618 867 340T797 59Q797 55 798 54T805 50T822 48T855 46H886Q892 37 892 35Q892 19 885 5Q880 0 869 0Q864 0 828 1T736 2Q675 2 644 2T609 1Q592 1 592 11Q592 13 594 25Q598 41 602 43T625 46Q652 46 685 49Q699 52 704 61Q706 65 742 207T813 490T848 631L654 322Q458 10 453 5Q451 4 449 3Q444 0 433 0Q418 0 415 7Q413 11 374 317L335 624L267 354Q200 88 200 79Q206 46 272 46H282Q288 41 289 37T286 19Q282 3 278 1Q274 0 267 0Q265 0 255 0T221 1T157 2Q127 2 95 1T58 0Q43 0 39 2T35 11Q35 13 38 25T43 40Q45 46 65 46Q135 46 154 86Q158 92 223 354T289 629Z"></path></g><g data-mml-node="mi" transform="translate(15627.6,0)"><path data-c="1D44E" d="M33 157Q33 258 109 349T280 441Q331 441 370 392Q386 422 416 422Q429 422 439 414T449 394Q449 381 412 234T374 68Q374 43 381 35T402 26Q411 27 422 35Q443 55 463 131Q469 151 473 152Q475 153 483 153H487Q506 153 506 144Q506 138 501 117T481 63T449 13Q436 0 417 -8Q409 -10 393 -10Q359 -10 336 5T306 36L300 51Q299 52 296 50Q294 48 292 46Q233 -10 172 -10Q117 -10 75 30T33 157ZM351 328Q351 334 346 350T323 385T277 405Q242 405 210 374T160 293Q131 214 119 129Q119 126 119 118T118 106Q118 61 136 44T179 26Q217 26 254 59T298 110Q300 114 325 217T351 328Z"></path></g><g data-mml-node="msub" transform="translate(16156.6,0)"><g data-mml-node="mi"><path data-c="1D465" d="M52 289Q59 331 106 386T222 442Q257 442 286 424T329 379Q371 442 430 442Q467 442 494 420T522 361Q522 332 508 314T481 292T458 288Q439 288 427 299T415 328Q415 374 465 391Q454 404 425 404Q412 404 406 402Q368 386 350 336Q290 115 290 78Q290 50 306 38T341 26Q378 26 414 59T463 140Q466 150 469 151T485 153H489Q504 153 504 145Q504 144 502 134Q486 77 440 33T333 -11Q263 -11 227 52Q186 -10 133 -10H127Q78 -10 57 16T35 71Q35 103 54 123T99 143Q142 143 142 101Q142 81 130 66T107 46T94 41L91 40Q91 39 97 36T113 29T132 26Q168 26 194 71Q203 87 217 139T245 247T261 313Q266 340 266 352Q266 380 251 392T217 404Q177 404 142 372T93 290Q91 281 88 280T72 278H58Q52 284 52 289Z"></path></g><g data-mml-node="mi" transform="translate(605,-150) scale(0.707)"><path data-c="1D464" d="M580 385Q580 406 599 424T641 443Q659 443 674 425T690 368Q690 339 671 253Q656 197 644 161T609 80T554 12T482 -11Q438 -11 404 5T355 48Q354 47 352 44Q311 -11 252 -11Q226 -11 202 -5T155 14T118 53T104 116Q104 170 138 262T173 379Q173 380 173 381Q173 390 173 393T169 400T158 404H154Q131 404 112 385T82 344T65 302T57 280Q55 278 41 278H27Q21 284 21 287Q21 293 29 315T52 366T96 418T161 441Q204 441 227 416T250 358Q250 340 217 250T184 111Q184 65 205 46T258 26Q301 26 334 87L339 96V119Q339 122 339 128T340 136T341 143T342 152T345 165T348 182T354 206T362 238T373 281Q402 395 406 404Q419 431 449 431Q468 431 475 421T483 402Q483 389 454 274T422 142Q420 131 420 107V100Q420 85 423 71T442 42T487 26Q558 26 600 148Q609 171 620 213T632 273Q632 306 619 325T593 357T580 385Z"></path></g></g><g data-mml-node="mo" transform="translate(17317.9,0)"><path data-c="7D" d="M65 731Q65 745 68 747T88 750Q171 750 216 725T279 670Q288 649 289 635T291 501Q292 362 293 357Q306 312 345 291T417 269Q428 269 431 266T434 250T431 234T417 231Q380 231 345 210T298 157Q293 143 292 121T291 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+<p><strong>原理</strong>：补码编码的唯一性</p>
+<p>函数 <mjx-container class="MathJax" jax="SVG"><svg style="vertical-align: -0.357ex;" xmlns="http://www.w3.org/2000/svg" width="5.503ex" height="1.902ex" role="img" focusable="false" viewBox="0 -683 2432.3 840.8"><g stroke="currentColor" fill="currentColor" stroke-width="0" transform="scale(1,-1)"><g data-mml-node="math"><g data-mml-node="mi"><path data-c="1D435" d="M231 637Q204 637 199 638T194 649Q194 676 205 682Q206 683 335 683Q594 683 608 681Q671 671 713 636T756 544Q756 480 698 429T565 360L555 357Q619 348 660 311T702 219Q702 146 630 78T453 1Q446 0 242 0Q42 0 39 2Q35 5 35 10Q35 17 37 24Q42 43 47 45Q51 46 62 46H68Q95 46 128 49Q142 52 147 61Q150 65 219 339T288 628Q288 635 231 637ZM649 544Q649 574 634 600T585 634Q578 636 493 637Q473 637 451 637T416 636H403Q388 635 384 626Q382 622 352 506Q352 503 351 500L320 374H401Q482 374 494 376Q554 386 601 434T649 544ZM595 229Q595 273 572 302T512 336Q506 337 429 337Q311 337 310 336Q310 334 293 263T258 122L240 52Q240 48 252 48T333 46Q422 46 429 47Q491 54 543 105T595 229Z"></path></g><g data-mml-node="mn" transform="translate(759,0)"><path data-c="32" d="M109 429Q82 429 66 447T50 491Q50 562 103 614T235 666Q326 666 387 610T449 465Q449 422 429 383T381 315T301 241Q265 210 201 149L142 93L218 92Q375 92 385 97Q392 99 409 186V189H449V186Q448 183 436 95T421 3V0H50V19V31Q50 38 56 46T86 81Q115 113 136 137Q145 147 170 174T204 211T233 244T261 278T284 308T305 340T320 369T333 401T340 431T343 464Q343 527 309 573T212 619Q179 619 154 602T119 569T109 550Q109 549 114 549Q132 549 151 535T170 489Q170 464 154 447T109 429Z"></path></g><g data-mml-node="msub" transform="translate(1259,0)"><g data-mml-node="mi"><path data-c="1D447" d="M40 437Q21 437 21 445Q21 450 37 501T71 602L88 651Q93 669 101 677H569H659Q691 677 697 676T704 667Q704 661 687 553T668 444Q668 437 649 437Q640 437 637 437T631 442L629 445Q629 451 635 490T641 551Q641 586 628 604T573 629Q568 630 515 631Q469 631 457 630T439 622Q438 621 368 343T298 60Q298 48 386 46Q418 46 427 45T436 36Q436 31 433 22Q429 4 424 1L422 0Q419 0 415 0Q410 0 363 1T228 2Q99 2 64 0H49Q43 6 43 9T45 27Q49 40 55 46H83H94Q174 46 189 55Q190 56 191 56Q196 59 201 76T241 233Q258 301 269 344Q339 619 339 625Q339 630 310 630H279Q212 630 191 624Q146 614 121 583T67 467Q60 445 57 441T43 437H40Z"></path></g><g data-mml-node="TeXAtom" transform="translate(617,-150) scale(0.707)" data-mjx-texclass="ORD"><g data-mml-node="mi"><path data-c="1D464" d="M580 385Q580 406 599 424T641 443Q659 443 674 425T690 368Q690 339 671 253Q656 197 644 161T609 80T554 12T482 -11Q438 -11 404 5T355 48Q354 47 352 44Q311 -11 252 -11Q226 -11 202 -5T155 14T118 53T104 116Q104 170 138 262T173 379Q173 380 173 381Q173 390 173 393T169 400T158 404H154Q131 404 112 385T82 344T65 302T57 280Q55 278 41 278H27Q21 284 21 287Q21 293 29 315T52 366T96 418T161 441Q204 441 227 416T250 358Q250 340 217 250T184 111Q184 65 205 46T258 26Q301 26 334 87L339 96V119Q339 122 339 128T340 136T341 143T342 152T345 165T348 182T354 206T362 238T373 281Q402 395 406 404Q419 431 449 431Q468 431 475 421T483 402Q483 389 454 274T422 142Q420 131 420 107V100Q420 85 423 71T442 42T487 26Q558 26 600 148Q609 171 620 213T632 273Q632 306 619 325T593 357T580 385Z"></path></g></g></g></g></g></svg></mjx-container> 是一个双射。</p>
+<p>观察特殊值</p>
+<table>
 <thead>
 <tr>
-<th>快捷键</th>
-<th>功能</th>
+<th>数</th>
+<th>w=8</th>
 </tr>
 </thead>
 <tbody><tr>
-<td><code>Ctrl + x</code> + <code>Ctrl + n</code></td>
-<td>使用当前文件的内容文字作为关键词，予以补齐</td>
+<td><mjx-container class="MathJax" jax="SVG"><svg style="vertical-align: -0.357ex;" xmlns="http://www.w3.org/2000/svg" width="7.937ex" height="1.902ex" role="img" focusable="false" viewBox="0 -683 3508.3 840.8"><g stroke="currentColor" fill="currentColor" stroke-width="0" transform="scale(1,-1)"><g data-mml-node="math"><g data-mml-node="mi"><path data-c="1D448" d="M107 637Q73 637 71 641Q70 643 70 649Q70 673 81 682Q83 683 98 683Q139 681 234 681Q268 681 297 681T342 682T362 682Q378 682 378 672Q378 670 376 658Q371 641 366 638H364Q362 638 359 638T352 638T343 637T334 637Q295 636 284 634T266 623Q265 621 238 518T184 302T154 169Q152 155 152 140Q152 86 183 55T269 24Q336 24 403 69T501 205L552 406Q599 598 599 606Q599 633 535 637Q511 637 511 648Q511 650 513 660Q517 676 519 679T529 683Q532 683 561 682T645 680Q696 680 723 681T752 682Q767 682 767 672Q767 650 759 642Q756 637 737 637Q666 633 648 597Q646 592 598 404Q557 235 548 205Q515 105 433 42T263 -22Q171 -22 116 34T60 167V183Q60 201 115 421Q164 622 164 628Q164 635 107 637Z"></path></g><g data-mml-node="mi" transform="translate(767,0)"><path data-c="1D440" d="M289 629Q289 635 232 637Q208 637 201 638T194 648Q194 649 196 659Q197 662 198 666T199 671T201 676T203 679T207 681T212 683T220 683T232 684Q238 684 262 684T307 683Q386 683 398 683T414 678Q415 674 451 396L487 117L510 154Q534 190 574 254T662 394Q837 673 839 675Q840 676 842 678T846 681L852 683H948Q965 683 988 683T1017 684Q1051 684 1051 673Q1051 668 1048 656T1045 643Q1041 637 1008 637Q968 636 957 634T939 623Q936 618 867 340T797 59Q797 55 798 54T805 50T822 48T855 46H886Q892 37 892 35Q892 19 885 5Q880 0 869 0Q864 0 828 1T736 2Q675 2 644 2T609 1Q592 1 592 11Q592 13 594 25Q598 41 602 43T625 46Q652 46 685 49Q699 52 704 61Q706 65 742 207T813 490T848 631L654 322Q458 10 453 5Q451 4 449 3Q444 0 433 0Q418 0 415 7Q413 11 374 317L335 624L267 354Q200 88 200 79Q206 46 272 46H282Q288 41 289 37T286 19Q282 3 278 1Q274 0 267 0Q265 0 255 0T221 1T157 2Q127 2 95 1T58 0Q43 0 39 2T35 11Q35 13 38 25T43 40Q45 46 65 46Q135 46 154 86Q158 92 223 354T289 629Z"></path></g><g data-mml-node="mi" transform="translate(1818,0)"><path data-c="1D44E" d="M33 157Q33 258 109 349T280 441Q331 441 370 392Q386 422 416 422Q429 422 439 414T449 394Q449 381 412 234T374 68Q374 43 381 35T402 26Q411 27 422 35Q443 55 463 131Q469 151 473 152Q475 153 483 153H487Q506 153 506 144Q506 138 501 117T481 63T449 13Q436 0 417 -8Q409 -10 393 -10Q359 -10 336 5T306 36L300 51Q299 52 296 50Q294 48 292 46Q233 -10 172 -10Q117 -10 75 30T33 157ZM351 328Q351 334 346 350T323 385T277 405Q242 405 210 374T160 293Q131 214 119 129Q119 126 119 118T118 106Q118 61 136 44T179 26Q217 26 254 59T298 110Q300 114 325 217T351 328Z"></path></g><g data-mml-node="msub" transform="translate(2347,0)"><g data-mml-node="mi"><path data-c="1D465" d="M52 289Q59 331 106 386T222 442Q257 442 286 424T329 379Q371 442 430 442Q467 442 494 420T522 361Q522 332 508 314T481 292T458 288Q439 288 427 299T415 328Q415 374 465 391Q454 404 425 404Q412 404 406 402Q368 386 350 336Q290 115 290 78Q290 50 306 38T341 26Q378 26 414 59T463 140Q466 150 469 151T485 153H489Q504 153 504 145Q504 144 502 134Q486 77 440 33T333 -11Q263 -11 227 52Q186 -10 133 -10H127Q78 -10 57 16T35 71Q35 103 54 123T99 143Q142 143 142 101Q142 81 130 66T107 46T94 41L91 40Q91 39 97 36T113 29T132 26Q168 26 194 71Q203 87 217 139T245 247T261 313Q266 340 266 352Q266 380 251 392T217 404Q177 404 142 372T93 290Q91 281 88 280T72 278H58Q52 284 52 289Z"></path></g><g data-mml-node="mi" transform="translate(605,-150) scale(0.707)"><path data-c="1D464" d="M580 385Q580 406 599 424T641 443Q659 443 674 425T690 368Q690 339 671 253Q656 197 644 161T609 80T554 12T482 -11Q438 -11 404 5T355 48Q354 47 352 44Q311 -11 252 -11Q226 -11 202 -5T155 14T118 53T104 116Q104 170 138 262T173 379Q173 380 173 381Q173 390 173 393T169 400T158 404H154Q131 404 112 385T82 344T65 302T57 280Q55 278 41 278H27Q21 284 21 287Q21 293 29 315T52 366T96 418T161 441Q204 441 227 416T250 358Q250 340 217 250T184 111Q184 65 205 46T258 26Q301 26 334 87L339 96V119Q339 122 339 128T340 136T341 143T342 152T345 165T348 182T354 206T362 238T373 281Q402 395 406 404Q419 431 449 431Q468 431 475 421T483 402Q483 389 454 274T422 142Q420 131 420 107V100Q420 85 423 71T442 42T487 26Q558 26 600 148Q609 171 620 213T632 273Q632 306 619 325T593 357T580 385Z"></path></g></g></g></g></svg></mjx-container></td>
+<td>11111111</td>
 </tr>
 <tr>
-<td><code>Ctrl + x</code> + <code>Ctrl + f</code></td>
-<td>使用当前目录的文件名作为关键词，予以补齐</td>
+<td><mjx-container class="MathJax" jax="SVG"><svg style="vertical-align: -0.357ex;" xmlns="http://www.w3.org/2000/svg" width="7.442ex" height="1.902ex" role="img" focusable="false" viewBox="0 -683 3289.3 840.8"><g stroke="currentColor" fill="currentColor" stroke-width="0" transform="scale(1,-1)"><g data-mml-node="math"><g data-mml-node="mi"><path data-c="1D447" d="M40 437Q21 437 21 445Q21 450 37 501T71 602L88 651Q93 669 101 677H569H659Q691 677 697 676T704 667Q704 661 687 553T668 444Q668 437 649 437Q640 437 637 437T631 442L629 445Q629 451 635 490T641 551Q641 586 628 604T573 629Q568 630 515 631Q469 631 457 630T439 622Q438 621 368 343T298 60Q298 48 386 46Q418 46 427 45T436 36Q436 31 433 22Q429 4 424 1L422 0Q419 0 415 0Q410 0 363 1T228 2Q99 2 64 0H49Q43 6 43 9T45 27Q49 40 55 46H83H94Q174 46 189 55Q190 56 191 56Q196 59 201 76T241 233Q258 301 269 344Q339 619 339 625Q339 630 310 630H279Q212 630 191 624Q146 614 121 583T67 467Q60 445 57 441T43 437H40Z"></path></g><g data-mml-node="mi" transform="translate(704,0)"><path data-c="1D440" d="M289 629Q289 635 232 637Q208 637 201 638T194 648Q194 649 196 659Q197 662 198 666T199 671T201 676T203 679T207 681T212 683T220 683T232 684Q238 684 262 684T307 683Q386 683 398 683T414 678Q415 674 451 396L487 117L510 154Q534 190 574 254T662 394Q837 673 839 675Q840 676 842 678T846 681L852 683H948Q965 683 988 683T1017 684Q1051 684 1051 673Q1051 668 1048 656T1045 643Q1041 637 1008 637Q968 636 957 634T939 623Q936 618 867 340T797 59Q797 55 798 54T805 50T822 48T855 46H886Q892 37 892 35Q892 19 885 5Q880 0 869 0Q864 0 828 1T736 2Q675 2 644 2T609 1Q592 1 592 11Q592 13 594 25Q598 41 602 43T625 46Q652 46 685 49Q699 52 704 61Q706 65 742 207T813 490T848 631L654 322Q458 10 453 5Q451 4 449 3Q444 0 433 0Q418 0 415 7Q413 11 374 317L335 624L267 354Q200 88 200 79Q206 46 272 46H282Q288 41 289 37T286 19Q282 3 278 1Q274 0 267 0Q265 0 255 0T221 1T157 2Q127 2 95 1T58 0Q43 0 39 2T35 11Q35 13 38 25T43 40Q45 46 65 46Q135 46 154 86Q158 92 223 354T289 629Z"></path></g><g data-mml-node="mi" transform="translate(1755,0)"><path data-c="1D456" d="M184 600Q184 624 203 642T247 661Q265 661 277 649T290 619Q290 596 270 577T226 557Q211 557 198 567T184 600ZM21 287Q21 295 30 318T54 369T98 420T158 442Q197 442 223 419T250 357Q250 340 236 301T196 196T154 83Q149 61 149 51Q149 26 166 26Q175 26 185 29T208 43T235 78T260 137Q263 149 265 151T282 153Q302 153 302 143Q302 135 293 112T268 61T223 11T161 -11Q129 -11 102 10T74 74Q74 91 79 106T122 220Q160 321 166 341T173 380Q173 404 156 404H154Q124 404 99 371T61 287Q60 286 59 284T58 281T56 279T53 278T49 278T41 278H27Q21 284 21 287Z"></path></g><g data-mml-node="msub" transform="translate(2100,0)"><g data-mml-node="mi"><path data-c="1D45B" d="M21 287Q22 293 24 303T36 341T56 388T89 425T135 442Q171 442 195 424T225 390T231 369Q231 367 232 367L243 378Q304 442 382 442Q436 442 469 415T503 336T465 179T427 52Q427 26 444 26Q450 26 453 27Q482 32 505 65T540 145Q542 153 560 153Q580 153 580 145Q580 144 576 130Q568 101 554 73T508 17T439 -10Q392 -10 371 17T350 73Q350 92 386 193T423 345Q423 404 379 404H374Q288 404 229 303L222 291L189 157Q156 26 151 16Q138 -11 108 -11Q95 -11 87 -5T76 7T74 17Q74 30 112 180T152 343Q153 348 153 366Q153 405 129 405Q91 405 66 305Q60 285 60 284Q58 278 41 278H27Q21 284 21 287Z"></path></g><g data-mml-node="mi" transform="translate(633,-150) scale(0.707)"><path data-c="1D464" d="M580 385Q580 406 599 424T641 443Q659 443 674 425T690 368Q690 339 671 253Q656 197 644 161T609 80T554 12T482 -11Q438 -11 404 5T355 48Q354 47 352 44Q311 -11 252 -11Q226 -11 202 -5T155 14T118 53T104 116Q104 170 138 262T173 379Q173 380 173 381Q173 390 173 393T169 400T158 404H154Q131 404 112 385T82 344T65 302T57 280Q55 278 41 278H27Q21 284 21 287Q21 293 29 315T52 366T96 418T161 441Q204 441 227 416T250 358Q250 340 217 250T184 111Q184 65 205 46T258 26Q301 26 334 87L339 96V119Q339 122 339 128T340 136T341 143T342 152T345 165T348 182T354 206T362 238T373 281Q402 395 406 404Q419 431 449 431Q468 431 475 421T483 402Q483 389 454 274T422 142Q420 131 420 107V100Q420 85 423 71T442 42T487 26Q558 26 600 148Q609 171 620 213T632 273Q632 306 619 325T593 357T580 385Z"></path></g></g></g></g></svg></mjx-container></td>
+<td>10000000</td>
 </tr>
 <tr>
-<td><code>Ctrl + x</code> + <code>Ctrl + o</code></td>
-<td>使用扩展名作为语法补充，以 Vim 内置的关键词，予以补齐</td>
+<td><mjx-container class="MathJax" jax="SVG"><svg style="vertical-align: -0.357ex;" xmlns="http://www.w3.org/2000/svg" width="7.795ex" height="1.902ex" role="img" focusable="false" viewBox="0 -683 3445.3 840.8"><g stroke="currentColor" fill="currentColor" stroke-width="0" transform="scale(1,-1)"><g data-mml-node="math"><g data-mml-node="mi"><path data-c="1D447" d="M40 437Q21 437 21 445Q21 450 37 501T71 602L88 651Q93 669 101 677H569H659Q691 677 697 676T704 667Q704 661 687 553T668 444Q668 437 649 437Q640 437 637 437T631 442L629 445Q629 451 635 490T641 551Q641 586 628 604T573 629Q568 630 515 631Q469 631 457 630T439 622Q438 621 368 343T298 60Q298 48 386 46Q418 46 427 45T436 36Q436 31 433 22Q429 4 424 1L422 0Q419 0 415 0Q410 0 363 1T228 2Q99 2 64 0H49Q43 6 43 9T45 27Q49 40 55 46H83H94Q174 46 189 55Q190 56 191 56Q196 59 201 76T241 233Q258 301 269 344Q339 619 339 625Q339 630 310 630H279Q212 630 191 624Q146 614 121 583T67 467Q60 445 57 441T43 437H40Z"></path></g><g data-mml-node="mi" transform="translate(704,0)"><path data-c="1D440" d="M289 629Q289 635 232 637Q208 637 201 638T194 648Q194 649 196 659Q197 662 198 666T199 671T201 676T203 679T207 681T212 683T220 683T232 684Q238 684 262 684T307 683Q386 683 398 683T414 678Q415 674 451 396L487 117L510 154Q534 190 574 254T662 394Q837 673 839 675Q840 676 842 678T846 681L852 683H948Q965 683 988 683T1017 684Q1051 684 1051 673Q1051 668 1048 656T1045 643Q1041 637 1008 637Q968 636 957 634T939 623Q936 618 867 340T797 59Q797 55 798 54T805 50T822 48T855 46H886Q892 37 892 35Q892 19 885 5Q880 0 869 0Q864 0 828 1T736 2Q675 2 644 2T609 1Q592 1 592 11Q592 13 594 25Q598 41 602 43T625 46Q652 46 685 49Q699 52 704 61Q706 65 742 207T813 490T848 631L654 322Q458 10 453 5Q451 4 449 3Q444 0 433 0Q418 0 415 7Q413 11 374 317L335 624L267 354Q200 88 200 79Q206 46 272 46H282Q288 41 289 37T286 19Q282 3 278 1Q274 0 267 0Q265 0 255 0T221 1T157 2Q127 2 95 1T58 0Q43 0 39 2T35 11Q35 13 38 25T43 40Q45 46 65 46Q135 46 154 86Q158 92 223 354T289 629Z"></path></g><g data-mml-node="mi" transform="translate(1755,0)"><path data-c="1D44E" d="M33 157Q33 258 109 349T280 441Q331 441 370 392Q386 422 416 422Q429 422 439 414T449 394Q449 381 412 234T374 68Q374 43 381 35T402 26Q411 27 422 35Q443 55 463 131Q469 151 473 152Q475 153 483 153H487Q506 153 506 144Q506 138 501 117T481 63T449 13Q436 0 417 -8Q409 -10 393 -10Q359 -10 336 5T306 36L300 51Q299 52 296 50Q294 48 292 46Q233 -10 172 -10Q117 -10 75 30T33 157ZM351 328Q351 334 346 350T323 385T277 405Q242 405 210 374T160 293Q131 214 119 129Q119 126 119 118T118 106Q118 61 136 44T179 26Q217 26 254 59T298 110Q300 114 325 217T351 328Z"></path></g><g data-mml-node="msub" transform="translate(2284,0)"><g data-mml-node="mi"><path data-c="1D465" d="M52 289Q59 331 106 386T222 442Q257 442 286 424T329 379Q371 442 430 442Q467 442 494 420T522 361Q522 332 508 314T481 292T458 288Q439 288 427 299T415 328Q415 374 465 391Q454 404 425 404Q412 404 406 402Q368 386 350 336Q290 115 290 78Q290 50 306 38T341 26Q378 26 414 59T463 140Q466 150 469 151T485 153H489Q504 153 504 145Q504 144 502 134Q486 77 440 33T333 -11Q263 -11 227 52Q186 -10 133 -10H127Q78 -10 57 16T35 71Q35 103 54 123T99 143Q142 143 142 101Q142 81 130 66T107 46T94 41L91 40Q91 39 97 36T113 29T132 26Q168 26 194 71Q203 87 217 139T245 247T261 313Q266 340 266 352Q266 380 251 392T217 404Q177 404 142 372T93 290Q91 281 88 280T72 278H58Q52 284 52 289Z"></path></g><g data-mml-node="mi" transform="translate(605,-150) scale(0.707)"><path data-c="1D464" d="M580 385Q580 406 599 424T641 443Q659 443 674 425T690 368Q690 339 671 253Q656 197 644 161T609 80T554 12T482 -11Q438 -11 404 5T355 48Q354 47 352 44Q311 -11 252 -11Q226 -11 202 -5T155 14T118 53T104 116Q104 170 138 262T173 379Q173 380 173 381Q173 390 173 393T169 400T158 404H154Q131 404 112 385T82 344T65 302T57 280Q55 278 41 278H27Q21 284 21 287Q21 293 29 315T52 366T96 418T161 441Q204 441 227 416T250 358Q250 340 217 250T184 111Q184 65 205 46T258 26Q301 26 334 87L339 96V119Q339 122 339 128T340 136T341 143T342 152T345 165T348 182T354 206T362 238T373 281Q402 395 406 404Q419 431 449 431Q468 431 475 421T483 402Q483 389 454 274T422 142Q420 131 420 107V100Q420 85 423 71T442 42T487 26Q558 26 600 148Q609 171 620 213T632 273Q632 306 619 325T593 357T580 385Z"></path></g></g></g></g></svg></mjx-container></td>
+<td>01111111</td>
 </tr>
-</tbody></table>
-<h2 id="环境配置"><a href="#环境配置" class="headerlink" title="环境配置"></a>环境配置</h2><table>
-<thead>
 <tr>
-<th>设置参数</th>
-<th>功能</th>
-</tr>
-</thead>
-<tbody><tr>
-<td><code>:set nu</code> </br> <code>:set nonu</code></td>
-<td>设置和取消行号</td>
+<td>-1</td>
+<td>11111111</td>
 </tr>
 <tr>
-<td><code>:syntax on</code> </br> <code>:syntax off</code></td>
-<td>是否依据程序相关语法显示不同颜色</td>
+<td>0</td>
+<td>00000000</td>
 </tr>
 </tbody></table>
+<ol>
+<li>补码的范围不对称<br><mjx-container class="MathJax" jax="SVG" display="true"><svg style="vertical-align: -0.564ex;" xmlns="http://www.w3.org/2000/svg" width="24.666ex" height="2.26ex" role="img" focusable="false" viewBox="0 -749.5 10902.6 999"><g stroke="currentColor" fill="currentColor" stroke-width="0" transform="scale(1,-1)"><g data-mml-node="math"><g data-mml-node="mo" transform="translate(0 -0.5)"><path data-c="7C" d="M139 -249H137Q125 -249 119 -235V251L120 737Q130 750 139 750Q152 750 159 735V-235Q151 -249 141 -249H139Z"></path></g><g data-mml-node="mi" transform="translate(278,0)"><path data-c="1D447" d="M40 437Q21 437 21 445Q21 450 37 501T71 602L88 651Q93 669 101 677H569H659Q691 677 697 676T704 667Q704 661 687 553T668 444Q668 437 649 437Q640 437 637 437T631 442L629 445Q629 451 635 490T641 551Q641 586 628 604T573 629Q568 630 515 631Q469 631 457 630T439 622Q438 621 368 343T298 60Q298 48 386 46Q418 46 427 45T436 36Q436 31 433 22Q429 4 424 1L422 0Q419 0 415 0Q410 0 363 1T228 2Q99 2 64 0H49Q43 6 43 9T45 27Q49 40 55 46H83H94Q174 46 189 55Q190 56 191 56Q196 59 201 76T241 233Q258 301 269 344Q339 619 339 625Q339 630 310 630H279Q212 630 191 624Q146 614 121 583T67 467Q60 445 57 441T43 437H40Z"></path></g><g data-mml-node="mi" transform="translate(982,0)"><path data-c="1D440" d="M289 629Q289 635 232 637Q208 637 201 638T194 648Q194 649 196 659Q197 662 198 666T199 671T201 676T203 679T207 681T212 683T220 683T232 684Q238 684 262 684T307 683Q386 683 398 683T414 678Q415 674 451 396L487 117L510 154Q534 190 574 254T662 394Q837 673 839 675Q840 676 842 678T846 681L852 683H948Q965 683 988 683T1017 684Q1051 684 1051 673Q1051 668 1048 656T1045 643Q1041 637 1008 637Q968 636 957 634T939 623Q936 618 867 340T797 59Q797 55 798 54T805 50T822 48T855 46H886Q892 37 892 35Q892 19 885 5Q880 0 869 0Q864 0 828 1T736 2Q675 2 644 2T609 1Q592 1 592 11Q592 13 594 25Q598 41 602 43T625 46Q652 46 685 49Q699 52 704 61Q706 65 742 207T813 490T848 631L654 322Q458 10 453 5Q451 4 449 3Q444 0 433 0Q418 0 415 7Q413 11 374 317L335 624L267 354Q200 88 200 79Q206 46 272 46H282Q288 41 289 37T286 19Q282 3 278 1Q274 0 267 0Q265 0 255 0T221 1T157 2Q127 2 95 1T58 0Q43 0 39 2T35 11Q35 13 38 25T43 40Q45 46 65 46Q135 46 154 86Q158 92 223 354T289 629Z"></path></g><g data-mml-node="mi" transform="translate(2033,0)"><path data-c="1D456" d="M184 600Q184 624 203 642T247 661Q265 661 277 649T290 619Q290 596 270 577T226 557Q211 557 198 567T184 600ZM21 287Q21 295 30 318T54 369T98 420T158 442Q197 442 223 419T250 357Q250 340 236 301T196 196T154 83Q149 61 149 51Q149 26 166 26Q175 26 185 29T208 43T235 78T260 137Q263 149 265 151T282 153Q302 153 302 143Q302 135 293 112T268 61T223 11T161 -11Q129 -11 102 10T74 74Q74 91 79 106T122 220Q160 321 166 341T173 380Q173 404 156 404H154Q124 404 99 371T61 287Q60 286 59 284T58 281T56 279T53 278T49 278T41 278H27Q21 284 21 287Z"></path></g><g data-mml-node="msub" transform="translate(2378,0)"><g data-mml-node="mi"><path data-c="1D45B" d="M21 287Q22 293 24 303T36 341T56 388T89 425T135 442Q171 442 195 424T225 390T231 369Q231 367 232 367L243 378Q304 442 382 442Q436 442 469 415T503 336T465 179T427 52Q427 26 444 26Q450 26 453 27Q482 32 505 65T540 145Q542 153 560 153Q580 153 580 145Q580 144 576 130Q568 101 554 73T508 17T439 -10Q392 -10 371 17T350 73Q350 92 386 193T423 345Q423 404 379 404H374Q288 404 229 303L222 291L189 157Q156 26 151 16Q138 -11 108 -11Q95 -11 87 -5T76 7T74 17Q74 30 112 180T152 343Q153 348 153 366Q153 405 129 405Q91 405 66 305Q60 285 60 284Q58 278 41 278H27Q21 284 21 287Z"></path></g><g data-mml-node="mi" transform="translate(633,-150) scale(0.707)"><path data-c="1D464" d="M580 385Q580 406 599 424T641 443Q659 443 674 425T690 368Q690 339 671 253Q656 197 644 161T609 80T554 12T482 -11Q438 -11 404 5T355 48Q354 47 352 44Q311 -11 252 -11Q226 -11 202 -5T155 14T118 53T104 116Q104 170 138 262T173 379Q173 380 173 381Q173 390 173 393T169 400T158 404H154Q131 404 112 385T82 344T65 302T57 280Q55 278 41 278H27Q21 284 21 287Q21 293 29 315T52 366T96 418T161 441Q204 441 227 416T250 358Q250 340 217 250T184 111Q184 65 205 46T258 26Q301 26 334 87L339 96V119Q339 122 339 128T340 136T341 143T342 152T345 165T348 182T354 206T362 238T373 281Q402 395 406 404Q419 431 449 431Q468 431 475 421T483 402Q483 389 454 274T422 142Q420 131 420 107V100Q420 85 423 71T442 42T487 26Q558 26 600 148Q609 171 620 213T632 273Q632 306 619 325T593 357T580 385Z"></path></g></g><g data-mml-node="mo" transform="translate(3567.3,0) translate(0 -0.5)"><path data-c="7C" d="M139 -249H137Q125 -249 119 -235V251L120 737Q130 750 139 750Q152 750 159 735V-235Q151 -249 141 -249H139Z"></path></g><g data-mml-node="mo" transform="translate(4123.1,0)"><path data-c="3D" d="M56 347Q56 360 70 367H707Q722 359 722 347Q722 336 708 328L390 327H72Q56 332 56 347ZM56 153Q56 168 72 173H708Q722 163 722 153Q722 140 707 133H70Q56 140 56 153Z"></path></g><g data-mml-node="mo" transform="translate(5178.8,0) translate(0 -0.5)"><path data-c="7C" d="M139 -249H137Q125 -249 119 -235V251L120 737Q130 750 139 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678Q415 674 451 396L487 117L510 154Q534 190 574 254T662 394Q837 673 839 675Q840 676 842 678T846 681L852 683H948Q965 683 988 683T1017 684Q1051 684 1051 673Q1051 668 1048 656T1045 643Q1041 637 1008 637Q968 636 957 634T939 623Q936 618 867 340T797 59Q797 55 798 54T805 50T822 48T855 46H886Q892 37 892 35Q892 19 885 5Q880 0 869 0Q864 0 828 1T736 2Q675 2 644 2T609 1Q592 1 592 11Q592 13 594 25Q598 41 602 43T625 46Q652 46 685 49Q699 52 704 61Q706 65 742 207T813 490T848 631L654 322Q458 10 453 5Q451 4 449 3Q444 0 433 0Q418 0 415 7Q413 11 374 317L335 624L267 354Q200 88 200 79Q206 46 272 46H282Q288 41 289 37T286 19Q282 3 278 1Q274 0 267 0Q265 0 255 0T221 1T157 2Q127 2 95 1T58 0Q43 0 39 2T35 11Q35 13 38 25T43 40Q45 46 65 46Q135 46 154 86Q158 92 223 354T289 629Z"></path></g><g data-mml-node="mi" transform="translate(7211.8,0)"><path data-c="1D44E" d="M33 157Q33 258 109 349T280 441Q331 441 370 392Q386 422 416 422Q429 422 439 414T449 394Q449 381 412 234T374 68Q374 43 381 35T402 26Q411 27 422 35Q443 55 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+<li>最大的无符号数值比补码的最大值的两倍大1<br><mjx-container class="MathJax" jax="SVG" display="true"><svg style="vertical-align: -0.357ex;" xmlns="http://www.w3.org/2000/svg" width="23.386ex" height="1.902ex" role="img" focusable="false" viewBox="0 -683 10336.6 840.8"><g stroke="currentColor" fill="currentColor" stroke-width="0" transform="scale(1,-1)"><g data-mml-node="math"><g data-mml-node="mi"><path data-c="1D448" d="M107 637Q73 637 71 641Q70 643 70 649Q70 673 81 682Q83 683 98 683Q139 681 234 681Q268 681 297 681T342 682T362 682Q378 682 378 672Q378 670 376 658Q371 641 366 638H364Q362 638 359 638T352 638T343 637T334 637Q295 636 284 634T266 623Q265 621 238 518T184 302T154 169Q152 155 152 140Q152 86 183 55T269 24Q336 24 403 69T501 205L552 406Q599 598 599 606Q599 633 535 637Q511 637 511 648Q511 650 513 660Q517 676 519 679T529 683Q532 683 561 682T645 680Q696 680 723 681T752 682Q767 682 767 672Q767 650 759 642Q756 637 737 637Q666 633 648 597Q646 592 598 404Q557 235 548 205Q515 105 433 42T263 -22Q171 -22 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414 59T463 140Q466 150 469 151T485 153H489Q504 153 504 145Q504 144 502 134Q486 77 440 33T333 -11Q263 -11 227 52Q186 -10 133 -10H127Q78 -10 57 16T35 71Q35 103 54 123T99 143Q142 143 142 101Q142 81 130 66T107 46T94 41L91 40Q91 39 97 36T113 29T132 26Q168 26 194 71Q203 87 217 139T245 247T261 313Q266 340 266 352Q266 380 251 392T217 404Q177 404 142 372T93 290Q91 281 88 280T72 278H58Q52 284 52 289Z"></path></g><g data-mml-node="mi" transform="translate(605,-150) scale(0.707)"><path data-c="1D464" d="M580 385Q580 406 599 424T641 443Q659 443 674 425T690 368Q690 339 671 253Q656 197 644 161T609 80T554 12T482 -11Q438 -11 404 5T355 48Q354 47 352 44Q311 -11 252 -11Q226 -11 202 -5T155 14T118 53T104 116Q104 170 138 262T173 379Q173 380 173 381Q173 390 173 393T169 400T158 404H154Q131 404 112 385T82 344T65 302T57 280Q55 278 41 278H27Q21 284 21 287Q21 293 29 315T52 366T96 418T161 441Q204 441 227 416T250 358Q250 340 217 250T184 111Q184 65 205 46T258 26Q301 26 334 87L339 96V119Q339 122 339 128T340 136T341 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385Z"></path></g></g><g data-mml-node="mo" transform="translate(8836.4,0)"><path data-c="2B" d="M56 237T56 250T70 270H369V420L370 570Q380 583 389 583Q402 583 409 568V270H707Q722 262 722 250T707 230H409V-68Q401 -82 391 -82H389H387Q375 -82 369 -68V230H70Q56 237 56 250Z"></path></g><g data-mml-node="mn" transform="translate(9836.6,0)"><path data-c="31" d="M213 578L200 573Q186 568 160 563T102 556H83V602H102Q149 604 189 617T245 641T273 663Q275 666 285 666Q294 666 302 660V361L303 61Q310 54 315 52T339 48T401 46H427V0H416Q395 3 257 3Q121 3 100 0H88V46H114Q136 46 152 46T177 47T193 50T201 52T207 57T213 61V578Z"></path></g></g></g></svg></mjx-container></li>
+</ol>
+<p>C语言标准并没有要求要用补码形式来表示有符号整数，但是几乎所有的机器都是这么做的。关于整数数据类型的取值范围和表示，Java标准是非常明确的。</p>
+<blockquote>
+<p>数学角度解释和推导</p>
+</blockquote>
+<p>有符号数的其他表示方法</p>
+<ul>
+<li><strong>反码</strong>（Ones’s Complement）：除了最高有效位的权重是 <mjx-container class="MathJax" jax="SVG"><svg style="vertical-align: -0.791ex;" xmlns="http://www.w3.org/2000/svg" width="12.616ex" height="2.713ex" role="img" focusable="false" viewBox="0 -849.5 5576.1 1199"><g stroke="currentColor" fill="currentColor" stroke-width="0" transform="scale(1,-1)"><g data-mml-node="math"><g data-mml-node="mo"><path data-c="2212" d="M84 237T84 250T98 270H679Q694 262 694 250T679 230H98Q84 237 84 250Z"></path></g><g data-mml-node="mrow" transform="translate(944.7,0)"><g data-mml-node="mo" transform="translate(0 -0.5)"><path data-c="28" d="M152 251Q152 646 388 850H416Q422 844 422 841Q422 837 403 816T357 753T302 649T255 482T236 250Q236 124 255 19T301 -147T356 -251T403 -315T422 -340Q422 -343 416 -349H388Q359 -325 332 -296T271 -213T212 -97T170 56T152 251Z"></path></g><g data-mml-node="msup" transform="translate(458,0)"><g data-mml-node="mn"><path data-c="32" d="M109 429Q82 429 66 447T50 491Q50 562 103 614T235 666Q326 666 387 610T449 465Q449 422 429 383T381 315T301 241Q265 210 201 149L142 93L218 92Q375 92 385 97Q392 99 409 186V189H449V186Q448 183 436 95T421 3V0H50V19V31Q50 38 56 46T86 81Q115 113 136 137Q145 147 170 174T204 211T233 244T261 278T284 308T305 340T320 369T333 401T340 431T343 464Q343 527 309 573T212 619Q179 619 154 602T119 569T109 550Q109 549 114 549Q132 549 151 535T170 489Q170 464 154 447T109 429Z"></path></g><g data-mml-node="TeXAtom" transform="translate(533,363) scale(0.707)" data-mjx-texclass="ORD"><g data-mml-node="mi"><path data-c="1D464" d="M580 385Q580 406 599 424T641 443Q659 443 674 425T690 368Q690 339 671 253Q656 197 644 161T609 80T554 12T482 -11Q438 -11 404 5T355 48Q354 47 352 44Q311 -11 252 -11Q226 -11 202 -5T155 14T118 53T104 116Q104 170 138 262T173 379Q173 380 173 381Q173 390 173 393T169 400T158 404H154Q131 404 112 385T82 344T65 302T57 280Q55 278 41 278H27Q21 284 21 287Q21 293 29 315T52 366T96 418T161 441Q204 441 227 416T250 358Q250 340 217 250T184 111Q184 65 205 46T258 26Q301 26 334 87L339 96V119Q339 122 339 128T340 136T341 143T342 152T345 165T348 182T354 206T362 238T373 281Q402 395 406 404Q419 431 449 431Q468 431 475 421T483 402Q483 389 454 274T422 142Q420 131 420 107V100Q420 85 423 71T442 42T487 26Q558 26 600 148Q609 171 620 213T632 273Q632 306 619 325T593 357T580 385Z"></path></g><g data-mml-node="mo" transform="translate(716,0)"><path data-c="2212" d="M84 237T84 250T98 270H679Q694 262 694 250T679 230H98Q84 237 84 250Z"></path></g><g data-mml-node="mn" transform="translate(1494,0)"><path data-c="31" d="M213 578L200 573Q186 568 160 563T102 556H83V602H102Q149 604 189 617T245 641T273 663Q275 666 285 666Q294 666 302 660V361L303 61Q310 54 315 52T339 48T401 46H427V0H416Q395 3 257 3Q121 3 100 0H88V46H114Q136 46 152 46T177 47T193 50T201 52T207 57T213 61V578Z"></path></g></g></g><g data-mml-node="mo" transform="translate(2673.2,0)"><path data-c="2212" d="M84 237T84 250T98 270H679Q694 262 694 250T679 230H98Q84 237 84 250Z"></path></g><g data-mml-node="mn" transform="translate(3673.4,0)"><path data-c="31" d="M213 578L200 573Q186 568 160 563T102 556H83V602H102Q149 604 189 617T245 641T273 663Q275 666 285 666Q294 666 302 660V361L303 61Q310 54 315 52T339 48T401 46H427V0H416Q395 3 257 3Q121 3 100 0H88V46H114Q136 46 152 46T177 47T193 50T201 52T207 57T213 61V578Z"></path></g><g data-mml-node="mo" transform="translate(4173.4,0) translate(0 -0.5)"><path data-c="29" d="M305 251Q305 -145 69 -349H56Q43 -349 39 -347T35 -338Q37 -333 60 -307T108 -239T160 -136T204 27T221 250T204 473T160 636T108 740T60 807T35 839Q35 850 50 850H56H69Q197 743 256 566Q305 425 305 251Z"></path></g></g></g></g></svg></mjx-container> 而不是 <mjx-container class="MathJax" jax="SVG"><svg style="vertical-align: -0.186ex;" xmlns="http://www.w3.org/2000/svg" width="6.269ex" height="2.072ex" role="img" focusable="false" viewBox="0 -833.9 2771 915.9"><g stroke="currentColor" fill="currentColor" stroke-width="0" transform="scale(1,-1)"><g data-mml-node="math"><g data-mml-node="mo"><path data-c="2212" d="M84 237T84 250T98 270H679Q694 262 694 250T679 230H98Q84 237 84 250Z"></path></g><g data-mml-node="msup" transform="translate(778,0)"><g data-mml-node="mn"><path data-c="32" d="M109 429Q82 429 66 447T50 491Q50 562 103 614T235 666Q326 666 387 610T449 465Q449 422 429 383T381 315T301 241Q265 210 201 149L142 93L218 92Q375 92 385 97Q392 99 409 186V189H449V186Q448 183 436 95T421 3V0H50V19V31Q50 38 56 46T86 81Q115 113 136 137Q145 147 170 174T204 211T233 244T261 278T284 308T305 340T320 369T333 401T340 431T343 464Q343 527 309 573T212 619Q179 619 154 602T119 569T109 550Q109 549 114 549Q132 549 151 535T170 489Q170 464 154 447T109 429Z"></path></g><g data-mml-node="TeXAtom" transform="translate(533,363) scale(0.707)" data-mjx-texclass="ORD"><g data-mml-node="mi"><path data-c="1D464" d="M580 385Q580 406 599 424T641 443Q659 443 674 425T690 368Q690 339 671 253Q656 197 644 161T609 80T554 12T482 -11Q438 -11 404 5T355 48Q354 47 352 44Q311 -11 252 -11Q226 -11 202 -5T155 14T118 53T104 116Q104 170 138 262T173 379Q173 380 173 381Q173 390 173 393T169 400T158 404H154Q131 404 112 385T82 344T65 302T57 280Q55 278 41 278H27Q21 284 21 287Q21 293 29 315T52 366T96 418T161 441Q204 441 227 416T250 358Q250 340 217 250T184 111Q184 65 205 46T258 26Q301 26 334 87L339 96V119Q339 122 339 128T340 136T341 143T342 152T345 165T348 182T354 206T362 238T373 281Q402 395 406 404Q419 431 449 431Q468 431 475 421T483 402Q483 389 454 274T422 142Q420 131 420 107V100Q420 85 423 71T442 42T487 26Q558 26 600 148Q609 171 620 213T632 273Q632 306 619 325T593 357T580 385Z"></path></g><g data-mml-node="mo" transform="translate(716,0)"><path data-c="2212" d="M84 237T84 250T98 270H679Q694 262 694 250T679 230H98Q84 237 84 250Z"></path></g><g data-mml-node="mn" transform="translate(1494,0)"><path data-c="31" d="M213 578L200 573Q186 568 160 563T102 556H83V602H102Q149 604 189 617T245 641T273 663Q275 666 285 666Q294 666 302 660V361L303 61Q310 54 315 52T339 48T401 46H427V0H416Q395 3 257 3Q121 3 100 0H88V46H114Q136 46 152 46T177 47T193 50T201 52T207 57T213 61V578Z"></path></g></g></g></g></g></svg></mjx-container>，它和补码是一样的：<br><mjx-container class="MathJax" jax="SVG" display="true"><svg style="vertical-align: -2.819ex;" xmlns="http://www.w3.org/2000/svg" width="40.019ex" height="6.712ex" role="img" focusable="false" viewBox="0 -1720.9 17688.5 2966.8"><g stroke="currentColor" fill="currentColor" stroke-width="0" transform="scale(1,-1)"><g data-mml-node="math"><g data-mml-node="mi"><path data-c="1D435" d="M231 637Q204 637 199 638T194 649Q194 676 205 682Q206 683 335 683Q594 683 608 681Q671 671 713 636T756 544Q756 480 698 429T565 360L555 357Q619 348 660 311T702 219Q702 146 630 78T453 1Q446 0 242 0Q42 0 39 2Q35 5 35 10Q35 17 37 24Q42 43 47 45Q51 46 62 46H68Q95 46 128 49Q142 52 147 61Q150 65 219 339T288 628Q288 635 231 637ZM649 544Q649 574 634 600T585 634Q578 636 493 637Q473 637 451 637T416 636H403Q388 635 384 626Q382 622 352 506Q352 503 351 500L320 374H401Q482 374 494 376Q554 386 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+<li><strong>原码</strong>（Sign-Magnitude）：最高有效位是符号位，用来确定剩下的位应该取负权还是正权：<br><mjx-container class="MathJax" jax="SVG" display="true"><svg style="vertical-align: -2.827ex;" xmlns="http://www.w3.org/2000/svg" width="31.982ex" height="6.785ex" role="img" focusable="false" viewBox="0 -1749.5 14136.1 2999"><g stroke="currentColor" fill="currentColor" stroke-width="0" transform="scale(1,-1)"><g data-mml-node="math"><g data-mml-node="mi"><path data-c="1D435" d="M231 637Q204 637 199 638T194 649Q194 676 205 682Q206 683 335 683Q594 683 608 681Q671 671 713 636T756 544Q756 480 698 429T565 360L555 357Q619 348 660 311T702 219Q702 146 630 78T453 1Q446 0 242 0Q42 0 39 2Q35 5 35 10Q35 17 37 24Q42 43 47 45Q51 46 62 46H68Q95 46 128 49Q142 52 147 61Q150 65 219 339T288 628Q288 635 231 637ZM649 544Q649 574 634 600T585 634Q578 636 493 637Q473 637 451 637T416 636H403Q388 635 384 626Q382 622 352 506Q352 503 351 500L320 374H401Q482 374 494 376Q554 386 601 434T649 544ZM595 229Q595 273 572 302T512 336Q506 337 429 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10T74 74Q74 91 79 106T122 220Q160 321 166 341T173 380Q173 404 156 404H154Q124 404 99 371T61 287Q60 286 59 284T58 281T56 279T53 278T49 278T41 278H27Q21 284 21 287Z"></path></g><g data-mml-node="mo" transform="translate(345,0)"><path data-c="3D" d="M56 347Q56 360 70 367H707Q722 359 722 347Q722 336 708 328L390 327H72Q56 332 56 347ZM56 153Q56 168 72 173H708Q722 163 722 153Q722 140 707 133H70Q56 140 56 153Z"></path></g><g data-mml-node="mn" transform="translate(1123,0)"><path data-c="30" d="M96 585Q152 666 249 666Q297 666 345 640T423 548Q460 465 460 320Q460 165 417 83Q397 41 362 16T301 -15T250 -22Q224 -22 198 -16T137 16T82 83Q39 165 39 320Q39 494 96 585ZM321 597Q291 629 250 629Q208 629 178 597Q153 571 145 525T137 333Q137 175 145 125T181 46Q209 16 250 16Q290 16 318 46Q347 76 354 130T362 333Q362 478 354 524T321 597Z"></path></g></g><g data-mml-node="TeXAtom" transform="translate(17,1150) scale(0.707)" data-mjx-texclass="ORD"><g data-mml-node="mi"><path data-c="1D464" d="M580 385Q580 406 599 424T641 443Q659 443 674 425T690 368Q690 339 671 253Q656 197 644 161T609 80T554 12T482 -11Q438 -11 404 5T355 48Q354 47 352 44Q311 -11 252 -11Q226 -11 202 -5T155 14T118 53T104 116Q104 170 138 262T173 379Q173 380 173 381Q173 390 173 393T169 400T158 404H154Q131 404 112 385T82 344T65 302T57 280Q55 278 41 278H27Q21 284 21 287Q21 293 29 315T52 366T96 418T161 441Q204 441 227 416T250 358Q250 340 217 250T184 111Q184 65 205 46T258 26Q301 26 334 87L339 96V119Q339 122 339 128T340 136T341 143T342 152T345 165T348 182T354 206T362 238T373 281Q402 395 406 404Q419 431 449 431Q468 431 475 421T483 402Q483 389 454 274T422 142Q420 131 420 107V100Q420 85 423 71T442 42T487 26Q558 26 600 148Q609 171 620 213T632 273Q632 306 619 325T593 357T580 385Z"></path></g><g data-mml-node="mo" transform="translate(716,0)"><path data-c="2212" d="M84 237T84 250T98 270H679Q694 262 694 250T679 230H98Q84 237 84 250Z"></path></g><g data-mml-node="mn" transform="translate(1494,0)"><path data-c="32" d="M109 429Q82 429 66 447T50 491Q50 562 103 614T235 666Q326 666 387 610T449 465Q449 422 429 383T381 315T301 241Q265 210 201 149L142 93L218 92Q375 92 385 97Q392 99 409 186V189H449V186Q448 183 436 95T421 3V0H50V19V31Q50 38 56 46T86 81Q115 113 136 137Q145 147 170 174T204 211T233 244T261 278T284 308T305 340T320 369T333 401T340 431T343 464Q343 527 309 573T212 619Q179 619 154 602T119 569T109 550Q109 549 114 549Q132 549 151 535T170 489Q170 464 154 447T109 429Z"></path></g></g></g><g data-mml-node="msub" transform="translate(2402.7,0)"><g data-mml-node="mi"><path data-c="1D465" d="M52 289Q59 331 106 386T222 442Q257 442 286 424T329 379Q371 442 430 442Q467 442 494 420T522 361Q522 332 508 314T481 292T458 288Q439 288 427 299T415 328Q415 374 465 391Q454 404 425 404Q412 404 406 402Q368 386 350 336Q290 115 290 78Q290 50 306 38T341 26Q378 26 414 59T463 140Q466 150 469 151T485 153H489Q504 153 504 145Q504 144 502 134Q486 77 440 33T333 -11Q263 -11 227 52Q186 -10 133 -10H127Q78 -10 57 16T35 71Q35 103 54 123T99 143Q142 143 142 101Q142 81 130 66T107 46T94 41L91 40Q91 39 97 36T113 29T132 26Q168 26 194 71Q203 87 217 139T245 247T261 313Q266 340 266 352Q266 380 251 392T217 404Q177 404 142 372T93 290Q91 281 88 280T72 278H58Q52 284 52 289Z"></path></g><g data-mml-node="TeXAtom" transform="translate(605,-150) scale(0.707)" data-mjx-texclass="ORD"><g data-mml-node="mi"><path data-c="1D456" d="M184 600Q184 624 203 642T247 661Q265 661 277 649T290 619Q290 596 270 577T226 557Q211 557 198 567T184 600ZM21 287Q21 295 30 318T54 369T98 420T158 442Q197 442 223 419T250 357Q250 340 236 301T196 196T154 83Q149 61 149 51Q149 26 166 26Q175 26 185 29T208 43T235 78T260 137Q263 149 265 151T282 153Q302 153 302 143Q302 135 293 112T268 61T223 11T161 -11Q129 -11 102 10T74 74Q74 91 79 106T122 220Q160 321 166 341T173 380Q173 404 156 404H154Q124 404 99 371T61 287Q60 286 59 284T58 281T56 279T53 278T49 278T41 278H27Q21 284 21 287Z"></path></g></g></g><g data-mml-node="msup" transform="translate(3301.6,0)"><g data-mml-node="mn"><path data-c="32" d="M109 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371T61 287Q60 286 59 284T58 281T56 279T53 278T49 278T41 278H27Q21 284 21 287Z"></path></g></g><g data-mml-node="mo" transform="translate(4128.6,0) translate(0 -0.5)"><path data-c="29" d="M33 1741Q33 1750 51 1750H60H65Q73 1750 81 1743T119 1700Q554 1207 554 251Q554 -707 119 -1199Q76 -1250 66 -1250Q65 -1250 62 -1250T56 -1249Q55 -1249 53 -1249T49 -1250Q33 -1250 33 -1239Q33 -1236 50 -1214T98 -1150T163 -1052T238 -910T311 -727Q443 -335 443 251Q443 402 436 532T405 831T339 1142T224 1438T50 1716Q33 1737 33 1741Z"></path></g></g></g></g></svg></mjx-container></li>
+</ul>
+<p>这两种表示方法都有一个奇怪的属性，就是对于数字 0 有两种不同的编码方式，把 [00…0] 都是解释为 +0，而值 -0 在原码中表示为 [10…0]，在反码中表示为 [11…1]。虽然过去生产过基于反码表示的机器，但是几乎所有的现代机器都使用补码。在浮点数中仍有使用原码编码。</p>
+<blockquote>
+<p>尽管在实际应用中已经存在胜出者，但是了解其他有符号数的表示方式仍有助于理解编码本身。</p>
+</blockquote>
+<p>补码（Two’s Complement）：对于非负数 x，我们用 <mjx-container class="MathJax" jax="SVG"><svg style="vertical-align: -0.186ex;" xmlns="http://www.w3.org/2000/svg" width="6.524ex" height="1.715ex" role="img" focusable="false" viewBox="0 -676.2 2883.7 758.2"><g stroke="currentColor" fill="currentColor" stroke-width="0" transform="scale(1,-1)"><g data-mml-node="math"><g data-mml-node="msup"><g data-mml-node="mn"><path data-c="32" d="M109 429Q82 429 66 447T50 491Q50 562 103 614T235 666Q326 666 387 610T449 465Q449 422 429 383T381 315T301 241Q265 210 201 149L142 93L218 92Q375 92 385 97Q392 99 409 186V189H449V186Q448 183 436 95T421 3V0H50V19V31Q50 38 56 46T86 81Q115 113 136 137Q145 147 170 174T204 211T233 244T261 278T284 308T305 340T320 369T333 401T340 431T343 464Q343 527 309 573T212 619Q179 619 154 602T119 569T109 550Q109 549 114 549Q132 549 151 535T170 489Q170 464 154 447T109 429Z"></path></g><g data-mml-node="mi" transform="translate(533,363) scale(0.707)"><path data-c="1D464" d="M580 385Q580 406 599 424T641 443Q659 443 674 425T690 368Q690 339 671 253Q656 197 644 161T609 80T554 12T482 -11Q438 -11 404 5T355 48Q354 47 352 44Q311 -11 252 -11Q226 -11 202 -5T155 14T118 53T104 116Q104 170 138 262T173 379Q173 380 173 381Q173 390 173 393T169 400T158 404H154Q131 404 112 385T82 344T65 302T57 280Q55 278 41 278H27Q21 284 21 287Q21 293 29 315T52 366T96 418T161 441Q204 441 227 416T250 358Q250 340 217 250T184 111Q184 65 205 46T258 26Q301 26 334 87L339 96V119Q339 122 339 128T340 136T341 143T342 152T345 165T348 182T354 206T362 238T373 281Q402 395 406 404Q419 431 449 431Q468 431 475 421T483 402Q483 389 454 274T422 142Q420 131 420 107V100Q420 85 423 71T442 42T487 26Q558 26 600 148Q609 171 620 213T632 273Q632 306 619 325T593 357T580 385Z"></path></g></g><g data-mml-node="mo" transform="translate(1311.5,0)"><path data-c="2212" d="M84 237T84 250T98 270H679Q694 262 694 250T679 230H98Q84 237 84 250Z"></path></g><g data-mml-node="mi" transform="translate(2311.7,0)"><path data-c="1D465" d="M52 289Q59 331 106 386T222 442Q257 442 286 424T329 379Q371 442 430 442Q467 442 494 420T522 361Q522 332 508 314T481 292T458 288Q439 288 427 299T415 328Q415 374 465 391Q454 404 425 404Q412 404 406 402Q368 386 350 336Q290 115 290 78Q290 50 306 38T341 26Q378 26 414 59T463 140Q466 150 469 151T485 153H489Q504 153 504 145Q504 144 502 134Q486 77 440 33T333 -11Q263 -11 227 52Q186 -10 133 -10H127Q78 -10 57 16T35 71Q35 103 54 123T99 143Q142 143 142 101Q142 81 130 66T107 46T94 41L91 40Q91 39 97 36T113 29T132 26Q168 26 194 71Q203 87 217 139T245 247T261 313Q266 340 266 352Q266 380 251 392T217 404Q177 404 142 372T93 290Q91 281 88 280T72 278H58Q52 284 52 289Z"></path></g></g></g></svg></mjx-container> 来计算 -x 的 w 位表示。<br>反码（Ones’ Complement）用 <mjx-container class="MathJax" jax="SVG"><svg style="vertical-align: -0.566ex;" xmlns="http://www.w3.org/2000/svg" width="13.248ex" height="2.262ex" role="img" focusable="false" viewBox="0 -750 5855.8 1000"><g stroke="currentColor" fill="currentColor" stroke-width="0" transform="scale(1,-1)"><g data-mml-node="math"><g data-mml-node="mrow"><g data-mml-node="mo"><path data-c="5B" d="M118 -250V750H255V710H158V-210H255V-250H118Z"></path></g><g data-mml-node="mn" transform="translate(278,0)"><path data-c="31" d="M213 578L200 573Q186 568 160 563T102 556H83V602H102Q149 604 189 617T245 641T273 663Q275 666 285 666Q294 666 302 660V361L303 61Q310 54 315 52T339 48T401 46H427V0H416Q395 3 257 3Q121 3 100 0H88V46H114Q136 46 152 46T177 47T193 50T201 52T207 57T213 61V578Z"></path><path data-c="31" d="M213 578L200 573Q186 568 160 563T102 556H83V602H102Q149 604 189 617T245 641T273 663Q275 666 285 666Q294 666 302 660V361L303 61Q310 54 315 52T339 48T401 46H427V0H416Q395 3 257 3Q121 3 100 0H88V46H114Q136 46 152 46T177 47T193 50T201 52T207 57T213 61V578Z" transform="translate(500,0)"></path><path data-c="31" d="M213 578L200 573Q186 568 160 563T102 556H83V602H102Q149 604 189 617T245 641T273 663Q275 666 285 666Q294 666 302 660V361L303 61Q310 54 315 52T339 48T401 46H427V0H416Q395 3 257 3Q121 3 100 0H88V46H114Q136 46 152 46T177 47T193 50T201 52T207 57T213 61V578Z" transform="translate(1000,0)"></path></g><g data-mml-node="mo" transform="translate(1944.7,0)"><path data-c="2026" d="M78 60Q78 84 95 102T138 120Q162 120 180 104T199 61Q199 36 182 18T139 0T96 17T78 60ZM525 60Q525 84 542 102T585 120Q609 120 627 104T646 61Q646 36 629 18T586 0T543 17T525 60ZM972 60Q972 84 989 102T1032 120Q1056 120 1074 104T1093 61Q1093 36 1076 18T1033 0T990 17T972 60Z"></path></g><g data-mml-node="mn" transform="translate(3283.3,0)"><path data-c="31" d="M213 578L200 573Q186 568 160 563T102 556H83V602H102Q149 604 189 617T245 641T273 663Q275 666 285 666Q294 666 302 660V361L303 61Q310 54 315 52T339 48T401 46H427V0H416Q395 3 257 3Q121 3 100 0H88V46H114Q136 46 152 46T177 47T193 50T201 52T207 57T213 61V578Z"></path></g><g data-mml-node="mo" transform="translate(3783.3,0)"><path data-c="5D" d="M22 710V750H159V-250H22V-210H119V710H22Z"></path></g></g><g data-mml-node="mo" transform="translate(4283.6,0)"><path data-c="2212" d="M84 237T84 250T98 270H679Q694 262 694 250T679 230H98Q84 237 84 250Z"></path></g><g data-mml-node="mi" transform="translate(5283.8,0)"><path data-c="1D465" d="M52 289Q59 331 106 386T222 442Q257 442 286 424T329 379Q371 442 430 442Q467 442 494 420T522 361Q522 332 508 314T481 292T458 288Q439 288 427 299T415 328Q415 374 465 391Q454 404 425 404Q412 404 406 402Q368 386 350 336Q290 115 290 78Q290 50 306 38T341 26Q378 26 414 59T463 140Q466 150 469 151T485 153H489Q504 153 504 145Q504 144 502 134Q486 77 440 33T333 -11Q263 -11 227 52Q186 -10 133 -10H127Q78 -10 57 16T35 71Q35 103 54 123T99 143Q142 143 142 101Q142 81 130 66T107 46T94 41L91 40Q91 39 97 36T113 29T132 26Q168 26 194 71Q203 87 217 139T245 247T261 313Q266 340 266 352Q266 380 251 392T217 404Q177 404 142 372T93 290Q91 281 88 280T72 278H58Q52 284 52 289Z"></path></g></g></g></svg></mjx-container> 来计算 -x 的反码表示。</p>
+<blockquote>
+<p>了解术语来源比单纯的记忆术语有意思多了！</p>
+</blockquote>
+<h2 id="参考文章"><a href="#参考文章" class="headerlink" title="参考文章"></a>参考文章</h2><ul>
+<li>《深入理解计算机系统》</li>
+</ul>
+]]></content>
+  </entry>
+  <entry>
+    <title>Spring @Configuration 注解的源码分析</title>
+    <url>/2023/11/23/source-code-analysis-of-Spring-Configuration-annotation/</url>
+    <content><![CDATA[<p><code>Configuration</code> 注解是 <code>Spring</code> 中常用的注解，在一般的应用场景中，它用于标识一个类作为配置类，搭配 <code>Bean</code> 注解将创建的 <code>bean</code> 交给 <code>Spring</code> 容器管理。神奇的是，被 <code>Bean</code> 注解标注的方法，只会被真正调用一次。这种方法调用被拦截的情况很容易让人联想到代理，如果你在 <code>Debug</code> 时注意过配置类的实例，你会发现配置类的 <code>Class</code> 名称中携带 <code>EnhancerBySpringCGLIB</code>。本文将从源码角度，分析 <code>Configuration</code> 注解是如何工作的。</p>
+<span id="more"></span>
+
+<h2 id="测试用例"><a href="#测试用例" class="headerlink" title="测试用例"></a>测试用例</h2><ul>
+<li>配置类<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="meta">@Configuration</span></span><br><span class="line"><span class="keyword">public</span> <span class="keyword">class</span> <span class="title class_">BeanConfig</span> &#123;</span><br><span class="line"></span><br><span class="line">    <span class="meta">@Bean</span></span><br><span class="line">    <span class="keyword">public</span> Person <span class="title function_">lisi</span><span class="params">()</span> &#123;</span><br><span class="line">        <span class="keyword">return</span> <span class="keyword">new</span> <span class="title class_">Person</span>(<span class="string">&quot;lisi&quot;</span>, <span class="number">20</span>);</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="meta">@Bean(value = &quot;customName&quot;)</span></span><br><span class="line">    <span class="keyword">public</span> Person <span class="title function_">person</span><span class="params">()</span> &#123;</span><br><span class="line">        <span class="comment">// 测试 lisi() 在配置类拥有注解 @Configuration 时只会真正执行一次</span></span><br><span class="line">        lisi();</span><br><span class="line">        <span class="keyword">return</span> <span class="keyword">new</span> <span class="title class_">Person</span>(<span class="string">&quot;wangwu&quot;</span>, <span class="number">30</span>);</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure></li>
+<li>测试类<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="meta">@Test</span></span><br><span class="line"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title function_">annotationConfigTest</span><span class="params">()</span> &#123;</span><br><span class="line">    <span class="type">ApplicationContext</span> <span class="variable">ac</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">AnnotationConfigApplicationContext</span>(BeanConfig.class);</span><br><span class="line">    <span class="type">BeanConfig</span> <span class="variable">beanConfig</span> <span class="operator">=</span> (BeanConfig) ac.getBean(<span class="string">&quot;beanConfig&quot;</span>);</span><br><span class="line">    <span class="comment">// 即使通过 beanConfig 调用，也不会执行第二次</span></span><br><span class="line">    <span class="type">Person</span> <span class="variable">lisi</span> <span class="operator">=</span> beanConfig.lisi();</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure></li>
+</ul>
+<h2 id="解析配置类"><a href="#解析配置类" class="headerlink" title="解析配置类"></a>解析配置类</h2><h3 id="什么是配置类？"><a href="#什么是配置类？" class="headerlink" title="什么是配置类？"></a>什么是配置类？</h3><p>通常情况下，我们称被 <code>Configuration</code> 注解标注的类为配置类。事实上，配置类的范围比这个定义稍微广泛一些，可以划分为全配置类和精简配置类。在解析配置类时，我们再进一步说明。</p>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="type">ApplicationContext</span> <span class="variable">ac</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">AnnotationConfigApplicationContext</span>(BeanConfig.class);</span><br><span class="line"></span><br><span class="line"><span class="keyword">public</span> <span class="title function_">AnnotationConfigApplicationContext</span><span class="params">(Class&lt;?&gt;... annotatedClasses)</span> &#123;</span><br><span class="line">    <span class="built_in">this</span>();</span><br><span class="line">    <span class="comment">// 注册类，几乎可以说无条件地注册 annotatedClasses 的 bean 定义</span></span><br><span class="line">    register(annotatedClasses);</span><br><span class="line">    refresh();</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<p>本文不详细介绍配置类本身如何注册到 <code>BeanFactory</code> 中。当 <code>BeanConfig</code> 被传递给 <code>AnnotationConfigApplicationContext</code>，自身会先被解析为 <code>BeanDefinition</code> 注册到 <code>beanFactory</code> 中。有两点需要注意：</p>
+<ol>
+<li><code>annotatedClasses</code> 可以传入多个，意味着一开始<strong>静态指定的配置类</strong>可以有多个。</li>
+<li><code>annotatedClasses</code> 除了在命名上提示用户应传入被注解的类外，<code>register(annotatedClasses)</code> 实际上只是将它们视作普通的 <code>Bean</code> 注册到 <code>beanFactory</code> 中。它们是从外界传入的**首批 <code>BeanDefinition</code>**。</li>
+</ol>
+<p>之后 <code>Spring</code> 进入 <code>refresh</code> 流程。使用 <code>IDEA Debug</code> 观察此时的 <code>beanDefinitionMap</code>，除了 <code>beanConfig</code> 外，<code>AnnotationConfigApplicationContext</code> 在创建时，已经自动注册了 <code>6</code> 个 <code>bean</code> 定义，其中一个就是我们今天的主角 <code>org.springframework.context.annotation.internalConfigurationAnnotationProcessor -&gt; org.springframework.context.annotation.ConfigurationClassPostProcessor</code>。显而易见，此时配置类还未被处理得到新的 <code>bean</code> 定义。</p>
+<div style="width:70%;margin:auto"><img src="/2023/11/23/source-code-analysis-of-Spring-Configuration-annotation/Snipaste_2023-11-24_15-26-08.png" class="" title="AnnotationConfigApplicationContext 刷新前的 bean 定义"></div>
+
+<h3 id="配置类后处理器-ConfigurationClassPostProcessor"><a href="#配置类后处理器-ConfigurationClassPostProcessor" class="headerlink" title="配置类后处理器 ConfigurationClassPostProcessor"></a>配置类后处理器 ConfigurationClassPostProcessor</h3><p>配置类后处理器 <code>ConfigurationClassPostProcessor</code> 实现了接口 <code>BeanDefinitionRegistryPostProcessor</code>，也因此同时实现了接口 <code>BeanFactoryPostProcessor</code>。在<a href="/2023/08/04/Spring-application-context-refresh-process/" title="Spring 应用 context 刷新流程">Spring 应用 context 刷新流程</a>中，我们介绍过这两个接口，它们作为工厂后处理器，被用于 <code>refresh</code> 过程的<strong>调用工厂后处理器阶段</strong>（<code>invokeBeanFactoryPostProcessors(beanFactory)</code>）。工厂后处理器的作用，一言以蔽之，允许自定义修改应用上下文中的 bean 定义。</p>
+<p>配置类后处理器 <code>ConfigurationClassPostProcessor</code> 的具体作用可以概括为两点：</p>
+<ol>
+<li>解析配置类中配置的 <code>Bean</code>，将它们的 <code>bean</code> 定义注册到 <code>BeanFactory</code> 中。</li>
+<li>（如有必要）增强配置类</li>
+</ol>
+<h3 id="处理配置类的核心方法-processConfigBeanDefinitions"><a href="#处理配置类的核心方法-processConfigBeanDefinitions" class="headerlink" title="处理配置类的核心方法 processConfigBeanDefinitions"></a>处理配置类的核心方法 processConfigBeanDefinitions</h3><p>根据之前的介绍，进入 <code>invokeBeanFactoryPostProcessors(beanFactory)</code>，<code>ConfigurationClassPostProcessor</code> 会先作为 <code>BeanDefinitionRegistryPostProcessor</code> 被调用。</p>
 <blockquote>
-<p>可以通过 <code>vim ~/.vimrc</code> 修改配置文件。</p>
+<p>个人的理解是，先将 <code>BeanFactory</code> 视作 <code>BeanDefinitionRegistry</code> 注册好 <code>BeanDefinition</code>，再视作 <code>BeanFactory</code> 进行处理，有点预备好原材料再统一处理的意思。</p>
 </blockquote>
-<h2 id="参考文章"><a href="#参考文章" class="headerlink" title="参考文章"></a>参考文章</h2><ul>
-<li><a href="https://linux.vbird.org/linux_basic/centos7/0310vi.php">vim 程式編輯器</a></li>
-<li><a href="https://linux.cn/article-8144-1.html">Vim 快捷键速查表</a></li>
-<li><a href="https://www.ruanyifeng.com/blog/2018/09/vimrc.html">Vim 配置入门</a></li>
-</ul>
-]]></content>
-      <tags>
-        <tag>linux</tag>
-        <tag>vim</tag>
-      </tags>
-  </entry>
-  <entry>
-    <title>k3s 的安装和使用</title>
-    <url>/2024/01/30/installation-and-use-of-k3s/</url>
-    <content><![CDATA[<p>本文记录了 <code>k3s</code> 的安装和使用，相较于 <code>minikube</code>，前者是一个完全兼容的 <code>Kubernetes</code> 发行版，安装和使用的体验更佳。</p>
-<span id="more"></span>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="meta">@Override</span></span><br><span class="line"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title function_">postProcessBeanDefinitionRegistry</span><span class="params">(BeanDefinitionRegistry registry)</span> &#123;</span><br><span class="line">    <span class="comment">// ...</span></span><br><span class="line">    <span class="comment">// 处理配置的 BeanDefinition</span></span><br><span class="line">    processConfigBeanDefinitions(registry);</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
 
-<h2 id="安装"><a href="#安装" class="headerlink" title="安装"></a>安装</h2><blockquote>
-<p>参考官方文档-<a href="https://docs.k3s.io/zh/quick-start">快速入门指南</a>，使用默认选项启动集群非常简单方便！！！</p>
+<blockquote>
+<p>核心方法 <code>processConfigBeanDefinitions(registry)</code> 冗长，个人建议无需过度关注细节（但同时个人感受是反复阅读和 <code>Debug</code> 确实有益于加深理解，看个人时间和精力）。</p>
 </blockquote>
-<h3 id="步骤"><a href="#步骤" class="headerlink" title="步骤"></a>步骤</h3><ol>
-<li>获取并运行 <code>k3s</code> 安装脚本。官方为中国用户提供了镜像加速支持。<figure class="highlight text"><table><tr><td class="code"><pre><span class="line">$ curl -sfL https://rancher-mirror.rancher.cn/k3s/k3s-install.sh | INSTALL_K3S_MIRROR=cn sh -                                </span><br><span class="line">[sudo] password for moralok:                                                                                                                        </span><br><span class="line">[INFO]  Finding release for channel stable                                                                                                        </span><br><span class="line">[INFO]  Using v1.28.5+k3s1 as release                                                                                                             </span><br><span class="line">[INFO]  Downloading hash rancher-mirror.rancher.cn/k3s/v1.28.5-k3s1/sha256sum-amd64.txt                                                           </span><br><span class="line">[INFO]  Downloading binary rancher-mirror.rancher.cn/k3s/v1.28.5-k3s1/k3s                                                                         </span><br><span class="line">[INFO]  Verifying binary download                                                                                                                 </span><br><span class="line">[INFO]  Installing k3s to /usr/local/bin/k3s                                                                                                      </span><br><span class="line">[INFO]  Skipping installation of SELinux RPM                                                                                                      </span><br><span class="line">[INFO]  Creating /usr/local/bin/kubectl symlink to k3s                                                                                            </span><br><span class="line">[INFO]  Creating /usr/local/bin/crictl symlink to k3s                                                                                             </span><br><span class="line">[INFO]  Skipping /usr/local/bin/ctr symlink to k3s, command exists in PATH at /usr/bin/ctr                                                        </span><br><span class="line">[INFO]  Creating killall script /usr/local/bin/k3s-killall.sh                                                                                     </span><br><span class="line">[INFO]  Creating uninstall script /usr/local/bin/k3s-uninstall.sh                                                                                 </span><br><span class="line">[INFO]  env: Creating environment file /etc/systemd/system/k3s.service.env                                                                        </span><br><span class="line">[INFO]  systemd: Creating service file /etc/systemd/system/k3s.service                                                                            </span><br><span class="line">sh: 1014: restorecon: not found                                                                                                                   </span><br><span class="line">sh: 1015: restorecon: not found                                                                                                                   </span><br><span class="line">[INFO]  systemd: Enabling k3s unit                                                                                                                </span><br><span class="line">Created symlink /etc/systemd/system/multi-user.target.wants/k3s.service → /etc/systemd/system/k3s.service.                                        </span><br><span class="line">[INFO]  systemd: Starting k3s</span><br></pre></td></tr></table></figure></li>
-<li>可以通过使用 <code>kubectl</code> 确认安装成功。刚安装的时候使用 <code>kubectl</code> 需要 <code>root</code> 权限。<figure class="highlight text"><table><tr><td class="code"><pre><span class="line">$ sudo kubectl get node</span><br><span class="line">NAME            STATUS   ROLES                  AGE   VERSION</span><br><span class="line">ubuntu-server   Ready    control-plane,master   52m   v1.28.5+k3s1</span><br></pre></td></tr></table></figure></li>
-<li>实际上安装的就是一个 <code>k3s</code> 可执行文件，<code>kubectl</code> 和 <code>crictl</code> 只是软链接，指向 <code>k3s</code>。<figure class="highlight text"><table><tr><td class="code"><pre><span class="line">$ ls /usr/local/bin/</span><br><span class="line">crictl  k3s  k3s-killall.sh  k3s-uninstall.sh  kubectl</span><br></pre></td></tr></table></figure></li>
+<p>基于配置类的 <code>BeanDefinition Registry</code>（也就是 <code>BeanFactory</code>），获取配置类，构建和校验配置模型：</p>
+<ol>
+<li>从 <code>BeanDefinition Registry</code>（即 <code>BeanFactory</code>）中查找配置类。</li>
+<li>解析配置类得到<strong>配置模型</strong>，从模型中读取 <code>BeanDefinitions</code> 注册到 <code>BeanDefinition Registry</code>。</li>
+<li>新的 <code>BeanDefinitions</code> 可能有新的配置类，回到 <code>1</code> 再来一遍。重复循环直到不再引入新的配置类。</li>
 </ol>
+<p>以本文示例进行说明，静态添加的配置类只有 <code>BeanConfig</code>，假如 <code>BeanConfig</code> 不仅被 <code>Configuration</code> 注解标注，还被 <code>ComponentScan</code> 注解标注，并且刚好 <code>Spring</code> 通过扫描获得并添加了新的配置类，那么新的配置类就需要继续被解析。</p>
 <blockquote>
-<p>安装的信息中显示了 <code>k3s</code> 的 <code>service file</code> 和 <code>environment file</code> 的路径，后续修改启动参数和环境变量需要用到。</p>
+<p>应正视<strong>配置模型</strong>这个概念，它可以理解为配置类到 <code>BeanDefinitions</code> 的中间产物。最初我先入为主，带着<code>解析得到 BeanDefinitions</code> 这样“一阶段”完成的观念，非常不理解 <code>processConfigBeanDefinitions</code> 方法上 <code>Build and validate a configuration model based on the registry of Configuration classes</code> 这句注释。先行强调注意，<strong>处理配置类得到 <code>bean</code> 定义分为“两阶段”，解析配置类得到配置模型，从配置模型中读取 <code>bean</code> 定义</strong>。</p>
 </blockquote>
-<h3 id="配置文件权限问题"><a href="#配置文件权限问题" class="headerlink" title="配置文件权限问题"></a>配置文件权限问题</h3><p>在刚安装完 <code>k3s</code> 的时候，使用 <code>kubectl</code> 需要 <code>root</code> 权限。根据报错信息可知，是因为非 <code>root</code> 用户无法读取配置文件 <code>/etc/rancher/k3s/k3s.yaml</code>。</p>
-<figure class="highlight text"><table><tr><td class="code"><pre><span class="line">$ kubectl get node                                                                                                                                            </span><br><span class="line">WARN[0000] Unable to read /etc/rancher/k3s/k3s.yaml, please start server with --write-kubeconfig-mode to modify kube config permissions           </span><br><span class="line">error: error loading config file &quot;/etc/rancher/k3s/k3s.yaml&quot;: open /etc/rancher/k3s/k3s.yaml: permission denied</span><br></pre></td></tr></table></figure>
+<div style="width:60%;margin:auto"><img src="/2023/11/23/source-code-analysis-of-Spring-Configuration-annotation/Pasted%20image%2020231127205117.png" class="" title="处理配置类的过程"></div>
 
-<p>查看配置文件的信息可知其权限配置为 <code>600</code>，只有 <code>root</code> 用户具有读写权限。</p>
-<figure class="highlight text"><table><tr><td class="code"><pre><span class="line">$ ll /etc/rancher/k3s/k3s.yaml                                                                                               </span><br><span class="line">-rw------- 1 root root 2961 Jan 30 18:58 /etc/rancher/k3s/k3s.yaml</span><br></pre></td></tr></table></figure>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title function_">processConfigBeanDefinitions</span><span class="params">(BeanDefinitionRegistry registry)</span> &#123;</span><br><span class="line">    List&lt;BeanDefinitionHolder&gt; configCandidates = <span class="keyword">new</span> <span class="title class_">ArrayList</span>&lt;BeanDefinitionHolder&gt;();</span><br><span class="line">    <span class="comment">// 刚开始，获取全部的 BeanDefinitions 作为候选</span></span><br><span class="line">    String[] candidateNames = registry.getBeanDefinitionNames();</span><br><span class="line"></span><br><span class="line">    <span class="keyword">for</span> (String beanName : candidateNames) &#123;</span><br><span class="line">        <span class="type">BeanDefinition</span> <span class="variable">beanDef</span> <span class="operator">=</span> registry.getBeanDefinition(beanName);</span><br><span class="line">        <span class="keyword">if</span> (ConfigurationClassUtils.isFullConfigurationClass(beanDef) ||</span><br><span class="line">                ConfigurationClassUtils.isLiteConfigurationClass(beanDef)) &#123;</span><br><span class="line">            <span class="comment">// 根据 beanDef 的 attributes 判断是 Full 还是 Lite 的配置类</span></span><br><span class="line">            <span class="comment">// 已经处理过的配置类，会在 attributes 中添加标识</span></span><br><span class="line">            <span class="keyword">if</span> (logger.isDebugEnabled()) &#123;</span><br><span class="line">                logger.debug(<span class="string">&quot;Bean definition has already been processed as a configuration class: &quot;</span> + beanDef);</span><br><span class="line">            &#125;</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="keyword">else</span> <span class="keyword">if</span> (ConfigurationClassUtils.checkConfigurationClassCandidate(beanDef, <span class="built_in">this</span>.metadataReaderFactory)) &#123;</span><br><span class="line">            <span class="comment">// 未处理过的候选者，检查是否是配置类。</span></span><br><span class="line">            <span class="comment">// configCandidates 的命名让人有些困惑，个人认为这里指代的就是配置类</span></span><br><span class="line">            configCandidates.add(<span class="keyword">new</span> <span class="title class_">BeanDefinitionHolder</span>(beanDef, beanName));</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// Return immediately if no @Configuration classes were found</span></span><br><span class="line">    <span class="comment">// 和注释略有不符，配置类的判定没有这么单一，不仅限于 @Configuration 注解的 Full 配置类</span></span><br><span class="line">    <span class="keyword">if</span> (configCandidates.isEmpty()) &#123;</span><br><span class="line">        <span class="keyword">return</span>;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 根据 attributes 中的 order 排序（来源于 @Order 注解，可能不存在）</span></span><br><span class="line">    Collections.sort(configCandidates, <span class="keyword">new</span> <span class="title class_">Comparator</span>&lt;BeanDefinitionHolder&gt;() &#123;</span><br><span class="line">        <span class="meta">@Override</span></span><br><span class="line">        <span class="keyword">public</span> <span class="type">int</span> <span class="title function_">compare</span><span class="params">(BeanDefinitionHolder bd1, BeanDefinitionHolder bd2)</span> &#123;</span><br><span class="line">            <span class="type">int</span> <span class="variable">i1</span> <span class="operator">=</span> ConfigurationClassUtils.getOrder(bd1.getBeanDefinition());</span><br><span class="line">            <span class="type">int</span> <span class="variable">i2</span> <span class="operator">=</span> ConfigurationClassUtils.getOrder(bd2.getBeanDefinition());</span><br><span class="line">            <span class="keyword">return</span> (i1 &lt; i2) ? -<span class="number">1</span> : (i1 &gt; i2) ? <span class="number">1</span> : <span class="number">0</span>;</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;);</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 检测应用上下文中是否配置了自定义 bean 名称生成策略</span></span><br><span class="line">    <span class="type">SingletonBeanRegistry</span> <span class="variable">sbr</span> <span class="operator">=</span> <span class="literal">null</span>;</span><br><span class="line">    <span class="keyword">if</span> (registry <span class="keyword">instanceof</span> SingletonBeanRegistry) &#123;</span><br><span class="line">        sbr = (SingletonBeanRegistry) registry;</span><br><span class="line">        <span class="keyword">if</span> (!<span class="built_in">this</span>.localBeanNameGeneratorSet &amp;&amp; sbr.containsSingleton(CONFIGURATION_BEAN_NAME_GENERATOR)) &#123;</span><br><span class="line">            <span class="comment">// 如果 localBeanNameGenerator 未设置，且 SingletonBeanRegistry 中存在，就获取并使用</span></span><br><span class="line">            <span class="type">BeanNameGenerator</span> <span class="variable">generator</span> <span class="operator">=</span> (BeanNameGenerator) sbr.getSingleton(CONFIGURATION_BEAN_NAME_GENERATOR);</span><br><span class="line">            <span class="built_in">this</span>.componentScanBeanNameGenerator = generator;</span><br><span class="line">            <span class="built_in">this</span>.importBeanNameGenerator = generator;</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 创建 ConfigurationClassParser，解析每一个配置类（不限于 Full 类型）</span></span><br><span class="line">    <span class="type">ConfigurationClassParser</span> <span class="variable">parser</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">ConfigurationClassParser</span>(</span><br><span class="line">            <span class="built_in">this</span>.metadataReaderFactory, <span class="built_in">this</span>.problemReporter, <span class="built_in">this</span>.environment,</span><br><span class="line">            <span class="built_in">this</span>.resourceLoader, <span class="built_in">this</span>.componentScanBeanNameGenerator, registry);</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 配置类候选</span></span><br><span class="line">    Set&lt;BeanDefinitionHolder&gt; candidates = <span class="keyword">new</span> <span class="title class_">LinkedHashSet</span>&lt;BeanDefinitionHolder&gt;(configCandidates);</span><br><span class="line">    <span class="comment">// 处理过的配置模型，已经被读取过 Bean 定义</span></span><br><span class="line">    <span class="comment">// 个人感觉命名为 alreadyRead 更为准确</span></span><br><span class="line">    Set&lt;ConfigurationClass&gt; alreadyParsed = <span class="keyword">new</span> <span class="title class_">HashSet</span>&lt;ConfigurationClass&gt;(configCandidates.size());</span><br><span class="line">    <span class="keyword">do</span> &#123;</span><br><span class="line">        <span class="comment">// 解析</span></span><br><span class="line">        parser.parse(candidates);</span><br><span class="line">        <span class="comment">// 校验</span></span><br><span class="line">        parser.validate();</span><br><span class="line"></span><br><span class="line">        <span class="comment">// 从 parser 中获取 ConfigurationClass，这就是配置模型（忍不住吐槽一下这个命名和配置类好容易搞混）</span></span><br><span class="line">        Set&lt;ConfigurationClass&gt; configClasses = <span class="keyword">new</span> <span class="title class_">LinkedHashSet</span>&lt;ConfigurationClass&gt;(parser.getConfigurationClasses());</span><br><span class="line">        <span class="comment">// 排除已经读取过 Bean 定义的 ConfigurationClass</span></span><br><span class="line">        configClasses.removeAll(alreadyParsed);</span><br><span class="line"></span><br><span class="line">        <span class="comment">// Read the model and create bean definitions based on its content</span></span><br><span class="line">        <span class="comment">// 读取模型并根据它的内容创建 BeanDefinitions</span></span><br><span class="line">        <span class="keyword">if</span> (<span class="built_in">this</span>.reader == <span class="literal">null</span>) &#123;</span><br><span class="line">            <span class="built_in">this</span>.reader = <span class="keyword">new</span> <span class="title class_">ConfigurationClassBeanDefinitionReader</span>(</span><br><span class="line">                    registry, <span class="built_in">this</span>.sourceExtractor, <span class="built_in">this</span>.resourceLoader, <span class="built_in">this</span>.environment,</span><br><span class="line">                    <span class="built_in">this</span>.importBeanNameGenerator, parser.getImportRegistry());</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="comment">// 加载（读取并注册） BeanDefinitions</span></span><br><span class="line">        <span class="built_in">this</span>.reader.loadBeanDefinitions(configClasses);</span><br><span class="line">        <span class="comment">// 添加到已经读取过的配置模型集合中（上面的 configClasses.removeAll(alreadyParsed) 造成的干扰好大）</span></span><br><span class="line">        alreadyParsed.addAll(configClasses);</span><br><span class="line"></span><br><span class="line">        <span class="comment">// 清空这一轮处理的配置类集合</span></span><br><span class="line">        candidates.clear();</span><br><span class="line">        <span class="comment">// 通过 registry 中的 BeanDefinitions 数量判断是否有新增的 BeanDefinitions</span></span><br><span class="line">        <span class="keyword">if</span> (registry.getBeanDefinitionCount() &gt; candidateNames.length) &#123;</span><br><span class="line">            <span class="comment">// 重新获取全部 BeanDefinitions 作为候选</span></span><br><span class="line">            String[] newCandidateNames = registry.getBeanDefinitionNames();</span><br><span class="line">            <span class="comment">// 保留旧的候选集合用于快速筛选</span></span><br><span class="line">            Set&lt;String&gt; oldCandidateNames = <span class="keyword">new</span> <span class="title class_">HashSet</span>&lt;String&gt;(Arrays.asList(candidateNames));</span><br><span class="line">            <span class="comment">// 为什么 alreadyParsedClasses 不定义在循环外，需要每次动态地从 alreadyParsed 获取？难道 configurationClass.getMetadata().getClassName() 的结果会变化吗？</span></span><br><span class="line">            <span class="comment">// 如果不存在上述情况，直接在添加到 alreadyParsed 时，添加到 alreadyParsedClasses 就好了呀？</span></span><br><span class="line">            Set&lt;String&gt; alreadyParsedClasses = <span class="keyword">new</span> <span class="title class_">HashSet</span>&lt;String&gt;();</span><br><span class="line">            <span class="keyword">for</span> (ConfigurationClass configurationClass : alreadyParsed) &#123;</span><br><span class="line">                alreadyParsedClasses.add(configurationClass.getMetadata().getClassName());</span><br><span class="line">            &#125;</span><br><span class="line">            <span class="keyword">for</span> (String candidateName : newCandidateNames) &#123;</span><br><span class="line">                <span class="comment">// 快速地排除旧候选</span></span><br><span class="line">                <span class="keyword">if</span> (!oldCandidateNames.contains(candidateName)) &#123;</span><br><span class="line">                    <span class="type">BeanDefinition</span> <span class="variable">bd</span> <span class="operator">=</span> registry.getBeanDefinition(candidateName);</span><br><span class="line">                    <span class="comment">// 检查是否是配置类并且未被解析过（比如同一个配置类，重复注册，无需多次处理）</span></span><br><span class="line">                    <span class="keyword">if</span> (ConfigurationClassUtils.checkConfigurationClassCandidate(bd, <span class="built_in">this</span>.metadataReaderFactory) &amp;&amp;</span><br><span class="line">                            !alreadyParsedClasses.contains(bd.getBeanClassName())) &#123;</span><br><span class="line">                        <span class="comment">// 添加到新的配置类集合</span></span><br><span class="line">                        candidates.add(<span class="keyword">new</span> <span class="title class_">BeanDefinitionHolder</span>(bd, candidateName));</span><br><span class="line">                    &#125;</span><br><span class="line">                &#125;</span><br><span class="line">            &#125;</span><br><span class="line">            candidateNames = newCandidateNames;</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="keyword">while</span> (!candidates.isEmpty());</span><br><span class="line"></span><br><span class="line">    <span class="comment">// Register the ImportRegistry as a bean in order to support ImportAware @Configuration classes</span></span><br><span class="line">    <span class="keyword">if</span> (sbr != <span class="literal">null</span>) &#123;</span><br><span class="line">        <span class="keyword">if</span> (!sbr.containsSingleton(IMPORT_REGISTRY_BEAN_NAME)) &#123;</span><br><span class="line">            sbr.registerSingleton(IMPORT_REGISTRY_BEAN_NAME, parser.getImportRegistry());</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 清理 metadataReaderFactory 缓存</span></span><br><span class="line">    <span class="keyword">if</span> (<span class="built_in">this</span>.metadataReaderFactory <span class="keyword">instanceof</span> CachingMetadataReaderFactory) &#123;</span><br><span class="line">        ((CachingMetadataReaderFactory) <span class="built_in">this</span>.metadataReaderFactory).clearCache();</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
 
-<p>一般来说，我们希望能够通过非 <code>root</code> 用户使用 <code>kubectl</code>，避免通过 <code>root</code> 用户或者通过 <code>sudo</code> 加输入密码的形式来使用 <code>kubectl</code>。那么如何解决这个问题呢？本质上这是一个 <code>Linux</code> 的文件权限问题，似乎修改文件的权限配置就可以解决。但是提示信息给出的解决方案并不是那么直接，它告诉我们通过修改 <code>k3s server</code> 的启动参数来达到修改配置文件权限的目的。这是因为 <code>k3s</code> 服务在每次重启时会根据启动参数和环境变量重置配置文件 <code>/etc/rancher/k3s/k3s.yaml</code>，手动修改文件的权限配置并不能优雅地解决这个问题，一旦服务重启，修改就会丢失。</p>
+<h3 id="判断是否是配置类"><a href="#判断是否是配置类" class="headerlink" title="判断是否是配置类"></a>判断是否是配置类</h3><p><code>checkConfigurationClassCandidate</code> 方法：</p>
+<ol>
+<li>不能 <code>className</code> 为 <code>null</code> 或 <code>Bean</code> 定义拥有工厂方法</li>
+<li>被 <code>Configuration</code> 注解标注（全配置类）</li>
+<li>被 <code>Component</code>、<code>ComponentScan</code>、<code>Import</code>、<code>ImportResource</code> 注解标注或者拥有被 <code>Bean</code> 注解标注的方法</li>
+<li>设置 <code>order</code> 用于排序</li>
+</ol>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">static</span> <span class="type">boolean</span> <span class="title function_">checkConfigurationClassCandidate</span><span class="params">(BeanDefinition beanDef, MetadataReaderFactory metadataReaderFactory)</span> &#123;</span><br><span class="line">    <span class="type">String</span> <span class="variable">className</span> <span class="operator">=</span> beanDef.getBeanClassName();</span><br><span class="line">    <span class="keyword">if</span> (className == <span class="literal">null</span> || beanDef.getFactoryMethodName() != <span class="literal">null</span>) &#123;</span><br><span class="line">        <span class="comment">// 如果 className 为 null，或者拥有工厂方法，返回 false</span></span><br><span class="line">        <span class="comment">// 举例，被 @Bean 注解的方法返回的 Bean，它的类即使被 @Configuration 注解，也不属于配置类</span></span><br><span class="line">        <span class="keyword">return</span> <span class="literal">false</span>;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 获取 AnnotationMetadata</span></span><br><span class="line">    <span class="comment">// 这些分支对应的场景？</span></span><br><span class="line">    AnnotationMetadata metadata;</span><br><span class="line">    <span class="keyword">if</span> (beanDef <span class="keyword">instanceof</span> AnnotatedBeanDefinition &amp;&amp;</span><br><span class="line">            className.equals(((AnnotatedBeanDefinition) beanDef).getMetadata().getClassName())) &#123;</span><br><span class="line">        <span class="comment">// 可以复用 BeanDefinition 中已经解析过的 metadata</span></span><br><span class="line">        metadata = ((AnnotatedBeanDefinition) beanDef).getMetadata();</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="keyword">else</span> <span class="keyword">if</span> (beanDef <span class="keyword">instanceof</span> AbstractBeanDefinition &amp;&amp; ((AbstractBeanDefinition) beanDef).hasBeanClass()) &#123;</span><br><span class="line">        <span class="comment">// 检查是否存在已经加载的 Class，因为我们可能甚至无法加载该类的类文件</span></span><br><span class="line">        <span class="comment">// 创建 metadata 看起来也没干什么事情呀</span></span><br><span class="line">        Class&lt;?&gt; beanClass = ((AbstractBeanDefinition) beanDef).getBeanClass();</span><br><span class="line">        metadata = <span class="keyword">new</span> <span class="title class_">StandardAnnotationMetadata</span>(beanClass, <span class="literal">true</span>);</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="keyword">else</span> &#123;</span><br><span class="line">        <span class="comment">// 第二个分支提到的无法加载类文件的情况是指这里吗？</span></span><br><span class="line">        <span class="keyword">try</span> &#123;</span><br><span class="line">            <span class="type">MetadataReader</span> <span class="variable">metadataReader</span> <span class="operator">=</span> metadataReaderFactory.getMetadataReader(className);</span><br><span class="line">            metadata = metadataReader.getAnnotationMetadata();</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="keyword">catch</span> (IOException ex) &#123;</span><br><span class="line">            <span class="keyword">if</span> (logger.isDebugEnabled()) &#123;</span><br><span class="line">                logger.debug(<span class="string">&quot;Could not find class file for introspecting configuration annotations: &quot;</span> + className, ex);</span><br><span class="line">            &#125;</span><br><span class="line">            <span class="keyword">return</span> <span class="literal">false</span>;</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">if</span> (isFullConfigurationCandidate(metadata)) &#123;</span><br><span class="line">        <span class="comment">// 属于 Full 配置类，添加 Attribute 标记，标识已处理过</span></span><br><span class="line">        beanDef.setAttribute(CONFIGURATION_CLASS_ATTRIBUTE, CONFIGURATION_CLASS_FULL);</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="keyword">else</span> <span class="keyword">if</span> (isLiteConfigurationCandidate(metadata)) &#123;</span><br><span class="line">        <span class="comment">// 属于 Lite 配置类，添加 Attribute 标记，标识已处理过</span></span><br><span class="line">        beanDef.setAttribute(CONFIGURATION_CLASS_ATTRIBUTE, CONFIGURATION_CLASS_LITE);</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="keyword">else</span> &#123;</span><br><span class="line">        <span class="keyword">return</span> <span class="literal">false</span>;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 不管是 Full 还是 Lite 配置类，检查是否被 @Order 注解，如果有则设置到 Attribute，用于排序</span></span><br><span class="line">    Map&lt;String, Object&gt; orderAttributes = metadata.getAnnotationAttributes(Order.class.getName());</span><br><span class="line">    <span class="keyword">if</span> (orderAttributes != <span class="literal">null</span>) &#123;</span><br><span class="line">        beanDef.setAttribute(ORDER_ATTRIBUTE, orderAttributes.get(AnnotationUtils.VALUE));</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">return</span> <span class="literal">true</span>;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<h4 id="判断是否属于-Full-配置类"><a href="#判断是否属于-Full-配置类" class="headerlink" title="判断是否属于 Full 配置类"></a>判断是否属于 Full 配置类</h4><ol>
+<li>被 <code>Configuration</code> 注解标注</li>
+</ol>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">static</span> <span class="type">boolean</span> <span class="title function_">isFullConfigurationCandidate</span><span class="params">(AnnotationMetadata metadata)</span> &#123;</span><br><span class="line">    <span class="keyword">return</span> metadata.isAnnotated(Configuration.class.getName());</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<h4 id="判断是否属于-Lite-配置类"><a href="#判断是否属于-Lite-配置类" class="headerlink" title="判断是否属于 Lite 配置类"></a>判断是否属于 Lite 配置类</h4><ol>
+<li>被 <code>Component</code>、<code>ComponentScan</code>、<code>Import</code>、<code>ImportResource</code> 注解标注</li>
+<li>拥有被 <code>Bean</code> 注解标注的方法</li>
+</ol>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">static</span> <span class="type">boolean</span> <span class="title function_">isLiteConfigurationCandidate</span><span class="params">(AnnotationMetadata metadata)</span> &#123;</span><br><span class="line">    <span class="comment">// 接口和注解，直接返回 false</span></span><br><span class="line">    <span class="keyword">if</span> (metadata.isInterface()) &#123;</span><br><span class="line">        <span class="keyword">return</span> <span class="literal">false</span>;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 如果被 @Component、@ComponentScan、@Import、@ImportResource 注解</span></span><br><span class="line">    <span class="keyword">for</span> (String indicator : candidateIndicators) &#123;</span><br><span class="line">        <span class="keyword">if</span> (metadata.isAnnotated(indicator)) &#123;</span><br><span class="line">            <span class="keyword">return</span> <span class="literal">true</span>;</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 拥有被 @Bean 注解的方法</span></span><br><span class="line">    <span class="keyword">try</span> &#123;</span><br><span class="line">        <span class="keyword">return</span> metadata.hasAnnotatedMethods(Bean.class.getName());</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="keyword">catch</span> (Throwable ex) &#123;</span><br><span class="line">        <span class="keyword">if</span> (logger.isDebugEnabled()) &#123;</span><br><span class="line">            logger.debug(<span class="string">&quot;Failed to introspect @Bean methods on class [&quot;</span> + metadata.getClassName() + <span class="string">&quot;]: &quot;</span> + ex);</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="keyword">return</span> <span class="literal">false</span>;</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<h3 id="循环处理直至没有新增配置类"><a href="#循环处理直至没有新增配置类" class="headerlink" title="循环处理直至没有新增配置类"></a>循环处理直至没有新增配置类</h3><p>循环处理部分的代码有点难阅读。</p>
+<ul>
+<li>首先是因为命名比较相似，需要理清各个变量的含义和作用<ul>
+<li><code>candidateNames</code> 就是普普通通的纯候选者（全部 <code>BeanDefinitions</code>），每次循环在解析完，加载 <code>BeanDefinitions</code> 后可能会新增</li>
+<li><code>configCandidates</code>（<code>candidates</code>） 就是符合配置类条件的配置类。虽然命名带 <code>Candidates</code>，其实已经是正牌，并非候选。感觉 <code>configClass</code> 更容易理解，但该变量名另作他用。有新增就要继续循环</li>
+<li><code>configClass</code>（<code>ConfigurationClass</code> 类） 是经过解析的配置模型，不要和配置类搞混了。后面出现过 <code>ConfigurationModel</code>，感觉该命名更加准确</li>
+</ul>
+</li>
+<li>其次是因为对黑盒 parser 的作用不了解，个人经验如果完全将 <code>parser</code> 当作黑盒对待，不了解解析过程、解析的返回结果以及如何处理返回结果，理解循环解析的过程时会有点困难<ul>
+<li><code>parser.parse(candidates)</code> 解析配置类构建得到配置模型（<code>ConfigurationClass</code>）。以副作用的形式进行处理，传入 <code>ConfigurationClass</code>，返回 <code>ConfigurationClass</code></li>
+<li><code>this.reader.loadBeanDefinitions(configClasses)</code> 从配置模型（<code>ConfigurationClass</code>）中加载 <code>BeanDefinitions</code></li>
+</ul>
+</li>
+</ul>
 <blockquote>
-<p><a href="https://github.com/k3s-io/k3s/discussions/7278">k3s 的 Github Discussions</a> 中讨论了这个问题，并链接了文档 <a href="https://docs.k3s.io/zh/cli/server#%E7%AE%A1%E7%90%86-kubeconfig-%E9%80%89%E9%A1%B9">管理 Kubeconfig 选项</a>，文档介绍了通过修改启动参数和环境变量达到修改配置文件权限的目的。</p>
+<p>再次提示：<strong>正视配置模型的概念，<code>ConfigurationClassParser</code> 使用配置类构建配置模型并校验；<code>ConfigurationClassBeanDefinitionReader</code> 从配置模型中读取 <code>bean</code> 定义。</strong></p>
 </blockquote>
-<h4 id="修改启动参数"><a href="#修改启动参数" class="headerlink" title="修改启动参数"></a>修改启动参数</h4><p>第一种方式是修改启动参数。</p>
+<div style="width:50%;margin:auto"><img src="/2023/11/23/source-code-analysis-of-Spring-Configuration-annotation/Pasted%20image%2020231127214511.png" class="" title="处理配置类流程图"></div>
+
+<h3 id="解析配置类构建配置模型"><a href="#解析配置类构建配置模型" class="headerlink" title="解析配置类构建配置模型"></a>解析配置类构建配置模型</h3><p><code>parser.parse(candidates)</code> 正式进入解析过程，<code>ConfigurationClassParser</code> 负责将配置类转换为配置模型（<code>ConfigurationClass</code>）。</p>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title function_">parse</span><span class="params">(Set&lt;BeanDefinitionHolder&gt; configCandidates)</span> &#123;</span><br><span class="line">    <span class="built_in">this</span>.deferredImportSelectors = <span class="keyword">new</span> <span class="title class_">LinkedList</span>&lt;DeferredImportSelectorHolder&gt;();</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 循环依次处理配置类</span></span><br><span class="line">    <span class="keyword">for</span> (BeanDefinitionHolder holder : configCandidates) &#123;</span><br><span class="line">        <span class="type">BeanDefinition</span> <span class="variable">bd</span> <span class="operator">=</span> holder.getBeanDefinition();</span><br><span class="line">        <span class="keyword">try</span> &#123;</span><br><span class="line">            <span class="keyword">if</span> (bd <span class="keyword">instanceof</span> AnnotatedBeanDefinition) &#123;</span><br><span class="line">                <span class="comment">// 拥有注解的 BeanDefinition</span></span><br><span class="line">                parse(((AnnotatedBeanDefinition) bd).getMetadata(), holder.getBeanName());</span><br><span class="line">            &#125;</span><br><span class="line">            <span class="keyword">else</span> <span class="keyword">if</span> (bd <span class="keyword">instanceof</span> AbstractBeanDefinition &amp;&amp; ((AbstractBeanDefinition) bd).hasBeanClass()) &#123;</span><br><span class="line">                parse(((AbstractBeanDefinition) bd).getBeanClass(), holder.getBeanName());</span><br><span class="line">            &#125;</span><br><span class="line">            <span class="keyword">else</span> &#123;</span><br><span class="line">                parse(bd.getBeanClassName(), holder.getBeanName());</span><br><span class="line">            &#125;</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="keyword">catch</span> (BeanDefinitionStoreException ex) &#123;</span><br><span class="line">            <span class="keyword">throw</span> ex;</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="keyword">catch</span> (Throwable ex) &#123;</span><br><span class="line">            <span class="keyword">throw</span> <span class="keyword">new</span> <span class="title class_">BeanDefinitionStoreException</span>(</span><br><span class="line">                    <span class="string">&quot;Failed to parse configuration class [&quot;</span> + bd.getBeanClassName() + <span class="string">&quot;]&quot;</span>, ex);</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    processDeferredImportSelectors();</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<p>每次都创建一个新的配置模型 <code>ConfigurationClass</code>，最终处理结果以副作用的形式直接表现在配置模型上。</p>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">protected</span> <span class="keyword">final</span> <span class="keyword">void</span> <span class="title function_">parse</span><span class="params">(AnnotationMetadata metadata, String beanName)</span> <span class="keyword">throws</span> IOException &#123;</span><br><span class="line">    <span class="comment">// 每次都 new 一个 ConfigurationClass</span></span><br><span class="line">    processConfigurationClass(<span class="keyword">new</span> <span class="title class_">ConfigurationClass</span>(metadata, beanName));</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<div style="width:50%;margin:auto"><img src="/2023/11/23/source-code-analysis-of-Spring-Configuration-annotation/Pasted%20image%2020231127215414.png" class="" title="处理配置模型"></div>
+
+<p>处理配置模型的方法 <code>processConfigurationClass</code>。</p>
 <ol>
-<li><code>sudo vim /etc/systemd/system/k3s.service</code> 添加 <code>k3s</code> 启动参数 <code>--write-kubeconfig-mode 644</code><figure class="highlight ini"><table><tr><td class="code"><pre><span class="line"><span class="attr">ExecStart</span>=/usr/local/bin/k3s \</span><br><span class="line">    server --write-kubeconfig-mode 644 \</span><br></pre></td></tr></table></figure></li>
-<li><code>systemctl daemon-reload</code> 重新加载 <code>systemd</code> 配置</li>
-<li><code>systemctl restart k3s.service</code> 重启服务</li>
-<li>验证修改生效<figure class="highlight text"><table><tr><td class="code"><pre><span class="line">$ ll /etc/rancher/k3s/k3s.yaml</span><br><span class="line">-rw-r--r-- 1 root root 2961 Jan 30 20:13 /etc/rancher/k3s/k3s.yaml</span><br></pre></td></tr></table></figure></li>
+<li>检查配置模型是否曾经处理过</li>
+<li>处理配置模型（递归处理配置类和它的父类）</li>
 </ol>
-<h4 id="修改环境变量"><a href="#修改环境变量" class="headerlink" title="修改环境变量"></a>修改环境变量</h4><p>第二种方式是修改环境变量。</p>
+<p><code>SourceClass</code> 是一个简单的包装器，无论带注解的源类是如何被加载的，允许以统一的方式处理。</p>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">protected</span> <span class="keyword">void</span> <span class="title function_">processConfigurationClass</span><span class="params">(ConfigurationClass configClass)</span> <span class="keyword">throws</span> IOException &#123;</span><br><span class="line">    <span class="comment">// 判断是否跳过</span></span><br><span class="line">    <span class="keyword">if</span> (<span class="built_in">this</span>.conditionEvaluator.shouldSkip(configClass.getMetadata(), ConfigurationPhase.PARSE_CONFIGURATION)) &#123;</span><br><span class="line">        <span class="keyword">return</span>;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// ConfigurationClass 重写了 equals 和 hashCode 方法</span></span><br><span class="line">    <span class="type">ConfigurationClass</span> <span class="variable">existingClass</span> <span class="operator">=</span> <span class="built_in">this</span>.configurationClasses.get(configClass);</span><br><span class="line">    <span class="comment">// 判断是否已经存在</span></span><br><span class="line">    <span class="keyword">if</span> (existingClass != <span class="literal">null</span>) &#123;</span><br><span class="line">        <span class="comment">// 检查是否是导入的</span></span><br><span class="line">        <span class="keyword">if</span> (configClass.isImported()) &#123;</span><br><span class="line">            <span class="keyword">if</span> (existingClass.isImported()) &#123;</span><br><span class="line">                <span class="comment">// 如果新的旧的 isImported 均为 true，合并 ImportedBy 集合</span></span><br><span class="line">                existingClass.mergeImportedBy(configClass);</span><br><span class="line">            &#125;</span><br><span class="line">            <span class="comment">// Otherwise ignore new imported config class; existing non-imported class overrides it.</span></span><br><span class="line">            <span class="keyword">return</span>;</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="keyword">else</span> &#123;</span><br><span class="line">            <span class="comment">// 可能找到了一个显式定义的配置类，用于代替导入的，直接移除旧的</span></span><br><span class="line">            <span class="built_in">this</span>.configurationClasses.remove(configClass);</span><br><span class="line">            <span class="keyword">for</span> (Iterator&lt;ConfigurationClass&gt; it = <span class="built_in">this</span>.knownSuperclasses.values().iterator(); it.hasNext();) &#123;</span><br><span class="line">                <span class="keyword">if</span> (configClass.equals(it.next())) &#123;</span><br><span class="line">                    it.remove();</span><br><span class="line">                &#125;</span><br><span class="line">            &#125;</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 递归处理配置类和它的父类</span></span><br><span class="line">    <span class="type">SourceClass</span> <span class="variable">sourceClass</span> <span class="operator">=</span> asSourceClass(configClass);</span><br><span class="line">    <span class="keyword">do</span> &#123;</span><br><span class="line">        sourceClass = doProcessConfigurationClass(configClass, sourceClass);</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="keyword">while</span> (sourceClass != <span class="literal">null</span>);</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 保存处理过的配置模型</span></span><br><span class="line">    <span class="built_in">this</span>.configurationClasses.put(configClass, configClass);</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<p>注意 <code>ConfigurationClass</code> 重写了 <code>equals</code> 和 <code>hashCode</code> 方法，<code>metadata</code> 的 <code>className</code> 相同代表配置模型也相同。</p>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="type">boolean</span> <span class="title function_">equals</span><span class="params">(Object other)</span> &#123;</span><br><span class="line">    <span class="keyword">return</span> (<span class="built_in">this</span> == other || (other <span class="keyword">instanceof</span> ConfigurationClass &amp;&amp;</span><br><span class="line">            getMetadata().getClassName().equals(((ConfigurationClass) other).getMetadata().getClassName())));</span><br><span class="line">&#125;</span><br><span class="line"></span><br><span class="line"><span class="keyword">public</span> <span class="type">int</span> <span class="title function_">hashCode</span><span class="params">()</span> &#123;</span><br><span class="line">    <span class="keyword">return</span> getMetadata().getClassName().hashCode();</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<p>真正处理配置模型的方法，根据注释很容易知道，如果配置类携带了 <code>PropertySource</code>、<code>ComponentScan</code>、<code>Import</code>、<code>ImportResource</code>、<code>Bean</code> 等注解，就是在这里被处理的。<br>比如示例中被 <code>Bean</code> 注解标注的方法，<code>configClass.addBeanMethod(new BeanMethod(methodMetadata, configClass))</code> 将它以 <code>BeanMethod</code> 的形式添加到配置模型中。</p>
 <ol>
-<li><code>sudo vim /etc/systemd/system/k3s.service.env</code> 添加环境变量 <code>K3S_KUBECONFIG_MODE=644</code><figure class="highlight ini"><table><tr><td class="code"><pre><span class="line"><span class="attr">K3S_KUBECONFIG_MODE</span>=<span class="number">644</span></span><br></pre></td></tr></table></figure></li>
-<li><code>systemctl restart k3s.service</code> 重启服务</li>
+<li>先递归的处理成员（嵌套）类</li>
+<li>处理 <code>@PropertySource</code></li>
+<li>处理 <code>@ComponentScan</code></li>
+<li>处理 <code>@Import</code></li>
+<li>处理 <code>@ImportResource</code></li>
+<li>处理 <code>@Bean</code>，<strong>使用 <code>ASM</code> 代替 <code>JVM</code> 反射，以获得确定性的声明顺序</strong></li>
+<li>处理接口的默认方法</li>
+<li>检查是否有父类</li>
 </ol>
-<h4 id="修改配置文件路径"><a href="#修改配置文件路径" class="headerlink" title="修改配置文件路径"></a>修改配置文件路径</h4><p>第三种方式是复制配置信息到当前用户目录下，并使用其作为配置文件的路径。</p>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">protected</span> <span class="keyword">final</span> SourceClass <span class="title function_">doProcessConfigurationClass</span><span class="params">(ConfigurationClass configClass, SourceClass sourceClass)</span></span><br><span class="line">        <span class="keyword">throws</span> IOException &#123;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// Recursively process any member (nested) classes first</span></span><br><span class="line">    processMemberClasses(configClass, sourceClass);</span><br><span class="line"></span><br><span class="line">    <span class="comment">// Process any @PropertySource annotations</span></span><br><span class="line">    <span class="keyword">for</span> (AnnotationAttributes propertySource : AnnotationConfigUtils.attributesForRepeatable(</span><br><span class="line">            sourceClass.getMetadata(), PropertySources.class,</span><br><span class="line">            org.springframework.context.annotation.PropertySource.class)) &#123;</span><br><span class="line">        <span class="keyword">if</span> (<span class="built_in">this</span>.environment <span class="keyword">instanceof</span> ConfigurableEnvironment) &#123;</span><br><span class="line">            processPropertySource(propertySource);</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="keyword">else</span> &#123;</span><br><span class="line">            logger.warn(<span class="string">&quot;Ignoring @PropertySource annotation on [&quot;</span> + sourceClass.getMetadata().getClassName() +</span><br><span class="line">                    <span class="string">&quot;]. Reason: Environment must implement ConfigurableEnvironment&quot;</span>);</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// Process any @ComponentScan annotations</span></span><br><span class="line">    Set&lt;AnnotationAttributes&gt; componentScans = AnnotationConfigUtils.attributesForRepeatable(</span><br><span class="line">            sourceClass.getMetadata(), ComponentScans.class, ComponentScan.class);</span><br><span class="line">    <span class="keyword">if</span> (!componentScans.isEmpty() &amp;&amp;</span><br><span class="line">            !<span class="built_in">this</span>.conditionEvaluator.shouldSkip(sourceClass.getMetadata(), ConfigurationPhase.REGISTER_BEAN)) &#123;</span><br><span class="line">        <span class="keyword">for</span> (AnnotationAttributes componentScan : componentScans) &#123;</span><br><span class="line">            <span class="comment">// The config class is annotated with @ComponentScan -&gt; perform the scan immediately</span></span><br><span class="line">            Set&lt;BeanDefinitionHolder&gt; scannedBeanDefinitions =</span><br><span class="line">                    <span class="built_in">this</span>.componentScanParser.parse(componentScan, sourceClass.getMetadata().getClassName());</span><br><span class="line">            <span class="comment">// Check the set of scanned definitions for any further config classes and parse recursively if needed</span></span><br><span class="line">            <span class="keyword">for</span> (BeanDefinitionHolder holder : scannedBeanDefinitions) &#123;</span><br><span class="line">                <span class="keyword">if</span> (ConfigurationClassUtils.checkConfigurationClassCandidate(</span><br><span class="line">                        holder.getBeanDefinition(), <span class="built_in">this</span>.metadataReaderFactory)) &#123;</span><br><span class="line">                    parse(holder.getBeanDefinition().getBeanClassName(), holder.getBeanName());</span><br><span class="line">                &#125;</span><br><span class="line">            &#125;</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// Process any @Import annotations</span></span><br><span class="line">    processImports(configClass, sourceClass, getImports(sourceClass), <span class="literal">true</span>);</span><br><span class="line"></span><br><span class="line">    <span class="comment">// Process any @ImportResource annotations</span></span><br><span class="line">    <span class="keyword">if</span> (sourceClass.getMetadata().isAnnotated(ImportResource.class.getName())) &#123;</span><br><span class="line">        <span class="type">AnnotationAttributes</span> <span class="variable">importResource</span> <span class="operator">=</span></span><br><span class="line">                AnnotationConfigUtils.attributesFor(sourceClass.getMetadata(), ImportResource.class);</span><br><span class="line">        String[] resources = importResource.getStringArray(<span class="string">&quot;locations&quot;</span>);</span><br><span class="line">        Class&lt;? <span class="keyword">extends</span> <span class="title class_">BeanDefinitionReader</span>&gt; readerClass = importResource.getClass(<span class="string">&quot;reader&quot;</span>);</span><br><span class="line">        <span class="keyword">for</span> (String resource : resources) &#123;</span><br><span class="line">            <span class="type">String</span> <span class="variable">resolvedResource</span> <span class="operator">=</span> <span class="built_in">this</span>.environment.resolveRequiredPlaceholders(resource);</span><br><span class="line">            configClass.addImportedResource(resolvedResource, readerClass);</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// Process individual @Bean methods</span></span><br><span class="line">    Set&lt;MethodMetadata&gt; beanMethods = retrieveBeanMethodMetadata(sourceClass);</span><br><span class="line">    <span class="keyword">for</span> (MethodMetadata methodMetadata : beanMethods) &#123;</span><br><span class="line">        configClass.addBeanMethod(<span class="keyword">new</span> <span class="title class_">BeanMethod</span>(methodMetadata, configClass));</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// Process default methods on interfaces</span></span><br><span class="line">    processInterfaces(configClass, sourceClass);</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 如果有父类，且之前没有处理过，返回父类继续处理</span></span><br><span class="line">    <span class="keyword">if</span> (sourceClass.getMetadata().hasSuperClass()) &#123;</span><br><span class="line">        <span class="type">String</span> <span class="variable">superclass</span> <span class="operator">=</span> sourceClass.getMetadata().getSuperClassName();</span><br><span class="line">        <span class="keyword">if</span> (!superclass.startsWith(<span class="string">&quot;java&quot;</span>) &amp;&amp; !<span class="built_in">this</span>.knownSuperclasses.containsKey(superclass)) &#123;</span><br><span class="line">            <span class="built_in">this</span>.knownSuperclasses.put(superclass, configClass);</span><br><span class="line">            <span class="comment">// Superclass found, return its annotation metadata and recurse</span></span><br><span class="line">            <span class="keyword">return</span> sourceClass.getSuperClass();</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// No superclass -&gt; processing is complete</span></span><br><span class="line">    <span class="keyword">return</span> <span class="literal">null</span>;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<h3 id="读取配置模型，加载-Bean-定义"><a href="#读取配置模型，加载-Bean-定义" class="headerlink" title="读取配置模型，加载 Bean 定义"></a>读取配置模型，加载 Bean 定义</h3><p><code>this.reader.loadBeanDefinitions(configClasses)</code> 读取配置模型的内容，注册 <code>BeanDefinitions</code> 到 <code>BeanDefinition Registry</code>（也就是 <code>BeanFactory</code>）。</p>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title function_">loadBeanDefinitions</span><span class="params">(Set&lt;ConfigurationClass&gt; configurationModel)</span> &#123;</span><br><span class="line">    <span class="type">TrackedConditionEvaluator</span> <span class="variable">trackedConditionEvaluator</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">TrackedConditionEvaluator</span>();</span><br><span class="line">    <span class="comment">// 叫 ConfigurationModel 多好啊，ConfigurationClass 真让人容易误解</span></span><br><span class="line">    <span class="keyword">for</span> (ConfigurationClass configClass : configurationModel) &#123;</span><br><span class="line">        loadBeanDefinitionsForConfigurationClass(configClass, trackedConditionEvaluator);</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<p>处理单独的一个配置模型。</p>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">private</span> <span class="keyword">void</span> <span class="title function_">loadBeanDefinitionsForConfigurationClass</span><span class="params">(ConfigurationClass configClass,</span></span><br><span class="line"><span class="params">        TrackedConditionEvaluator trackedConditionEvaluator)</span> &#123;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">if</span> (trackedConditionEvaluator.shouldSkip(configClass)) &#123;</span><br><span class="line">        <span class="type">String</span> <span class="variable">beanName</span> <span class="operator">=</span> configClass.getBeanName();</span><br><span class="line">        <span class="keyword">if</span> (StringUtils.hasLength(beanName) &amp;&amp; <span class="built_in">this</span>.registry.containsBeanDefinition(beanName)) &#123;</span><br><span class="line">            <span class="built_in">this</span>.registry.removeBeanDefinition(beanName);</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="built_in">this</span>.importRegistry.removeImportingClass(configClass.getMetadata().getClassName());</span><br><span class="line">        <span class="keyword">return</span>;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">if</span> (configClass.isImported()) &#123;</span><br><span class="line">        registerBeanDefinitionForImportedConfigurationClass(configClass);</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="keyword">for</span> (BeanMethod beanMethod : configClass.getBeanMethods()) &#123;</span><br><span class="line">        loadBeanDefinitionsForBeanMethod(beanMethod);</span><br><span class="line">    &#125;</span><br><span class="line">    loadBeanDefinitionsFromImportedResources(configClass.getImportedResources());</span><br><span class="line">    loadBeanDefinitionsFromRegistrars(configClass.getImportBeanDefinitionRegistrars());</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<h2 id="增强配置类"><a href="#增强配置类" class="headerlink" title="增强配置类"></a>增强配置类</h2><p>我们在介绍 <code>ConfigurationClassPostProcessor</code> 时提过，它既实现了接口 <code>BeanDefinitionRegistryPostProcessor</code>，也因此同时实现了接口 <code>BeanFactoryPostProcessor</code>。在 <code>invokeBeanFactoryPostProcessors(beanFactory)</code> 阶段，调用 <code>postProcessBeanDefinitionRegistry</code> 方法，成功注册配置类引入的 <code>Bean</code> 后，紧接着会调用 <code>postProcessBeanFactory</code> 方法，增强配置类本身。</p>
+<blockquote>
+<p><code>ConfigurationClasses</code> 在之前还是指配置模型，这里就又指配置类了。。。真让人头秃。</p>
+</blockquote>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title function_">postProcessBeanFactory</span><span class="params">(ConfigurableListableBeanFactory beanFactory)</span> &#123;</span><br><span class="line">    <span class="comment">// ...</span></span><br><span class="line"></span><br><span class="line">    <span class="comment">// 增强配置类</span></span><br><span class="line">    enhanceConfigurationClasses(beanFactory);</span><br><span class="line">    <span class="comment">// 添加后处理器 ImportAwareBeanPostProcessor</span></span><br><span class="line">    beanFactory.addBeanPostProcessor(<span class="keyword">new</span> <span class="title class_">ImportAwareBeanPostProcessor</span>(beanFactory));</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<h3 id="增强所有-Full-类型配置类"><a href="#增强所有-Full-类型配置类" class="headerlink" title="增强所有 Full 类型配置类"></a>增强所有 Full 类型配置类</h3><ol>
+<li>查找所有 <code>Full</code> 类型的配置类</li>
+<li>依次使用 <code>ConfigurationClassEnhancer</code> 增强目标类，成功则替换 <code>BeanClass</code>（不成功的情况是已经增强过）</li>
+</ol>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">void</span> <span class="title function_">enhanceConfigurationClasses</span><span class="params">(ConfigurableListableBeanFactory beanFactory)</span> &#123;</span><br><span class="line">    Map&lt;String, AbstractBeanDefinition&gt; configBeanDefs = <span class="keyword">new</span> <span class="title class_">LinkedHashMap</span>&lt;String, AbstractBeanDefinition&gt;();</span><br><span class="line">    <span class="comment">// 获取全部的 BeanDefinitions 检查是否存在全配置类（FullConfigurationClass）</span></span><br><span class="line">    <span class="keyword">for</span> (String beanName : beanFactory.getBeanDefinitionNames()) &#123;</span><br><span class="line">        <span class="type">BeanDefinition</span> <span class="variable">beanDef</span> <span class="operator">=</span> beanFactory.getBeanDefinition(beanName);</span><br><span class="line">        <span class="keyword">if</span> (ConfigurationClassUtils.isFullConfigurationClass(beanDef)) &#123;</span><br><span class="line">            <span class="keyword">if</span> (!(beanDef <span class="keyword">instanceof</span> AbstractBeanDefinition)) &#123;</span><br><span class="line">                <span class="keyword">throw</span> <span class="keyword">new</span> <span class="title class_">BeanDefinitionStoreException</span>(<span class="string">&quot;Cannot enhance @Configuration bean definition &#x27;&quot;</span> +</span><br><span class="line">                        beanName + <span class="string">&quot;&#x27; since it is not stored in an AbstractBeanDefinition subclass&quot;</span>);</span><br><span class="line">            &#125;</span><br><span class="line">            <span class="keyword">else</span> <span class="keyword">if</span> (logger.isWarnEnabled() &amp;&amp; beanFactory.containsSingleton(beanName)) &#123;</span><br><span class="line">                logger.warn(<span class="string">&quot;Cannot enhance @Configuration bean definition &#x27;&quot;</span> + beanName +</span><br><span class="line">                        <span class="string">&quot;&#x27; since its singleton instance has been created too early. The typical cause &quot;</span> +</span><br><span class="line">                        <span class="string">&quot;is a non-static @Bean method with a BeanDefinitionRegistryPostProcessor &quot;</span> +</span><br><span class="line">                        <span class="string">&quot;return type: Consider declaring such methods as &#x27;static&#x27;.&quot;</span>);</span><br><span class="line">            &#125;</span><br><span class="line">            configBeanDefs.put(beanName, (AbstractBeanDefinition) beanDef);</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="keyword">if</span> (configBeanDefs.isEmpty()) &#123;</span><br><span class="line">        <span class="keyword">return</span>;</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="comment">// 通过 CGLib 增强</span></span><br><span class="line">    <span class="type">ConfigurationClassEnhancer</span> <span class="variable">enhancer</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">ConfigurationClassEnhancer</span>();</span><br><span class="line">    <span class="keyword">for</span> (Map.Entry&lt;String, AbstractBeanDefinition&gt; entry : configBeanDefs.entrySet()) &#123;</span><br><span class="line">        <span class="type">AbstractBeanDefinition</span> <span class="variable">beanDef</span> <span class="operator">=</span> entry.getValue();</span><br><span class="line">        <span class="comment">// 如果被 @Configuration 注解的类被代理，则始终代理目标类（proxy target class），在 Attributes 中标记</span></span><br><span class="line">        beanDef.setAttribute(AutoProxyUtils.PRESERVE_TARGET_CLASS_ATTRIBUTE, Boolean.TRUE);</span><br><span class="line">        <span class="keyword">try</span> &#123;</span><br><span class="line">            Class&lt;?&gt; configClass = beanDef.resolveBeanClass(<span class="built_in">this</span>.beanClassLoader);</span><br><span class="line">            Class&lt;?&gt; enhancedClass = enhancer.enhance(configClass, <span class="built_in">this</span>.beanClassLoader);</span><br><span class="line">            <span class="keyword">if</span> (configClass != enhancedClass) &#123;</span><br><span class="line">                <span class="keyword">if</span> (logger.isDebugEnabled()) &#123;</span><br><span class="line">                    logger.debug(String.format(<span class="string">&quot;Replacing bean definition &#x27;%s&#x27; existing class &#x27;%s&#x27; with &quot;</span> +</span><br><span class="line">                            <span class="string">&quot;enhanced class &#x27;%s&#x27;&quot;</span>, entry.getKey(), configClass.getName(), enhancedClass.getName()));</span><br><span class="line">                &#125;</span><br><span class="line">                <span class="comment">// 如果成功增强，则替换掉 BeanClass</span></span><br><span class="line">                beanDef.setBeanClass(enhancedClass);</span><br><span class="line">            &#125;</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="keyword">catch</span> (Throwable ex) &#123;</span><br><span class="line">            <span class="keyword">throw</span> <span class="keyword">new</span> <span class="title class_">IllegalStateException</span>(<span class="string">&quot;Cannot load configuration class: &quot;</span> + beanDef.getBeanClassName(), ex);</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
 <ol>
-<li>设置环境变量 <code>export KUBECONFIG=~/.kube/config</code></li>
-<li>创建文件夹 <code>mkdir ~/.kube 2&gt; /dev/null</code></li>
-<li>复制配置信息 <code>sudo k3s kubectl config view --raw &gt; &quot;$KUBECONFIG&quot;</code></li>
-<li>修改配置文件的权限 <code>chmod 600 &quot;$KUBECONFIG&quot;</code></li>
+<li>如果增强过则不再处理。这往往代表容器中存在多个 <code>ConfigurationClassPostProcessor</code>，虽然无害，但是建议调整配置</li>
+<li>如果未曾增强过，则创建增强类</li>
 </ol>
-<h3 id="配置代理"><a href="#配置代理" class="headerlink" title="配置代理"></a>配置代理</h3><p>涉及 <code>k8s</code>，难免需要使用代理，否则在拉取镜像时将寸步难行。官方文档 <a href="https://docs.k3s.io/zh/advanced#%E9%85%8D%E7%BD%AE-http-%E4%BB%A3%E7%90%86">配置 HTTP 代理</a> 介绍了如何配置代理。其中提及 <code>k3s</code> 安装脚本会自动使用当前 <code>shell</code> 中的 <code>HTTP_PROXY</code>、<code>HTTPS_PROXY</code> 和 <code>NO_PROXY</code>，以及 <code>CONTAINERD_HTTP_PROXY</code>、<code>CONTAINERD_HTTPS_PROXY</code> 和 <code>CONTAINERD_NO_PROXY</code> 变量（如果存在），并将它们写入 <code>systemd</code> 服务的环境文件。比如我设置过 <code>shell</code> 变量 <code>HTTP_PROXY</code>、<code>HTTPS_PROXY</code> 和 <code>NO_PROXY</code>，<code>/etc/systemd/system/k3s.service.env</code> 如下，你也可以自行编辑修改。</p>
-<figure class="highlight ini"><table><tr><td class="code"><pre><span class="line"><span class="attr">http_proxy</span>=<span class="string">&#x27;http://127.0.0.1:7890&#x27;</span></span><br><span class="line"><span class="attr">https_proxy</span>=<span class="string">&#x27;http://127.0.0.1:7890&#x27;</span></span><br><span class="line"><span class="attr">no_proxy</span>=<span class="string">&#x27;localhost,127.0.0.1&#x27;</span></span><br><span class="line"><span class="attr">K3S_KUBECONFIG_MODE</span>=<span class="number">644</span></span><br></pre></td></tr></table></figure>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> Class&lt;?&gt; enhance(Class&lt;?&gt; configClass, ClassLoader classLoader) &#123;</span><br><span class="line">    <span class="comment">// 增强过的类都实现了 EnhancedConfiguration，因此可以起到标识作用</span></span><br><span class="line">    <span class="keyword">if</span> (EnhancedConfiguration.class.isAssignableFrom(configClass)) &#123;</span><br><span class="line">        <span class="keyword">if</span> (logger.isDebugEnabled()) &#123;</span><br><span class="line">            logger.debug(String.format(<span class="string">&quot;Ignoring request to enhance %s as it has &quot;</span> +</span><br><span class="line">                    <span class="string">&quot;already been enhanced. This usually indicates that more than one &quot;</span> +</span><br><span class="line">                    <span class="string">&quot;ConfigurationClassPostProcessor has been registered (e.g. via &quot;</span> +</span><br><span class="line">                    <span class="string">&quot;&lt;context:annotation-config&gt;). This is harmless, but you may &quot;</span> +</span><br><span class="line">                    <span class="string">&quot;want check your configuration and remove one CCPP if possible&quot;</span>,</span><br><span class="line">                    configClass.getName()));</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="keyword">return</span> configClass;</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="comment">// 创建增强类</span></span><br><span class="line">    Class&lt;?&gt; enhancedClass = createClass(newEnhancer(configClass, classLoader));</span><br><span class="line">    <span class="keyword">if</span> (logger.isDebugEnabled()) &#123;</span><br><span class="line">        logger.debug(String.format(<span class="string">&quot;Successfully enhanced %s; enhanced class name is: %s&quot;</span>,</span><br><span class="line">                configClass.getName(), enhancedClass.getName()));</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="keyword">return</span> enhancedClass;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
 
-<h2 id="使用"><a href="#使用" class="headerlink" title="使用"></a>使用</h2><blockquote>
-<p>k8s 基础教程可参考官方文档 <a href="https://kubernetes.io/zh-cn/docs/tutorials/kubernetes-basics/">Kubernetes 基础</a>。</p>
+<h3 id="创建-CGLib-子类"><a href="#创建-CGLib-子类" class="headerlink" title="创建 CGLib 子类"></a>创建 CGLib 子类</h3><blockquote>
+<p>如果完全不熟悉 <code>CGLib</code>，可以单独查阅一下相关资料，稍作了解。</p>
 </blockquote>
-<h3 id="创建-Deployment"><a href="#创建-Deployment" class="headerlink" title="创建 Deployment"></a>创建 Deployment</h3><ol>
-<li>使用 <code>kubectl create</code> 命令创建管理 <code>Pod</code> 的 <code>Deployment</code>。该 <code>Pod</code> 根据提供的 <code>Docker</code> 镜像运行容器。<figure class="highlight shell"><table><tr><td class="code"><pre><span class="line">kubectl create deployment hello-node --image=registry.k8s.io/e2e-test-images/agnhost:2.39 -- /agnhost netexec --http-port=8080</span><br></pre></td></tr></table></figure></li>
-<li>查看 <code>Deployment</code>：<figure class="highlight text"><table><tr><td class="code"><pre><span class="line">$ kubectl get pods</span><br><span class="line">NAME                         READY   STATUS    RESTARTS   AGE</span><br><span class="line">hello-node-ccf4b9788-d8k9b   1/1     Running   0          15h</span><br></pre></td></tr></table></figure></li>
-<li>查看 <code>Pod</code> 中容器的应用程序日志。<figure class="highlight text"><table><tr><td class="code"><pre><span class="line">$ kubectl logs hello-node-ccf4b9788-d8k9b</span><br><span class="line">I0130 19:26:57.751131       1 log.go:195] Started HTTP server on port 8080</span><br><span class="line">I0130 19:26:57.751350       1 log.go:195] Started UDP server on port  8081</span><br></pre></td></tr></table></figure></li>
+<p>创建 <code>Enhancer</code>，并设置属性。</p>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">private</span> Enhancer <span class="title function_">newEnhancer</span><span class="params">(Class&lt;?&gt; superclass, ClassLoader classLoader)</span> &#123;</span><br><span class="line">    <span class="type">Enhancer</span> <span class="variable">enhancer</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">Enhancer</span>();</span><br><span class="line">    <span class="comment">// 设置被增强的类为父类</span></span><br><span class="line">    enhancer.setSuperclass(superclass);</span><br><span class="line">    <span class="comment">// 设置接口，可以用于标识类被增强过</span></span><br><span class="line">    enhancer.setInterfaces(<span class="keyword">new</span> <span class="title class_">Class</span>&lt;?&gt;[] &#123;EnhancedConfiguration.class&#125;);</span><br><span class="line">    enhancer.setUseFactory(<span class="literal">false</span>);</span><br><span class="line">    <span class="comment">// 设置命名策略，BySpringCGLIB 后缀</span></span><br><span class="line">    enhancer.setNamingPolicy(SpringNamingPolicy.INSTANCE);</span><br><span class="line">    <span class="comment">// 设置生成策略，这里为 CGLib 子类新增一个 $$beanFactory 属性</span></span><br><span class="line">    enhancer.setStrategy(<span class="keyword">new</span> <span class="title class_">BeanFactoryAwareGeneratorStrategy</span>(classLoader));</span><br><span class="line">    <span class="comment">// 设置 CallbackFilter，用于方法匹配</span></span><br><span class="line">    enhancer.setCallbackFilter(CALLBACK_FILTER);</span><br><span class="line">    enhancer.setCallbackTypes(CALLBACK_FILTER.getCallbackTypes());</span><br><span class="line">    <span class="keyword">return</span> enhancer;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<ul>
+<li>所有因为 <code>Configuration</code> 注解而被增强的配置类，它的 <code>CGLib</code> 子类都实现了这个标记接口，用于检查候选类是否已经增强过，避免重复增强。</li>
+<li>该接口继承了 <code>BeanFactoryAware</code>。**创建得到的 <code>CGLib</code> 子类必须能够访问 <code>BeanFactory</code>**，用以在工厂方法交叉调用时获取已经创建的 <code>Bean</code> 而非真正执行。</li>
+</ul>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">interface</span> <span class="title class_">EnhancedConfiguration</span> <span class="keyword">extends</span> <span class="title class_">BeanFactoryAware</span> &#123;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<p>创建子类，并注册静态回调。</p>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">private</span> Class&lt;?&gt; createClass(Enhancer enhancer) &#123;</span><br><span class="line">    Class&lt;?&gt; subclass = enhancer.createClass();</span><br><span class="line">    <span class="comment">// 注册静态回调（虽然注释不太理解）</span></span><br><span class="line">    Enhancer.registerStaticCallbacks(subclass, CALLBACKS);</span><br><span class="line">    <span class="keyword">return</span> subclass;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<p><code>CALLBACKS</code>、<code>CALLBACK_FILTER</code> 和 <code>$$beanFactory</code> 属性名都是 <code>ConfigurationClassEnhancer</code> 的静态属性。</p>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">class</span> <span class="title class_">ConfigurationClassEnhancer</span> &#123;</span><br><span class="line">    <span class="comment">// The callbacks to use. Note that these callbacks must be stateless.</span></span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">static</span> <span class="keyword">final</span> Callback[] CALLBACKS = <span class="keyword">new</span> <span class="title class_">Callback</span>[] &#123;</span><br><span class="line">            <span class="keyword">new</span> <span class="title class_">BeanMethodInterceptor</span>(),</span><br><span class="line">            <span class="keyword">new</span> <span class="title class_">BeanFactoryAwareMethodInterceptor</span>(),</span><br><span class="line">            NoOp.INSTANCE</span><br><span class="line">    &#125;;</span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">static</span> <span class="keyword">final</span> <span class="type">ConditionalCallbackFilter</span> <span class="variable">CALLBACK_FILTER</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">ConditionalCallbackFilter</span>(CALLBACKS);</span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">static</span> <span class="keyword">final</span> <span class="type">String</span> <span class="variable">BEAN_FACTORY_FIELD</span> <span class="operator">=</span> <span class="string">&quot;$$beanFactory&quot;</span>;</span><br><span class="line">    <span class="comment">// ...</span></span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<h3 id="匹配回调-ConditionalCallbackFilter"><a href="#匹配回调-ConditionalCallbackFilter" class="headerlink" title="匹配回调 ConditionalCallbackFilter"></a>匹配回调 ConditionalCallbackFilter</h3><p><code>ConditionalCallbackFilter</code> 实现了 <code>CGLib</code> 的 <code>CallbackFilter</code> 接口，<code>accept</code> 方法返回准备使用的 <code>Callback</code> 的索引。匹配规则如下：</p>
+<ol>
+<li>遍历 <code>callbacks</code>，依次判断<ol>
+<li>如果 <code>this.callbacks[i]</code> 不是 <code>ConditionalCallback</code> 类型，直接返回。根据 <code>CALLBACKS</code> 的值，这意味着没有匹配到合适的 <code>MethodInterceptor</code>，选择 <code>NoOp.INSTANCE</code>。</li>
+<li>如果 <code>this.callbacks[i]</code> 是 <code>ConditionalCallback</code> 类型，使用 <code>isMatch</code> 方法判断是否匹配，匹配成功返回对应索引</li>
 </ol>
-<h3 id="创建-Service"><a href="#创建-Service" class="headerlink" title="创建 Service"></a>创建 Service</h3><ol>
-<li>使用 <code>kubectl expose</code> 命令将 <code>Pod</code> 暴露给公网：<figure class="highlight shell"><table><tr><td class="code"><pre><span class="line">kubectl expose deployment hello-node --type=LoadBalancer --port=8080</span><br></pre></td></tr></table></figure></li>
-<li>查看你创建的 <code>Service</code>：<figure class="highlight text"><table><tr><td class="code"><pre><span class="line">$ kubectl get services</span><br><span class="line">NAME         TYPE           CLUSTER-IP     EXTERNAL-IP      PORT(S)          AGE</span><br><span class="line">kubernetes   ClusterIP      10.43.0.1      &lt;none&gt;           443/TCP          15h</span><br><span class="line">hello-node   LoadBalancer   10.43.37.170   192.168.46.128   8080:32117/TCP   15h</span><br></pre></td></tr></table></figure></li>
-<li>使用 <code>curl</code> 发起请求：<figure class="highlight text"><table><tr><td class="code"><pre><span class="line">$ curl http://localhost:8080</span><br><span class="line">NOW: 2024-01-31 10:55:14.228709273 +0000 UTC m=+25932.159732511</span><br></pre></td></tr></table></figure></li>
-<li>再次查看 <code>Pod</code> 中容器的应用程序日志。<figure class="highlight text"><table><tr><td class="code"><pre><span class="line">$ kubectl logs hello-node-ccf4b9788-d8k9b</span><br><span class="line">I0130 19:26:57.751131       1 log.go:195] Started HTTP server on port 8080</span><br><span class="line">I0130 19:26:57.751350       1 log.go:195] Started UDP server on port  8081</span><br><span class="line">I0130 19:32:21.074992       1 log.go:195] GET /</span><br></pre></td></tr></table></figure></li>
+</li>
 </ol>
-<h3 id="清理"><a href="#清理" class="headerlink" title="清理"></a>清理</h3><ol>
-<li>删除 <code>Service</code>：<figure class="highlight shell"><table><tr><td class="code"><pre><span class="line">kubectl delete service hello-node</span><br></pre></td></tr></table></figure></li>
-<li>删除 <code>Deployment</code>：<figure class="highlight shell"><table><tr><td class="code"><pre><span class="line">kubectl delete deployment hello-node</span><br></pre></td></tr></table></figure></li>
+<p><code>Callback</code> 中除了 <code>NoOp.INSTANCE</code>，还有 <code>BeanFactoryAwareMethodInterceptor</code> 用于拦截 <code>setBeanFactory</code> 方法，以及 <code>BeanMethodInterceptor</code> 拦截 <code>@Bean</code> 方法。</p>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">private</span> <span class="keyword">static</span> <span class="keyword">class</span> <span class="title class_">ConditionalCallbackFilter</span> <span class="keyword">implements</span> <span class="title class_">CallbackFilter</span> &#123;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">final</span> Callback[] callbacks;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">final</span> Class&lt;?&gt;[] callbackTypes;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">public</span> <span class="title function_">ConditionalCallbackFilter</span><span class="params">(Callback[] callbacks)</span> &#123;</span><br><span class="line">        <span class="built_in">this</span>.callbacks = callbacks;</span><br><span class="line">        <span class="built_in">this</span>.callbackTypes = <span class="keyword">new</span> <span class="title class_">Class</span>&lt;?&gt;[callbacks.length];</span><br><span class="line">        <span class="keyword">for</span> (<span class="type">int</span> <span class="variable">i</span> <span class="operator">=</span> <span class="number">0</span>; i &lt; callbacks.length; i++) &#123;</span><br><span class="line">            <span class="built_in">this</span>.callbackTypes[i] = callbacks[i].getClass();</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="meta">@Override</span></span><br><span class="line">    <span class="keyword">public</span> <span class="type">int</span> <span class="title function_">accept</span><span class="params">(Method method)</span> &#123;</span><br><span class="line">        <span class="keyword">for</span> (<span class="type">int</span> <span class="variable">i</span> <span class="operator">=</span> <span class="number">0</span>; i &lt; <span class="built_in">this</span>.callbacks.length; i++) &#123;</span><br><span class="line">            <span class="keyword">if</span> (!(<span class="built_in">this</span>.callbacks[i] <span class="keyword">instanceof</span> ConditionalCallback) ||</span><br><span class="line">                    ((ConditionalCallback) <span class="built_in">this</span>.callbacks[i]).isMatch(method)) &#123;</span><br><span class="line">                <span class="keyword">return</span> i;</span><br><span class="line">            &#125;</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="keyword">throw</span> <span class="keyword">new</span> <span class="title class_">IllegalStateException</span>(<span class="string">&quot;No callback available for method &quot;</span> + method.getName());</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">public</span> Class&lt;?&gt;[] getCallbackTypes() &#123;</span><br><span class="line">        <span class="keyword">return</span> <span class="built_in">this</span>.callbackTypes;</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<h3 id="拦截-setBeanFactory-方法"><a href="#拦截-setBeanFactory-方法" class="headerlink" title="拦截 setBeanFactory 方法"></a>拦截 setBeanFactory 方法</h3><p><code>BeanFactoryAwareMethodInterceptor</code> 实现了 <code>MethodInterceptor</code> 和 <code>ConditionalCallback</code> 接口。<code>isMatch</code> 匹配到 <code>BeanFactoryAware</code> 接口的 <code>setBeanFactory</code> 方法，则调用 <code>intercept</code> 方法，为 <code>$$beanFactory</code> 属性赋值。<code>$$beanFactory</code> 是 <code>CGLib</code> 生成的 <code>BeanFactory</code> 类型的属性。这个属性是通过设置 <code>enhancer.setStrategy(new BeanFactoryAwareGeneratorStrategy(classLoader))</code> 生成的。</p>
+<p>这样，当配置类 <code>Bean</code> 被创建时，会因为实现了 <code>BeanFactoryAware</code>，在初始化阶段被调用 <code>setBeanFactory</code> 方法而被拦截。拦截后将获得的 <code>beanFactory</code> 实例保存在 <code>CGlib</code> 生成的属性 <code>$$beanFactory</code> 中。</p>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">private</span> <span class="keyword">static</span> <span class="keyword">class</span> <span class="title class_">BeanFactoryAwareMethodInterceptor</span> <span class="keyword">implements</span> <span class="title class_">MethodInterceptor</span>, ConditionalCallback &#123;</span><br><span class="line"></span><br><span class="line">    <span class="meta">@Override</span></span><br><span class="line">    <span class="keyword">public</span> Object <span class="title function_">intercept</span><span class="params">(Object obj, Method method, Object[] args, MethodProxy proxy)</span> <span class="keyword">throws</span> Throwable &#123;</span><br><span class="line">        <span class="type">Field</span> <span class="variable">field</span> <span class="operator">=</span> ReflectionUtils.findField(obj.getClass(), BEAN_FACTORY_FIELD);</span><br><span class="line">        Assert.state(field != <span class="literal">null</span>, <span class="string">&quot;Unable to find generated BeanFactory field&quot;</span>);</span><br><span class="line">        <span class="comment">// 设置 beanFactory 的值</span></span><br><span class="line">        field.set(obj, args[<span class="number">0</span>]);</span><br><span class="line"></span><br><span class="line">        <span class="comment">// Does the actual (non-CGLIB) superclass implement BeanFactoryAware?</span></span><br><span class="line">        <span class="comment">// If so, call its setBeanFactory() method. If not, just exit.</span></span><br><span class="line">        <span class="comment">// 如果实际的（non-CGLIB）父类实现了 BeanFactoryAware 接口，调用它的 setBeanFactory() 方法</span></span><br><span class="line">        <span class="keyword">if</span> (BeanFactoryAware.class.isAssignableFrom(ClassUtils.getUserClass(obj.getClass().getSuperclass()))) &#123;</span><br><span class="line">            <span class="keyword">return</span> proxy.invokeSuper(obj, args);</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="keyword">return</span> <span class="literal">null</span>;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 根据方法名、参数数量、参数类型、方法所在的类判断</span></span><br><span class="line">    <span class="meta">@Override</span></span><br><span class="line">    <span class="keyword">public</span> <span class="type">boolean</span> <span class="title function_">isMatch</span><span class="params">(Method candidateMethod)</span> &#123;</span><br><span class="line">        <span class="keyword">return</span> (candidateMethod.getName().equals(<span class="string">&quot;setBeanFactory&quot;</span>) &amp;&amp;</span><br><span class="line">                candidateMethod.getParameterTypes().length == <span class="number">1</span> &amp;&amp;</span><br><span class="line">                BeanFactory.class == candidateMethod.getParameterTypes()[<span class="number">0</span>] &amp;&amp;</span><br><span class="line">                BeanFactoryAware.class.isAssignableFrom(candidateMethod.getDeclaringClass()));</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<h4 id="生成-beanFactory-属性"><a href="#生成-beanFactory-属性" class="headerlink" title="生成 $$beanFactory 属性"></a>生成 $$beanFactory 属性</h4><p><code>BeanFactoryAwareGeneratorStrategy</code> 为配置的 <code>CGLib</code> 子类生成一个访问控制符为 <code>public</code>、类型为 <code>BeanFactory</code>、名称为 <code>$$beanFactory</code> 的属性。</p>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">private</span> <span class="keyword">static</span> <span class="keyword">class</span> <span class="title class_">BeanFactoryAwareGeneratorStrategy</span> <span class="keyword">extends</span> <span class="title class_">DefaultGeneratorStrategy</span> &#123;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">final</span> ClassLoader classLoader;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">public</span> <span class="title function_">BeanFactoryAwareGeneratorStrategy</span><span class="params">(ClassLoader classLoader)</span> &#123;</span><br><span class="line">        <span class="built_in">this</span>.classLoader = classLoader;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="meta">@Override</span></span><br><span class="line">    <span class="keyword">protected</span> ClassGenerator <span class="title function_">transform</span><span class="params">(ClassGenerator cg)</span> <span class="keyword">throws</span> Exception &#123;</span><br><span class="line">        <span class="type">ClassEmitterTransformer</span> <span class="variable">transformer</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">ClassEmitterTransformer</span>() &#123;</span><br><span class="line">            <span class="meta">@Override</span></span><br><span class="line">            <span class="keyword">public</span> <span class="keyword">void</span> <span class="title function_">end_class</span><span class="params">()</span> &#123;</span><br><span class="line">                <span class="comment">// 新增一个访问控制符为 public、类型为 BeanFactory、名称为 $$beanFactory 的属性</span></span><br><span class="line">                declare_field(Constants.ACC_PUBLIC, BEAN_FACTORY_FIELD, Type.getType(BeanFactory.class), <span class="literal">null</span>);</span><br><span class="line">                <span class="built_in">super</span>.end_class();</span><br><span class="line">            &#125;</span><br><span class="line">        &#125;;</span><br><span class="line">        <span class="keyword">return</span> <span class="keyword">new</span> <span class="title class_">TransformingClassGenerator</span>(cg, transformer);</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 处理逻辑是清晰的，作用和影响不清楚</span></span><br><span class="line">    <span class="meta">@Override</span></span><br><span class="line">    <span class="keyword">public</span> <span class="type">byte</span>[] generate(ClassGenerator cg) <span class="keyword">throws</span> Exception &#123;</span><br><span class="line">        <span class="keyword">if</span> (<span class="built_in">this</span>.classLoader == <span class="literal">null</span>) &#123;</span><br><span class="line">            <span class="keyword">return</span> <span class="built_in">super</span>.generate(cg);</span><br><span class="line">        &#125;</span><br><span class="line"></span><br><span class="line">        <span class="type">Thread</span> <span class="variable">currentThread</span> <span class="operator">=</span> Thread.currentThread();</span><br><span class="line">        ClassLoader threadContextClassLoader;</span><br><span class="line">        <span class="keyword">try</span> &#123;</span><br><span class="line">            threadContextClassLoader = currentThread.getContextClassLoader();</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="keyword">catch</span> (Throwable ex) &#123;</span><br><span class="line">            <span class="comment">// Cannot access thread context ClassLoader - falling back...</span></span><br><span class="line">            <span class="keyword">return</span> <span class="built_in">super</span>.generate(cg);</span><br><span class="line">        &#125;</span><br><span class="line"></span><br><span class="line">        <span class="type">boolean</span> <span class="variable">overrideClassLoader</span> <span class="operator">=</span> !<span class="built_in">this</span>.classLoader.equals(threadContextClassLoader);</span><br><span class="line">        <span class="keyword">if</span> (overrideClassLoader) &#123;</span><br><span class="line">            currentThread.setContextClassLoader(<span class="built_in">this</span>.classLoader);</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="keyword">try</span> &#123;</span><br><span class="line">            <span class="keyword">return</span> <span class="built_in">super</span>.generate(cg);</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="keyword">finally</span> &#123;</span><br><span class="line">            <span class="keyword">if</span> (overrideClassLoader) &#123;</span><br><span class="line">                <span class="comment">// Reset original thread context ClassLoader.</span></span><br><span class="line">                currentThread.setContextClassLoader(threadContextClassLoader);</span><br><span class="line">            &#125;</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<h3 id="核心：拦截-Bean-方法"><a href="#核心：拦截-Bean-方法" class="headerlink" title="核心：拦截 @Bean 方法"></a>核心：拦截 @Bean 方法</h3><p><code>BeanMethodInterceptor</code> 实现了 <code>MethodInterceptor</code> 和 <code>ConditionalCallback</code> 接口。<code>isMatch</code> 匹配到被 <code>Bean</code> 注解标注的方法，则调用 <code>intercept</code> 方法。被 <code>Configuration</code> 注解标注的配置类，它定义的被 <code>Bean</code> 注解标注的方法，只会在第一次被调用时真正地执行并创建实例，后续不会再执行的“魔法”就在这里。即使你手动地调用配置类的方法，或是被 <code>Bean</code> 注解标注的方法间互相调用，都是如此。</p>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> Object <span class="title function_">intercept</span><span class="params">(Object enhancedConfigInstance, Method beanMethod, Object[] beanMethodArgs,</span></span><br><span class="line"><span class="params">            MethodProxy cglibMethodProxy)</span> <span class="keyword">throws</span> Throwable &#123;</span><br><span class="line">    <span class="comment">// 通过反射，获得 beanFactory 实例</span></span><br><span class="line">    <span class="type">ConfigurableBeanFactory</span> <span class="variable">beanFactory</span> <span class="operator">=</span> getBeanFactory(enhancedConfigInstance);</span><br><span class="line">    <span class="comment">// 获取 beanName，默认是方法名，可以自定义</span></span><br><span class="line">    <span class="type">String</span> <span class="variable">beanName</span> <span class="operator">=</span> BeanAnnotationHelper.determineBeanNameFor(beanMethod);</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 确定这个 bean 是否属于 scoped-proxy（不了解）</span></span><br><span class="line">    <span class="type">Scope</span> <span class="variable">scope</span> <span class="operator">=</span> AnnotatedElementUtils.findMergedAnnotation(beanMethod, Scope.class);</span><br><span class="line">    <span class="keyword">if</span> (scope != <span class="literal">null</span> &amp;&amp; scope.proxyMode() != ScopedProxyMode.NO) &#123;</span><br><span class="line">        <span class="type">String</span> <span class="variable">scopedBeanName</span> <span class="operator">=</span> ScopedProxyCreator.getTargetBeanName(beanName);</span><br><span class="line">        <span class="keyword">if</span> (beanFactory.isCurrentlyInCreation(scopedBeanName)) &#123;</span><br><span class="line">            beanName = scopedBeanName;</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// To handle the case of an inter-bean method reference, we must explicitly check the</span></span><br><span class="line">    <span class="comment">// container for already cached instances.</span></span><br><span class="line"></span><br><span class="line">    <span class="comment">// First, check to see if the requested bean is a FactoryBean. If so, create a subclass</span></span><br><span class="line">    <span class="comment">// proxy that intercepts calls to getObject() and returns any cached bean instance.</span></span><br><span class="line">    <span class="comment">// This ensures that the semantics of calling a FactoryBean from within @Bean methods</span></span><br><span class="line">    <span class="comment">// is the same as that of referring to a FactoryBean within XML. See SPR-6602.</span></span><br><span class="line">    <span class="keyword">if</span> (factoryContainsBean(beanFactory, BeanFactory.FACTORY_BEAN_PREFIX + beanName) &amp;&amp;</span><br><span class="line">            factoryContainsBean(beanFactory, beanName)) &#123;</span><br><span class="line">        <span class="type">Object</span> <span class="variable">factoryBean</span> <span class="operator">=</span> beanFactory.getBean(BeanFactory.FACTORY_BEAN_PREFIX + beanName);</span><br><span class="line">        <span class="keyword">if</span> (factoryBean <span class="keyword">instanceof</span> ScopedProxyFactoryBean) &#123;</span><br><span class="line">            <span class="comment">// Scoped proxy factory beans are a special case and should not be further proxied</span></span><br><span class="line">        &#125;</span><br><span class="line">        <span class="keyword">else</span> &#123;</span><br><span class="line">            <span class="comment">// It is a candidate FactoryBean - go ahead with enhancement</span></span><br><span class="line">            <span class="comment">// 处理 FactoryBean 类型</span></span><br><span class="line">            <span class="keyword">return</span> enhanceFactoryBean(factoryBean, beanMethod.getReturnType(), beanFactory, beanName);</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 检查 beanMethod 是不是当前正在被调用的 FactoryMethod</span></span><br><span class="line">    <span class="keyword">if</span> (isCurrentlyInvokedFactoryMethod(beanMethod)) &#123;</span><br><span class="line">        <span class="comment">// The factory is calling the bean method in order to instantiate and register the bean</span></span><br><span class="line">        <span class="comment">// (i.e. via a getBean() call) -&gt; invoke the super implementation of the method to actually</span></span><br><span class="line">        <span class="comment">// create the bean instance.</span></span><br><span class="line">        <span class="keyword">if</span> (logger.isWarnEnabled() &amp;&amp;</span><br><span class="line">                BeanFactoryPostProcessor.class.isAssignableFrom(beanMethod.getReturnType())) &#123;</span><br><span class="line">            logger.warn(String.format(<span class="string">&quot;@Bean method %s.%s is non-static and returns an object &quot;</span> +</span><br><span class="line">                            <span class="string">&quot;assignable to Spring&#x27;s BeanFactoryPostProcessor interface. This will &quot;</span> +</span><br><span class="line">                            <span class="string">&quot;result in a failure to process annotations such as @Autowired, &quot;</span> +</span><br><span class="line">                            <span class="string">&quot;@Resource and @PostConstruct within the method&#x27;s declaring &quot;</span> +</span><br><span class="line">                            <span class="string">&quot;@Configuration class. Add the &#x27;static&#x27; modifier to this method to avoid &quot;</span> +</span><br><span class="line">                            <span class="string">&quot;these container lifecycle issues; see @Bean javadoc for complete details.&quot;</span>,</span><br><span class="line">                    beanMethod.getDeclaringClass().getSimpleName(), beanMethod.getName()));</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="comment">// 调用实际的父类方法，创建 Bean 实例</span></span><br><span class="line">        <span class="keyword">return</span> cglibMethodProxy.invokeSuper(enhancedConfigInstance, beanMethodArgs);</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 从 BeanFactory 里获取</span></span><br><span class="line">    <span class="keyword">return</span> obtainBeanInstanceFromFactory(beanMethod, beanMethodArgs, beanFactory, beanName);</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<ol>
+<li><code>isCurrentlyInvokedFactoryMethod(beanMethod)</code> 检查 <code>beanMethod</code> 是不是当前正在被调用的 <code>FactoryMethod</code></li>
+<li>如果是，则调用实际的父类方法，创建 <code>Bean</code> 实例</li>
+<li>如果不是，则从 <code>BeanFactory</code> 中获取</li>
 </ol>
-<h2 id="参考文章"><a href="#参考文章" class="headerlink" title="参考文章"></a>参考文章</h2><ul>
-<li><a href="https://docs.k3s.io/zh/quick-start">快速入门指南</a></li>
-<li><a href="https://docs.k3s.io/zh/cli/server#%E7%AE%A1%E7%90%86-kubeconfig-%E9%80%89%E9%A1%B9">管理 Kubeconfig 选项</a></li>
-<li><a href="https://docs.k3s.io/zh/advanced#%E9%85%8D%E7%BD%AE-http-%E4%BB%A3%E7%90%86">配置 HTTP 代理</a></li>
-<li><a href="https://kubernetes.io/zh-cn/docs/tutorials/hello-minikube/">你好，Minikube</a></li>
-<li><a href="https://github.com/k3s-io/k3s/issues/7272">Permission denied on non-existing &#x2F;etc&#x2F;rancher&#x2F;k3s&#x2F;config.yaml after fresh install</a></li>
-<li><a href="https://devops.stackexchange.com/questions/16043/error-error-loading-config-file-etc-rancher-k3s-k3s-yaml-open-etc-rancher">error: error loading config file “&#x2F;etc&#x2F;rancher&#x2F;k3s&#x2F;k3s.yaml”: open &#x2F;etc&#x2F;rancher&#x2F;k3s&#x2F;k3s.yaml: permission denied</a></li>
-<li><a href="https://github.com/k3s-io/k3s/issues/389">&#x2F;etc&#x2F;rancher&#x2F;k3s&#x2F;k3s.yaml is world readable #389</a></li>
+<p>以本文示例进行说明。</p>
+<ol>
+<li>调用 <code>lisi()</code> 前，设置当前正在调用的 <code>FactoryMethod</code> 为 <code>lisi()</code><ol>
+<li>lisi() 调用被拦截后，查询获知当前正在调用的 <code>FactoryMethod</code> 确实是 <code>lisi()</code>，调用父类方法创建</li>
+</ol>
+</li>
+<li>调用 <code>person()</code> 前，设置当前正在调用的 <code>FactoryMethod</code> 为 <code>person()</code><ol>
+<li><code>person()</code> 调用被拦截后，查询获知当前正在调用的 <code>FactoryMethod</code> 确实是 <code>person()</code>，调用父类方法创建</li>
+<li>父类方法内调用了 <code>lisi()</code><ol>
+<li><code>lisi()</code> 调用被拦截后，查询获知当前正在调用的 <code>FactoryMethod</code> 是 <code>person()</code>，从 <code>BeanFactory</code> 中获取</li>
+<li>从 <code>BeanFactory</code> 中获取得到已经创建的 <code>lisi</code></li>
+</ol>
+</li>
+<li>继续创建并返回</li>
+</ol>
+</li>
+</ol>
+<p>以上处理的过程是比较清晰简单的，但是当前正在被调用的 <code>FactoryMethod</code> 是什么时候保存的，怎么处理的，还未明朗。</p>
+<h4 id="isCurrentlyInvokedFactoryMethod"><a href="#isCurrentlyInvokedFactoryMethod" class="headerlink" title="isCurrentlyInvokedFactoryMethod"></a>isCurrentlyInvokedFactoryMethod</h4><p>判断是否是当前正在被调用的 <code>FactoryMethod</code>。</p>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">private</span> <span class="type">boolean</span> <span class="title function_">isCurrentlyInvokedFactoryMethod</span><span class="params">(Method method)</span> &#123;</span><br><span class="line">    <span class="type">Method</span> <span class="variable">currentlyInvoked</span> <span class="operator">=</span> SimpleInstantiationStrategy.getCurrentlyInvokedFactoryMethod();</span><br><span class="line">    <span class="keyword">return</span> (currentlyInvoked != <span class="literal">null</span> &amp;&amp; method.getName().equals(currentlyInvoked.getName()) &amp;&amp;</span><br><span class="line">            Arrays.equals(method.getParameterTypes(), currentlyInvoked.getParameterTypes()));</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<p>原理是通过 <code>ThreadLocal</code> 记录正在调用的 <code>FactoryMethod</code>。</p>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">class</span> <span class="title class_">SimpleInstantiationStrategy</span> <span class="keyword">implements</span> <span class="title class_">InstantiationStrategy</span> &#123;</span><br><span class="line"></span><br><span class="line">	<span class="keyword">private</span> <span class="keyword">static</span> <span class="keyword">final</span> ThreadLocal&lt;Method&gt; currentlyInvokedFactoryMethod = <span class="keyword">new</span> <span class="title class_">ThreadLocal</span>&lt;Method&gt;();</span><br><span class="line"></span><br><span class="line">	<span class="comment">/**</span></span><br><span class="line"><span class="comment">	 * Return the factory method currently being invoked or &#123;<span class="doctag">@code</span> null&#125; if none.</span></span><br><span class="line"><span class="comment">	 * &lt;p&gt;Allows factory method implementations to determine whether the current</span></span><br><span class="line"><span class="comment">	 * caller is the container itself as opposed to user code.</span></span><br><span class="line"><span class="comment">	 */</span></span><br><span class="line">	<span class="keyword">public</span> <span class="keyword">static</span> Method <span class="title function_">getCurrentlyInvokedFactoryMethod</span><span class="params">()</span> &#123;</span><br><span class="line">		<span class="keyword">return</span> currentlyInvokedFactoryMethod.get();</span><br><span class="line">	&#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<p>这里只是通过 <code>get</code> 获取 <code>currentlyInvokedFactoryMethod</code> 的值，我们还不知道它是在哪更新的。</p>
+<h3 id="currentlyInvokedFactoryMethod-的“来龙去脉”"><a href="#currentlyInvokedFactoryMethod-的“来龙去脉”" class="headerlink" title="currentlyInvokedFactoryMethod 的“来龙去脉”"></a>currentlyInvokedFactoryMethod 的“来龙去脉”</h3><p>当 <code>BeanFactory</code> 创建 <code>Bean</code> 实例时，被 <code>Bean</code> 注解标注的方法注册的 <code>Bean</code> 在实例化时是使用工厂方法而不是构造器方法。</p>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">protected</span> BeanWrapper <span class="title function_">createBeanInstance</span><span class="params">(String beanName, RootBeanDefinition mbd, Object[] args)</span> &#123;</span><br><span class="line">    <span class="comment">// ...</span></span><br><span class="line">    <span class="keyword">if</span> (mbd.getFactoryMethodName() != <span class="literal">null</span>)  &#123;</span><br><span class="line">        <span class="comment">// 如果 FactoryMethodName 不为 null，则通过工厂方法实例化</span></span><br><span class="line">        <span class="keyword">return</span> instantiateUsingFactoryMethod(beanName, mbd, args);</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="comment">// ...</span></span><br><span class="line">&#125;</span><br><span class="line"></span><br><span class="line"><span class="keyword">protected</span> BeanWrapper <span class="title function_">instantiateUsingFactoryMethod</span><span class="params">(</span></span><br><span class="line"><span class="params">        String beanName, RootBeanDefinition mbd, Object[] explicitArgs)</span> &#123;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">return</span> <span class="keyword">new</span> <span class="title class_">ConstructorResolver</span>(<span class="built_in">this</span>).instantiateUsingFactoryMethod(beanName, mbd, explicitArgs);</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<p><code>BeanFactory</code> 委托给 <code>ConstructorResolver</code>。</p>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> BeanWrapper <span class="title function_">instantiateUsingFactoryMethod</span><span class="params">(</span></span><br><span class="line"><span class="params">		<span class="keyword">final</span> String beanName, <span class="keyword">final</span> RootBeanDefinition mbd, <span class="keyword">final</span> Object[] explicitArgs)</span> &#123;</span><br><span class="line">    <span class="comment">// ...</span></span><br><span class="line">    beanInstance = <span class="built_in">this</span>.beanFactory.getInstantiationStrategy().instantiate(</span><br><span class="line">			mbd, beanName, <span class="built_in">this</span>.beanFactory, factoryBean, factoryMethodToUse, argsToUse);</span><br><span class="line">    <span class="comment">// ...</span></span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<p><code>AbstractAutowireCapableBeanFactory</code> 的 <code>instantiationStrategy</code> 类型是 <code>CglibSubclassingInstantiationStrategy</code>，继承自 <code>SimpleInstantiationStrategy</code>。</p>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">private</span> <span class="type">InstantiationStrategy</span> <span class="variable">instantiationStrategy</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">CglibSubclassingInstantiationStrategy</span>();</span><br></pre></td></tr></table></figure>
+
+<p><code>SimpleInstantiationStrategy</code> 的 <code>instantiate</code> 方法在通过反射调用 <code>factoryBean</code> 对应的 <code>method</code> 前后，会处理 <code>currentlyInvokedFactoryMethod</code> 的值。</p>
+<blockquote>
+<p>被 <code>Bean</code> 注解标注的方法，对应的 <code>Bean</code> 就是一个 <code>FactoryBean</code>。</p>
+</blockquote>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">class</span> <span class="title class_">SimpleInstantiationStrategy</span> <span class="keyword">implements</span> <span class="title class_">InstantiationStrategy</span> &#123;</span><br><span class="line">    <span class="comment">// ...</span></span><br><span class="line">    <span class="meta">@Override</span></span><br><span class="line">    <span class="keyword">public</span> Object <span class="title function_">instantiate</span><span class="params">(RootBeanDefinition bd, String beanName, BeanFactory owner,</span></span><br><span class="line"><span class="params">            Object factoryBean, <span class="keyword">final</span> Method factoryMethod, Object... args)</span> &#123;</span><br><span class="line">        <span class="keyword">try</span> &#123;</span><br><span class="line">            <span class="keyword">if</span> (System.getSecurityManager() != <span class="literal">null</span>) &#123;</span><br><span class="line">                AccessController.doPrivileged(<span class="keyword">new</span> <span class="title class_">PrivilegedAction</span>&lt;Object&gt;() &#123;</span><br><span class="line">                    <span class="meta">@Override</span></span><br><span class="line">                    <span class="keyword">public</span> Object <span class="title function_">run</span><span class="params">()</span> &#123;</span><br><span class="line">                        ReflectionUtils.makeAccessible(factoryMethod);</span><br><span class="line">                        <span class="keyword">return</span> <span class="literal">null</span>;</span><br><span class="line">                    &#125;</span><br><span class="line">                &#125;);</span><br><span class="line">            &#125;</span><br><span class="line">            <span class="keyword">else</span> &#123;</span><br><span class="line">                ReflectionUtils.makeAccessible(factoryMethod);</span><br><span class="line">            &#125;</span><br><span class="line">            </span><br><span class="line">            <span class="comment">// 获取之前正在被调用的 FactoryMethod</span></span><br><span class="line">            <span class="type">Method</span> <span class="variable">priorInvokedFactoryMethod</span> <span class="operator">=</span> currentlyInvokedFactoryMethod.get();</span><br><span class="line">            <span class="keyword">try</span> &#123;</span><br><span class="line">                <span class="comment">// 将当前正在被调用的 FactoryMethod 保存</span></span><br><span class="line">                currentlyInvokedFactoryMethod.set(factoryMethod);</span><br><span class="line">                <span class="comment">// 调用 FactoryMethod</span></span><br><span class="line">                <span class="keyword">return</span> factoryMethod.invoke(factoryBean, args);</span><br><span class="line">            &#125;</span><br><span class="line">            <span class="keyword">finally</span> &#123;</span><br><span class="line">                <span class="keyword">if</span> (priorInvokedFactoryMethod != <span class="literal">null</span>) &#123;</span><br><span class="line">                    <span class="comment">// 如果之前正在被调用的 FactoryMethod 不为 null，复原</span></span><br><span class="line">                    currentlyInvokedFactoryMethod.set(priorInvokedFactoryMethod);</span><br><span class="line">                &#125;</span><br><span class="line">                <span class="keyword">else</span> &#123;</span><br><span class="line">                    <span class="comment">// 否则移除</span></span><br><span class="line">                    currentlyInvokedFactoryMethod.remove();</span><br><span class="line">                &#125;</span><br><span class="line">            &#125;</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="keyword">catch</span> (IllegalArgumentException ex) &#123;</span><br><span class="line">            <span class="keyword">throw</span> <span class="keyword">new</span> <span class="title class_">BeanInstantiationException</span>(factoryMethod,</span><br><span class="line">                    <span class="string">&quot;Illegal arguments to factory method &#x27;&quot;</span> + factoryMethod.getName() + <span class="string">&quot;&#x27;; &quot;</span> +</span><br><span class="line">                    <span class="string">&quot;args: &quot;</span> + StringUtils.arrayToCommaDelimitedString(args), ex);</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="keyword">catch</span> (IllegalAccessException ex) &#123;</span><br><span class="line">            <span class="keyword">throw</span> <span class="keyword">new</span> <span class="title class_">BeanInstantiationException</span>(factoryMethod,</span><br><span class="line">                    <span class="string">&quot;Cannot access factory method &#x27;&quot;</span> + factoryMethod.getName() + <span class="string">&quot;&#x27;; is it public?&quot;</span>, ex);</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="keyword">catch</span> (InvocationTargetException ex) &#123;</span><br><span class="line">            <span class="type">String</span> <span class="variable">msg</span> <span class="operator">=</span> <span class="string">&quot;Factory method &#x27;&quot;</span> + factoryMethod.getName() + <span class="string">&quot;&#x27; threw exception&quot;</span>;</span><br><span class="line">            <span class="keyword">if</span> (bd.getFactoryBeanName() != <span class="literal">null</span> &amp;&amp; owner <span class="keyword">instanceof</span> ConfigurableBeanFactory &amp;&amp;</span><br><span class="line">                    ((ConfigurableBeanFactory) owner).isCurrentlyInCreation(bd.getFactoryBeanName())) &#123;</span><br><span class="line">                msg = <span class="string">&quot;Circular reference involving containing bean &#x27;&quot;</span> + bd.getFactoryBeanName() + <span class="string">&quot;&#x27; - consider &quot;</span> +</span><br><span class="line">                    <span class="string">&quot;declaring the factory method as static for independence from its containing instance. &quot;</span> + msg;</span><br><span class="line">            &#125;</span><br><span class="line">            <span class="keyword">throw</span> <span class="keyword">new</span> <span class="title class_">BeanInstantiationException</span>(factoryMethod, msg, ex.getTargetException());</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<h3 id="从-BeanFactory-获取-Bean"><a href="#从-BeanFactory-获取-Bean" class="headerlink" title="从 BeanFactory 获取 Bean"></a>从 BeanFactory 获取 Bean</h3><figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">private</span> Object <span class="title function_">obtainBeanInstanceFromFactory</span><span class="params">(Method beanMethod, Object[] beanMethodArgs,</span></span><br><span class="line"><span class="params">        ConfigurableBeanFactory beanFactory, String beanName)</span> &#123;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// bean 可能已经在创建中</span></span><br><span class="line">    <span class="type">boolean</span> <span class="variable">alreadyInCreation</span> <span class="operator">=</span> beanFactory.isCurrentlyInCreation(beanName);</span><br><span class="line">    <span class="keyword">try</span> &#123;</span><br><span class="line">        <span class="keyword">if</span> (alreadyInCreation) &#123;</span><br><span class="line">            <span class="comment">// 暂时添加到 inCreationCheckExclusions，不再检查是否在创建中</span></span><br><span class="line">            beanFactory.setCurrentlyInCreation(beanName, <span class="literal">false</span>);</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="type">boolean</span> <span class="variable">useArgs</span> <span class="operator">=</span> !ObjectUtils.isEmpty(beanMethodArgs);</span><br><span class="line">        <span class="keyword">if</span> (useArgs &amp;&amp; beanFactory.isSingleton(beanName)) &#123;</span><br><span class="line">            <span class="comment">// 检查参数是否存在 null</span></span><br><span class="line">            <span class="keyword">for</span> (Object arg : beanMethodArgs) &#123;</span><br><span class="line">                <span class="keyword">if</span> (arg == <span class="literal">null</span>) &#123;</span><br><span class="line">                    useArgs = <span class="literal">false</span>;</span><br><span class="line">                    <span class="keyword">break</span>;</span><br><span class="line">                &#125;</span><br><span class="line">            &#125;</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="comment">// 从 beanFactory 获取 Bean</span></span><br><span class="line">        <span class="type">Object</span> <span class="variable">beanInstance</span> <span class="operator">=</span> (useArgs ? beanFactory.getBean(beanName, beanMethodArgs) :</span><br><span class="line">                beanFactory.getBean(beanName));</span><br><span class="line">        <span class="keyword">if</span> (beanInstance != <span class="literal">null</span> &amp;&amp; !ClassUtils.isAssignableValue(beanMethod.getReturnType(), beanInstance)) &#123;</span><br><span class="line">            <span class="type">String</span> <span class="variable">msg</span> <span class="operator">=</span> String.format(<span class="string">&quot;@Bean method %s.%s called as a bean reference &quot;</span> +</span><br><span class="line">                        <span class="string">&quot;for type [%s] but overridden by non-compatible bean instance of type [%s].&quot;</span>,</span><br><span class="line">                        beanMethod.getDeclaringClass().getSimpleName(), beanMethod.getName(),</span><br><span class="line">                        beanMethod.getReturnType().getName(), beanInstance.getClass().getName());</span><br><span class="line">            <span class="keyword">try</span> &#123;</span><br><span class="line">                <span class="type">BeanDefinition</span> <span class="variable">beanDefinition</span> <span class="operator">=</span> beanFactory.getMergedBeanDefinition(beanName);</span><br><span class="line">                msg += <span class="string">&quot; Overriding bean of same name declared in: &quot;</span> + beanDefinition.getResourceDescription();</span><br><span class="line">            &#125;</span><br><span class="line">            <span class="keyword">catch</span> (NoSuchBeanDefinitionException ex) &#123;</span><br><span class="line">                <span class="comment">// Ignore - simply no detailed message then.</span></span><br><span class="line">            &#125;</span><br><span class="line">            <span class="keyword">throw</span> <span class="keyword">new</span> <span class="title class_">IllegalStateException</span>(msg);</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="comment">// 注册依赖关系</span></span><br><span class="line">        <span class="type">Method</span> <span class="variable">currentlyInvoked</span> <span class="operator">=</span> SimpleInstantiationStrategy.getCurrentlyInvokedFactoryMethod();</span><br><span class="line">        <span class="keyword">if</span> (currentlyInvoked != <span class="literal">null</span>) &#123;</span><br><span class="line">            <span class="type">String</span> <span class="variable">outerBeanName</span> <span class="operator">=</span> BeanAnnotationHelper.determineBeanNameFor(currentlyInvoked);</span><br><span class="line">            beanFactory.registerDependentBean(beanName, outerBeanName);</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="keyword">return</span> beanInstance;</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="keyword">finally</span> &#123;</span><br><span class="line">        <span class="keyword">if</span> (alreadyInCreation) &#123;</span><br><span class="line">            <span class="comment">// 复原状态</span></span><br><span class="line">            beanFactory.setCurrentlyInCreation(beanName, <span class="literal">true</span>);</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<p>延续自本文的文章：</p>
+<ul>
+<li><a href="/2023/12/11/the-truth-about-override-of-ComponentScan-basePackages/" title="ComponentScan 扫描路径覆盖的真相">ComponentScan 扫描路径覆盖的真相</a></li>
+<li><a href="/2023/12/04/use-and-analysis-of-Import-annotation-in-Spring/" title="Spring 中 @Import 注解的使用和源码分析">Spring 中 @Import 注解的使用和源码分析</a></li>
 </ul>
 ]]></content>
       <tags>
-        <tag>k8s</tag>
-        <tag>k3s</tag>
+        <tag>java</tag>
+        <tag>spring</tag>
       </tags>
   </entry>
 </search>
diff --git a/tags/aop/index.html b/tags/aop/index.html
index 1626c021..7d1dc507 100644
--- a/tags/aop/index.html
+++ b/tags/aop/index.html
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   <nav class="site-state">
       <div class="site-state-item site-state-posts">
         <a href="/archives/">
-          <span class="site-state-item-count">48</span>
+          <span class="site-state-item-count">49</span>
           <span class="site-state-item-name">日志</span>
         </a>
       </div>
@@ -242,13 +242,13 @@ <h1 class="collection-header">aop
     <span class="post-meta-item-icon">
       <i class="fa fa-chart-line"></i>
     </span>
-    <span title="站点总字数">125k</span>
+    <span title="站点总字数">129k</span>
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       <i class="fa fa-coffee"></i>
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-    <span title="站点阅读时长">6:56</span>
+    <span title="站点阅读时长">7:09</span>
   </span>
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   <div class="powered-by">由 <a href="https://hexo.io/" rel="noopener" target="_blank">Hexo</a> & <a href="https://theme-next.js.org/" rel="noopener" target="_blank">NexT.Gemini</a> 强力驱动
diff --git a/tags/auto-configuration/index.html b/tags/auto-configuration/index.html
index da0b3bfa..6f1a4645 100644
--- a/tags/auto-configuration/index.html
+++ b/tags/auto-configuration/index.html
@@ -151,7 +151,7 @@
   <nav class="site-state">
       <div class="site-state-item site-state-posts">
         <a href="/archives/">
-          <span class="site-state-item-count">48</span>
+          <span class="site-state-item-count">49</span>
           <span class="site-state-item-name">日志</span>
         </a>
       </div>
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     <span class="post-meta-item-icon">
       <i class="fa fa-chart-line"></i>
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-    <span title="站点总字数">125k</span>
+    <span title="站点总字数">129k</span>
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     <span class="post-meta-item-icon">
       <i class="fa fa-coffee"></i>
     </span>
-    <span title="站点阅读时长">6:56</span>
+    <span title="站点阅读时长">7:09</span>
   </span>
 </div>
   <div class="powered-by">由 <a href="https://hexo.io/" rel="noopener" target="_blank">Hexo</a> & <a href="https://theme-next.js.org/" rel="noopener" target="_blank">NexT.Gemini</a> 强力驱动
diff --git a/tags/bytecode/index.html b/tags/bytecode/index.html
index 33392fb8..05feb6af 100644
--- a/tags/bytecode/index.html
+++ b/tags/bytecode/index.html
@@ -151,7 +151,7 @@
   <nav class="site-state">
       <div class="site-state-item site-state-posts">
         <a href="/archives/">
-          <span class="site-state-item-count">48</span>
+          <span class="site-state-item-count">49</span>
           <span class="site-state-item-name">日志</span>
         </a>
       </div>
@@ -242,13 +242,13 @@ <h1 class="collection-header">bytecode
     <span class="post-meta-item-icon">
       <i class="fa fa-chart-line"></i>
     </span>
-    <span title="站点总字数">125k</span>
+    <span title="站点总字数">129k</span>
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     <span class="post-meta-item-icon">
       <i class="fa fa-coffee"></i>
     </span>
-    <span title="站点阅读时长">6:56</span>
+    <span title="站点阅读时长">7:09</span>
   </span>
 </div>
   <div class="powered-by">由 <a href="https://hexo.io/" rel="noopener" target="_blank">Hexo</a> & <a href="https://theme-next.js.org/" rel="noopener" target="_blank">NexT.Gemini</a> 强力驱动
diff --git a/tags/cglib/index.html b/tags/cglib/index.html
index 5473f698..23ac5a63 100644
--- a/tags/cglib/index.html
+++ b/tags/cglib/index.html
@@ -151,7 +151,7 @@
   <nav class="site-state">
       <div class="site-state-item site-state-posts">
         <a href="/archives/">
-          <span class="site-state-item-count">48</span>
+          <span class="site-state-item-count">49</span>
           <span class="site-state-item-name">日志</span>
         </a>
       </div>
@@ -242,13 +242,13 @@ <h1 class="collection-header">cglib
     <span class="post-meta-item-icon">
       <i class="fa fa-chart-line"></i>
     </span>
-    <span title="站点总字数">125k</span>
+    <span title="站点总字数">129k</span>
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     <span class="post-meta-item-icon">
       <i class="fa fa-coffee"></i>
     </span>
-    <span title="站点阅读时长">6:56</span>
+    <span title="站点阅读时长">7:09</span>
   </span>
 </div>
   <div class="powered-by">由 <a href="https://hexo.io/" rel="noopener" target="_blank">Hexo</a> & <a href="https://theme-next.js.org/" rel="noopener" target="_blank">NexT.Gemini</a> 强力驱动
diff --git a/tags/clash/index.html b/tags/clash/index.html
index 44dd5020..89509669 100644
--- a/tags/clash/index.html
+++ b/tags/clash/index.html
@@ -151,7 +151,7 @@
   <nav class="site-state">
       <div class="site-state-item site-state-posts">
         <a href="/archives/">
-          <span class="site-state-item-count">48</span>
+          <span class="site-state-item-count">49</span>
           <span class="site-state-item-name">日志</span>
         </a>
       </div>
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     <span class="post-meta-item-icon">
       <i class="fa fa-chart-line"></i>
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-    <span title="站点总字数">125k</span>
+    <span title="站点总字数">129k</span>
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       <i class="fa fa-coffee"></i>
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-    <span title="站点阅读时长">6:56</span>
+    <span title="站点阅读时长">7:09</span>
   </span>
 </div>
   <div class="powered-by">由 <a href="https://hexo.io/" rel="noopener" target="_blank">Hexo</a> & <a href="https://theme-next.js.org/" rel="noopener" target="_blank">NexT.Gemini</a> 强力驱动
diff --git a/tags/class-loader/index.html b/tags/class-loader/index.html
index f5c9fe32..21b38236 100644
--- a/tags/class-loader/index.html
+++ b/tags/class-loader/index.html
@@ -151,7 +151,7 @@
   <nav class="site-state">
       <div class="site-state-item site-state-posts">
         <a href="/archives/">
-          <span class="site-state-item-count">48</span>
+          <span class="site-state-item-count">49</span>
           <span class="site-state-item-name">日志</span>
         </a>
       </div>
@@ -242,13 +242,13 @@ <h1 class="collection-header">class loader
     <span class="post-meta-item-icon">
       <i class="fa fa-chart-line"></i>
     </span>
-    <span title="站点总字数">125k</span>
+    <span title="站点总字数">129k</span>
   </span>
   <span class="post-meta-item">
     <span class="post-meta-item-icon">
       <i class="fa fa-coffee"></i>
     </span>
-    <span title="站点阅读时长">6:56</span>
+    <span title="站点阅读时长">7:09</span>
   </span>
 </div>
   <div class="powered-by">由 <a href="https://hexo.io/" rel="noopener" target="_blank">Hexo</a> & <a href="https://theme-next.js.org/" rel="noopener" target="_blank">NexT.Gemini</a> 强力驱动
diff --git a/tags/distributed-lock/index.html b/tags/distributed-lock/index.html
index 23efbf21..fd808dac 100644
--- a/tags/distributed-lock/index.html
+++ b/tags/distributed-lock/index.html
@@ -151,7 +151,7 @@
   <nav class="site-state">
       <div class="site-state-item site-state-posts">
         <a href="/archives/">
-          <span class="site-state-item-count">48</span>
+          <span class="site-state-item-count">49</span>
           <span class="site-state-item-name">日志</span>
         </a>
       </div>
@@ -242,13 +242,13 @@ <h1 class="collection-header">distributed lock
     <span class="post-meta-item-icon">
       <i class="fa fa-chart-line"></i>
     </span>
-    <span title="站点总字数">125k</span>
+    <span title="站点总字数">129k</span>
   </span>
   <span class="post-meta-item">
     <span class="post-meta-item-icon">
       <i class="fa fa-coffee"></i>
     </span>
-    <span title="站点阅读时长">6:56</span>
+    <span title="站点阅读时长">7:09</span>
   </span>
 </div>
   <div class="powered-by">由 <a href="https://hexo.io/" rel="noopener" target="_blank">Hexo</a> & <a href="https://theme-next.js.org/" rel="noopener" target="_blank">NexT.Gemini</a> 强力驱动
diff --git a/tags/docker/index.html b/tags/docker/index.html
index 7fd23eae..b79359c2 100644
--- a/tags/docker/index.html
+++ b/tags/docker/index.html
@@ -151,7 +151,7 @@
   <nav class="site-state">
       <div class="site-state-item site-state-posts">
         <a href="/archives/">
-          <span class="site-state-item-count">48</span>
+          <span class="site-state-item-count">49</span>
           <span class="site-state-item-name">日志</span>
         </a>
       </div>
@@ -325,13 +325,13 @@ <h1 class="collection-header">docker
     <span class="post-meta-item-icon">
       <i class="fa fa-chart-line"></i>
     </span>
-    <span title="站点总字数">125k</span>
+    <span title="站点总字数">129k</span>
   </span>
   <span class="post-meta-item">
     <span class="post-meta-item-icon">
       <i class="fa fa-coffee"></i>
     </span>
-    <span title="站点阅读时长">6:56</span>
+    <span title="站点阅读时长">7:09</span>
   </span>
 </div>
   <div class="powered-by">由 <a href="https://hexo.io/" rel="noopener" target="_blank">Hexo</a> & <a href="https://theme-next.js.org/" rel="noopener" target="_blank">NexT.Gemini</a> 强力驱动
diff --git a/tags/dubbo/index.html b/tags/dubbo/index.html
index c77b433f..cf162020 100644
--- a/tags/dubbo/index.html
+++ b/tags/dubbo/index.html
@@ -151,7 +151,7 @@
   <nav class="site-state">
       <div class="site-state-item site-state-posts">
         <a href="/archives/">
-          <span class="site-state-item-count">48</span>
+          <span class="site-state-item-count">49</span>
           <span class="site-state-item-name">日志</span>
         </a>
       </div>
@@ -262,13 +262,13 @@ <h1 class="collection-header">dubbo
     <span class="post-meta-item-icon">
       <i class="fa fa-chart-line"></i>
     </span>
-    <span title="站点总字数">125k</span>
+    <span title="站点总字数">129k</span>
   </span>
   <span class="post-meta-item">
     <span class="post-meta-item-icon">
       <i class="fa fa-coffee"></i>
     </span>
-    <span title="站点阅读时长">6:56</span>
+    <span title="站点阅读时长">7:09</span>
   </span>
 </div>
   <div class="powered-by">由 <a href="https://hexo.io/" rel="noopener" target="_blank">Hexo</a> & <a href="https://theme-next.js.org/" rel="noopener" target="_blank">NexT.Gemini</a> 强力驱动
diff --git a/tags/elasticsearch/index.html b/tags/elasticsearch/index.html
index 09b0d7ac..29cca918 100644
--- a/tags/elasticsearch/index.html
+++ b/tags/elasticsearch/index.html
@@ -151,7 +151,7 @@
   <nav class="site-state">
       <div class="site-state-item site-state-posts">
         <a href="/archives/">
-          <span class="site-state-item-count">48</span>
+          <span class="site-state-item-count">49</span>
           <span class="site-state-item-name">日志</span>
         </a>
       </div>
@@ -242,13 +242,13 @@ <h1 class="collection-header">elasticsearch
     <span class="post-meta-item-icon">
       <i class="fa fa-chart-line"></i>
     </span>
-    <span title="站点总字数">125k</span>
+    <span title="站点总字数">129k</span>
   </span>
   <span class="post-meta-item">
     <span class="post-meta-item-icon">
       <i class="fa fa-coffee"></i>
     </span>
-    <span title="站点阅读时长">6:56</span>
+    <span title="站点阅读时长">7:09</span>
   </span>
 </div>
   <div class="powered-by">由 <a href="https://hexo.io/" rel="noopener" target="_blank">Hexo</a> & <a href="https://theme-next.js.org/" rel="noopener" target="_blank">NexT.Gemini</a> 强力驱动
diff --git a/tags/grafana/index.html b/tags/grafana/index.html
index 4e863db5..7802fc4d 100644
--- a/tags/grafana/index.html
+++ b/tags/grafana/index.html
@@ -151,7 +151,7 @@
   <nav class="site-state">
       <div class="site-state-item site-state-posts">
         <a href="/archives/">
-          <span class="site-state-item-count">48</span>
+          <span class="site-state-item-count">49</span>
           <span class="site-state-item-name">日志</span>
         </a>
       </div>
@@ -242,13 +242,13 @@ <h1 class="collection-header">grafana
     <span class="post-meta-item-icon">
       <i class="fa fa-chart-line"></i>
     </span>
-    <span title="站点总字数">125k</span>
+    <span title="站点总字数">129k</span>
   </span>
   <span class="post-meta-item">
     <span class="post-meta-item-icon">
       <i class="fa fa-coffee"></i>
     </span>
-    <span title="站点阅读时长">6:56</span>
+    <span title="站点阅读时长">7:09</span>
   </span>
 </div>
   <div class="powered-by">由 <a href="https://hexo.io/" rel="noopener" target="_blank">Hexo</a> & <a href="https://theme-next.js.org/" rel="noopener" target="_blank">NexT.Gemini</a> 强力驱动
diff --git a/tags/index.html b/tags/index.html
index 5ee43efb..70cd8b20 100644
--- a/tags/index.html
+++ b/tags/index.html
@@ -27,7 +27,7 @@
 <meta property="og:description" content="假如生命只剩一天">
 <meta property="og:locale" content="zh_CN">
 <meta property="article:published_time" content="2023-06-19T11:28:34.000Z">
-<meta property="article:modified_time" content="2024-04-10T14:49:47.895Z">
+<meta property="article:modified_time" content="2024-04-23T18:42:37.635Z">
 <meta property="article:author" content="Moralok">
 <meta name="twitter:card" content="summary">
 
@@ -154,7 +154,7 @@
   <nav class="site-state">
       <div class="site-state-item site-state-posts">
         <a href="/archives/">
-          <span class="site-state-item-count">48</span>
+          <span class="site-state-item-count">49</span>
           <span class="site-state-item-name">日志</span>
         </a>
       </div>
@@ -237,13 +237,13 @@ <h1 class="post-title" itemprop="name headline">tags
     <span class="post-meta-item-icon">
       <i class="fa fa-chart-line"></i>
     </span>
-    <span title="站点总字数">125k</span>
+    <span title="站点总字数">129k</span>
   </span>
   <span class="post-meta-item">
     <span class="post-meta-item-icon">
       <i class="fa fa-coffee"></i>
     </span>
-    <span title="站点阅读时长">6:56</span>
+    <span title="站点阅读时长">7:09</span>
   </span>
 </div>
   <div class="powered-by">由 <a href="https://hexo.io/" rel="noopener" target="_blank">Hexo</a> & <a href="https://theme-next.js.org/" rel="noopener" target="_blank">NexT.Gemini</a> 强力驱动
diff --git a/tags/java/index.html b/tags/java/index.html
index 937d0734..83bfccca 100644
--- a/tags/java/index.html
+++ b/tags/java/index.html
@@ -151,7 +151,7 @@
   <nav class="site-state">
       <div class="site-state-item site-state-posts">
         <a href="/archives/">
-          <span class="site-state-item-count">48</span>
+          <span class="site-state-item-count">49</span>
           <span class="site-state-item-name">日志</span>
         </a>
       </div>
@@ -425,13 +425,13 @@ <h1 class="collection-header">java
     <span class="post-meta-item-icon">
       <i class="fa fa-chart-line"></i>
     </span>
-    <span title="站点总字数">125k</span>
+    <span title="站点总字数">129k</span>
   </span>
   <span class="post-meta-item">
     <span class="post-meta-item-icon">
       <i class="fa fa-coffee"></i>
     </span>
-    <span title="站点阅读时长">6:56</span>
+    <span title="站点阅读时长">7:09</span>
   </span>
 </div>
   <div class="powered-by">由 <a href="https://hexo.io/" rel="noopener" target="_blank">Hexo</a> & <a href="https://theme-next.js.org/" rel="noopener" target="_blank">NexT.Gemini</a> 强力驱动
diff --git a/tags/java/page/2/index.html b/tags/java/page/2/index.html
index 68393a21..d67d33af 100644
--- a/tags/java/page/2/index.html
+++ b/tags/java/page/2/index.html
@@ -151,7 +151,7 @@
   <nav class="site-state">
       <div class="site-state-item site-state-posts">
         <a href="/archives/">
-          <span class="site-state-item-count">48</span>
+          <span class="site-state-item-count">49</span>
           <span class="site-state-item-name">日志</span>
         </a>
       </div>
@@ -425,13 +425,13 @@ <h1 class="collection-header">java
     <span class="post-meta-item-icon">
       <i class="fa fa-chart-line"></i>
     </span>
-    <span title="站点总字数">125k</span>
+    <span title="站点总字数">129k</span>
   </span>
   <span class="post-meta-item">
     <span class="post-meta-item-icon">
       <i class="fa fa-coffee"></i>
     </span>
-    <span title="站点阅读时长">6:56</span>
+    <span title="站点阅读时长">7:09</span>
   </span>
 </div>
   <div class="powered-by">由 <a href="https://hexo.io/" rel="noopener" target="_blank">Hexo</a> & <a href="https://theme-next.js.org/" rel="noopener" target="_blank">NexT.Gemini</a> 强力驱动
diff --git a/tags/java/page/3/index.html b/tags/java/page/3/index.html
index f38e38d1..daecf144 100644
--- a/tags/java/page/3/index.html
+++ b/tags/java/page/3/index.html
@@ -151,7 +151,7 @@
   <nav class="site-state">
       <div class="site-state-item site-state-posts">
         <a href="/archives/">
-          <span class="site-state-item-count">48</span>
+          <span class="site-state-item-count">49</span>
           <span class="site-state-item-name">日志</span>
         </a>
       </div>
@@ -305,13 +305,13 @@ <h1 class="collection-header">java
     <span class="post-meta-item-icon">
       <i class="fa fa-chart-line"></i>
     </span>
-    <span title="站点总字数">125k</span>
+    <span title="站点总字数">129k</span>
   </span>
   <span class="post-meta-item">
     <span class="post-meta-item-icon">
       <i class="fa fa-coffee"></i>
     </span>
-    <span title="站点阅读时长">6:56</span>
+    <span title="站点阅读时长">7:09</span>
   </span>
 </div>
   <div class="powered-by">由 <a href="https://hexo.io/" rel="noopener" target="_blank">Hexo</a> & <a href="https://theme-next.js.org/" rel="noopener" target="_blank">NexT.Gemini</a> 强力驱动
diff --git a/tags/jdk-proxy/index.html b/tags/jdk-proxy/index.html
index 0fe82a65..3aec00d1 100644
--- a/tags/jdk-proxy/index.html
+++ b/tags/jdk-proxy/index.html
@@ -151,7 +151,7 @@
   <nav class="site-state">
       <div class="site-state-item site-state-posts">
         <a href="/archives/">
-          <span class="site-state-item-count">48</span>
+          <span class="site-state-item-count">49</span>
           <span class="site-state-item-name">日志</span>
         </a>
       </div>
@@ -242,13 +242,13 @@ <h1 class="collection-header">jdk proxy
     <span class="post-meta-item-icon">
       <i class="fa fa-chart-line"></i>
     </span>
-    <span title="站点总字数">125k</span>
+    <span title="站点总字数">129k</span>
   </span>
   <span class="post-meta-item">
     <span class="post-meta-item-icon">
       <i class="fa fa-coffee"></i>
     </span>
-    <span title="站点阅读时长">6:56</span>
+    <span title="站点阅读时长">7:09</span>
   </span>
 </div>
   <div class="powered-by">由 <a href="https://hexo.io/" rel="noopener" target="_blank">Hexo</a> & <a href="https://theme-next.js.org/" rel="noopener" target="_blank">NexT.Gemini</a> 强力驱动
diff --git a/tags/jvm/index.html b/tags/jvm/index.html
index 3e2c7a24..c40dac7f 100644
--- a/tags/jvm/index.html
+++ b/tags/jvm/index.html
@@ -151,7 +151,7 @@
   <nav class="site-state">
       <div class="site-state-item site-state-posts">
         <a href="/archives/">
-          <span class="site-state-item-count">48</span>
+          <span class="site-state-item-count">49</span>
           <span class="site-state-item-name">日志</span>
         </a>
       </div>
@@ -302,13 +302,13 @@ <h1 class="collection-header">jvm
     <span class="post-meta-item-icon">
       <i class="fa fa-chart-line"></i>
     </span>
-    <span title="站点总字数">125k</span>
+    <span title="站点总字数">129k</span>
   </span>
   <span class="post-meta-item">
     <span class="post-meta-item-icon">
       <i class="fa fa-coffee"></i>
     </span>
-    <span title="站点阅读时长">6:56</span>
+    <span title="站点阅读时长">7:09</span>
   </span>
 </div>
   <div class="powered-by">由 <a href="https://hexo.io/" rel="noopener" target="_blank">Hexo</a> & <a href="https://theme-next.js.org/" rel="noopener" target="_blank">NexT.Gemini</a> 强力驱动
diff --git a/tags/k3s/index.html b/tags/k3s/index.html
index 79f43e58..3e28ce83 100644
--- a/tags/k3s/index.html
+++ b/tags/k3s/index.html
@@ -151,7 +151,7 @@
   <nav class="site-state">
       <div class="site-state-item site-state-posts">
         <a href="/archives/">
-          <span class="site-state-item-count">48</span>
+          <span class="site-state-item-count">49</span>
           <span class="site-state-item-name">日志</span>
         </a>
       </div>
@@ -242,13 +242,13 @@ <h1 class="collection-header">k3s
     <span class="post-meta-item-icon">
       <i class="fa fa-chart-line"></i>
     </span>
-    <span title="站点总字数">125k</span>
+    <span title="站点总字数">129k</span>
   </span>
   <span class="post-meta-item">
     <span class="post-meta-item-icon">
       <i class="fa fa-coffee"></i>
     </span>
-    <span title="站点阅读时长">6:56</span>
+    <span title="站点阅读时长">7:09</span>
   </span>
 </div>
   <div class="powered-by">由 <a href="https://hexo.io/" rel="noopener" target="_blank">Hexo</a> & <a href="https://theme-next.js.org/" rel="noopener" target="_blank">NexT.Gemini</a> 强力驱动
diff --git a/tags/k8s/index.html b/tags/k8s/index.html
index 7b98fd3d..3ba60ca3 100644
--- a/tags/k8s/index.html
+++ b/tags/k8s/index.html
@@ -151,7 +151,7 @@
   <nav class="site-state">
       <div class="site-state-item site-state-posts">
         <a href="/archives/">
-          <span class="site-state-item-count">48</span>
+          <span class="site-state-item-count">49</span>
           <span class="site-state-item-name">日志</span>
         </a>
       </div>
@@ -265,13 +265,13 @@ <h1 class="collection-header">k8s
     <span class="post-meta-item-icon">
       <i class="fa fa-chart-line"></i>
     </span>
-    <span title="站点总字数">125k</span>
+    <span title="站点总字数">129k</span>
   </span>
   <span class="post-meta-item">
     <span class="post-meta-item-icon">
       <i class="fa fa-coffee"></i>
     </span>
-    <span title="站点阅读时长">6:56</span>
+    <span title="站点阅读时长">7:09</span>
   </span>
 </div>
   <div class="powered-by">由 <a href="https://hexo.io/" rel="noopener" target="_blank">Hexo</a> & <a href="https://theme-next.js.org/" rel="noopener" target="_blank">NexT.Gemini</a> 强力驱动
diff --git a/tags/kibana/index.html b/tags/kibana/index.html
index 77adb861..eb0ee0b9 100644
--- a/tags/kibana/index.html
+++ b/tags/kibana/index.html
@@ -151,7 +151,7 @@
   <nav class="site-state">
       <div class="site-state-item site-state-posts">
         <a href="/archives/">
-          <span class="site-state-item-count">48</span>
+          <span class="site-state-item-count">49</span>
           <span class="site-state-item-name">日志</span>
         </a>
       </div>
@@ -242,13 +242,13 @@ <h1 class="collection-header">kibana
     <span class="post-meta-item-icon">
       <i class="fa fa-chart-line"></i>
     </span>
-    <span title="站点总字数">125k</span>
+    <span title="站点总字数">129k</span>
   </span>
   <span class="post-meta-item">
     <span class="post-meta-item-icon">
       <i class="fa fa-coffee"></i>
     </span>
-    <span title="站点阅读时长">6:56</span>
+    <span title="站点阅读时长">7:09</span>
   </span>
 </div>
   <div class="powered-by">由 <a href="https://hexo.io/" rel="noopener" target="_blank">Hexo</a> & <a href="https://theme-next.js.org/" rel="noopener" target="_blank">NexT.Gemini</a> 强力驱动
diff --git a/tags/linux/index.html b/tags/linux/index.html
index 014f7dfd..47096989 100644
--- a/tags/linux/index.html
+++ b/tags/linux/index.html
@@ -151,7 +151,7 @@
   <nav class="site-state">
       <div class="site-state-item site-state-posts">
         <a href="/archives/">
-          <span class="site-state-item-count">48</span>
+          <span class="site-state-item-count">49</span>
           <span class="site-state-item-name">日志</span>
         </a>
       </div>
@@ -308,13 +308,13 @@ <h1 class="collection-header">linux
     <span class="post-meta-item-icon">
       <i class="fa fa-chart-line"></i>
     </span>
-    <span title="站点总字数">125k</span>
+    <span title="站点总字数">129k</span>
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   <span class="post-meta-item">
     <span class="post-meta-item-icon">
       <i class="fa fa-coffee"></i>
     </span>
-    <span title="站点阅读时长">6:56</span>
+    <span title="站点阅读时长">7:09</span>
   </span>
 </div>
   <div class="powered-by">由 <a href="https://hexo.io/" rel="noopener" target="_blank">Hexo</a> & <a href="https://theme-next.js.org/" rel="noopener" target="_blank">NexT.Gemini</a> 强力驱动
diff --git a/tags/lock/index.html b/tags/lock/index.html
index b2577019..145b044f 100644
--- a/tags/lock/index.html
+++ b/tags/lock/index.html
@@ -151,7 +151,7 @@
   <nav class="site-state">
       <div class="site-state-item site-state-posts">
         <a href="/archives/">
-          <span class="site-state-item-count">48</span>
+          <span class="site-state-item-count">49</span>
           <span class="site-state-item-name">日志</span>
         </a>
       </div>
@@ -262,13 +262,13 @@ <h1 class="collection-header">lock
     <span class="post-meta-item-icon">
       <i class="fa fa-chart-line"></i>
     </span>
-    <span title="站点总字数">125k</span>
+    <span title="站点总字数">129k</span>
   </span>
   <span class="post-meta-item">
     <span class="post-meta-item-icon">
       <i class="fa fa-coffee"></i>
     </span>
-    <span title="站点阅读时长">6:56</span>
+    <span title="站点阅读时长">7:09</span>
   </span>
 </div>
   <div class="powered-by">由 <a href="https://hexo.io/" rel="noopener" target="_blank">Hexo</a> & <a href="https://theme-next.js.org/" rel="noopener" target="_blank">NexT.Gemini</a> 强力驱动
diff --git a/tags/logrotate/index.html b/tags/logrotate/index.html
index 493abb54..d2def224 100644
--- a/tags/logrotate/index.html
+++ b/tags/logrotate/index.html
@@ -151,7 +151,7 @@
   <nav class="site-state">
       <div class="site-state-item site-state-posts">
         <a href="/archives/">
-          <span class="site-state-item-count">48</span>
+          <span class="site-state-item-count">49</span>
           <span class="site-state-item-name">日志</span>
         </a>
       </div>
@@ -242,13 +242,13 @@ <h1 class="collection-header">logrotate
     <span class="post-meta-item-icon">
       <i class="fa fa-chart-line"></i>
     </span>
-    <span title="站点总字数">125k</span>
+    <span title="站点总字数">129k</span>
   </span>
   <span class="post-meta-item">
     <span class="post-meta-item-icon">
       <i class="fa fa-coffee"></i>
     </span>
-    <span title="站点阅读时长">6:56</span>
+    <span title="站点阅读时长">7:09</span>
   </span>
 </div>
   <div class="powered-by">由 <a href="https://hexo.io/" rel="noopener" target="_blank">Hexo</a> & <a href="https://theme-next.js.org/" rel="noopener" target="_blank">NexT.Gemini</a> 强力驱动
diff --git a/tags/minikube/index.html b/tags/minikube/index.html
index 3da9453a..384f20a9 100644
--- a/tags/minikube/index.html
+++ b/tags/minikube/index.html
@@ -151,7 +151,7 @@
   <nav class="site-state">
       <div class="site-state-item site-state-posts">
         <a href="/archives/">
-          <span class="site-state-item-count">48</span>
+          <span class="site-state-item-count">49</span>
           <span class="site-state-item-name">日志</span>
         </a>
       </div>
@@ -242,13 +242,13 @@ <h1 class="collection-header">minikube
     <span class="post-meta-item-icon">
       <i class="fa fa-chart-line"></i>
     </span>
-    <span title="站点总字数">125k</span>
+    <span title="站点总字数">129k</span>
   </span>
   <span class="post-meta-item">
     <span class="post-meta-item-icon">
       <i class="fa fa-coffee"></i>
     </span>
-    <span title="站点阅读时长">6:56</span>
+    <span title="站点阅读时长">7:09</span>
   </span>
 </div>
   <div class="powered-by">由 <a href="https://hexo.io/" rel="noopener" target="_blank">Hexo</a> & <a href="https://theme-next.js.org/" rel="noopener" target="_blank">NexT.Gemini</a> 强力驱动
diff --git a/tags/mysql/index.html b/tags/mysql/index.html
index 2c742d2a..87c51c7d 100644
--- a/tags/mysql/index.html
+++ b/tags/mysql/index.html
@@ -151,7 +151,7 @@
   <nav class="site-state">
       <div class="site-state-item site-state-posts">
         <a href="/archives/">
-          <span class="site-state-item-count">48</span>
+          <span class="site-state-item-count">49</span>
           <span class="site-state-item-name">日志</span>
         </a>
       </div>
@@ -288,13 +288,13 @@ <h1 class="collection-header">mysql
     <span class="post-meta-item-icon">
       <i class="fa fa-chart-line"></i>
     </span>
-    <span title="站点总字数">125k</span>
+    <span title="站点总字数">129k</span>
   </span>
   <span class="post-meta-item">
     <span class="post-meta-item-icon">
       <i class="fa fa-coffee"></i>
     </span>
-    <span title="站点阅读时长">6:56</span>
+    <span title="站点阅读时长">7:09</span>
   </span>
 </div>
   <div class="powered-by">由 <a href="https://hexo.io/" rel="noopener" target="_blank">Hexo</a> & <a href="https://theme-next.js.org/" rel="noopener" target="_blank">NexT.Gemini</a> 强力驱动
diff --git a/tags/nginx/index.html b/tags/nginx/index.html
index e32a1e4e..74274d95 100644
--- a/tags/nginx/index.html
+++ b/tags/nginx/index.html
@@ -151,7 +151,7 @@
   <nav class="site-state">
       <div class="site-state-item site-state-posts">
         <a href="/archives/">
-          <span class="site-state-item-count">48</span>
+          <span class="site-state-item-count">49</span>
           <span class="site-state-item-name">日志</span>
         </a>
       </div>
@@ -262,13 +262,13 @@ <h1 class="collection-header">nginx
     <span class="post-meta-item-icon">
       <i class="fa fa-chart-line"></i>
     </span>
-    <span title="站点总字数">125k</span>
+    <span title="站点总字数">129k</span>
   </span>
   <span class="post-meta-item">
     <span class="post-meta-item-icon">
       <i class="fa fa-coffee"></i>
     </span>
-    <span title="站点阅读时长">6:56</span>
+    <span title="站点阅读时长">7:09</span>
   </span>
 </div>
   <div class="powered-by">由 <a href="https://hexo.io/" rel="noopener" target="_blank">Hexo</a> & <a href="https://theme-next.js.org/" rel="noopener" target="_blank">NexT.Gemini</a> 强力驱动
diff --git a/tags/openvpn/index.html b/tags/openvpn/index.html
index 4537f040..bfe59827 100644
--- a/tags/openvpn/index.html
+++ b/tags/openvpn/index.html
@@ -151,7 +151,7 @@
   <nav class="site-state">
       <div class="site-state-item site-state-posts">
         <a href="/archives/">
-          <span class="site-state-item-count">48</span>
+          <span class="site-state-item-count">49</span>
           <span class="site-state-item-name">日志</span>
         </a>
       </div>
@@ -282,13 +282,13 @@ <h1 class="collection-header">openvpn
     <span class="post-meta-item-icon">
       <i class="fa fa-chart-line"></i>
     </span>
-    <span title="站点总字数">125k</span>
+    <span title="站点总字数">129k</span>
   </span>
   <span class="post-meta-item">
     <span class="post-meta-item-icon">
       <i class="fa fa-coffee"></i>
     </span>
-    <span title="站点阅读时长">6:56</span>
+    <span title="站点阅读时长">7:09</span>
   </span>
 </div>
   <div class="powered-by">由 <a href="https://hexo.io/" rel="noopener" target="_blank">Hexo</a> & <a href="https://theme-next.js.org/" rel="noopener" target="_blank">NexT.Gemini</a> 强力驱动
diff --git a/tags/prometheus/index.html b/tags/prometheus/index.html
index 7db90fb0..3c3cc139 100644
--- a/tags/prometheus/index.html
+++ b/tags/prometheus/index.html
@@ -151,7 +151,7 @@
   <nav class="site-state">
       <div class="site-state-item site-state-posts">
         <a href="/archives/">
-          <span class="site-state-item-count">48</span>
+          <span class="site-state-item-count">49</span>
           <span class="site-state-item-name">日志</span>
         </a>
       </div>
@@ -242,13 +242,13 @@ <h1 class="collection-header">prometheus
     <span class="post-meta-item-icon">
       <i class="fa fa-chart-line"></i>
     </span>
-    <span title="站点总字数">125k</span>
+    <span title="站点总字数">129k</span>
   </span>
   <span class="post-meta-item">
     <span class="post-meta-item-icon">
       <i class="fa fa-coffee"></i>
     </span>
-    <span title="站点阅读时长">6:56</span>
+    <span title="站点阅读时长">7:09</span>
   </span>
 </div>
   <div class="powered-by">由 <a href="https://hexo.io/" rel="noopener" target="_blank">Hexo</a> & <a href="https://theme-next.js.org/" rel="noopener" target="_blank">NexT.Gemini</a> 强力驱动
diff --git a/tags/proxy/index.html b/tags/proxy/index.html
index 15dec47a..bc4a313a 100644
--- a/tags/proxy/index.html
+++ b/tags/proxy/index.html
@@ -151,7 +151,7 @@
   <nav class="site-state">
       <div class="site-state-item site-state-posts">
         <a href="/archives/">
-          <span class="site-state-item-count">48</span>
+          <span class="site-state-item-count">49</span>
           <span class="site-state-item-name">日志</span>
         </a>
       </div>
@@ -322,13 +322,13 @@ <h1 class="collection-header">proxy
     <span class="post-meta-item-icon">
       <i class="fa fa-chart-line"></i>
     </span>
-    <span title="站点总字数">125k</span>
+    <span title="站点总字数">129k</span>
   </span>
   <span class="post-meta-item">
     <span class="post-meta-item-icon">
       <i class="fa fa-coffee"></i>
     </span>
-    <span title="站点阅读时长">6:56</span>
+    <span title="站点阅读时长">7:09</span>
   </span>
 </div>
   <div class="powered-by">由 <a href="https://hexo.io/" rel="noopener" target="_blank">Hexo</a> & <a href="https://theme-next.js.org/" rel="noopener" target="_blank">NexT.Gemini</a> 强力驱动
diff --git a/tags/redis/index.html b/tags/redis/index.html
index 183c7bc3..759b6cdc 100644
--- a/tags/redis/index.html
+++ b/tags/redis/index.html
@@ -151,7 +151,7 @@
   <nav class="site-state">
       <div class="site-state-item site-state-posts">
         <a href="/archives/">
-          <span class="site-state-item-count">48</span>
+          <span class="site-state-item-count">49</span>
           <span class="site-state-item-name">日志</span>
         </a>
       </div>
@@ -242,13 +242,13 @@ <h1 class="collection-header">redis
     <span class="post-meta-item-icon">
       <i class="fa fa-chart-line"></i>
     </span>
-    <span title="站点总字数">125k</span>
+    <span title="站点总字数">129k</span>
   </span>
   <span class="post-meta-item">
     <span class="post-meta-item-icon">
       <i class="fa fa-coffee"></i>
     </span>
-    <span title="站点阅读时长">6:56</span>
+    <span title="站点阅读时长">7:09</span>
   </span>
 </div>
   <div class="powered-by">由 <a href="https://hexo.io/" rel="noopener" target="_blank">Hexo</a> & <a href="https://theme-next.js.org/" rel="noopener" target="_blank">NexT.Gemini</a> 强力驱动
diff --git a/tags/reverse-proxy/index.html b/tags/reverse-proxy/index.html
index 691f54b7..dff4a831 100644
--- a/tags/reverse-proxy/index.html
+++ b/tags/reverse-proxy/index.html
@@ -151,7 +151,7 @@
   <nav class="site-state">
       <div class="site-state-item site-state-posts">
         <a href="/archives/">
-          <span class="site-state-item-count">48</span>
+          <span class="site-state-item-count">49</span>
           <span class="site-state-item-name">日志</span>
         </a>
       </div>
@@ -242,13 +242,13 @@ <h1 class="collection-header">reverse proxy
     <span class="post-meta-item-icon">
       <i class="fa fa-chart-line"></i>
     </span>
-    <span title="站点总字数">125k</span>
+    <span title="站点总字数">129k</span>
   </span>
   <span class="post-meta-item">
     <span class="post-meta-item-icon">
       <i class="fa fa-coffee"></i>
     </span>
-    <span title="站点阅读时长">6:56</span>
+    <span title="站点阅读时长">7:09</span>
   </span>
 </div>
   <div class="powered-by">由 <a href="https://hexo.io/" rel="noopener" target="_blank">Hexo</a> & <a href="https://theme-next.js.org/" rel="noopener" target="_blank">NexT.Gemini</a> 强力驱动
diff --git a/tags/spi/index.html b/tags/spi/index.html
index 00dc1acc..ca4dce7b 100644
--- a/tags/spi/index.html
+++ b/tags/spi/index.html
@@ -151,7 +151,7 @@
   <nav class="site-state">
       <div class="site-state-item site-state-posts">
         <a href="/archives/">
-          <span class="site-state-item-count">48</span>
+          <span class="site-state-item-count">49</span>
           <span class="site-state-item-name">日志</span>
         </a>
       </div>
@@ -282,13 +282,13 @@ <h1 class="collection-header">spi
     <span class="post-meta-item-icon">
       <i class="fa fa-chart-line"></i>
     </span>
-    <span title="站点总字数">125k</span>
+    <span title="站点总字数">129k</span>
   </span>
   <span class="post-meta-item">
     <span class="post-meta-item-icon">
       <i class="fa fa-coffee"></i>
     </span>
-    <span title="站点阅读时长">6:56</span>
+    <span title="站点阅读时长">7:09</span>
   </span>
 </div>
   <div class="powered-by">由 <a href="https://hexo.io/" rel="noopener" target="_blank">Hexo</a> & <a href="https://theme-next.js.org/" rel="noopener" target="_blank">NexT.Gemini</a> 强力驱动
diff --git a/tags/spring-boot/index.html b/tags/spring-boot/index.html
index 7b77c54c..03b1a708 100644
--- a/tags/spring-boot/index.html
+++ b/tags/spring-boot/index.html
@@ -151,7 +151,7 @@
   <nav class="site-state">
       <div class="site-state-item site-state-posts">
         <a href="/archives/">
-          <span class="site-state-item-count">48</span>
+          <span class="site-state-item-count">49</span>
           <span class="site-state-item-name">日志</span>
         </a>
       </div>
@@ -302,13 +302,13 @@ <h1 class="collection-header">spring boot
     <span class="post-meta-item-icon">
       <i class="fa fa-chart-line"></i>
     </span>
-    <span title="站点总字数">125k</span>
+    <span title="站点总字数">129k</span>
   </span>
   <span class="post-meta-item">
     <span class="post-meta-item-icon">
       <i class="fa fa-coffee"></i>
     </span>
-    <span title="站点阅读时长">6:56</span>
+    <span title="站点阅读时长">7:09</span>
   </span>
 </div>
   <div class="powered-by">由 <a href="https://hexo.io/" rel="noopener" target="_blank">Hexo</a> & <a href="https://theme-next.js.org/" rel="noopener" target="_blank">NexT.Gemini</a> 强力驱动
diff --git a/tags/spring/index.html b/tags/spring/index.html
index 85f76e1d..c224cfc5 100644
--- a/tags/spring/index.html
+++ b/tags/spring/index.html
@@ -151,7 +151,7 @@
   <nav class="site-state">
       <div class="site-state-item site-state-posts">
         <a href="/archives/">
-          <span class="site-state-item-count">48</span>
+          <span class="site-state-item-count">49</span>
           <span class="site-state-item-name">日志</span>
         </a>
       </div>
@@ -425,13 +425,13 @@ <h1 class="collection-header">spring
     <span class="post-meta-item-icon">
       <i class="fa fa-chart-line"></i>
     </span>
-    <span title="站点总字数">125k</span>
+    <span title="站点总字数">129k</span>
   </span>
   <span class="post-meta-item">
     <span class="post-meta-item-icon">
       <i class="fa fa-coffee"></i>
     </span>
-    <span title="站点阅读时长">6:56</span>
+    <span title="站点阅读时长">7:09</span>
   </span>
 </div>
   <div class="powered-by">由 <a href="https://hexo.io/" rel="noopener" target="_blank">Hexo</a> & <a href="https://theme-next.js.org/" rel="noopener" target="_blank">NexT.Gemini</a> 强力驱动
diff --git a/tags/spring/page/2/index.html b/tags/spring/page/2/index.html
index d0aac089..753019bc 100644
--- a/tags/spring/page/2/index.html
+++ b/tags/spring/page/2/index.html
@@ -151,7 +151,7 @@
   <nav class="site-state">
       <div class="site-state-item site-state-posts">
         <a href="/archives/">
-          <span class="site-state-item-count">48</span>
+          <span class="site-state-item-count">49</span>
           <span class="site-state-item-name">日志</span>
         </a>
       </div>
@@ -265,13 +265,13 @@ <h1 class="collection-header">spring
     <span class="post-meta-item-icon">
       <i class="fa fa-chart-line"></i>
     </span>
-    <span title="站点总字数">125k</span>
+    <span title="站点总字数">129k</span>
   </span>
   <span class="post-meta-item">
     <span class="post-meta-item-icon">
       <i class="fa fa-coffee"></i>
     </span>
-    <span title="站点阅读时长">6:56</span>
+    <span title="站点阅读时长">7:09</span>
   </span>
 </div>
   <div class="powered-by">由 <a href="https://hexo.io/" rel="noopener" target="_blank">Hexo</a> & <a href="https://theme-next.js.org/" rel="noopener" target="_blank">NexT.Gemini</a> 强力驱动
diff --git a/tags/ssh/index.html b/tags/ssh/index.html
index 677015dc..dce9521b 100644
--- a/tags/ssh/index.html
+++ b/tags/ssh/index.html
@@ -151,7 +151,7 @@
   <nav class="site-state">
       <div class="site-state-item site-state-posts">
         <a href="/archives/">
-          <span class="site-state-item-count">48</span>
+          <span class="site-state-item-count">49</span>
           <span class="site-state-item-name">日志</span>
         </a>
       </div>
@@ -242,13 +242,13 @@ <h1 class="collection-header">ssh
     <span class="post-meta-item-icon">
       <i class="fa fa-chart-line"></i>
     </span>
-    <span title="站点总字数">125k</span>
+    <span title="站点总字数">129k</span>
   </span>
   <span class="post-meta-item">
     <span class="post-meta-item-icon">
       <i class="fa fa-coffee"></i>
     </span>
-    <span title="站点阅读时长">6:56</span>
+    <span title="站点阅读时长">7:09</span>
   </span>
 </div>
   <div class="powered-by">由 <a href="https://hexo.io/" rel="noopener" target="_blank">Hexo</a> & <a href="https://theme-next.js.org/" rel="noopener" target="_blank">NexT.Gemini</a> 强力驱动
diff --git a/tags/synchronized/index.html b/tags/synchronized/index.html
index 94963dfa..858fe390 100644
--- a/tags/synchronized/index.html
+++ b/tags/synchronized/index.html
@@ -151,7 +151,7 @@
   <nav class="site-state">
       <div class="site-state-item site-state-posts">
         <a href="/archives/">
-          <span class="site-state-item-count">48</span>
+          <span class="site-state-item-count">49</span>
           <span class="site-state-item-name">日志</span>
         </a>
       </div>
@@ -242,13 +242,13 @@ <h1 class="collection-header">synchronized
     <span class="post-meta-item-icon">
       <i class="fa fa-chart-line"></i>
     </span>
-    <span title="站点总字数">125k</span>
+    <span title="站点总字数">129k</span>
   </span>
   <span class="post-meta-item">
     <span class="post-meta-item-icon">
       <i class="fa fa-coffee"></i>
     </span>
-    <span title="站点阅读时长">6:56</span>
+    <span title="站点阅读时长">7:09</span>
   </span>
 </div>
   <div class="powered-by">由 <a href="https://hexo.io/" rel="noopener" target="_blank">Hexo</a> & <a href="https://theme-next.js.org/" rel="noopener" target="_blank">NexT.Gemini</a> 强力驱动
diff --git a/tags/tmux/index.html b/tags/tmux/index.html
index ec47fdee..6d6d7e09 100644
--- a/tags/tmux/index.html
+++ b/tags/tmux/index.html
@@ -151,7 +151,7 @@
   <nav class="site-state">
       <div class="site-state-item site-state-posts">
         <a href="/archives/">
-          <span class="site-state-item-count">48</span>
+          <span class="site-state-item-count">49</span>
           <span class="site-state-item-name">日志</span>
         </a>
       </div>
@@ -242,13 +242,13 @@ <h1 class="collection-header">tmux
     <span class="post-meta-item-icon">
       <i class="fa fa-chart-line"></i>
     </span>
-    <span title="站点总字数">125k</span>
+    <span title="站点总字数">129k</span>
   </span>
   <span class="post-meta-item">
     <span class="post-meta-item-icon">
       <i class="fa fa-coffee"></i>
     </span>
-    <span title="站点阅读时长">6:56</span>
+    <span title="站点阅读时长">7:09</span>
   </span>
 </div>
   <div class="powered-by">由 <a href="https://hexo.io/" rel="noopener" target="_blank">Hexo</a> & <a href="https://theme-next.js.org/" rel="noopener" target="_blank">NexT.Gemini</a> 强力驱动
diff --git a/tags/ubuntu/index.html b/tags/ubuntu/index.html
index 51ea171e..cd6ddccb 100644
--- a/tags/ubuntu/index.html
+++ b/tags/ubuntu/index.html
@@ -151,7 +151,7 @@
   <nav class="site-state">
       <div class="site-state-item site-state-posts">
         <a href="/archives/">
-          <span class="site-state-item-count">48</span>
+          <span class="site-state-item-count">49</span>
           <span class="site-state-item-name">日志</span>
         </a>
       </div>
@@ -265,13 +265,13 @@ <h1 class="collection-header">ubuntu
     <span class="post-meta-item-icon">
       <i class="fa fa-chart-line"></i>
     </span>
-    <span title="站点总字数">125k</span>
+    <span title="站点总字数">129k</span>
   </span>
   <span class="post-meta-item">
     <span class="post-meta-item-icon">
       <i class="fa fa-coffee"></i>
     </span>
-    <span title="站点阅读时长">6:56</span>
+    <span title="站点阅读时长">7:09</span>
   </span>
 </div>
   <div class="powered-by">由 <a href="https://hexo.io/" rel="noopener" target="_blank">Hexo</a> & <a href="https://theme-next.js.org/" rel="noopener" target="_blank">NexT.Gemini</a> 强力驱动
diff --git a/tags/vim/index.html b/tags/vim/index.html
index e7973974..52639137 100644
--- a/tags/vim/index.html
+++ b/tags/vim/index.html
@@ -151,7 +151,7 @@
   <nav class="site-state">
       <div class="site-state-item site-state-posts">
         <a href="/archives/">
-          <span class="site-state-item-count">48</span>
+          <span class="site-state-item-count">49</span>
           <span class="site-state-item-name">日志</span>
         </a>
       </div>
@@ -242,13 +242,13 @@ <h1 class="collection-header">vim
     <span class="post-meta-item-icon">
       <i class="fa fa-chart-line"></i>
     </span>
-    <span title="站点总字数">125k</span>
+    <span title="站点总字数">129k</span>
   </span>
   <span class="post-meta-item">
     <span class="post-meta-item-icon">
       <i class="fa fa-coffee"></i>
     </span>
-    <span title="站点阅读时长">6:56</span>
+    <span title="站点阅读时长">7:09</span>
   </span>
 </div>
   <div class="powered-by">由 <a href="https://hexo.io/" rel="noopener" target="_blank">Hexo</a> & <a href="https://theme-next.js.org/" rel="noopener" target="_blank">NexT.Gemini</a> 强力驱动