diff --git a/2020/08/19/docker-frequently-used-commands/index.html b/2020/08/19/docker-frequently-used-commands/index.html
index 26a9cd0e..37f0fd1a 100644
--- a/2020/08/19/docker-frequently-used-commands/index.html
+++ b/2020/08/19/docker-frequently-used-commands/index.html
@@ -27,7 +27,7 @@
 <meta property="og:description" content="常用命令从 Docker 官方命令行参考中按顺序选取常用的命令和用法。 docker attach将本地标准输入、输出和错误流附加到一个正在运行的容器。 用法1docker attach [OPTIONS] CONTAINER  描述使用 docker attach 通过容器 ID 或名称将终端的标准输入、输出和错误附加到正在运行的容器。这允许你查看其正在进行的输出或以交互方式控制它，就好像命令直">
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-<meta property="article:modified_time" content="2023-12-04T08:27:13.932Z">
+<meta property="article:modified_time" content="2023-12-05T08:44:37.391Z">
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+      <time title="修改时间：2023-12-05 16:44:37" itemprop="dateModified" datetime="2023-12-05T16:44:37+08:00">2023-12-05</time>
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+    <span title="站点阅读时长">4:18</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/2023/05/27/how-to-install-clash-on-ubuntu/index.html b/2023/05/27/how-to-install-clash-on-ubuntu/index.html
index 221b6545..6eec7d1b 100644
--- a/2023/05/27/how-to-install-clash-on-ubuntu/index.html
+++ b/2023/05/27/how-to-install-clash-on-ubuntu/index.html
@@ -27,7 +27,7 @@
 <meta property="og:description" content="安装 Clash从 GitHub 下载预构建的二进制文件。 1:&#x2F;mnt&#x2F;hgfs&#x2F;share$ wget https:&#x2F;&#x2F;github.com&#x2F;Dreamacro&#x2F;clash&#x2F;releases&#x2F;download&#x2F;v1.16.0&#x2F;clash-linux-amd64-v1.16.0.gz  使用 gzip 解压压缩包 clash-linux-amd64-v1.16.0.gz 得到 clash-lin">
 <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="2023-12-05T08:44:37.391Z">
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+      <time title="修改时间：2023-12-05 16:44:37" itemprop="dateModified" datetime="2023-12-05T16:44:37+08:00">2023-12-05</time>
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@@ -365,13 +365,13 @@ <h2 id="设置-Clash-为后台服务"><a href="#设置-Clash-为后台服务" cl
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+    <span title="站点阅读时长">4:18</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 32f13e6d..abd58fdc 100644
--- 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
@@ -27,7 +27,7 @@
 <meta property="og:description" content="安装 OpenVPN ConnectmacOS 访问官网下载。iOS 访问 AppStore，需要登录外区 Apple ID。 配置 OpenVPN Connect客户端提供了两种方式导入配置文件，一是通过 URL，建议 URL 仅限在私有网络内访问，二是通过其他方式例如邮件，下载为本地文件再导入。 配置文件的组织方式又分为两种形式，一种是将 CA 根证书 ca.crt，客户端证书 client.">
 <meta property="og:locale" content="zh_CN">
 <meta property="article:published_time" content="2023-06-07T09:04:23.000Z">
-<meta property="article:modified_time" content="2023-12-04T08:27:13.932Z">
+<meta property="article:modified_time" content="2023-12-05T08:44:37.391Z">
 <meta property="article:author" content="Moralok">
 <meta property="article:tag" content="openvpn">
 <meta name="twitter:card" content="summary">
@@ -156,7 +156,7 @@
   <nav class="site-state">
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         <a href="/archives/">
-          <span class="site-state-item-count">28</span>
+          <span class="site-state-item-count">29</span>
           <span class="site-state-item-name">日志</span>
         </a>
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@@ -237,7 +237,7 @@ <h1 class="post-title" itemprop="name headline">
         <i class="far fa-calendar-check"></i>
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@@ -346,13 +346,13 @@ <h2 id="参考链接"><a href="#参考链接" class="headerlink" title="参考
     <span class="post-meta-item-icon">
       <i class="fa fa-chart-line"></i>
     </span>
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-    <span title="站点阅读时长">4:06</span>
+    <span title="站点阅读时长">4:18</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-server-on-windows-10/index.html b/2023/06/07/how-to-setup-OpenVPN-server-on-windows-10/index.html
index 12989d2a..8facffea 100644
--- 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
@@ -27,7 +27,7 @@
 <meta property="og:description" content="安装 OpenVPN server从 OpenVPN 社区 下载 Windows 64-bit MSI installer。本次安装的版本为 OpenVPN 2.6.4。  注意事项：在选择安装类型时选择 Customize 而不要选择 Install Now。额外勾选 OpenVPN -&gt; OpenVPN Service -&gt; Entire feature will be insta">
 <meta property="og:locale" content="zh_CN">
 <meta property="article:published_time" content="2023-06-07T07:18:02.000Z">
-<meta property="article:modified_time" content="2023-12-04T08:27:13.932Z">
+<meta property="article:modified_time" content="2023-12-05T08:44:37.391Z">
 <meta property="article:author" content="Moralok">
 <meta property="article:tag" content="openvpn">
 <meta name="twitter:card" content="summary">
@@ -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">28</span>
+          <span class="site-state-item-count">29</span>
           <span class="site-state-item-name">日志</span>
         </a>
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@@ -237,7 +237,7 @@ <h1 class="post-title" itemprop="name headline">
         <i class="far fa-calendar-check"></i>
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-      <time title="修改时间：2023-12-04 16:27:13" itemprop="dateModified" datetime="2023-12-04T16:27:13+08:00">2023-12-04</time>
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@@ -351,13 +351,13 @@ <h2 id="参考链接"><a href="#参考链接" class="headerlink" title="参考
     <span class="post-meta-item-icon">
       <i class="fa fa-chart-line"></i>
     </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">4:06</span>
+    <span title="站点阅读时长">4:18</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/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 230de814..ab361335 100644
--- 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
@@ -27,7 +27,7 @@
 <meta property="og:description" content="网络概况宽带是电信宽带，分配了动态的公网 IP。光猫使用桥接模式，通过路由器拨号上网（PPPoE），路由器局域网为 192.168.3.0&#x2F;24。一台 Windows 10 主机，在路由器局域网上的 IP 192.168.3.120。。Windows 10 主机上运行 Vmware 虚拟机，网络采用 NAT 模式。子网为 192.168.46.0&#x2F;24。运行了 Linux 主机">
 <meta property="og:locale" content="zh_CN">
 <meta property="article:published_time" content="2023-06-07T14:19:17.000Z">
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+<meta property="article:modified_time" content="2023-12-05T08:44:37.391Z">
 <meta property="article:author" content="Moralok">
 <meta property="article:tag" content="openvpn">
 <meta name="twitter:card" content="summary">
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       <div class="site-state-item site-state-posts">
         <a href="/archives/">
-          <span class="site-state-item-count">28</span>
+          <span class="site-state-item-count">29</span>
           <span class="site-state-item-name">日志</span>
         </a>
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@@ -378,13 +378,13 @@ <h2 id="参考链接"><a href="#参考链接" class="headerlink" title="参考
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       <i class="fa fa-chart-line"></i>
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-    <span title="站点阅读时长">4:06</span>
+    <span title="站点阅读时长">4:18</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/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 658caf54..310cd9ee 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="2023-12-04T08:27:13.932Z">
+<meta property="article:modified_time" content="2023-12-05T08:44:37.391Z">
 <meta property="article:author" content="Moralok">
 <meta property="article:tag" content="proxy">
 <meta property="article:tag" content="docker">
@@ -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">28</span>
+          <span class="site-state-item-count">29</span>
           <span class="site-state-item-name">日志</span>
         </a>
       </div>
@@ -238,7 +238,7 @@ <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：2023-12-04 16:27:13" itemprop="dateModified" datetime="2023-12-04T16:27:13+08:00">2023-12-04</time>
+      <time title="修改时间：2023-12-05 16:44:37" itemprop="dateModified" datetime="2023-12-05T16:44:37+08:00">2023-12-05</time>
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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
     <span class="post-meta-item-icon">
       <i class="fa fa-chart-line"></i>
     </span>
-    <span title="站点总字数">74k</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">4:06</span>
+    <span title="站点阅读时长">4:18</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/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
index 3ef8355c..36f79a7f 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="2023-12-04T08:27:13.932Z">
+<meta property="article:modified_time" content="2023-12-05T08:44:37.391Z">
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 <meta property="article:tag" content="minikube">
 <meta name="twitter:card" content="summary">
@@ -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">28</span>
+          <span class="site-state-item-count">29</span>
           <span class="site-state-item-name">日志</span>
         </a>
       </div>
@@ -237,7 +237,7 @@ <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：2023-12-04 16:27:13" itemprop="dateModified" datetime="2023-12-04T16:27:13+08:00">2023-12-04</time>
+      <time title="修改时间：2023-12-05 16:44:37" itemprop="dateModified" datetime="2023-12-05T16:44:37+08:00">2023-12-05</time>
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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
     <span class="post-meta-item-icon">
       <i class="fa fa-chart-line"></i>
     </span>
-    <span title="站点总字数">74k</span>
+    <span title="站点总字数">77k</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">4:06</span>
+    <span title="站点阅读时长">4:18</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/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 a0c5d65f..74d30d7b 100644
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@@ -27,7 +27,7 @@
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 <meta property="article:published_time" content="2023-06-24T16:04:43.000Z">
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@@ -341,13 +341,13 @@ <h2 id="参考链接"><a href="#参考链接" class="headerlink" title="参考
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index f8d98c48..277aa708 100644
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 <meta property="article:published_time" content="2023-06-28T20:36:35.000Z">
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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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diff --git a/2023/06/29/tmux-frequently-used-commands/index.html b/2023/06/29/tmux-frequently-used-commands/index.html
index 454178e7..605f3f37 100644
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 <meta property="article:published_time" content="2023-06-29T10:44:44.000Z">
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 <meta property="article:published_time" content="2023-07-13T20:08:11.000Z">
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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 9e35bedb..db940b67 100644
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 <meta property="article:tag" content="spring">
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-          <span class="site-state-item-count">28</span>
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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 45874671..c7717f47 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 609f4c9d..11597c2f 100644
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index 822068d2..d3ebc88d 100644
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diff --git a/2023/12/02/rotating-nginx-logs-in-docker-container-with-logrotate/index.html b/2023/12/02/rotating-nginx-logs-in-docker-container-with-logrotate/index.html
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+        <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="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></pre></td><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="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">......</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>
+<li><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></li>
+</ul>
+<h3 id="获取要导入的目标"><a href="#获取要导入的目标" class="headerlink" title="获取要导入的目标"></a>获取要导入的目标</h3><p>在 <code>doProcessConfigurationClass</code> 方法中处理配置类构建配置模型时，会调用 <code>processImports</code> 方法处理 <code>Import</code> 注解。在进入方法前，会调用 <code>getImports</code> 方法从 <code>sourceClass</code> 获取要导入的目标。</p>
+<blockquote>
+<p>注意：目标不仅仅来自直接标注在 <code>sourceClass</code> 上的 <code>Import</code> 注解，因为 <code>sourceClass</code> 上可能还有其他的注解，这些注解自身可能标注了 <code>Import</code> 注解，因此需要递归地遍历所有注解，找到所有的 <code>Import</code> 注解。</p>
+</blockquote>
+<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">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">// 前后省略 @PropertySource、@ComponentScan、@ImportSource、@Bean 等注解的处理</span></span><br><span class="line">    <span class="comment">// 处理 Import 注解</span></span><br><span class="line">    processImports(configClass, sourceClass, getImports(sourceClass), <span class="literal">true</span>);</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<p><code>collectImports</code> 方法是一种常见的递归写法（深度优先遍历）。<code>imports</code> 存放要导入的目标，<code>visited</code> 存放已经访问过的 <code>sourceClass</code>。<code>sourceClass</code> 在入口处包装了一个普通的 <code>Class</code>，在递归的过程中包装的都是一个注解 <code>Class</code>。</p>
+<blockquote>
+<p>注意：这里还没有检测循环导入的情况并抛出异常，但 <code>visited</code> 保证了只会遍历一次。</p>
+</blockquote>
+<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></pre></td><td class="code"><pre><span class="line"><span class="comment">// 获取 Import 注解 value 中的 Class 对象，并包装为 SourceClass 返回</span></span><br><span class="line"><span class="keyword">private</span> Set&lt;SourceClass&gt; <span class="title function_">getImports</span><span class="params">(SourceClass sourceClass)</span> <span class="keyword">throws</span> IOException &#123;</span><br><span class="line">    Set&lt;SourceClass&gt; imports = <span class="keyword">new</span> <span class="title class_">LinkedHashSet</span>&lt;SourceClass&gt;();</span><br><span class="line">    Set&lt;SourceClass&gt; visited = <span class="keyword">new</span> <span class="title class_">LinkedHashSet</span>&lt;SourceClass&gt;();</span><br><span class="line">    collectImports(sourceClass, imports, visited);</span><br><span class="line">    <span class="keyword">return</span> imports;</span><br><span class="line">&#125;</span><br><span class="line"></span><br><span class="line"><span class="comment">// 递归地收集要导入的目标（包装为 SourceClass）</span></span><br><span class="line"><span class="keyword">private</span> <span class="keyword">void</span> <span class="title function_">collectImports</span><span class="params">(SourceClass sourceClass, Set&lt;SourceClass&gt; imports, Set&lt;SourceClass&gt; visited)</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">// 如果 sourceClass 尚未访问过</span></span><br><span class="line">    <span class="keyword">if</span> (visited.add(sourceClass)) &#123;</span><br><span class="line">        <span class="comment">// 遍历 sourceClass 上的注解</span></span><br><span class="line">        <span class="keyword">for</span> (SourceClass annotation : sourceClass.getAnnotations()) &#123;</span><br><span class="line">            <span class="type">String</span> <span class="variable">annName</span> <span class="operator">=</span> annotation.getMetadata().getClassName();</span><br><span class="line">            <span class="comment">// 只要注解的名称不是 java 开头或者不是 Import 注解</span></span><br><span class="line">            <span class="keyword">if</span> (!annName.startsWith(<span class="string">&quot;java&quot;</span>) &amp;&amp; !annName.equals(Import.class.getName())) &#123;</span><br><span class="line">                <span class="comment">// 将该注解作为 sourceClass 递归地调用</span></span><br><span class="line">                collectImports(annotation, imports, visited);</span><br><span class="line">            &#125;</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="comment">// 将 Import 注解的 value 的值转换为 sourceClass 加入 imports</span></span><br><span class="line">        imports.addAll(sourceClass.getAnnotationAttributes(Import.class.getName(), <span class="string">&quot;value&quot;</span>));</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<p>这时候，并不区分要导入的目标的 <code>Class</code> 有什么特别之处，<code>Import</code> 注解的语义，此时宽泛地说就是：“将 <code>value</code> 中的类导入”。但是显而易见，这样的方式不够灵活，因此才有了另外两种更有灵活性的导入方式：<code>ImportSelector</code> 和 <code>ImportBeanDefinitionRegistrar</code>，<code>Spring</code> 最终不会真的注册这两种类，而是注册它们“介绍”的类，相当于把确定导入什么类的工作委托给它们。</p>
+<h3 id="处理要导入的目标"><a href="#处理要导入的目标" class="headerlink" title="处理要导入的目标"></a>处理要导入的目标</h3><p><code>processImports</code> 方法是处理 <code>Import</code> 注解的核心方法，这里的处理逻辑就对应着 <code>Import</code> 注解的三种使用方式。主要步骤如下：</p>
+<ul>
+<li>检测要导入的候选者不为空</li>
+<li>判断是否要检测循环导入以及是否存在循环导入</li>
+<li>处理要导入的候选者<ul>
+<li>如果是 <code>ImportSelector</code> 类型，调用 <code>selectImports</code> 方法获取新的要导入的目标，递归调用 <code>processImports</code> 处理</li>
+<li>如果是 <code>ImportBeanDefinitionRegistrar</code> 类型，添加到配置模型 <code>configClass</code>（出口 <code>1</code>）</li>
+<li>如果是其他剩余情况，作为配置类处理（出口 <code>2</code>）</li>
+</ul>
+</li>
+</ul>
+<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><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><span class="line">75</span><br><span class="line">76</span><br><span class="line">77</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">private</span> <span class="keyword">void</span> <span class="title function_">processImports</span><span class="params">(ConfigurationClass configClass, SourceClass currentSourceClass,</span></span><br><span class="line"><span class="params">			Collection&lt;SourceClass&gt; importCandidates, <span class="type">boolean</span> checkForCircularImports)</span> <span class="keyword">throws</span> IOException &#123;</span><br><span class="line">    <span class="comment">// 如果要导入的目标为空，直接返回</span></span><br><span class="line">    <span class="keyword">if</span> (importCandidates.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="keyword">if</span> (checkForCircularImports &amp;&amp; isChainedImportOnStack(configClass)) &#123;</span><br><span class="line">        <span class="comment">// 如果要检查循环导入，且确实存在循环导入，则抛出异常</span></span><br><span class="line">        <span class="built_in">this</span>.problemReporter.error(<span class="keyword">new</span> <span class="title class_">CircularImportProblem</span>(configClass, <span class="built_in">this</span>.importStack));</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">// 将配置模型放入 importStack，用于检查循环导入</span></span><br><span class="line">        <span class="built_in">this</span>.importStack.push(configClass);</span><br><span class="line">        <span class="keyword">try</span> &#123;</span><br><span class="line">            <span class="comment">// 遍历每一个准备导入的目标</span></span><br><span class="line">            <span class="keyword">for</span> (SourceClass candidate : importCandidates) &#123;</span><br><span class="line">                <span class="comment">// 如果是 ImportSelector 类型，委托给它确定导入目标</span></span><br><span class="line">                <span class="keyword">if</span> (candidate.isAssignable(ImportSelector.class)) &#123;</span><br><span class="line">                    <span class="comment">// 加载类</span></span><br><span class="line">                    Class&lt;?&gt; candidateClass = candidate.loadClass();</span><br><span class="line">                    <span class="comment">// 实例化得到 ImportSelector 实例</span></span><br><span class="line">                    <span class="type">ImportSelector</span> <span class="variable">selector</span> <span class="operator">=</span> BeanUtils.instantiateClass(candidateClass, ImportSelector.class);</span><br><span class="line">                    <span class="comment">// 调用其 Aware 接口</span></span><br><span class="line">                    ParserStrategyUtils.invokeAwareMethods(</span><br><span class="line">                            selector, <span class="built_in">this</span>.environment, <span class="built_in">this</span>.resourceLoader, <span class="built_in">this</span>.registry);</span><br><span class="line">                    <span class="keyword">if</span> (<span class="built_in">this</span>.deferredImportSelectors != <span class="literal">null</span> &amp;&amp; selector <span class="keyword">instanceof</span> DeferredImportSelector) &#123;</span><br><span class="line">                        <span class="comment">// 如果是 DeferredImportSelector 类型，存入 deferredImportSelectors 推迟调用</span></span><br><span class="line">                        <span class="built_in">this</span>.deferredImportSelectors.add(</span><br><span class="line">                                <span class="keyword">new</span> <span class="title class_">DeferredImportSelectorHolder</span>(configClass, (DeferredImportSelector) selector));</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">// 调用 selectImports 方法，返回要导入的目标的全限定类名</span></span><br><span class="line">                        String[] importClassNames = selector.selectImports(currentSourceClass.getMetadata());</span><br><span class="line">                        <span class="comment">// 包装为 SourceClass</span></span><br><span class="line">                        Collection&lt;SourceClass&gt; importSourceClasses = asSourceClasses(importClassNames);</span><br><span class="line">                        <span class="comment">// 递归调用 processImports</span></span><br><span class="line">                        <span class="comment">// 从这里看，ImportSelector 本质上是更加灵活的 Import</span></span><br><span class="line">                        processImports(configClass, currentSourceClass, importSourceClasses, <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">// 如果是 ImportBeanDefinitionRegistrar 类型，委托给它注册额外的 BeanDefinitions</span></span><br><span class="line">                <span class="keyword">else</span> <span class="keyword">if</span> (candidate.isAssignable(ImportBeanDefinitionRegistrar.class)) &#123;</span><br><span class="line">                    <span class="comment">// 加载类</span></span><br><span class="line">                    Class&lt;?&gt; candidateClass = candidate.loadClass();</span><br><span class="line">                    <span class="comment">// 实例化得到 ImportBeanDefinitionRegistrar 实例</span></span><br><span class="line">                    <span class="type">ImportBeanDefinitionRegistrar</span> <span class="variable">registrar</span> <span class="operator">=</span></span><br><span class="line">                            BeanUtils.instantiateClass(candidateClass, ImportBeanDefinitionRegistrar.class);</span><br><span class="line">                    <span class="comment">// 调用其 Aware 接口</span></span><br><span class="line">                    ParserStrategyUtils.invokeAwareMethods(</span><br><span class="line">                            registrar, <span class="built_in">this</span>.environment, <span class="built_in">this</span>.resourceLoader, <span class="built_in">this</span>.registry);</span><br><span class="line">                    <span class="comment">// 添加到配置模型</span></span><br><span class="line">                    configClass.addImportBeanDefinitionRegistrar(registrar, currentSourceClass.getMetadata());</span><br><span class="line">                &#125;</span><br><span class="line">                <span class="comment">// 既不是 ImportSelector，也不是 ImportBeanDefinitionRegistrar 的其他剩余情况，将其视为被 Configuration 注解标注的配置类进行处理</span></span><br><span class="line">                <span class="keyword">else</span> &#123;</span><br><span class="line">                    <span class="built_in">this</span>.importStack.registerImport(</span><br><span class="line">                            currentSourceClass.getMetadata(), candidate.getMetadata().getClassName());</span><br><span class="line">                    <span class="comment">// asConfigClass 方法建立了 candidate importBy configClass 的关系</span></span><br><span class="line">                    processConfigurationClass(candidate.asConfigClass(configClass));</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> (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 process import candidates for configuration class [&quot;</span> +</span><br><span class="line">                    configClass.getMetadata().getClassName() + <span class="string">&quot;]&quot;</span>, ex);</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="keyword">finally</span> &#123;</span><br><span class="line">            <span class="comment">// pop 配置模型</span></span><br><span class="line">            <span class="built_in">this</span>.importStack.pop();</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="类型一：ImportSelector"><a href="#类型一：ImportSelector" class="headerlink" title="类型一：ImportSelector"></a>类型一：ImportSelector</h4><p>如果要导入的目标是 <code>ImportSelector</code> 类型，那么 <code>Spring</code> 将确定真正导入什么目标的工作委托给它，不导入目标本身，实际上只导入目标“介绍”的类。具体步骤是：</p>
+<ol>
+<li>先获取 <code>Class</code> 对象</li>
+<li>再实例化得到一个 <code>ImportSelector</code> 实例</li>
+<li>调用 <code>selectImports</code> 方法，该方法返回的是类的全限定名，这样就得到了真正要导入的目标</li>
+<li>再次递归调用 <code>processImports</code></li>
+</ol>
+<p><code>ImportSelector</code> 就像它名字的含义一样，本质上是一种导入选择器，是一种更加灵活的 <code>getImports</code> 方法。由于返回的目标可能属于三种情形中的任意一种，所以对这些目标的处理还是要回到 <code>processImports</code> 方法。可以说 <code>ImportSelector</code> 类型本身不是 <code>processImports</code> 方法的出口，它最终会转换为 <code>ImportBeanDefinitionRegistrar</code> 或其他剩余情况。</p>
+<p><code>ImportSelector</code> 灵活性的来源：</p>
+<ul>
+<li><code>selectImports</code> 的 <code>AnnotationMetadata</code> 参数，为它提供了根据注解信息返回要导入的目标的能力</li>
+<li><code>ImportSelector</code> 可以实现 <code>Aware</code> 接口，用以感知到一些容器级别的资源，如 <code>BeanFactory</code>，这为它提供了根据这些资源中的信息返回要导入的目标的能力</li>
+</ul>
+<h4 id="类型二：ImportBeanDefinitionRegistrar"><a href="#类型二：ImportBeanDefinitionRegistrar" class="headerlink" title="类型二：ImportBeanDefinitionRegistrar"></a>类型二：ImportBeanDefinitionRegistrar</h4><p>如果要导入的目标是 <code>ImportBeanDefinitionRegistrar</code>，它会和 <code>ImportSelector</code> 有些相似却又有所不同。<code>Spring</code> 同样将确定真正导入什么目标的工作委托给它，不导入目标本身，实际上只导入目标“介绍”的类。</p>
+<ol>
+<li>先获取 <code>Class</code> 对象</li>
+<li>再实例化得到一个 <code>ImportBeanDefinitionRegistrar</code> 实例</li>
+<li>添加到配置模型 <code>configClass</code> 的 <code>importBeanDefinitionRegistrars</code> 属性</li>
+</ol>
+<p><code>ImportBeanDefinitionRegistrar</code> 不像 <code>ImportSelector</code> 需要进一步处理，它本身就代表着一个返回出口，成为了配置模型的一部分。但是请注意，<code>registerBeanDefinitions</code> 方法此时并没有被调用。</p>
+<p><code>ImportBeanDefinitionRegistrar</code> 灵活性的来源：</p>
+<ul>
+<li><code>registerBeanDefinitions</code> 的 <code>AnnotationMetadata</code> 参数，为它提供了根据注解信息决定注册 <code>BeanDefinition</code> 的能力</li>
+<li><code>registerBeanDefinitions</code> 的 <code>BeanDefinitionRegistry</code> 参数，为它提供了根据 <code>BeanDefinitionRegistry</code> 中的信息决定注册 <code>BeanDefinition</code> 的能力</li>
+<li><code>ImportBeanDefinitionRegistrar</code> 可以实现 <code>Aware</code> 接口，用以感知到一些容器级别的资源，如 <code>BeanFactory</code>，这为它提供了根据这些资源中的信息返回要导入的目标的能力</li>
+</ul>
+<h4 id="类型三：其他剩余情况"><a href="#类型三：其他剩余情况" class="headerlink" title="类型三：其他剩余情况"></a>类型三：其他剩余情况</h4><p>如果要导入的目标属于既不是 <code>ImportSelector</code> 也不是 <code>ImportBeanDefinitionRegistrar</code> 的其他剩余情况，那么 <code>Spring</code> 将其视为被 <code>Configuration</code> 注解标注的配置类进行处理。这里的处理逻辑是，<code>Import</code> 注解导入的类可能不是一个普通的类，而是一个配置类，因此需要回到 <code>processConfigurationClass</code> 进行处理。<code>processConfigurationClass</code> 方法正是本文开头的 <code>doProcessConfigurationClass</code> 方法的调用方，这里有两个地方值得注意：</p>
+<ul>
+<li><code>Import</code> 注解产生的 <code>ConfigurationClass</code> 根据不同的情况需要合并或者被抛弃，显式声明比 Import 导入的优先级更高。</li>
+<li>其他剩余情况下，目标最终会转换为一个配置模型，添加到 <code>parser</code> 的 <code>configurationClasses</code> 属性。</li>
+</ul>
+<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></pre></td><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">// 判断是否跳过处理</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">// 如果配置模型已经存在</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="keyword">if</span> (existingClass != <span class="literal">null</span>) &#123;</span><br><span class="line">        <span class="comment">// 如果新的配置模型代表的类，是 Import 导入的</span></span><br><span class="line">        <span class="keyword">if</span> (configClass.isImported()) &#123;</span><br><span class="line">            <span class="comment">// 如果已存在的配置模型也是 Import 导入的</span></span><br><span class="line">            <span class="keyword">if</span> (existingClass.isImported()) &#123;</span><br><span class="line">                <span class="comment">// 合并它们的来源</span></span><br><span class="line">                <span class="comment">// 比如一个类 A 既被 Config1 上的 Import 注解导入，也被 Config2 上的 Import 导入</span></span><br><span class="line">                existingClass.mergeImportedBy(configClass);</span><br><span class="line">            &#125;</span><br><span class="line">            <span class="comment">// 否则忽略新的因为 Import 导入而产生的配置模型</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">// 使用显式定义的代替 Import 导入的（显式定义的和 Import 导入的有什么不同吗）</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">// 先递归地处理配置类和它的父类，因为配合各种注解，可能引入更多的类</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">// 一个配置类，本身最终被解析成配置模型（配置模型在后续将会解析出 BeanDefinition）</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>
+
+<h3 id="DeferredImportSelector-的调用时机"><a href="#DeferredImportSelector-的调用时机" class="headerlink" title="DeferredImportSelector 的调用时机"></a>DeferredImportSelector 的调用时机</h3><p>在解析完每一批（注释中说“全部”）的配置类后，会统一调用 <code>DeferredImportSelector</code>。它作为一个标记接口推迟了 <code>selectImports</code> 的时机，打破了处理顺序的限制，在方法被调用时，可以得到更加完整的信息。注释中说“在选择导入的目标是 <code>@Conditional</code> 时，这个类型的选择器会很有用”，但是我不太理解，因为这个时候，处理配置类得到的信息尚未转换为 <code>ImportSelector</code> 可以感知到的信息，不像 <code>ImportBeanDefinitionRegistrar</code>，它被调用的时机在最后，也因此可以感知到更多的信息。</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></pre></td><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="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">                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 class="comment">// 调用 DeferredImportSelectors</span></span><br><span class="line">    processDeferredImportSelectors();</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_">processDeferredImportSelectors</span><span class="params">()</span> &#123;</span><br><span class="line">    <span class="comment">// 获取处理这一批配置类获得的 DeferredImportSelectors</span></span><br><span class="line">    List&lt;DeferredImportSelectorHolder&gt; deferredImports = <span class="built_in">this</span>.deferredImportSelectors;</span><br><span class="line">    <span class="comment">// 清空</span></span><br><span class="line">    <span class="built_in">this</span>.deferredImportSelectors = <span class="literal">null</span>;</span><br><span class="line">    <span class="comment">// 排序</span></span><br><span class="line">    Collections.sort(deferredImports, DEFERRED_IMPORT_COMPARATOR);</span><br><span class="line">    <span class="comment">// 遍历</span></span><br><span class="line">    <span class="keyword">for</span> (DeferredImportSelectorHolder deferredImport : deferredImports) &#123;</span><br><span class="line">        <span class="type">ConfigurationClass</span> <span class="variable">configClass</span> <span class="operator">=</span> deferredImport.getConfigurationClass();</span><br><span class="line">        <span class="keyword">try</span> &#123;</span><br><span class="line">            <span class="comment">// 调用 selectImports 获取要导入的目标</span></span><br><span class="line">            String[] imports = deferredImport.getImportSelector().selectImports(configClass.getMetadata());</span><br><span class="line">            <span class="comment">// 调用 processImports 处理要导入的目标，这里不管循环导入？竟然是任由 StackOverFlow</span></span><br><span class="line">            processImports(configClass, asSourceClass(configClass), asSourceClasses(imports), <span class="literal">false</span>);</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 process import candidates for configuration class [&quot;</span> +</span><br><span class="line">                    configClass.getMetadata().getClassName() + <span class="string">&quot;]&quot;</span>, 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>
+
+<h3 id="ImportBeanDefinitionRegistrar-的调用时机"><a href="#ImportBeanDefinitionRegistrar-的调用时机" class="headerlink" title="ImportBeanDefinitionRegistrar 的调用时机"></a>ImportBeanDefinitionRegistrar 的调用时机</h3><p><code>ConfigurationClassPostProcessor</code> 在每次解析得到新的一批配置模型后，都会调用 <code>ConfigurationClassBeanDefinitionReader</code> 的 <code>loadBeanDefinitions</code> 方法加载 <code>BeanDefinition</code>，在这过程的最后会从 <code>ImportBeanDefinitionRegistrar</code> 加载 <code>BeanDefinition</code>。这代表在处理同一批配置类时，在 <code>registerBeanDefinitions</code> 方法中总是能感知到以其他方式注册到 <code>BeanDefinitionRegistry</code> 中的 <code>BeanDefinition</code>，不论书面定义的顺序如何。</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></pre></td><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">// 遍历每一个配置模型</span></span><br><span class="line">    <span class="keyword">for</span> (ConfigurationClass configClass : configurationModel) &#123;</span><br><span class="line">        <span class="comment">// 从配置模型中加载 BeanDefinistion</span></span><br><span class="line">        loadBeanDefinitionsForConfigurationClass(configClass, trackedConditionEvaluator);</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_">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="comment">// 如果配置模型本身是导入的，为自身注册 BeanDefinition</span></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="comment">// 为 BeanMethod 加载 BeanDefinition（Bean 注解）</span></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">    <span class="comment">// 为 ImportResources 加载 BeanDefinition（ImportResource 注解）</span></span><br><span class="line">    loadBeanDefinitionsFromImportedResources(configClass.getImportedResources());</span><br><span class="line">    <span class="comment">// 从 ImportBeanDefinitionRegistrar 加载 BeanDefinition</span></span><br><span class="line">    loadBeanDefinitionsFromRegistrars(configClass.getImportBeanDefinitionRegistrars());</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_">loadBeanDefinitionsFromRegistrars</span><span class="params">(Map&lt;ImportBeanDefinitionRegistrar, AnnotationMetadata&gt; registrars)</span> &#123;</span><br><span class="line">    <span class="comment">// 遍历 ImportBeanDefinitionRegistrar 调用 registerBeanDefinitions 方法注册 BeanDefinition</span></span><br><span class="line">    <span class="keyword">for</span> (Map.Entry&lt;ImportBeanDefinitionRegistrar, AnnotationMetadata&gt; entry : registrars.entrySet()) &#123;</span><br><span class="line">        entry.getKey().registerBeanDefinitions(entry.getValue(), <span class="built_in">this</span>.registry);</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<h3 id="循环导入的检测"><a href="#循环导入的检测" class="headerlink" title="循环导入的检测"></a>循环导入的检测</h3><p>在处理导入的目标前将配置类放入 <code>importStack</code>，处理完毕移除。如果要导入的目标属于其他剩余情况时，注册被导入类-&gt;所有导入类集合的映射关系。</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></pre></td><td class="code"><pre><span class="line"><span class="keyword">private</span> <span class="keyword">void</span> <span class="title function_">processImports</span><span class="params">(ConfigurationClass configClass, SourceClass currentSourceClass,</span></span><br><span class="line"><span class="params">			Collection&lt;SourceClass&gt; importCandidates, <span class="type">boolean</span> checkForCircularImports)</span> <span class="keyword">throws</span> IOException &#123;</span><br><span class="line">    <span class="comment">// ...</span></span><br><span class="line">    <span class="keyword">if</span> (checkForCircularImports &amp;&amp; isChainedImportOnStack(configClass)) &#123;</span><br><span class="line">        <span class="comment">// 如果要检查循环导入，且确实存在循环导入，则抛出异常</span></span><br><span class="line">        <span class="built_in">this</span>.problemReporter.error(<span class="keyword">new</span> <span class="title class_">CircularImportProblem</span>(configClass, <span class="built_in">this</span>.importStack));</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">// 将配置模型放入 importStack，用于检查循环导入</span></span><br><span class="line">        <span class="built_in">this</span>.importStack.push(configClass);</span><br><span class="line">        <span class="keyword">try</span> &#123;</span><br><span class="line">            <span class="comment">// 遍历每一个准备导入的目标</span></span><br><span class="line">            <span class="keyword">for</span> (SourceClass candidate : importCandidates) &#123;</span><br><span class="line">                <span class="comment">// ...</span></span><br><span class="line">                <span class="keyword">else</span> &#123;</span><br><span class="line">                    <span class="comment">// 记录了被导入类-&gt;所有导入类集合的映射关系</span></span><br><span class="line">                    <span class="built_in">this</span>.importStack.registerImport(</span><br><span class="line">                            currentSourceClass.getMetadata(), candidate.getMetadata().getClassName());</span><br><span class="line">                    <span class="comment">// asConfigClass 方法建立了 candidate importBy configClass 的关系</span></span><br><span class="line">                    processConfigurationClass(candidate.asConfigClass(configClass));</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">        <span class="keyword">finally</span> &#123;</span><br><span class="line">            <span class="comment">// pop 配置模型</span></span><br><span class="line">            <span class="built_in">this</span>.importStack.pop();</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>检测是否发生循环导入。以当前类开始，循环向上查找最近一个导入自身的类，如果找到自身，说明发生循环导入。</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">private</span> <span class="type">boolean</span> <span class="title function_">isChainedImportOnStack</span><span class="params">(ConfigurationClass configClass)</span> &#123;</span><br><span class="line">    <span class="comment">// 如果 importStack 已存在该配置模型</span></span><br><span class="line">    <span class="keyword">if</span> (<span class="built_in">this</span>.importStack.contains(configClass)) &#123;</span><br><span class="line">        <span class="type">String</span> <span class="variable">configClassName</span> <span class="operator">=</span> configClass.getMetadata().getClassName();</span><br><span class="line">        <span class="comment">// 获取最新一个导入 configClass 的类</span></span><br><span class="line">        <span class="type">AnnotationMetadata</span> <span class="variable">importingClass</span> <span class="operator">=</span> <span class="built_in">this</span>.importStack.getImportingClassFor(configClassName);</span><br><span class="line">        <span class="comment">// 循环查找导入类的最近一个导入类，如果找到了自身，表示发生循环导入</span></span><br><span class="line">        <span class="keyword">while</span> (importingClass != <span class="literal">null</span>) &#123;</span><br><span class="line">            <span class="keyword">if</span> (configClassName.equals(importingClass.getClassName())) &#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">            importingClass = <span class="built_in">this</span>.importStack.getImportingClassFor(importingClass.getClassName());</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">false</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><table>
+<thead>
+<tr>
+<th></th>
+<th><code>ImportSelector</code></th>
+<th><code>ImportBeanDefinitionRegistrar</code></th>
+<th>其他剩余情况</th>
+</tr>
+</thead>
+<tbody><tr>
+<td>灵活性</td>
+<td>中</td>
+<td>高</td>
+<td>低</td>
+</tr>
+<tr>
+<td>处理结果</td>
+<td></td>
+<td>转换为配置模型的一部分</td>
+<td>转换为一个配置模型</td>
+</tr>
+<tr>
+<td>方法调用时机</td>
+<td>立即（或解析配置类的最后）</td>
+<td>加载 <code>BeanDefinition</code> 的最后</td>
+<td></td>
+</tr>
+<tr>
+<td>方法的结果</td>
+<td>获取 Import 目标</td>
+<td>直接注册 <code>BeanDefinition</code></td>
+<td></td>
+</tr>
+</tbody></table>
+
+    </div>
+
+    
+    
+    
+
+    <footer class="post-footer">
+          <div class="post-tags">
+              <a href="/tags/java/" rel="tag"># java</a>
+              <a href="/tags/spring/" rel="tag"># spring</a>
+          </div>
+
+        
+
+          <div class="post-nav">
+            <div class="post-nav-item">
+                <a href="/2023/12/02/rotating-nginx-logs-in-docker-container-with-logrotate/" rel="prev" title="使用 logrotate 滚动 Docker 容器内的 Nginx 的日志">
+                  <i class="fa fa-chevron-left"></i> 使用 logrotate 滚动 Docker 容器内的 Nginx 的日志
+                </a>
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+            <div class="post-nav-item">
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+    </footer>
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+</div>
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+  </main>
+
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+    <div class="footer-inner">
+
+
+<div class="copyright">
+  &copy; 
+  <span itemprop="copyrightYear">2023</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">77k</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">4:18</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>
+
+  
+  <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>
+
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+  
+
+
+  <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>
+
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+</body>
+</html>
diff --git a/archives/2020/08/index.html b/archives/2020/08/index.html
index 78a65b33..b892a4d1 100644
--- a/archives/2020/08/index.html
+++ b/archives/2020/08/index.html
@@ -152,7 +152,7 @@ <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">28</span>
+          <span class="site-state-item-count">29</span>
           <span class="site-state-item-name">日志</span>
         </a>
       </div>
@@ -195,7 +195,7 @@ <h1 class="site-title">Moralok</h1>
   <div class="post-block">
     <div class="post-content">
       <div class="collection-title">
-        <span class="collection-header">嗯..! 目前共计 28 篇日志。 继续努力。</span>
+        <span class="collection-header">嗯..! 目前共计 29 篇日志。 继续努力。</span>
       </div>
 
       
@@ -250,13 +250,13 @@ <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">74k</span>
+    <span title="站点总字数">77k</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">4:06</span>
+    <span title="站点阅读时长">4:18</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 8ab4ff48..ab804ed4 100644
--- a/archives/2020/index.html
+++ b/archives/2020/index.html
@@ -152,7 +152,7 @@ <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">28</span>
+          <span class="site-state-item-count">29</span>
           <span class="site-state-item-name">日志</span>
         </a>
       </div>
@@ -195,7 +195,7 @@ <h1 class="site-title">Moralok</h1>
   <div class="post-block">
     <div class="post-content">
       <div class="collection-title">
-        <span class="collection-header">嗯..! 目前共计 28 篇日志。 继续努力。</span>
+        <span class="collection-header">嗯..! 目前共计 29 篇日志。 继续努力。</span>
       </div>
 
       
@@ -250,13 +250,13 @@ <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">74k</span>
+    <span title="站点总字数">77k</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">4:06</span>
+    <span title="站点阅读时长">4:18</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 b6313192..4e6b9102 100644
--- a/archives/2023/05/index.html
+++ b/archives/2023/05/index.html
@@ -152,7 +152,7 @@ <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">28</span>
+          <span class="site-state-item-count">29</span>
           <span class="site-state-item-name">日志</span>
         </a>
       </div>
@@ -195,7 +195,7 @@ <h1 class="site-title">Moralok</h1>
   <div class="post-block">
     <div class="post-content">
       <div class="collection-title">
-        <span class="collection-header">嗯..! 目前共计 28 篇日志。 继续努力。</span>
+        <span class="collection-header">嗯..! 目前共计 29 篇日志。 继续努力。</span>
       </div>
 
       
@@ -250,13 +250,13 @@ <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">74k</span>
+    <span title="站点总字数">77k</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">4:06</span>
+    <span title="站点阅读时长">4:18</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 932783fe..98ddbe0c 100644
--- a/archives/2023/06/index.html
+++ b/archives/2023/06/index.html
@@ -152,7 +152,7 @@ <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">28</span>
+          <span class="site-state-item-count">29</span>
           <span class="site-state-item-name">日志</span>
         </a>
       </div>
@@ -195,7 +195,7 @@ <h1 class="site-title">Moralok</h1>
   <div class="post-block">
     <div class="post-content">
       <div class="collection-title">
-        <span class="collection-header">嗯..! 目前共计 28 篇日志。 继续努力。</span>
+        <span class="collection-header">嗯..! 目前共计 29 篇日志。 继续努力。</span>
       </div>
 
       
@@ -390,13 +390,13 @@ <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">74k</span>
+    <span title="站点总字数">77k</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">4:06</span>
+    <span title="站点阅读时长">4:18</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 33bdc81f..53a5da58 100644
--- a/archives/2023/07/index.html
+++ b/archives/2023/07/index.html
@@ -152,7 +152,7 @@ <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">28</span>
+          <span class="site-state-item-count">29</span>
           <span class="site-state-item-name">日志</span>
         </a>
       </div>
@@ -195,7 +195,7 @@ <h1 class="site-title">Moralok</h1>
   <div class="post-block">
     <div class="post-content">
       <div class="collection-title">
-        <span class="collection-header">嗯..! 目前共计 28 篇日志。 继续努力。</span>
+        <span class="collection-header">嗯..! 目前共计 29 篇日志。 继续努力。</span>
       </div>
 
       
@@ -250,13 +250,13 @@ <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">74k</span>
+    <span title="站点总字数">77k</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">4:06</span>
+    <span title="站点阅读时长">4:18</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 d530c770..1fadab66 100644
--- a/archives/2023/08/index.html
+++ b/archives/2023/08/index.html
@@ -152,7 +152,7 @@ <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">28</span>
+          <span class="site-state-item-count">29</span>
           <span class="site-state-item-name">日志</span>
         </a>
       </div>
@@ -195,7 +195,7 @@ <h1 class="site-title">Moralok</h1>
   <div class="post-block">
     <div class="post-content">
       <div class="collection-title">
-        <span class="collection-header">嗯..! 目前共计 28 篇日志。 继续努力。</span>
+        <span class="collection-header">嗯..! 目前共计 29 篇日志。 继续努力。</span>
       </div>
 
       
@@ -270,13 +270,13 @@ <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">74k</span>
+    <span title="站点总字数">77k</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">4:06</span>
+    <span title="站点阅读时长">4:18</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 b105ba98..aad65a28 100644
--- a/archives/2023/11/index.html
+++ b/archives/2023/11/index.html
@@ -152,7 +152,7 @@ <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">28</span>
+          <span class="site-state-item-count">29</span>
           <span class="site-state-item-name">日志</span>
         </a>
       </div>
@@ -195,7 +195,7 @@ <h1 class="site-title">Moralok</h1>
   <div class="post-block">
     <div class="post-content">
       <div class="collection-title">
-        <span class="collection-header">嗯..! 目前共计 28 篇日志。 继续努力。</span>
+        <span class="collection-header">嗯..! 目前共计 29 篇日志。 继续努力。</span>
       </div>
 
       
@@ -433,13 +433,13 @@ <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">74k</span>
+    <span title="站点总字数">77k</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">4:06</span>
+    <span title="站点阅读时长">4:18</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 c2b4b88b..65f2a1e6 100644
--- a/archives/2023/11/page/2/index.html
+++ b/archives/2023/11/page/2/index.html
@@ -152,7 +152,7 @@ <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">28</span>
+          <span class="site-state-item-count">29</span>
           <span class="site-state-item-name">日志</span>
         </a>
       </div>
@@ -195,7 +195,7 @@ <h1 class="site-title">Moralok</h1>
   <div class="post-block">
     <div class="post-content">
       <div class="collection-title">
-        <span class="collection-header">嗯..! 目前共计 28 篇日志。 继续努力。</span>
+        <span class="collection-header">嗯..! 目前共计 29 篇日志。 继续努力。</span>
       </div>
 
       
@@ -293,13 +293,13 @@ <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">74k</span>
+    <span title="站点总字数">77k</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">4:06</span>
+    <span title="站点阅读时长">4:18</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 1fcf6b2c..426b1c1d 100644
--- a/archives/2023/12/index.html
+++ b/archives/2023/12/index.html
@@ -152,7 +152,7 @@ <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">28</span>
+          <span class="site-state-item-count">29</span>
           <span class="site-state-item-name">日志</span>
         </a>
       </div>
@@ -195,7 +195,7 @@ <h1 class="site-title">Moralok</h1>
   <div class="post-block">
     <div class="post-content">
       <div class="collection-title">
-        <span class="collection-header">嗯..! 目前共计 28 篇日志。 继续努力。</span>
+        <span class="collection-header">嗯..! 目前共计 29 篇日志。 继续努力。</span>
       </div>
 
       
@@ -203,6 +203,26 @@ <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="2023-12-04T08:36:21+08:00"
+              content="2023-12-04">
+          12-04
+        </time>
+      </div>
+
+      <div class="post-title">
+          <a class="post-title-link" href="/2023/12/04/use-and-analysis-of-Import-annotation-in-Spring/" itemprop="url">
+            <span itemprop="name">Spring 中 @Import 注解的使用和源码分析</span>
+          </a>
+      </div>
+
+      
+    </header>
+  </article>
+
   <article itemscope itemtype="http://schema.org/Article">
     <header class="post-header">
       <div class="post-meta-container">
@@ -270,13 +290,13 @@ <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">74k</span>
+    <span title="站点总字数">77k</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">4:06</span>
+    <span title="站点阅读时长">4:18</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 70be2330..279ff6e7 100644
--- a/archives/2023/index.html
+++ b/archives/2023/index.html
@@ -152,7 +152,7 @@ <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">28</span>
+          <span class="site-state-item-count">29</span>
           <span class="site-state-item-name">日志</span>
         </a>
       </div>
@@ -195,7 +195,7 @@ <h1 class="site-title">Moralok</h1>
   <div class="post-block">
     <div class="post-content">
       <div class="collection-title">
-        <span class="collection-header">嗯..! 目前共计 28 篇日志。 继续努力。</span>
+        <span class="collection-header">嗯..! 目前共计 29 篇日志。 继续努力。</span>
       </div>
 
       
@@ -203,6 +203,26 @@ <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="2023-12-04T08:36:21+08:00"
+              content="2023-12-04">
+          12-04
+        </time>
+      </div>
+
+      <div class="post-title">
+          <a class="post-title-link" href="/2023/12/04/use-and-analysis-of-Import-annotation-in-Spring/" itemprop="url">
+            <span itemprop="name">Spring 中 @Import 注解的使用和源码分析</span>
+          </a>
+      </div>
+
+      
+    </header>
+  </article>
+
   <article itemscope itemtype="http://schema.org/Article">
     <header class="post-header">
       <div class="post-meta-container">
@@ -383,26 +403,6 @@ <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="2023-11-13T14:02:49+08:00"
-              content="2023-11-13">
-          11-13
-        </time>
-      </div>
-
-      <div class="post-title">
-          <a class="post-title-link" href="/2023/11/13/simple-implementation-of-distributed-lock-based-on-Redis/" itemprop="url">
-            <span itemprop="name">基于 Redis 的分布式锁的简单实现</span>
-          </a>
-      </div>
-
-      
-    </header>
-  </article>
-
 
     </div>
   </div>
@@ -433,13 +433,13 @@ <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">74k</span>
+    <span title="站点总字数">77k</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">4:06</span>
+    <span title="站点阅读时长">4:18</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 a58bb4b0..10c83e44 100644
--- a/archives/2023/page/2/index.html
+++ b/archives/2023/page/2/index.html
@@ -152,7 +152,7 @@ <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">28</span>
+          <span class="site-state-item-count">29</span>
           <span class="site-state-item-name">日志</span>
         </a>
       </div>
@@ -195,7 +195,7 @@ <h1 class="site-title">Moralok</h1>
   <div class="post-block">
     <div class="post-content">
       <div class="collection-title">
-        <span class="collection-header">嗯..! 目前共计 28 篇日志。 继续努力。</span>
+        <span class="collection-header">嗯..! 目前共计 29 篇日志。 继续努力。</span>
       </div>
 
       
@@ -203,6 +203,26 @@ <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="2023-11-13T14:02:49+08:00"
+              content="2023-11-13">
+          11-13
+        </time>
+      </div>
+
+      <div class="post-title">
+          <a class="post-title-link" href="/2023/11/13/simple-implementation-of-distributed-lock-based-on-Redis/" itemprop="url">
+            <span itemprop="name">基于 Redis 的分布式锁的简单实现</span>
+          </a>
+      </div>
+
+      
+    </header>
+  </article>
+
   <article itemscope itemtype="http://schema.org/Article">
     <header class="post-header">
       <div class="post-meta-container">
@@ -383,26 +403,6 @@ <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="2023-06-29T04:36:35+08:00"
-              content="2023-06-29">
-          06-29
-        </time>
-      </div>
-
-      <div class="post-title">
-          <a class="post-title-link" href="/2023/06/28/how-to-use-ssh-to-connect-github-and-server/" itemprop="url">
-            <span itemprop="name">如何使用 SSH 连接 Github 和服务器</span>
-          </a>
-      </div>
-
-      
-    </header>
-  </article>
-
 
     </div>
   </div>
@@ -433,13 +433,13 @@ <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">74k</span>
+    <span title="站点总字数">77k</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">4:06</span>
+    <span title="站点阅读时长">4:18</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 1ba22f6c..7bc3926a 100644
--- a/archives/2023/page/3/index.html
+++ b/archives/2023/page/3/index.html
@@ -152,7 +152,7 @@ <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">28</span>
+          <span class="site-state-item-count">29</span>
           <span class="site-state-item-name">日志</span>
         </a>
       </div>
@@ -195,7 +195,7 @@ <h1 class="site-title">Moralok</h1>
   <div class="post-block">
     <div class="post-content">
       <div class="collection-title">
-        <span class="collection-header">嗯..! 目前共计 28 篇日志。 继续努力。</span>
+        <span class="collection-header">嗯..! 目前共计 29 篇日志。 继续努力。</span>
       </div>
 
       
@@ -203,6 +203,26 @@ <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="2023-06-29T04:36:35+08:00"
+              content="2023-06-29">
+          06-29
+        </time>
+      </div>
+
+      <div class="post-title">
+          <a class="post-title-link" href="/2023/06/28/how-to-use-ssh-to-connect-github-and-server/" itemprop="url">
+            <span itemprop="name">如何使用 SSH 连接 Github 和服务器</span>
+          </a>
+      </div>
+
+      
+    </header>
+  </article>
+
   <article itemscope itemtype="http://schema.org/Article">
     <header class="post-header">
       <div class="post-meta-container">
@@ -373,13 +393,13 @@ <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">74k</span>
+    <span title="站点总字数">77k</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">4:06</span>
+    <span title="站点阅读时长">4:18</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 43f001f3..87d82edc 100644
--- a/archives/index.html
+++ b/archives/index.html
@@ -152,7 +152,7 @@ <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">28</span>
+          <span class="site-state-item-count">29</span>
           <span class="site-state-item-name">日志</span>
         </a>
       </div>
@@ -195,7 +195,7 @@ <h1 class="site-title">Moralok</h1>
   <div class="post-block">
     <div class="post-content">
       <div class="collection-title">
-        <span class="collection-header">嗯..! 目前共计 28 篇日志。 继续努力。</span>
+        <span class="collection-header">嗯..! 目前共计 29 篇日志。 继续努力。</span>
       </div>
 
       
@@ -203,6 +203,26 @@ <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="2023-12-04T08:36:21+08:00"
+              content="2023-12-04">
+          12-04
+        </time>
+      </div>
+
+      <div class="post-title">
+          <a class="post-title-link" href="/2023/12/04/use-and-analysis-of-Import-annotation-in-Spring/" itemprop="url">
+            <span itemprop="name">Spring 中 @Import 注解的使用和源码分析</span>
+          </a>
+      </div>
+
+      
+    </header>
+  </article>
+
   <article itemscope itemtype="http://schema.org/Article">
     <header class="post-header">
       <div class="post-meta-container">
@@ -383,26 +403,6 @@ <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="2023-11-13T14:02:49+08:00"
-              content="2023-11-13">
-          11-13
-        </time>
-      </div>
-
-      <div class="post-title">
-          <a class="post-title-link" href="/2023/11/13/simple-implementation-of-distributed-lock-based-on-Redis/" itemprop="url">
-            <span itemprop="name">基于 Redis 的分布式锁的简单实现</span>
-          </a>
-      </div>
-
-      
-    </header>
-  </article>
-
 
     </div>
   </div>
@@ -433,13 +433,13 @@ <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">74k</span>
+    <span title="站点总字数">77k</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">4:06</span>
+    <span title="站点阅读时长">4:18</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 4c7de36e..69fa5149 100644
--- a/archives/page/2/index.html
+++ b/archives/page/2/index.html
@@ -152,7 +152,7 @@ <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">28</span>
+          <span class="site-state-item-count">29</span>
           <span class="site-state-item-name">日志</span>
         </a>
       </div>
@@ -195,7 +195,7 @@ <h1 class="site-title">Moralok</h1>
   <div class="post-block">
     <div class="post-content">
       <div class="collection-title">
-        <span class="collection-header">嗯..! 目前共计 28 篇日志。 继续努力。</span>
+        <span class="collection-header">嗯..! 目前共计 29 篇日志。 继续努力。</span>
       </div>
 
       
@@ -203,6 +203,26 @@ <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="2023-11-13T14:02:49+08:00"
+              content="2023-11-13">
+          11-13
+        </time>
+      </div>
+
+      <div class="post-title">
+          <a class="post-title-link" href="/2023/11/13/simple-implementation-of-distributed-lock-based-on-Redis/" itemprop="url">
+            <span itemprop="name">基于 Redis 的分布式锁的简单实现</span>
+          </a>
+      </div>
+
+      
+    </header>
+  </article>
+
   <article itemscope itemtype="http://schema.org/Article">
     <header class="post-header">
       <div class="post-meta-container">
@@ -383,26 +403,6 @@ <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="2023-06-29T04:36:35+08:00"
-              content="2023-06-29">
-          06-29
-        </time>
-      </div>
-
-      <div class="post-title">
-          <a class="post-title-link" href="/2023/06/28/how-to-use-ssh-to-connect-github-and-server/" itemprop="url">
-            <span itemprop="name">如何使用 SSH 连接 Github 和服务器</span>
-          </a>
-      </div>
-
-      
-    </header>
-  </article>
-
 
     </div>
   </div>
@@ -433,13 +433,13 @@ <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">74k</span>
+    <span title="站点总字数">77k</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">4:06</span>
+    <span title="站点阅读时长">4:18</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 9254a4a4..d4c5021f 100644
--- a/archives/page/3/index.html
+++ b/archives/page/3/index.html
@@ -152,7 +152,7 @@ <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">28</span>
+          <span class="site-state-item-count">29</span>
           <span class="site-state-item-name">日志</span>
         </a>
       </div>
@@ -195,7 +195,7 @@ <h1 class="site-title">Moralok</h1>
   <div class="post-block">
     <div class="post-content">
       <div class="collection-title">
-        <span class="collection-header">嗯..! 目前共计 28 篇日志。 继续努力。</span>
+        <span class="collection-header">嗯..! 目前共计 29 篇日志。 继续努力。</span>
       </div>
 
       
@@ -203,6 +203,26 @@ <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="2023-06-29T04:36:35+08:00"
+              content="2023-06-29">
+          06-29
+        </time>
+      </div>
+
+      <div class="post-title">
+          <a class="post-title-link" href="/2023/06/28/how-to-use-ssh-to-connect-github-and-server/" itemprop="url">
+            <span itemprop="name">如何使用 SSH 连接 Github 和服务器</span>
+          </a>
+      </div>
+
+      
+    </header>
+  </article>
+
   <article itemscope itemtype="http://schema.org/Article">
     <header class="post-header">
       <div class="post-meta-container">
@@ -396,13 +416,13 @@ <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">74k</span>
+    <span title="站点总字数">77k</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">4:06</span>
+    <span title="站点阅读时长">4:18</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 50d3036c..cb901c88 100644
--- a/index.html
+++ b/index.html
@@ -152,7 +152,7 @@ <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">28</span>
+          <span class="site-state-item-count">29</span>
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@@ -191,6 +191,234 @@ <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="/2023/12/04/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>
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+          <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="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></pre></td><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="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">......</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>
+<li><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></li>
+</ul>
+<h3 id="获取要导入的目标"><a href="#获取要导入的目标" class="headerlink" title="获取要导入的目标"></a>获取要导入的目标</h3><p>在 <code>doProcessConfigurationClass</code> 方法中处理配置类构建配置模型时，会调用 <code>processImports</code> 方法处理 <code>Import</code> 注解。在进入方法前，会调用 <code>getImports</code> 方法从 <code>sourceClass</code> 获取要导入的目标。</p>
+<blockquote>
+<p>注意：目标不仅仅来自直接标注在 <code>sourceClass</code> 上的 <code>Import</code> 注解，因为 <code>sourceClass</code> 上可能还有其他的注解，这些注解自身可能标注了 <code>Import</code> 注解，因此需要递归地遍历所有注解，找到所有的 <code>Import</code> 注解。</p>
+</blockquote>
+<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">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">// 前后省略 @PropertySource、@ComponentScan、@ImportSource、@Bean 等注解的处理</span></span><br><span class="line">    <span class="comment">// 处理 Import 注解</span></span><br><span class="line">    processImports(configClass, sourceClass, getImports(sourceClass), <span class="literal">true</span>);</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<p><code>collectImports</code> 方法是一种常见的递归写法（深度优先遍历）。<code>imports</code> 存放要导入的目标，<code>visited</code> 存放已经访问过的 <code>sourceClass</code>。<code>sourceClass</code> 在入口处包装了一个普通的 <code>Class</code>，在递归的过程中包装的都是一个注解 <code>Class</code>。</p>
+<blockquote>
+<p>注意：这里还没有检测循环导入的情况并抛出异常，但 <code>visited</code> 保证了只会遍历一次。</p>
+</blockquote>
+<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></pre></td><td class="code"><pre><span class="line"><span class="comment">// 获取 Import 注解 value 中的 Class 对象，并包装为 SourceClass 返回</span></span><br><span class="line"><span class="keyword">private</span> Set&lt;SourceClass&gt; <span class="title function_">getImports</span><span class="params">(SourceClass sourceClass)</span> <span class="keyword">throws</span> IOException &#123;</span><br><span class="line">    Set&lt;SourceClass&gt; imports = <span class="keyword">new</span> <span class="title class_">LinkedHashSet</span>&lt;SourceClass&gt;();</span><br><span class="line">    Set&lt;SourceClass&gt; visited = <span class="keyword">new</span> <span class="title class_">LinkedHashSet</span>&lt;SourceClass&gt;();</span><br><span class="line">    collectImports(sourceClass, imports, visited);</span><br><span class="line">    <span class="keyword">return</span> imports;</span><br><span class="line">&#125;</span><br><span class="line"></span><br><span class="line"><span class="comment">// 递归地收集要导入的目标（包装为 SourceClass）</span></span><br><span class="line"><span class="keyword">private</span> <span class="keyword">void</span> <span class="title function_">collectImports</span><span class="params">(SourceClass sourceClass, Set&lt;SourceClass&gt; imports, Set&lt;SourceClass&gt; visited)</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">// 如果 sourceClass 尚未访问过</span></span><br><span class="line">    <span class="keyword">if</span> (visited.add(sourceClass)) &#123;</span><br><span class="line">        <span class="comment">// 遍历 sourceClass 上的注解</span></span><br><span class="line">        <span class="keyword">for</span> (SourceClass annotation : sourceClass.getAnnotations()) &#123;</span><br><span class="line">            <span class="type">String</span> <span class="variable">annName</span> <span class="operator">=</span> annotation.getMetadata().getClassName();</span><br><span class="line">            <span class="comment">// 只要注解的名称不是 java 开头或者不是 Import 注解</span></span><br><span class="line">            <span class="keyword">if</span> (!annName.startsWith(<span class="string">&quot;java&quot;</span>) &amp;&amp; !annName.equals(Import.class.getName())) &#123;</span><br><span class="line">                <span class="comment">// 将该注解作为 sourceClass 递归地调用</span></span><br><span class="line">                collectImports(annotation, imports, visited);</span><br><span class="line">            &#125;</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="comment">// 将 Import 注解的 value 的值转换为 sourceClass 加入 imports</span></span><br><span class="line">        imports.addAll(sourceClass.getAnnotationAttributes(Import.class.getName(), <span class="string">&quot;value&quot;</span>));</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<p>这时候，并不区分要导入的目标的 <code>Class</code> 有什么特别之处，<code>Import</code> 注解的语义，此时宽泛地说就是：“将 <code>value</code> 中的类导入”。但是显而易见，这样的方式不够灵活，因此才有了另外两种更有灵活性的导入方式：<code>ImportSelector</code> 和 <code>ImportBeanDefinitionRegistrar</code>，<code>Spring</code> 最终不会真的注册这两种类，而是注册它们“介绍”的类，相当于把确定导入什么类的工作委托给它们。</p>
+<h3 id="处理要导入的目标"><a href="#处理要导入的目标" class="headerlink" title="处理要导入的目标"></a>处理要导入的目标</h3><p><code>processImports</code> 方法是处理 <code>Import</code> 注解的核心方法，这里的处理逻辑就对应着 <code>Import</code> 注解的三种使用方式。主要步骤如下：</p>
+<ul>
+<li>检测要导入的候选者不为空</li>
+<li>判断是否要检测循环导入以及是否存在循环导入</li>
+<li>处理要导入的候选者<ul>
+<li>如果是 <code>ImportSelector</code> 类型，调用 <code>selectImports</code> 方法获取新的要导入的目标，递归调用 <code>processImports</code> 处理</li>
+<li>如果是 <code>ImportBeanDefinitionRegistrar</code> 类型，添加到配置模型 <code>configClass</code>（出口 <code>1</code>）</li>
+<li>如果是其他剩余情况，作为配置类处理（出口 <code>2</code>）</li>
+</ul>
+</li>
+</ul>
+<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><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><span class="line">75</span><br><span class="line">76</span><br><span class="line">77</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">private</span> <span class="keyword">void</span> <span class="title function_">processImports</span><span class="params">(ConfigurationClass configClass, SourceClass currentSourceClass,</span></span><br><span class="line"><span class="params">			Collection&lt;SourceClass&gt; importCandidates, <span class="type">boolean</span> checkForCircularImports)</span> <span class="keyword">throws</span> IOException &#123;</span><br><span class="line">    <span class="comment">// 如果要导入的目标为空，直接返回</span></span><br><span class="line">    <span class="keyword">if</span> (importCandidates.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="keyword">if</span> (checkForCircularImports &amp;&amp; isChainedImportOnStack(configClass)) &#123;</span><br><span class="line">        <span class="comment">// 如果要检查循环导入，且确实存在循环导入，则抛出异常</span></span><br><span class="line">        <span class="built_in">this</span>.problemReporter.error(<span class="keyword">new</span> <span class="title class_">CircularImportProblem</span>(configClass, <span class="built_in">this</span>.importStack));</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">// 将配置模型放入 importStack，用于检查循环导入</span></span><br><span class="line">        <span class="built_in">this</span>.importStack.push(configClass);</span><br><span class="line">        <span class="keyword">try</span> &#123;</span><br><span class="line">            <span class="comment">// 遍历每一个准备导入的目标</span></span><br><span class="line">            <span class="keyword">for</span> (SourceClass candidate : importCandidates) &#123;</span><br><span class="line">                <span class="comment">// 如果是 ImportSelector 类型，委托给它确定导入目标</span></span><br><span class="line">                <span class="keyword">if</span> (candidate.isAssignable(ImportSelector.class)) &#123;</span><br><span class="line">                    <span class="comment">// 加载类</span></span><br><span class="line">                    Class&lt;?&gt; candidateClass = candidate.loadClass();</span><br><span class="line">                    <span class="comment">// 实例化得到 ImportSelector 实例</span></span><br><span class="line">                    <span class="type">ImportSelector</span> <span class="variable">selector</span> <span class="operator">=</span> BeanUtils.instantiateClass(candidateClass, ImportSelector.class);</span><br><span class="line">                    <span class="comment">// 调用其 Aware 接口</span></span><br><span class="line">                    ParserStrategyUtils.invokeAwareMethods(</span><br><span class="line">                            selector, <span class="built_in">this</span>.environment, <span class="built_in">this</span>.resourceLoader, <span class="built_in">this</span>.registry);</span><br><span class="line">                    <span class="keyword">if</span> (<span class="built_in">this</span>.deferredImportSelectors != <span class="literal">null</span> &amp;&amp; selector <span class="keyword">instanceof</span> DeferredImportSelector) &#123;</span><br><span class="line">                        <span class="comment">// 如果是 DeferredImportSelector 类型，存入 deferredImportSelectors 推迟调用</span></span><br><span class="line">                        <span class="built_in">this</span>.deferredImportSelectors.add(</span><br><span class="line">                                <span class="keyword">new</span> <span class="title class_">DeferredImportSelectorHolder</span>(configClass, (DeferredImportSelector) selector));</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">// 调用 selectImports 方法，返回要导入的目标的全限定类名</span></span><br><span class="line">                        String[] importClassNames = selector.selectImports(currentSourceClass.getMetadata());</span><br><span class="line">                        <span class="comment">// 包装为 SourceClass</span></span><br><span class="line">                        Collection&lt;SourceClass&gt; importSourceClasses = asSourceClasses(importClassNames);</span><br><span class="line">                        <span class="comment">// 递归调用 processImports</span></span><br><span class="line">                        <span class="comment">// 从这里看，ImportSelector 本质上是更加灵活的 Import</span></span><br><span class="line">                        processImports(configClass, currentSourceClass, importSourceClasses, <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">// 如果是 ImportBeanDefinitionRegistrar 类型，委托给它注册额外的 BeanDefinitions</span></span><br><span class="line">                <span class="keyword">else</span> <span class="keyword">if</span> (candidate.isAssignable(ImportBeanDefinitionRegistrar.class)) &#123;</span><br><span class="line">                    <span class="comment">// 加载类</span></span><br><span class="line">                    Class&lt;?&gt; candidateClass = candidate.loadClass();</span><br><span class="line">                    <span class="comment">// 实例化得到 ImportBeanDefinitionRegistrar 实例</span></span><br><span class="line">                    <span class="type">ImportBeanDefinitionRegistrar</span> <span class="variable">registrar</span> <span class="operator">=</span></span><br><span class="line">                            BeanUtils.instantiateClass(candidateClass, ImportBeanDefinitionRegistrar.class);</span><br><span class="line">                    <span class="comment">// 调用其 Aware 接口</span></span><br><span class="line">                    ParserStrategyUtils.invokeAwareMethods(</span><br><span class="line">                            registrar, <span class="built_in">this</span>.environment, <span class="built_in">this</span>.resourceLoader, <span class="built_in">this</span>.registry);</span><br><span class="line">                    <span class="comment">// 添加到配置模型</span></span><br><span class="line">                    configClass.addImportBeanDefinitionRegistrar(registrar, currentSourceClass.getMetadata());</span><br><span class="line">                &#125;</span><br><span class="line">                <span class="comment">// 既不是 ImportSelector，也不是 ImportBeanDefinitionRegistrar 的其他剩余情况，将其视为被 Configuration 注解标注的配置类进行处理</span></span><br><span class="line">                <span class="keyword">else</span> &#123;</span><br><span class="line">                    <span class="built_in">this</span>.importStack.registerImport(</span><br><span class="line">                            currentSourceClass.getMetadata(), candidate.getMetadata().getClassName());</span><br><span class="line">                    <span class="comment">// asConfigClass 方法建立了 candidate importBy configClass 的关系</span></span><br><span class="line">                    processConfigurationClass(candidate.asConfigClass(configClass));</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> (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 process import candidates for configuration class [&quot;</span> +</span><br><span class="line">                    configClass.getMetadata().getClassName() + <span class="string">&quot;]&quot;</span>, ex);</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="keyword">finally</span> &#123;</span><br><span class="line">            <span class="comment">// pop 配置模型</span></span><br><span class="line">            <span class="built_in">this</span>.importStack.pop();</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="类型一：ImportSelector"><a href="#类型一：ImportSelector" class="headerlink" title="类型一：ImportSelector"></a>类型一：ImportSelector</h4><p>如果要导入的目标是 <code>ImportSelector</code> 类型，那么 <code>Spring</code> 将确定真正导入什么目标的工作委托给它，不导入目标本身，实际上只导入目标“介绍”的类。具体步骤是：</p>
+<ol>
+<li>先获取 <code>Class</code> 对象</li>
+<li>再实例化得到一个 <code>ImportSelector</code> 实例</li>
+<li>调用 <code>selectImports</code> 方法，该方法返回的是类的全限定名，这样就得到了真正要导入的目标</li>
+<li>再次递归调用 <code>processImports</code></li>
+</ol>
+<p><code>ImportSelector</code> 就像它名字的含义一样，本质上是一种导入选择器，是一种更加灵活的 <code>getImports</code> 方法。由于返回的目标可能属于三种情形中的任意一种，所以对这些目标的处理还是要回到 <code>processImports</code> 方法。可以说 <code>ImportSelector</code> 类型本身不是 <code>processImports</code> 方法的出口，它最终会转换为 <code>ImportBeanDefinitionRegistrar</code> 或其他剩余情况。</p>
+<p><code>ImportSelector</code> 灵活性的来源：</p>
+<ul>
+<li><code>selectImports</code> 的 <code>AnnotationMetadata</code> 参数，为它提供了根据注解信息返回要导入的目标的能力</li>
+<li><code>ImportSelector</code> 可以实现 <code>Aware</code> 接口，用以感知到一些容器级别的资源，如 <code>BeanFactory</code>，这为它提供了根据这些资源中的信息返回要导入的目标的能力</li>
+</ul>
+<h4 id="类型二：ImportBeanDefinitionRegistrar"><a href="#类型二：ImportBeanDefinitionRegistrar" class="headerlink" title="类型二：ImportBeanDefinitionRegistrar"></a>类型二：ImportBeanDefinitionRegistrar</h4><p>如果要导入的目标是 <code>ImportBeanDefinitionRegistrar</code>，它会和 <code>ImportSelector</code> 有些相似却又有所不同。<code>Spring</code> 同样将确定真正导入什么目标的工作委托给它，不导入目标本身，实际上只导入目标“介绍”的类。</p>
+<ol>
+<li>先获取 <code>Class</code> 对象</li>
+<li>再实例化得到一个 <code>ImportBeanDefinitionRegistrar</code> 实例</li>
+<li>添加到配置模型 <code>configClass</code> 的 <code>importBeanDefinitionRegistrars</code> 属性</li>
+</ol>
+<p><code>ImportBeanDefinitionRegistrar</code> 不像 <code>ImportSelector</code> 需要进一步处理，它本身就代表着一个返回出口，成为了配置模型的一部分。但是请注意，<code>registerBeanDefinitions</code> 方法此时并没有被调用。</p>
+<p><code>ImportBeanDefinitionRegistrar</code> 灵活性的来源：</p>
+<ul>
+<li><code>registerBeanDefinitions</code> 的 <code>AnnotationMetadata</code> 参数，为它提供了根据注解信息决定注册 <code>BeanDefinition</code> 的能力</li>
+<li><code>registerBeanDefinitions</code> 的 <code>BeanDefinitionRegistry</code> 参数，为它提供了根据 <code>BeanDefinitionRegistry</code> 中的信息决定注册 <code>BeanDefinition</code> 的能力</li>
+<li><code>ImportBeanDefinitionRegistrar</code> 可以实现 <code>Aware</code> 接口，用以感知到一些容器级别的资源，如 <code>BeanFactory</code>，这为它提供了根据这些资源中的信息返回要导入的目标的能力</li>
+</ul>
+<h4 id="类型三：其他剩余情况"><a href="#类型三：其他剩余情况" class="headerlink" title="类型三：其他剩余情况"></a>类型三：其他剩余情况</h4><p>如果要导入的目标属于既不是 <code>ImportSelector</code> 也不是 <code>ImportBeanDefinitionRegistrar</code> 的其他剩余情况，那么 <code>Spring</code> 将其视为被 <code>Configuration</code> 注解标注的配置类进行处理。这里的处理逻辑是，<code>Import</code> 注解导入的类可能不是一个普通的类，而是一个配置类，因此需要回到 <code>processConfigurationClass</code> 进行处理。<code>processConfigurationClass</code> 方法正是本文开头的 <code>doProcessConfigurationClass</code> 方法的调用方，这里有两个地方值得注意：</p>
+<ul>
+<li><code>Import</code> 注解产生的 <code>ConfigurationClass</code> 根据不同的情况需要合并或者被抛弃，显式声明比 Import 导入的优先级更高。</li>
+<li>其他剩余情况下，目标最终会转换为一个配置模型，添加到 <code>parser</code> 的 <code>configurationClasses</code> 属性。</li>
+</ul>
+<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></pre></td><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">// 判断是否跳过处理</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">// 如果配置模型已经存在</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="keyword">if</span> (existingClass != <span class="literal">null</span>) &#123;</span><br><span class="line">        <span class="comment">// 如果新的配置模型代表的类，是 Import 导入的</span></span><br><span class="line">        <span class="keyword">if</span> (configClass.isImported()) &#123;</span><br><span class="line">            <span class="comment">// 如果已存在的配置模型也是 Import 导入的</span></span><br><span class="line">            <span class="keyword">if</span> (existingClass.isImported()) &#123;</span><br><span class="line">                <span class="comment">// 合并它们的来源</span></span><br><span class="line">                <span class="comment">// 比如一个类 A 既被 Config1 上的 Import 注解导入，也被 Config2 上的 Import 导入</span></span><br><span class="line">                existingClass.mergeImportedBy(configClass);</span><br><span class="line">            &#125;</span><br><span class="line">            <span class="comment">// 否则忽略新的因为 Import 导入而产生的配置模型</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">// 使用显式定义的代替 Import 导入的（显式定义的和 Import 导入的有什么不同吗）</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">// 先递归地处理配置类和它的父类，因为配合各种注解，可能引入更多的类</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">// 一个配置类，本身最终被解析成配置模型（配置模型在后续将会解析出 BeanDefinition）</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>
+
+<h3 id="DeferredImportSelector-的调用时机"><a href="#DeferredImportSelector-的调用时机" class="headerlink" title="DeferredImportSelector 的调用时机"></a>DeferredImportSelector 的调用时机</h3><p>在解析完每一批（注释中说“全部”）的配置类后，会统一调用 <code>DeferredImportSelector</code>。它作为一个标记接口推迟了 <code>selectImports</code> 的时机，打破了处理顺序的限制，在方法被调用时，可以得到更加完整的信息。注释中说“在选择导入的目标是 <code>@Conditional</code> 时，这个类型的选择器会很有用”，但是我不太理解，因为这个时候，处理配置类得到的信息尚未转换为 <code>ImportSelector</code> 可以感知到的信息，不像 <code>ImportBeanDefinitionRegistrar</code>，它被调用的时机在最后，也因此可以感知到更多的信息。</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></pre></td><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="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">                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 class="comment">// 调用 DeferredImportSelectors</span></span><br><span class="line">    processDeferredImportSelectors();</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_">processDeferredImportSelectors</span><span class="params">()</span> &#123;</span><br><span class="line">    <span class="comment">// 获取处理这一批配置类获得的 DeferredImportSelectors</span></span><br><span class="line">    List&lt;DeferredImportSelectorHolder&gt; deferredImports = <span class="built_in">this</span>.deferredImportSelectors;</span><br><span class="line">    <span class="comment">// 清空</span></span><br><span class="line">    <span class="built_in">this</span>.deferredImportSelectors = <span class="literal">null</span>;</span><br><span class="line">    <span class="comment">// 排序</span></span><br><span class="line">    Collections.sort(deferredImports, DEFERRED_IMPORT_COMPARATOR);</span><br><span class="line">    <span class="comment">// 遍历</span></span><br><span class="line">    <span class="keyword">for</span> (DeferredImportSelectorHolder deferredImport : deferredImports) &#123;</span><br><span class="line">        <span class="type">ConfigurationClass</span> <span class="variable">configClass</span> <span class="operator">=</span> deferredImport.getConfigurationClass();</span><br><span class="line">        <span class="keyword">try</span> &#123;</span><br><span class="line">            <span class="comment">// 调用 selectImports 获取要导入的目标</span></span><br><span class="line">            String[] imports = deferredImport.getImportSelector().selectImports(configClass.getMetadata());</span><br><span class="line">            <span class="comment">// 调用 processImports 处理要导入的目标，这里不管循环导入？竟然是任由 StackOverFlow</span></span><br><span class="line">            processImports(configClass, asSourceClass(configClass), asSourceClasses(imports), <span class="literal">false</span>);</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 process import candidates for configuration class [&quot;</span> +</span><br><span class="line">                    configClass.getMetadata().getClassName() + <span class="string">&quot;]&quot;</span>, 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>
+
+<h3 id="ImportBeanDefinitionRegistrar-的调用时机"><a href="#ImportBeanDefinitionRegistrar-的调用时机" class="headerlink" title="ImportBeanDefinitionRegistrar 的调用时机"></a>ImportBeanDefinitionRegistrar 的调用时机</h3><p><code>ConfigurationClassPostProcessor</code> 在每次解析得到新的一批配置模型后，都会调用 <code>ConfigurationClassBeanDefinitionReader</code> 的 <code>loadBeanDefinitions</code> 方法加载 <code>BeanDefinition</code>，在这过程的最后会从 <code>ImportBeanDefinitionRegistrar</code> 加载 <code>BeanDefinition</code>。这代表在处理同一批配置类时，在 <code>registerBeanDefinitions</code> 方法中总是能感知到以其他方式注册到 <code>BeanDefinitionRegistry</code> 中的 <code>BeanDefinition</code>，不论书面定义的顺序如何。</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></pre></td><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">// 遍历每一个配置模型</span></span><br><span class="line">    <span class="keyword">for</span> (ConfigurationClass configClass : configurationModel) &#123;</span><br><span class="line">        <span class="comment">// 从配置模型中加载 BeanDefinistion</span></span><br><span class="line">        loadBeanDefinitionsForConfigurationClass(configClass, trackedConditionEvaluator);</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_">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="comment">// 如果配置模型本身是导入的，为自身注册 BeanDefinition</span></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="comment">// 为 BeanMethod 加载 BeanDefinition（Bean 注解）</span></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">    <span class="comment">// 为 ImportResources 加载 BeanDefinition（ImportResource 注解）</span></span><br><span class="line">    loadBeanDefinitionsFromImportedResources(configClass.getImportedResources());</span><br><span class="line">    <span class="comment">// 从 ImportBeanDefinitionRegistrar 加载 BeanDefinition</span></span><br><span class="line">    loadBeanDefinitionsFromRegistrars(configClass.getImportBeanDefinitionRegistrars());</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_">loadBeanDefinitionsFromRegistrars</span><span class="params">(Map&lt;ImportBeanDefinitionRegistrar, AnnotationMetadata&gt; registrars)</span> &#123;</span><br><span class="line">    <span class="comment">// 遍历 ImportBeanDefinitionRegistrar 调用 registerBeanDefinitions 方法注册 BeanDefinition</span></span><br><span class="line">    <span class="keyword">for</span> (Map.Entry&lt;ImportBeanDefinitionRegistrar, AnnotationMetadata&gt; entry : registrars.entrySet()) &#123;</span><br><span class="line">        entry.getKey().registerBeanDefinitions(entry.getValue(), <span class="built_in">this</span>.registry);</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<h3 id="循环导入的检测"><a href="#循环导入的检测" class="headerlink" title="循环导入的检测"></a>循环导入的检测</h3><p>在处理导入的目标前将配置类放入 <code>importStack</code>，处理完毕移除。如果要导入的目标属于其他剩余情况时，注册被导入类-&gt;所有导入类集合的映射关系。</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></pre></td><td class="code"><pre><span class="line"><span class="keyword">private</span> <span class="keyword">void</span> <span class="title function_">processImports</span><span class="params">(ConfigurationClass configClass, SourceClass currentSourceClass,</span></span><br><span class="line"><span class="params">			Collection&lt;SourceClass&gt; importCandidates, <span class="type">boolean</span> checkForCircularImports)</span> <span class="keyword">throws</span> IOException &#123;</span><br><span class="line">    <span class="comment">// ...</span></span><br><span class="line">    <span class="keyword">if</span> (checkForCircularImports &amp;&amp; isChainedImportOnStack(configClass)) &#123;</span><br><span class="line">        <span class="comment">// 如果要检查循环导入，且确实存在循环导入，则抛出异常</span></span><br><span class="line">        <span class="built_in">this</span>.problemReporter.error(<span class="keyword">new</span> <span class="title class_">CircularImportProblem</span>(configClass, <span class="built_in">this</span>.importStack));</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">// 将配置模型放入 importStack，用于检查循环导入</span></span><br><span class="line">        <span class="built_in">this</span>.importStack.push(configClass);</span><br><span class="line">        <span class="keyword">try</span> &#123;</span><br><span class="line">            <span class="comment">// 遍历每一个准备导入的目标</span></span><br><span class="line">            <span class="keyword">for</span> (SourceClass candidate : importCandidates) &#123;</span><br><span class="line">                <span class="comment">// ...</span></span><br><span class="line">                <span class="keyword">else</span> &#123;</span><br><span class="line">                    <span class="comment">// 记录了被导入类-&gt;所有导入类集合的映射关系</span></span><br><span class="line">                    <span class="built_in">this</span>.importStack.registerImport(</span><br><span class="line">                            currentSourceClass.getMetadata(), candidate.getMetadata().getClassName());</span><br><span class="line">                    <span class="comment">// asConfigClass 方法建立了 candidate importBy configClass 的关系</span></span><br><span class="line">                    processConfigurationClass(candidate.asConfigClass(configClass));</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">        <span class="keyword">finally</span> &#123;</span><br><span class="line">            <span class="comment">// pop 配置模型</span></span><br><span class="line">            <span class="built_in">this</span>.importStack.pop();</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>检测是否发生循环导入。以当前类开始，循环向上查找最近一个导入自身的类，如果找到自身，说明发生循环导入。</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">private</span> <span class="type">boolean</span> <span class="title function_">isChainedImportOnStack</span><span class="params">(ConfigurationClass configClass)</span> &#123;</span><br><span class="line">    <span class="comment">// 如果 importStack 已存在该配置模型</span></span><br><span class="line">    <span class="keyword">if</span> (<span class="built_in">this</span>.importStack.contains(configClass)) &#123;</span><br><span class="line">        <span class="type">String</span> <span class="variable">configClassName</span> <span class="operator">=</span> configClass.getMetadata().getClassName();</span><br><span class="line">        <span class="comment">// 获取最新一个导入 configClass 的类</span></span><br><span class="line">        <span class="type">AnnotationMetadata</span> <span class="variable">importingClass</span> <span class="operator">=</span> <span class="built_in">this</span>.importStack.getImportingClassFor(configClassName);</span><br><span class="line">        <span class="comment">// 循环查找导入类的最近一个导入类，如果找到了自身，表示发生循环导入</span></span><br><span class="line">        <span class="keyword">while</span> (importingClass != <span class="literal">null</span>) &#123;</span><br><span class="line">            <span class="keyword">if</span> (configClassName.equals(importingClass.getClassName())) &#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">            importingClass = <span class="built_in">this</span>.importStack.getImportingClassFor(importingClass.getClassName());</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">false</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><table>
+<thead>
+<tr>
+<th></th>
+<th><code>ImportSelector</code></th>
+<th><code>ImportBeanDefinitionRegistrar</code></th>
+<th>其他剩余情况</th>
+</tr>
+</thead>
+<tbody><tr>
+<td>灵活性</td>
+<td>中</td>
+<td>高</td>
+<td>低</td>
+</tr>
+<tr>
+<td>处理结果</td>
+<td></td>
+<td>转换为配置模型的一部分</td>
+<td>转换为一个配置模型</td>
+</tr>
+<tr>
+<td>方法调用时机</td>
+<td>立即（或解析配置类的最后）</td>
+<td>加载 <code>BeanDefinition</code> 的最后</td>
+<td></td>
+</tr>
+<tr>
+<td>方法的结果</td>
+<td>获取 Import 目标</td>
+<td>直接注册 <code>BeanDefinition</code></td>
+<td></td>
+</tr>
+</tbody></table>
+
+      
+    </div>
+
+    
+    
+    
+
+    <footer class="post-footer">
+        <div class="post-eof"></div>
+      
+    </footer>
+  </article>
+</div>
+
+
+
+
+    
+
+
 <div class="post-block">
   
   
@@ -232,7 +460,7 @@ <h2 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：2023-12-04 16:27:13" itemprop="dateModified" datetime="2023-12-04T16:27:13+08:00">2023-12-04</time>
+      <time title="修改时间：2023-12-05 16:44:37" itemprop="dateModified" datetime="2023-12-05T16:44:37+08:00">2023-12-05</time>
     </span>
 
   
@@ -337,7 +565,7 @@ <h2 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：2023-12-04 16:27:13" itemprop="dateModified" datetime="2023-12-04T16:27:13+08:00">2023-12-04</time>
+      <time title="修改时间：2023-12-05 16:44:37" itemprop="dateModified" datetime="2023-12-05T16:44:37+08:00">2023-12-05</time>
     </span>
 
   
@@ -442,7 +670,7 @@ <h2 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：2023-12-04 16:27:13" itemprop="dateModified" datetime="2023-12-04T16:27:13+08:00">2023-12-04</time>
+      <time title="修改时间：2023-12-05 16:44:37" itemprop="dateModified" datetime="2023-12-05T16:44:37+08:00">2023-12-05</time>
     </span>
 
   
@@ -547,7 +775,7 @@ <h2 class="post-title" itemprop="name headline">
         <i class="far fa-calendar-check"></i>
       </span>
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@@ -1751,160 +1979,6 @@ <h4 id="mysqld-exporter-配置文件"><a href="#mysqld-exporter-配置文件" cl
 
 
 
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-  <article itemscope itemtype="http://schema.org/Article" class="post-content" lang="">
-    <link itemprop="mainEntityOfPage" href="https://www.moralok.com/2023/11/13/simple-implementation-of-distributed-lock-based-on-Redis/">
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-      <meta itemprop="image" content="/images/avatar.gif">
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-      <meta itemprop="name" content="Moralok">
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-      <meta itemprop="name" content="undefined | Moralok">
-      <meta itemprop="description" content="">
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-        <h2 class="post-title" itemprop="name headline">
-          <a href="/2023/11/13/simple-implementation-of-distributed-lock-based-on-Redis/" class="post-title-link" itemprop="url">基于 Redis 的分布式锁的简单实现</a>
-        </h2>
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-    <span class="post-meta-item">
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-      <time title="创建时间：2023-11-13 14:02:49" itemprop="dateCreated datePublished" datetime="2023-11-13T14:02:49+08:00">2023-11-13</time>
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-    </span>
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-  
-    <span id="/2023/11/13/simple-implementation-of-distributed-lock-based-on-Redis/" class="post-meta-item leancloud_visitors" data-flag-title="基于 Redis 的分布式锁的简单实现" title="阅读次数">
-      <span class="post-meta-item-icon">
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-      <span class="post-meta-item-text">阅读次数：</span>
-      <span class="leancloud-visitors-count"></span>
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-      <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>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>5 分钟</span>
-    </span>
-</div>
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-        </div>
-      </header>
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-    
-    
-    
-    <div class="post-body" itemprop="articleBody">
-          <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="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"><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="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></pre></td><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="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"><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="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">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="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"><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="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">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="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"><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="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">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="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></pre></td><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 target="_blank" rel="noopener" href="https://github.com/moralok/redis-lock">redis-lock</a></p>
-<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>《Redis 深度历险，核心原理与应用实践》</li>
-</ul>
-
-      
-    </div>
-
-    
-    
-    
-
-    <footer class="post-footer">
-        <div class="post-eof"></div>
-      
-    </footer>
-  </article>
-</div>
-
-
-
-
   <nav class="pagination">
     <span class="page-number current">1</span><a class="page-number" href="/page/2/">2</a><a class="page-number" href="/page/3/">3</a><a class="extend next" rel="next" href="/page/2/"><i class="fa fa-angle-right" aria-label="下一页"></i></a>
   </nav>
@@ -1929,13 +2003,13 @@ <h2 id="参考文章"><a href="#参考文章" class="headerlink" title="参考
     <span class="post-meta-item-icon">
       <i class="fa fa-chart-line"></i>
     </span>
-    <span title="站点总字数">74k</span>
+    <span title="站点总字数">77k</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">4:06</span>
+    <span title="站点阅读时长">4:18</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 015aa352..9bfb5dad 100644
--- a/leancloud_counter_security_urls.json
+++ b/leancloud_counter_security_urls.json
@@ -1 +1 @@
-[{"title":"在 Windows 10 上安装 OpenVPN 服务器","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":"在 Ubuntu 上安装 Clash","url":"/2023/05/27/how-to-install-clash-on-ubuntu/"},{"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":"Docker 常用命令列表","url":"/2020/08/19/docker-frequently-used-commands/"},{"title":"Tmux 常用命令和快捷键","url":"/2023/06/29/tmux-frequently-used-commands/"},{"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":"如何在 Ubuntu 20.04 上安装 Minikube","url":"/2023/06/23/how-to-install-Minikube-on-Ubuntu-20-04/"},{"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":"Spring 应用 context 刷新流程","url":"/2023/08/04/Spring-application-context-refresh-process/"},{"title":"字符串常量池的测试和分析","url":"/2023/11/03/testing-and-analysis-of-StringTable/"},{"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":"JVM 内存区域的测试和分析","url":"/2023/11/04/testing-and-analysis-of-jvm-memory-area/"},{"title":"使用 Grafana 和 Prometheus 搭建监控","url":"/2023/11/18/setup-monitoring-using-grafana-and-prometheus/"},{"title":"Java 垃圾收集","url":"/2023/11/07/garbage-collection-in-Java/"},{"title":"Spring AOP 如何创建代理 beans","url":"/2023/11/19/how-does-Spring-AOP-create-proxy-beans/"},{"title":"JDK 动态代理和 CGLib","url":"/2023/11/19/JDK-dynamic-proxy-and-CGLib/"},{"title":"Spring 中的循环依赖","url":"/2023/11/22/circular-dependencies-in-Spring/"},{"title":"Java 类加载器源码分析","url":"/2023/07/13/Java-class-loader-source-code-analysis/"},{"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 的工作原理","url":"/2023/11/28/how-does-Dubbo-SPI-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 @Configuration 注解的源码分析","url":"/2023/11/23/source-code-analysis-of-Spring-Configuration-annotation/"},{"title":"Dubbo SPI 自适应拓展的工作原理","url":"/2023/11/29/how-does-Dubbo-SPI-adaptive-extension-works/"}]
\ No newline at end of file
+[{"title":"在 Ubuntu 上安装 Clash","url":"/2023/05/27/how-to-install-clash-on-ubuntu/"},{"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 Windows 10 上安装 OpenVPN 服务器","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":"Docker 常用命令列表","url":"/2020/08/19/docker-frequently-used-commands/"},{"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":"Spring 应用 context 刷新流程","url":"/2023/08/04/Spring-application-context-refresh-process/"},{"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":"Java 类加载器源码分析","url":"/2023/07/13/Java-class-loader-source-code-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":"字符串常量池的测试和分析","url":"/2023/11/03/testing-and-analysis-of-StringTable/"},{"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":"Java 垃圾收集","url":"/2023/11/07/garbage-collection-in-Java/"},{"title":"使用 Grafana 和 Prometheus 搭建监控","url":"/2023/11/18/setup-monitoring-using-grafana-and-prometheus/"},{"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":"JDK 动态代理和 CGLib","url":"/2023/11/19/JDK-dynamic-proxy-and-CGLib/"},{"title":"Spring 中的循环依赖","url":"/2023/11/22/circular-dependencies-in-Spring/"},{"title":"Spring AOP 如何创建代理 beans","url":"/2023/11/19/how-does-Spring-AOP-create-proxy-beans/"},{"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":"Spring @Configuration 注解的源码分析","url":"/2023/11/23/source-code-analysis-of-Spring-Configuration-annotation/"},{"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/"}]
\ No newline at end of file
diff --git a/page/2/index.html b/page/2/index.html
index 3f48965a..6657a632 100644
--- a/page/2/index.html
+++ b/page/2/index.html
@@ -152,7 +152,7 @@ <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">28</span>
+          <span class="site-state-item-count">29</span>
           <span class="site-state-item-name">日志</span>
         </a>
       </div>
@@ -191,6 +191,160 @@ <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/2023/11/13/simple-implementation-of-distributed-lock-based-on-Redis/">
+
+    <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="Moralok's blog">
+    </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="/2023/11/13/simple-implementation-of-distributed-lock-based-on-Redis/" class="post-title-link" itemprop="url">基于 Redis 的分布式锁的简单实现</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：2023-11-13 14:02:49" itemprop="dateCreated datePublished" datetime="2023-11-13T14:02:49+08:00">2023-11-13</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：2023-12-05 16:44:37" itemprop="dateModified" datetime="2023-12-05T16:44:37+08:00">2023-12-05</time>
+    </span>
+
+  
+    <span id="/2023/11/13/simple-implementation-of-distributed-lock-based-on-Redis/" class="post-meta-item leancloud_visitors" data-flag-title="基于 Redis 的分布式锁的简单实现" 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>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>5 分钟</span>
+    </span>
+</div>
+
+        </div>
+      </header>
+
+    
+    
+    
+    <div class="post-body" itemprop="articleBody">
+          <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="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"><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="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></pre></td><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="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"><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="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">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="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"><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="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">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="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"><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="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">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="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></pre></td><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 target="_blank" rel="noopener" href="https://github.com/moralok/redis-lock">redis-lock</a></p>
+<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>《Redis 深度历险，核心原理与应用实践》</li>
+</ul>
+
+      
+    </div>
+
+    
+    
+    
+
+    <footer class="post-footer">
+        <div class="post-eof"></div>
+      
+    </footer>
+  </article>
+</div>
+
+
+
+
+    
+
+
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-      <time title="修改时间：2023-12-04 16:27:13" itemprop="dateModified" datetime="2023-12-04T16:27:13+08:00">2023-12-04</time>
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-      <time title="修改时间：2023-12-04 16:27:13" itemprop="dateModified" datetime="2023-12-04T16:27:13+08:00">2023-12-04</time>
+      <time title="修改时间：2023-12-05 16:44:37" itemprop="dateModified" datetime="2023-12-05T16:44:37+08:00">2023-12-05</time>
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-      <time title="修改时间：2023-12-04 16:27:13" itemprop="dateModified" datetime="2023-12-04T16:27:13+08:00">2023-12-04</time>
+      <time title="修改时间：2023-12-05 16:44:37" itemprop="dateModified" datetime="2023-12-05T16:44:37+08:00">2023-12-05</time>
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-      <time title="修改时间：2023-12-04 16:27:13" itemprop="dateModified" datetime="2023-12-04T16:27:13+08:00">2023-12-04</time>
+      <time title="修改时间：2023-12-05 16:44:37" itemprop="dateModified" datetime="2023-12-05T16:44:37+08:00">2023-12-05</time>
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-      <time title="修改时间：2023-12-04 16:27:13" itemprop="dateModified" datetime="2023-12-04T16:27:13+08:00">2023-12-04</time>
+      <time title="修改时间：2023-12-05 16:44:37" itemprop="dateModified" datetime="2023-12-05T16:44:37+08:00">2023-12-05</time>
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-    <span hidden itemprop="author" itemscope itemtype="http://schema.org/Person">
-      <meta itemprop="image" content="/images/avatar.gif">
-      <meta itemprop="name" content="Moralok">
-    </span>
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-      <meta itemprop="name" content="Moralok">
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-        <h2 class="post-title" itemprop="name headline">
-          <a href="/2023/06/28/how-to-use-ssh-to-connect-github-and-server/" class="post-title-link" itemprop="url">如何使用 SSH 连接 Github 和服务器</a>
-        </h2>
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-      <time title="创建时间：2023-06-29 04:36:35" itemprop="dateCreated datePublished" datetime="2023-06-29T04:36:35+08:00">2023-06-29</time>
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-      <time title="修改时间：2023-12-04 16:27:13" itemprop="dateModified" datetime="2023-12-04T16:27:13+08:00">2023-12-04</time>
-    </span>
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-  
-    <span id="/2023/06/28/how-to-use-ssh-to-connect-github-and-server/" class="post-meta-item leancloud_visitors" data-flag-title="如何使用 SSH 连接 Github 和服务器" title="阅读次数">
-      <span class="post-meta-item-icon">
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-      <span class="post-meta-item-text">本文字数：</span>
-      <span>1.1k</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>4 分钟</span>
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-          <h2 id="使用-SSH-连接-Github"><a href="#使用-SSH-连接-Github" class="headerlink" title="使用 SSH 连接 Github"></a>使用 SSH 连接 Github</h2><h3 id="检查现有-SSH-密钥"><a href="#检查现有-SSH-密钥" class="headerlink" title="检查现有 SSH 密钥"></a>检查现有 SSH 密钥</h3><p>打开终端，输入 <code>ls -al ~/.ssh</code> 以查看是否存在现有的 SSH 密钥。</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></pre></td><td class="code"><pre><span class="line"><span class="meta prompt_">$ </span><span class="language-bash"><span class="built_in">ls</span> -al ~/.ssh</span></span><br><span class="line">total 16</span><br><span class="line">drwx------ 2 wrmao wrmao 4096 Jun 28 20:19 .</span><br><span class="line">drwxr-xr-x 6 wrmao wrmao 4096 Jun 28 20:13 ..</span><br><span class="line">-rw------- 1 wrmao wrmao  106 Jun 28 20:07 authorized_keys</span><br><span class="line">-rw-r--r-- 1 wrmao wrmao  444 Jun 28 20:19 known_hosts</span><br></pre></td></tr></table></figure>
-<p>检查目录列表以查看是否已经有 SSH 公钥。 默认情况下，GitHub 的一个支持的公钥的文件名是以下之一。</p>
-<ul>
-<li>id_rsa.pub</li>
-<li>id_ecdsa.pub</li>
-<li>id_ed25519.pub</li>
-</ul>
-<h3 id="生成-SSH-密钥"><a href="#生成-SSH-密钥" class="headerlink" title="生成 SSH 密钥"></a>生成 SSH 密钥</h3><p>如果没有密钥，就需要生成新的 SSH 密钥；如果已有，跳到上传已有密钥环节。<br>打开终端，粘贴下面的文本（替换为你的 GitHub 电子邮件地址），这将以提供的电子邮件地址为标签创建新 SSH 密钥。<br>一直 yes 确定选择默认即可。</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"><span class="meta prompt_">$ </span><span class="language-bash">ssh-keygen -t ed25519 -C <span class="string">&quot;your_email@example.com&quot;</span></span></span><br><span class="line">Generating public/private ed25519 key pair.</span><br><span class="line">Enter file in which to save the key (/home/your-user/.ssh/id_ed25519):</span><br></pre></td></tr></table></figure>
-
-<h3 id="上传-SSH-密钥"><a href="#上传-SSH-密钥" class="headerlink" title="上传 SSH 密钥"></a>上传 SSH 密钥</h3><p>将 SSH 公钥复制到剪贴板，在 Github 上的 <code>Settings</code> - <code>Access</code> - <code>SSH and GPG keys</code> - <code>New SSH key</code>，粘贴即可。</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"><span class="meta prompt_">$ </span><span class="language-bash"><span class="built_in">cat</span> ~/.ssh/id_ed25519.pub</span></span><br></pre></td></tr></table></figure>
-
-<h3 id="配置-Git"><a href="#配置-Git" class="headerlink" title="配置 Git"></a>配置 Git</h3><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"><span class="meta prompt_">$ </span><span class="language-bash">git config --global user.name <span class="string">&quot;moralok&quot;</span></span></span><br><span class="line"><span class="meta prompt_">$ </span><span class="language-bash">git config --global user.email <span class="string">&quot;wrmao.public@outlook.com&quot;</span></span></span><br></pre></td></tr></table></figure>
-
-
-<h2 id="SSH-的原理"><a href="#SSH-的原理" class="headerlink" title="SSH 的原理"></a>SSH 的原理</h2><h3 id="关于-SSH"><a href="#关于-SSH" class="headerlink" title="关于 SSH"></a>关于 SSH</h3><p>使用 SSH 协议可以连接远程服务器和服务并向它们验证，而无需在每次访问时都提供用户名和密码，Github 还可以使用 SSH 密钥对提交进行签名。</p>
-<h3 id="公钥和私钥"><a href="#公钥和私钥" class="headerlink" title="公钥和私钥"></a>公钥和私钥</h3><p>SSH 的使用（非对称加密）需要生成公钥 public key 和私钥 private key。常用的算法有 <code>rsa</code>、<code>ecdsa</code> 和 <code>ed25519</code>，相对应的公钥默认文件名即id_XXX.pub。<code>ed25519</code> 的安全性介于 <code>rsa 2048</code> 和 <code>rsa 4096</code> 之间，但性能却提升数十倍。<br>在生成密钥时，会要求你 <code>Enter passphrase (empty for no passphrase):</code>，可以输入一个口令保护私钥的使用。不为空的情况下，正常使用是需要输入这个口令的，很多人认为麻烦，因此留空。<br>公钥的权限必须是 644，私钥的权限必须是 600，否则 SSH 认为其不可靠。<br>私钥是要安全保管在客户端不能泄露的，公钥则要提供给远程服务器或服务。服务端的 <code>~/.ssh/authorized_keys</code> 里面存储着可以登录的客户端的公钥。我们将公钥粘贴到 Github 的过程就是对应于此。</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"><span class="meta prompt_">$ </span><span class="language-bash">ssh-keygen -t rsa -b 4096 -f my_id -C <span class="string">&quot;email@example.com&quot;</span></span></span><br></pre></td></tr></table></figure>
-<ul>
-<li><code>-t</code> 表示算法，如 <code>rsa</code>。</li>
-<li><code>-b</code> 表示 <code>rsa</code> 密钥长度，默认 2048 bit，<code>ed25519</code> 不需要指定。</li>
-<li><code>-f</code> 表示文件名。</li>
-<li><code>-C</code> 表示在公钥文件中添加注释，可修改</li>
-</ul>
-<h3 id="SSH-公钥登录过程"><a href="#SSH-公钥登录过程" class="headerlink" title="SSH 公钥登录过程"></a>SSH 公钥登录过程</h3><ol>
-<li>Client 将自己的公钥存放到服务端，追加到 authorized_keys 文件。</li>
-<li>Server 收到 Client 的连接请求后，会在 authorized_keys 文件中匹配到 Client 传过来的公钥，并生成随机数 R，用公钥对随机数加密得到 pubKey(R)。</li>
-<li>Client 收到后通过私钥解密得到随机数 R，然后对随机数 R 和本次会话的 sessionKey 使用 MD5 生成摘要 Digest1，发送给服务端。</li>
-<li>Server 会对随机数 R 和会话的 sessionKey 同样使用 MD5 生成摘要 Digest2，对比相同即完成认证过程。</li>
-</ol>
-<h3 id="避免中间人攻击"><a href="#避免中间人攻击" class="headerlink" title="避免中间人攻击"></a>避免中间人攻击</h3><p>SSH 通过口令确认避免中间人攻击，如果用户第一次登录 Server，系统会提示：</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></pre></td><td class="code"><pre><span class="line"><span class="meta prompt_">$ </span><span class="language-bash">ssh -T git@github.com</span></span><br><span class="line">The authenticity of host &#x27;github.com (20.205.243.166)&#x27; can&#x27;t be established.</span><br><span class="line">ECDSA key fingerprint is SHA256:p2QAMXNIC1TJYWeIOttrVc98/R1BUFWu3/LiyKgUfQM.</span><br><span class="line">Are you sure you want to continue connecting (yes/no/[fingerprint])? yes</span><br><span class="line">Warning: Permanently added &#x27;github.com,20.205.243.166&#x27; (ECDSA) to the list of known hosts.</span><br><span class="line">Hi $&#123;username&#125;! You&#x27;ve successfully authenticated, but GitHub does not provide shell access.</span><br></pre></td></tr></table></figure>
-<p>Server 需要在其网站上公示其公钥的指纹，Github 的公钥指纹<a target="_blank" rel="noopener" href="https://docs.github.com/zh/authentication/keeping-your-account-and-data-secure/githubs-ssh-key-fingerprints">在这里</a>。<br>确认匹配后，客户端会在 <code>~/.ssh/known_hosts</code> 中记录，下次登录不再警告。</p>
-<h2 id="使用-SSH-免密登录服务器"><a href="#使用-SSH-免密登录服务器" class="headerlink" title="使用 SSH 免密登录服务器"></a>使用 SSH 免密登录服务器</h2><p>使用现成的密钥，将 <code>~/.ssh/id_ed25519.pub</code> 的内容追加到自己服务端的 <code>~/.ssh/authorized_keys</code> 中，使用 <code>ssh user@host</code> 成功免密登录。<br>这样一来，使用 VScode 远程连接服务器和使用 Remote Explorer 打开文件夹时，不用每次都输入密码了。</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 target="_blank" rel="noopener" href="https://docs.github.com/zh/authentication/connecting-to-github-with-ssh/about-ssh">使用 SSH 进行连接 Github</a><br><a target="_blank" rel="noopener" href="https://blog.csdn.net/u012408797/article/details/116196831">Git 多台电脑共用SSH Key</a><br><a target="_blank" rel="noopener" href="https://blog.csdn.net/neo949332116/article/details/102926051">SSH协议登录过程详解</a><br><a target="_blank" rel="noopener" href="https://docs.github.com/zh/authentication/keeping-your-account-and-data-secure/githubs-ssh-key-fingerprints">GitHub 的 SSH 密钥指纹</a><br><a target="_blank" rel="noopener" href="https://zhuanlan.zhihu.com/p/110413836">使用 Ed25519 算法生成你的 SSH 密钥</a></p>
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     <a class="extend prev" rel="prev" href="/"><i class="fa fa-angle-left" aria-label="上一页"></i></a><a class="page-number" href="/">1</a><span class="page-number current">2</span><a class="page-number" href="/page/3/">3</a><a class="extend next" rel="next" href="/page/3/"><i class="fa fa-angle-right" aria-label="下一页"></i></a>
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@@ -2347,13 +2367,13 @@ <h2 id="参考链接"><a href="#参考链接" class="headerlink" title="参考
     <span class="post-meta-item-icon">
       <i class="fa fa-chart-line"></i>
     </span>
-    <span title="站点总字数">74k</span>
+    <span title="站点总字数">77k</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">4:06</span>
+    <span title="站点阅读时长">4:18</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 76466bb7..352709bd 100644
--- a/page/3/index.html
+++ b/page/3/index.html
@@ -152,7 +152,7 @@ <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">28</span>
+          <span class="site-state-item-count">29</span>
           <span class="site-state-item-name">日志</span>
         </a>
       </div>
@@ -191,6 +191,140 @@ <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/2023/06/28/how-to-use-ssh-to-connect-github-and-server/">
+
+    <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="Moralok's blog">
+    </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="/2023/06/28/how-to-use-ssh-to-connect-github-and-server/" class="post-title-link" itemprop="url">如何使用 SSH 连接 Github 和服务器</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：2023-06-29 04:36:35" itemprop="dateCreated datePublished" datetime="2023-06-29T04:36:35+08:00">2023-06-29</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：2023-12-05 16:44:37" itemprop="dateModified" datetime="2023-12-05T16:44:37+08:00">2023-12-05</time>
+    </span>
+
+  
+    <span id="/2023/06/28/how-to-use-ssh-to-connect-github-and-server/" class="post-meta-item leancloud_visitors" data-flag-title="如何使用 SSH 连接 Github 和服务器" 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>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>4 分钟</span>
+    </span>
+</div>
+
+        </div>
+      </header>
+
+    
+    
+    
+    <div class="post-body" itemprop="articleBody">
+          <h2 id="使用-SSH-连接-Github"><a href="#使用-SSH-连接-Github" class="headerlink" title="使用 SSH 连接 Github"></a>使用 SSH 连接 Github</h2><h3 id="检查现有-SSH-密钥"><a href="#检查现有-SSH-密钥" class="headerlink" title="检查现有 SSH 密钥"></a>检查现有 SSH 密钥</h3><p>打开终端，输入 <code>ls -al ~/.ssh</code> 以查看是否存在现有的 SSH 密钥。</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></pre></td><td class="code"><pre><span class="line"><span class="meta prompt_">$ </span><span class="language-bash"><span class="built_in">ls</span> -al ~/.ssh</span></span><br><span class="line">total 16</span><br><span class="line">drwx------ 2 wrmao wrmao 4096 Jun 28 20:19 .</span><br><span class="line">drwxr-xr-x 6 wrmao wrmao 4096 Jun 28 20:13 ..</span><br><span class="line">-rw------- 1 wrmao wrmao  106 Jun 28 20:07 authorized_keys</span><br><span class="line">-rw-r--r-- 1 wrmao wrmao  444 Jun 28 20:19 known_hosts</span><br></pre></td></tr></table></figure>
+<p>检查目录列表以查看是否已经有 SSH 公钥。 默认情况下，GitHub 的一个支持的公钥的文件名是以下之一。</p>
+<ul>
+<li>id_rsa.pub</li>
+<li>id_ecdsa.pub</li>
+<li>id_ed25519.pub</li>
+</ul>
+<h3 id="生成-SSH-密钥"><a href="#生成-SSH-密钥" class="headerlink" title="生成 SSH 密钥"></a>生成 SSH 密钥</h3><p>如果没有密钥，就需要生成新的 SSH 密钥；如果已有，跳到上传已有密钥环节。<br>打开终端，粘贴下面的文本（替换为你的 GitHub 电子邮件地址），这将以提供的电子邮件地址为标签创建新 SSH 密钥。<br>一直 yes 确定选择默认即可。</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"><span class="meta prompt_">$ </span><span class="language-bash">ssh-keygen -t ed25519 -C <span class="string">&quot;your_email@example.com&quot;</span></span></span><br><span class="line">Generating public/private ed25519 key pair.</span><br><span class="line">Enter file in which to save the key (/home/your-user/.ssh/id_ed25519):</span><br></pre></td></tr></table></figure>
+
+<h3 id="上传-SSH-密钥"><a href="#上传-SSH-密钥" class="headerlink" title="上传 SSH 密钥"></a>上传 SSH 密钥</h3><p>将 SSH 公钥复制到剪贴板，在 Github 上的 <code>Settings</code> - <code>Access</code> - <code>SSH and GPG keys</code> - <code>New SSH key</code>，粘贴即可。</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"><span class="meta prompt_">$ </span><span class="language-bash"><span class="built_in">cat</span> ~/.ssh/id_ed25519.pub</span></span><br></pre></td></tr></table></figure>
+
+<h3 id="配置-Git"><a href="#配置-Git" class="headerlink" title="配置 Git"></a>配置 Git</h3><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"><span class="meta prompt_">$ </span><span class="language-bash">git config --global user.name <span class="string">&quot;moralok&quot;</span></span></span><br><span class="line"><span class="meta prompt_">$ </span><span class="language-bash">git config --global user.email <span class="string">&quot;wrmao.public@outlook.com&quot;</span></span></span><br></pre></td></tr></table></figure>
+
+
+<h2 id="SSH-的原理"><a href="#SSH-的原理" class="headerlink" title="SSH 的原理"></a>SSH 的原理</h2><h3 id="关于-SSH"><a href="#关于-SSH" class="headerlink" title="关于 SSH"></a>关于 SSH</h3><p>使用 SSH 协议可以连接远程服务器和服务并向它们验证，而无需在每次访问时都提供用户名和密码，Github 还可以使用 SSH 密钥对提交进行签名。</p>
+<h3 id="公钥和私钥"><a href="#公钥和私钥" class="headerlink" title="公钥和私钥"></a>公钥和私钥</h3><p>SSH 的使用（非对称加密）需要生成公钥 public key 和私钥 private key。常用的算法有 <code>rsa</code>、<code>ecdsa</code> 和 <code>ed25519</code>，相对应的公钥默认文件名即id_XXX.pub。<code>ed25519</code> 的安全性介于 <code>rsa 2048</code> 和 <code>rsa 4096</code> 之间，但性能却提升数十倍。<br>在生成密钥时，会要求你 <code>Enter passphrase (empty for no passphrase):</code>，可以输入一个口令保护私钥的使用。不为空的情况下，正常使用是需要输入这个口令的，很多人认为麻烦，因此留空。<br>公钥的权限必须是 644，私钥的权限必须是 600，否则 SSH 认为其不可靠。<br>私钥是要安全保管在客户端不能泄露的，公钥则要提供给远程服务器或服务。服务端的 <code>~/.ssh/authorized_keys</code> 里面存储着可以登录的客户端的公钥。我们将公钥粘贴到 Github 的过程就是对应于此。</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"><span class="meta prompt_">$ </span><span class="language-bash">ssh-keygen -t rsa -b 4096 -f my_id -C <span class="string">&quot;email@example.com&quot;</span></span></span><br></pre></td></tr></table></figure>
+<ul>
+<li><code>-t</code> 表示算法，如 <code>rsa</code>。</li>
+<li><code>-b</code> 表示 <code>rsa</code> 密钥长度，默认 2048 bit，<code>ed25519</code> 不需要指定。</li>
+<li><code>-f</code> 表示文件名。</li>
+<li><code>-C</code> 表示在公钥文件中添加注释，可修改</li>
+</ul>
+<h3 id="SSH-公钥登录过程"><a href="#SSH-公钥登录过程" class="headerlink" title="SSH 公钥登录过程"></a>SSH 公钥登录过程</h3><ol>
+<li>Client 将自己的公钥存放到服务端，追加到 authorized_keys 文件。</li>
+<li>Server 收到 Client 的连接请求后，会在 authorized_keys 文件中匹配到 Client 传过来的公钥，并生成随机数 R，用公钥对随机数加密得到 pubKey(R)。</li>
+<li>Client 收到后通过私钥解密得到随机数 R，然后对随机数 R 和本次会话的 sessionKey 使用 MD5 生成摘要 Digest1，发送给服务端。</li>
+<li>Server 会对随机数 R 和会话的 sessionKey 同样使用 MD5 生成摘要 Digest2，对比相同即完成认证过程。</li>
+</ol>
+<h3 id="避免中间人攻击"><a href="#避免中间人攻击" class="headerlink" title="避免中间人攻击"></a>避免中间人攻击</h3><p>SSH 通过口令确认避免中间人攻击，如果用户第一次登录 Server，系统会提示：</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></pre></td><td class="code"><pre><span class="line"><span class="meta prompt_">$ </span><span class="language-bash">ssh -T git@github.com</span></span><br><span class="line">The authenticity of host &#x27;github.com (20.205.243.166)&#x27; can&#x27;t be established.</span><br><span class="line">ECDSA key fingerprint is SHA256:p2QAMXNIC1TJYWeIOttrVc98/R1BUFWu3/LiyKgUfQM.</span><br><span class="line">Are you sure you want to continue connecting (yes/no/[fingerprint])? yes</span><br><span class="line">Warning: Permanently added &#x27;github.com,20.205.243.166&#x27; (ECDSA) to the list of known hosts.</span><br><span class="line">Hi $&#123;username&#125;! You&#x27;ve successfully authenticated, but GitHub does not provide shell access.</span><br></pre></td></tr></table></figure>
+<p>Server 需要在其网站上公示其公钥的指纹，Github 的公钥指纹<a target="_blank" rel="noopener" href="https://docs.github.com/zh/authentication/keeping-your-account-and-data-secure/githubs-ssh-key-fingerprints">在这里</a>。<br>确认匹配后，客户端会在 <code>~/.ssh/known_hosts</code> 中记录，下次登录不再警告。</p>
+<h2 id="使用-SSH-免密登录服务器"><a href="#使用-SSH-免密登录服务器" class="headerlink" title="使用 SSH 免密登录服务器"></a>使用 SSH 免密登录服务器</h2><p>使用现成的密钥，将 <code>~/.ssh/id_ed25519.pub</code> 的内容追加到自己服务端的 <code>~/.ssh/authorized_keys</code> 中，使用 <code>ssh user@host</code> 成功免密登录。<br>这样一来，使用 VScode 远程连接服务器和使用 Remote Explorer 打开文件夹时，不用每次都输入密码了。</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 target="_blank" rel="noopener" href="https://docs.github.com/zh/authentication/connecting-to-github-with-ssh/about-ssh">使用 SSH 进行连接 Github</a><br><a target="_blank" rel="noopener" href="https://blog.csdn.net/u012408797/article/details/116196831">Git 多台电脑共用SSH Key</a><br><a target="_blank" rel="noopener" href="https://blog.csdn.net/neo949332116/article/details/102926051">SSH协议登录过程详解</a><br><a target="_blank" rel="noopener" href="https://docs.github.com/zh/authentication/keeping-your-account-and-data-secure/githubs-ssh-key-fingerprints">GitHub 的 SSH 密钥指纹</a><br><a target="_blank" rel="noopener" href="https://zhuanlan.zhihu.com/p/110413836">使用 Ed25519 算法生成你的 SSH 密钥</a></p>
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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/search.xml b/search.xml
index 0bcdd4a7..330cdc5e 100644
--- a/search.xml
+++ b/search.xml
@@ -1,64 +1,5 @@
 <?xml version="1.0" encoding="utf-8"?>
 <search>
-  <entry>
-    <title>在 Windows 10 上安装 OpenVPN 服务器</title>
-    <url>/2023/06/07/how-to-setup-OpenVPN-server-on-windows-10/</url>
-    <content><![CDATA[<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><p>从 <a href="https://openvpn.net/community-downloads/">OpenVPN 社区</a> 下载 Windows 64-bit MSI installer。本次安装的版本为 OpenVPN 2.6.4。</p>
-<blockquote>
-<p>注意事项：在选择安装类型时选择 Customize 而不要选择 Install Now。额外勾选 OpenVPN -&gt; OpenVPN Service -&gt; Entire feature will be installed on local hard drive 和 OpenSSL Utilities -&gt; EasyRSA 3 Certificate Management Scripts -&gt; Entire feature will be installed on local hard drive。</p>
-</blockquote>
-<p>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。<br>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 OpenVPN TAP-Windows6 和 OpenVPN Wintun。</p>
-<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><p>打开 Windows 10 终端程序。<br>进入 OpenVPN 默认安装目录中的 easy-rsa 目录。</p>
-<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>
-<p>执行命令进入 Easy-RSA 3 Shell</p>
-<figure class="highlight shell"><table><tr><td class="code"><pre><span class="line">.\EasyRSA-Start.bat</span><br></pre></td></tr></table></figure>
-<p>初始化公钥基础设施目录 pki</p>
-<figure class="highlight shell"><table><tr><td class="code"><pre><span class="line">./easyrsa init-pki</span><br></pre></td></tr></table></figure>
-<p>构建证书颁发机构（CA）密钥，CA 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 Common Name，输入主机名即可。创建的 ca.crt 保存在目录 <code>C：\Program Files\OpenVPN\easy-rsa\pki</code> 中，ca.key 保存在目录 <code>C：\Program Files\OpenVPN\easy-rsa\pki\private</code> 中。</p>
-<figure class="highlight shell"><table><tr><td class="code"><pre><span class="line">./easyrsa build-ca nopass</span><br></pre></td></tr></table></figure>
-<p>构建服务器证书和密钥。创建的 server.crt 保存在目录 <code>C：\Program Files\OpenVPN\easy-rsa\pki\issued</code> 中，server.key 保存在目录 <code>C：\Program Files\OpenVPN\easy-rsa\pki\private</code> 中。</p>
-<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>
-<p>构建客户端证书和密钥。创建的 client.crt 保存在目录 <code>C：\Program Files\OpenVPN\easy-rsa\pki\issued</code> 中，client.key 保存在目录 <code>C：\Program Files\OpenVPN\easy-rsa\pki\private</code> 中。</p>
-<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>
-<p>生成 Diffie-Hellman 参数</p>
-<figure class="highlight shell"><table><tr><td class="code"><pre><span class="line">./easyrsa gen-dh</span><br></pre></td></tr></table></figure>
-<p>从目录 <code>C：\Program Files\OpenVPN\sample-config</code> 复制服务端配置文件模板 server.ovpn 到目录 <code>C：\Program Files\OpenVPN\config</code> 中，修改以下配置：</p>
-<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>
-<p>端口号按需修改，默认为1194，需要保证 OpenVPN 的网络流量可以通过防火墙，设置 Windows 10 Defender 允许 OpenVPN 通过即可。dh2048.pem 修改为生成的文件名 dh.pem。取消注释 duplicate-cn，让多个客户端使用同一个客户端证书。注释掉 tls-auth ta.key 0。复制 ca.crt，dh.pem，server.crt 和 server.key 到目录 C：\Program Files\OpenVPN\config 中。</p>
-<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 OpenVPN，点击连接，系统提示分配 IP 10.8.0.1。按配置，每次 OpenVPN server 都将为自己分配 10.8.0.1。</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>
-      </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>
-    <content><![CDATA[<h2 id="安装-OpenVPN-Connect"><a href="#安装-OpenVPN-Connect" class="headerlink" title="安装 OpenVPN Connect"></a>安装 OpenVPN Connect</h2><p>macOS 访问<a href="https://openvpn.net/client-connect-vpn-for-mac-os/">官网下载</a>。<br>iOS 访问 <a href="https://itunes.apple.com/us/app/openvpn-connect/id590379981?mt=8">AppStore</a>，需要登录外区 Apple ID。</p>
-<h2 id="配置-OpenVPN-Connect"><a href="#配置-OpenVPN-Connect" class="headerlink" title="配置 OpenVPN Connect"></a>配置 OpenVPN Connect</h2><p>客户端提供了两种方式导入配置文件，一是通过 URL，建议 URL 仅限在私有网络内访问，二是通过其他方式例如邮件，下载为本地文件再导入。</p>
-<p>配置文件的组织方式又分为两种形式，一种是将 CA 根证书 ca.crt，客户端证书 client.crt，客户端密钥 client.key 的内容复制粘贴到 client.ovpn 中，形成一个联合配置文件；另一种是使用 openssl 将 CA 根证书 ca.crt，客户端证书 client.crt，客户端密钥 client.key 转换为 PKCS#12 文件，先后导入 client.ovpn12 和 client.ovpn。</p>
-<h3 id="单一-client-ovpn"><a href="#单一-client-ovpn" class="headerlink" title="单一 client.ovpn"></a>单一 client.ovpn</h3><p>从目录 <code>C：\Program Files\OpenVPN\sample-config</code> 复制客户端配置文件模板 client.ovpn，修改以下配置：</p>
-<figure class="highlight ini"><table><tr><td class="code"><pre><span class="line">remote your-server 1194</span><br><span class="line"></span><br><span class="line"><span class="comment">;ca ca.crt</span></span><br><span class="line"><span class="comment">;cert client.crt</span></span><br><span class="line"><span class="comment">;key client.key</span></span><br><span class="line"></span><br><span class="line"><span class="comment">;tls-auth ta.key 1</span></span><br><span class="line"></span><br><span class="line">&lt;ca&gt;</span><br><span class="line">-----BEGIN CERTIFICATE-----</span><br><span class="line">paste contents of ca.crt</span><br><span class="line">-----END CERTIFICATE-----</span><br><span class="line">&lt;/ca&gt;</span><br><span class="line">&lt;cert&gt;</span><br><span class="line">-----BEGIN CERTIFICATE-----</span><br><span class="line">paste contents of client.crt</span><br><span class="line">-----END CERTIFICATE-----</span><br><span class="line">&lt;/cert&gt;</span><br><span class="line">&lt;key&gt;</span><br><span class="line">-----BEGIN PRIVATE KEY-----</span><br><span class="line">paste contents of client.key</span><br><span class="line">-----END PRIVATE KEY-----</span><br><span class="line">&lt;/key&gt;</span><br></pre></td></tr></table></figure>
-<p>将 <code>remote your-server 1194</code> 中的地址和端口替换成你的 OpenVPN server 的地址和端口。将 <code>ca ca.crt</code>， <code>cert client.crt</code>， <code>key client.key</code>， <code>tls-auth ta.key 1</code> 注释掉，将各自文件中的内容以上述类 XML 的形式粘贴到 client.ovpn 中。</p>
-<p>将修改好的客户端配置文件导入到客户端中即可。</p>
-<h3 id="client-ovpn-client-opvn12"><a href="#client-ovpn-client-opvn12" class="headerlink" title="client.ovpn + client.opvn12"></a>client.ovpn + client.opvn12</h3><p>使用 openssl 命令将客户端的证书和私钥文件转换为 PKCS#12 形式的文件。该命令会提示 <code>Enter Export Password</code>，可以为空，但为了安全建议设置密码。</p>
-<figure class="highlight shell"><table><tr><td class="code"><pre><span class="line">openssl pkcs12 -export -in cert -inkey key -certfile ca -name MyClient -out client.ovpn12</span><br></pre></td></tr></table></figure>
-<p>由于在 iOS 中导入 PKCS#12 文件到 Keychain 中时只导入了客户端证书和密钥，CA 根证书并没有导入，client.ovpn 文件中必须要保留 CA 根证书的配置。<br>既可以用传统的引用文件的方式：</p>
-<figure class="highlight ini"><table><tr><td class="code"><pre><span class="line">ca ca.crt</span><br></pre></td></tr></table></figure>
-<p>也可以用类 XML 的形式粘贴 ca.crt 内容到 client.ovpn 中：</p>
-<figure class="highlight ini"><table><tr><td class="code"><pre><span class="line">&lt;ca&gt;</span><br><span class="line">paste contents of ca.crt here</span><br><span class="line">&lt;/ca&gt;</span><br></pre></td></tr></table></figure>
-<p>先导入 client.ovpn12（需要输入转换时的密码），再导入 client.ovpn。</p>
-<blockquote>
-<p>但是我失败了……导入 client.ovpn12 时密码一直错误，搜索到类似的案例，但是没有找到解决方案。不确定是不是 openssl 版本引起的。</p>
-</blockquote>
-<h2 id="路由器-NAT"><a href="#路由器-NAT" class="headerlink" title="路由器 NAT"></a>路由器 NAT</h2><p>在路由器管理后台的 NAT 设置功能里，配置好对外端口号和 Windows 10 主机上 OpenVPN 端口号的映射关系。</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://openvpn.net/vpn-server-resources/faq-regarding-openvpn-connect-ios/">iOS 使用 OpenVPN 的 FAQ</a><br><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><br><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></p>
-]]></content>
-      <tags>
-        <tag>openvpn</tag>
-      </tags>
-  </entry>
   <entry>
     <title>在 Ubuntu 上安装 Clash</title>
     <url>/2023/05/27/how-to-install-clash-on-ubuntu/</url>
@@ -104,6 +45,65 @@
         <tag>proxy</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>
+    <content><![CDATA[<h2 id="安装-OpenVPN-Connect"><a href="#安装-OpenVPN-Connect" class="headerlink" title="安装 OpenVPN Connect"></a>安装 OpenVPN Connect</h2><p>macOS 访问<a href="https://openvpn.net/client-connect-vpn-for-mac-os/">官网下载</a>。<br>iOS 访问 <a href="https://itunes.apple.com/us/app/openvpn-connect/id590379981?mt=8">AppStore</a>，需要登录外区 Apple ID。</p>
+<h2 id="配置-OpenVPN-Connect"><a href="#配置-OpenVPN-Connect" class="headerlink" title="配置 OpenVPN Connect"></a>配置 OpenVPN Connect</h2><p>客户端提供了两种方式导入配置文件，一是通过 URL，建议 URL 仅限在私有网络内访问，二是通过其他方式例如邮件，下载为本地文件再导入。</p>
+<p>配置文件的组织方式又分为两种形式，一种是将 CA 根证书 ca.crt，客户端证书 client.crt，客户端密钥 client.key 的内容复制粘贴到 client.ovpn 中，形成一个联合配置文件；另一种是使用 openssl 将 CA 根证书 ca.crt，客户端证书 client.crt，客户端密钥 client.key 转换为 PKCS#12 文件，先后导入 client.ovpn12 和 client.ovpn。</p>
+<h3 id="单一-client-ovpn"><a href="#单一-client-ovpn" class="headerlink" title="单一 client.ovpn"></a>单一 client.ovpn</h3><p>从目录 <code>C：\Program Files\OpenVPN\sample-config</code> 复制客户端配置文件模板 client.ovpn，修改以下配置：</p>
+<figure class="highlight ini"><table><tr><td class="code"><pre><span class="line">remote your-server 1194</span><br><span class="line"></span><br><span class="line"><span class="comment">;ca ca.crt</span></span><br><span class="line"><span class="comment">;cert client.crt</span></span><br><span class="line"><span class="comment">;key client.key</span></span><br><span class="line"></span><br><span class="line"><span class="comment">;tls-auth ta.key 1</span></span><br><span class="line"></span><br><span class="line">&lt;ca&gt;</span><br><span class="line">-----BEGIN CERTIFICATE-----</span><br><span class="line">paste contents of ca.crt</span><br><span class="line">-----END CERTIFICATE-----</span><br><span class="line">&lt;/ca&gt;</span><br><span class="line">&lt;cert&gt;</span><br><span class="line">-----BEGIN CERTIFICATE-----</span><br><span class="line">paste contents of client.crt</span><br><span class="line">-----END CERTIFICATE-----</span><br><span class="line">&lt;/cert&gt;</span><br><span class="line">&lt;key&gt;</span><br><span class="line">-----BEGIN PRIVATE KEY-----</span><br><span class="line">paste contents of client.key</span><br><span class="line">-----END PRIVATE KEY-----</span><br><span class="line">&lt;/key&gt;</span><br></pre></td></tr></table></figure>
+<p>将 <code>remote your-server 1194</code> 中的地址和端口替换成你的 OpenVPN server 的地址和端口。将 <code>ca ca.crt</code>， <code>cert client.crt</code>， <code>key client.key</code>， <code>tls-auth ta.key 1</code> 注释掉，将各自文件中的内容以上述类 XML 的形式粘贴到 client.ovpn 中。</p>
+<p>将修改好的客户端配置文件导入到客户端中即可。</p>
+<h3 id="client-ovpn-client-opvn12"><a href="#client-ovpn-client-opvn12" class="headerlink" title="client.ovpn + client.opvn12"></a>client.ovpn + client.opvn12</h3><p>使用 openssl 命令将客户端的证书和私钥文件转换为 PKCS#12 形式的文件。该命令会提示 <code>Enter Export Password</code>，可以为空，但为了安全建议设置密码。</p>
+<figure class="highlight shell"><table><tr><td class="code"><pre><span class="line">openssl pkcs12 -export -in cert -inkey key -certfile ca -name MyClient -out client.ovpn12</span><br></pre></td></tr></table></figure>
+<p>由于在 iOS 中导入 PKCS#12 文件到 Keychain 中时只导入了客户端证书和密钥，CA 根证书并没有导入，client.ovpn 文件中必须要保留 CA 根证书的配置。<br>既可以用传统的引用文件的方式：</p>
+<figure class="highlight ini"><table><tr><td class="code"><pre><span class="line">ca ca.crt</span><br></pre></td></tr></table></figure>
+<p>也可以用类 XML 的形式粘贴 ca.crt 内容到 client.ovpn 中：</p>
+<figure class="highlight ini"><table><tr><td class="code"><pre><span class="line">&lt;ca&gt;</span><br><span class="line">paste contents of ca.crt here</span><br><span class="line">&lt;/ca&gt;</span><br></pre></td></tr></table></figure>
+<p>先导入 client.ovpn12（需要输入转换时的密码），再导入 client.ovpn。</p>
+<blockquote>
+<p>但是我失败了……导入 client.ovpn12 时密码一直错误，搜索到类似的案例，但是没有找到解决方案。不确定是不是 openssl 版本引起的。</p>
+</blockquote>
+<h2 id="路由器-NAT"><a href="#路由器-NAT" class="headerlink" title="路由器 NAT"></a>路由器 NAT</h2><p>在路由器管理后台的 NAT 设置功能里，配置好对外端口号和 Windows 10 主机上 OpenVPN 端口号的映射关系。</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://openvpn.net/vpn-server-resources/faq-regarding-openvpn-connect-ios/">iOS 使用 OpenVPN 的 FAQ</a><br><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><br><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></p>
+]]></content>
+      <tags>
+        <tag>openvpn</tag>
+      </tags>
+  </entry>
+  <entry>
+    <title>在 Windows 10 上安装 OpenVPN 服务器</title>
+    <url>/2023/06/07/how-to-setup-OpenVPN-server-on-windows-10/</url>
+    <content><![CDATA[<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><p>从 <a href="https://openvpn.net/community-downloads/">OpenVPN 社区</a> 下载 Windows 64-bit MSI installer。本次安装的版本为 OpenVPN 2.6.4。</p>
+<blockquote>
+<p>注意事项：在选择安装类型时选择 Customize 而不要选择 Install Now。额外勾选 OpenVPN -&gt; OpenVPN Service -&gt; Entire feature will be installed on local hard drive 和 OpenSSL Utilities -&gt; EasyRSA 3 Certificate Management Scripts -&gt; Entire feature will be installed on local hard drive。</p>
+</blockquote>
+<p>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。<br>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 OpenVPN TAP-Windows6 和 OpenVPN Wintun。</p>
+<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><p>打开 Windows 10 终端程序。<br>进入 OpenVPN 默认安装目录中的 easy-rsa 目录。</p>
+<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>
+<p>执行命令进入 Easy-RSA 3 Shell</p>
+<figure class="highlight shell"><table><tr><td class="code"><pre><span class="line">.\EasyRSA-Start.bat</span><br></pre></td></tr></table></figure>
+<p>初始化公钥基础设施目录 pki</p>
+<figure class="highlight shell"><table><tr><td class="code"><pre><span class="line">./easyrsa init-pki</span><br></pre></td></tr></table></figure>
+<p>构建证书颁发机构（CA）密钥，CA 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 Common Name，输入主机名即可。创建的 ca.crt 保存在目录 <code>C：\Program Files\OpenVPN\easy-rsa\pki</code> 中，ca.key 保存在目录 <code>C：\Program Files\OpenVPN\easy-rsa\pki\private</code> 中。</p>
+<figure class="highlight shell"><table><tr><td class="code"><pre><span class="line">./easyrsa build-ca nopass</span><br></pre></td></tr></table></figure>
+<p>构建服务器证书和密钥。创建的 server.crt 保存在目录 <code>C：\Program Files\OpenVPN\easy-rsa\pki\issued</code> 中，server.key 保存在目录 <code>C：\Program Files\OpenVPN\easy-rsa\pki\private</code> 中。</p>
+<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>
+<p>构建客户端证书和密钥。创建的 client.crt 保存在目录 <code>C：\Program Files\OpenVPN\easy-rsa\pki\issued</code> 中，client.key 保存在目录 <code>C：\Program Files\OpenVPN\easy-rsa\pki\private</code> 中。</p>
+<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>
+<p>生成 Diffie-Hellman 参数</p>
+<figure class="highlight shell"><table><tr><td class="code"><pre><span class="line">./easyrsa gen-dh</span><br></pre></td></tr></table></figure>
+<p>从目录 <code>C：\Program Files\OpenVPN\sample-config</code> 复制服务端配置文件模板 server.ovpn 到目录 <code>C：\Program Files\OpenVPN\config</code> 中，修改以下配置：</p>
+<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>
+<p>端口号按需修改，默认为1194，需要保证 OpenVPN 的网络流量可以通过防火墙，设置 Windows 10 Defender 允许 OpenVPN 通过即可。dh2048.pem 修改为生成的文件名 dh.pem。取消注释 duplicate-cn，让多个客户端使用同一个客户端证书。注释掉 tls-auth ta.key 0。复制 ca.crt，dh.pem，server.crt 和 server.key 到目录 C：\Program Files\OpenVPN\config 中。</p>
+<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 OpenVPN，点击连接，系统提示分配 IP 10.8.0.1。按配置，每次 OpenVPN server 都将为自己分配 10.8.0.1。</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>
+      </tags>
+  </entry>
   <entry>
     <title>使用 OpenVPN 访问家庭内网</title>
     <url>/2023/06/07/how-to-use-OpenVPN-to-access-home-network/</url>
@@ -163,80 +163,6 @@
         <tag>openvpn</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>
-
-<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>proxy</tag>
-        <tag>docker</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>最近在本地测试 Kubesphere 和 Minikube，使用 Ubuntu server 20.04 搭建了多个虚拟机，磁盘空间紧张。注意到安装后，磁盘空间仅占据分配的一半左右。<br>如果 Ubuntu server 20.04 安装时使用默认的 lvm 选项，就会出现这种情况。</p>
-<p>分配了 40GB 磁盘空间，可用仅 19GB。</p>
-<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>
-
-<p>查看发现 Free  PE &#x2F; Size 还有 19GB。</p>
-<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>
-
-<p>重新分配空间。</p>
-<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><span class="line"><span class="meta prompt_"></span></span><br><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>
-
-<p>再次查看。</p>
-<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>
-
-<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>ubuntu</tag>
-      </tags>
-  </entry>
   <entry>
     <title>Docker 常用命令列表</title>
     <url>/2020/08/19/docker-frequently-used-commands/</url>
@@ -690,113 +616,77 @@
       </tags>
   </entry>
   <entry>
-    <title>Tmux 常用命令和快捷键</title>
-    <url>/2023/06/29/tmux-frequently-used-commands/</url>
-    <content><![CDATA[<h2 id="Tmux-是什么"><a href="#Tmux-是什么" class="headerlink" title="Tmux 是什么"></a>Tmux 是什么</h2><p>Tmux 是一个终端复用器（Terminal Multiplexer），它可以将终端的会话和窗口解绑分离，达到窗口关闭，会话不终止，并且还能使用窗口再次绑定目标会话的效果，从而避免因为网络中断或者窗口关闭导致会话中运行的进程终止。</p>
-<h2 id="基本用法"><a href="#基本用法" class="headerlink" title="基本用法"></a>基本用法</h2><p>Ubuntu server 20.04 默认已安装 Tmux。如果没有，可以通过以下命令安装：</p>
-<figure class="highlight shell"><table><tr><td class="code"><pre><span class="line"><span class="meta prompt_">$ </span><span class="language-bash">sudo apt-get install tmux</span></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>
 
-<h3 id="会话管理"><a href="#会话管理" class="headerlink" title="会话管理"></a>会话管理</h3><h4 id="新建会话"><a href="#新建会话" class="headerlink" title="新建会话"></a>新建会话</h4><figure class="highlight shell"><table><tr><td class="code"><pre><span class="line"><span class="meta prompt_">$ </span><span class="language-bash">tmux new -s &lt;session-name&gt;</span></span><br></pre></td></tr></table></figure>
-<h4 id="分离会话"><a href="#分离会话" class="headerlink" title="分离会话"></a>分离会话</h4><figure class="highlight shell"><table><tr><td class="code"><pre><span class="line"><span class="meta prompt_">$ </span><span class="language-bash">tmux detach</span></span><br></pre></td></tr></table></figure>
-<h4 id="查看会话列表"><a href="#查看会话列表" class="headerlink" title="查看会话列表"></a>查看会话列表</h4><figure class="highlight shell"><table><tr><td class="code"><pre><span class="line"><span class="meta prompt_">$ </span><span class="language-bash">tmux <span class="built_in">ls</span></span></span><br></pre></td></tr></table></figure>
-<h4 id="接入会话"><a href="#接入会话" class="headerlink" title="接入会话"></a>接入会话</h4><figure class="highlight shell"><table><tr><td class="code"><pre><span class="line"><span class="meta prompt_">$ </span><span class="language-bash">tmux attach -t &lt;session-name&gt;</span></span><br><span class="line"><span class="meta prompt_">$ </span><span class="language-bash">tmux attach -t &lt;session-id&gt;</span></span><br></pre></td></tr></table></figure>
-<h4 id="杀死会话"><a href="#杀死会话" class="headerlink" title="杀死会话"></a>杀死会话</h4><figure class="highlight shell"><table><tr><td class="code"><pre><span class="line"><span class="meta prompt_">$ </span><span class="language-bash">tmux kill-session -t &lt;session-name&gt;</span></span><br><span class="line"><span class="meta prompt_">$ </span><span class="language-bash">tmux kill-session -t &lt;session-id&gt;</span></span><br></pre></td></tr></table></figure>
-<h4 id="切换会话"><a href="#切换会话" class="headerlink" title="切换会话"></a>切换会话</h4><figure class="highlight shell"><table><tr><td class="code"><pre><span class="line"><span class="meta prompt_">$ </span><span class="language-bash">tmux switch -t &lt;session-name&gt;</span></span><br><span class="line"><span class="meta prompt_">$ </span><span class="language-bash">tmux switch -t &lt;session-id&gt;</span></span><br></pre></td></tr></table></figure>
-<h4 id="重命名会话"><a href="#重命名会话" class="headerlink" title="重命名会话"></a>重命名会话</h4><figure class="highlight shell"><table><tr><td class="code"><pre><span class="line"><span class="meta prompt_">$ </span><span class="language-bash">tmux rename-session -t &lt;old&gt; &lt;new&gt;</span></span><br><span class="line"><span class="meta prompt_">$ </span><span class="language-bash">tmux rename-session &lt;new&gt;</span></span><br></pre></td></tr></table></figure>
-<h4 id="会话快捷键"><a href="#会话快捷键" class="headerlink" title="会话快捷键"></a>会话快捷键</h4><ul>
-<li><strong><code>Ctrl+b d</code>：分离当前会话，猜测 detach</strong></li>
-<li><strong><code>Ctrl+b s</code>：查看会话列表并选择，session</strong></li>
-<li><strong><code>Ctrl+b $</code>：重命名当前会话名称</strong></li>
-<li><strong><code>Ctrl+d</code>：关闭当前会话</strong></li>
-</ul>
-<h3 id="窗口管理"><a href="#窗口管理" class="headerlink" title="窗口管理"></a>窗口管理</h3><h4 id="新建窗口"><a href="#新建窗口" class="headerlink" title="新建窗口"></a>新建窗口</h4><figure class="highlight shell"><table><tr><td class="code"><pre><span class="line"><span class="meta prompt_">$ </span><span class="language-bash">tmux new-window -n &lt;window-name&gt;</span></span><br></pre></td></tr></table></figure>
-<h4 id="关闭窗口"><a href="#关闭窗口" class="headerlink" title="关闭窗口"></a>关闭窗口</h4><figure class="highlight shell"><table><tr><td class="code"><pre><span class="line"><span class="meta prompt_">$ </span><span class="language-bash">tmux kill-window -t &lt;window-name&gt;</span></span><br><span class="line"><span class="meta prompt_">$ </span><span class="language-bash">tmux kill-window</span></span><br></pre></td></tr></table></figure>
-<h4 id="切换窗口"><a href="#切换窗口" class="headerlink" title="切换窗口"></a>切换窗口</h4><figure class="highlight shell"><table><tr><td class="code"><pre><span class="line"><span class="meta prompt_">$ </span><span class="language-bash">tmux select-window -t &lt;window-name&gt;</span></span><br><span class="line"><span class="meta prompt_">$ </span><span class="language-bash">tmux select-window -t &lt;window-id&gt;</span></span><br></pre></td></tr></table></figure>
-<h4 id="重命名窗口"><a href="#重命名窗口" class="headerlink" title="重命名窗口"></a>重命名窗口</h4><figure class="highlight shell"><table><tr><td class="code"><pre><span class="line"><span class="meta prompt_">$ </span><span class="language-bash">tmux rename-window -t &lt;old&gt; &lt;new&gt;</span></span><br><span class="line"><span class="meta prompt_">$ </span><span class="language-bash">tmux rename-window &lt;new&gt;</span></span><br></pre></td></tr></table></figure>
-<h4 id="窗口快捷键"><a href="#窗口快捷键" class="headerlink" title="窗口快捷键"></a>窗口快捷键</h4><ul>
-<li><strong><code>Ctrl+b c</code>：创建一个新窗口，状态栏会显示窗口信息</strong></li>
-<li><code>Ctrl+b p</code>：切换到上一个窗口，prev</li>
-<li><code>Ctrl+b n</code>：切换到下一个窗口，next</li>
-<li><code>Ctrl+b &lt;number&gt;</code>：切换到指定编号的窗口</li>
-<li><strong><code>Ctrl+b w</code>：查看窗口列表并选择，window</strong></li>
-<li><strong><code>Ctrl+b ,</code>：重命名当前窗口</strong></li>
-<li><strong><code>Ctrl+b &amp;</code>：关闭当前窗口</strong></li>
-</ul>
-<h3 id="窗格管理"><a href="#窗格管理" class="headerlink" title="窗格管理"></a>窗格管理</h3><h4 id="划分窗格"><a href="#划分窗格" class="headerlink" title="划分窗格"></a>划分窗格</h4><p>猜测 vertical，horizontal。</p>
-<figure class="highlight shell"><table><tr><td class="code"><pre><span class="line"><span class="meta prompt_">$ </span><span class="language-bash">tmux split-window [-v]</span></span><br><span class="line"><span class="meta prompt_">$ </span><span class="language-bash">tmux split-window -h</span></span><br></pre></td></tr></table></figure>
-<h4 id="移动光标"><a href="#移动光标" class="headerlink" title="移动光标"></a>移动光标</h4><p>猜测 upper，down，left，right。</p>
-<figure class="highlight shell"><table><tr><td class="code"><pre><span class="line"><span class="meta prompt_">$ </span><span class="language-bash">tmux select-pane -U</span></span><br><span class="line"><span class="meta prompt_">$ </span><span class="language-bash">tmux select-pane -D</span></span><br><span class="line"><span class="meta prompt_">$ </span><span class="language-bash">tmux select-pane -L</span></span><br><span class="line"><span class="meta prompt_">$ </span><span class="language-bash">tmux select-pane -R</span></span><br></pre></td></tr></table></figure>
-<h4 id="交换窗格"><a href="#交换窗格" class="headerlink" title="交换窗格"></a>交换窗格</h4><p>当前窗格和上一个或下一个窗格交换位置。</p>
-<figure class="highlight shell"><table><tr><td class="code"><pre><span class="line"><span class="meta prompt_">$ </span><span class="language-bash">tmux swap-pane -U</span></span><br><span class="line"><span class="meta prompt_">$ </span><span class="language-bash">tmux swap-pane -D</span></span><br></pre></td></tr></table></figure>
-<h4 id="窗格快捷键"><a href="#窗格快捷键" class="headerlink" title="窗格快捷键"></a>窗格快捷键</h4><ul>
-<li><strong><code>Ctrl+b &quot;</code>：上下划分窗格</strong></li>
-<li><strong><code>Ctrl+b %</code>：左右划分窗格</strong></li>
-<li><strong><code>Ctrl+b &lt;arrow key&gt;</code>：使用方向键切换窗格</strong></li>
-<li><code>Ctrl+b ;</code>：光标切换到上一个窗格</li>
-<li><code>Ctrl+b o</code>：光标切换到下一个窗格</li>
-<li><code>Ctrl+b &#123;</code>：当前窗格和上一个窗格交换位置</li>
-<li><code>Ctrl+b &#125;</code>：当前窗格和下一个窗格交换位置</li>
-<li><strong><code>Ctrl+b x</code>：关闭当前窗格</strong></li>
-<li><code>Ctrl+b !</code>：将当前窗格拆分为一个独立窗口</li>
-<li><code>Ctrl+b z</code>：当前窗格全屏显示，再使用一次会变回原来大小，状态栏会有大写的 Z 标识</li>
-<li><code>Ctrl+b q</code>：显示窗格编号</li>
-</ul>
-<h3 id="其他命令"><a href="#其他命令" class="headerlink" title="其他命令"></a>其他命令</h3><h4 id="进入翻页模式"><a href="#进入翻页模式" class="headerlink" title="进入翻页模式"></a>进入翻页模式</h4><ul>
-<li><strong><code>Ctrl+b [</code>：进入翻页模式</strong></li>
-<li><code>q</code>：退出翻页模式</li>
-</ul>
-<h4 id="列出所有快捷键，及其对应的-Tmux-命令"><a href="#列出所有快捷键，及其对应的-Tmux-命令" class="headerlink" title="列出所有快捷键，及其对应的 Tmux 命令"></a>列出所有快捷键，及其对应的 Tmux 命令</h4><figure class="highlight shell"><table><tr><td class="code"><pre><span class="line"><span class="meta prompt_">$ </span><span class="language-bash">tmux list-keys</span></span><br></pre></td></tr></table></figure>
-<h4 id="列出所有-Tmux-命令及其参数"><a href="#列出所有-Tmux-命令及其参数" class="headerlink" title="列出所有 Tmux 命令及其参数"></a>列出所有 Tmux 命令及其参数</h4><figure class="highlight shell"><table><tr><td class="code"><pre><span class="line"><span class="meta prompt_">$ </span><span class="language-bash">tmux list-commands</span></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>
 
-<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://www.ruanyifeng.com/blog/2019/10/tmux.html">Tmux 使用教程</a><br><a href="https://blog.csdn.net/weixin_51311218/article/details/122172339">Tmux 学习</a></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>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>tmux</tag>
+        <tag>proxy</tag>
+        <tag>docker</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>
-    <content><![CDATA[<h2 id="使用-SSH-连接-Github"><a href="#使用-SSH-连接-Github" class="headerlink" title="使用 SSH 连接 Github"></a>使用 SSH 连接 Github</h2><h3 id="检查现有-SSH-密钥"><a href="#检查现有-SSH-密钥" class="headerlink" title="检查现有 SSH 密钥"></a>检查现有 SSH 密钥</h3><p>打开终端，输入 <code>ls -al ~/.ssh</code> 以查看是否存在现有的 SSH 密钥。</p>
-<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">ls</span> -al ~/.ssh</span></span><br><span class="line">total 16</span><br><span class="line">drwx------ 2 wrmao wrmao 4096 Jun 28 20:19 .</span><br><span class="line">drwxr-xr-x 6 wrmao wrmao 4096 Jun 28 20:13 ..</span><br><span class="line">-rw------- 1 wrmao wrmao  106 Jun 28 20:07 authorized_keys</span><br><span class="line">-rw-r--r-- 1 wrmao wrmao  444 Jun 28 20:19 known_hosts</span><br></pre></td></tr></table></figure>
-<p>检查目录列表以查看是否已经有 SSH 公钥。 默认情况下，GitHub 的一个支持的公钥的文件名是以下之一。</p>
-<ul>
-<li>id_rsa.pub</li>
-<li>id_ecdsa.pub</li>
-<li>id_ed25519.pub</li>
-</ul>
-<h3 id="生成-SSH-密钥"><a href="#生成-SSH-密钥" class="headerlink" title="生成 SSH 密钥"></a>生成 SSH 密钥</h3><p>如果没有密钥，就需要生成新的 SSH 密钥；如果已有，跳到上传已有密钥环节。<br>打开终端，粘贴下面的文本（替换为你的 GitHub 电子邮件地址），这将以提供的电子邮件地址为标签创建新 SSH 密钥。<br>一直 yes 确定选择默认即可。</p>
-<figure class="highlight shell"><table><tr><td class="code"><pre><span class="line"><span class="meta prompt_">$ </span><span class="language-bash">ssh-keygen -t ed25519 -C <span class="string">&quot;your_email@example.com&quot;</span></span></span><br><span class="line">Generating public/private ed25519 key pair.</span><br><span class="line">Enter file in which to save the key (/home/your-user/.ssh/id_ed25519):</span><br></pre></td></tr></table></figure>
+    <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>最近在本地测试 Kubesphere 和 Minikube，使用 Ubuntu server 20.04 搭建了多个虚拟机，磁盘空间紧张。注意到安装后，磁盘空间仅占据分配的一半左右。<br>如果 Ubuntu server 20.04 安装时使用默认的 lvm 选项，就会出现这种情况。</p>
+<p>分配了 40GB 磁盘空间，可用仅 19GB。</p>
+<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>
 
-<h3 id="上传-SSH-密钥"><a href="#上传-SSH-密钥" class="headerlink" title="上传 SSH 密钥"></a>上传 SSH 密钥</h3><p>将 SSH 公钥复制到剪贴板，在 Github 上的 <code>Settings</code> - <code>Access</code> - <code>SSH and GPG keys</code> - <code>New SSH key</code>，粘贴即可。</p>
-<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">cat</span> ~/.ssh/id_ed25519.pub</span></span><br></pre></td></tr></table></figure>
+<p>查看发现 Free  PE &#x2F; Size 还有 19GB。</p>
+<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>
 
-<h3 id="配置-Git"><a href="#配置-Git" class="headerlink" title="配置 Git"></a>配置 Git</h3><figure class="highlight shell"><table><tr><td class="code"><pre><span class="line"><span class="meta prompt_">$ </span><span class="language-bash">git config --global user.name <span class="string">&quot;moralok&quot;</span></span></span><br><span class="line"><span class="meta prompt_">$ </span><span class="language-bash">git config --global user.email <span class="string">&quot;wrmao.public@outlook.com&quot;</span></span></span><br></pre></td></tr></table></figure>
+<p>重新分配空间。</p>
+<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><span class="line"><span class="meta prompt_"></span></span><br><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>
 
+<p>再次查看。</p>
+<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>
 
-<h2 id="SSH-的原理"><a href="#SSH-的原理" class="headerlink" title="SSH 的原理"></a>SSH 的原理</h2><h3 id="关于-SSH"><a href="#关于-SSH" class="headerlink" title="关于 SSH"></a>关于 SSH</h3><p>使用 SSH 协议可以连接远程服务器和服务并向它们验证，而无需在每次访问时都提供用户名和密码，Github 还可以使用 SSH 密钥对提交进行签名。</p>
-<h3 id="公钥和私钥"><a href="#公钥和私钥" class="headerlink" title="公钥和私钥"></a>公钥和私钥</h3><p>SSH 的使用（非对称加密）需要生成公钥 public key 和私钥 private key。常用的算法有 <code>rsa</code>、<code>ecdsa</code> 和 <code>ed25519</code>，相对应的公钥默认文件名即id_XXX.pub。<code>ed25519</code> 的安全性介于 <code>rsa 2048</code> 和 <code>rsa 4096</code> 之间，但性能却提升数十倍。<br>在生成密钥时，会要求你 <code>Enter passphrase (empty for no passphrase):</code>，可以输入一个口令保护私钥的使用。不为空的情况下，正常使用是需要输入这个口令的，很多人认为麻烦，因此留空。<br>公钥的权限必须是 644，私钥的权限必须是 600，否则 SSH 认为其不可靠。<br>私钥是要安全保管在客户端不能泄露的，公钥则要提供给远程服务器或服务。服务端的 <code>~/.ssh/authorized_keys</code> 里面存储着可以登录的客户端的公钥。我们将公钥粘贴到 Github 的过程就是对应于此。</p>
-<figure class="highlight shell"><table><tr><td class="code"><pre><span class="line"><span class="meta prompt_">$ </span><span class="language-bash">ssh-keygen -t rsa -b 4096 -f my_id -C <span class="string">&quot;email@example.com&quot;</span></span></span><br></pre></td></tr></table></figure>
-<ul>
-<li><code>-t</code> 表示算法，如 <code>rsa</code>。</li>
-<li><code>-b</code> 表示 <code>rsa</code> 密钥长度，默认 2048 bit，<code>ed25519</code> 不需要指定。</li>
-<li><code>-f</code> 表示文件名。</li>
-<li><code>-C</code> 表示在公钥文件中添加注释，可修改</li>
-</ul>
-<h3 id="SSH-公钥登录过程"><a href="#SSH-公钥登录过程" class="headerlink" title="SSH 公钥登录过程"></a>SSH 公钥登录过程</h3><ol>
-<li>Client 将自己的公钥存放到服务端，追加到 authorized_keys 文件。</li>
-<li>Server 收到 Client 的连接请求后，会在 authorized_keys 文件中匹配到 Client 传过来的公钥，并生成随机数 R，用公钥对随机数加密得到 pubKey(R)。</li>
-<li>Client 收到后通过私钥解密得到随机数 R，然后对随机数 R 和本次会话的 sessionKey 使用 MD5 生成摘要 Digest1，发送给服务端。</li>
-<li>Server 会对随机数 R 和会话的 sessionKey 同样使用 MD5 生成摘要 Digest2，对比相同即完成认证过程。</li>
-</ol>
-<h3 id="避免中间人攻击"><a href="#避免中间人攻击" class="headerlink" title="避免中间人攻击"></a>避免中间人攻击</h3><p>SSH 通过口令确认避免中间人攻击，如果用户第一次登录 Server，系统会提示：</p>
-<figure class="highlight shell"><table><tr><td class="code"><pre><span class="line"><span class="meta prompt_">$ </span><span class="language-bash">ssh -T git@github.com</span></span><br><span class="line">The authenticity of host &#x27;github.com (20.205.243.166)&#x27; can&#x27;t be established.</span><br><span class="line">ECDSA key fingerprint is SHA256:p2QAMXNIC1TJYWeIOttrVc98/R1BUFWu3/LiyKgUfQM.</span><br><span class="line">Are you sure you want to continue connecting (yes/no/[fingerprint])? yes</span><br><span class="line">Warning: Permanently added &#x27;github.com,20.205.243.166&#x27; (ECDSA) to the list of known hosts.</span><br><span class="line">Hi $&#123;username&#125;! You&#x27;ve successfully authenticated, but GitHub does not provide shell access.</span><br></pre></td></tr></table></figure>
-<p>Server 需要在其网站上公示其公钥的指纹，Github 的公钥指纹<a href="https://docs.github.com/zh/authentication/keeping-your-account-and-data-secure/githubs-ssh-key-fingerprints">在这里</a>。<br>确认匹配后，客户端会在 <code>~/.ssh/known_hosts</code> 中记录，下次登录不再警告。</p>
-<h2 id="使用-SSH-免密登录服务器"><a href="#使用-SSH-免密登录服务器" class="headerlink" title="使用 SSH 免密登录服务器"></a>使用 SSH 免密登录服务器</h2><p>使用现成的密钥，将 <code>~/.ssh/id_ed25519.pub</code> 的内容追加到自己服务端的 <code>~/.ssh/authorized_keys</code> 中，使用 <code>ssh user@host</code> 成功免密登录。<br>这样一来，使用 VScode 远程连接服务器和使用 Remote Explorer 打开文件夹时，不用每次都输入密码了。</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://docs.github.com/zh/authentication/connecting-to-github-with-ssh/about-ssh">使用 SSH 进行连接 Github</a><br><a href="https://blog.csdn.net/u012408797/article/details/116196831">Git 多台电脑共用SSH Key</a><br><a href="https://blog.csdn.net/neo949332116/article/details/102926051">SSH协议登录过程详解</a><br><a href="https://docs.github.com/zh/authentication/keeping-your-account-and-data-secure/githubs-ssh-key-fingerprints">GitHub 的 SSH 密钥指纹</a><br><a href="https://zhuanlan.zhihu.com/p/110413836">使用 Ed25519 算法生成你的 SSH 密钥</a></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.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>ssh</tag>
+        <tag>ubuntu</tag>
       </tags>
   </entry>
   <entry>
@@ -861,149 +751,113 @@
       </tags>
   </entry>
   <entry>
-    <title>Spring Bean 加载过程</title>
-    <url>/2023/08/10/how-does-Spring-load-beans/</url>
-    <content><![CDATA[<h2 id="Spring-Bean-生命周期"><a href="#Spring-Bean-生命周期" class="headerlink" title="Spring Bean 生命周期"></a>Spring Bean 生命周期</h2><img src="/2023/08/10/how-does-Spring-load-beans/Pasted%20image%2020231118213120.png" class="" title="Spring Bean 生命周期">
-
-<h2 id="获取-Bean"><a href="#获取-Bean" class="headerlink" title="获取 Bean"></a>获取 Bean</h2><p>获取指定 Bean 的入口方法是 getBean，在 Spring 上下文刷新过程中，就依次调用 <code>AbstractBeanFactory#getBean(java.lang.String)</code> 方法获取 <code>non-lazy-init</code> 的 Bean。</p>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> Object <span class="title function_">getBean</span><span class="params">(String name)</span> <span class="keyword">throws</span> BeansException &#123;</span><br><span class="line">    <span class="comment">// 具体工作由 doGetBean 完成</span></span><br><span class="line">    <span class="keyword">return</span> doGetBean(name, <span class="literal">null</span>, <span class="literal">null</span>, <span class="literal">false</span>);</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
-
-<h3 id="deGetBean"><a href="#deGetBean" class="headerlink" title="deGetBean"></a>deGetBean</h3><p>作为公共处理逻辑，由 AbstractBeanFactory 自己实现。</p>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">protected</span> &lt;T&gt; T <span class="title function_">doGetBean</span><span class="params">(</span></span><br><span class="line"><span class="params">    <span class="keyword">final</span> String name, <span class="keyword">final</span> Class&lt;T&gt; requiredType, <span class="keyword">final</span> Object[] args, <span class="type">boolean</span> typeCheckOnly)</span> </span><br><span class="line">    <span class="keyword">throws</span> BeansException &#123;</span><br><span class="line">    <span class="comment">// 转换名称：去除 FactoryBean 的前缀 &amp;，将别名转换为规范名称</span></span><br><span class="line">    <span class="keyword">final</span> <span class="type">String</span> <span class="variable">beanName</span> <span class="operator">=</span> transformedBeanName(name);</span><br><span class="line">    Object bean;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 检查单例缓存中是否已存在</span></span><br><span class="line">    <span class="type">Object</span> <span class="variable">sharedInstance</span> <span class="operator">=</span> getSingleton(beanName);</span><br><span class="line">    <span class="keyword">if</span> (sharedInstance != <span class="literal">null</span> &amp;&amp; args == <span class="literal">null</span>) &#123;</span><br><span class="line">        <span class="comment">// ...</span></span><br><span class="line">        <span class="comment">// 如果已存在，直接返回该实例或者使用该实例（FactoryBean）创建并返回对象</span></span><br><span class="line">        bean = getObjectForBeanInstance(sharedInstance, name, beanName, <span class="literal">null</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">// 如果当前 Bean 是一个正在创建中的 prototype 类型，表明可能发生循环引用</span></span><br><span class="line">        <span class="comment">// 注意：Spring 并未解决 prototype 类型的循环引用问题，要抛出异常</span></span><br><span class="line">        <span class="keyword">if</span> (isPrototypeCurrentlyInCreation(beanName)) &#123;</span><br><span class="line">            <span class="keyword">throw</span> <span class="keyword">new</span> <span class="title class_">BeanCurrentlyInCreationException</span>(beanName);</span><br><span class="line">        &#125;</span><br><span class="line">        </span><br><span class="line">        <span class="comment">// 如果当前 beanFactory 没有 bean 定义，去 parent beanFactory 中查找</span></span><br><span class="line">        <span class="type">BeanFactory</span> <span class="variable">parentBeanFactory</span> <span class="operator">=</span> getParentBeanFactory();</span><br><span class="line">        <span class="keyword">if</span> (parentBeanFactory != <span class="literal">null</span> &amp;&amp; !containsBeanDefinition(beanName)) &#123;</span><br><span class="line">            <span class="type">String</span> <span class="variable">nameToLookup</span> <span class="operator">=</span> originalBeanName(name);</span><br><span class="line">            <span class="keyword">if</span> (args != <span class="literal">null</span>) &#123;</span><br><span class="line">                <span class="keyword">return</span> (T) parentBeanFactory.getBean(nameToLookup, args);</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> parentBeanFactory.getBean(nameToLookup, requiredType);</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> (!typeCheckOnly) &#123;</span><br><span class="line">            <span class="comment">// 标记为至少创建过一次</span></span><br><span class="line">            markBeanAsCreated(beanName);</span><br><span class="line">        &#125;</span><br><span class="line">        </span><br><span class="line">        <span class="keyword">try</span> &#123;</span><br><span class="line">            <span class="keyword">final</span> <span class="type">RootBeanDefinition</span> <span class="variable">mbd</span> <span class="operator">=</span> getMergedLocalBeanDefinition(beanName);</span><br><span class="line">            checkMergedBeanDefinition(mbd, beanName, args);</span><br><span class="line"></span><br><span class="line">            <span class="comment">// 确保 bean 依赖的 bean（构造器参数） 都已实例化</span></span><br><span class="line">            String[] dependsOn = mbd.getDependsOn();</span><br><span class="line">            <span class="keyword">if</span> (dependsOn != <span class="literal">null</span>) &#123;</span><br><span class="line">                <span class="keyword">for</span> (String dep : dependsOn) &#123;</span><br><span class="line">                    <span class="keyword">if</span> (isDependent(beanName, dep)) &#123;</span><br><span class="line">                        <span class="comment">// 注意：Spring 并未解决构造器方法中的循环引用问题，要抛异常</span></span><br><span class="line">                    &#125;</span><br><span class="line">                    <span class="comment">// 注册依赖关系，确保先销毁被依赖的 bean</span></span><br><span class="line">                    registerDependentBean(dep, beanName);</span><br><span class="line">                    <span class="comment">// 递归，获取依赖的 bean</span></span><br><span class="line">                    getBean(dep);</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">if</span> (mbd.isSingleton()) &#123;</span><br><span class="line">            <span class="comment">// 如果是单例类型（绝大多数都是此类型）</span></span><br><span class="line">            <span class="comment">// 再次从缓存中获取，如果仍不存在，则使用传入的 ObjectFactory 创建</span></span><br><span class="line">            sharedInstance = getSingleton(beanName, <span class="keyword">new</span> <span class="title class_">ObjectFactory</span>&lt;Object&gt;(</span><br><span class="line">                &#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_">getObject</span><span class="params">()</span> <span class="keyword">throws</span> BeansException &#123;</span><br><span class="line">                        <span class="keyword">try</span> &#123;</span><br><span class="line">                            <span class="comment">// 创建 bean</span></span><br><span class="line">                            <span class="keyword">return</span> createBean(beanName, mbd, args);</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">// 由于可能已经提前暴露，需要显示地销毁                </span></span><br><span class="line">                            destroySingleton(beanName);</span><br><span class="line">                            <span class="keyword">throw</span> ex;</span><br><span class="line">                        &#125;</span><br><span class="line">                    &#125;</span><br><span class="line">                &#125;);</span><br><span class="line">            bean = getObjectForBeanInstance(sharedInstance, name, beanName, mbd);</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="keyword">else</span> <span class="keyword">if</span> (mbd.isPrototype()) &#123;</span><br><span class="line">            <span class="comment">// 如果是原型类型，每次都新创建一个</span></span><br><span class="line">            <span class="comment">// ...</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">// 如果是其他 scope 类型</span></span><br><span class="line">            <span class="comment">// ...</span></span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="keyword">catch</span> (BeansException ex) &#123;</span><br><span class="line">        cleanupAfterBeanCreationFailure(beanName);</span><br><span class="line">        <span class="keyword">throw</span> ex;</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
-
-<h3 id="getSingleton"><a href="#getSingleton" class="headerlink" title="getSingleton"></a>getSingleton</h3><figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> Object <span class="title function_">getSingleton</span><span class="params">(String beanName, ObjectFactory&lt;?&gt; singletonFactory)</span> &#123;</span><br><span class="line">    <span class="comment">// 加锁</span></span><br><span class="line">    <span class="keyword">synchronized</span> (<span class="built_in">this</span>.singletonObjects) &#123;</span><br><span class="line">        <span class="comment">// 再次从缓存中获取（和调用前从缓存中获取构成双重校验）</span></span><br><span class="line">        <span class="type">Object</span> <span class="variable">singletonObject</span> <span class="operator">=</span> <span class="built_in">this</span>.singletonObjects.get(beanName);</span><br><span class="line">        <span class="keyword">if</span> (singletonObject == <span class="literal">null</span>) &#123;</span><br><span class="line">            <span class="keyword">if</span> (<span class="built_in">this</span>.singletonsCurrentlyInDestruction) &#123;</span><br><span class="line">                <span class="comment">// 如果正在销毁单例，则抛异常</span></span><br><span class="line">                <span class="comment">// 注意：不要在销毁方法中调用获取 bean 方法</span></span><br><span class="line">            &#125;</span><br><span class="line">            <span class="comment">// 创建前，先注册到正在创建中的集合</span></span><br><span class="line">            <span class="comment">// 在出现循环引用时，第二次进入 doGetBean，用此作为判断标志</span></span><br><span class="line">            beforeSingletonCreation(beanName);</span><br><span class="line">            <span class="type">boolean</span> <span class="variable">newSingleton</span> <span class="operator">=</span> <span class="literal">false</span>;</span><br><span class="line">            <span class="comment">// ...</span></span><br><span class="line">            <span class="keyword">try</span> &#123;</span><br><span class="line">                <span class="comment">// 使用传入的单例工厂创建对象</span></span><br><span class="line">                singletonObject = singletonFactory.getObject();</span><br><span class="line">                newSingleton = <span class="literal">true</span>;</span><br><span class="line">            &#125;</span><br><span class="line">            <span class="keyword">catch</span> (IllegalStateException ex) &#123;</span><br><span class="line">                <span class="comment">// 如果异常的出现是因为 bean 被创建了，就忽略异常，否则抛出异常</span></span><br><span class="line">                singletonObject = <span class="built_in">this</span>.singletonObjects.get(beanName);</span><br><span class="line">                <span class="keyword">if</span> (singletonObject == <span class="literal">null</span>) &#123;</span><br><span class="line">                    <span class="keyword">throw</span> ex;</span><br><span class="line">                &#125;</span><br><span class="line">            &#125;</span><br><span class="line">            <span class="keyword">catch</span> (BeanCreationException ex) &#123;</span><br><span class="line">                <span class="comment">// ...</span></span><br><span class="line">            &#125;</span><br><span class="line">            <span class="keyword">finally</span> &#123;</span><br><span class="line">                <span class="comment">// ...</span></span><br><span class="line">                <span class="comment">// 创建后，从正在创建中集合移除</span></span><br><span class="line">                afterSingletonCreation(beanName);</span><br><span class="line">            &#125;</span><br><span class="line">            <span class="keyword">if</span> (newSingleton) &#123;</span><br><span class="line">                <span class="comment">// 添加单例到缓存</span></span><br><span class="line">                addSingleton(beanName, singletonObject);</span><br><span class="line">            &#125;</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="keyword">return</span> (singletonObject != NULL_OBJECT ? singletonObject : <span class="literal">null</span>);</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
-
-<h2 id="创建-Bean"><a href="#创建-Bean" class="headerlink" title="创建 Bean"></a>创建 Bean</h2><p>createBean 是创建 Bean 的入口方法，由 AbstractBeanFactory 定义，由 AbstractAutowireCapableBeanFactory 实现。</p>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">protected</span> Object <span class="title function_">createBean</span><span class="params">(String beanName, RootBeanDefinition mbd, Object[] args)</span> <span class="keyword">throws</span> BeanCreationException &#123;</span><br><span class="line">    <span class="comment">// ...</span></span><br><span class="line">    <span class="keyword">try</span> &#123;</span><br><span class="line">        <span class="comment">// 给 Bean 后置处理器一个返回代理的机会</span></span><br><span class="line">        <span class="type">Object</span> <span class="variable">bean</span> <span class="operator">=</span> resolveBeforeInstantiation(beanName, mbdToUse);</span><br><span class="line">        <span class="keyword">if</span> (bean != <span class="literal">null</span>) &#123;</span><br><span class="line">            <span class="keyword">return</span> bean;</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">    <span class="comment">// 常规的创建 Bean</span></span><br><span class="line">    <span class="type">Object</span> <span class="variable">beanInstance</span> <span class="operator">=</span> doCreateBean(beanName, mbdToUse, args);</span><br><span class="line">    <span class="keyword">return</span> beanInstance;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
-
-<h3 id="doCreateBean"><a href="#doCreateBean" class="headerlink" title="doCreateBean"></a>doCreateBean</h3><p>常规的创建 Bean 的具体工作是由 doCreateBean 完成的。</p>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">protected</span> Object <span class="title function_">doCreateBean</span><span class="params">(<span class="keyword">final</span> String beanName, <span class="keyword">final</span> RootBeanDefinition mbd, <span class="keyword">final</span> Object[] args)</span> <span class="keyword">throws</span> BeanCreationException &#123;</span><br><span class="line">    <span class="type">BeanWrapper</span> <span class="variable">instanceWrapper</span> <span class="operator">=</span> <span class="literal">null</span>;</span><br><span class="line">    <span class="keyword">if</span> (mbd.isSingleton()) &#123;</span><br><span class="line">        instanceWrapper = <span class="built_in">this</span>.factoryBeanInstanceCache.remove(beanName);</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="keyword">if</span> (instanceWrapper == <span class="literal">null</span>) &#123;</span><br><span class="line">        <span class="comment">// 使用相应的策略创建 bean 实例，例如通过工厂方法或者有参、无参构造器方法</span></span><br><span class="line">        instanceWrapper = createBeanInstance(beanName, mbd, args);</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="keyword">final</span> <span class="type">Object</span> <span class="variable">bean</span> <span class="operator">=</span> (instanceWrapper != <span class="literal">null</span> ? instanceWrapper.getWrappedInstance() : <span class="literal">null</span>);</span><br><span class="line">    Class&lt;?&gt; beanType = (instanceWrapper != <span class="literal">null</span> ? instanceWrapper.getWrappedClass() : <span class="literal">null</span>);</span><br><span class="line">    mbd.resolvedTargetType = beanType;</span><br><span class="line">    </span><br><span class="line">    <span class="comment">// ...</span></span><br><span class="line"></span><br><span class="line">    <span class="comment">// 使用 ObjectFactory 封装实例并缓存，以解决循环引用问题</span></span><br><span class="line">    <span class="type">boolean</span> <span class="variable">earlySingletonExposure</span> <span class="operator">=</span> (mbd.isSingleton() </span><br><span class="line">        &amp;&amp; <span class="built_in">this</span>.allowCircularReferences </span><br><span class="line">        &amp;&amp; isSingletonCurrentlyInCreation(beanName));</span><br><span class="line">    <span class="keyword">if</span> (earlySingletonExposure) &#123;</span><br><span class="line">        addSingletonFactory(beanName, <span class="keyword">new</span> <span class="title class_">ObjectFactory</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_">getObject</span><span class="params">()</span> <span class="keyword">throws</span> BeansException &#123;</span><br><span class="line">                <span class="keyword">return</span> getEarlyBeanReference(beanName, mbd, bean);</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="type">Object</span> <span class="variable">exposedObject</span> <span class="operator">=</span> bean;</span><br><span class="line">    <span class="keyword">try</span> &#123;</span><br><span class="line">        <span class="comment">// 填充属性（包括解析依赖的 bean）</span></span><br><span class="line">        populateBean(beanName, mbd, instanceWrapper);</span><br><span class="line">        <span class="keyword">if</span> (exposedObject != <span class="literal">null</span>) &#123;</span><br><span class="line">            <span class="comment">// 初始化 bean</span></span><br><span class="line">            exposedObject = initializeBean(beanName, exposedObject, mbd);</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"></span><br><span class="line">    <span class="comment">// 如有需要，将 bean 注册为一次性的，以供 beanFactory 在关闭时调用销毁方法</span></span><br><span class="line">    <span class="keyword">try</span> &#123;</span><br><span class="line">        registerDisposableBeanIfNecessary(beanName, bean, mbd);</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="comment">// ...</span></span><br><span class="line"></span><br><span class="line">    <span class="keyword">return</span> exposedObject;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
-
-<h4 id="createBeanInstance"><a href="#createBeanInstance" class="headerlink" title="createBeanInstance"></a>createBeanInstance</h4><p>创建 Bean 实例，并使用 BeanWrapper 封装。实例化的方式：</p>
-<ol>
-<li>工厂方法</li>
-<li>构造器方法<ol>
-<li>有参</li>
-<li>无参</li>
-</ol>
-</li>
-</ol>
-<h4 id="populateBean"><a href="#populateBean" class="headerlink" title="populateBean"></a>populateBean</h4><p>为创建出的实例填充属性，包括解析当前 bean 所依赖的 bean。</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_">populateBean</span><span class="params">(String beanName, RootBeanDefinition mbd, BeanWrapper bw)</span> &#123;</span><br><span class="line">    <span class="type">PropertyValues</span> <span class="variable">pvs</span> <span class="operator">=</span> mbd.getPropertyValues();</span><br><span class="line">    <span class="comment">// ...</span></span><br><span class="line">    </span><br><span class="line">    <span class="comment">// 给 InstantiationAwareBeanPostProcessors 一个机会，</span></span><br><span class="line">    <span class="comment">// 在设置 bean 属性前修改 bean 状态，可用于自定义的字段注入</span></span><br><span class="line">    <span class="type">boolean</span> <span class="variable">continueWithPropertyPopulation</span> <span class="operator">=</span> <span class="literal">true</span>;</span><br><span class="line">    <span class="keyword">if</span> (!mbd.isSynthetic() &amp;&amp; hasInstantiationAwareBeanPostProcessors()) &#123;</span><br><span class="line">        <span class="keyword">for</span> (BeanPostProcessor bp : getBeanPostProcessors()) &#123;</span><br><span class="line">            <span class="keyword">if</span> (bp <span class="keyword">instanceof</span> InstantiationAwareBeanPostProcessor) &#123;</span><br><span class="line">                <span class="type">InstantiationAwareBeanPostProcessor</span> <span class="variable">ibp</span> <span class="operator">=</span> (InstantiationAwareBeanPostProcessor) bp;</span><br><span class="line">                <span class="keyword">if</span> (!ibp.postProcessAfterInstantiation(bw.getWrappedInstance(), beanName)) &#123;</span><br><span class="line">                    continueWithPropertyPopulation = <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">    &#125;</span><br><span class="line">    </span><br><span class="line">    <span class="comment">// 是否继续填充属性的流程</span></span><br><span class="line">    <span class="keyword">if</span> (!continueWithPropertyPopulation) &#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="keyword">if</span> (mbd.getResolvedAutowireMode() == RootBeanDefinition.AUTOWIRE_BY_NAME</span><br><span class="line">        || mbd.getResolvedAutowireMode() == RootBeanDefinition.AUTOWIRE_BY_TYPE) &#123;</span><br><span class="line">        <span class="type">MutablePropertyValues</span> <span class="variable">newPvs</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">MutablePropertyValues</span>(pvs);</span><br><span class="line">        <span class="comment">// 根据名称注入</span></span><br><span class="line">        <span class="keyword">if</span> (mbd.getResolvedAutowireMode() == RootBeanDefinition.AUTOWIRE_BY_NAME) &#123;</span><br><span class="line">            autowireByName(beanName, mbd, bw, newPvs);</span><br><span class="line">        &#125;</span><br><span class="line">        </span><br><span class="line">        <span class="comment">// 根据类型注入</span></span><br><span class="line">        <span class="keyword">if</span> (mbd.getResolvedAutowireMode() == RootBeanDefinition.AUTOWIRE_BY_TYPE) &#123;</span><br><span class="line">            autowireByType(beanName, mbd, bw, newPvs);</span><br><span class="line">        &#125;</span><br><span class="line">        pvs = newPvs;</span><br><span class="line">    &#125;</span><br><span class="line">    </span><br><span class="line">    <span class="comment">// 是否存在 InstantiationAwareBeanPostProcessors</span></span><br><span class="line">    <span class="type">boolean</span> <span class="variable">hasInstAwareBpps</span> <span class="operator">=</span> hasInstantiationAwareBeanPostProcessors();</span><br><span class="line">    <span class="comment">// 是否需要检查依赖</span></span><br><span class="line">    <span class="type">boolean</span> <span class="variable">needsDepCheck</span> <span class="operator">=</span> (mbd.getDependencyCheck() != RootBeanDefinition.DEPENDENCY_CHECK_NONE);</span><br><span class="line">    </span><br><span class="line">    <span class="keyword">if</span> (hasInstAwareBpps || needsDepCheck) &#123;</span><br><span class="line">        PropertyDescriptor[] filteredPds = filterPropertyDescriptorsForDependencyCheck(bw, mbd.allowCaching);</span><br><span class="line">        <span class="keyword">if</span> (hasInstAwareBpps) &#123;</span><br><span class="line">            <span class="comment">// 后置处理 PropertyValues</span></span><br><span class="line">            <span class="keyword">for</span> (BeanPostProcessor bp : getBeanPostProcessors()) &#123;</span><br><span class="line">                <span class="keyword">if</span> (bp <span class="keyword">instanceof</span> InstantiationAwareBeanPostProcessor) &#123;</span><br><span class="line">                    <span class="type">InstantiationAwareBeanPostProcessor</span> <span class="variable">ibp</span> <span class="operator">=</span> (InstantiationAwareBeanPostProcessor) bp;</span><br><span class="line">                    pvs = ibp.postProcessPropertyValues(pvs, filteredPds, bw.getWrappedInstance(), beanName);</span><br><span class="line">                    <span class="keyword">if</span> (pvs == <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">                &#125;   </span><br><span class="line">            &#125;</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="keyword">if</span> (needsDepCheck) &#123;</span><br><span class="line">            checkDependencies(beanName, mbd, filteredPds, pvs);</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="comment">// 将属性应用到 bean 上（常规情况下，前面的处理都用不上）</span></span><br><span class="line">    applyPropertyValues(beanName, mbd, bw, pvs);</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
-
-<h4 id="initializeBean"><a href="#initializeBean" class="headerlink" title="initializeBean"></a>initializeBean</h4><p>在填充完属性后，实例就可以进行初始化工作：</p>
-<ol>
-<li>invokeAwareMethods，让 Bean 通过 xxxAware 接口感知一些信息</li>
-<li>调用 BeanPostProcessor 的 postProcessBeforeInitialization 方法</li>
-<li>invokeInitMethods，调用初始化方法</li>
-<li>调用 BeanPostProcessor 的 postProcessAfterInitialization 方法</li>
-</ol>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">protected</span> Object <span class="title function_">initializeBean</span><span class="params">(<span class="keyword">final</span> String beanName, <span class="keyword">final</span> Object bean, RootBeanDefinition mbd)</span> &#123;</span><br><span class="line">    <span class="comment">// 处理 Aware 接口的相应方法</span></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">                invokeAwareMethods(beanName, bean);</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">        invokeAwareMethods(beanName, bean);</span><br><span class="line">    &#125;</span><br><span class="line">    </span><br><span class="line">    <span class="comment">// 应用 BeanPostProcessor 的 postProcessBeforeInitialization 方法</span></span><br><span class="line">    <span class="type">Object</span> <span class="variable">wrappedBean</span> <span class="operator">=</span> bean;</span><br><span class="line">    <span class="keyword">if</span> (mbd == <span class="literal">null</span> || !mbd.isSynthetic()) &#123;</span><br><span class="line">        wrappedBean = applyBeanPostProcessorsBeforeInitialization(wrappedBean, beanName);</span><br><span class="line">    &#125;</span><br><span class="line">    </span><br><span class="line">    <span class="keyword">try</span> &#123;</span><br><span class="line">        <span class="comment">// 调用初始化方法</span></span><br><span class="line">        invokeInitMethods(beanName, wrappedBean, mbd);</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_">BeanCreationException</span>(</span><br><span class="line">            (mbd != <span class="literal">null</span> ? mbd.getResourceDescription() : <span class="literal">null</span>),</span><br><span class="line">            beanName, <span class="string">&quot;Invocation of init method failed&quot;</span>, ex);</span><br><span class="line">    &#125;</span><br><span class="line">    </span><br><span class="line">    <span class="keyword">if</span> (mbd == <span class="literal">null</span> || !mbd.isSynthetic()) &#123;</span><br><span class="line">        <span class="comment">// 应用 BeanPostProcessor 的 postProcessAfterInitialization 方法</span></span><br><span class="line">        wrappedBean = applyBeanPostProcessorsAfterInitialization(wrappedBean, beanName);</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="keyword">return</span> wrappedBean;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
-
-<h5 id="处理-Aware-接口的相应方法"><a href="#处理-Aware-接口的相应方法" class="headerlink" title="处理 Aware 接口的相应方法"></a>处理 Aware 接口的相应方法</h5><p>让 Bean 在初始化中，感知（获知）和自身相关的资源，如 beanName、beanClassLoader 或者 beanFactory。</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_">invokeAwareMethods</span><span class="params">(<span class="keyword">final</span> String beanName, <span class="keyword">final</span> Object bean)</span> &#123;</span><br><span class="line">    <span class="keyword">if</span> (bean <span class="keyword">instanceof</span> Aware) &#123;</span><br><span class="line">        <span class="keyword">if</span> (bean <span class="keyword">instanceof</span> BeanNameAware) &#123;</span><br><span class="line">            ((BeanNameAware) bean).setBeanName(beanName);</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="keyword">if</span> (bean <span class="keyword">instanceof</span> BeanClassLoaderAware) &#123;</span><br><span class="line">            ((BeanClassLoaderAware) bean).setBeanClassLoader(getBeanClassLoader());</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="keyword">if</span> (bean <span class="keyword">instanceof</span> BeanFactoryAware) &#123;</span><br><span class="line">            ((BeanFactoryAware) bean).setBeanFactory(AbstractAutowireCapableBeanFactory.<span class="built_in">this</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>
+    <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>
+    <content><![CDATA[<h2 id="使用-SSH-连接-Github"><a href="#使用-SSH-连接-Github" class="headerlink" title="使用 SSH 连接 Github"></a>使用 SSH 连接 Github</h2><h3 id="检查现有-SSH-密钥"><a href="#检查现有-SSH-密钥" class="headerlink" title="检查现有 SSH 密钥"></a>检查现有 SSH 密钥</h3><p>打开终端，输入 <code>ls -al ~/.ssh</code> 以查看是否存在现有的 SSH 密钥。</p>
+<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">ls</span> -al ~/.ssh</span></span><br><span class="line">total 16</span><br><span class="line">drwx------ 2 wrmao wrmao 4096 Jun 28 20:19 .</span><br><span class="line">drwxr-xr-x 6 wrmao wrmao 4096 Jun 28 20:13 ..</span><br><span class="line">-rw------- 1 wrmao wrmao  106 Jun 28 20:07 authorized_keys</span><br><span class="line">-rw-r--r-- 1 wrmao wrmao  444 Jun 28 20:19 known_hosts</span><br></pre></td></tr></table></figure>
+<p>检查目录列表以查看是否已经有 SSH 公钥。 默认情况下，GitHub 的一个支持的公钥的文件名是以下之一。</p>
+<ul>
+<li>id_rsa.pub</li>
+<li>id_ecdsa.pub</li>
+<li>id_ed25519.pub</li>
+</ul>
+<h3 id="生成-SSH-密钥"><a href="#生成-SSH-密钥" class="headerlink" title="生成 SSH 密钥"></a>生成 SSH 密钥</h3><p>如果没有密钥，就需要生成新的 SSH 密钥；如果已有，跳到上传已有密钥环节。<br>打开终端，粘贴下面的文本（替换为你的 GitHub 电子邮件地址），这将以提供的电子邮件地址为标签创建新 SSH 密钥。<br>一直 yes 确定选择默认即可。</p>
+<figure class="highlight shell"><table><tr><td class="code"><pre><span class="line"><span class="meta prompt_">$ </span><span class="language-bash">ssh-keygen -t ed25519 -C <span class="string">&quot;your_email@example.com&quot;</span></span></span><br><span class="line">Generating public/private ed25519 key pair.</span><br><span class="line">Enter file in which to save the key (/home/your-user/.ssh/id_ed25519):</span><br></pre></td></tr></table></figure>
 
-<h5 id="调用初始化方法"><a href="#调用初始化方法" class="headerlink" title="调用初始化方法"></a>调用初始化方法</h5><ol>
-<li>如果 bean 实现 InitializingBean 接口，调用 afterPropertiesSet 方法</li>
-<li>如果自定义 init 方法且满足调用条件，同样进行调用</li>
-</ol>
-<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_">invokeInitMethods</span><span class="params">(String beanName, <span class="keyword">final</span> Object bean, RootBeanDefinition mbd)</span> <span class="keyword">throws</span> Throwable &#123;</span><br><span class="line">    <span class="comment">// 是否实现 InitializingBean 接口，是的话调用 afterPropertiesSet 方法</span></span><br><span class="line">    <span class="comment">// 给 bean 一个感知属性已设置并做出反应的机会</span></span><br><span class="line">    <span class="type">boolean</span> <span class="variable">isInitializingBean</span> <span class="operator">=</span> (bean <span class="keyword">instanceof</span> InitializingBean);</span><br><span class="line">    <span class="keyword">if</span> (isInitializingBean</span><br><span class="line">        &amp;&amp; (mbd == <span class="literal">null</span> || !mbd.isExternallyManagedInitMethod(<span class="string">&quot;afterPropertiesSet&quot;</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">            <span class="keyword">try</span> &#123;</span><br><span class="line">                AccessController.doPrivileged(<span class="keyword">new</span> <span class="title class_">PrivilegedExceptionAction</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> <span class="keyword">throws</span> Exception &#123;</span><br><span class="line">                        ((InitializingBean) bean).afterPropertiesSet();</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">catch</span> (PrivilegedActionException pae) &#123;</span><br><span class="line">                <span class="keyword">throw</span> pae.getException();</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">            ((InitializingBean) bean).afterPropertiesSet();</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">// 如果存在自定义的 init 方法且方法名称不是 afterPropertiesSet，判断是否调用</span></span><br><span class="line">    <span class="keyword">if</span> (mbd != <span class="literal">null</span>) &#123;</span><br><span class="line">        <span class="type">String</span> <span class="variable">initMethodName</span> <span class="operator">=</span> mbd.getInitMethodName();</span><br><span class="line">        <span class="keyword">if</span> (initMethodName != <span class="literal">null</span></span><br><span class="line">            &amp;&amp; !(isInitializingBean &amp;&amp; <span class="string">&quot;afterPropertiesSet&quot;</span>.equals(initMethodName))</span><br><span class="line">            &amp;&amp; !mbd.isExternallyManagedInitMethod(initMethodName)) &#123;</span><br><span class="line">            invokeCustomInitMethod(beanName, bean, mbd);</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="上传-SSH-密钥"><a href="#上传-SSH-密钥" class="headerlink" title="上传 SSH 密钥"></a>上传 SSH 密钥</h3><p>将 SSH 公钥复制到剪贴板，在 Github 上的 <code>Settings</code> - <code>Access</code> - <code>SSH and GPG keys</code> - <code>New SSH key</code>，粘贴即可。</p>
+<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">cat</span> ~/.ssh/id_ed25519.pub</span></span><br></pre></td></tr></table></figure>
 
-<h5 id="BeanPostProcessor-处理"><a href="#BeanPostProcessor-处理" class="headerlink" title="BeanPostProcessor 处理"></a>BeanPostProcessor 处理</h5><p>在调用初始化方法前后，BeanPostProcessor 先后进行两次处理。其实和 BeanPostProcessor 相关的代码都非常相似：</p>
-<ol>
-<li>获取 Processor 列表</li>
-<li>判断 Processor 类型是否是当前需要的</li>
-<li>对 bean 进行处理</li>
-</ol>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> Object <span class="title function_">applyBeanPostProcessorsBeforeInitialization</span><span class="params">(Object existingBean, String beanName)</span> <span class="keyword">throws</span> BeansException &#123;</span><br><span class="line"></span><br><span class="line">    <span class="type">Object</span> <span class="variable">result</span> <span class="operator">=</span> existingBean;</span><br><span class="line">    <span class="keyword">for</span> (BeanPostProcessor beanProcessor : getBeanPostProcessors()) &#123;</span><br><span class="line">        result = beanProcessor.postProcessBeforeInitialization(result, beanName);</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">    <span class="keyword">return</span> result;</span><br><span class="line">&#125;</span><br><span class="line"></span><br><span class="line"><span class="keyword">public</span> Object <span class="title function_">applyBeanPostProcessorsAfterInitialization</span><span class="params">(Object existingBean, String beanName)</span> <span class="keyword">throws</span> BeansException &#123;</span><br><span class="line"></span><br><span class="line">    <span class="type">Object</span> <span class="variable">result</span> <span class="operator">=</span> existingBean;</span><br><span class="line">    <span class="keyword">for</span> (BeanPostProcessor beanProcessor : getBeanPostProcessors()) &#123;</span><br><span class="line">        result = beanProcessor.postProcessAfterInitialization(result, beanName);</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">    <span class="keyword">return</span> result;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+<h3 id="配置-Git"><a href="#配置-Git" class="headerlink" title="配置 Git"></a>配置 Git</h3><figure class="highlight shell"><table><tr><td class="code"><pre><span class="line"><span class="meta prompt_">$ </span><span class="language-bash">git config --global user.name <span class="string">&quot;moralok&quot;</span></span></span><br><span class="line"><span class="meta prompt_">$ </span><span class="language-bash">git config --global user.email <span class="string">&quot;wrmao.public@outlook.com&quot;</span></span></span><br></pre></td></tr></table></figure>
 
-<h4 id="再思-Bean-的初始化"><a href="#再思-Bean-的初始化" class="headerlink" title="再思 Bean 的初始化"></a>再思 Bean 的初始化</h4><p>以下代码片段一度让我困惑，从注释看，初始化 Bean 实例的工作包括了 populateBean 和 initializeBean，但是 initializeBean 方法的含义就是初始化 Bean。在 initializeBean 方法中，调用了 invokeInitMethods 方法，其含义仍然是调用初始化方法。<br>在更熟悉代码后，我有一种微妙的、个人性的体会，在 Spring 源码中，有时候视角的变化是很快的，痕迹是很小的。如果不加以理解和区分，很容易迷失在相似的描述中。以此处为例，“初始化 Bean 和 Bean 的初始化”扩展开来是 “Bean 工厂初始化一个 Bean 和 Bean 自身进行初始化”。</p>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="comment">// Initialize the bean instance.</span></span><br><span class="line"><span class="type">Object</span> <span class="variable">exposedObject</span> <span class="operator">=</span> bean;</span><br><span class="line"><span class="keyword">try</span> &#123;</span><br><span class="line">    populateBean(beanName, mbd, instanceWrapper);</span><br><span class="line">    <span class="keyword">if</span> (exposedObject != <span class="literal">null</span>) &#123;</span><br><span class="line">        exposedObject = initializeBean(beanName, exposedObject, mbd);</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
 
-<p>在注释这一行，视角是属于 BeanFactory（AbstractAutowireCapableBeanFactory）。从工厂的视角，面对一个刚刚创建出来的 Bean 实例，需要完成两方面的工作：</p>
-<ol>
-<li>为 Bean 实例填充属性，包括解析依赖，为 Bean 自身的初始化做好准备。</li>
-<li>Bean 自身的初始化。</li>
+<h2 id="SSH-的原理"><a href="#SSH-的原理" class="headerlink" title="SSH 的原理"></a>SSH 的原理</h2><h3 id="关于-SSH"><a href="#关于-SSH" class="headerlink" title="关于 SSH"></a>关于 SSH</h3><p>使用 SSH 协议可以连接远程服务器和服务并向它们验证，而无需在每次访问时都提供用户名和密码，Github 还可以使用 SSH 密钥对提交进行签名。</p>
+<h3 id="公钥和私钥"><a href="#公钥和私钥" class="headerlink" title="公钥和私钥"></a>公钥和私钥</h3><p>SSH 的使用（非对称加密）需要生成公钥 public key 和私钥 private key。常用的算法有 <code>rsa</code>、<code>ecdsa</code> 和 <code>ed25519</code>，相对应的公钥默认文件名即id_XXX.pub。<code>ed25519</code> 的安全性介于 <code>rsa 2048</code> 和 <code>rsa 4096</code> 之间，但性能却提升数十倍。<br>在生成密钥时，会要求你 <code>Enter passphrase (empty for no passphrase):</code>，可以输入一个口令保护私钥的使用。不为空的情况下，正常使用是需要输入这个口令的，很多人认为麻烦，因此留空。<br>公钥的权限必须是 644，私钥的权限必须是 600，否则 SSH 认为其不可靠。<br>私钥是要安全保管在客户端不能泄露的，公钥则要提供给远程服务器或服务。服务端的 <code>~/.ssh/authorized_keys</code> 里面存储着可以登录的客户端的公钥。我们将公钥粘贴到 Github 的过程就是对应于此。</p>
+<figure class="highlight shell"><table><tr><td class="code"><pre><span class="line"><span class="meta prompt_">$ </span><span class="language-bash">ssh-keygen -t rsa -b 4096 -f my_id -C <span class="string">&quot;email@example.com&quot;</span></span></span><br></pre></td></tr></table></figure>
+<ul>
+<li><code>-t</code> 表示算法，如 <code>rsa</code>。</li>
+<li><code>-b</code> 表示 <code>rsa</code> 密钥长度，默认 2048 bit，<code>ed25519</code> 不需要指定。</li>
+<li><code>-f</code> 表示文件名。</li>
+<li><code>-C</code> 表示在公钥文件中添加注释，可修改</li>
+</ul>
+<h3 id="SSH-公钥登录过程"><a href="#SSH-公钥登录过程" class="headerlink" title="SSH 公钥登录过程"></a>SSH 公钥登录过程</h3><ol>
+<li>Client 将自己的公钥存放到服务端，追加到 authorized_keys 文件。</li>
+<li>Server 收到 Client 的连接请求后，会在 authorized_keys 文件中匹配到 Client 传过来的公钥，并生成随机数 R，用公钥对随机数加密得到 pubKey(R)。</li>
+<li>Client 收到后通过私钥解密得到随机数 R，然后对随机数 R 和本次会话的 sessionKey 使用 MD5 生成摘要 Digest1，发送给服务端。</li>
+<li>Server 会对随机数 R 和会话的 sessionKey 同样使用 MD5 生成摘要 Digest2，对比相同即完成认证过程。</li>
 </ol>
-<p>在万事俱备之后，就是 Bean 自身的初始化工作。由于 Spring 的高度扩展性，这部分并不只是单纯地调用初始化方法，还包含 Aware 接口和 BeanPostProcessor 的相关处理，前者偏属于 Java 对象层面，后者偏属于 Spring Bean 层面。<br>在认同 BeanPostProcessor 的处理属于 Bean 自身初始化工作的一部分后，@PostConstruct 注解的方法被称为 Bean 的初始化方法也就不那么违和了，因为它的实现原理正是 BeanPostProcessor，这仍然在 initializeBean 的范围内。</p>
+<h3 id="避免中间人攻击"><a href="#避免中间人攻击" class="headerlink" title="避免中间人攻击"></a>避免中间人攻击</h3><p>SSH 通过口令确认避免中间人攻击，如果用户第一次登录 Server，系统会提示：</p>
+<figure class="highlight shell"><table><tr><td class="code"><pre><span class="line"><span class="meta prompt_">$ </span><span class="language-bash">ssh -T git@github.com</span></span><br><span class="line">The authenticity of host &#x27;github.com (20.205.243.166)&#x27; can&#x27;t be established.</span><br><span class="line">ECDSA key fingerprint is SHA256:p2QAMXNIC1TJYWeIOttrVc98/R1BUFWu3/LiyKgUfQM.</span><br><span class="line">Are you sure you want to continue connecting (yes/no/[fingerprint])? yes</span><br><span class="line">Warning: Permanently added &#x27;github.com,20.205.243.166&#x27; (ECDSA) to the list of known hosts.</span><br><span class="line">Hi $&#123;username&#125;! You&#x27;ve successfully authenticated, but GitHub does not provide shell access.</span><br></pre></td></tr></table></figure>
+<p>Server 需要在其网站上公示其公钥的指纹，Github 的公钥指纹<a href="https://docs.github.com/zh/authentication/keeping-your-account-and-data-secure/githubs-ssh-key-fingerprints">在这里</a>。<br>确认匹配后，客户端会在 <code>~/.ssh/known_hosts</code> 中记录，下次登录不再警告。</p>
+<h2 id="使用-SSH-免密登录服务器"><a href="#使用-SSH-免密登录服务器" class="headerlink" title="使用 SSH 免密登录服务器"></a>使用 SSH 免密登录服务器</h2><p>使用现成的密钥，将 <code>~/.ssh/id_ed25519.pub</code> 的内容追加到自己服务端的 <code>~/.ssh/authorized_keys</code> 中，使用 <code>ssh user@host</code> 成功免密登录。<br>这样一来，使用 VScode 远程连接服务器和使用 Remote Explorer 打开文件夹时，不用每次都输入密码了。</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://docs.github.com/zh/authentication/connecting-to-github-with-ssh/about-ssh">使用 SSH 进行连接 Github</a><br><a href="https://blog.csdn.net/u012408797/article/details/116196831">Git 多台电脑共用SSH Key</a><br><a href="https://blog.csdn.net/neo949332116/article/details/102926051">SSH协议登录过程详解</a><br><a href="https://docs.github.com/zh/authentication/keeping-your-account-and-data-secure/githubs-ssh-key-fingerprints">GitHub 的 SSH 密钥指纹</a><br><a href="https://zhuanlan.zhihu.com/p/110413836">使用 Ed25519 算法生成你的 SSH 密钥</a></p>
 ]]></content>
       <tags>
-        <tag>java</tag>
-        <tag>spring</tag>
+        <tag>ssh</tag>
       </tags>
   </entry>
   <entry>
-    <title>JVM GC 的测试和分析</title>
-    <url>/2023/11/01/testing-and-analysis-of-jvm-gc/</url>
-    <content><![CDATA[<h3 id="堆的组成"><a href="#堆的组成" class="headerlink" title="堆的组成"></a>堆的组成</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_">JvmGcTest_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">final</span> <span class="type">int</span> <span class="variable">_512KB</span> <span class="operator">=</span> <span class="number">512</span> * <span class="number">1024</span>;</span><br><span class="line">    <span class="keyword">public</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 class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">final</span> <span class="type">int</span> <span class="variable">_6MB</span> <span class="operator">=</span> <span class="number">6</span> * <span class="number">1024</span> * <span class="number">1024</span>;</span><br><span class="line">    <span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">final</span> <span class="type">int</span> <span class="variable">_7MB</span> <span class="operator">=</span> <span class="number">7</span> * <span class="number">1024</span> * <span class="number">1024</span>;</span><br><span class="line">    <span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">final</span> <span class="type">int</span> <span class="variable">_8MB</span> <span class="operator">=</span> <span class="number">8</span> * <span class="number">1024</span> * <span class="number">1024</span>;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// -Xms20M -Xmx20M -Xmn10M -XX:+UseSerialGC -XX:+PrintGCDetails -verbose:gc</span></span><br><span class="line">    <span class="comment">// -XX:+UseSerialGC 避免幸存区比例动态调整</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><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">Heap</span><br><span class="line"> def new generation   total 9216K, used 2010K [0x00000000fec00000, 0x00000000ff600000, 0x00000000ff600000)</span><br><span class="line">  eden space 8192K,  24% used [0x00000000fec00000, 0x00000000fedf68c8, 0x00000000ff400000)</span><br><span class="line">  from space 1024K,   0% used [0x00000000ff400000, 0x00000000ff400000, 0x00000000ff500000)</span><br><span class="line">  to   space 1024K,   0% used [0x00000000ff500000, 0x00000000ff500000, 0x00000000ff600000)</span><br><span class="line"> tenured generation   total 10240K, used 0K [0x00000000ff600000, 0x0000000100000000, 0x0000000100000000)</span><br><span class="line">   the space 10240K,   0% used [0x00000000ff600000, 0x00000000ff600000, 0x00000000ff600200, 0x0000000100000000)</span><br><span class="line"> Metaspace       used 3288K, capacity 4496K, committed 4864K, reserved 1056768K</span><br><span class="line">  class space    used 348K, capacity 388K, committed 512K, reserved 1048576K</span><br></pre></td></tr></table></figure>
+    <title>Tmux 常用命令和快捷键</title>
+    <url>/2023/06/29/tmux-frequently-used-commands/</url>
+    <content><![CDATA[<h2 id="Tmux-是什么"><a href="#Tmux-是什么" class="headerlink" title="Tmux 是什么"></a>Tmux 是什么</h2><p>Tmux 是一个终端复用器（Terminal Multiplexer），它可以将终端的会话和窗口解绑分离，达到窗口关闭，会话不终止，并且还能使用窗口再次绑定目标会话的效果，从而避免因为网络中断或者窗口关闭导致会话中运行的进程终止。</p>
+<h2 id="基本用法"><a href="#基本用法" class="headerlink" title="基本用法"></a>基本用法</h2><p>Ubuntu server 20.04 默认已安装 Tmux。如果没有，可以通过以下命令安装：</p>
+<figure class="highlight shell"><table><tr><td class="code"><pre><span class="line"><span class="meta prompt_">$ </span><span class="language-bash">sudo apt-get install tmux</span></span><br></pre></td></tr></table></figure>
 
-<p>根据打印的信息，组成如下：</p>
-<ul>
-<li><code>Heap</code>: 堆。<ul>
-<li><code>def new generation</code>: 新生代。</li>
-<li><code>tenured generation</code>: 老年代。</li>
-<li><code>Metaspace</code>: 元空间，实际上并不属于堆， <code>-XX:+PrintGCDetails</code> 将它的信息一起输出。</li>
+<h3 id="会话管理"><a href="#会话管理" class="headerlink" title="会话管理"></a>会话管理</h3><h4 id="新建会话"><a href="#新建会话" class="headerlink" title="新建会话"></a>新建会话</h4><figure class="highlight shell"><table><tr><td class="code"><pre><span class="line"><span class="meta prompt_">$ </span><span class="language-bash">tmux new -s &lt;session-name&gt;</span></span><br></pre></td></tr></table></figure>
+<h4 id="分离会话"><a href="#分离会话" class="headerlink" title="分离会话"></a>分离会话</h4><figure class="highlight shell"><table><tr><td class="code"><pre><span class="line"><span class="meta prompt_">$ </span><span class="language-bash">tmux detach</span></span><br></pre></td></tr></table></figure>
+<h4 id="查看会话列表"><a href="#查看会话列表" class="headerlink" title="查看会话列表"></a>查看会话列表</h4><figure class="highlight shell"><table><tr><td class="code"><pre><span class="line"><span class="meta prompt_">$ </span><span class="language-bash">tmux <span class="built_in">ls</span></span></span><br></pre></td></tr></table></figure>
+<h4 id="接入会话"><a href="#接入会话" class="headerlink" title="接入会话"></a>接入会话</h4><figure class="highlight shell"><table><tr><td class="code"><pre><span class="line"><span class="meta prompt_">$ </span><span class="language-bash">tmux attach -t &lt;session-name&gt;</span></span><br><span class="line"><span class="meta prompt_">$ </span><span class="language-bash">tmux attach -t &lt;session-id&gt;</span></span><br></pre></td></tr></table></figure>
+<h4 id="杀死会话"><a href="#杀死会话" class="headerlink" title="杀死会话"></a>杀死会话</h4><figure class="highlight shell"><table><tr><td class="code"><pre><span class="line"><span class="meta prompt_">$ </span><span class="language-bash">tmux kill-session -t &lt;session-name&gt;</span></span><br><span class="line"><span class="meta prompt_">$ </span><span class="language-bash">tmux kill-session -t &lt;session-id&gt;</span></span><br></pre></td></tr></table></figure>
+<h4 id="切换会话"><a href="#切换会话" class="headerlink" title="切换会话"></a>切换会话</h4><figure class="highlight shell"><table><tr><td class="code"><pre><span class="line"><span class="meta prompt_">$ </span><span class="language-bash">tmux switch -t &lt;session-name&gt;</span></span><br><span class="line"><span class="meta prompt_">$ </span><span class="language-bash">tmux switch -t &lt;session-id&gt;</span></span><br></pre></td></tr></table></figure>
+<h4 id="重命名会话"><a href="#重命名会话" class="headerlink" title="重命名会话"></a>重命名会话</h4><figure class="highlight shell"><table><tr><td class="code"><pre><span class="line"><span class="meta prompt_">$ </span><span class="language-bash">tmux rename-session -t &lt;old&gt; &lt;new&gt;</span></span><br><span class="line"><span class="meta prompt_">$ </span><span class="language-bash">tmux rename-session &lt;new&gt;</span></span><br></pre></td></tr></table></figure>
+<h4 id="会话快捷键"><a href="#会话快捷键" class="headerlink" title="会话快捷键"></a>会话快捷键</h4><ul>
+<li><strong><code>Ctrl+b d</code>：分离当前会话，猜测 detach</strong></li>
+<li><strong><code>Ctrl+b s</code>：查看会话列表并选择，session</strong></li>
+<li><strong><code>Ctrl+b $</code>：重命名当前会话名称</strong></li>
+<li><strong><code>Ctrl+d</code>：关闭当前会话</strong></li>
 </ul>
-</li>
+<h3 id="窗口管理"><a href="#窗口管理" class="headerlink" title="窗口管理"></a>窗口管理</h3><h4 id="新建窗口"><a href="#新建窗口" class="headerlink" title="新建窗口"></a>新建窗口</h4><figure class="highlight shell"><table><tr><td class="code"><pre><span class="line"><span class="meta prompt_">$ </span><span class="language-bash">tmux new-window -n &lt;window-name&gt;</span></span><br></pre></td></tr></table></figure>
+<h4 id="关闭窗口"><a href="#关闭窗口" class="headerlink" title="关闭窗口"></a>关闭窗口</h4><figure class="highlight shell"><table><tr><td class="code"><pre><span class="line"><span class="meta prompt_">$ </span><span class="language-bash">tmux kill-window -t &lt;window-name&gt;</span></span><br><span class="line"><span class="meta prompt_">$ </span><span class="language-bash">tmux kill-window</span></span><br></pre></td></tr></table></figure>
+<h4 id="切换窗口"><a href="#切换窗口" class="headerlink" title="切换窗口"></a>切换窗口</h4><figure class="highlight shell"><table><tr><td class="code"><pre><span class="line"><span class="meta prompt_">$ </span><span class="language-bash">tmux select-window -t &lt;window-name&gt;</span></span><br><span class="line"><span class="meta prompt_">$ </span><span class="language-bash">tmux select-window -t &lt;window-id&gt;</span></span><br></pre></td></tr></table></figure>
+<h4 id="重命名窗口"><a href="#重命名窗口" class="headerlink" title="重命名窗口"></a>重命名窗口</h4><figure class="highlight shell"><table><tr><td class="code"><pre><span class="line"><span class="meta prompt_">$ </span><span class="language-bash">tmux rename-window -t &lt;old&gt; &lt;new&gt;</span></span><br><span class="line"><span class="meta prompt_">$ </span><span class="language-bash">tmux rename-window &lt;new&gt;</span></span><br></pre></td></tr></table></figure>
+<h4 id="窗口快捷键"><a href="#窗口快捷键" class="headerlink" title="窗口快捷键"></a>窗口快捷键</h4><ul>
+<li><strong><code>Ctrl+b c</code>：创建一个新窗口，状态栏会显示窗口信息</strong></li>
+<li><code>Ctrl+b p</code>：切换到上一个窗口，prev</li>
+<li><code>Ctrl+b n</code>：切换到下一个窗口，next</li>
+<li><code>Ctrl+b &lt;number&gt;</code>：切换到指定编号的窗口</li>
+<li><strong><code>Ctrl+b w</code>：查看窗口列表并选择，window</strong></li>
+<li><strong><code>Ctrl+b ,</code>：重命名当前窗口</strong></li>
+<li><strong><code>Ctrl+b &amp;</code>：关闭当前窗口</strong></li>
 </ul>
-<h4 id="堆空间的比例"><a href="#堆空间的比例" class="headerlink" title="堆空间的比例"></a>堆空间的比例</h4><p>新生代中的空间占比 <code>eden:from:to</code> 在默认情况下是 <code>8:1:1</code>，与观察到的数据 <code>8192K:1024K:1024K</code> 一致。<br>新生代的空间 <code>eden + from + to</code> 为 10240K，符合 <code>-Xmn10M</code> 设置的大小。<br><code>total</code> 显示为 9216K，即 <code>eden + from</code> 的大小，是因为 <code>to</code> 的空间不计算在内。新生代可用的空间只有 <code>eden + from</code>，<code>to</code> 空间只是在使用标记-复制算法进行垃圾回收时使用。<br>老年代的空间为 10240K。<br>目前仅 <code>eden</code> 中已用 2010K，约占 <code>eden</code> 空间的 24%。</p>
-<h4 id="从内存地址分析堆空间"><a href="#从内存地址分析堆空间" class="headerlink" title="从内存地址分析堆空间"></a>从内存地址分析堆空间</h4><p>内存地址为 16 位的 16 进制的数字，64 位机器。<br><code>[0x00000000fec00000, 0x00000000ff600000, 0x00000000ff600000)</code> 分别表示地址空间的开始、已用、结束的地址指针。<br>新生代 <code>[0x00000000fec00000, 0x00000000ff600000)</code>，老年代 <code>[0x00000000ff600000, 0x0000000100000000)</code>，计算可得空间大小均为 10MB。<br><code>eden</code> 中已用的空间地址为 <code>[0x00000000fec00000, 0x00000000fedf68c8)</code>，空间大小为 2058440 byte，约等于 2010K。</p>
-<p>显而易见，新生代和老生代是一片完全连续的地址空间。</p>
-<h3 id="堆的垃圾回收"><a href="#堆的垃圾回收" class="headerlink" title="堆的垃圾回收"></a>堆的垃圾回收</h3><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> &#123;</span><br><span class="line">    List&lt;<span class="type">byte</span>[]&gt; list = <span class="keyword">new</span> <span class="title class_">ArrayList</span>&lt;&gt;();</span><br><span class="line">    list.add(<span class="keyword">new</span> <span class="title class_">byte</span>[_7MB]);</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">[GC (Allocation Failure) [DefNew: 2013K-&gt;721K(9216K), 0.0105099 secs] 2013K-&gt;721K(19456K), 0.0105455 secs] [Times: user=0.00 sys=0.00, real=0.01 secs] </span><br><span class="line">Heap</span><br><span class="line"> def new generation   total 9216K, used 8135K [0x00000000fec00000, 0x00000000ff600000, 0x00000000ff600000)</span><br><span class="line">  eden space 8192K,  90% used [0x00000000fec00000, 0x00000000ff33d8c0, 0x00000000ff400000)</span><br><span class="line">  from space 1024K,  70% used [0x00000000ff500000, 0x00000000ff5b45f0, 0x00000000ff600000)</span><br><span class="line">  to   space 1024K,   0% used [0x00000000ff400000, 0x00000000ff400000, 0x00000000ff500000)</span><br><span class="line"> tenured generation   total 10240K, used 0K [0x00000000ff600000, 0x0000000100000000, 0x0000000100000000)</span><br><span class="line">   the space 10240K,   0% used [0x00000000ff600000, 0x00000000ff600000, 0x00000000ff600200, 0x0000000100000000)</span><br><span class="line"> Metaspace       used 3354K, capacity 4496K, committed 4864K, reserved 1056768K</span><br><span class="line">  class space    used 360K, capacity 388K, committed 512K, reserved 1048576K</span><br></pre></td></tr></table></figure>
-
-<p><code>Allocation Failure</code>，正常情况下，新对象总是分配在 Eden，分配空间失败，<code>eden</code> 的剩余空间不足以存放 7M 大小的对象，新生代发生 <code>minor GC</code>。<br><code>[DefNew: 2013K-&gt;721K(9216K), 0.0105099 secs]</code>，新生代在垃圾回收前后空间的占用变化和耗时。<br><code>2013K-&gt;721K(19456K), 0.0105455 secs</code>，整个堆在垃圾回收前后空间的占用变化和耗时。</p>
-<h4 id="GC-类型"><a href="#GC-类型" class="headerlink" title="GC 类型"></a>GC 类型</h4><ul>
-<li>GC: minor GC。</li>
-<li>Fulle GC: full GC。</li>
+<h3 id="窗格管理"><a href="#窗格管理" class="headerlink" title="窗格管理"></a>窗格管理</h3><h4 id="划分窗格"><a href="#划分窗格" class="headerlink" title="划分窗格"></a>划分窗格</h4><p>猜测 vertical，horizontal。</p>
+<figure class="highlight shell"><table><tr><td class="code"><pre><span class="line"><span class="meta prompt_">$ </span><span class="language-bash">tmux split-window [-v]</span></span><br><span class="line"><span class="meta prompt_">$ </span><span class="language-bash">tmux split-window -h</span></span><br></pre></td></tr></table></figure>
+<h4 id="移动光标"><a href="#移动光标" class="headerlink" title="移动光标"></a>移动光标</h4><p>猜测 upper，down，left，right。</p>
+<figure class="highlight shell"><table><tr><td class="code"><pre><span class="line"><span class="meta prompt_">$ </span><span class="language-bash">tmux select-pane -U</span></span><br><span class="line"><span class="meta prompt_">$ </span><span class="language-bash">tmux select-pane -D</span></span><br><span class="line"><span class="meta prompt_">$ </span><span class="language-bash">tmux select-pane -L</span></span><br><span class="line"><span class="meta prompt_">$ </span><span class="language-bash">tmux select-pane -R</span></span><br></pre></td></tr></table></figure>
+<h4 id="交换窗格"><a href="#交换窗格" class="headerlink" title="交换窗格"></a>交换窗格</h4><p>当前窗格和上一个或下一个窗格交换位置。</p>
+<figure class="highlight shell"><table><tr><td class="code"><pre><span class="line"><span class="meta prompt_">$ </span><span class="language-bash">tmux swap-pane -U</span></span><br><span class="line"><span class="meta prompt_">$ </span><span class="language-bash">tmux swap-pane -D</span></span><br></pre></td></tr></table></figure>
+<h4 id="窗格快捷键"><a href="#窗格快捷键" class="headerlink" title="窗格快捷键"></a>窗格快捷键</h4><ul>
+<li><strong><code>Ctrl+b &quot;</code>：上下划分窗格</strong></li>
+<li><strong><code>Ctrl+b %</code>：左右划分窗格</strong></li>
+<li><strong><code>Ctrl+b &lt;arrow key&gt;</code>：使用方向键切换窗格</strong></li>
+<li><code>Ctrl+b ;</code>：光标切换到上一个窗格</li>
+<li><code>Ctrl+b o</code>：光标切换到下一个窗格</li>
+<li><code>Ctrl+b &#123;</code>：当前窗格和上一个窗格交换位置</li>
+<li><code>Ctrl+b &#125;</code>：当前窗格和下一个窗格交换位置</li>
+<li><strong><code>Ctrl+b x</code>：关闭当前窗格</strong></li>
+<li><code>Ctrl+b !</code>：将当前窗格拆分为一个独立窗口</li>
+<li><code>Ctrl+b z</code>：当前窗格全屏显示，再使用一次会变回原来大小，状态栏会有大写的 Z 标识</li>
+<li><code>Ctrl+b q</code>：显示窗格编号</li>
 </ul>
-<h4 id="from-和-to-的角色变换"><a href="#from-和-to-的角色变换" class="headerlink" title="from 和 to 的角色变换"></a>from 和 to 的角色变换</h4><p><code>from</code> 的已用空间的地址为 <code>[0x00000000ff500000, 0x00000000ff5b45f0)</code>，空间大小为 738800 byte，约 721K，与 GC 后的新生代空间占用大小一致。在垃圾回收后，<code>eden</code> 区域存活的对象全部转移到了原 <code>to</code> 空间，<code>from</code> 和 <code>to</code> 空间的角色相互转换（从地址空间的信息可以看到此时 <code>to</code> 的地址指针比 <code>from</code> 的地址指针小）。<br><code>eden</code> 的已用空间的地址为 <code>[0x00000000fec00000, 0x00000000ff33d8c0)</code>，空间大小为 7592128 byte，约 7.24M，比 7M 大不少。此时 <code>eden</code> 区域除了 <code>byte[]</code> 对象外，还存储了其他对象，比如为了创建 <code>List&lt;byte[]&gt;</code> 对象而新加载的类对象。</p>
-<h3 id="eden-空间足够时不发生-GC"><a href="#eden-空间足够时不发生-GC" class="headerlink" title="eden 空间足够时不发生 GC"></a>eden 空间足够时不发生 GC</h3><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> &#123;</span><br><span class="line">    List&lt;<span class="type">byte</span>[]&gt; list = <span class="keyword">new</span> <span class="title class_">ArrayList</span>&lt;&gt;();</span><br><span class="line">    list.add(<span class="keyword">new</span> <span class="title class_">byte</span>[_7MB]);</span><br><span class="line">    list.add(<span class="keyword">new</span> <span class="title class_">byte</span>[_512KB]);</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">[GC (Allocation Failure) [DefNew: 2013K-&gt;721K(9216K), 0.0011172 secs] 2013K-&gt;721K(19456K), 0.0011443 secs] [Times: user=0.00 sys=0.00, real=0.00 secs] </span><br><span class="line">Heap</span><br><span class="line"> def new generation   total 9216K, used 8647K [0x00000000fec00000, 0x00000000ff600000, 0x00000000ff600000)</span><br><span class="line">  eden space 8192K,  96% used [0x00000000fec00000, 0x00000000ff3bd8d0, 0x00000000ff400000)</span><br><span class="line">  from space 1024K,  70% used [0x00000000ff500000, 0x00000000ff5b45f0, 0x00000000ff600000)</span><br><span class="line">  to   space 1024K,   0% used [0x00000000ff400000, 0x00000000ff400000, 0x00000000ff500000)</span><br><span class="line"> tenured generation   total 10240K, used 0K [0x00000000ff600000, 0x0000000100000000, 0x0000000100000000)</span><br><span class="line">   the space 10240K,   0% used [0x00000000ff600000, 0x00000000ff600000, 0x00000000ff600200, 0x0000000100000000)</span><br><span class="line"> Metaspace       used 3354K, capacity 4496K, committed 4864K, reserved 1056768K</span><br><span class="line">  class space    used 360K, capacity 388K, committed 512K, reserved 1048576K</span><br></pre></td></tr></table></figure>
-
-<p>由于 <code>eden</code> 区域还能放下 512K 的对象，所以仍然只会发生一次垃圾回收。<br><code>eden</code> 区域的已用空间比例上升到 96%，已用空间的地址为 <code>[0x00000000fec00000, 0x00000000ff3bd8d0)</code>，空间大小为 8116432 byte，约 7.74M，比上一次增加了 524304 byte，即 <code>512 * 1024 + 16</code>。显然第二次添加时，不再因为创建 <code>List&lt;byte[]&gt;</code> 而创建额外的对象，只有创建对象所需的 512K 和 16 字节的对象头。<strong>这一刻数值的精确让人欣喜hhh</strong>。</p>
-<h3 id="新生代空间不足，部分对象提前晋升到老年代"><a href="#新生代空间不足，部分对象提前晋升到老年代" class="headerlink" title="新生代空间不足，部分对象提前晋升到老年代"></a>新生代空间不足，部分对象提前晋升到老年代</h3><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> &#123;</span><br><span class="line">    List&lt;<span class="type">byte</span>[]&gt; list = <span class="keyword">new</span> <span class="title class_">ArrayList</span>&lt;&gt;();</span><br><span class="line">    list.add(<span class="keyword">new</span> <span class="title class_">byte</span>[_7MB]);</span><br><span class="line">    list.add(<span class="keyword">new</span> <span class="title class_">byte</span>[_512KB]);</span><br><span class="line">    list.add(<span class="keyword">new</span> <span class="title class_">byte</span>[_512KB]);</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">[GC (Allocation Failure) [DefNew: 2013K-&gt;721K(9216K), 0.0013580 secs] 2013K-&gt;721K(19456K), 0.0013932 secs] [Times: user=0.00 sys=0.00, real=0.00 secs] </span><br><span class="line">[GC (Allocation Failure) [DefNew: 8565K-&gt;512K(9216K), 0.0046378 secs] 8565K-&gt;8396K(19456K), 0.0046540 secs] [Times: user=0.00 sys=0.00, real=0.00 secs] </span><br><span class="line">Heap</span><br><span class="line"> def new generation   total 9216K, used 1350K [0x00000000fec00000, 0x00000000ff600000, 0x00000000ff600000)</span><br><span class="line">  eden space 8192K,  10% used [0x00000000fec00000, 0x00000000fecd1a20, 0x00000000ff400000)</span><br><span class="line">  from space 1024K,  50% used [0x00000000ff400000, 0x00000000ff480048, 0x00000000ff500000)</span><br><span class="line">  to   space 1024K,   0% used [0x00000000ff500000, 0x00000000ff500000, 0x00000000ff600000)</span><br><span class="line"> tenured generation   total 10240K, used 7884K [0x00000000ff600000, 0x0000000100000000, 0x0000000100000000)</span><br><span class="line">   the space 10240K,  77% used [0x00000000ff600000, 0x00000000ffdb33a0, 0x00000000ffdb3400, 0x0000000100000000)</span><br><span class="line"> Metaspace       used 3354K, capacity 4496K, committed 4864K, reserved 1056768K</span><br><span class="line">  class space    used 360K, capacity 388K, committed 512K, reserved 1048576K</span><br></pre></td></tr></table></figure>
-
-<p>在第三次添加时，由于 <code>eden</code> 空间不足，因此又发生了第二次垃圾回收。<br><code>[DefNew: 8565K-&gt;512K(9216K), 0.0046378 secs]</code>，新生代的空间占用下降到了 512K，应该是在 from 中留下了第二次添加时的 512K。<br>在第二次添加完成后，<code>eden</code> <code>[0x00000000fec00000, 0x00000000ff3bd8d0)</code> 和 <code>from</code> <code>[0x00000000ff500000, 0x00000000ff5b45f0)</code> 占用的空间为 <code>8116432 + 738800 = 8855232</code> 约 8647.7K，略大于 8565K。很奇怪，第二次垃圾回收前，新生代的空间占用为什么有小幅度下降。<br><code>8565K-&gt;8396K(19456K), 0.0046540 secs</code>，堆的占用空间并未发生明显下降。部分对象因为新生代空间不足，提前晋升到了老年代中。8396K - 512 K 剩余 7884K，全部晋升到老年代，符合 77% 的统计数据。<br><code>eden</code> 中加入了第三次添加时的对象，大于 512K 不少。<br>此时 <code>eden</code>、<code>from</code>、<code>tenured</code> 中均有不好确认成分的空间占用，比如 from 中多了 56 字节。</p>
-<h3 id="新生代空间不足，大对象直接在老年代创建"><a href="#新生代空间不足，大对象直接在老年代创建" class="headerlink" title="新生代空间不足，大对象直接在老年代创建"></a>新生代空间不足，大对象直接在老年代创建</h3><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> &#123;</span><br><span class="line">    List&lt;<span class="type">byte</span>[]&gt; list = <span class="keyword">new</span> <span class="title class_">ArrayList</span>&lt;&gt;();</span><br><span class="line">    list.add(<span class="keyword">new</span> <span class="title class_">byte</span>[_8MB]);</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">Heap</span><br><span class="line"> def <span class="keyword">new</span> <span class="title class_">generation</span>   total 9216K, used 2177K [<span class="number">0x00000000fec00000</span>, <span class="number">0x00000000ff600000</span>, <span class="number">0x00000000ff600000</span>)</span><br><span class="line">  eden space 8192K,  <span class="number">26</span>% used [<span class="number">0x00000000fec00000</span>, <span class="number">0x00000000fee20730</span>, <span class="number">0x00000000ff400000</span>)</span><br><span class="line">  from space 1024K,   <span class="number">0</span>% used [<span class="number">0x00000000ff400000</span>, <span class="number">0x00000000ff400000</span>, <span class="number">0x00000000ff500000</span>)</span><br><span class="line">  to   space 1024K,   <span class="number">0</span>% used [<span class="number">0x00000000ff500000</span>, <span class="number">0x00000000ff500000</span>, <span class="number">0x00000000ff600000</span>)</span><br><span class="line"> tenured generation   total 10240K, used 8192K [<span class="number">0x00000000ff600000</span>, <span class="number">0x0000000100000000</span>, <span class="number">0x0000000100000000</span>)</span><br><span class="line">   the space 10240K,  <span class="number">80</span>% used [<span class="number">0x00000000ff600000</span>, <span class="number">0x00000000ffe00010</span>, <span class="number">0x00000000ffe00200</span>, <span class="number">0x0000000100000000</span>)</span><br><span class="line"> Metaspace       used 3353K, capacity 4496K, committed 4864K, reserved 1056768K</span><br><span class="line">  <span class="keyword">class</span> <span class="title class_">space</span>    used 360K, capacity 388K, committed 512K, reserved 1048576K</span><br></pre></td></tr></table></figure>
-
-<p>在 Eden 空间肯定不足而老年代空间足够的情况下，大对象会直接在老年代中创建，此时不会发生 GC。</p>
-<h3 id="内存不足-OOM"><a href="#内存不足-OOM" class="headerlink" title="内存不足 OOM"></a>内存不足 OOM</h3><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> &#123;</span><br><span class="line">    List&lt;<span class="type">byte</span>[]&gt; list = <span class="keyword">new</span> <span class="title class_">ArrayList</span>&lt;&gt;();</span><br><span class="line">    list.add(<span class="keyword">new</span> <span class="title class_">byte</span>[_8MB]);</span><br><span class="line">    list.add(<span class="keyword">new</span> <span class="title class_">byte</span>[_8MB]);</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">waiting...</span><br><span class="line">[GC (Allocation Failure) [DefNew: 4711K-&gt;928K(9216K), 0.0017245 secs][Tenured: 8192K-&gt;9117K(10240K), 0.0021690 secs] 12903K-&gt;9117K(19456K), [Metaspace: 4267K-&gt;4267K(1056768K)], 0.0039336 secs] [Times: user=0.00 sys=0.00, real=0.00 secs] </span><br><span class="line">[Full GC (Allocation Failure) [Tenured: 9117K-&gt;9063K(10240K), 0.0014352 secs] 9117K-&gt;9063K(19456K), [Metaspace: 4267K-&gt;4267K(1056768K)], 0.0014614 secs] [Times: user=0.00 sys=0.00, real=0.00 secs] </span><br><span class="line">Exception in thread &quot;Thread-0&quot; java.lang.OutOfMemoryError: Java heap space</span><br><span class="line">	at com.moralok.jvm.gc.JvmGcTest.lambda$main$0(JvmGcTest.java:27)</span><br><span class="line">	at com.moralok.jvm.gc.JvmGcTest$$Lambda$1/2003749087.run(Unknown Source)</span><br><span class="line">	at java.lang.Thread.run(Thread.java:750)</span><br><span class="line"></span><br><span class="line">Heap</span><br><span class="line"> def new generation   total 9216K, used 1502K [0x00000000fec00000, 0x00000000ff600000, 0x00000000ff600000)</span><br><span class="line">  eden space 8192K,  18% used [0x00000000fec00000, 0x00000000fed77a00, 0x00000000ff400000)</span><br><span class="line">  from space 1024K,   0% used [0x00000000ff500000, 0x00000000ff500000, 0x00000000ff600000)</span><br><span class="line">  to   space 1024K,   0% used [0x00000000ff400000, 0x00000000ff400000, 0x00000000ff500000)</span><br><span class="line"> tenured generation   total 10240K, used 9063K [0x00000000ff600000, 0x0000000100000000, 0x0000000100000000)</span><br><span class="line">   the space 10240K,  88% used [0x00000000ff600000, 0x00000000ffed9c50, 0x00000000ffed9e00, 0x0000000100000000)</span><br><span class="line"> Metaspace       used 4787K, capacity 4884K, committed 4992K, reserved 1056768K</span><br><span class="line">  class space    used 522K, capacity 558K, committed 640K, reserved 1048576K</span><br></pre></td></tr></table></figure>
-
-<p>当新生代和老年代的空间均不足时，在尝试 GC 和 Full GC 后仍不能成功分配对象，就会发生 <code>OutOfMemoryError</code>。</p>
-<h4 id="线程中发生内存不足，不会影响其他线程"><a href="#线程中发生内存不足，不会影响其他线程" class="headerlink" title="线程中发生内存不足，不会影响其他线程"></a>线程中发生内存不足，不会影响其他线程</h4><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> &#123;</span><br><span class="line">    List&lt;<span class="type">byte</span>[]&gt; list = <span class="keyword">new</span> <span class="title class_">ArrayList</span>&lt;&gt;();</span><br><span class="line"></span><br><span class="line">    <span class="keyword">new</span> <span class="title class_">Thread</span>(() -&gt; &#123;</span><br><span class="line">        list.add(<span class="keyword">new</span> <span class="title class_">byte</span>[_8MB]);</span><br><span class="line">        list.add(<span class="keyword">new</span> <span class="title class_">byte</span>[_8MB]);</span><br><span class="line">    &#125;).start();</span><br><span class="line"></span><br><span class="line">    System.out.println(<span class="string">&quot;waiting...&quot;</span>);</span><br><span class="line">    <span class="keyword">try</span> &#123;</span><br><span class="line">        System.in.read();</span><br><span class="line">    &#125; <span class="keyword">catch</span> (IOException 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>
-
-<figure class="highlight console"><table><tr><td class="code"><pre><span class="line">[GC (Allocation Failure) [DefNew: 2013K-&gt;721K(9216K), 0.0012274 secs][Tenured: 8192K-&gt;8912K(10240K), 0.0113036 secs] 10205K-&gt;8912K(19456K), [Metaspace: 3345K-&gt;3345K(1056768K)], 0.0125751 secs] [Times: user=0.00 sys=0.00, real=0.01 secs] </span><br><span class="line">[Full GC (Allocation Failure) [Tenured: 8912K-&gt;8895K(10240K), 0.0011880 secs] 8912K-&gt;8895K(19456K), [Metaspace: 3345K-&gt;3345K(1056768K)], 0.0012009 secs] [Times: user=0.00 sys=0.00, real=0.00 secs] </span><br><span class="line">Heap</span><br><span class="line"> def new generation   total 9216K, used 246K [0x00000000fec00000, 0x00000000ff600000, 0x00000000ff600000)</span><br><span class="line">  eden space 8192K,   3% used [0x00000000fec00000, 0x00000000fec3d890, 0x00000000ff400000)</span><br><span class="line">  from space 1024K,   0% used [0x00000000ff500000, 0x00000000ff500000, 0x00000000ff600000)</span><br><span class="line">  to   space 1024K,   0% used [0x00000000ff400000, 0x00000000ff400000, 0x00000000ff500000)</span><br><span class="line"> tenured generation   total 10240K, used 8895K [0x00000000ff600000, 0x0000000100000000, 0x0000000100000000)</span><br><span class="line">   the space 10240K,  86% used [0x00000000ff600000, 0x00000000ffeafce0, 0x00000000ffeafe00, 0x0000000100000000)</span><br><span class="line"> Metaspace       used 3380K, capacity 4496K, committed 4864K, reserved 1056768K</span><br><span class="line">  class space    used 363K, capacity 388K, committed 512K, reserved 1048576K</span><br><span class="line">Exception in thread &quot;main&quot; java.lang.OutOfMemoryError: Java heap space</span><br><span class="line">	at com.moralok.jvm.gc.JvmGcTest.main(JvmGcTest.java:21)</span><br></pre></td></tr></table></figure>
-
-<p>当 <code>Thread-0</code> 发生 <code>OutOfMemoryError</code> 后，<code>main</code> 线程仍然正常运行。</p>
-<h3 id="大对象的划分指标"><a href="#大对象的划分指标" class="headerlink" title="大对象的划分指标"></a>大对象的划分指标</h3><p>当创建的大对象 + 对象头的容量小于等于 <code>eden</code>，如果 GC 后的存活对象可以放入 <code>to</code>，那么还是会先在 <code>eden</code> 中创建大对象。<br>在本案例中，又会马上发生一次 GC，大对象提前晋升到老年代中。</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> &#123;</span><br><span class="line">    List&lt;<span class="type">byte</span>[]&gt; list = <span class="keyword">new</span> <span class="title class_">ArrayList</span>&lt;&gt;();</span><br><span class="line">    list.add(<span class="keyword">new</span> <span class="title class_">byte</span>[_8MB - <span class="number">16</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">[GC (Allocation Failure) [DefNew: 2013K-&gt;693K(9216K), 0.0015517 secs] 2013K-&gt;693K(19456K), 0.0015828 secs] [Times: user=0.00 sys=0.00, real=0.00 secs] </span><br><span class="line">[GC (Allocation Failure) [DefNew: 8885K-&gt;0K(9216K), 0.0048110 secs] 8885K-&gt;8885K(19456K), 0.0048264 secs] [Times: user=0.00 sys=0.02, real=0.00 secs] </span><br><span class="line">Heap</span><br><span class="line"> def new generation   total 9216K, used 410K [0x00000000fec00000, 0x00000000ff600000, 0x00000000ff600000)</span><br><span class="line">  eden space 8192K,   5% used [0x00000000fec00000, 0x00000000fec66958, 0x00000000ff400000)</span><br><span class="line">  from space 1024K,   0% used [0x00000000ff400000, 0x00000000ff400000, 0x00000000ff500000)</span><br><span class="line">  to   space 1024K,   0% used [0x00000000ff500000, 0x00000000ff500000, 0x00000000ff600000)</span><br><span class="line"> tenured generation   total 10240K, used 8885K [0x00000000ff600000, 0x0000000100000000, 0x0000000100000000)</span><br><span class="line">   the space 10240K,  86% used [0x00000000ff600000, 0x00000000ffead580, 0x00000000ffead600, 0x0000000100000000)</span><br><span class="line"> Metaspace       used 3321K, capacity 4496K, committed 4864K, reserved 1056768K</span><br><span class="line">  class space    used 354K, capacity 388K, committed 512K, reserved 1048576K</span><br></pre></td></tr></table></figure>
-
-<p>尽管最终大部分对象提前晋升到老年代，但是可以看到第二次 GC 前的新生代空间占用，可见数组分配时，所需空间刚好为 Eden 空间大小时，还是会在 eden 创建对象。</p>
-<h3 id="注意事项"><a href="#注意事项" class="headerlink" title="注意事项"></a>注意事项</h3><ul>
-<li>正常情况下，新对象都是在 eden 中创建。</li>
-<li>空间足够的意思并非空间占用相加的值仍小于总额，而是有连续的一片内存可供分配。因此紧凑才能利用率高。</li>
-<li>正常情况下，GC 前 to 区域总是为空，GC 后 eden 区域总是为空。</li>
-<li>正常情况下，GC 后 eden 和 from 的存活对象要么去了 to，要么去老年代。</li>
-<li>只要 GC 后腾空 eden，创建在 eden 中的新对象的空间占用可以等于 eden 的大小。</li>
+<h3 id="其他命令"><a href="#其他命令" class="headerlink" title="其他命令"></a>其他命令</h3><h4 id="进入翻页模式"><a href="#进入翻页模式" class="headerlink" title="进入翻页模式"></a>进入翻页模式</h4><ul>
+<li><strong><code>Ctrl+b [</code>：进入翻页模式</strong></li>
+<li><code>q</code>：退出翻页模式</li>
 </ul>
-<p>尽管总体上有迹可循，但是 GC 的具体情况，仍然需要具体分析，有很多分支情况未一一确认。</p>
+<h4 id="列出所有快捷键，及其对应的-Tmux-命令"><a href="#列出所有快捷键，及其对应的-Tmux-命令" class="headerlink" title="列出所有快捷键，及其对应的 Tmux 命令"></a>列出所有快捷键，及其对应的 Tmux 命令</h4><figure class="highlight shell"><table><tr><td class="code"><pre><span class="line"><span class="meta prompt_">$ </span><span class="language-bash">tmux list-keys</span></span><br></pre></td></tr></table></figure>
+<h4 id="列出所有-Tmux-命令及其参数"><a href="#列出所有-Tmux-命令及其参数" class="headerlink" title="列出所有 Tmux 命令及其参数"></a>列出所有 Tmux 命令及其参数</h4><figure class="highlight shell"><table><tr><td class="code"><pre><span class="line"><span class="meta prompt_">$ </span><span class="language-bash">tmux list-commands</span></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://www.ruanyifeng.com/blog/2019/10/tmux.html">Tmux 使用教程</a><br><a href="https://blog.csdn.net/weixin_51311218/article/details/122172339">Tmux 学习</a></p>
 ]]></content>
       <tags>
-        <tag>java</tag>
-        <tag>jvm</tag>
+        <tag>tmux</tag>
       </tags>
   </entry>
   <entry>
@@ -1124,111 +978,145 @@
       </tags>
   </entry>
   <entry>
-    <title>字符串常量池的测试和分析</title>
-    <url>/2023/11/03/testing-and-analysis-of-StringTable/</url>
-    <content><![CDATA[<p>如果你准备过 Java 的面试，应该看到过一个问题：“<code>String s1 = new String(&quot;abc&quot;);</code> 这个语句创建了几个字符串对象”。这个问题曾经困扰我，当时的我不能理解这个问题想要考察的是什么？<br>答案中或许提及了字符串常量池，但是如果细究起来，会发现答案并不完善，有些令人困惑，甚至问题本身就有一定的误导作用。它很容易让初学者以为创建一个字符串对象和创建一个其他类型的对象在过程上是有一些区别的。<br>其实关键的地方在于 “abc” 而不是 <code>new String(&quot;abc&quot;)</code>。</p>
-<h2 id="字符串常量池的作用"><a href="#字符串常量池的作用" class="headerlink" title="字符串常量池的作用"></a>字符串常量池的作用</h2><h3 id="字符串字面量"><a href="#字符串字面量" class="headerlink" title="字符串字面量"></a>字符串字面量</h3><p>字面量(literal)是用于表达源代码中的一个固定值的表示法(notion)，比如代码中的整数、浮点数、字符串。简而言之，字符串字面量就是双引号包裹的字符串，例如：</p>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="type">String</span> <span class="variable">s1</span> <span class="operator">=</span> <span class="string">&quot;a&quot;</span>;</span><br></pre></td></tr></table></figure>
+    <title>Spring Bean 加载过程</title>
+    <url>/2023/08/10/how-does-Spring-load-beans/</url>
+    <content><![CDATA[<h2 id="Spring-Bean-生命周期"><a href="#Spring-Bean-生命周期" class="headerlink" title="Spring Bean 生命周期"></a>Spring Bean 生命周期</h2><img src="/2023/08/10/how-does-Spring-load-beans/Pasted%20image%2020231118213120.png" class="" title="Spring Bean 生命周期">
 
-<p>在 Java 中，字符串对象就是一个 String 类型的对象，因此在程序运行时，String 类型的变量 s1 指向的一定是一个 String 对象。<strong>字面量 “a” 在某一个时刻，没有经过 new 关键字，变成了一个 String 对象</strong>。</p>
-<p>接下来我们来思考一个问题，程序中每一个字符串字面量都要对应着生成一个单独的 String 对象吗？考虑到 Java 中 String 对象是不可变的，显然相同的字符串字面量完全可以共用一个 String 对象从而避免重复创建对象。JVM 也是这样设计的，这些可以共用的 String 对象组成了一个字符串常量池。</p>
+<h2 id="获取-Bean"><a href="#获取-Bean" class="headerlink" title="获取 Bean"></a>获取 Bean</h2><p>获取指定 Bean 的入口方法是 getBean，在 Spring 上下文刷新过程中，就依次调用 <code>AbstractBeanFactory#getBean(java.lang.String)</code> 方法获取 <code>non-lazy-init</code> 的 Bean。</p>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> Object <span class="title function_">getBean</span><span class="params">(String name)</span> <span class="keyword">throws</span> BeansException &#123;</span><br><span class="line">    <span class="comment">// 具体工作由 doGetBean 完成</span></span><br><span class="line">    <span class="keyword">return</span> doGetBean(name, <span class="literal">null</span>, <span class="literal">null</span>, <span class="literal">false</span>);</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<h3 id="deGetBean"><a href="#deGetBean" class="headerlink" title="deGetBean"></a>deGetBean</h3><p>作为公共处理逻辑，由 AbstractBeanFactory 自己实现。</p>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">protected</span> &lt;T&gt; T <span class="title function_">doGetBean</span><span class="params">(</span></span><br><span class="line"><span class="params">    <span class="keyword">final</span> String name, <span class="keyword">final</span> Class&lt;T&gt; requiredType, <span class="keyword">final</span> Object[] args, <span class="type">boolean</span> typeCheckOnly)</span> </span><br><span class="line">    <span class="keyword">throws</span> BeansException &#123;</span><br><span class="line">    <span class="comment">// 转换名称：去除 FactoryBean 的前缀 &amp;，将别名转换为规范名称</span></span><br><span class="line">    <span class="keyword">final</span> <span class="type">String</span> <span class="variable">beanName</span> <span class="operator">=</span> transformedBeanName(name);</span><br><span class="line">    Object bean;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 检查单例缓存中是否已存在</span></span><br><span class="line">    <span class="type">Object</span> <span class="variable">sharedInstance</span> <span class="operator">=</span> getSingleton(beanName);</span><br><span class="line">    <span class="keyword">if</span> (sharedInstance != <span class="literal">null</span> &amp;&amp; args == <span class="literal">null</span>) &#123;</span><br><span class="line">        <span class="comment">// ...</span></span><br><span class="line">        <span class="comment">// 如果已存在，直接返回该实例或者使用该实例（FactoryBean）创建并返回对象</span></span><br><span class="line">        bean = getObjectForBeanInstance(sharedInstance, name, beanName, <span class="literal">null</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">// 如果当前 Bean 是一个正在创建中的 prototype 类型，表明可能发生循环引用</span></span><br><span class="line">        <span class="comment">// 注意：Spring 并未解决 prototype 类型的循环引用问题，要抛出异常</span></span><br><span class="line">        <span class="keyword">if</span> (isPrototypeCurrentlyInCreation(beanName)) &#123;</span><br><span class="line">            <span class="keyword">throw</span> <span class="keyword">new</span> <span class="title class_">BeanCurrentlyInCreationException</span>(beanName);</span><br><span class="line">        &#125;</span><br><span class="line">        </span><br><span class="line">        <span class="comment">// 如果当前 beanFactory 没有 bean 定义，去 parent beanFactory 中查找</span></span><br><span class="line">        <span class="type">BeanFactory</span> <span class="variable">parentBeanFactory</span> <span class="operator">=</span> getParentBeanFactory();</span><br><span class="line">        <span class="keyword">if</span> (parentBeanFactory != <span class="literal">null</span> &amp;&amp; !containsBeanDefinition(beanName)) &#123;</span><br><span class="line">            <span class="type">String</span> <span class="variable">nameToLookup</span> <span class="operator">=</span> originalBeanName(name);</span><br><span class="line">            <span class="keyword">if</span> (args != <span class="literal">null</span>) &#123;</span><br><span class="line">                <span class="keyword">return</span> (T) parentBeanFactory.getBean(nameToLookup, args);</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> parentBeanFactory.getBean(nameToLookup, requiredType);</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> (!typeCheckOnly) &#123;</span><br><span class="line">            <span class="comment">// 标记为至少创建过一次</span></span><br><span class="line">            markBeanAsCreated(beanName);</span><br><span class="line">        &#125;</span><br><span class="line">        </span><br><span class="line">        <span class="keyword">try</span> &#123;</span><br><span class="line">            <span class="keyword">final</span> <span class="type">RootBeanDefinition</span> <span class="variable">mbd</span> <span class="operator">=</span> getMergedLocalBeanDefinition(beanName);</span><br><span class="line">            checkMergedBeanDefinition(mbd, beanName, args);</span><br><span class="line"></span><br><span class="line">            <span class="comment">// 确保 bean 依赖的 bean（构造器参数） 都已实例化</span></span><br><span class="line">            String[] dependsOn = mbd.getDependsOn();</span><br><span class="line">            <span class="keyword">if</span> (dependsOn != <span class="literal">null</span>) &#123;</span><br><span class="line">                <span class="keyword">for</span> (String dep : dependsOn) &#123;</span><br><span class="line">                    <span class="keyword">if</span> (isDependent(beanName, dep)) &#123;</span><br><span class="line">                        <span class="comment">// 注意：Spring 并未解决构造器方法中的循环引用问题，要抛异常</span></span><br><span class="line">                    &#125;</span><br><span class="line">                    <span class="comment">// 注册依赖关系，确保先销毁被依赖的 bean</span></span><br><span class="line">                    registerDependentBean(dep, beanName);</span><br><span class="line">                    <span class="comment">// 递归，获取依赖的 bean</span></span><br><span class="line">                    getBean(dep);</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">if</span> (mbd.isSingleton()) &#123;</span><br><span class="line">            <span class="comment">// 如果是单例类型（绝大多数都是此类型）</span></span><br><span class="line">            <span class="comment">// 再次从缓存中获取，如果仍不存在，则使用传入的 ObjectFactory 创建</span></span><br><span class="line">            sharedInstance = getSingleton(beanName, <span class="keyword">new</span> <span class="title class_">ObjectFactory</span>&lt;Object&gt;(</span><br><span class="line">                &#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_">getObject</span><span class="params">()</span> <span class="keyword">throws</span> BeansException &#123;</span><br><span class="line">                        <span class="keyword">try</span> &#123;</span><br><span class="line">                            <span class="comment">// 创建 bean</span></span><br><span class="line">                            <span class="keyword">return</span> createBean(beanName, mbd, args);</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">// 由于可能已经提前暴露，需要显示地销毁                </span></span><br><span class="line">                            destroySingleton(beanName);</span><br><span class="line">                            <span class="keyword">throw</span> ex;</span><br><span class="line">                        &#125;</span><br><span class="line">                    &#125;</span><br><span class="line">                &#125;);</span><br><span class="line">            bean = getObjectForBeanInstance(sharedInstance, name, beanName, mbd);</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="keyword">else</span> <span class="keyword">if</span> (mbd.isPrototype()) &#123;</span><br><span class="line">            <span class="comment">// 如果是原型类型，每次都新创建一个</span></span><br><span class="line">            <span class="comment">// ...</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">// 如果是其他 scope 类型</span></span><br><span class="line">            <span class="comment">// ...</span></span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="keyword">catch</span> (BeansException ex) &#123;</span><br><span class="line">        cleanupAfterBeanCreationFailure(beanName);</span><br><span class="line">        <span class="keyword">throw</span> ex;</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<h3 id="getSingleton"><a href="#getSingleton" class="headerlink" title="getSingleton"></a>getSingleton</h3><figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> Object <span class="title function_">getSingleton</span><span class="params">(String beanName, ObjectFactory&lt;?&gt; singletonFactory)</span> &#123;</span><br><span class="line">    <span class="comment">// 加锁</span></span><br><span class="line">    <span class="keyword">synchronized</span> (<span class="built_in">this</span>.singletonObjects) &#123;</span><br><span class="line">        <span class="comment">// 再次从缓存中获取（和调用前从缓存中获取构成双重校验）</span></span><br><span class="line">        <span class="type">Object</span> <span class="variable">singletonObject</span> <span class="operator">=</span> <span class="built_in">this</span>.singletonObjects.get(beanName);</span><br><span class="line">        <span class="keyword">if</span> (singletonObject == <span class="literal">null</span>) &#123;</span><br><span class="line">            <span class="keyword">if</span> (<span class="built_in">this</span>.singletonsCurrentlyInDestruction) &#123;</span><br><span class="line">                <span class="comment">// 如果正在销毁单例，则抛异常</span></span><br><span class="line">                <span class="comment">// 注意：不要在销毁方法中调用获取 bean 方法</span></span><br><span class="line">            &#125;</span><br><span class="line">            <span class="comment">// 创建前，先注册到正在创建中的集合</span></span><br><span class="line">            <span class="comment">// 在出现循环引用时，第二次进入 doGetBean，用此作为判断标志</span></span><br><span class="line">            beforeSingletonCreation(beanName);</span><br><span class="line">            <span class="type">boolean</span> <span class="variable">newSingleton</span> <span class="operator">=</span> <span class="literal">false</span>;</span><br><span class="line">            <span class="comment">// ...</span></span><br><span class="line">            <span class="keyword">try</span> &#123;</span><br><span class="line">                <span class="comment">// 使用传入的单例工厂创建对象</span></span><br><span class="line">                singletonObject = singletonFactory.getObject();</span><br><span class="line">                newSingleton = <span class="literal">true</span>;</span><br><span class="line">            &#125;</span><br><span class="line">            <span class="keyword">catch</span> (IllegalStateException ex) &#123;</span><br><span class="line">                <span class="comment">// 如果异常的出现是因为 bean 被创建了，就忽略异常，否则抛出异常</span></span><br><span class="line">                singletonObject = <span class="built_in">this</span>.singletonObjects.get(beanName);</span><br><span class="line">                <span class="keyword">if</span> (singletonObject == <span class="literal">null</span>) &#123;</span><br><span class="line">                    <span class="keyword">throw</span> ex;</span><br><span class="line">                &#125;</span><br><span class="line">            &#125;</span><br><span class="line">            <span class="keyword">catch</span> (BeanCreationException ex) &#123;</span><br><span class="line">                <span class="comment">// ...</span></span><br><span class="line">            &#125;</span><br><span class="line">            <span class="keyword">finally</span> &#123;</span><br><span class="line">                <span class="comment">// ...</span></span><br><span class="line">                <span class="comment">// 创建后，从正在创建中集合移除</span></span><br><span class="line">                afterSingletonCreation(beanName);</span><br><span class="line">            &#125;</span><br><span class="line">            <span class="keyword">if</span> (newSingleton) &#123;</span><br><span class="line">                <span class="comment">// 添加单例到缓存</span></span><br><span class="line">                addSingleton(beanName, singletonObject);</span><br><span class="line">            &#125;</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="keyword">return</span> (singletonObject != NULL_OBJECT ? singletonObject : <span class="literal">null</span>);</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<h2 id="创建-Bean"><a href="#创建-Bean" class="headerlink" title="创建 Bean"></a>创建 Bean</h2><p>createBean 是创建 Bean 的入口方法，由 AbstractBeanFactory 定义，由 AbstractAutowireCapableBeanFactory 实现。</p>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">protected</span> Object <span class="title function_">createBean</span><span class="params">(String beanName, RootBeanDefinition mbd, Object[] args)</span> <span class="keyword">throws</span> BeanCreationException &#123;</span><br><span class="line">    <span class="comment">// ...</span></span><br><span class="line">    <span class="keyword">try</span> &#123;</span><br><span class="line">        <span class="comment">// 给 Bean 后置处理器一个返回代理的机会</span></span><br><span class="line">        <span class="type">Object</span> <span class="variable">bean</span> <span class="operator">=</span> resolveBeforeInstantiation(beanName, mbdToUse);</span><br><span class="line">        <span class="keyword">if</span> (bean != <span class="literal">null</span>) &#123;</span><br><span class="line">            <span class="keyword">return</span> bean;</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">    <span class="comment">// 常规的创建 Bean</span></span><br><span class="line">    <span class="type">Object</span> <span class="variable">beanInstance</span> <span class="operator">=</span> doCreateBean(beanName, mbdToUse, args);</span><br><span class="line">    <span class="keyword">return</span> beanInstance;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<h3 id="doCreateBean"><a href="#doCreateBean" class="headerlink" title="doCreateBean"></a>doCreateBean</h3><p>常规的创建 Bean 的具体工作是由 doCreateBean 完成的。</p>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">protected</span> Object <span class="title function_">doCreateBean</span><span class="params">(<span class="keyword">final</span> String beanName, <span class="keyword">final</span> RootBeanDefinition mbd, <span class="keyword">final</span> Object[] args)</span> <span class="keyword">throws</span> BeanCreationException &#123;</span><br><span class="line">    <span class="type">BeanWrapper</span> <span class="variable">instanceWrapper</span> <span class="operator">=</span> <span class="literal">null</span>;</span><br><span class="line">    <span class="keyword">if</span> (mbd.isSingleton()) &#123;</span><br><span class="line">        instanceWrapper = <span class="built_in">this</span>.factoryBeanInstanceCache.remove(beanName);</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="keyword">if</span> (instanceWrapper == <span class="literal">null</span>) &#123;</span><br><span class="line">        <span class="comment">// 使用相应的策略创建 bean 实例，例如通过工厂方法或者有参、无参构造器方法</span></span><br><span class="line">        instanceWrapper = createBeanInstance(beanName, mbd, args);</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="keyword">final</span> <span class="type">Object</span> <span class="variable">bean</span> <span class="operator">=</span> (instanceWrapper != <span class="literal">null</span> ? instanceWrapper.getWrappedInstance() : <span class="literal">null</span>);</span><br><span class="line">    Class&lt;?&gt; beanType = (instanceWrapper != <span class="literal">null</span> ? instanceWrapper.getWrappedClass() : <span class="literal">null</span>);</span><br><span class="line">    mbd.resolvedTargetType = beanType;</span><br><span class="line">    </span><br><span class="line">    <span class="comment">// ...</span></span><br><span class="line"></span><br><span class="line">    <span class="comment">// 使用 ObjectFactory 封装实例并缓存，以解决循环引用问题</span></span><br><span class="line">    <span class="type">boolean</span> <span class="variable">earlySingletonExposure</span> <span class="operator">=</span> (mbd.isSingleton() </span><br><span class="line">        &amp;&amp; <span class="built_in">this</span>.allowCircularReferences </span><br><span class="line">        &amp;&amp; isSingletonCurrentlyInCreation(beanName));</span><br><span class="line">    <span class="keyword">if</span> (earlySingletonExposure) &#123;</span><br><span class="line">        addSingletonFactory(beanName, <span class="keyword">new</span> <span class="title class_">ObjectFactory</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_">getObject</span><span class="params">()</span> <span class="keyword">throws</span> BeansException &#123;</span><br><span class="line">                <span class="keyword">return</span> getEarlyBeanReference(beanName, mbd, bean);</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="type">Object</span> <span class="variable">exposedObject</span> <span class="operator">=</span> bean;</span><br><span class="line">    <span class="keyword">try</span> &#123;</span><br><span class="line">        <span class="comment">// 填充属性（包括解析依赖的 bean）</span></span><br><span class="line">        populateBean(beanName, mbd, instanceWrapper);</span><br><span class="line">        <span class="keyword">if</span> (exposedObject != <span class="literal">null</span>) &#123;</span><br><span class="line">            <span class="comment">// 初始化 bean</span></span><br><span class="line">            exposedObject = initializeBean(beanName, exposedObject, mbd);</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"></span><br><span class="line">    <span class="comment">// 如有需要，将 bean 注册为一次性的，以供 beanFactory 在关闭时调用销毁方法</span></span><br><span class="line">    <span class="keyword">try</span> &#123;</span><br><span class="line">        registerDisposableBeanIfNecessary(beanName, bean, mbd);</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="comment">// ...</span></span><br><span class="line"></span><br><span class="line">    <span class="keyword">return</span> exposedObject;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<h4 id="createBeanInstance"><a href="#createBeanInstance" class="headerlink" title="createBeanInstance"></a>createBeanInstance</h4><p>创建 Bean 实例，并使用 BeanWrapper 封装。实例化的方式：</p>
 <ol>
-<li>第一次遇到某一个字符串字面量时，会在字符串常量池中创建一个 String 对象，以后遇到相同的字符串字面量，就复用该对象，不再重复创建。</li>
-<li>每一次 new 都会创建一个新的 String 对象。</li>
+<li>工厂方法</li>
+<li>构造器方法<ol>
+<li>有参</li>
+<li>无参</li>
 </ol>
-<p>ps: 以上的“遇到某一个字符串字面量”就是很纯粹地指代程序的源代码中出现用双引号括起来的字符串字面量。</p>
-<h3 id="进入字符串常量池的两种情况"><a href="#进入字符串常量池的两种情况" class="headerlink" title="进入字符串常量池的两种情况"></a>进入字符串常量池的两种情况</h3><p>因此，<strong>如果字符串常量池中没有值为 “abc” 的 String 对象</strong>，<code>new String(&quot;abc&quot;)</code> 语句将涉及两个 String 对象的创建，第一个是因为括号里的 “abc” 而在字符串常量池中生成的，第二个才是 new 关键字在堆中创建的；否则只会涉及一个 String 对象的创建。<br>为什么上面改用<strong>如果字符串常量池中没有值为 “abc” 的 String 对象</strong>呢？这是因为，字符串常量池里保留的 String 对象有两种产生来源：</p>
-<ol>
-<li>因为第一次遇到字符串字面量而生成的字符串对象。</li>
-<li>使用 <code>java.lang.String#intern</code> 主动地尝试将字符串对象放入字符串常量池。</li>
+</li>
 </ol>
-<h2 id="常量池的分类"><a href="#常量池的分类" class="headerlink" title="常量池的分类"></a>常量池的分类</h2><ol>
-<li>Class 文件中的常量池(Constant Pool)</li>
-<li>运行时常量池(Runtime Constant Pool)</li>
-<li>字符串常量池</li>
+<h4 id="populateBean"><a href="#populateBean" class="headerlink" title="populateBean"></a>populateBean</h4><p>为创建出的实例填充属性，包括解析当前 bean 所依赖的 bean。</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_">populateBean</span><span class="params">(String beanName, RootBeanDefinition mbd, BeanWrapper bw)</span> &#123;</span><br><span class="line">    <span class="type">PropertyValues</span> <span class="variable">pvs</span> <span class="operator">=</span> mbd.getPropertyValues();</span><br><span class="line">    <span class="comment">// ...</span></span><br><span class="line">    </span><br><span class="line">    <span class="comment">// 给 InstantiationAwareBeanPostProcessors 一个机会，</span></span><br><span class="line">    <span class="comment">// 在设置 bean 属性前修改 bean 状态，可用于自定义的字段注入</span></span><br><span class="line">    <span class="type">boolean</span> <span class="variable">continueWithPropertyPopulation</span> <span class="operator">=</span> <span class="literal">true</span>;</span><br><span class="line">    <span class="keyword">if</span> (!mbd.isSynthetic() &amp;&amp; hasInstantiationAwareBeanPostProcessors()) &#123;</span><br><span class="line">        <span class="keyword">for</span> (BeanPostProcessor bp : getBeanPostProcessors()) &#123;</span><br><span class="line">            <span class="keyword">if</span> (bp <span class="keyword">instanceof</span> InstantiationAwareBeanPostProcessor) &#123;</span><br><span class="line">                <span class="type">InstantiationAwareBeanPostProcessor</span> <span class="variable">ibp</span> <span class="operator">=</span> (InstantiationAwareBeanPostProcessor) bp;</span><br><span class="line">                <span class="keyword">if</span> (!ibp.postProcessAfterInstantiation(bw.getWrappedInstance(), beanName)) &#123;</span><br><span class="line">                    continueWithPropertyPopulation = <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">    &#125;</span><br><span class="line">    </span><br><span class="line">    <span class="comment">// 是否继续填充属性的流程</span></span><br><span class="line">    <span class="keyword">if</span> (!continueWithPropertyPopulation) &#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="keyword">if</span> (mbd.getResolvedAutowireMode() == RootBeanDefinition.AUTOWIRE_BY_NAME</span><br><span class="line">        || mbd.getResolvedAutowireMode() == RootBeanDefinition.AUTOWIRE_BY_TYPE) &#123;</span><br><span class="line">        <span class="type">MutablePropertyValues</span> <span class="variable">newPvs</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">MutablePropertyValues</span>(pvs);</span><br><span class="line">        <span class="comment">// 根据名称注入</span></span><br><span class="line">        <span class="keyword">if</span> (mbd.getResolvedAutowireMode() == RootBeanDefinition.AUTOWIRE_BY_NAME) &#123;</span><br><span class="line">            autowireByName(beanName, mbd, bw, newPvs);</span><br><span class="line">        &#125;</span><br><span class="line">        </span><br><span class="line">        <span class="comment">// 根据类型注入</span></span><br><span class="line">        <span class="keyword">if</span> (mbd.getResolvedAutowireMode() == RootBeanDefinition.AUTOWIRE_BY_TYPE) &#123;</span><br><span class="line">            autowireByType(beanName, mbd, bw, newPvs);</span><br><span class="line">        &#125;</span><br><span class="line">        pvs = newPvs;</span><br><span class="line">    &#125;</span><br><span class="line">    </span><br><span class="line">    <span class="comment">// 是否存在 InstantiationAwareBeanPostProcessors</span></span><br><span class="line">    <span class="type">boolean</span> <span class="variable">hasInstAwareBpps</span> <span class="operator">=</span> hasInstantiationAwareBeanPostProcessors();</span><br><span class="line">    <span class="comment">// 是否需要检查依赖</span></span><br><span class="line">    <span class="type">boolean</span> <span class="variable">needsDepCheck</span> <span class="operator">=</span> (mbd.getDependencyCheck() != RootBeanDefinition.DEPENDENCY_CHECK_NONE);</span><br><span class="line">    </span><br><span class="line">    <span class="keyword">if</span> (hasInstAwareBpps || needsDepCheck) &#123;</span><br><span class="line">        PropertyDescriptor[] filteredPds = filterPropertyDescriptorsForDependencyCheck(bw, mbd.allowCaching);</span><br><span class="line">        <span class="keyword">if</span> (hasInstAwareBpps) &#123;</span><br><span class="line">            <span class="comment">// 后置处理 PropertyValues</span></span><br><span class="line">            <span class="keyword">for</span> (BeanPostProcessor bp : getBeanPostProcessors()) &#123;</span><br><span class="line">                <span class="keyword">if</span> (bp <span class="keyword">instanceof</span> InstantiationAwareBeanPostProcessor) &#123;</span><br><span class="line">                    <span class="type">InstantiationAwareBeanPostProcessor</span> <span class="variable">ibp</span> <span class="operator">=</span> (InstantiationAwareBeanPostProcessor) bp;</span><br><span class="line">                    pvs = ibp.postProcessPropertyValues(pvs, filteredPds, bw.getWrappedInstance(), beanName);</span><br><span class="line">                    <span class="keyword">if</span> (pvs == <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">                &#125;   </span><br><span class="line">            &#125;</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="keyword">if</span> (needsDepCheck) &#123;</span><br><span class="line">            checkDependencies(beanName, mbd, filteredPds, pvs);</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="comment">// 将属性应用到 bean 上（常规情况下，前面的处理都用不上）</span></span><br><span class="line">    applyPropertyValues(beanName, mbd, bw, pvs);</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<h4 id="initializeBean"><a href="#initializeBean" class="headerlink" title="initializeBean"></a>initializeBean</h4><p>在填充完属性后，实例就可以进行初始化工作：</p>
+<ol>
+<li>invokeAwareMethods，让 Bean 通过 xxxAware 接口感知一些信息</li>
+<li>调用 BeanPostProcessor 的 postProcessBeforeInitialization 方法</li>
+<li>invokeInitMethods，调用初始化方法</li>
+<li>调用 BeanPostProcessor 的 postProcessAfterInitialization 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">class</span> <span class="title class_">StringTableTest_1</span> &#123;  </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">String</span> <span class="variable">s1</span> <span class="operator">=</span> <span class="string">&quot;a&quot;</span>;  </span><br><span class="line">        <span class="type">String</span> <span class="variable">s2</span> <span class="operator">=</span> <span class="string">&quot;b&quot;</span>;  </span><br><span class="line">        <span class="type">String</span> <span class="variable">s3</span> <span class="operator">=</span> <span class="string">&quot;ab&quot;</span>;  </span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
-<p>使用 <code>javap -v .\StringTableTest_1.class</code> 进行反编译，摘取重要部分：</p>
-<figure class="highlight console"><table><tr><td class="code"><pre><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.#24         // 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 = String             <span class="comment">#25            // a</span></span></span><br><span class="line"><span class="meta prompt_">   #</span><span class="language-bash">3 = String             <span class="comment">#26            // b</span></span></span><br><span class="line"><span class="meta prompt_">   #</span><span class="language-bash">4 = String             <span class="comment">#27            // ab</span></span></span><br><span class="line"><span class="meta prompt_"></span></span><br><span class="line"><span class="meta prompt_">  #</span><span class="language-bash">25 = Utf8               a</span></span><br><span class="line"><span class="meta prompt_">  #</span><span class="language-bash">26 = Utf8               b</span></span><br><span class="line"><span class="meta prompt_">  #</span><span class="language-bash">27 = Utf8               ab</span></span><br><span class="line"></span><br><span class="line"></span><br><span class="line"></span><br><span class="line">0: ldc           #2                  // String a</span><br><span class="line">2: astore_1</span><br><span class="line">3: ldc           #3                  // String b</span><br><span class="line">5: astore_2</span><br><span class="line">6: ldc           #4                  // String ab</span><br><span class="line">8: astore_3</span><br><span class="line">9: return</span><br></pre></td></tr></table></figure>
-<ul>
-<li>Class 文件中的常量池 Constant pool 会记录代码中出现的字面量（文本文件）。</li>
-<li>运行时常量池是方法区的一部分，Class 文件中的常量池的内容，在类加载后，就进入了运行时常量池中（内存中的数据）。</li>
-<li>字符串常量池，记录 interned string 的一个全局表，JDK 6 前在方法区，后移到堆中。</li>
-</ul>
-<h2 id="字符串常量池的位置和形式"><a href="#字符串常量池的位置和形式" class="headerlink" title="字符串常量池的位置和形式"></a>字符串常量池的位置和形式</h2><p>在《深入理解Java虚拟机》提到：字符串常量池的位置从 JDK 7 开始，从永久代中移到了堆中。在这句话中，字符串常量池像是一个特定的内存区域，存储了 interned string 的实例。</p>
-<img src="/2023/11/03/testing-and-analysis-of-StringTable/Pasted%20image%2020231103113047.png" class="" title="字符串常量池的位置">
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">protected</span> Object <span class="title function_">initializeBean</span><span class="params">(<span class="keyword">final</span> String beanName, <span class="keyword">final</span> Object bean, RootBeanDefinition mbd)</span> &#123;</span><br><span class="line">    <span class="comment">// 处理 Aware 接口的相应方法</span></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">                invokeAwareMethods(beanName, bean);</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">        invokeAwareMethods(beanName, bean);</span><br><span class="line">    &#125;</span><br><span class="line">    </span><br><span class="line">    <span class="comment">// 应用 BeanPostProcessor 的 postProcessBeforeInitialization 方法</span></span><br><span class="line">    <span class="type">Object</span> <span class="variable">wrappedBean</span> <span class="operator">=</span> bean;</span><br><span class="line">    <span class="keyword">if</span> (mbd == <span class="literal">null</span> || !mbd.isSynthetic()) &#123;</span><br><span class="line">        wrappedBean = applyBeanPostProcessorsBeforeInitialization(wrappedBean, beanName);</span><br><span class="line">    &#125;</span><br><span class="line">    </span><br><span class="line">    <span class="keyword">try</span> &#123;</span><br><span class="line">        <span class="comment">// 调用初始化方法</span></span><br><span class="line">        invokeInitMethods(beanName, wrappedBean, mbd);</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_">BeanCreationException</span>(</span><br><span class="line">            (mbd != <span class="literal">null</span> ? mbd.getResourceDescription() : <span class="literal">null</span>),</span><br><span class="line">            beanName, <span class="string">&quot;Invocation of init method failed&quot;</span>, ex);</span><br><span class="line">    &#125;</span><br><span class="line">    </span><br><span class="line">    <span class="keyword">if</span> (mbd == <span class="literal">null</span> || !mbd.isSynthetic()) &#123;</span><br><span class="line">        <span class="comment">// 应用 BeanPostProcessor 的 postProcessAfterInitialization 方法</span></span><br><span class="line">        wrappedBean = applyBeanPostProcessorsAfterInitialization(wrappedBean, beanName);</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="keyword">return</span> wrappedBean;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
 
-<h3 id="验证字符串常量池的位置"><a href="#验证字符串常量池的位置" class="headerlink" title="验证字符串常量池的位置"></a>验证字符串常量池的位置</h3><p>书中使用了以下方式来验证字符串常量池的位置。</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_">StringTableTest_8</span> &#123;  </span><br><span class="line">  </span><br><span class="line">    <span class="comment">// JDK 1.8 设置 -Xmx10m -XX:-UseGCOverheadLimit    </span></span><br><span class="line">    <span class="comment">// JDK 1.6 设置 -XX:MaxPerSize=10m</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">        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">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">for</span> (<span class="type">int</span> <span class="variable">j</span> <span class="operator">=</span> <span class="number">0</span>; j &lt; <span class="number">260000</span>; j++) &#123;  </span><br><span class="line">                list.add(String.valueOf(j).intern());  </span><br><span class="line">                i++;  </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">            e.printStackTrace();  </span><br><span class="line">        &#125; <span class="keyword">finally</span> &#123;  </span><br><span class="line">            System.out.println(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>
-<p>在 JDK 8 中异常如下：</p>
-<figure class="highlight console"><table><tr><td class="code"><pre><span class="line">Exception in thread &quot;main&quot; java.lang.OutOfMemoryError: Java heap space</span><br></pre></td></tr></table></figure>
-<p>在 JDK 6 中异常如下：</p>
-<figure class="highlight console"><table><tr><td class="code"><pre><span class="line">java.lang.OutOfMemoryError: PermGen space</span><br></pre></td></tr></table></figure>
+<h5 id="处理-Aware-接口的相应方法"><a href="#处理-Aware-接口的相应方法" class="headerlink" title="处理 Aware 接口的相应方法"></a>处理 Aware 接口的相应方法</h5><p>让 Bean 在初始化中，感知（获知）和自身相关的资源，如 beanName、beanClassLoader 或者 beanFactory。</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_">invokeAwareMethods</span><span class="params">(<span class="keyword">final</span> String beanName, <span class="keyword">final</span> Object bean)</span> &#123;</span><br><span class="line">    <span class="keyword">if</span> (bean <span class="keyword">instanceof</span> Aware) &#123;</span><br><span class="line">        <span class="keyword">if</span> (bean <span class="keyword">instanceof</span> BeanNameAware) &#123;</span><br><span class="line">            ((BeanNameAware) bean).setBeanName(beanName);</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="keyword">if</span> (bean <span class="keyword">instanceof</span> BeanClassLoaderAware) &#123;</span><br><span class="line">            ((BeanClassLoaderAware) bean).setBeanClassLoader(getBeanClassLoader());</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="keyword">if</span> (bean <span class="keyword">instanceof</span> BeanFactoryAware) &#123;</span><br><span class="line">            ((BeanFactoryAware) bean).setBeanFactory(AbstractAutowireCapableBeanFactory.<span class="built_in">this</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>同时书中也提到了，在字符串常量池的位置改变后，它只用保存第一次出现时字符串对象的引用。JDK 8 中的 intern 方法可以印证该说法，方法注释中提到：如果字符串常量池中已存在相等(equals)的字符串，那就返回已存在的对象（这样原先准备加入的对象就可以释放）；否则，将字符串对象加入字符串常量池中，直接返回对该对象的引用（不用像 JDK 6 时，复制一个对象加入常量池，返回该复制对象的引用）。</p>
-<h3 id="关于-intern-的实验"><a href="#关于-intern-的实验" class="headerlink" title="关于 intern 的实验"></a>关于 intern 的实验</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_">StringTableTest_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> &#123;  </span><br><span class="line">        <span class="comment">// &quot;a&quot;、&quot;b&quot; 作为字符串字面量，会解析得到字符串对象放入字符串常量池      </span></span><br><span class="line">        <span class="comment">// 但是 new String(&quot;a&quot;) 创建出来的字符串对象，不会进入字符串常量池        </span></span><br><span class="line">        <span class="type">String</span> <span class="variable">s1</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">String</span>(<span class="string">&quot;a&quot;</span>) + <span class="keyword">new</span> <span class="title class_">String</span>(<span class="string">&quot;b&quot;</span>);  </span><br><span class="line">        <span class="comment">// intern 方法尝试将 s1 放入 StringTable，无则放入，返回该对象引用，有则返回已存在对象的引用  </span></span><br><span class="line">        <span class="type">String</span> <span class="variable">s2</span> <span class="operator">=</span> s1.intern();  </span><br><span class="line">  </span><br><span class="line">        <span class="type">String</span> <span class="variable">x</span> <span class="operator">=</span> <span class="string">&quot;ab&quot;</span>;  </span><br><span class="line">  </span><br><span class="line">		System.out.println(s2 == x);  </span><br><span class="line">		System.out.println(s1 == x); </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_">StringTableTest_6</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="comment">// 将 &quot;ab&quot; 的赋值语句提前到最开始，&quot;ab&quot; 生成的字符串对象进入字符串常量池       </span></span><br><span class="line">        <span class="type">String</span> <span class="variable">x</span> <span class="operator">=</span> <span class="string">&quot;ab&quot;</span>;  </span><br><span class="line">        <span class="type">String</span> <span class="variable">s1</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">String</span>(<span class="string">&quot;a&quot;</span>) + <span class="keyword">new</span> <span class="title class_">String</span>(<span class="string">&quot;b&quot;</span>);  </span><br><span class="line">        <span class="comment">// intern 方法尝试将 s1 放入 StringTable，无则放入，返回该对象引用，有则返回已存在对象的引用  </span></span><br><span class="line">        <span class="type">String</span> <span class="variable">s2</span> <span class="operator">=</span> s1.intern();  </span><br><span class="line">  </span><br><span class="line">        System.out.println(s2 == x);  </span><br><span class="line">        System.out.println(s1 == x);  </span><br><span class="line">    &#125;  </span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
-<p>实验结果证实了上述说法。</p>
-<h3 id="字符串常量池到底是什么？"><a href="#字符串常量池到底是什么？" class="headerlink" title="字符串常量池到底是什么？"></a>字符串常量池到底是什么？</h3><p>但是 <a href="https://www.zhihu.com/people/logirl.cc">xinxi</a> 提及：字符串常量池，也称为 StringTable，本质上是一个惰性维护的哈希表，是一个纯运行时的结构，只存储对 <code>java.lang.String</code> 实例的引用，而不存储 String 对象的内容。当我们提到一个字符串进入字符串常量池其实是说在这个 StringTable 中保存了对它的引用，反之，如果说没有在其中就是说 StringTable 中没有对它的引用。<br><a href="https://blog.csdn.net/zyplanke">zyplanke</a> 分析 StringTable 在内存中的形式时，也表达了类似的观点。</p>
-<img src="/2023/11/03/testing-and-analysis-of-StringTable/Pasted%20image%2020231103194544.png" class="" title="StringTable 的内存形式">
+<h5 id="调用初始化方法"><a href="#调用初始化方法" class="headerlink" title="调用初始化方法"></a>调用初始化方法</h5><ol>
+<li>如果 bean 实现 InitializingBean 接口，调用 afterPropertiesSet 方法</li>
+<li>如果自定义 init 方法且满足调用条件，同样进行调用</li>
+</ol>
+<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_">invokeInitMethods</span><span class="params">(String beanName, <span class="keyword">final</span> Object bean, RootBeanDefinition mbd)</span> <span class="keyword">throws</span> Throwable &#123;</span><br><span class="line">    <span class="comment">// 是否实现 InitializingBean 接口，是的话调用 afterPropertiesSet 方法</span></span><br><span class="line">    <span class="comment">// 给 bean 一个感知属性已设置并做出反应的机会</span></span><br><span class="line">    <span class="type">boolean</span> <span class="variable">isInitializingBean</span> <span class="operator">=</span> (bean <span class="keyword">instanceof</span> InitializingBean);</span><br><span class="line">    <span class="keyword">if</span> (isInitializingBean</span><br><span class="line">        &amp;&amp; (mbd == <span class="literal">null</span> || !mbd.isExternallyManagedInitMethod(<span class="string">&quot;afterPropertiesSet&quot;</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">            <span class="keyword">try</span> &#123;</span><br><span class="line">                AccessController.doPrivileged(<span class="keyword">new</span> <span class="title class_">PrivilegedExceptionAction</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> <span class="keyword">throws</span> Exception &#123;</span><br><span class="line">                        ((InitializingBean) bean).afterPropertiesSet();</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">catch</span> (PrivilegedActionException pae) &#123;</span><br><span class="line">                <span class="keyword">throw</span> pae.getException();</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">            ((InitializingBean) bean).afterPropertiesSet();</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">// 如果存在自定义的 init 方法且方法名称不是 afterPropertiesSet，判断是否调用</span></span><br><span class="line">    <span class="keyword">if</span> (mbd != <span class="literal">null</span>) &#123;</span><br><span class="line">        <span class="type">String</span> <span class="variable">initMethodName</span> <span class="operator">=</span> mbd.getInitMethodName();</span><br><span class="line">        <span class="keyword">if</span> (initMethodName != <span class="literal">null</span></span><br><span class="line">            &amp;&amp; !(isInitializingBean &amp;&amp; <span class="string">&quot;afterPropertiesSet&quot;</span>.equals(initMethodName))</span><br><span class="line">            &amp;&amp; !mbd.isExternallyManagedInitMethod(initMethodName)) &#123;</span><br><span class="line">            invokeCustomInitMethod(beanName, bean, mbd);</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>尽管这个疑问似乎不妨碍我们理解很多东西，但是深究之后，真的让人困惑，网上也没有搜集到更多的信息。字符串常量池和 StringTable 是否等价？字符串常量池更准确的说法是否是“一个保存引用的 StringTable 加上分布在堆（JDK 6 以前的永久代）中的字符串实例”？<br>已经好几次打开 jvm 的源码，却看不懂它到底什么意思啊！！！！！难道是时候开始学 C++ 了吗。</p>
-<h2 id="进入字符串常量池的时机"><a href="#进入字符串常量池的时机" class="headerlink" title="进入字符串常量池的时机"></a>进入字符串常量池的时机</h2><p>前面提到了第一次遇到的字符串字面量会在某一个时刻，生成对应的字符串对象进入字符串常量池，同时也提到了，字符串常量池（StringTable）的维护是懒惰的，那么这些究竟是什么时候发生的呢？</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_">StringTableTest_12</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> IOException &#123;</span><br><span class="line">        <span class="keyword">new</span> <span class="title class_">String</span>(<span class="string">&quot;ab&quot;</span>);</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+<h5 id="BeanPostProcessor-处理"><a href="#BeanPostProcessor-处理" class="headerlink" title="BeanPostProcessor 处理"></a>BeanPostProcessor 处理</h5><p>在调用初始化方法前后，BeanPostProcessor 先后进行两次处理。其实和 BeanPostProcessor 相关的代码都非常相似：</p>
+<ol>
+<li>获取 Processor 列表</li>
+<li>判断 Processor 类型是否是当前需要的</li>
+<li>对 bean 进行处理</li>
+</ol>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> Object <span class="title function_">applyBeanPostProcessorsBeforeInitialization</span><span class="params">(Object existingBean, String beanName)</span> <span class="keyword">throws</span> BeansException &#123;</span><br><span class="line"></span><br><span class="line">    <span class="type">Object</span> <span class="variable">result</span> <span class="operator">=</span> existingBean;</span><br><span class="line">    <span class="keyword">for</span> (BeanPostProcessor beanProcessor : getBeanPostProcessors()) &#123;</span><br><span class="line">        result = beanProcessor.postProcessBeforeInitialization(result, beanName);</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">    <span class="keyword">return</span> result;</span><br><span class="line">&#125;</span><br><span class="line"></span><br><span class="line"><span class="keyword">public</span> Object <span class="title function_">applyBeanPostProcessorsAfterInitialization</span><span class="params">(Object existingBean, String beanName)</span> <span class="keyword">throws</span> BeansException &#123;</span><br><span class="line"></span><br><span class="line">    <span class="type">Object</span> <span class="variable">result</span> <span class="operator">=</span> existingBean;</span><br><span class="line">    <span class="keyword">for</span> (BeanPostProcessor beanProcessor : getBeanPostProcessors()) &#123;</span><br><span class="line">        result = beanProcessor.postProcessAfterInitialization(result, beanName);</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">    <span class="keyword">return</span> result;</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"> 0: new           #2                  // class java/lang/String</span><br><span class="line"> 3: dup</span><br><span class="line"> 4: ldc           #3                  // String ab</span><br><span class="line"> 6: invokespecial #4                  // Method java/lang/String.&quot;&lt;init&gt;&quot;:(Ljava/lang/String;)V</span><br><span class="line"> 9: pop</span><br><span class="line">10: return</span><br></pre></td></tr></table></figure>
+<h4 id="再思-Bean-的初始化"><a href="#再思-Bean-的初始化" class="headerlink" title="再思 Bean 的初始化"></a>再思 Bean 的初始化</h4><p>以下代码片段一度让我困惑，从注释看，初始化 Bean 实例的工作包括了 populateBean 和 initializeBean，但是 initializeBean 方法的含义就是初始化 Bean。在 initializeBean 方法中，调用了 invokeInitMethods 方法，其含义仍然是调用初始化方法。<br>在更熟悉代码后，我有一种微妙的、个人性的体会，在 Spring 源码中，有时候视角的变化是很快的，痕迹是很小的。如果不加以理解和区分，很容易迷失在相似的描述中。以此处为例，“初始化 Bean 和 Bean 的初始化”扩展开来是 “Bean 工厂初始化一个 Bean 和 Bean 自身进行初始化”。</p>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="comment">// Initialize the bean instance.</span></span><br><span class="line"><span class="type">Object</span> <span class="variable">exposedObject</span> <span class="operator">=</span> bean;</span><br><span class="line"><span class="keyword">try</span> &#123;</span><br><span class="line">    populateBean(beanName, mbd, instanceWrapper);</span><br><span class="line">    <span class="keyword">if</span> (exposedObject != <span class="literal">null</span>) &#123;</span><br><span class="line">        exposedObject = initializeBean(beanName, exposedObject, mbd);</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
 
-<p><a href="https://www.zhihu.com/people/rednaxelafx">RednaxelaFX</a> 的文章提到：</p>
-<blockquote>
-<p>在类加载阶段，JVM 会在堆中创建对应这些 class 文件常量池中的字符串对象实例，并在字符串常量池中驻留其引用。具体在 resolve 阶段执行。这些常量全局共享。</p>
-</blockquote>
-<p><a href="https://www.zhihu.com/people/logirl.cc">xinxi</a> 的文章中补充到：</p>
-<blockquote>
-<p>这里说的比较笼统，没错，是 resolve 阶段，但是并不是大家想的那样，立即就创建对象并且在字符串常量池中驻留了引用。 <strong>JVM规范里明确指定resolve阶段可以是lazy的。</strong><br>……<br>就 HotSpot VM 的实现来说，加载类的时候，那些字符串字面量会进入到当前类的运行时常量池，不会进入全局的字符串常量池（即在 StringTable 中并没有相应的引用，在堆中也没有对应的对象产生）。</p>
-</blockquote>
-<p>《深入理解Java虚拟机》中提到：</p>
-<blockquote>
-<p>《Java虚拟机规范》之中并未规定解析阶段发生的具体时间，只要求了在执行ane-warray、checkcast、getfield、getstatic、instanceof、invokedynamic、invokeinterface、invoke-special、invokestatic、invokevirtual、ldc、ldc_w、ldc2_w、multianewarray、new、putfield和putstatic这17个用于操作符号引用的字节码指令之前，先对它们所使用的符号引用进行解析。所以虚拟机实现可以根据需要来自行判断，到底是在类被加载器加载时就对常量池中的符号引用进行解析，还是等到一个符号引用将要被使用前才去解析它。</p>
-</blockquote>
-<p>综上可知，字符串字面量的解析是属于类加载的解析阶段，但是《Java虚拟机规范》并未规定解析发生的具体时间，只要求在执行一些字节码指令前进行，其中包括了 ldc 指令。虚拟机的具体实现，比如 Hotspot 就在执行 <code>ldc #indexNumber</code> 前触发解析，根据字符串常量池中是否已存在字符串对象决定是否创建对象，并将对象推送到栈顶。<br>这也证实了前文中提到的字符串字面量生成字符串对象和 new 关键字无关。</p>
-<h3 id="验证延迟实例化"><a href="#验证延迟实例化" class="headerlink" title="验证延迟实例化"></a>验证延迟实例化</h3><p>使用 IDEA memory 功能，观察字符串对象的个数逐个变化。</p>
+<p>在注释这一行，视角是属于 BeanFactory（AbstractAutowireCapableBeanFactory）。从工厂的视角，面对一个刚刚创建出来的 Bean 实例，需要完成两方面的工作：</p>
 <ol>
-<li>直到第一次运行到字符串字面量时，才会创建对应的字符串对象。</li>
-<li>相同的字符串常量，不会重复创建字符串对象。</li>
+<li>为 Bean 实例填充属性，包括解析依赖，为 Bean 自身的初始化做好准备。</li>
+<li>Bean 自身的初始化。</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_">StringTableTest_4</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><br><span class="line">         </span><br><span class="line">        System.out.println(<span class="string">&quot;1&quot;</span>);  </span><br><span class="line">        System.out.println(<span class="string">&quot;2&quot;</span>);  </span><br><span class="line">        System.out.println(<span class="string">&quot;3&quot;</span>);  </span><br><span class="line">        System.out.println(<span class="string">&quot;4&quot;</span>);  </span><br><span class="line">        System.out.println(<span class="string">&quot;5&quot;</span>);  </span><br><span class="line">        System.out.println(<span class="string">&quot;6&quot;</span>);  </span><br><span class="line">        System.out.println(<span class="string">&quot;7&quot;</span>);  </span><br><span class="line">        System.out.println(<span class="string">&quot;8&quot;</span>);  </span><br><span class="line">        System.out.println(<span class="string">&quot;9&quot;</span>);  </span><br><span class="line">        System.out.println(<span class="string">&quot;0&quot;</span>);  </span><br><span class="line">        System.out.println(<span class="string">&quot;1&quot;</span>);  </span><br><span class="line">        System.out.println(<span class="string">&quot;2&quot;</span>);  </span><br><span class="line">        System.out.println(<span class="string">&quot;3&quot;</span>);  </span><br><span class="line">        System.out.println(<span class="string">&quot;4&quot;</span>);  </span><br><span class="line">        System.out.println(<span class="string">&quot;5&quot;</span>);  </span><br><span class="line">        System.out.println(<span class="string">&quot;6&quot;</span>);  </span><br><span class="line">        System.out.println(<span class="string">&quot;7&quot;</span>);  </span><br><span class="line">        System.out.println(<span class="string">&quot;8&quot;</span>);  </span><br><span class="line">        System.out.println(<span class="string">&quot;9&quot;</span>);  </span><br><span class="line">        System.out.println(<span class="string">&quot;0&quot;</span>);  </span><br><span class="line">    &#125;  </span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+<p>在万事俱备之后，就是 Bean 自身的初始化工作。由于 Spring 的高度扩展性，这部分并不只是单纯地调用初始化方法，还包含 Aware 接口和 BeanPostProcessor 的相关处理，前者偏属于 Java 对象层面，后者偏属于 Spring Bean 层面。<br>在认同 BeanPostProcessor 的处理属于 Bean 自身初始化工作的一部分后，@PostConstruct 注解的方法被称为 Bean 的初始化方法也就不那么违和了，因为它的实现原理正是 BeanPostProcessor，这仍然在 initializeBean 的范围内。</p>
+]]></content>
+      <tags>
+        <tag>java</tag>
+        <tag>spring</tag>
+      </tags>
+  </entry>
+  <entry>
+    <title>JVM GC 的测试和分析</title>
+    <url>/2023/11/01/testing-and-analysis-of-jvm-gc/</url>
+    <content><![CDATA[<h3 id="堆的组成"><a href="#堆的组成" class="headerlink" title="堆的组成"></a>堆的组成</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_">JvmGcTest_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">final</span> <span class="type">int</span> <span class="variable">_512KB</span> <span class="operator">=</span> <span class="number">512</span> * <span class="number">1024</span>;</span><br><span class="line">    <span class="keyword">public</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 class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">final</span> <span class="type">int</span> <span class="variable">_6MB</span> <span class="operator">=</span> <span class="number">6</span> * <span class="number">1024</span> * <span class="number">1024</span>;</span><br><span class="line">    <span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">final</span> <span class="type">int</span> <span class="variable">_7MB</span> <span class="operator">=</span> <span class="number">7</span> * <span class="number">1024</span> * <span class="number">1024</span>;</span><br><span class="line">    <span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">final</span> <span class="type">int</span> <span class="variable">_8MB</span> <span class="operator">=</span> <span class="number">8</span> * <span class="number">1024</span> * <span class="number">1024</span>;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// -Xms20M -Xmx20M -Xmn10M -XX:+UseSerialGC -XX:+PrintGCDetails -verbose:gc</span></span><br><span class="line">    <span class="comment">// -XX:+UseSerialGC 避免幸存区比例动态调整</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><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
 
-<img src="/2023/11/03/testing-and-analysis-of-StringTable/Pasted%20image%2020231102225445.png" class="" title="字符串字面量延迟实例化">
+<figure class="highlight console"><table><tr><td class="code"><pre><span class="line">Heap</span><br><span class="line"> def new generation   total 9216K, used 2010K [0x00000000fec00000, 0x00000000ff600000, 0x00000000ff600000)</span><br><span class="line">  eden space 8192K,  24% used [0x00000000fec00000, 0x00000000fedf68c8, 0x00000000ff400000)</span><br><span class="line">  from space 1024K,   0% used [0x00000000ff400000, 0x00000000ff400000, 0x00000000ff500000)</span><br><span class="line">  to   space 1024K,   0% used [0x00000000ff500000, 0x00000000ff500000, 0x00000000ff600000)</span><br><span class="line"> tenured generation   total 10240K, used 0K [0x00000000ff600000, 0x0000000100000000, 0x0000000100000000)</span><br><span class="line">   the space 10240K,   0% used [0x00000000ff600000, 0x00000000ff600000, 0x00000000ff600200, 0x0000000100000000)</span><br><span class="line"> Metaspace       used 3288K, capacity 4496K, committed 4864K, reserved 1056768K</span><br><span class="line">  class space    used 348K, capacity 388K, committed 512K, reserved 1048576K</span><br></pre></td></tr></table></figure>
 
-<h2 id="字符串常量池的垃圾回收和性能优化"><a href="#字符串常量池的垃圾回收和性能优化" class="headerlink" title="字符串常量池的垃圾回收和性能优化"></a>字符串常量池的垃圾回收和性能优化</h2><h3 id="垃圾回收"><a href="#垃圾回收" class="headerlink" title="垃圾回收"></a>垃圾回收</h3><p>前文提到字符串常量池在 JDK 7 开始移到堆中，是因为考虑在方法区中的垃圾回收是比较困难的，同时随着字节码技术的发展，CGLib 等会大量动态生成类的技术的运用使得方法区的内存紧张，将字符串常量池移到堆中，可以有效提高其垃圾回收效率。</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_">StringTableTest_9</span> &#123;  </span><br><span class="line">  </span><br><span class="line">    <span class="comment">// -Xmx10m -XX:+PrintStringTableStatistics -XX:+PrintGCDetails -verbose:gc  </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">            <span class="comment">// 0-&gt;100-&gt;10000，观察统计信息中数量的变化以及垃圾回收记录</span></span><br><span class="line">            <span class="keyword">for</span> (<span class="type">int</span> <span class="variable">j</span> <span class="operator">=</span> <span class="number">0</span>; j &lt; <span class="number">10000</span>; j++) &#123;  </span><br><span class="line">                String.valueOf(j).intern();  </span><br><span class="line">                i++;  </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">            e.printStackTrace();  </span><br><span class="line">        &#125; <span class="keyword">finally</span> &#123;  </span><br><span class="line">            System.out.println(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>
+<p>根据打印的信息，组成如下：</p>
+<ul>
+<li><code>Heap</code>: 堆。<ul>
+<li><code>def new generation</code>: 新生代。</li>
+<li><code>tenured generation</code>: 老年代。</li>
+<li><code>Metaspace</code>: 元空间，实际上并不属于堆， <code>-XX:+PrintGCDetails</code> 将它的信息一起输出。</li>
+</ul>
+</li>
+</ul>
+<h4 id="堆空间的比例"><a href="#堆空间的比例" class="headerlink" title="堆空间的比例"></a>堆空间的比例</h4><p>新生代中的空间占比 <code>eden:from:to</code> 在默认情况下是 <code>8:1:1</code>，与观察到的数据 <code>8192K:1024K:1024K</code> 一致。<br>新生代的空间 <code>eden + from + to</code> 为 10240K，符合 <code>-Xmn10M</code> 设置的大小。<br><code>total</code> 显示为 9216K，即 <code>eden + from</code> 的大小，是因为 <code>to</code> 的空间不计算在内。新生代可用的空间只有 <code>eden + from</code>，<code>to</code> 空间只是在使用标记-复制算法进行垃圾回收时使用。<br>老年代的空间为 10240K。<br>目前仅 <code>eden</code> 中已用 2010K，约占 <code>eden</code> 空间的 24%。</p>
+<h4 id="从内存地址分析堆空间"><a href="#从内存地址分析堆空间" class="headerlink" title="从内存地址分析堆空间"></a>从内存地址分析堆空间</h4><p>内存地址为 16 位的 16 进制的数字，64 位机器。<br><code>[0x00000000fec00000, 0x00000000ff600000, 0x00000000ff600000)</code> 分别表示地址空间的开始、已用、结束的地址指针。<br>新生代 <code>[0x00000000fec00000, 0x00000000ff600000)</code>，老年代 <code>[0x00000000ff600000, 0x0000000100000000)</code>，计算可得空间大小均为 10MB。<br><code>eden</code> 中已用的空间地址为 <code>[0x00000000fec00000, 0x00000000fedf68c8)</code>，空间大小为 2058440 byte，约等于 2010K。</p>
+<p>显而易见，新生代和老生代是一片完全连续的地址空间。</p>
+<h3 id="堆的垃圾回收"><a href="#堆的垃圾回收" class="headerlink" title="堆的垃圾回收"></a>堆的垃圾回收</h3><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> &#123;</span><br><span class="line">    List&lt;<span class="type">byte</span>[]&gt; list = <span class="keyword">new</span> <span class="title class_">ArrayList</span>&lt;&gt;();</span><br><span class="line">    list.add(<span class="keyword">new</span> <span class="title class_">byte</span>[_7MB]);</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">[GC (Allocation Failure) [DefNew: 2013K-&gt;721K(9216K), 0.0105099 secs] 2013K-&gt;721K(19456K), 0.0105455 secs] [Times: user=0.00 sys=0.00, real=0.01 secs] </span><br><span class="line">Heap</span><br><span class="line"> def new generation   total 9216K, used 8135K [0x00000000fec00000, 0x00000000ff600000, 0x00000000ff600000)</span><br><span class="line">  eden space 8192K,  90% used [0x00000000fec00000, 0x00000000ff33d8c0, 0x00000000ff400000)</span><br><span class="line">  from space 1024K,  70% used [0x00000000ff500000, 0x00000000ff5b45f0, 0x00000000ff600000)</span><br><span class="line">  to   space 1024K,   0% used [0x00000000ff400000, 0x00000000ff400000, 0x00000000ff500000)</span><br><span class="line"> tenured generation   total 10240K, used 0K [0x00000000ff600000, 0x0000000100000000, 0x0000000100000000)</span><br><span class="line">   the space 10240K,   0% used [0x00000000ff600000, 0x00000000ff600000, 0x00000000ff600200, 0x0000000100000000)</span><br><span class="line"> Metaspace       used 3354K, capacity 4496K, committed 4864K, reserved 1056768K</span><br><span class="line">  class space    used 360K, capacity 388K, committed 512K, reserved 1048576K</span><br></pre></td></tr></table></figure>
 
-<figure class="highlight console"><table><tr><td class="code"><pre><span class="line">[GC (Allocation Failure) [PSYoungGen: 2048K-&gt;488K(2560K)] 2048K-&gt;856K(9728K), 0.0007745 secs] [Times: user=0.00 sys=0.00, real=0.00 secs] </span><br><span class="line"></span><br><span class="line"></span><br><span class="line">StringTable statistics:</span><br><span class="line">Number of buckets       :     60013 =    480104 bytes, avg   8.000</span><br><span class="line">Number of entries       :      7277 =    174648 bytes, avg  24.000</span><br><span class="line">Number of literals      :      7277 =    421560 bytes, avg  57.930</span><br><span class="line">Total footprint         :           =   1076312 bytes</span><br><span class="line">Average bucket size     :     0.121</span><br><span class="line">Variance of bucket size :     0.125</span><br><span class="line">Std. dev. of bucket size:     0.354</span><br><span class="line">Maximum bucket size     :         3</span><br></pre></td></tr></table></figure>
+<p><code>Allocation Failure</code>，正常情况下，新对象总是分配在 Eden，分配空间失败，<code>eden</code> 的剩余空间不足以存放 7M 大小的对象，新生代发生 <code>minor GC</code>。<br><code>[DefNew: 2013K-&gt;721K(9216K), 0.0105099 secs]</code>，新生代在垃圾回收前后空间的占用变化和耗时。<br><code>2013K-&gt;721K(19456K), 0.0105455 secs</code>，整个堆在垃圾回收前后空间的占用变化和耗时。</p>
+<h4 id="GC-类型"><a href="#GC-类型" class="headerlink" title="GC 类型"></a>GC 类型</h4><ul>
+<li>GC: minor GC。</li>
+<li>Fulle GC: full GC。</li>
+</ul>
+<h4 id="from-和-to-的角色变换"><a href="#from-和-to-的角色变换" class="headerlink" title="from 和 to 的角色变换"></a>from 和 to 的角色变换</h4><p><code>from</code> 的已用空间的地址为 <code>[0x00000000ff500000, 0x00000000ff5b45f0)</code>，空间大小为 738800 byte，约 721K，与 GC 后的新生代空间占用大小一致。在垃圾回收后，<code>eden</code> 区域存活的对象全部转移到了原 <code>to</code> 空间，<code>from</code> 和 <code>to</code> 空间的角色相互转换（从地址空间的信息可以看到此时 <code>to</code> 的地址指针比 <code>from</code> 的地址指针小）。<br><code>eden</code> 的已用空间的地址为 <code>[0x00000000fec00000, 0x00000000ff33d8c0)</code>，空间大小为 7592128 byte，约 7.24M，比 7M 大不少。此时 <code>eden</code> 区域除了 <code>byte[]</code> 对象外，还存储了其他对象，比如为了创建 <code>List&lt;byte[]&gt;</code> 对象而新加载的类对象。</p>
+<h3 id="eden-空间足够时不发生-GC"><a href="#eden-空间足够时不发生-GC" class="headerlink" title="eden 空间足够时不发生 GC"></a>eden 空间足够时不发生 GC</h3><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> &#123;</span><br><span class="line">    List&lt;<span class="type">byte</span>[]&gt; list = <span class="keyword">new</span> <span class="title class_">ArrayList</span>&lt;&gt;();</span><br><span class="line">    list.add(<span class="keyword">new</span> <span class="title class_">byte</span>[_7MB]);</span><br><span class="line">    list.add(<span class="keyword">new</span> <span class="title class_">byte</span>[_512KB]);</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
 
-<h3 id="性能优化"><a href="#性能优化" class="headerlink" title="性能优化"></a>性能优化</h3><h4 id="调整-buckets-size"><a href="#调整-buckets-size" class="headerlink" title="调整 buckets size"></a>调整 buckets size</h4><p>当 size 过小，哈希碰撞增加，链表变长，效率会变低，需要增大 buckets size。</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_">StringTableTest_10</span> &#123;  </span><br><span class="line">  </span><br><span class="line">    <span class="comment">// -XX:StringTableSize=200000 -XX:+PrintStringTableStatistics  </span></span><br><span class="line">    <span class="comment">// 默认-&gt;200000-&gt;1009(最小值)，观察耗时  </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> (<span class="type">BufferedReader</span> <span class="variable">br</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>(<span class="keyword">new</span> <span class="title class_">FileInputStream</span>(<span class="string">&quot;src/main/resources/linux.words&quot;</span>), StandardCharsets.UTF_8))) &#123;  </span><br><span class="line">            <span class="type">String</span> <span class="variable">line</span> <span class="operator">=</span> <span class="literal">null</span>;  </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">while</span> (<span class="literal">true</span>) &#123;  </span><br><span class="line">                line = br.readLine();  </span><br><span class="line">                <span class="keyword">if</span> (line == <span class="literal">null</span>) &#123;  </span><br><span class="line">                    <span class="keyword">break</span>;  </span><br><span class="line">                &#125;  </span><br><span class="line">                line.intern();  </span><br><span class="line">            &#125;  </span><br><span class="line">            System.out.println(<span class="string">&quot;cost: &quot;</span> + (System.nanoTime() - start) / <span class="number">1000000</span>) ;  </span><br><span class="line">        &#125; <span class="keyword">catch</span> (IOException 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>
+<figure class="highlight console"><table><tr><td class="code"><pre><span class="line">[GC (Allocation Failure) [DefNew: 2013K-&gt;721K(9216K), 0.0011172 secs] 2013K-&gt;721K(19456K), 0.0011443 secs] [Times: user=0.00 sys=0.00, real=0.00 secs] </span><br><span class="line">Heap</span><br><span class="line"> def new generation   total 9216K, used 8647K [0x00000000fec00000, 0x00000000ff600000, 0x00000000ff600000)</span><br><span class="line">  eden space 8192K,  96% used [0x00000000fec00000, 0x00000000ff3bd8d0, 0x00000000ff400000)</span><br><span class="line">  from space 1024K,  70% used [0x00000000ff500000, 0x00000000ff5b45f0, 0x00000000ff600000)</span><br><span class="line">  to   space 1024K,   0% used [0x00000000ff400000, 0x00000000ff400000, 0x00000000ff500000)</span><br><span class="line"> tenured generation   total 10240K, used 0K [0x00000000ff600000, 0x0000000100000000, 0x0000000100000000)</span><br><span class="line">   the space 10240K,   0% used [0x00000000ff600000, 0x00000000ff600000, 0x00000000ff600200, 0x0000000100000000)</span><br><span class="line"> Metaspace       used 3354K, capacity 4496K, committed 4864K, reserved 1056768K</span><br><span class="line">  class space    used 360K, capacity 388K, committed 512K, reserved 1048576K</span><br></pre></td></tr></table></figure>
 
-<h4 id="主动运用-intern-的场景"><a href="#主动运用-intern-的场景" class="headerlink" title="主动运用 intern 的场景"></a>主动运用 intern 的场景</h4><p>当你需要大量缓存重复的字符串时，使用 intern 可以大大减少内存占用。</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_">StringTableTest_11</span> &#123;  </span><br><span class="line">  </span><br><span class="line">    <span class="comment">// -Xms500m -Xmx500m -XX:StringTableSize=200000 -XX:+PrintStringTableStatistics  </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;String&gt; words = <span class="keyword">new</span> <span class="title class_">ArrayList</span>&lt;&gt;();  </span><br><span class="line">        System.in.read();  </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">10</span>; i++) &#123;  </span><br><span class="line">            <span class="keyword">try</span> (<span class="type">BufferedReader</span> <span class="variable">br</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>(<span class="keyword">new</span> <span class="title class_">FileInputStream</span>(<span class="string">&quot;src/main/resources/linux.words&quot;</span>), StandardCharsets.UTF_8))) &#123;  </span><br><span class="line">                <span class="type">String</span> <span class="variable">line</span> <span class="operator">=</span> <span class="literal">null</span>;  </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">while</span> (<span class="literal">true</span>) &#123;  </span><br><span class="line">                    line = br.readLine();  </span><br><span class="line">                    <span class="keyword">if</span> (line == <span class="literal">null</span>) &#123;  </span><br><span class="line">                        <span class="keyword">break</span>;  </span><br><span class="line">                    &#125;    </span><br><span class="line">                    <span class="comment">// words.add(line);  </span></span><br><span class="line">                    words.add(line.intern());  </span><br><span class="line">                &#125;  </span><br><span class="line">                System.out.println(<span class="string">&quot;cost: &quot;</span> + (System.nanoTime() - start) / <span class="number">1000000</span>) ;  </span><br><span class="line">            &#125;  </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">&#125;</span><br></pre></td></tr></table></figure>
+<p>由于 <code>eden</code> 区域还能放下 512K 的对象，所以仍然只会发生一次垃圾回收。<br><code>eden</code> 区域的已用空间比例上升到 96%，已用空间的地址为 <code>[0x00000000fec00000, 0x00000000ff3bd8d0)</code>，空间大小为 8116432 byte，约 7.74M，比上一次增加了 524304 byte，即 <code>512 * 1024 + 16</code>。显然第二次添加时，不再因为创建 <code>List&lt;byte[]&gt;</code> 而创建额外的对象，只有创建对象所需的 512K 和 16 字节的对象头。<strong>这一刻数值的精确让人欣喜hhh</strong>。</p>
+<h3 id="新生代空间不足，部分对象提前晋升到老年代"><a href="#新生代空间不足，部分对象提前晋升到老年代" class="headerlink" title="新生代空间不足，部分对象提前晋升到老年代"></a>新生代空间不足，部分对象提前晋升到老年代</h3><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> &#123;</span><br><span class="line">    List&lt;<span class="type">byte</span>[]&gt; list = <span class="keyword">new</span> <span class="title class_">ArrayList</span>&lt;&gt;();</span><br><span class="line">    list.add(<span class="keyword">new</span> <span class="title class_">byte</span>[_7MB]);</span><br><span class="line">    list.add(<span class="keyword">new</span> <span class="title class_">byte</span>[_512KB]);</span><br><span class="line">    list.add(<span class="keyword">new</span> <span class="title class_">byte</span>[_512KB]);</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
 
-<p>使用 VisualVM 观察字符串和 char[] 内存占用情况，可以发现提升显著。</p>
-<img src="/2023/11/03/testing-and-analysis-of-StringTable/Pasted%20image%2020231103131707.png" class="" title="intern 减少内存占用">
+<figure class="highlight console"><table><tr><td class="code"><pre><span class="line">[GC (Allocation Failure) [DefNew: 2013K-&gt;721K(9216K), 0.0013580 secs] 2013K-&gt;721K(19456K), 0.0013932 secs] [Times: user=0.00 sys=0.00, real=0.00 secs] </span><br><span class="line">[GC (Allocation Failure) [DefNew: 8565K-&gt;512K(9216K), 0.0046378 secs] 8565K-&gt;8396K(19456K), 0.0046540 secs] [Times: user=0.00 sys=0.00, real=0.00 secs] </span><br><span class="line">Heap</span><br><span class="line"> def new generation   total 9216K, used 1350K [0x00000000fec00000, 0x00000000ff600000, 0x00000000ff600000)</span><br><span class="line">  eden space 8192K,  10% used [0x00000000fec00000, 0x00000000fecd1a20, 0x00000000ff400000)</span><br><span class="line">  from space 1024K,  50% used [0x00000000ff400000, 0x00000000ff480048, 0x00000000ff500000)</span><br><span class="line">  to   space 1024K,   0% used [0x00000000ff500000, 0x00000000ff500000, 0x00000000ff600000)</span><br><span class="line"> tenured generation   total 10240K, used 7884K [0x00000000ff600000, 0x0000000100000000, 0x0000000100000000)</span><br><span class="line">   the space 10240K,  77% used [0x00000000ff600000, 0x00000000ffdb33a0, 0x00000000ffdb3400, 0x0000000100000000)</span><br><span class="line"> Metaspace       used 3354K, capacity 4496K, committed 4864K, reserved 1056768K</span><br><span class="line">  class space    used 360K, capacity 388K, committed 512K, reserved 1048576K</span><br></pre></td></tr></table></figure>
 
-<h2 id="字符串拼接"><a href="#字符串拼接" class="headerlink" title="字符串拼接"></a>字符串拼接</h2><h3 id="变量的拼接"><a href="#变量的拼接" class="headerlink" title="变量的拼接"></a>变量的拼接</h3><p>字符串变量的拼接，底层是使用 StringBuilder 实现：<code>new StringBuilder().append(&quot;a&quot;).append(&quot;b&quot;).toString()</code>，而 toString 方法使用拼接得到的 char 数组创建一个新的 String 对象，因此 s3 和 s4 是不相同的两个对象。</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_">StringTableTest_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">        <span class="type">String</span> <span class="variable">s1</span> <span class="operator">=</span> <span class="string">&quot;a&quot;</span>;  </span><br><span class="line">        <span class="type">String</span> <span class="variable">s2</span> <span class="operator">=</span> <span class="string">&quot;b&quot;</span>;  </span><br><span class="line">        <span class="type">String</span> <span class="variable">s3</span> <span class="operator">=</span> <span class="string">&quot;ab&quot;</span>;  </span><br><span class="line">        <span class="type">String</span> <span class="variable">s4</span> <span class="operator">=</span> s1 + s2;  </span><br><span class="line">    &#125;  </span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+<p>在第三次添加时，由于 <code>eden</code> 空间不足，因此又发生了第二次垃圾回收。<br><code>[DefNew: 8565K-&gt;512K(9216K), 0.0046378 secs]</code>，新生代的空间占用下降到了 512K，应该是在 from 中留下了第二次添加时的 512K。<br>在第二次添加完成后，<code>eden</code> <code>[0x00000000fec00000, 0x00000000ff3bd8d0)</code> 和 <code>from</code> <code>[0x00000000ff500000, 0x00000000ff5b45f0)</code> 占用的空间为 <code>8116432 + 738800 = 8855232</code> 约 8647.7K，略大于 8565K。很奇怪，第二次垃圾回收前，新生代的空间占用为什么有小幅度下降。<br><code>8565K-&gt;8396K(19456K), 0.0046540 secs</code>，堆的占用空间并未发生明显下降。部分对象因为新生代空间不足，提前晋升到了老年代中。8396K - 512 K 剩余 7884K，全部晋升到老年代，符合 77% 的统计数据。<br><code>eden</code> 中加入了第三次添加时的对象，大于 512K 不少。<br>此时 <code>eden</code>、<code>from</code>、<code>tenured</code> 中均有不好确认成分的空间占用，比如 from 中多了 56 字节。</p>
+<h3 id="新生代空间不足，大对象直接在老年代创建"><a href="#新生代空间不足，大对象直接在老年代创建" class="headerlink" title="新生代空间不足，大对象直接在老年代创建"></a>新生代空间不足，大对象直接在老年代创建</h3><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> &#123;</span><br><span class="line">    List&lt;<span class="type">byte</span>[]&gt; list = <span class="keyword">new</span> <span class="title class_">ArrayList</span>&lt;&gt;();</span><br><span class="line">    list.add(<span class="keyword">new</span> <span class="title class_">byte</span>[_8MB]);</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"> 0: ldc           #2                  // String a</span><br><span class="line"> 2: astore_1</span><br><span class="line"> 3: ldc           #3                  // String b</span><br><span class="line"> 5: astore_2</span><br><span class="line"> 6: ldc           #4                  // String ab</span><br><span class="line"> 8: astore_3</span><br><span class="line"> 9: new           #5                  // class java/lang/StringBuilder</span><br><span class="line">12: dup</span><br><span class="line">13: invokespecial #6                  // Method java/lang/StringBuilder.&quot;&lt;init&gt;&quot;:()V</span><br><span class="line">16: aload_1</span><br><span class="line">17: invokevirtual #7                  // Method java/lang/StringBuilder.append:(Ljava/lang/String;)Ljava/lang/StringBuilder;</span><br><span class="line">20: aload_2</span><br><span class="line">21: invokevirtual #7                  // Method java/lang/StringBuilder.append:(Ljava/lang/String;)Ljava/lang/StringBuilder;</span><br><span class="line">24: invokevirtual #8                  // Method java/lang/StringBuilder.toString:()Ljava/lang/String;</span><br><span class="line">27: astore        4</span><br><span class="line">29: return</span><br></pre></td></tr></table></figure>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line">Heap</span><br><span class="line"> def <span class="keyword">new</span> <span class="title class_">generation</span>   total 9216K, used 2177K [<span class="number">0x00000000fec00000</span>, <span class="number">0x00000000ff600000</span>, <span class="number">0x00000000ff600000</span>)</span><br><span class="line">  eden space 8192K,  <span class="number">26</span>% used [<span class="number">0x00000000fec00000</span>, <span class="number">0x00000000fee20730</span>, <span class="number">0x00000000ff400000</span>)</span><br><span class="line">  from space 1024K,   <span class="number">0</span>% used [<span class="number">0x00000000ff400000</span>, <span class="number">0x00000000ff400000</span>, <span class="number">0x00000000ff500000</span>)</span><br><span class="line">  to   space 1024K,   <span class="number">0</span>% used [<span class="number">0x00000000ff500000</span>, <span class="number">0x00000000ff500000</span>, <span class="number">0x00000000ff600000</span>)</span><br><span class="line"> tenured generation   total 10240K, used 8192K [<span class="number">0x00000000ff600000</span>, <span class="number">0x0000000100000000</span>, <span class="number">0x0000000100000000</span>)</span><br><span class="line">   the space 10240K,  <span class="number">80</span>% used [<span class="number">0x00000000ff600000</span>, <span class="number">0x00000000ffe00010</span>, <span class="number">0x00000000ffe00200</span>, <span class="number">0x0000000100000000</span>)</span><br><span class="line"> Metaspace       used 3353K, capacity 4496K, committed 4864K, reserved 1056768K</span><br><span class="line">  <span class="keyword">class</span> <span class="title class_">space</span>    used 360K, capacity 388K, committed 512K, reserved 1048576K</span><br></pre></td></tr></table></figure>
 
-<h3 id="常量的拼接"><a href="#常量的拼接" class="headerlink" title="常量的拼接"></a>常量的拼接</h3><p>字符串常量的拼接是在编译期间，因为已知结果而被优化为一个字符串常量。又因为 “ab” 字符串在 StringTable 中是已存在的，所以不会重新创建新对象。</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_">StringTableTest_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">        <span class="type">String</span> <span class="variable">s1</span> <span class="operator">=</span> <span class="string">&quot;a&quot;</span>;</span><br><span class="line">        <span class="type">String</span> <span class="variable">s2</span> <span class="operator">=</span> <span class="string">&quot;b&quot;</span>;</span><br><span class="line">        <span class="type">String</span> <span class="variable">s3</span> <span class="operator">=</span> <span class="string">&quot;ab&quot;</span>;</span><br><span class="line">        <span class="type">String</span> <span class="variable">s4</span> <span class="operator">=</span> s1 + s2;</span><br><span class="line">        <span class="type">String</span> <span class="variable">s5</span> <span class="operator">=</span> <span class="string">&quot;a&quot;</span> + <span class="string">&quot;b&quot;</span>;</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+<p>在 Eden 空间肯定不足而老年代空间足够的情况下，大对象会直接在老年代中创建，此时不会发生 GC。</p>
+<h3 id="内存不足-OOM"><a href="#内存不足-OOM" class="headerlink" title="内存不足 OOM"></a>内存不足 OOM</h3><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> &#123;</span><br><span class="line">    List&lt;<span class="type">byte</span>[]&gt; list = <span class="keyword">new</span> <span class="title class_">ArrayList</span>&lt;&gt;();</span><br><span class="line">    list.add(<span class="keyword">new</span> <span class="title class_">byte</span>[_8MB]);</span><br><span class="line">    list.add(<span class="keyword">new</span> <span class="title class_">byte</span>[_8MB]);</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"> 0: ldc           #2                  // String a</span><br><span class="line"> 2: astore_1</span><br><span class="line"> 3: ldc           #3                  // String b</span><br><span class="line"> 5: astore_2</span><br><span class="line"> 6: ldc           #4                  // String ab</span><br><span class="line"> 8: astore_3</span><br><span class="line"> 9: new           #5                  // class java/lang/StringBuilder</span><br><span class="line">12: dup</span><br><span class="line">13: invokespecial #6                  // Method java/lang/StringBuilder.&quot;&lt;init&gt;&quot;:()V</span><br><span class="line">16: aload_1</span><br><span class="line">17: invokevirtual #7                  // Method java/lang/StringBuilder.append:(Ljava/lang/String;)Ljava/lang/StringBuilder;</span><br><span class="line">20: aload_2</span><br><span class="line">21: invokevirtual #7                  // Method java/lang/StringBuilder.append:(Ljava/lang/String;)Ljava/lang/StringBuilder;</span><br><span class="line">24: invokevirtual #8                  // Method java/lang/StringBuilder.toString:()Ljava/lang/String;</span><br><span class="line">27: astore        4</span><br><span class="line">29: ldc           #4                  // String ab</span><br><span class="line">31: astore        5</span><br><span class="line">33: return</span><br></pre></td></tr></table></figure>
+<figure class="highlight console"><table><tr><td class="code"><pre><span class="line">waiting...</span><br><span class="line">[GC (Allocation Failure) [DefNew: 4711K-&gt;928K(9216K), 0.0017245 secs][Tenured: 8192K-&gt;9117K(10240K), 0.0021690 secs] 12903K-&gt;9117K(19456K), [Metaspace: 4267K-&gt;4267K(1056768K)], 0.0039336 secs] [Times: user=0.00 sys=0.00, real=0.00 secs] </span><br><span class="line">[Full GC (Allocation Failure) [Tenured: 9117K-&gt;9063K(10240K), 0.0014352 secs] 9117K-&gt;9063K(19456K), [Metaspace: 4267K-&gt;4267K(1056768K)], 0.0014614 secs] [Times: user=0.00 sys=0.00, real=0.00 secs] </span><br><span class="line">Exception in thread &quot;Thread-0&quot; java.lang.OutOfMemoryError: Java heap space</span><br><span class="line">	at com.moralok.jvm.gc.JvmGcTest.lambda$main$0(JvmGcTest.java:27)</span><br><span class="line">	at com.moralok.jvm.gc.JvmGcTest$$Lambda$1/2003749087.run(Unknown Source)</span><br><span class="line">	at java.lang.Thread.run(Thread.java:750)</span><br><span class="line"></span><br><span class="line">Heap</span><br><span class="line"> def new generation   total 9216K, used 1502K [0x00000000fec00000, 0x00000000ff600000, 0x00000000ff600000)</span><br><span class="line">  eden space 8192K,  18% used [0x00000000fec00000, 0x00000000fed77a00, 0x00000000ff400000)</span><br><span class="line">  from space 1024K,   0% used [0x00000000ff500000, 0x00000000ff500000, 0x00000000ff600000)</span><br><span class="line">  to   space 1024K,   0% used [0x00000000ff400000, 0x00000000ff400000, 0x00000000ff500000)</span><br><span class="line"> tenured generation   total 10240K, used 9063K [0x00000000ff600000, 0x0000000100000000, 0x0000000100000000)</span><br><span class="line">   the space 10240K,  88% used [0x00000000ff600000, 0x00000000ffed9c50, 0x00000000ffed9e00, 0x0000000100000000)</span><br><span class="line"> Metaspace       used 4787K, capacity 4884K, committed 4992K, reserved 1056768K</span><br><span class="line">  class space    used 522K, capacity 558K, committed 640K, reserved 1048576K</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><ol>
-<li><a href="https://www.zhihu.com/question/55994121/answer/147296098">Java 中new String(“字面量”) 中 “字面量” 是何时进入字符串常量池的? - xinxi的回答 - 知乎</a></li>
-<li><a href="https://www.iteye.com/topic/774673">请别再拿“String s &#x3D; new String(“xyz”);创建了多少个String实例”来面试了吧</a></li>
-<li><a href="https://blog.csdn.net/zyplanke/article/details/108699727">JVM中字符串常量池StringTable在内存中形式分析</a></li>
-</ol>
+<p>当新生代和老年代的空间均不足时，在尝试 GC 和 Full GC 后仍不能成功分配对象，就会发生 <code>OutOfMemoryError</code>。</p>
+<h4 id="线程中发生内存不足，不会影响其他线程"><a href="#线程中发生内存不足，不会影响其他线程" class="headerlink" title="线程中发生内存不足，不会影响其他线程"></a>线程中发生内存不足，不会影响其他线程</h4><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> &#123;</span><br><span class="line">    List&lt;<span class="type">byte</span>[]&gt; list = <span class="keyword">new</span> <span class="title class_">ArrayList</span>&lt;&gt;();</span><br><span class="line"></span><br><span class="line">    <span class="keyword">new</span> <span class="title class_">Thread</span>(() -&gt; &#123;</span><br><span class="line">        list.add(<span class="keyword">new</span> <span class="title class_">byte</span>[_8MB]);</span><br><span class="line">        list.add(<span class="keyword">new</span> <span class="title class_">byte</span>[_8MB]);</span><br><span class="line">    &#125;).start();</span><br><span class="line"></span><br><span class="line">    System.out.println(<span class="string">&quot;waiting...&quot;</span>);</span><br><span class="line">    <span class="keyword">try</span> &#123;</span><br><span class="line">        System.in.read();</span><br><span class="line">    &#125; <span class="keyword">catch</span> (IOException 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>
+
+<figure class="highlight console"><table><tr><td class="code"><pre><span class="line">[GC (Allocation Failure) [DefNew: 2013K-&gt;721K(9216K), 0.0012274 secs][Tenured: 8192K-&gt;8912K(10240K), 0.0113036 secs] 10205K-&gt;8912K(19456K), [Metaspace: 3345K-&gt;3345K(1056768K)], 0.0125751 secs] [Times: user=0.00 sys=0.00, real=0.01 secs] </span><br><span class="line">[Full GC (Allocation Failure) [Tenured: 8912K-&gt;8895K(10240K), 0.0011880 secs] 8912K-&gt;8895K(19456K), [Metaspace: 3345K-&gt;3345K(1056768K)], 0.0012009 secs] [Times: user=0.00 sys=0.00, real=0.00 secs] </span><br><span class="line">Heap</span><br><span class="line"> def new generation   total 9216K, used 246K [0x00000000fec00000, 0x00000000ff600000, 0x00000000ff600000)</span><br><span class="line">  eden space 8192K,   3% used [0x00000000fec00000, 0x00000000fec3d890, 0x00000000ff400000)</span><br><span class="line">  from space 1024K,   0% used [0x00000000ff500000, 0x00000000ff500000, 0x00000000ff600000)</span><br><span class="line">  to   space 1024K,   0% used [0x00000000ff400000, 0x00000000ff400000, 0x00000000ff500000)</span><br><span class="line"> tenured generation   total 10240K, used 8895K [0x00000000ff600000, 0x0000000100000000, 0x0000000100000000)</span><br><span class="line">   the space 10240K,  86% used [0x00000000ff600000, 0x00000000ffeafce0, 0x00000000ffeafe00, 0x0000000100000000)</span><br><span class="line"> Metaspace       used 3380K, capacity 4496K, committed 4864K, reserved 1056768K</span><br><span class="line">  class space    used 363K, capacity 388K, committed 512K, reserved 1048576K</span><br><span class="line">Exception in thread &quot;main&quot; java.lang.OutOfMemoryError: Java heap space</span><br><span class="line">	at com.moralok.jvm.gc.JvmGcTest.main(JvmGcTest.java:21)</span><br></pre></td></tr></table></figure>
+
+<p>当 <code>Thread-0</code> 发生 <code>OutOfMemoryError</code> 后，<code>main</code> 线程仍然正常运行。</p>
+<h3 id="大对象的划分指标"><a href="#大对象的划分指标" class="headerlink" title="大对象的划分指标"></a>大对象的划分指标</h3><p>当创建的大对象 + 对象头的容量小于等于 <code>eden</code>，如果 GC 后的存活对象可以放入 <code>to</code>，那么还是会先在 <code>eden</code> 中创建大对象。<br>在本案例中，又会马上发生一次 GC，大对象提前晋升到老年代中。</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> &#123;</span><br><span class="line">    List&lt;<span class="type">byte</span>[]&gt; list = <span class="keyword">new</span> <span class="title class_">ArrayList</span>&lt;&gt;();</span><br><span class="line">    list.add(<span class="keyword">new</span> <span class="title class_">byte</span>[_8MB - <span class="number">16</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">[GC (Allocation Failure) [DefNew: 2013K-&gt;693K(9216K), 0.0015517 secs] 2013K-&gt;693K(19456K), 0.0015828 secs] [Times: user=0.00 sys=0.00, real=0.00 secs] </span><br><span class="line">[GC (Allocation Failure) [DefNew: 8885K-&gt;0K(9216K), 0.0048110 secs] 8885K-&gt;8885K(19456K), 0.0048264 secs] [Times: user=0.00 sys=0.02, real=0.00 secs] </span><br><span class="line">Heap</span><br><span class="line"> def new generation   total 9216K, used 410K [0x00000000fec00000, 0x00000000ff600000, 0x00000000ff600000)</span><br><span class="line">  eden space 8192K,   5% used [0x00000000fec00000, 0x00000000fec66958, 0x00000000ff400000)</span><br><span class="line">  from space 1024K,   0% used [0x00000000ff400000, 0x00000000ff400000, 0x00000000ff500000)</span><br><span class="line">  to   space 1024K,   0% used [0x00000000ff500000, 0x00000000ff500000, 0x00000000ff600000)</span><br><span class="line"> tenured generation   total 10240K, used 8885K [0x00000000ff600000, 0x0000000100000000, 0x0000000100000000)</span><br><span class="line">   the space 10240K,  86% used [0x00000000ff600000, 0x00000000ffead580, 0x00000000ffead600, 0x0000000100000000)</span><br><span class="line"> Metaspace       used 3321K, capacity 4496K, committed 4864K, reserved 1056768K</span><br><span class="line">  class space    used 354K, capacity 388K, committed 512K, reserved 1048576K</span><br></pre></td></tr></table></figure>
+
+<p>尽管最终大部分对象提前晋升到老年代，但是可以看到第二次 GC 前的新生代空间占用，可见数组分配时，所需空间刚好为 Eden 空间大小时，还是会在 eden 创建对象。</p>
+<h3 id="注意事项"><a href="#注意事项" class="headerlink" title="注意事项"></a>注意事项</h3><ul>
+<li>正常情况下，新对象都是在 eden 中创建。</li>
+<li>空间足够的意思并非空间占用相加的值仍小于总额，而是有连续的一片内存可供分配。因此紧凑才能利用率高。</li>
+<li>正常情况下，GC 前 to 区域总是为空，GC 后 eden 区域总是为空。</li>
+<li>正常情况下，GC 后 eden 和 from 的存活对象要么去了 to，要么去老年代。</li>
+<li>只要 GC 后腾空 eden，创建在 eden 中的新对象的空间占用可以等于 eden 的大小。</li>
+</ul>
+<p>尽管总体上有迹可循，但是 GC 的具体情况，仍然需要具体分析，有很多分支情况未一一确认。</p>
 ]]></content>
       <tags>
         <tag>java</tag>
@@ -1236,149 +1124,201 @@
       </tags>
   </entry>
   <entry>
-    <title>关于 Java 字节码指令的一些例子分析</title>
-    <url>/2023/11/09/some-examples-of-Java-bytecode-instruction-analysis/</url>
-    <content><![CDATA[<h2 id="演示字节码指令的执行"><a href="#演示字节码指令的执行" class="headerlink" title="演示字节码指令的执行"></a>演示字节码指令的执行</h2><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_">ByteCodeTest_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">        <span class="type">int</span> <span class="variable">a</span> <span class="operator">=</span> <span class="number">10</span>;</span><br><span class="line">        <span class="type">int</span> <span class="variable">b</span> <span class="operator">=</span> Short.MAX_VALUE + <span class="number">1</span>;</span><br><span class="line">        <span class="type">int</span> <span class="variable">c</span> <span class="operator">=</span> a + b;</span><br><span class="line">        System.out.println(c);</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+    <title>Java 类加载器源码分析</title>
+    <url>/2023/07/13/Java-class-loader-source-code-analysis/</url>
+    <content><![CDATA[<h3 id="组织类加载工作：loadClass"><a href="#组织类加载工作：loadClass" class="headerlink" title="组织类加载工作：loadClass"></a>组织类加载工作：loadClass</h3><p>当 <code>Java</code> 程序启动的时候，<code>Java</code> 虚拟机会调用 <code>java.lang.ClassLoader#loadClass(java.lang.String)</code> 加载 <code>main</code> 方法所在的类。</p>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> Class&lt;?&gt; loadClass(String name) <span class="keyword">throws</span> ClassNotFoundException &#123;</span><br><span class="line">    <span class="keyword">return</span> loadClass(name, <span class="literal">false</span>);</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
 
-<h3 id="操作数栈和本地变量表的大小"><a href="#操作数栈和本地变量表的大小" class="headerlink" title="操作数栈和本地变量表的大小"></a>操作数栈和本地变量表的大小</h3><p>在编译期间就可计算得到操作数栈和本地变量表的大小。</p>
-<figure class="highlight console"><table><tr><td class="code"><pre><span class="line">stack=2, locals=4, args_size=1</span><br></pre></td></tr></table></figure>
+<p>根据注释可知，此方法加载具有指定二进制名称的类，它由 <code>Java</code> 虚拟机调用来解析类引用，调用它等同于调用 <code>loadClass(name, false)</code>。</p>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">protected</span> Class&lt;?&gt; loadClass(String name, <span class="type">boolean</span> resolve)</span><br><span class="line">    <span class="keyword">throws</span> ClassNotFoundException</span><br><span class="line">&#123;</span><br><span class="line">    <span class="comment">// 以二进制名称获取类加载的锁进行同步</span></span><br><span class="line">    <span class="keyword">synchronized</span> (getClassLoadingLock(name)) &#123;</span><br><span class="line">        <span class="comment">// First, check if the class has already been loaded</span></span><br><span class="line">        <span class="comment">// 首先检查类是否已加载，根据该方法注释可知：</span></span><br><span class="line">        <span class="comment">// 如果当前类加载器已经被 Java 虚拟机记录为具有该二进制名称的类的加载器（initiating loader），Java 虚拟机可以直接返回 Class 对象。</span></span><br><span class="line">        Class&lt;?&gt; c = findLoadedClass(name);</span><br><span class="line">        <span class="keyword">if</span> (c == <span class="literal">null</span>) &#123;</span><br><span class="line">            <span class="type">long</span> <span class="variable">t0</span> <span class="operator">=</span> System.nanoTime();</span><br><span class="line">            <span class="keyword">try</span> &#123;</span><br><span class="line">                <span class="comment">// 如果类还未加载，先委派给父·类加载器进行加载，如果父·类加载器为 null，则使用虚拟机内建的类加载器进行加载</span></span><br><span class="line">                <span class="keyword">if</span> (parent != <span class="literal">null</span>) &#123;</span><br><span class="line">                    <span class="comment">// 递归调用</span></span><br><span class="line">                    c = parent.loadClass(name, <span class="literal">false</span>);</span><br><span class="line">                &#125; <span class="keyword">else</span> &#123;</span><br><span class="line">                    <span class="comment">// 递归调用的终结点</span></span><br><span class="line">                    c = findBootstrapClassOrNull(name);</span><br><span class="line">                &#125;</span><br><span class="line">            &#125; <span class="keyword">catch</span> (ClassNotFoundException e) &#123;</span><br><span class="line">                <span class="comment">// ClassNotFoundException thrown if class not found</span></span><br><span class="line">                <span class="comment">// from the non-null parent class loader</span></span><br><span class="line">                <span class="comment">// 当父·类加载器长尝试加载但是失败，捕获异常但是什么都不做，因为接下来，当前类加载器需要自己也尝试加载。</span></span><br><span class="line">            &#125;</span><br><span class="line"></span><br><span class="line">            <span class="keyword">if</span> (c == <span class="literal">null</span>) &#123;</span><br><span class="line">                <span class="comment">// If still not found, then invoke findClass in order</span></span><br><span class="line">                <span class="comment">// to find the class.</span></span><br><span class="line">                <span class="type">long</span> <span class="variable">t1</span> <span class="operator">=</span> System.nanoTime();</span><br><span class="line">                <span class="comment">// 父·类加载器未找到类，当前类加载器自己找。</span></span><br><span class="line">                c = findClass(name);</span><br><span class="line"></span><br><span class="line">                <span class="comment">// this is the defining class loader; record the stats</span></span><br><span class="line">                sun.misc.PerfCounter.getParentDelegationTime().addTime(t1 - t0);</span><br><span class="line">                sun.misc.PerfCounter.getFindClassTime().addElapsedTimeFrom(t1);</span><br><span class="line">                sun.misc.PerfCounter.getFindClasses().increment();</span><br><span class="line">            &#125;</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="keyword">if</span> (resolve) &#123;</span><br><span class="line">            resolveClass(c);</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="keyword">return</span> c;</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
 
-<h3 id="本地变量表"><a href="#本地变量表" class="headerlink" title="本地变量表"></a>本地变量表</h3><p>Slot，即槽位，可理解为索引。</p>
-<figure class="highlight console"><table><tr><td class="code"><pre><span class="line">Start  Length  Slot  Name   Signature</span><br><span class="line">    0      18     0  args   [Ljava/lang/String;</span><br><span class="line">    3      15     1     a   I</span><br><span class="line">    6      12     2     b   I</span><br><span class="line">   10       8     3     c   I</span><br></pre></td></tr></table></figure>
+<p>根据注释可知，<code>java.lang.ClassLoader#loadClass(java.lang.String, boolean)</code> 同样是加载“具有指定二进制名称的类”，此方法的实现按以下顺序搜索类：</p>
+<ol>
+<li>调用 <code>findLoadedClass(String)</code> 以检查该类是否已加载。</li>
+<li>在父·类加载器上调用 <code>loadClass</code> 方法。如果父·类加载器为空，则使用虚拟机内置的类加载器。</li>
+<li>调用 <code>findClass(String)</code> 方法来查找该类。</li>
+</ol>
+<p>如果使用上述步骤找到了该类（找到并定义类），并且解析标志为 <code>true</code>，则此方法将对生成的 <code>Class</code> 对象调用 <code>resolveClass(Class)</code> 方法。鼓励 <code>ClassLoader</code> 的子类重写 <code>findClass(String)</code>，而不是此方法。除非被重写，否则此方法在整个类加载过程中以 <code>getClassLoadingLock</code> 方法的结果进行同步。</p>
+<blockquote>
+<p>注意：<strong>父·类加载器</strong>并非<strong>父类·类加载器</strong>（当前类加载器的父类），而是当前的类加载器的 <code>parent</code> 属性被赋值另外一个类加载器实例，其含义更接近于“可以委派类加载工作的另一个类加载器（一个帮忙干活的上级）”。虽然绝大多数说法中，当一个类加载器的 <code>parent</code> 值为 <code>null</code> 时，它的父·类加载器是引导类加载器（<code>bootstrap class loader</code>），但是当看到 <code>findBootstrapClassOrNull</code> 方法时，我有点困惑，因为我以为会看到语义类似于 <code>loadClassByBootstrapClassLoader</code> 这样的方法名。从注释和代码的语义上看，<code>bootstrap class loader</code> 不像是任何一个类加载器的父·类加载器，但是从类加载的机制设计上说，它是，只是因为它并非由 Java 语言编写而成，不能实例化并赋值给 <code>parent</code> 属性。<code>findBootstrapClassOrNull</code> 方法的语义更接近于：当一个类加载器的父·类加载器为 <code>null</code> 时，将准备加载的目标类先当作启动类（<code>Bootstrap Class</code>）尝试查找，如果找不到就返回 <code>null</code>。</p>
+</blockquote>
+<h4 id="怎么并行地加载类-getClassLoadingLock"><a href="#怎么并行地加载类-getClassLoadingLock" class="headerlink" title="怎么并行地加载类 getClassLoadingLock"></a>怎么并行地加载类 getClassLoadingLock</h4><p>需要加载的类可能很多很多，我们很容易想到如果可以并行地加载类就好了。显然，<code>JDK</code> 的编写者考虑到了这一点。<br>此方法返回类加载操作的锁对象。为了向后兼容，此方法的默认实现的行为如下。如果此 <code>ClassLoader</code> 对象注册为具备并行能力，则该方法返回与指定类名关联的专用对象。 否则，该方法返回此 <code>ClassLoader</code> 对象。<br>简单地说，如果 <code>ClassLoader</code> 对象注册为具备并行能力，那么一个 <code>name</code> 一个锁对象，已创建的锁对象保存在 <code>ConcurrentHashMap</code> 类型的 <code>parallelLockMap</code> 中，这样类加载工作可以并行；否则所有类加载工作共用一个锁对象，就是 <code>ClassLoader</code> 对象本身。<br>这个方案意味着非同名的目标类可以认为在加载时没有冲突？</p>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">protected</span> Object <span class="title function_">getClassLoadingLock</span><span class="params">(String className)</span> &#123;</span><br><span class="line">    <span class="type">Object</span> <span class="variable">lock</span> <span class="operator">=</span> <span class="built_in">this</span>;</span><br><span class="line">    <span class="keyword">if</span> (parallelLockMap != <span class="literal">null</span>) &#123;</span><br><span class="line">        <span class="type">Object</span> <span class="variable">newLock</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">Object</span>();</span><br><span class="line">        lock = parallelLockMap.putIfAbsent(className, newLock);</span><br><span class="line">        <span class="keyword">if</span> (lock == <span class="literal">null</span>) &#123;</span><br><span class="line">            lock = newLock;</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="keyword">return</span> lock;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
 
-<h3 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</h3><figure class="highlight console"><table><tr><td class="code"><pre><span class="line"><span class="meta prompt_">#</span><span class="language-bash">3 = Integer            32768</span></span><br><span class="line"><span class="meta prompt_">#</span><span class="language-bash">4 = Fieldref           <span class="comment">#27.#28        // java/lang/System.out:Ljava/io/PrintStream;</span></span></span><br><span class="line"><span class="meta prompt_">#</span><span class="language-bash">5 = Methodref          <span class="comment">#29.#30        // java/io/PrintStream.println:(I)V</span></span> </span><br></pre></td></tr></table></figure>
+<h5 id="什么是-“ClassLoader-对象注册为具有并行能力”呢？"><a href="#什么是-“ClassLoader-对象注册为具有并行能力”呢？" class="headerlink" title="什么是 “ClassLoader 对象注册为具有并行能力”呢？"></a>什么是 “<code>ClassLoader</code> 对象注册为具有并行能力”呢？</h5><p><code>AppClassLoader</code> 中有一段 <code>static</code> 代码。事实上 <code>java.lang.ClassLoader#registerAsParallelCapable</code> 是将 <code>ClassLoader</code> 对象注册为具有并行能力唯一的入口。因此，所有想要注册为具有并行能力的 <code>ClassLoader</code> 都需要调用一次该方法。</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">    ClassLoader.registerAsParallelCapable();</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
 
-<img src="/2023/11/09/some-examples-of-Java-bytecode-instruction-analysis/Snipaste_2023-11-10_00-28-14.png" class="" title="字节码指令执行栈帧示意图">
+<p><code>java.lang.ClassLoader#registerAsParallelCapable</code> 方法有一个注解 <code>@CallerSensitive</code>，这是因为它的代码中调用的 <code>native</code> 方法 <code>sun.reflect.Reflection#getCallerClass()</code> 方法。由注释可知，当且仅当以下所有条件全部满足时才注册成功：</p>
+<ol>
+<li>尚未创建调用者的实例（类加载器尚未实例化）</li>
+<li>调用者的所有超类（<code>Object</code> 类除外）都注册为具有并行能力。</li>
+</ol>
+<h5 id="怎么保证这两个条件成立呢？"><a href="#怎么保证这两个条件成立呢？" class="headerlink" title="怎么保证这两个条件成立呢？"></a>怎么保证这两个条件成立呢？</h5><ol>
+<li>对于第一个条件，可以通过将调用的代码写在 <code>static</code> 代码块中来实现。如果写在构造器方法里，并且通过单例模式保证只实例化一次可以吗？答案是不行的，后续会解释这个“注册”行为在构造器方法中是如何被使用以及为何不能写在构造器方法里。</li>
+<li>对于第二个条件，由于 <code>Java</code> 虚拟机加载类时，总是会先尝试加载其父类，又因为加载类时会先调用 <code>static</code> 代码块，因此父类的 <code>static</code> 代码块总是先于子类的 <code>static</code> 代码块。</li>
+</ol>
+<p>你可以看到 <code>AppClassLoader-&gt;URLClassLoader-&gt;SecureClassLoader-&gt;ClassLoader</code> 均在 <code>static</code> 代码块实现注册，以保证满足以上两个条件。</p>
+<h5 id="注册工作做了什么？"><a href="#注册工作做了什么？" class="headerlink" title="注册工作做了什么？"></a>注册工作做了什么？</h5><p>简单地说就是保存了类加载器所属 <code>Class</code> 的 <code>Set</code>。</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">protected</span> <span class="keyword">static</span> <span class="type">boolean</span> <span class="title function_">registerAsParallelCapable</span><span class="params">()</span> &#123;</span><br><span class="line">    <span class="comment">// 获得此方法的调用者的 Class 实例，asSubClass 可以将 Class&lt;?&gt; 类型的 Class 转换为代表指定类的子类的 Class&lt;? extends U&gt; 类型的 Class。</span></span><br><span class="line">    Class&lt;? <span class="keyword">extends</span> <span class="title class_">ClassLoader</span>&gt; callerClass =</span><br><span class="line">        Reflection.getCallerClass().asSubclass(ClassLoader.class);</span><br><span class="line">    <span class="comment">// 注册调用者的 Class 为具有并行能力</span></span><br><span class="line">    <span class="keyword">return</span> ParallelLoaders.register(callerClass);</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
 
-<h3 id="字节码指令"><a href="#字节码指令" class="headerlink" title="字节码指令"></a>字节码指令</h3><figure class="highlight console"><table><tr><td class="code"><pre><span class="line"> 0: bipush        10</span><br><span class="line"> 2: istore_1</span><br><span class="line"> 3: ldc           #3             // int 32768</span><br><span class="line"> 5: istore_2</span><br><span class="line"> 6: iload_1</span><br><span class="line"> 7: iload_2</span><br><span class="line"> 8: iadd</span><br><span class="line"> 9: istore_3</span><br><span class="line">10: getstatic     #4             // Field java/lang/System.out:Ljava/io/PrintStream;</span><br><span class="line">13: iload_3</span><br><span class="line">14: invokevirtual #5             // Method java/io/PrintStream.println:(I)V</span><br><span class="line">17: return</span><br></pre></td></tr></table></figure>
-<ul>
-<li>bipush，将一个 byte，推入操作数栈。<ul>
-<li>short 范围内的数是和字节码指令一起存储的，范围外的数是存储在运行时常量池中的。</li>
-<li>操作数栈的宽度是 4 个字节，short 范围内的数在推入操作数栈前会经过符号扩展成为 int。</li>
-</ul>
-</li>
-<li>istore_1，将栈顶的 int，存入局部变量表，槽位 1。</li>
-<li>ldc，从运行时常量池中将指定常量推入操作数栈。</li>
-<li>istore_2，将栈顶的 int，存入局部变量表，槽位 2。</li>
-<li>iload_1 iload_2，依次从局部变量表将两个 int 推入操作数栈，槽位分别是 1 和 2。</li>
-<li>iadd，将栈顶的两个 int 弹出并相加，将结果推入操作数栈。</li>
-<li>istore_3，将栈顶的 int，存入局部变量表，槽位 3。</li>
-<li>getstatic，获取类的静态属性，推入操作数栈。</li>
-<li>iload_3，从局部变量表将 int 推入操作数栈，槽位 3。</li>
-<li>invokevirtual，将栈顶的参数依次弹出，调用实例方法。</li>
-<li>return，返回 void</li>
-</ul>
-<h2 id="分析-a-和-a"><a href="#分析-a-和-a" class="headerlink" title="分析 a++ 和 ++a"></a>分析 a++ 和 ++a</h2><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_">ByteCodeTest_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">        <span class="type">int</span> <span class="variable">a</span> <span class="operator">=</span> <span class="number">10</span>;</span><br><span class="line">        <span class="type">int</span> <span class="variable">b</span> <span class="operator">=</span> a++ + ++a + a--;</span><br><span class="line">        System.out.println(a);</span><br><span class="line">        System.out.println(b);</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+<p>方法 <code>java.lang.ClassLoader.ParallelLoaders#register</code>。<code>ParallelLoaders</code> 封装了一组具有并行能力的加载器类型。就是持有 <code>ClassLoader</code> 的 <code>Class</code> 实例的集合，并保证添加时加同步锁。</p>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="comment">// private 修饰，只有其外部类 ClassLoader 才可以使用</span></span><br><span class="line"><span class="comment">// static 修饰，内部类如果需要定义 static 方法或者 static 变量，必须用 static 修饰</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_">ParallelLoaders</span> &#123;</span><br><span class="line">    <span class="comment">// private 修饰构造器方法，不希望这个类被实例化，只想要使用它的静态变量和方法。</span></span><br><span class="line">    <span class="keyword">private</span> <span class="title function_">ParallelLoaders</span><span class="params">()</span> &#123;&#125;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// the set of parallel capable loader types</span></span><br><span class="line">    <span class="comment">// 使用 loaderTypes 时通过 synchronized 加同步锁</span></span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">static</span> <span class="keyword">final</span> Set&lt;Class&lt;? <span class="keyword">extends</span> <span class="title class_">ClassLoader</span>&gt;&gt; loaderTypes =</span><br><span class="line">        Collections.newSetFromMap(</span><br><span class="line">            <span class="comment">// todo: 为什么使用弱引用来实现？为了卸载类时的垃圾回收？</span></span><br><span class="line">            <span class="keyword">new</span> <span class="title class_">WeakHashMap</span>&lt;Class&lt;? <span class="keyword">extends</span> <span class="title class_">ClassLoader</span>&gt;, Boolean&gt;());</span><br><span class="line">    <span class="keyword">static</span> &#123;</span><br><span class="line">        <span class="comment">// 将 ClassLoader 本身注册为具有并行能力</span></span><br><span class="line">        <span class="keyword">synchronized</span> (loaderTypes) &#123; loaderTypes.add(ClassLoader.class); &#125;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="comment">/**</span></span><br><span class="line"><span class="comment">     * Registers the given class loader type as parallel capabale.</span></span><br><span class="line"><span class="comment">     * Returns &#123;<span class="doctag">@code</span> true&#125; is successfully registered; &#123;<span class="doctag">@code</span> false&#125; if</span></span><br><span class="line"><span class="comment">     * loader&#x27;s super class is not registered.</span></span><br><span class="line"><span class="comment">     */</span></span><br><span class="line">    <span class="keyword">static</span> <span class="type">boolean</span> <span class="title function_">register</span><span class="params">(Class&lt;? extends ClassLoader&gt; c)</span> &#123;</span><br><span class="line">        <span class="keyword">synchronized</span> (loaderTypes) &#123;</span><br><span class="line">            <span class="keyword">if</span> (loaderTypes.contains(c.getSuperclass())) &#123;</span><br><span class="line">                <span class="comment">// register the class loader as parallel capable</span></span><br><span class="line">                <span class="comment">// if and only if all of its super classes are.</span></span><br><span class="line">                <span class="comment">// Note: given current classloading sequence, if</span></span><br><span class="line">                <span class="comment">// the immediate super class is parallel capable,</span></span><br><span class="line">                <span class="comment">// all the super classes higher up must be too.</span></span><br><span class="line">                <span class="comment">// 当且仅当其所有超类都具有并行能力时，才将类加载器注册为具有并行能力。</span></span><br><span class="line">                <span class="comment">// 注意：给定当前的类加载顺序（加载类时，Java 虚拟机总是先尝试加载其父类），如果直接超类具有并行能力，则所有更高的超类也必然具有并行能力。</span></span><br><span class="line">                loaderTypes.add(c);</span><br><span class="line">                <span class="keyword">return</span> <span class="literal">true</span>;</span><br><span class="line">            &#125; <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">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="comment">/**</span></span><br><span class="line"><span class="comment">     * Returns &#123;<span class="doctag">@code</span> true&#125; if the given class loader type is</span></span><br><span class="line"><span class="comment">     * registered as parallel capable.</span></span><br><span class="line"><span class="comment">     */</span></span><br><span class="line">    <span class="keyword">static</span> <span class="type">boolean</span> <span class="title function_">isRegistered</span><span class="params">(Class&lt;? extends ClassLoader&gt; c)</span> &#123;</span><br><span class="line">        <span class="keyword">synchronized</span> (loaderTypes) &#123;</span><br><span class="line">            <span class="keyword">return</span> loaderTypes.contains(c);</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="字节码指令-1"><a href="#字节码指令-1" class="headerlink" title="字节码指令"></a>字节码指令</h3><figure class="highlight console"><table><tr><td class="code"><pre><span class="line"> 0: bipush        10</span><br><span class="line"> 2: istore_1</span><br><span class="line"> 3: iload_1</span><br><span class="line"> 4: iinc          1, 1</span><br><span class="line"> 7: iinc          1, 1</span><br><span class="line">10: iload_1</span><br><span class="line">11: iadd</span><br><span class="line">12: iload_1</span><br><span class="line">13: iinc          1, -1</span><br><span class="line">16: iadd</span><br><span class="line">17: istore_2</span><br></pre></td></tr></table></figure>
+<h5 id="“注册”怎么和锁产生联系？"><a href="#“注册”怎么和锁产生联系？" class="headerlink" title="“注册”怎么和锁产生联系？"></a>“注册”怎么和锁产生联系？</h5><p>但是以上的注册过程只是起到一个“标记”作用，没有涉及和锁相关的代码，那么这个“标记”是怎么和真正的锁产生联系呢？<code>ClassLoader</code> 提供了三个构造器方法：</p>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">private</span> <span class="title function_">ClassLoader</span><span class="params">(Void unused, ClassLoader parent)</span> &#123;</span><br><span class="line">    <span class="comment">// 由 private 修饰，不允许子类重写</span></span><br><span class="line">    <span class="built_in">this</span>.parent = parent;</span><br><span class="line">    <span class="keyword">if</span> (ParallelLoaders.isRegistered(<span class="built_in">this</span>.getClass())) &#123;</span><br><span class="line">        <span class="comment">// 如果类加载器已经注册为具有并行能力，则做一些赋值操作</span></span><br><span class="line">        parallelLockMap = <span class="keyword">new</span> <span class="title class_">ConcurrentHashMap</span>&lt;&gt;();</span><br><span class="line">        <span class="comment">// 保存 package-&gt;certs 的 map 映射，相关的工作也可以并行进行</span></span><br><span class="line">        package2certs = <span class="keyword">new</span> <span class="title class_">ConcurrentHashMap</span>&lt;&gt;();</span><br><span class="line">        assertionLock = <span class="keyword">new</span> <span class="title class_">Object</span>();</span><br><span class="line">    &#125; <span class="keyword">else</span> &#123;</span><br><span class="line">        <span class="comment">// no finer-grained lock; lock on the classloader instance</span></span><br><span class="line">        parallelLockMap = <span class="literal">null</span>;</span><br><span class="line">        package2certs = <span class="keyword">new</span> <span class="title class_">Hashtable</span>&lt;&gt;();</span><br><span class="line">        assertionLock = <span class="built_in">this</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">// 由 protect 修饰，允许子类重写，传递了父·类加载器。</span></span><br><span class="line"><span class="keyword">protected</span> <span class="title function_">ClassLoader</span><span class="params">(ClassLoader parent)</span> &#123;</span><br><span class="line">    <span class="built_in">this</span>(checkCreateClassLoader(), parent);</span><br><span class="line">&#125;</span><br><span class="line"></span><br><span class="line"><span class="comment">// 由 protect 修饰，允许子类重写，父·类加载器使用 getSystemClassLoader 方法返回的系统类加载器。</span></span><br><span class="line"><span class="keyword">protected</span> <span class="title function_">ClassLoader</span><span class="params">()</span> &#123;</span><br><span class="line">    <span class="built_in">this</span>(checkCreateClassLoader(), getSystemClassLoader());</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
 
-<ul>
-<li>a++ 和 ++a 的区别是先 load 还是先 iinc。</li>
-<li>iinc，将局部变量表指定槽位的数加上一个常数。</li>
-<li>注意 a 只 load 到操作数栈并没有 store 回局部变量表。</li>
-<li>b &#x3D; 10 + 12 + 12 &#x3D; 34</li>
-<li>a &#x3D; 10 + 1 + 1 - 1 &#x3D; 11</li>
-</ul>
-<h2 id="分析判断条件"><a href="#分析判断条件" class="headerlink" title="分析判断条件"></a>分析判断条件</h2><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_">ByteCodeTest_4</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="type">int</span> <span class="variable">a</span> <span class="operator">=</span> <span class="number">0</span>;</span><br><span class="line">        <span class="comment">// ifeq, goto</span></span><br><span class="line">        <span class="keyword">if</span> (a == <span class="number">0</span>) &#123;</span><br><span class="line">            a = <span class="number">10</span>;</span><br><span class="line">        &#125; <span class="keyword">else</span> &#123;</span><br><span class="line">            a = <span class="number">20</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><code>ClassLoader</code> 的构造器方法最终都调用 <code>private</code> 修饰的 <code>java.lang.ClassLoader#ClassLoader(java.lang.Void, java.lang.ClassLoader)</code>，又因为父类的构造器方法总是先于子类的构造器方法被执行，这样一来，所有继承 <code>ClassLoader</code> 的类加载器在创建的时候都会根据在创建实例之前是否注册为具有并行能力而做不同的操作。</p>
+<h5 id="为什么注册的代码不能写在构造器方法里？"><a href="#为什么注册的代码不能写在构造器方法里？" class="headerlink" title="为什么注册的代码不能写在构造器方法里？"></a>为什么注册的代码不能写在构造器方法里？</h5><p>使用“注册”的代码也解释了 <code>java.lang.ClassLoader#registerAsParallelCapable</code> 为了满足调用成功的第一个条件为什么不能写在构造器方法中，因为使用这个机制的代码先于你在子类构造器方法里编写的代码被执行。<br>同时，不论是 <code>loadLoader</code> 还是 <code>getClassLoadingLock</code> 都是由 <code>protect</code> 修饰，允许子类重写，来自定义并行加载类的能力。</p>
+<blockquote>
+<p>todo: 讨论自定义类加载器的时候，印象里似乎对并行加载类的提及比较少，之后留意一下。</p>
+</blockquote>
+<h4 id="检查目标类是否已加载"><a href="#检查目标类是否已加载" class="headerlink" title="检查目标类是否已加载"></a>检查目标类是否已加载</h4><p>加载类之前显然需要检查目标类是否已加载，这项工作最终是交给 <code>native</code> 方法，在虚拟机中执行，就像在黑盒中一样。<br>todo: 不同类加载器同一个类名会如何判定？</p>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">protected</span> <span class="keyword">final</span> Class&lt;?&gt; findLoadedClass(String name) &#123;</span><br><span class="line">    <span class="keyword">if</span> (!checkName(name))</span><br><span class="line">        <span class="keyword">return</span> <span class="literal">null</span>;</span><br><span class="line">    <span class="keyword">return</span> findLoadedClass0(name);</span><br><span class="line">&#125;</span><br><span class="line"></span><br><span class="line"><span class="keyword">private</span> <span class="keyword">native</span> <span class="keyword">final</span> Class&lt;?&gt; findLoadedClass0(String name);</span><br></pre></td></tr></table></figure>
 
-<h3 id="字节码指令-2"><a href="#字节码指令-2" class="headerlink" title="字节码指令"></a>字节码指令</h3><figure class="highlight console"><table><tr><td class="code"><pre><span class="line"> 0: iconst_0</span><br><span class="line"> 1: istore_1</span><br><span class="line"> 2: iload_1</span><br><span class="line"> 3: ifne          12</span><br><span class="line"> 6: bipush        10</span><br><span class="line"> 8: istore_1</span><br><span class="line"> 9: goto          15</span><br><span class="line">12: bipush        20</span><br><span class="line">14: istore_1</span><br><span class="line">15: return</span><br></pre></td></tr></table></figure>
+<h4 id="保证核心类库的安全性：双亲委派模型"><a href="#保证核心类库的安全性：双亲委派模型" class="headerlink" title="保证核心类库的安全性：双亲委派模型"></a>保证核心类库的安全性：双亲委派模型</h4><p>正如在代码和注释中所看到的，正常情况下，类的加载工作先委派给自己的父·类加载器，即 <code>parent</code> 属性的值——另一个类加载器实例。一层一层向上委派直到 <code>parent</code> 为 <code>null</code>，代表类加载工作会尝试先委派给虚拟机内建的 <code>bootstrap class loader</code> 处理，然后由 <code>bootstrap class loader</code> 首先尝试加载。如果被委派方加载失败，委派方会自己再尝试加载。<br>正常加载类的是应用类加载器 <code>AppClassLoader</code>，它的 <code>parent</code> 为 <code>ExtClassLoader</code>，<code>ExtClassLoader</code> 的 <code>parent</code> 为 <code>null</code>。</p>
+<blockquote>
+<p>在网上也能看到有人提到以前大家称之为“父·类加载器委派机制”，“双亲”一词易引人误解。</p>
+</blockquote>
+<h5 id="为什么要用这套奇怪的机制"><a href="#为什么要用这套奇怪的机制" class="headerlink" title="为什么要用这套奇怪的机制"></a>为什么要用这套奇怪的机制</h5><p>这样设计很明显的一个目的就是保证核心类库的类加载安全性。比如 <code>Object</code> 类，设计者不希望编写代码的人重新写一个 <code>Object</code> 类并加载到 <code>Java</code> 虚拟机中，但是加载类的本质就是读取字节数据传递给 <code>Java</code> 虚拟机创建一个 <code>Class</code> 实例，使用这套机制的目的之一就是为了让核心类库先加载，同时先加载的类不会再次被加载。</p>
+<p>通常流程如下：</p>
+<ol>
+<li><code>AppClassLoader</code> 调用 <code>loadClass</code> 方法，先委派给 <code>ExtClassLoader</code>。</li>
+<li><code>ExtClassLoader</code> 调用 <code>loadClass</code> 方法，先委派给 <code>bootstrap class loader</code>。</li>
+<li><code>bootstrap class loader</code> 在其设置的类路径中无法找到 <code>BananaTest</code> 类，抛出 <code>ClassNotFoundException</code> 异常。</li>
+<li><code>ExtClassLoader</code> 捕获异常，然后自己调用 <code>findClass</code> 方法尝试进行加载。</li>
+<li><code>ExtClassLoader</code> 在其设置的类路径中无法找到 <code>BananaTest</code> 类，抛出 <code>ClassNotFoundException</code> 异常。</li>
+<li><code>AppClassLoader</code> 捕获异常，然后自己调用 <code>findClass</code> 方法尝试进行加载。</li>
+</ol>
+<p>注释中提到鼓励重写 <code>findClass</code> 方法而不是 <code>loadClass</code>，因为正是该方法实现了所谓的“双亲委派模型”，<code>java.lang.ClassLoader#findClass</code> 实现了如何查找加载类。如果不是专门为了破坏这个类加载模型，应该选择重写 <code>findClass</code>；其次是因为该方法中涉及并行加载类的机制。</p>
+<h3 id="查找类资源：findClass"><a href="#查找类资源：findClass" class="headerlink" title="查找类资源：findClass"></a>查找类资源：findClass</h3><p>默认情况下，类加载器在自己尝试进行加载时，会调用 <code>java.lang.ClassLoader#findClass</code> 方法，该方法由子类重写。<code>AppClassLoader</code> 和 <code>ExtClassLoader</code> 都是继承 <code>URLClassLoader</code>，而 <code>URLClassLoader</code> 重写了 <code>findClass</code> 方法。根据注释可知，该方法会从 <code>URL</code> 搜索路径查找并加载具有指定名称的类。任何引用 <code>Jar</code> 文件的 <code>URL</code> 都会根据需要加载并打开，直到找到该类。</p>
+<p>过程如下：</p>
+<ol>
+<li>将 <code>name</code> 转换为 <code>path</code>，比如 <code>com.example.BananaTest</code> 转换为 <code>com/example/BananaTest.class</code>。</li>
+<li>使用 <code>URL</code> 搜索路径 <code>URLClassPath</code> 和 <code>path</code> 中获取 <code>Resource</code>，本质上就是轮流将可能存放的目录列表拼接上文件路径进行查找。</li>
+<li>调用 <code>URLClassLoader</code> 的私有方法 <code>defineClass</code>，该方法调用父类 <code>SecureClassLoader</code> 的 <code>defineClass</code> 方法。</li>
+</ol>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">protected</span> Class&lt;?&gt; findClass(<span class="keyword">final</span> String name)</span><br><span class="line">    <span class="keyword">throws</span> ClassNotFoundException</span><br><span class="line">&#123;</span><br><span class="line">    <span class="keyword">final</span> Class&lt;?&gt; result;</span><br><span class="line">    <span class="keyword">try</span> &#123;</span><br><span class="line">        <span class="comment">// todo:</span></span><br><span class="line">        result = AccessController.doPrivileged(</span><br><span class="line">            <span class="keyword">new</span> <span class="title class_">PrivilegedExceptionAction</span>&lt;Class&lt;?&gt;&gt;() &#123;</span><br><span class="line">                <span class="keyword">public</span> Class&lt;?&gt; run() <span class="keyword">throws</span> ClassNotFoundException &#123;</span><br><span class="line">                    <span class="comment">// 将 name 转换为 path</span></span><br><span class="line">                    <span class="type">String</span> <span class="variable">path</span> <span class="operator">=</span> name.replace(<span class="string">&#x27;.&#x27;</span>, <span class="string">&#x27;/&#x27;</span>).concat(<span class="string">&quot;.class&quot;</span>);</span><br><span class="line">                    <span class="comment">// 从 URLClassPath 中查找 Resource</span></span><br><span class="line">                    <span class="type">Resource</span> <span class="variable">res</span> <span class="operator">=</span> ucp.getResource(path, <span class="literal">false</span>);</span><br><span class="line">                    <span class="keyword">if</span> (res != <span class="literal">null</span>) &#123;</span><br><span class="line">                        <span class="keyword">try</span> &#123;</span><br><span class="line">                            <span class="keyword">return</span> defineClass(name, res);</span><br><span class="line">                        &#125; <span class="keyword">catch</span> (IOException e) &#123;</span><br><span class="line">                            <span class="keyword">throw</span> <span class="keyword">new</span> <span class="title class_">ClassNotFoundException</span>(name, e);</span><br><span class="line">                        &#125; <span class="keyword">catch</span> (ClassFormatError e2) &#123;</span><br><span class="line">                            <span class="keyword">if</span> (res.getDataError() != <span class="literal">null</span>) &#123;</span><br><span class="line">                                e2.addSuppressed(res.getDataError());</span><br><span class="line">                            &#125;</span><br><span class="line">                            <span class="keyword">throw</span> e2;</span><br><span class="line">                        &#125;</span><br><span class="line">                    &#125; <span class="keyword">else</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">                &#125;</span><br><span class="line">            &#125;, acc);</span><br><span class="line">    &#125; <span class="keyword">catch</span> (java.security.PrivilegedActionException pae) &#123;</span><br><span class="line">        <span class="keyword">throw</span> (ClassNotFoundException) pae.getException();</span><br><span class="line">    &#125;</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">throw</span> <span class="keyword">new</span> <span class="title class_">ClassNotFoundException</span>(name);</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="keyword">return</span> result;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
 
-<ul>
-<li>iconst，将一个 int 常量推入操作数栈。</li>
-<li>if<code>&lt;cond&gt;</code>，一个 int 和 0 的比较成立时进入分支，跳转到指定行号。</li>
-<li>goto，总是进入的分支，跳转到指定行号。</li>
-</ul>
-<h2 id="涉及的字节码指令"><a href="#涉及的字节码指令" class="headerlink" title="涉及的字节码指令"></a>涉及的字节码指令</h2><ul>
-<li>bipush，将一个 byte 符号扩展为一个 int，推入操作数栈。</li>
-<li>istore，将栈顶的 int，存入局部变量表的指定槽位。</li>
-<li>iload，将局部变量表指定槽位的 int，推入操作数栈。</li>
-<li>ldc，从运行时常量池将指定常量推入操作数栈。</li>
-<li>iadd，将栈顶的两个 int 弹出并相加，将结果推入操作数栈。</li>
-<li>getstatic，获取类的静态属性，推入操作数栈。</li>
-<li>invokevirtual，将栈顶的参数依次弹出，调用实例方法。</li>
-<li>return，返回 void。</li>
-<li>iinc，将局部变量表中指定槽位的数加一个常量。</li>
-<li>if<code>&lt;cond&gt;</code>，一个 int 和 0 的比较成立时进入分支，跳转到指定行号。<ul>
-<li>ifeq，equals</li>
-<li>ifne，not equals</li>
-<li>iflt，less than</li>
-<li>ifge，greater than or equals</li>
-<li>ifgt，great than</li>
-<li>ifle，less than or equals</li>
-</ul>
-</li>
-<li>goto，总是进入的分支，跳转到指定行号。</li>
-</ul>
-]]></content>
-      <tags>
-        <tag>java</tag>
-        <tag>bytecode</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">
+<h4 id="查找类的目录列表：URLClassPath"><a href="#查找类的目录列表：URLClassPath" class="headerlink" title="查找类的目录列表：URLClassPath"></a>查找类的目录列表：URLClassPath</h4><p><code>URLClassLoader</code> 拥有一个 <code>URLClassPath</code> 类型的属性 <code>ucp</code>。由注释可知，<code>URLClassPath</code> 类用于维护一个 <code>URL</code> 的搜索路径，以便从 <code>Jar</code> 文件和目录中加载类和资源。<br><code>URLClassPath</code> 的核心构造器方法：</p>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="title function_">URLClassPath</span><span class="params">(URL[] urls,</span></span><br><span class="line"><span class="params">                    URLStreamHandlerFactory factory,</span></span><br><span class="line"><span class="params">                    AccessControlContext acc)</span> &#123;</span><br><span class="line">    <span class="comment">// 将 urls 保存到 ArrayList 类型的属性 path 中，根据注释，path 的含义为 URL 的原始搜索路径。</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; urls.length; i++) &#123;</span><br><span class="line">        path.add(urls[i]);</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="comment">// 将 urls 保存到 Stack 类型的属性 urls 中，根据注释，urls 的含义为未打开的 URL 列表。</span></span><br><span class="line">    push(urls);</span><br><span class="line">    <span class="keyword">if</span> (factory != <span class="literal">null</span>) &#123;</span><br><span class="line">        <span class="comment">// 如果 factory 不为 null，使用它创建一个 URLStreamHandler 实例处理 Jar 文件。</span></span><br><span class="line">        jarHandler = factory.createURLStreamHandler(<span class="string">&quot;jar&quot;</span>);</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="keyword">if</span> (DISABLE_ACC_CHECKING)</span><br><span class="line">        <span class="built_in">this</span>.acc = <span class="literal">null</span>;</span><br><span class="line">    <span class="keyword">else</span></span><br><span class="line">        <span class="built_in">this</span>.acc = acc;</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>
+<h5 id="URLClassPath-getResource"><a href="#URLClassPath-getResource" class="headerlink" title="URLClassPath#getResource"></a>URLClassPath#getResource</h5><p><code>URLClassLoader</code> 调用 <code>sun.misc.URLClassPath#getResource(java.lang.String, boolean)</code> 方法获取指定名称对应的资源。根据注释，该方法会查找 <code>URL</code> 搜索路径上的第一个资源，如果找不到资源，则返回 <code>null</code>。<br>显然，这里的 <code>Loader</code> 不是我们前面提到的类加载器。<code>Loader</code> 是 <code>URLClassPath</code> 的内部类，用于表示根据一个基本 <code>URL</code> 创建的资源和类的加载器。也就是说一个基本 <code>URL</code> 对应一个 <code>Loader</code>。</p>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> Resource <span class="title function_">getResource</span><span class="params">(String name, <span class="type">boolean</span> check)</span> &#123;</span><br><span class="line">    <span class="keyword">if</span> (DEBUG) &#123;</span><br><span class="line">        System.err.println(<span class="string">&quot;URLClassPath.getResource(\&quot;&quot;</span> + name + <span class="string">&quot;\&quot;)&quot;</span>);</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    Loader loader;</span><br><span class="line">    <span class="comment">// 获取缓存（默认没有用）</span></span><br><span class="line">    <span class="type">int</span>[] cache = getLookupCache(name);</span><br><span class="line">    <span class="comment">// 不断获取下一个 Loader 来获取 Resource，直到获取到或者没有下一个 Loader</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>; (loader = getNextLoader(cache, i)) != <span class="literal">null</span>; i++) &#123;</span><br><span class="line">        <span class="type">Resource</span> <span class="variable">res</span> <span class="operator">=</span> loader.getResource(name, check);</span><br><span class="line">        <span class="keyword">if</span> (res != <span class="literal">null</span>) &#123;</span><br><span class="line">            <span class="keyword">return</span> res;</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>
 
-<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">
+<h5 id="URLClassPath-getNextLoader"><a href="#URLClassPath-getNextLoader" class="headerlink" title="URLClassPath#getNextLoader"></a>URLClassPath#getNextLoader</h5><p>获取下一个 <code>Loader</code>，其实根据 <code>index</code> 从一个存放已创建 <code>Loader</code> 的 <code>ArrayList</code> 中获取。</p>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">private</span> <span class="keyword">synchronized</span> Loader <span class="title function_">getNextLoader</span><span class="params">(<span class="type">int</span>[] cache, <span class="type">int</span> index)</span> &#123;</span><br><span class="line">    <span class="keyword">if</span> (closed) &#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">if</span> (cache != <span class="literal">null</span>) &#123;</span><br><span class="line">        <span class="keyword">if</span> (index &lt; cache.length) &#123;</span><br><span class="line">            <span class="type">Loader</span> <span class="variable">loader</span> <span class="operator">=</span> loaders.get(cache[index]);</span><br><span class="line">            <span class="keyword">if</span> (DEBUG_LOOKUP_CACHE) &#123;</span><br><span class="line">                System.out.println(<span class="string">&quot;HASCACHE: Loading from : &quot;</span> + cache[index]</span><br><span class="line">                                    + <span class="string">&quot; = &quot;</span> + loader.getBaseURL());</span><br><span class="line">            &#125;</span><br><span class="line">            <span class="keyword">return</span> loader;</span><br><span class="line">        &#125; <span class="keyword">else</span> &#123;</span><br><span class="line">            <span class="keyword">return</span> <span class="literal">null</span>; <span class="comment">// finished iterating over cache[]</span></span><br><span class="line">        &#125;</span><br><span class="line">    &#125; <span class="keyword">else</span> &#123;</span><br><span class="line">        <span class="comment">// 获取 Loader</span></span><br><span class="line">        <span class="keyword">return</span> getLoader(index);</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>
+<h5 id="URLClassPath-getLoader-int"><a href="#URLClassPath-getLoader-int" class="headerlink" title="URLClassPath#getLoader(int)"></a>URLClassPath#getLoader(int)</h5><ol>
+<li>用 <code>index</code> 到存放已创建 <code>Loader</code> 的列表中去获取（调用方传入的 <code>index</code> 从 <code>0</code> 开始不断递增直到超过范围）。</li>
+<li>如果 <code>index</code> 超过范围，说明已有的 <code>Loader</code> 都找不到目标 <code>Resource</code>，需要到未打开的 <code>URL</code> 中查找。</li>
+<li>从未打开的 <code>URL</code> 中取出（<code>pop</code>）一个来创建 <code>Loader</code>，如果 <code>urls</code> 已经为空，则返回 <code>null</code>。</li>
+</ol>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">private</span> <span class="keyword">synchronized</span> Loader <span class="title function_">getLoader</span><span class="params">(<span class="type">int</span> index)</span> &#123;</span><br><span class="line">    <span class="keyword">if</span> (closed) &#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="comment">// Expand URL search path until the request can be satisfied</span></span><br><span class="line">    <span class="comment">// or the URL stack is empty.</span></span><br><span class="line">    <span class="keyword">while</span> (loaders.size() &lt; index + <span class="number">1</span>) &#123;</span><br><span class="line">        <span class="comment">// Pop the next URL from the URL stack</span></span><br><span class="line">        <span class="comment">// 如果 index 超过数组范围，需要从未打开的 URL 中取出一个，创建 Loader 并返回</span></span><br><span class="line">        URL url;</span><br><span class="line">        <span class="keyword">synchronized</span> (urls) &#123;</span><br><span class="line">            <span class="keyword">if</span> (urls.empty()) &#123;</span><br><span class="line">                <span class="keyword">return</span> <span class="literal">null</span>;</span><br><span class="line">            &#125; <span class="keyword">else</span> &#123;</span><br><span class="line">                url = urls.pop();</span><br><span class="line">            &#125;</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="comment">// Skip this URL if it already has a Loader. (Loader</span></span><br><span class="line">        <span class="comment">// may be null in the case where URL has not been opened</span></span><br><span class="line">        <span class="comment">// but is referenced by a JAR index.)</span></span><br><span class="line">        <span class="type">String</span> <span class="variable">urlNoFragString</span> <span class="operator">=</span> URLUtil.urlNoFragString(url);</span><br><span class="line">        <span class="keyword">if</span> (lmap.containsKey(urlNoFragString)) &#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">// Otherwise, create a new Loader for the URL.</span></span><br><span class="line">        Loader loader;</span><br><span class="line">        <span class="keyword">try</span> &#123;</span><br><span class="line">            <span class="comment">// 根据 URL 创建 Loader</span></span><br><span class="line">            loader = getLoader(url);</span><br><span class="line">            <span class="comment">// If the loader defines a local class path then add the</span></span><br><span class="line">            <span class="comment">// URLs to the list of URLs to be opened.</span></span><br><span class="line">            URL[] urls = loader.getClassPath();</span><br><span class="line">            <span class="keyword">if</span> (urls != <span class="literal">null</span>) &#123;</span><br><span class="line">                push(urls);</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">            <span class="comment">// Silently ignore for now...</span></span><br><span class="line">            <span class="keyword">continue</span>;</span><br><span class="line">        &#125; <span class="keyword">catch</span> (SecurityException se) &#123;</span><br><span class="line">            <span class="comment">// Always silently ignore. The context, if there is one, that</span></span><br><span class="line">            <span class="comment">// this URLClassPath was given during construction will never</span></span><br><span class="line">            <span class="comment">// have permission to access the URL.</span></span><br><span class="line">            <span class="keyword">if</span> (DEBUG) &#123;</span><br><span class="line">                System.err.println(<span class="string">&quot;Failed to access &quot;</span> + url + <span class="string">&quot;, &quot;</span> + se );</span><br><span class="line">            &#125;</span><br><span class="line">            <span class="keyword">continue</span>;</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="comment">// Finally, add the Loader to the search path.</span></span><br><span class="line">        validateLookupCache(loaders.size(), urlNoFragString);</span><br><span class="line">        loaders.add(loader);</span><br><span class="line">        lmap.put(urlNoFragString, loader);</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="keyword">if</span> (DEBUG_LOOKUP_CACHE) &#123;</span><br><span class="line">        System.out.println(<span class="string">&quot;NOCACHE: Loading from : &quot;</span> + index );</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="keyword">return</span> loaders.get(index);</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">
+<h5 id="URLClassPath-getLoader-java-net-URL"><a href="#URLClassPath-getLoader-java-net-URL" class="headerlink" title="URLClassPath#getLoader(java.net.URL)"></a>URLClassPath#getLoader(java.net.URL)</h5><p>根据指定的 <code>URL</code> 创建 <code>Loader</code>，不同类型的 <code>URL</code> 会返回不同具体实现的 <code>Loader</code>。</p>
+<ol>
+<li>如果 <code>URL</code> 不是以 <code>/</code> 结尾，认为是 <code>Jar</code> 文件，则返回 <code>JarLoader</code> 类型，比如 <code>file:/C:/Users/xxx/.jdks/corretto-1.8.0_342/jre/lib/rt.jar</code>。</li>
+<li>如果 <code>URL</code> 以 <code>/</code> 结尾，且协议为 <code>file</code>，则返回 <code>FileLoader</code> 类型，比如 <code>file:/C:/Users/xxx/IdeaProjects/java-test/target/classes/</code>。</li>
+<li>如果 <code>URL</code> 以 <code>/</code> 结尾，且协议不会 <code>file</code>，则返回 <code>Loader</code> 类型。</li>
+</ol>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">private</span> Loader <span class="title function_">getLoader</span><span class="params">(<span class="keyword">final</span> URL url)</span> <span class="keyword">throws</span> IOException &#123;</span><br><span class="line">    <span class="keyword">try</span> &#123;</span><br><span class="line">        <span class="keyword">return</span> java.security.AccessController.doPrivileged(</span><br><span class="line">            <span class="keyword">new</span> <span class="title class_">java</span>.security.PrivilegedExceptionAction&lt;Loader&gt;() &#123;</span><br><span class="line">            <span class="keyword">public</span> Loader <span class="title function_">run</span><span class="params">()</span> <span class="keyword">throws</span> IOException &#123;</span><br><span class="line">                <span class="type">String</span> <span class="variable">file</span> <span class="operator">=</span> url.getFile();</span><br><span class="line">                <span class="keyword">if</span> (file != <span class="literal">null</span> &amp;&amp; file.endsWith(<span class="string">&quot;/&quot;</span>)) &#123;</span><br><span class="line">                    <span class="keyword">if</span> (<span class="string">&quot;file&quot;</span>.equals(url.getProtocol())) &#123;</span><br><span class="line">                        <span class="keyword">return</span> <span class="keyword">new</span> <span class="title class_">FileLoader</span>(url);</span><br><span class="line">                    &#125; <span class="keyword">else</span> &#123;</span><br><span class="line">                        <span class="keyword">return</span> <span class="keyword">new</span> <span class="title class_">Loader</span>(url);</span><br><span class="line">                    &#125;</span><br><span class="line">                &#125; <span class="keyword">else</span> &#123;</span><br><span class="line">                    <span class="keyword">return</span> <span class="keyword">new</span> <span class="title class_">JarLoader</span>(url, jarHandler, lmap, acc);</span><br><span class="line">                &#125;</span><br><span class="line">            &#125;</span><br><span class="line">        &#125;, acc);</span><br><span class="line">    &#125; <span class="keyword">catch</span> (java.security.PrivilegedActionException pae) &#123;</span><br><span class="line">        <span class="keyword">throw</span> (IOException)pae.getException();</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</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="URLClassPath-FileLoader-getResource"><a href="#URLClassPath-FileLoader-getResource" class="headerlink" title="URLClassPath.FileLoader#getResource"></a>URLClassPath.FileLoader#getResource</h4><p>以 <code>FileLoader</code> 的 <code>getResource</code> 为例，如果文件找到了，就会将文件包装成一个 <code>FileInputStream</code>，再将 <code>FileInputStream</code> 包装成一个 <code>Resource</code> 返回。</p>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line">Resource <span class="title function_">getResource</span><span class="params">(<span class="keyword">final</span> String name, <span class="type">boolean</span> check)</span> &#123;</span><br><span class="line">    <span class="keyword">final</span> URL url;</span><br><span class="line">    <span class="keyword">try</span> &#123;</span><br><span class="line">        <span class="type">URL</span> <span class="variable">normalizedBase</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">URL</span>(getBaseURL(), <span class="string">&quot;.&quot;</span>);</span><br><span class="line">        url = <span class="keyword">new</span> <span class="title class_">URL</span>(getBaseURL(), ParseUtil.encodePath(name, <span class="literal">false</span>));</span><br><span class="line"></span><br><span class="line">        <span class="keyword">if</span> (url.getFile().startsWith(normalizedBase.getFile()) == <span class="literal">false</span>) &#123;</span><br><span class="line">            <span class="comment">// requested resource had ../..&#x27;s in path</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"></span><br><span class="line">        <span class="keyword">if</span> (check)</span><br><span class="line">            URLClassPath.check(url);</span><br><span class="line"></span><br><span class="line">        <span class="keyword">final</span> File file;</span><br><span class="line">        <span class="keyword">if</span> (name.indexOf(<span class="string">&quot;..&quot;</span>) != -<span class="number">1</span>) &#123;</span><br><span class="line">            file = (<span class="keyword">new</span> <span class="title class_">File</span>(dir, name.replace(<span class="string">&#x27;/&#x27;</span>, File.separatorChar)))</span><br><span class="line">                    .getCanonicalFile();</span><br><span class="line">            <span class="keyword">if</span> ( !((file.getPath()).startsWith(dir.getPath())) ) &#123;</span><br><span class="line">                <span class="comment">/* outside of base dir */</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 class="keyword">else</span> &#123;</span><br><span class="line">            file = <span class="keyword">new</span> <span class="title class_">File</span>(dir, name.replace(<span class="string">&#x27;/&#x27;</span>, File.separatorChar));</span><br><span class="line">        &#125;</span><br><span class="line"></span><br><span class="line">        <span class="keyword">if</span> (file.exists()) &#123;</span><br><span class="line">            <span class="keyword">return</span> <span class="keyword">new</span> <span class="title class_">Resource</span>() &#123;</span><br><span class="line">                <span class="keyword">public</span> String <span class="title function_">getName</span><span class="params">()</span> &#123; <span class="keyword">return</span> name; &#125;;</span><br><span class="line">                <span class="keyword">public</span> URL <span class="title function_">getURL</span><span class="params">()</span> &#123; <span class="keyword">return</span> url; &#125;;</span><br><span class="line">                <span class="keyword">public</span> URL <span class="title function_">getCodeSourceURL</span><span class="params">()</span> &#123; <span class="keyword">return</span> getBaseURL(); &#125;;</span><br><span class="line">                <span class="keyword">public</span> InputStream <span class="title function_">getInputStream</span><span class="params">()</span> <span class="keyword">throws</span> IOException</span><br><span class="line">                    &#123; <span class="keyword">return</span> <span class="keyword">new</span> <span class="title class_">FileInputStream</span>(file); &#125;;</span><br><span class="line">                <span class="keyword">public</span> <span class="type">int</span> <span class="title function_">getContentLength</span><span class="params">()</span> <span class="keyword">throws</span> IOException</span><br><span class="line">                    &#123; <span class="keyword">return</span> (<span class="type">int</span>)file.length(); &#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">        <span class="keyword">return</span> <span class="literal">null</span>;</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>
 
-<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>
+<h4 id="ClassLoader-的搜索路径"><a href="#ClassLoader-的搜索路径" class="headerlink" title="ClassLoader 的搜索路径"></a>ClassLoader 的搜索路径</h4><p>从上文可知，<code>ClassLoader</code> 调用 <code>findClass</code> 方法查找类的时候，并不是漫无目的地查找，而是根据设置的类路径进行查找，不同的 <code>ClassLoader</code> 有不同的类路径。</p>
+<p>以下是通过 <code>IDEA</code> 启动 <code>Java</code> 程序时的命令，可以看到其中通过 <code>-classpath</code> 指定了应用·类加载器 <code>AppClassLoader</code> 的类路径，该类路径除了包含常规的 <code>JRE</code> 的文件路径外，还额外添加了当前 <code>maven</code> 工程编译生成的 <code>target\classes</code> 目录。</p>
+<figure class="highlight shell"><table><tr><td class="code"><pre><span class="line">C:\Users\xxx\.jdks\corretto-1.8.0_342\bin\java.exe -agentlib:jdwp=transport=dt_socket,address=127.0.0.1:52959,suspend=y,server=n -javaagent:C:\Users\xxx\AppData\Local\JetBrains\IntelliJIdea2022.3\captureAgent\debugger-agent.jar -Dfile.encoding=UTF-8 -classpath &quot;C:\Users\xxx\.jdks\corretto-1.8.0_342\jre\lib\charsets.jar;C:\Users\xxx\.jdks\corretto-1.8.0_342\jre\lib\ext\access-bridge-64.jar;C:\Users\xxx\.jdks\corretto-1.8.0_342\jre\lib\ext\cldrdata.jar;C:\Users\xxx\.jdks\corretto-1.8.0_342\jre\lib\ext\dnsns.jar;C:\Users\xxx\.jdks\corretto-1.8.0_342\jre\lib\ext\jaccess.jar;C:\Users\xxx\.jdks\corretto-1.8.0_342\jre\lib\ext\jfxrt.jar;C:\Users\xxx\.jdks\corretto-1.8.0_342\jre\lib\ext\localedata.jar;C:\Users\xxx\.jdks\corretto-1.8.0_342\jre\lib\ext\nashorn.jar;C:\Users\xxx\.jdks\corretto-1.8.0_342\jre\lib\ext\sunec.jar;C:\Users\xxx\.jdks\corretto-1.8.0_342\jre\lib\ext\sunjce_provider.jar;C:\Users\xxx\.jdks\corretto-1.8.0_342\jre\lib\ext\sunmscapi.jar;C:\Users\xxx\.jdks\corretto-1.8.0_342\jre\lib\ext\sunpkcs11.jar;C:\Users\xxx\.jdks\corretto-1.8.0_342\jre\lib\ext\zipfs.jar;C:\Users\xxx\.jdks\corretto-1.8.0_342\jre\lib\jce.jar;C:\Users\xxx\.jdks\corretto-1.8.0_342\jre\lib\jfr.jar;C:\Users\xxx\.jdks\corretto-1.8.0_342\jre\lib\jfxswt.jar;C:\Users\xxx\.jdks\corretto-1.8.0_342\jre\lib\jsse.jar;C:\Users\xxx\.jdks\corretto-1.8.0_342\jre\lib\management-agent.jar;C:\Users\xxx\.jdks\corretto-1.8.0_342\jre\lib\resources.jar;C:\Users\xxx\.jdks\corretto-1.8.0_342\jre\lib\rt.jar;C:\Users\xxx\IdeaProjects\java-test\target\classes;C:\Program Files\JetBrains\IntelliJ IDEA 2022.3.3\lib\idea_rt.jar&quot; org.example.BananaTest</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>
+<h5 id="bootstrap-class-loader"><a href="#bootstrap-class-loader" class="headerlink" title="bootstrap class loader"></a>bootstrap class loader</h5><p>启动·类加载器 <code>bootstrap class loader</code>，加载核心类库，即 <code>&lt;JRE_HOME&gt;/lib</code> 目录中的部分类库，如 <code>rt.jar</code>，只有名字符合要求的 <code>jar</code> 才能被识别。 启动 Java 虚拟机时可以通过选项 <code>-Xbootclasspath</code> 修改默认的类路径，有三种使用方式：</p>
+<ul>
+<li><code>-Xbootclasspath:</code>：完全覆盖核心类库的类路径，不常用，除非重写核心类库。</li>
+<li><code>-Xbootclasspath/a:</code> 以后缀的方式拼接在原搜索路径后面，常用。</li>
+<li><code>-Xbootclasspath/p:</code> 以前缀的方式拼接再原搜索路径前面.不常用，避免引起不必要的冲突。</li>
+</ul>
+<p>在 <code>IDEA</code> 中编辑启动配置，添加 <code>VM</code> 选项，<code>-Xbootclasspath:C:\Software</code>，里面没有类文件，启动虚拟机失败，提示：</p>
+<figure class="highlight shell"><table><tr><td class="code"><pre><span class="line">Error occurred during initialization of VM</span><br><span class="line">java/lang/NoClassDefFoundError: java/lang/Object</span><br><span class="line"></span><br><span class="line">进程已结束,退出代码1</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">
+<h5 id="ExtClassLoader"><a href="#ExtClassLoader" class="headerlink" title="ExtClassLoader"></a>ExtClassLoader</h5><p>扩展·类加载器 <code>ExtClassLoader</code>，加载 <code>&lt;JRE_HOME&gt;/lib/ext/</code> 目录中的类库。启动 <code>Java</code> 虚拟机时可以通过选项 <code>-Djava.ext.dirs</code> 修改默认的类路径。显然修改不当同样可能会引起 <code>Java</code> 程序的异常。</p>
+<h5 id="AppClassLoader"><a href="#AppClassLoader" class="headerlink" title="AppClassLoader"></a>AppClassLoader</h5><p>应用·类加载器 <code>AppClassLoader</code> ，加载应用级别的搜索路径中的类库。可以使用系统的环境变量 <code>CLASSPATH</code> 的值，也可以在启动 Java 虚拟机时通过选项 <code>-classpath</code> 修改。</p>
+<p><code>CLASSPATH</code> 在 <code>Windows</code> 中，多个文件路径使用分号 <code>;</code> 分隔，而 <code>Linux</code> 中则使用冒号 <code>:</code> 分隔。以下例子表示当前目录和另一个文件路径拼接而成的类路径。</p>
+<ul>
+<li>Windows：<code>.;C:\path\to\classes</code></li>
+<li>Linux：<code>.:/path/to/classes</code></li>
+</ul>
+<p>事实上，<code>AppClassLoader</code> 最终的类路径，不仅仅包含 <code>-classpath</code> 的值，还会包含 <code>-javaagent</code> 指定的值。</p>
+<h3 id="字节数据转换为-Class-实例：defineClass"><a href="#字节数据转换为-Class-实例：defineClass" class="headerlink" title="字节数据转换为 Class 实例：defineClass"></a>字节数据转换为 Class 实例：defineClass</h3><p>方法 <code>defineClass</code>，顾名思义，就是定义类，将字节数据转换为 <code>Class</code> 实例。在 <code>ClassLoader</code> 以及其子类中有很多同名方法，方法内各种处理和包装，最终都是为了使用 <code>name</code> 和字节数据等参数，调用 <code>native</code> 方法获得一个 <code>Class</code> 实例。<br>以下是定义类时最终可能调用的 <code>native</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">native</span> Class&lt;?&gt; defineClass0(String name, <span class="type">byte</span>[] b, <span class="type">int</span> off, <span class="type">int</span> len,</span><br><span class="line">                                     ProtectionDomain pd);</span><br><span class="line"></span><br><span class="line"><span class="keyword">private</span> <span class="keyword">native</span> Class&lt;?&gt; defineClass1(String name, <span class="type">byte</span>[] b, <span class="type">int</span> off, <span class="type">int</span> len,</span><br><span class="line">                                     ProtectionDomain pd, String source);</span><br><span class="line"></span><br><span class="line"><span class="keyword">private</span> <span class="keyword">native</span> Class&lt;?&gt; defineClass2(String name, java.nio.ByteBuffer b,</span><br><span class="line">                                     <span class="type">int</span> off, <span class="type">int</span> len, ProtectionDomain pd,</span><br><span class="line">                                     String source);</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>其方法参数有：</p>
+<ul>
+<li><code>name</code>，目标类的名称。</li>
+<li><code>byte[]</code> 或 <code>ByteBuffer</code> 类型的字节数据，<code>off</code> 和 <code>len</code> 只是为了定位传入的字节数组中关于目标类的字节数据，通常分别是 0 和字节数组的长度，毕竟专门构造一个包含无关数据的字节数组很无聊。</li>
+<li><code>ProtectionDomain</code>，保护域，todo:</li>
+<li><code>source</code>，<code>CodeSource</code> 的位置。</li>
+</ul>
+<p><code>defineClass</code> 方法的调用过程，其实就是从 <code>URLClassLoader</code> 开始，一层一层处理后再调用父类的 <code>defineClass</code> 方法，分别经过了 <code>SecureClassLoader</code> 和 <code>ClassLoader</code>。</p>
+<h4 id="URLClassLoader-defineClass"><a href="#URLClassLoader-defineClass" class="headerlink" title="URLClassLoader#defineClass"></a>URLClassLoader#defineClass</h4><p>此方法是再 <code>URLClassLoader</code> 的 <code>findClass</code> 方法中，获得正确的 <code>Resource</code> 之后调用的，由 <code>private</code> 修饰。根据注释，它使用从指定资源获取的类字节来定义类，生成的类必须先解析才能使用。</p>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">private</span> Class&lt;?&gt; defineClass(String name, Resource res) <span class="keyword">throws</span> IOException &#123;</span><br><span class="line">    <span class="type">long</span> <span class="variable">t0</span> <span class="operator">=</span> System.nanoTime();</span><br><span class="line">    <span class="comment">// 获取最后一个 . 的位置</span></span><br><span class="line">    <span class="type">int</span> <span class="variable">i</span> <span class="operator">=</span> name.lastIndexOf(<span class="string">&#x27;.&#x27;</span>);</span><br><span class="line">    <span class="comment">// 返回资源的 CodeSourceURL</span></span><br><span class="line">    <span class="type">URL</span> <span class="variable">url</span> <span class="operator">=</span> res.getCodeSourceURL();</span><br><span class="line">    <span class="keyword">if</span> (i != -<span class="number">1</span>) &#123;</span><br><span class="line">        <span class="comment">// 截取包名 com.example</span></span><br><span class="line">        <span class="type">String</span> <span class="variable">pkgname</span> <span class="operator">=</span> name.substring(<span class="number">0</span>, i);</span><br><span class="line">        <span class="comment">// Check if package already loaded.</span></span><br><span class="line">        <span class="type">Manifest</span> <span class="variable">man</span> <span class="operator">=</span> res.getManifest();</span><br><span class="line">        definePackageInternal(pkgname, man, url);</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="comment">// Now read the class bytes and define the class</span></span><br><span class="line">    <span class="comment">// 先尝试以 ByteBuffer 的形式返回字节数据，如果资源的输入流不是在 ByteBuffer 之上实现的，则返回 null</span></span><br><span class="line">    java.nio.<span class="type">ByteBuffer</span> <span class="variable">bb</span> <span class="operator">=</span> res.getByteBuffer();</span><br><span class="line">    <span class="keyword">if</span> (bb != <span class="literal">null</span>) &#123;</span><br><span class="line">        <span class="comment">// Use (direct) ByteBuffer:</span></span><br><span class="line">        <span class="comment">// 不常用</span></span><br><span class="line">        CodeSigner[] signers = res.getCodeSigners();</span><br><span class="line">        <span class="type">CodeSource</span> <span class="variable">cs</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">CodeSource</span>(url, signers);</span><br><span class="line">        sun.misc.PerfCounter.getReadClassBytesTime().addElapsedTimeFrom(t0);</span><br><span class="line">        <span class="comment">// 调用 java.security.SecureClassLoader#defineClass(java.lang.String, java.nio.ByteBuffer, java.security.CodeSource)</span></span><br><span class="line">        <span class="keyword">return</span> defineClass(name, bb, cs);</span><br><span class="line">    &#125; <span class="keyword">else</span> &#123;</span><br><span class="line">        <span class="comment">// 以字节数组的形式返回资源数据</span></span><br><span class="line">        <span class="type">byte</span>[] b = res.getBytes();</span><br><span class="line">        <span class="comment">// must read certificates AFTER reading bytes.</span></span><br><span class="line">        <span class="comment">// 必须再读取字节数据后读取证书，todo:</span></span><br><span class="line">        CodeSigner[] signers = res.getCodeSigners();</span><br><span class="line">        <span class="comment">// 根据 URL 和签名者创建 CodeSource</span></span><br><span class="line">        <span class="type">CodeSource</span> <span class="variable">cs</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">CodeSource</span>(url, signers);</span><br><span class="line">        sun.misc.PerfCounter.getReadClassBytesTime().addElapsedTimeFrom(t0);</span><br><span class="line">        <span class="comment">// 调用 java.security.SecureClassLoader#defineClass(java.lang.String, byte[], int, int, java.security.CodeSource)</span></span><br><span class="line">        <span class="keyword">return</span> defineClass(name, b, <span class="number">0</span>, b.length, cs);</span><br><span class="line">    &#125;</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><code>Resource</code> 类提供了 <code>getBytes</code> 方法，此方法以字节数组的形式返回字节数据。</p>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="type">byte</span>[] getBytes() <span class="keyword">throws</span> IOException &#123;</span><br><span class="line">    <span class="type">byte</span>[] b;</span><br><span class="line">    <span class="comment">// Get stream before content length so that a FileNotFoundException</span></span><br><span class="line">    <span class="comment">// can propagate upwards without being caught too early</span></span><br><span class="line">    <span class="comment">// 在获取内容长度之前获取流，以便 FileNotFoundException 可以向上传播而不会过早被捕获（todo: 不理解）</span></span><br><span class="line">    <span class="comment">// 获取缓存的 InputStream</span></span><br><span class="line">    <span class="type">InputStream</span> <span class="variable">in</span> <span class="operator">=</span> cachedInputStream();</span><br><span class="line"></span><br><span class="line">    <span class="comment">// This code has been uglified to protect against interrupts.</span></span><br><span class="line">    <span class="comment">// Even if a thread has been interrupted when loading resources,</span></span><br><span class="line">    <span class="comment">// the IO should not abort, so must carefully retry, failing only</span></span><br><span class="line">    <span class="comment">// if the retry leads to some other IO exception.</span></span><br><span class="line">    <span class="comment">// 该代码为了防止中断有点丑陋。即使线程在加载资源时被中断，IO 也不应该中止，因此必须小心重试，只有当重试导致其他 IO 异常时才会失败。</span></span><br><span class="line">    <span class="comment">// 检测当前线程是否收到中断信号，收到的话则返回 true 且清除中断状态，重新变更为未中断状态。</span></span><br><span class="line">    <span class="type">boolean</span> <span class="variable">isInterrupted</span> <span class="operator">=</span> Thread.interrupted();</span><br><span class="line">    <span class="type">int</span> len;</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">// 获取内容长度，顺利的话就跳出循环</span></span><br><span class="line">            len = getContentLength();</span><br><span class="line">            <span class="keyword">break</span>;</span><br><span class="line">        &#125; <span class="keyword">catch</span> (InterruptedIOException iioe) &#123;</span><br><span class="line">            <span class="comment">// 如果获取内容长度时，线程被中断抛出了异常，捕获后清除中断状态</span></span><br><span class="line">            Thread.interrupted();</span><br><span class="line">            isInterrupted = <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="keyword">try</span> &#123;</span><br><span class="line">        b = <span class="keyword">new</span> <span class="title class_">byte</span>[<span class="number">0</span>];</span><br><span class="line">        <span class="keyword">if</span> (len == -<span class="number">1</span>) len = Integer.MAX_VALUE;</span><br><span class="line">        <span class="type">int</span> <span class="variable">pos</span> <span class="operator">=</span> <span class="number">0</span>;</span><br><span class="line">        <span class="keyword">while</span> (pos &lt; len) &#123;</span><br><span class="line">            <span class="type">int</span> bytesToRead;</span><br><span class="line">            <span class="keyword">if</span> (pos &gt;= b.length) &#123; <span class="comment">// Only expand when there&#x27;s no room</span></span><br><span class="line">                <span class="comment">// 如果当前读取位置已经大于等于数组长度</span></span><br><span class="line">                <span class="comment">// 本次待读取字节长度 = 剩余未读取长度和 1024 取较小值</span></span><br><span class="line">                bytesToRead = Math.min(len - pos, b.length + <span class="number">1024</span>);</span><br><span class="line">                <span class="keyword">if</span> (b.length &lt; pos + bytesToRead) &#123;</span><br><span class="line">                    <span class="comment">// 如果当前读取位置 + 本次待读取字节长度 &gt; 数组长度，则创建新数组并复制数据</span></span><br><span class="line">                    b = Arrays.copyOf(b, pos + bytesToRead);</span><br><span class="line">                &#125;</span><br><span class="line">            &#125; <span class="keyword">else</span> &#123;</span><br><span class="line">                <span class="comment">// 数组还有空间，待读取字节长度 = 数组剩余空间</span></span><br><span class="line">                bytesToRead = b.length - pos;</span><br><span class="line">            &#125;</span><br><span class="line">            <span class="type">int</span> <span class="variable">cc</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">// 读取数据</span></span><br><span class="line">                cc = in.read(b, pos, bytesToRead);</span><br><span class="line">            &#125; <span class="keyword">catch</span> (InterruptedIOException iioe) &#123;</span><br><span class="line">                <span class="comment">// 如果读取时，线程被中断抛出了异常，捕获后清除中断状态</span></span><br><span class="line">                Thread.interrupted();</span><br><span class="line">                isInterrupted = <span class="literal">true</span>;</span><br><span class="line">            &#125;</span><br><span class="line">            <span class="keyword">if</span> (cc &lt; <span class="number">0</span>) &#123;</span><br><span class="line">                <span class="comment">// 如果读取返回值 &lt; 0</span></span><br><span class="line">                <span class="keyword">if</span> (len != Integer.MAX_VALUE) &#123;</span><br><span class="line">                    <span class="comment">// 且长度并未无限，表示提前检测到 EOF，抛出异常</span></span><br><span class="line">                    <span class="keyword">throw</span> <span class="keyword">new</span> <span class="title class_">EOFException</span>(<span class="string">&quot;Detect premature EOF&quot;</span>);</span><br><span class="line">                &#125; <span class="keyword">else</span> &#123;</span><br><span class="line">                    <span class="comment">// 如果长度无限，表示读到了文件结尾，数组长度大于当前读取位置，创建新数组并复制长度</span></span><br><span class="line">                    <span class="keyword">if</span> (b.length != pos) &#123;</span><br><span class="line">                        b = Arrays.copyOf(b, pos);</span><br><span class="line">                    &#125;</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">            pos += cc;</span><br><span class="line">        &#125;</span><br><span class="line">    &#125; <span class="keyword">finally</span> &#123;</span><br><span class="line">        <span class="keyword">try</span> &#123;</span><br><span class="line">            in.close();</span><br><span class="line">        &#125; <span class="keyword">catch</span> (InterruptedIOException iioe) &#123;</span><br><span class="line">            isInterrupted = <span class="literal">true</span>;</span><br><span class="line">        &#125; <span class="keyword">catch</span> (IOException ignore) &#123;&#125;</span><br><span class="line"></span><br><span class="line">        <span class="keyword">if</span> (isInterrupted) &#123;</span><br><span class="line">            <span class="comment">// 如果 isInterrupted 为 true，代表中断过，重新将线程状态置为中断。</span></span><br><span class="line">            Thread.currentThread().interrupt();</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="keyword">return</span> b;</span><br><span class="line">&#125;</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">
+<p>在 <code>getByteBuffer</code> 之后会缓存 <code>InputStream</code> 以便调用 <code>getBytes</code> 时使用，方法由 <code>synchronized</code> 修饰。</p>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">private</span> <span class="keyword">synchronized</span> InputStream <span class="title function_">cachedInputStream</span><span class="params">()</span> <span class="keyword">throws</span> IOException &#123;</span><br><span class="line">    <span class="keyword">if</span> (cis == <span class="literal">null</span>) &#123;</span><br><span class="line">        cis = getInputStream();</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="keyword">return</span> cis;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
 
-<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>在这个例子中，<code>Resource</code> 的实例是 <code>URLClassPath</code> 中的匿名类 <code>FileLoader</code> 以 <code>Resource</code> 的匿名类的方式创建的。</p>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> InputStream <span class="title function_">getInputStream</span><span class="params">()</span> <span class="keyword">throws</span> IOException</span><br><span class="line">&#123;</span><br><span class="line">    <span class="comment">// 在该匿名类中，getInputStream 的实现就是简单地根据 FileLoader 中保存的 File 实例创建 FileInputStream 并返回。</span></span><br><span class="line">    <span class="keyword">return</span> <span class="keyword">new</span> <span class="title class_">FileInputStream</span>(file);</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_">getContentLength</span><span class="params">()</span> <span class="keyword">throws</span> IOException</span><br><span class="line">&#123;</span><br><span class="line">    <span class="comment">// 在该匿名类中，getContentLength 的实现就是简单地根据 FileLoader 中保存的 File 实例获取长度。</span></span><br><span class="line">    <span class="keyword">return</span> (<span class="type">int</span>)file.length();</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>
+<h4 id="SecureClassLoader-defineClass"><a href="#SecureClassLoader-defineClass" class="headerlink" title="SecureClassLoader#defineClass"></a>SecureClassLoader#defineClass</h4><p><code>URLClassLoader</code> 继承自 <code>SecureClassLoader</code>，<code>SecureClassLoader</code> 提供并重载了 <code>defineClass</code> 方法，两个方法的注释均比代码长得多。<br>由注释可知，方法的作用是将字节数据（<code>byte[]</code> 类型或者 <code>ByteBuffer</code> 类型）转换为 <code>Class</code> 类型的实例，有一个可选的 <code>CodeSource</code> 类型的参数。</p>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">protected</span> <span class="keyword">final</span> Class&lt;?&gt; defineClass(String name,</span><br><span class="line">                                     <span class="type">byte</span>[] b, <span class="type">int</span> off, <span class="type">int</span> len,</span><br><span class="line">                                     CodeSource cs)</span><br><span class="line">&#123;</span><br><span class="line">    <span class="keyword">return</span> defineClass(name, b, off, len, getProtectionDomain(cs));</span><br><span class="line">&#125;</span><br><span class="line"></span><br><span class="line"><span class="keyword">protected</span> <span class="keyword">final</span> Class&lt;?&gt; defineClass(String name, java.nio.ByteBuffer b,</span><br><span class="line">                                     CodeSource cs)</span><br><span class="line">&#123;</span><br><span class="line">    <span class="keyword">return</span> defineClass(name, b, getProtectionDomain(cs));</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>
+<p>方法中只是简单地将 <code>CodeSource</code> 类型的参数转换成 <code>ProtectionDomain</code> 类型，就调用 <code>ClassLoader</code> 的 <code>defineClass</code> 方法。</p>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">private</span> ProtectionDomain <span class="title function_">getProtectionDomain</span><span class="params">(CodeSource cs)</span> &#123;</span><br><span class="line">    <span class="comment">// 如果 CodeSource 为 null，直接返回 null</span></span><br><span class="line">    <span class="keyword">if</span> (cs == <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><br><span class="line">    <span class="type">ProtectionDomain</span> <span class="variable">pd</span> <span class="operator">=</span> <span class="literal">null</span>;</span><br><span class="line">    <span class="keyword">synchronized</span> (pdcache) &#123;</span><br><span class="line">        <span class="comment">// 先从 Map 缓存中获取 ProtectionDomain</span></span><br><span class="line">        pd = pdcache.get(cs);</span><br><span class="line">        <span class="keyword">if</span> (pd == <span class="literal">null</span>) &#123;</span><br><span class="line">            <span class="comment">// 从 CodeSource 中获取 PermissionCollection</span></span><br><span class="line">            <span class="type">PermissionCollection</span> <span class="variable">perms</span> <span class="operator">=</span> getPermissions(cs);</span><br><span class="line">            <span class="comment">// 缓存中没有，则创建一个 ProtectionDomain 并放入缓存</span></span><br><span class="line">            pd = <span class="keyword">new</span> <span class="title class_">ProtectionDomain</span>(cs, perms, <span class="built_in">this</span>, <span class="literal">null</span>);</span><br><span class="line">            pdcache.put(cs, pd);</span><br><span class="line">            <span class="keyword">if</span> (debug != <span class="literal">null</span>) &#123;</span><br><span class="line">                debug.println(<span class="string">&quot; getPermissions &quot;</span>+ pd);</span><br><span class="line">                debug.println(<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><span class="line">    <span class="keyword">return</span> pd;</span><br><span class="line">&#125;</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>
-<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>《Redis 深度历险，核心原理与应用实践》</li>
+<h5 id="getPermissions"><a href="#getPermissions" class="headerlink" title="getPermissions"></a>getPermissions</h5><p>根据注释可知，此方法会返回给定 <code>CodeSource</code> 对象的权限。此方法由 <code>protect</code> 修饰，<code>AppClassLoader</code> 和 <code>URLClassLoader</code> 都有重写。当前 <code>ClassLoader</code> 是 <code>AppClassLoader</code>。</p>
+<p><code>AppClassLoader#getPermissions</code>，添加允许从类路径加载的任何类退出 VM的权限。</p>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">protected</span> PermissionCollection <span class="title function_">getPermissions</span><span class="params">(CodeSource codesource)</span></span><br><span class="line">&#123;</span><br><span class="line">    <span class="comment">// 调用父类 URLClassLoader 的 getPermissions</span></span><br><span class="line">    <span class="type">PermissionCollection</span> <span class="variable">perms</span> <span class="operator">=</span> <span class="built_in">super</span>.getPermissions(codesource);</span><br><span class="line">    <span class="comment">// 允许从类路径加载的任何类退出 VM的权限。</span></span><br><span class="line">    <span class="comment">// todo: 这是否自定义的类加载器加载的类，可能不能退出 VM。</span></span><br><span class="line">    perms.add(<span class="keyword">new</span> <span class="title class_">RuntimePermission</span>(<span class="string">&quot;exitVM&quot;</span>));</span><br><span class="line">    <span class="keyword">return</span> perms;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<p><code>SecureClassLoader#getPermissions</code>，添加一个读文件或读目录的权限。</p>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">protected</span> PermissionCollection <span class="title function_">getPermissions</span><span class="params">(CodeSource codesource)</span></span><br><span class="line">&#123;</span><br><span class="line">    <span class="comment">// 调用父类 SecureClassLoader 的 getPermissions</span></span><br><span class="line">    <span class="type">PermissionCollection</span> <span class="variable">perms</span> <span class="operator">=</span> <span class="built_in">super</span>.getPermissions(codesource);</span><br><span class="line"></span><br><span class="line">    <span class="type">URL</span> <span class="variable">url</span> <span class="operator">=</span> codesource.getLocation();</span><br><span class="line"></span><br><span class="line">    Permission p;</span><br><span class="line">    URLConnection urlConnection;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">try</span> &#123;</span><br><span class="line">        <span class="comment">// FileURLConnection 实例</span></span><br><span class="line">        urlConnection = url.openConnection();</span><br><span class="line">        <span class="comment">// 允许 read 的 FilePermission 实例</span></span><br><span class="line">        p = urlConnection.getPermission();</span><br><span class="line">    &#125; <span class="keyword">catch</span> (java.io.IOException ioe) &#123;</span><br><span class="line">        p = <span class="literal">null</span>;</span><br><span class="line">        urlConnection = <span class="literal">null</span>;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">if</span> (p <span class="keyword">instanceof</span> FilePermission) &#123;</span><br><span class="line">        <span class="comment">// if the permission has a separator char on the end,</span></span><br><span class="line">        <span class="comment">// it means the codebase is a directory, and we need</span></span><br><span class="line">        <span class="comment">// to add an additional permission to read recursively</span></span><br><span class="line">        <span class="comment">// 如果文件路径以文件分隔符结尾，表示目录，需要在末尾添加&quot;-&quot;改为递归读的权限</span></span><br><span class="line">        <span class="type">String</span> <span class="variable">path</span> <span class="operator">=</span> p.getName();</span><br><span class="line">        <span class="keyword">if</span> (path.endsWith(File.separator)) &#123;</span><br><span class="line">            path += <span class="string">&quot;-&quot;</span>;</span><br><span class="line">            p = <span class="keyword">new</span> <span class="title class_">FilePermission</span>(path, SecurityConstants.FILE_READ_ACTION);</span><br><span class="line">        &#125;</span><br><span class="line">    &#125; <span class="keyword">else</span> <span class="keyword">if</span> ((p == <span class="literal">null</span>) &amp;&amp; (url.getProtocol().equals(<span class="string">&quot;file&quot;</span>))) &#123;</span><br><span class="line">        <span class="type">String</span> <span class="variable">path</span> <span class="operator">=</span> url.getFile().replace(<span class="string">&#x27;/&#x27;</span>, File.separatorChar);</span><br><span class="line">        path = ParseUtil.decode(path);</span><br><span class="line">        <span class="keyword">if</span> (path.endsWith(File.separator))</span><br><span class="line">            path += <span class="string">&quot;-&quot;</span>;</span><br><span class="line">        p =  <span class="keyword">new</span> <span class="title class_">FilePermission</span>(path, SecurityConstants.FILE_READ_ACTION);</span><br><span class="line">    &#125; <span class="keyword">else</span> &#123;</span><br><span class="line">        <span class="comment">/**</span></span><br><span class="line"><span class="comment">         * Not loading from a &#x27;file:&#x27; URL so we want to give the class</span></span><br><span class="line"><span class="comment">         * permission to connect to and accept from the remote host</span></span><br><span class="line"><span class="comment">         * after we&#x27;ve made sure the host is the correct one and is valid.</span></span><br><span class="line"><span class="comment">         */</span></span><br><span class="line">        <span class="type">URL</span> <span class="variable">locUrl</span> <span class="operator">=</span> url;</span><br><span class="line">        <span class="keyword">if</span> (urlConnection <span class="keyword">instanceof</span> JarURLConnection) &#123;</span><br><span class="line">            locUrl = ((JarURLConnection)urlConnection).getJarFileURL();</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="type">String</span> <span class="variable">host</span> <span class="operator">=</span> locUrl.getHost();</span><br><span class="line">        <span class="keyword">if</span> (host != <span class="literal">null</span> &amp;&amp; (host.length() &gt; <span class="number">0</span>))</span><br><span class="line">            p = <span class="keyword">new</span> <span class="title class_">SocketPermission</span>(host,</span><br><span class="line">                                        SecurityConstants.SOCKET_CONNECT_ACCEPT_ACTION);</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// make sure the person that created this class loader</span></span><br><span class="line">    <span class="comment">// would have this permission</span></span><br><span class="line"></span><br><span class="line">    <span class="keyword">if</span> (p != <span class="literal">null</span>) &#123;</span><br><span class="line">        <span class="keyword">final</span> <span class="type">SecurityManager</span> <span class="variable">sm</span> <span class="operator">=</span> System.getSecurityManager();</span><br><span class="line">        <span class="keyword">if</span> (sm != <span class="literal">null</span>) &#123;</span><br><span class="line">            <span class="keyword">final</span> <span class="type">Permission</span> <span class="variable">fp</span> <span class="operator">=</span> p;</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> <span class="keyword">throws</span> SecurityException &#123;</span><br><span class="line">                    sm.checkPermission(fp);</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;, acc);</span><br><span class="line">        &#125;</span><br><span class="line">        perms.add(p);</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="keyword">return</span> perms;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<p><code>SecureClassLoader#getPermissions</code>，延迟设置权限，在创建 <code>ProtectionDomain</code> 时再设置。</p>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">protected</span> PermissionCollection <span class="title function_">getPermissions</span><span class="params">(CodeSource codesource)</span></span><br><span class="line">&#123;</span><br><span class="line">    <span class="comment">// 检查以确保类加载器已初始化。在 SecureClassLoader 构造器最后会用一个布尔变量表示加载器初始化成功。</span></span><br><span class="line">    <span class="comment">// 从代码上看，似乎只能保证 SecureClassLoader 的构造器方法已执行完毕？</span></span><br><span class="line">    check();</span><br><span class="line">    <span class="comment">// ProtectionDomain 延迟绑定，Permissions 继承 PermissionCollection 类。</span></span><br><span class="line">    <span class="keyword">return</span> <span class="keyword">new</span> <span class="title class_">Permissions</span>(); <span class="comment">// ProtectionDomain defers the binding</span></span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<h5 id="ProtectionDomain"><a href="#ProtectionDomain" class="headerlink" title="ProtectionDomain"></a>ProtectionDomain</h5><p><code>ProtectionDomain</code> 的相关构造器参数：</p>
+<ul>
+<li><code>CodeSource</code></li>
+<li><code>PermissionCollection</code>，如果不为 <code>null</code>，会设置权限为只读，表示权限在使用过程中不再修改；同时检查是否需要设置拥有全部权限。</li>
+<li><code>ClassLoader</code></li>
+<li><code>Principal[]</code></li>
 </ul>
-]]></content>
+<p>这样看来，<code>SecureClassLoader</code> 为了定义类做的处理，就是简单地创建一些关于权限的对象，并保存了 <code>CodeSource-&gt;ProtectionDomain</code> 的映射作为缓存。</p>
+<h4 id="ClassLoader-defineClass"><a href="#ClassLoader-defineClass" class="headerlink" title="ClassLoader#defineClass"></a>ClassLoader#defineClass</h4><p>抽象类 <code>ClassLoader</code> 中最终用于定义类的 <code>native</code> 方法 <code>define0</code>，<code>define1</code>，<code>define2</code> 都是由 <code>private</code> 修饰的，<code>ClassLoader</code> 提供并重载了 <code>defineClass</code> 方法作为使用它们的入口，这些 <code>defineClass</code> 方法都由 <code>protect</code> <code>final</code> 修饰，这意味着这些方法只能被子类使用，并且不能被重写。</p>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">protected</span> <span class="keyword">final</span> Class&lt;?&gt; defineClass(String name, <span class="type">byte</span>[] b, <span class="type">int</span> off, <span class="type">int</span> len)</span><br><span class="line">    <span class="keyword">throws</span> ClassFormatError</span><br><span class="line">&#123;</span><br><span class="line">    <span class="keyword">return</span> defineClass(name, b, off, len, <span class="literal">null</span>);</span><br><span class="line">&#125;</span><br><span class="line"></span><br><span class="line"><span class="keyword">protected</span> <span class="keyword">final</span> Class&lt;?&gt; defineClass(String name, <span class="type">byte</span>[] b, <span class="type">int</span> off, <span class="type">int</span> len,</span><br><span class="line">                                     ProtectionDomain protectionDomain)</span><br><span class="line">    <span class="keyword">throws</span> ClassFormatError</span><br><span class="line">&#123;</span><br><span class="line">    protectionDomain = preDefineClass(name, protectionDomain);</span><br><span class="line">    <span class="type">String</span> <span class="variable">source</span> <span class="operator">=</span> defineClassSourceLocation(protectionDomain);</span><br><span class="line">    Class&lt;?&gt; c = defineClass1(name, b, off, len, protectionDomain, source);</span><br><span class="line">    postDefineClass(c, protectionDomain);</span><br><span class="line">    <span class="keyword">return</span> c;</span><br><span class="line">&#125;</span><br><span class="line"></span><br><span class="line"><span class="keyword">protected</span> <span class="keyword">final</span> Class&lt;?&gt; defineClass(String name, java.nio.ByteBuffer b,</span><br><span class="line">                                     ProtectionDomain protectionDomain)</span><br><span class="line">    <span class="keyword">throws</span> ClassFormatError</span><br><span class="line">&#123;</span><br><span class="line">    <span class="type">int</span> <span class="variable">len</span> <span class="operator">=</span> b.remaining();</span><br><span class="line"></span><br><span class="line">    <span class="comment">// Use byte[] if not a direct ByteBufer:</span></span><br><span class="line">    <span class="keyword">if</span> (!b.isDirect()) &#123;</span><br><span class="line">        <span class="keyword">if</span> (b.hasArray()) &#123;</span><br><span class="line">            <span class="keyword">return</span> defineClass(name, b.array(),</span><br><span class="line">                                b.position() + b.arrayOffset(), len,</span><br><span class="line">                                protectionDomain);</span><br><span class="line">        &#125; <span class="keyword">else</span> &#123;</span><br><span class="line">            <span class="comment">// no array, or read-only array</span></span><br><span class="line">            <span class="type">byte</span>[] tb = <span class="keyword">new</span> <span class="title class_">byte</span>[len];</span><br><span class="line">            b.get(tb);  <span class="comment">// get bytes out of byte buffer.</span></span><br><span class="line">            <span class="keyword">return</span> defineClass(name, tb, <span class="number">0</span>, len, protectionDomain);</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    protectionDomain = preDefineClass(name, protectionDomain);</span><br><span class="line">    <span class="type">String</span> <span class="variable">source</span> <span class="operator">=</span> defineClassSourceLocation(protectionDomain);</span><br><span class="line">    Class&lt;?&gt; c = defineClass2(name, b, b.position(), len, protectionDomain, source);</span><br><span class="line">    postDefineClass(c, protectionDomain);</span><br><span class="line">    <span class="keyword">return</span> c;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<p>主要步骤：</p>
+<ol>
+<li><code>preDefineClass</code> 前置处理</li>
+<li><code>defineClassX</code></li>
+<li><code>postDefineClass</code> 后置处理</li>
+</ol>
+<h5 id="preDefineClass"><a href="#preDefineClass" class="headerlink" title="preDefineClass"></a>preDefineClass</h5><p>确定保护域 <code>ProtectionDomain</code>，并检查：</p>
+<ol>
+<li>未定义 <code>java.*</code> 类</li>
+<li>该类的签名者与包（<code>package</code>）中其余类的签名者相匹配</li>
+</ol>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">private</span> ProtectionDomain <span class="title function_">preDefineClass</span><span class="params">(String name,</span></span><br><span class="line"><span class="params">                                        ProtectionDomain pd)</span></span><br><span class="line">&#123;</span><br><span class="line">    <span class="comment">// 检查 name 为 null 或者有可能是有效的二进制名称</span></span><br><span class="line">    <span class="keyword">if</span> (!checkName(name))</span><br><span class="line">        <span class="keyword">throw</span> <span class="keyword">new</span> <span class="title class_">NoClassDefFoundError</span>(<span class="string">&quot;IllegalName: &quot;</span> + name);</span><br><span class="line"></span><br><span class="line">    <span class="comment">// Note:  Checking logic in java.lang.invoke.MemberName.checkForTypeAlias</span></span><br><span class="line">    <span class="comment">// relies on the fact that spoofing is impossible if a class has a name</span></span><br><span class="line">    <span class="comment">// of the form &quot;java.*&quot;</span></span><br><span class="line">    <span class="comment">// 如果 name 以 java. 开头，则抛出异常</span></span><br><span class="line">    <span class="keyword">if</span> ((name != <span class="literal">null</span>) &amp;&amp; name.startsWith(<span class="string">&quot;java.&quot;</span>)) &#123;</span><br><span class="line">        <span class="keyword">throw</span> <span class="keyword">new</span> <span class="title class_">SecurityException</span></span><br><span class="line">            (<span class="string">&quot;Prohibited package name: &quot;</span> +</span><br><span class="line">                name.substring(<span class="number">0</span>, name.lastIndexOf(<span class="string">&#x27;.&#x27;</span>)));</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="keyword">if</span> (pd == <span class="literal">null</span>) &#123;</span><br><span class="line">        <span class="comment">// 如果未传入 ProtectionDomain，取默认的 ProtectionDomain</span></span><br><span class="line">        pd = defaultDomain;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 存放了 package-&gt;certs 的 map 映射作为缓存，检查一个包内的 certs 都是一样的</span></span><br><span class="line">    <span class="comment">// todo: certs</span></span><br><span class="line">    <span class="keyword">if</span> (name != <span class="literal">null</span>) checkCerts(name, pd.getCodeSource());</span><br><span class="line"></span><br><span class="line">    <span class="keyword">return</span> pd;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<h5 id="defineClassSourceLocation"><a href="#defineClassSourceLocation" class="headerlink" title="defineClassSourceLocation"></a>defineClassSourceLocation</h5><p>确定 <code>Class</code> 的 <code>CodeSource</code> 位置。</p>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">private</span> String <span class="title function_">defineClassSourceLocation</span><span class="params">(ProtectionDomain pd)</span></span><br><span class="line">&#123;</span><br><span class="line">    <span class="type">CodeSource</span> <span class="variable">cs</span> <span class="operator">=</span> pd.getCodeSource();</span><br><span class="line">    <span class="type">String</span> <span class="variable">source</span> <span class="operator">=</span> <span class="literal">null</span>;</span><br><span class="line">    <span class="keyword">if</span> (cs != <span class="literal">null</span> &amp;&amp; cs.getLocation() != <span class="literal">null</span>) &#123;</span><br><span class="line">        source = cs.getLocation().toString();</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="keyword">return</span> source;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<h5 id="defineClassX-方法"><a href="#defineClassX-方法" class="headerlink" title="defineClassX 方法"></a>defineClassX 方法</h5><p>这些 <code>native</code> 方法使用了 <code>name</code>，字节数据，<code>ProtectionDomain</code> 和 <code>source</code> 等参数，像黑盒一样，在虚拟机中定义了一个类。</p>
+<h5 id="postDefineClass"><a href="#postDefineClass" class="headerlink" title="postDefineClass"></a>postDefineClass</h5><p>在定义类后使用 <code>ProtectionDomain</code> 中的 <code>certs</code> 补充 <code>Class</code> 实例的 <code>signer</code> 信息，猜测在 <code>native</code> 方法 <code>defineClassX</code> 方法中，对 <code>ProtectionDomain</code> 做了一些修改。事实上，从代码上看，将 <code>CodeSource</code> 包装为 <code>ProtectionDomain</code> 传入后，除了 <code>defineClassX</code> 方法外，其他地方都是取出 <code>CodeSource</code> 使用。</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_">postDefineClass</span><span class="params">(Class&lt;?&gt; c, ProtectionDomain pd)</span></span><br><span class="line">&#123;</span><br><span class="line">    <span class="keyword">if</span> (pd.getCodeSource() != <span class="literal">null</span>) &#123;</span><br><span class="line">        <span class="comment">// 获取证书</span></span><br><span class="line">        Certificate certs[] = pd.getCodeSource().getCertificates();</span><br><span class="line">        <span class="keyword">if</span> (certs != <span class="literal">null</span>)</span><br><span class="line">            setSigners(c, certs);</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>]]></content>
       <tags>
-        <tag>distributed lock</tag>
-        <tag>redis</tag>
+        <tag>java</tag>
+        <tag>class loader</tag>
       </tags>
   </entry>
   <entry>
@@ -1504,22 +1444,134 @@
 <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>
+<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>字符串常量池的测试和分析</title>
+    <url>/2023/11/03/testing-and-analysis-of-StringTable/</url>
+    <content><![CDATA[<p>如果你准备过 Java 的面试，应该看到过一个问题：“<code>String s1 = new String(&quot;abc&quot;);</code> 这个语句创建了几个字符串对象”。这个问题曾经困扰我，当时的我不能理解这个问题想要考察的是什么？<br>答案中或许提及了字符串常量池，但是如果细究起来，会发现答案并不完善，有些令人困惑，甚至问题本身就有一定的误导作用。它很容易让初学者以为创建一个字符串对象和创建一个其他类型的对象在过程上是有一些区别的。<br>其实关键的地方在于 “abc” 而不是 <code>new String(&quot;abc&quot;)</code>。</p>
+<h2 id="字符串常量池的作用"><a href="#字符串常量池的作用" class="headerlink" title="字符串常量池的作用"></a>字符串常量池的作用</h2><h3 id="字符串字面量"><a href="#字符串字面量" class="headerlink" title="字符串字面量"></a>字符串字面量</h3><p>字面量(literal)是用于表达源代码中的一个固定值的表示法(notion)，比如代码中的整数、浮点数、字符串。简而言之，字符串字面量就是双引号包裹的字符串，例如：</p>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="type">String</span> <span class="variable">s1</span> <span class="operator">=</span> <span class="string">&quot;a&quot;</span>;</span><br></pre></td></tr></table></figure>
+
+<p>在 Java 中，字符串对象就是一个 String 类型的对象，因此在程序运行时，String 类型的变量 s1 指向的一定是一个 String 对象。<strong>字面量 “a” 在某一个时刻，没有经过 new 关键字，变成了一个 String 对象</strong>。</p>
+<p>接下来我们来思考一个问题，程序中每一个字符串字面量都要对应着生成一个单独的 String 对象吗？考虑到 Java 中 String 对象是不可变的，显然相同的字符串字面量完全可以共用一个 String 对象从而避免重复创建对象。JVM 也是这样设计的，这些可以共用的 String 对象组成了一个字符串常量池。</p>
+<ol>
+<li>第一次遇到某一个字符串字面量时，会在字符串常量池中创建一个 String 对象，以后遇到相同的字符串字面量，就复用该对象，不再重复创建。</li>
+<li>每一次 new 都会创建一个新的 String 对象。</li>
+</ol>
+<p>ps: 以上的“遇到某一个字符串字面量”就是很纯粹地指代程序的源代码中出现用双引号括起来的字符串字面量。</p>
+<h3 id="进入字符串常量池的两种情况"><a href="#进入字符串常量池的两种情况" class="headerlink" title="进入字符串常量池的两种情况"></a>进入字符串常量池的两种情况</h3><p>因此，<strong>如果字符串常量池中没有值为 “abc” 的 String 对象</strong>，<code>new String(&quot;abc&quot;)</code> 语句将涉及两个 String 对象的创建，第一个是因为括号里的 “abc” 而在字符串常量池中生成的，第二个才是 new 关键字在堆中创建的；否则只会涉及一个 String 对象的创建。<br>为什么上面改用<strong>如果字符串常量池中没有值为 “abc” 的 String 对象</strong>呢？这是因为，字符串常量池里保留的 String 对象有两种产生来源：</p>
+<ol>
+<li>因为第一次遇到字符串字面量而生成的字符串对象。</li>
+<li>使用 <code>java.lang.String#intern</code> 主动地尝试将字符串对象放入字符串常量池。</li>
+</ol>
+<h2 id="常量池的分类"><a href="#常量池的分类" class="headerlink" title="常量池的分类"></a>常量池的分类</h2><ol>
+<li>Class 文件中的常量池(Constant Pool)</li>
+<li>运行时常量池(Runtime Constant Pool)</li>
+<li>字符串常量池</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_">StringTableTest_1</span> &#123;  </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">String</span> <span class="variable">s1</span> <span class="operator">=</span> <span class="string">&quot;a&quot;</span>;  </span><br><span class="line">        <span class="type">String</span> <span class="variable">s2</span> <span class="operator">=</span> <span class="string">&quot;b&quot;</span>;  </span><br><span class="line">        <span class="type">String</span> <span class="variable">s3</span> <span class="operator">=</span> <span class="string">&quot;ab&quot;</span>;  </span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+<p>使用 <code>javap -v .\StringTableTest_1.class</code> 进行反编译，摘取重要部分：</p>
+<figure class="highlight console"><table><tr><td class="code"><pre><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.#24         // 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 = String             <span class="comment">#25            // a</span></span></span><br><span class="line"><span class="meta prompt_">   #</span><span class="language-bash">3 = String             <span class="comment">#26            // b</span></span></span><br><span class="line"><span class="meta prompt_">   #</span><span class="language-bash">4 = String             <span class="comment">#27            // ab</span></span></span><br><span class="line"><span class="meta prompt_"></span></span><br><span class="line"><span class="meta prompt_">  #</span><span class="language-bash">25 = Utf8               a</span></span><br><span class="line"><span class="meta prompt_">  #</span><span class="language-bash">26 = Utf8               b</span></span><br><span class="line"><span class="meta prompt_">  #</span><span class="language-bash">27 = Utf8               ab</span></span><br><span class="line"></span><br><span class="line"></span><br><span class="line"></span><br><span class="line">0: ldc           #2                  // String a</span><br><span class="line">2: astore_1</span><br><span class="line">3: ldc           #3                  // String b</span><br><span class="line">5: astore_2</span><br><span class="line">6: ldc           #4                  // String ab</span><br><span class="line">8: astore_3</span><br><span class="line">9: return</span><br></pre></td></tr></table></figure>
+<ul>
+<li>Class 文件中的常量池 Constant pool 会记录代码中出现的字面量（文本文件）。</li>
+<li>运行时常量池是方法区的一部分，Class 文件中的常量池的内容，在类加载后，就进入了运行时常量池中（内存中的数据）。</li>
+<li>字符串常量池，记录 interned string 的一个全局表，JDK 6 前在方法区，后移到堆中。</li>
+</ul>
+<h2 id="字符串常量池的位置和形式"><a href="#字符串常量池的位置和形式" class="headerlink" title="字符串常量池的位置和形式"></a>字符串常量池的位置和形式</h2><p>在《深入理解Java虚拟机》提到：字符串常量池的位置从 JDK 7 开始，从永久代中移到了堆中。在这句话中，字符串常量池像是一个特定的内存区域，存储了 interned string 的实例。</p>
+<img src="/2023/11/03/testing-and-analysis-of-StringTable/Pasted%20image%2020231103113047.png" class="" title="字符串常量池的位置">
+
+<h3 id="验证字符串常量池的位置"><a href="#验证字符串常量池的位置" class="headerlink" title="验证字符串常量池的位置"></a>验证字符串常量池的位置</h3><p>书中使用了以下方式来验证字符串常量池的位置。</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_">StringTableTest_8</span> &#123;  </span><br><span class="line">  </span><br><span class="line">    <span class="comment">// JDK 1.8 设置 -Xmx10m -XX:-UseGCOverheadLimit    </span></span><br><span class="line">    <span class="comment">// JDK 1.6 设置 -XX:MaxPerSize=10m</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">        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">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">for</span> (<span class="type">int</span> <span class="variable">j</span> <span class="operator">=</span> <span class="number">0</span>; j &lt; <span class="number">260000</span>; j++) &#123;  </span><br><span class="line">                list.add(String.valueOf(j).intern());  </span><br><span class="line">                i++;  </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">            e.printStackTrace();  </span><br><span class="line">        &#125; <span class="keyword">finally</span> &#123;  </span><br><span class="line">            System.out.println(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>
+<p>在 JDK 8 中异常如下：</p>
+<figure class="highlight console"><table><tr><td class="code"><pre><span class="line">Exception in thread &quot;main&quot; java.lang.OutOfMemoryError: Java heap space</span><br></pre></td></tr></table></figure>
+<p>在 JDK 6 中异常如下：</p>
+<figure class="highlight console"><table><tr><td class="code"><pre><span class="line">java.lang.OutOfMemoryError: PermGen space</span><br></pre></td></tr></table></figure>
+
+<p>同时书中也提到了，在字符串常量池的位置改变后，它只用保存第一次出现时字符串对象的引用。JDK 8 中的 intern 方法可以印证该说法，方法注释中提到：如果字符串常量池中已存在相等(equals)的字符串，那就返回已存在的对象（这样原先准备加入的对象就可以释放）；否则，将字符串对象加入字符串常量池中，直接返回对该对象的引用（不用像 JDK 6 时，复制一个对象加入常量池，返回该复制对象的引用）。</p>
+<h3 id="关于-intern-的实验"><a href="#关于-intern-的实验" class="headerlink" title="关于 intern 的实验"></a>关于 intern 的实验</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_">StringTableTest_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> &#123;  </span><br><span class="line">        <span class="comment">// &quot;a&quot;、&quot;b&quot; 作为字符串字面量，会解析得到字符串对象放入字符串常量池      </span></span><br><span class="line">        <span class="comment">// 但是 new String(&quot;a&quot;) 创建出来的字符串对象，不会进入字符串常量池        </span></span><br><span class="line">        <span class="type">String</span> <span class="variable">s1</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">String</span>(<span class="string">&quot;a&quot;</span>) + <span class="keyword">new</span> <span class="title class_">String</span>(<span class="string">&quot;b&quot;</span>);  </span><br><span class="line">        <span class="comment">// intern 方法尝试将 s1 放入 StringTable，无则放入，返回该对象引用，有则返回已存在对象的引用  </span></span><br><span class="line">        <span class="type">String</span> <span class="variable">s2</span> <span class="operator">=</span> s1.intern();  </span><br><span class="line">  </span><br><span class="line">        <span class="type">String</span> <span class="variable">x</span> <span class="operator">=</span> <span class="string">&quot;ab&quot;</span>;  </span><br><span class="line">  </span><br><span class="line">		System.out.println(s2 == x);  </span><br><span class="line">		System.out.println(s1 == x); </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_">StringTableTest_6</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="comment">// 将 &quot;ab&quot; 的赋值语句提前到最开始，&quot;ab&quot; 生成的字符串对象进入字符串常量池       </span></span><br><span class="line">        <span class="type">String</span> <span class="variable">x</span> <span class="operator">=</span> <span class="string">&quot;ab&quot;</span>;  </span><br><span class="line">        <span class="type">String</span> <span class="variable">s1</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">String</span>(<span class="string">&quot;a&quot;</span>) + <span class="keyword">new</span> <span class="title class_">String</span>(<span class="string">&quot;b&quot;</span>);  </span><br><span class="line">        <span class="comment">// intern 方法尝试将 s1 放入 StringTable，无则放入，返回该对象引用，有则返回已存在对象的引用  </span></span><br><span class="line">        <span class="type">String</span> <span class="variable">s2</span> <span class="operator">=</span> s1.intern();  </span><br><span class="line">  </span><br><span class="line">        System.out.println(s2 == x);  </span><br><span class="line">        System.out.println(s1 == x);  </span><br><span class="line">    &#125;  </span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+<p>实验结果证实了上述说法。</p>
+<h3 id="字符串常量池到底是什么？"><a href="#字符串常量池到底是什么？" class="headerlink" title="字符串常量池到底是什么？"></a>字符串常量池到底是什么？</h3><p>但是 <a href="https://www.zhihu.com/people/logirl.cc">xinxi</a> 提及：字符串常量池，也称为 StringTable，本质上是一个惰性维护的哈希表，是一个纯运行时的结构，只存储对 <code>java.lang.String</code> 实例的引用，而不存储 String 对象的内容。当我们提到一个字符串进入字符串常量池其实是说在这个 StringTable 中保存了对它的引用，反之，如果说没有在其中就是说 StringTable 中没有对它的引用。<br><a href="https://blog.csdn.net/zyplanke">zyplanke</a> 分析 StringTable 在内存中的形式时，也表达了类似的观点。</p>
+<img src="/2023/11/03/testing-and-analysis-of-StringTable/Pasted%20image%2020231103194544.png" class="" title="StringTable 的内存形式">
+
+<p>尽管这个疑问似乎不妨碍我们理解很多东西，但是深究之后，真的让人困惑，网上也没有搜集到更多的信息。字符串常量池和 StringTable 是否等价？字符串常量池更准确的说法是否是“一个保存引用的 StringTable 加上分布在堆（JDK 6 以前的永久代）中的字符串实例”？<br>已经好几次打开 jvm 的源码，却看不懂它到底什么意思啊！！！！！难道是时候开始学 C++ 了吗。</p>
+<h2 id="进入字符串常量池的时机"><a href="#进入字符串常量池的时机" class="headerlink" title="进入字符串常量池的时机"></a>进入字符串常量池的时机</h2><p>前面提到了第一次遇到的字符串字面量会在某一个时刻，生成对应的字符串对象进入字符串常量池，同时也提到了，字符串常量池（StringTable）的维护是懒惰的，那么这些究竟是什么时候发生的呢？</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_">StringTableTest_12</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> IOException &#123;</span><br><span class="line">        <span class="keyword">new</span> <span class="title class_">String</span>(<span class="string">&quot;ab&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"> 0: new           #2                  // class java/lang/String</span><br><span class="line"> 3: dup</span><br><span class="line"> 4: ldc           #3                  // String ab</span><br><span class="line"> 6: invokespecial #4                  // Method java/lang/String.&quot;&lt;init&gt;&quot;:(Ljava/lang/String;)V</span><br><span class="line"> 9: pop</span><br><span class="line">10: return</span><br></pre></td></tr></table></figure>
+
+<p><a href="https://www.zhihu.com/people/rednaxelafx">RednaxelaFX</a> 的文章提到：</p>
+<blockquote>
+<p>在类加载阶段，JVM 会在堆中创建对应这些 class 文件常量池中的字符串对象实例，并在字符串常量池中驻留其引用。具体在 resolve 阶段执行。这些常量全局共享。</p>
+</blockquote>
+<p><a href="https://www.zhihu.com/people/logirl.cc">xinxi</a> 的文章中补充到：</p>
+<blockquote>
+<p>这里说的比较笼统，没错，是 resolve 阶段，但是并不是大家想的那样，立即就创建对象并且在字符串常量池中驻留了引用。 <strong>JVM规范里明确指定resolve阶段可以是lazy的。</strong><br>……<br>就 HotSpot VM 的实现来说，加载类的时候，那些字符串字面量会进入到当前类的运行时常量池，不会进入全局的字符串常量池（即在 StringTable 中并没有相应的引用，在堆中也没有对应的对象产生）。</p>
+</blockquote>
+<p>《深入理解Java虚拟机》中提到：</p>
+<blockquote>
+<p>《Java虚拟机规范》之中并未规定解析阶段发生的具体时间，只要求了在执行ane-warray、checkcast、getfield、getstatic、instanceof、invokedynamic、invokeinterface、invoke-special、invokestatic、invokevirtual、ldc、ldc_w、ldc2_w、multianewarray、new、putfield和putstatic这17个用于操作符号引用的字节码指令之前，先对它们所使用的符号引用进行解析。所以虚拟机实现可以根据需要来自行判断，到底是在类被加载器加载时就对常量池中的符号引用进行解析，还是等到一个符号引用将要被使用前才去解析它。</p>
+</blockquote>
+<p>综上可知，字符串字面量的解析是属于类加载的解析阶段，但是《Java虚拟机规范》并未规定解析发生的具体时间，只要求在执行一些字节码指令前进行，其中包括了 ldc 指令。虚拟机的具体实现，比如 Hotspot 就在执行 <code>ldc #indexNumber</code> 前触发解析，根据字符串常量池中是否已存在字符串对象决定是否创建对象，并将对象推送到栈顶。<br>这也证实了前文中提到的字符串字面量生成字符串对象和 new 关键字无关。</p>
+<h3 id="验证延迟实例化"><a href="#验证延迟实例化" class="headerlink" title="验证延迟实例化"></a>验证延迟实例化</h3><p>使用 IDEA memory 功能，观察字符串对象的个数逐个变化。</p>
+<ol>
+<li>直到第一次运行到字符串字面量时，才会创建对应的字符串对象。</li>
+<li>相同的字符串常量，不会重复创建字符串对象。</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_">StringTableTest_4</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><br><span class="line">         </span><br><span class="line">        System.out.println(<span class="string">&quot;1&quot;</span>);  </span><br><span class="line">        System.out.println(<span class="string">&quot;2&quot;</span>);  </span><br><span class="line">        System.out.println(<span class="string">&quot;3&quot;</span>);  </span><br><span class="line">        System.out.println(<span class="string">&quot;4&quot;</span>);  </span><br><span class="line">        System.out.println(<span class="string">&quot;5&quot;</span>);  </span><br><span class="line">        System.out.println(<span class="string">&quot;6&quot;</span>);  </span><br><span class="line">        System.out.println(<span class="string">&quot;7&quot;</span>);  </span><br><span class="line">        System.out.println(<span class="string">&quot;8&quot;</span>);  </span><br><span class="line">        System.out.println(<span class="string">&quot;9&quot;</span>);  </span><br><span class="line">        System.out.println(<span class="string">&quot;0&quot;</span>);  </span><br><span class="line">        System.out.println(<span class="string">&quot;1&quot;</span>);  </span><br><span class="line">        System.out.println(<span class="string">&quot;2&quot;</span>);  </span><br><span class="line">        System.out.println(<span class="string">&quot;3&quot;</span>);  </span><br><span class="line">        System.out.println(<span class="string">&quot;4&quot;</span>);  </span><br><span class="line">        System.out.println(<span class="string">&quot;5&quot;</span>);  </span><br><span class="line">        System.out.println(<span class="string">&quot;6&quot;</span>);  </span><br><span class="line">        System.out.println(<span class="string">&quot;7&quot;</span>);  </span><br><span class="line">        System.out.println(<span class="string">&quot;8&quot;</span>);  </span><br><span class="line">        System.out.println(<span class="string">&quot;9&quot;</span>);  </span><br><span class="line">        System.out.println(<span class="string">&quot;0&quot;</span>);  </span><br><span class="line">    &#125;  </span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<img src="/2023/11/03/testing-and-analysis-of-StringTable/Pasted%20image%2020231102225445.png" class="" title="字符串字面量延迟实例化">
+
+<h2 id="字符串常量池的垃圾回收和性能优化"><a href="#字符串常量池的垃圾回收和性能优化" class="headerlink" title="字符串常量池的垃圾回收和性能优化"></a>字符串常量池的垃圾回收和性能优化</h2><h3 id="垃圾回收"><a href="#垃圾回收" class="headerlink" title="垃圾回收"></a>垃圾回收</h3><p>前文提到字符串常量池在 JDK 7 开始移到堆中，是因为考虑在方法区中的垃圾回收是比较困难的，同时随着字节码技术的发展，CGLib 等会大量动态生成类的技术的运用使得方法区的内存紧张，将字符串常量池移到堆中，可以有效提高其垃圾回收效率。</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_">StringTableTest_9</span> &#123;  </span><br><span class="line">  </span><br><span class="line">    <span class="comment">// -Xmx10m -XX:+PrintStringTableStatistics -XX:+PrintGCDetails -verbose:gc  </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">            <span class="comment">// 0-&gt;100-&gt;10000，观察统计信息中数量的变化以及垃圾回收记录</span></span><br><span class="line">            <span class="keyword">for</span> (<span class="type">int</span> <span class="variable">j</span> <span class="operator">=</span> <span class="number">0</span>; j &lt; <span class="number">10000</span>; j++) &#123;  </span><br><span class="line">                String.valueOf(j).intern();  </span><br><span class="line">                i++;  </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">            e.printStackTrace();  </span><br><span class="line">        &#125; <span class="keyword">finally</span> &#123;  </span><br><span class="line">            System.out.println(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="code"><pre><span class="line">[GC (Allocation Failure) [PSYoungGen: 2048K-&gt;488K(2560K)] 2048K-&gt;856K(9728K), 0.0007745 secs] [Times: user=0.00 sys=0.00, real=0.00 secs] </span><br><span class="line"></span><br><span class="line"></span><br><span class="line">StringTable statistics:</span><br><span class="line">Number of buckets       :     60013 =    480104 bytes, avg   8.000</span><br><span class="line">Number of entries       :      7277 =    174648 bytes, avg  24.000</span><br><span class="line">Number of literals      :      7277 =    421560 bytes, avg  57.930</span><br><span class="line">Total footprint         :           =   1076312 bytes</span><br><span class="line">Average bucket size     :     0.121</span><br><span class="line">Variance of bucket size :     0.125</span><br><span class="line">Std. dev. of bucket size:     0.354</span><br><span class="line">Maximum bucket size     :         3</span><br></pre></td></tr></table></figure>
+
+<h3 id="性能优化"><a href="#性能优化" class="headerlink" title="性能优化"></a>性能优化</h3><h4 id="调整-buckets-size"><a href="#调整-buckets-size" class="headerlink" title="调整 buckets size"></a>调整 buckets size</h4><p>当 size 过小，哈希碰撞增加，链表变长，效率会变低，需要增大 buckets size。</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_">StringTableTest_10</span> &#123;  </span><br><span class="line">  </span><br><span class="line">    <span class="comment">// -XX:StringTableSize=200000 -XX:+PrintStringTableStatistics  </span></span><br><span class="line">    <span class="comment">// 默认-&gt;200000-&gt;1009(最小值)，观察耗时  </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> (<span class="type">BufferedReader</span> <span class="variable">br</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>(<span class="keyword">new</span> <span class="title class_">FileInputStream</span>(<span class="string">&quot;src/main/resources/linux.words&quot;</span>), StandardCharsets.UTF_8))) &#123;  </span><br><span class="line">            <span class="type">String</span> <span class="variable">line</span> <span class="operator">=</span> <span class="literal">null</span>;  </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">while</span> (<span class="literal">true</span>) &#123;  </span><br><span class="line">                line = br.readLine();  </span><br><span class="line">                <span class="keyword">if</span> (line == <span class="literal">null</span>) &#123;  </span><br><span class="line">                    <span class="keyword">break</span>;  </span><br><span class="line">                &#125;  </span><br><span class="line">                line.intern();  </span><br><span class="line">            &#125;  </span><br><span class="line">            System.out.println(<span class="string">&quot;cost: &quot;</span> + (System.nanoTime() - start) / <span class="number">1000000</span>) ;  </span><br><span class="line">        &#125; <span class="keyword">catch</span> (IOException 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="主动运用-intern-的场景"><a href="#主动运用-intern-的场景" class="headerlink" title="主动运用 intern 的场景"></a>主动运用 intern 的场景</h4><p>当你需要大量缓存重复的字符串时，使用 intern 可以大大减少内存占用。</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_">StringTableTest_11</span> &#123;  </span><br><span class="line">  </span><br><span class="line">    <span class="comment">// -Xms500m -Xmx500m -XX:StringTableSize=200000 -XX:+PrintStringTableStatistics  </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;String&gt; words = <span class="keyword">new</span> <span class="title class_">ArrayList</span>&lt;&gt;();  </span><br><span class="line">        System.in.read();  </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">10</span>; i++) &#123;  </span><br><span class="line">            <span class="keyword">try</span> (<span class="type">BufferedReader</span> <span class="variable">br</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>(<span class="keyword">new</span> <span class="title class_">FileInputStream</span>(<span class="string">&quot;src/main/resources/linux.words&quot;</span>), StandardCharsets.UTF_8))) &#123;  </span><br><span class="line">                <span class="type">String</span> <span class="variable">line</span> <span class="operator">=</span> <span class="literal">null</span>;  </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">while</span> (<span class="literal">true</span>) &#123;  </span><br><span class="line">                    line = br.readLine();  </span><br><span class="line">                    <span class="keyword">if</span> (line == <span class="literal">null</span>) &#123;  </span><br><span class="line">                        <span class="keyword">break</span>;  </span><br><span class="line">                    &#125;    </span><br><span class="line">                    <span class="comment">// words.add(line);  </span></span><br><span class="line">                    words.add(line.intern());  </span><br><span class="line">                &#125;  </span><br><span class="line">                System.out.println(<span class="string">&quot;cost: &quot;</span> + (System.nanoTime() - start) / <span class="number">1000000</span>) ;  </span><br><span class="line">            &#125;  </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">&#125;</span><br></pre></td></tr></table></figure>
+
+<p>使用 VisualVM 观察字符串和 char[] 内存占用情况，可以发现提升显著。</p>
+<img src="/2023/11/03/testing-and-analysis-of-StringTable/Pasted%20image%2020231103131707.png" class="" title="intern 减少内存占用">
 
-<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>
+<h2 id="字符串拼接"><a href="#字符串拼接" class="headerlink" title="字符串拼接"></a>字符串拼接</h2><h3 id="变量的拼接"><a href="#变量的拼接" class="headerlink" title="变量的拼接"></a>变量的拼接</h3><p>字符串变量的拼接，底层是使用 StringBuilder 实现：<code>new StringBuilder().append(&quot;a&quot;).append(&quot;b&quot;).toString()</code>，而 toString 方法使用拼接得到的 char 数组创建一个新的 String 对象，因此 s3 和 s4 是不相同的两个对象。</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_">StringTableTest_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">        <span class="type">String</span> <span class="variable">s1</span> <span class="operator">=</span> <span class="string">&quot;a&quot;</span>;  </span><br><span class="line">        <span class="type">String</span> <span class="variable">s2</span> <span class="operator">=</span> <span class="string">&quot;b&quot;</span>;  </span><br><span class="line">        <span class="type">String</span> <span class="variable">s3</span> <span class="operator">=</span> <span class="string">&quot;ab&quot;</span>;  </span><br><span class="line">        <span class="type">String</span> <span class="variable">s4</span> <span class="operator">=</span> s1 + s2;  </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>
+<figure class="highlight console"><table><tr><td class="code"><pre><span class="line"> 0: ldc           #2                  // String a</span><br><span class="line"> 2: astore_1</span><br><span class="line"> 3: ldc           #3                  // String b</span><br><span class="line"> 5: astore_2</span><br><span class="line"> 6: ldc           #4                  // String ab</span><br><span class="line"> 8: astore_3</span><br><span class="line"> 9: new           #5                  // class java/lang/StringBuilder</span><br><span class="line">12: dup</span><br><span class="line">13: invokespecial #6                  // Method java/lang/StringBuilder.&quot;&lt;init&gt;&quot;:()V</span><br><span class="line">16: aload_1</span><br><span class="line">17: invokevirtual #7                  // Method java/lang/StringBuilder.append:(Ljava/lang/String;)Ljava/lang/StringBuilder;</span><br><span class="line">20: aload_2</span><br><span class="line">21: invokevirtual #7                  // Method java/lang/StringBuilder.append:(Ljava/lang/String;)Ljava/lang/StringBuilder;</span><br><span class="line">24: invokevirtual #8                  // Method java/lang/StringBuilder.toString:()Ljava/lang/String;</span><br><span class="line">27: astore        4</span><br><span class="line">29: return</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>
+<h3 id="常量的拼接"><a href="#常量的拼接" class="headerlink" title="常量的拼接"></a>常量的拼接</h3><p>字符串常量的拼接是在编译期间，因为已知结果而被优化为一个字符串常量。又因为 “ab” 字符串在 StringTable 中是已存在的，所以不会重新创建新对象。</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_">StringTableTest_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">        <span class="type">String</span> <span class="variable">s1</span> <span class="operator">=</span> <span class="string">&quot;a&quot;</span>;</span><br><span class="line">        <span class="type">String</span> <span class="variable">s2</span> <span class="operator">=</span> <span class="string">&quot;b&quot;</span>;</span><br><span class="line">        <span class="type">String</span> <span class="variable">s3</span> <span class="operator">=</span> <span class="string">&quot;ab&quot;</span>;</span><br><span class="line">        <span class="type">String</span> <span class="variable">s4</span> <span class="operator">=</span> s1 + s2;</span><br><span class="line">        <span class="type">String</span> <span class="variable">s5</span> <span class="operator">=</span> <span class="string">&quot;a&quot;</span> + <span class="string">&quot;b&quot;</span>;</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>
+<figure class="highlight console"><table><tr><td class="code"><pre><span class="line"> 0: ldc           #2                  // String a</span><br><span class="line"> 2: astore_1</span><br><span class="line"> 3: ldc           #3                  // String b</span><br><span class="line"> 5: astore_2</span><br><span class="line"> 6: ldc           #4                  // String ab</span><br><span class="line"> 8: astore_3</span><br><span class="line"> 9: new           #5                  // class java/lang/StringBuilder</span><br><span class="line">12: dup</span><br><span class="line">13: invokespecial #6                  // Method java/lang/StringBuilder.&quot;&lt;init&gt;&quot;:()V</span><br><span class="line">16: aload_1</span><br><span class="line">17: invokevirtual #7                  // Method java/lang/StringBuilder.append:(Ljava/lang/String;)Ljava/lang/StringBuilder;</span><br><span class="line">20: aload_2</span><br><span class="line">21: invokevirtual #7                  // Method java/lang/StringBuilder.append:(Ljava/lang/String;)Ljava/lang/StringBuilder;</span><br><span class="line">24: invokevirtual #8                  // Method java/lang/StringBuilder.toString:()Ljava/lang/String;</span><br><span class="line">27: astore        4</span><br><span class="line">29: ldc           #4                  // String ab</span><br><span class="line">31: astore        5</span><br><span class="line">33: return</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>
+<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><ol>
+<li><a href="https://www.zhihu.com/question/55994121/answer/147296098">Java 中new String(“字面量”) 中 “字面量” 是何时进入字符串常量池的? - xinxi的回答 - 知乎</a></li>
+<li><a href="https://www.iteye.com/topic/774673">请别再拿“String s &#x3D; new String(“xyz”);创建了多少个String实例”来面试了吧</a></li>
+<li><a href="https://blog.csdn.net/zyplanke/article/details/108699727">JVM中字符串常量池StringTable在内存中形式分析</a></li>
+</ol>
 ]]></content>
       <tags>
         <tag>java</tag>
@@ -1527,85 +1579,83 @@
       </tags>
   </entry>
   <entry>
-    <title>使用 Grafana 和 Prometheus 搭建监控</title>
-    <url>/2023/11/18/setup-monitoring-using-grafana-and-prometheus/</url>
-    <content><![CDATA[<h3 id="Grafana"><a href="#Grafana" class="headerlink" title="Grafana"></a>Grafana</h3><h4 id="docker-compose-部署"><a href="#docker-compose-部署" class="headerlink" title="docker-compose 部署"></a>docker-compose 部署</h4><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">grafana:</span></span><br><span class="line">    <span class="attr">image:</span> <span class="string">grafana/grafana:9.5.6</span></span><br><span class="line">    <span class="attr">container_name:</span> <span class="string">grafana</span></span><br><span class="line">    <span class="attr">ports:</span></span><br><span class="line">      <span class="bullet">-</span> <span class="number">3000</span><span class="string">:3000</span></span><br><span class="line">    <span class="attr">volumes:</span></span><br><span class="line">      <span class="bullet">-</span> <span class="string">grafana-storage:/var/lib/grafana</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">volumes:</span></span><br><span class="line">  <span class="attr">grafana-storage:</span></span><br><span class="line">    <span class="attr">driver:</span> <span class="string">local</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>
+    <title>关于 Java 字节码指令的一些例子分析</title>
+    <url>/2023/11/09/some-examples-of-Java-bytecode-instruction-analysis/</url>
+    <content><![CDATA[<h2 id="演示字节码指令的执行"><a href="#演示字节码指令的执行" class="headerlink" title="演示字节码指令的执行"></a>演示字节码指令的执行</h2><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_">ByteCodeTest_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">        <span class="type">int</span> <span class="variable">a</span> <span class="operator">=</span> <span class="number">10</span>;</span><br><span class="line">        <span class="type">int</span> <span class="variable">b</span> <span class="operator">=</span> Short.MAX_VALUE + <span class="number">1</span>;</span><br><span class="line">        <span class="type">int</span> <span class="variable">c</span> <span class="operator">=</span> a + b;</span><br><span class="line">        System.out.println(c);</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
 
-<h3 id="Prometheus"><a href="#Prometheus" class="headerlink" title="Prometheus"></a>Prometheus</h3><h4 id="docker-compose-部署-1"><a href="#docker-compose-部署-1" class="headerlink" title="docker-compose 部署"></a>docker-compose 部署</h4><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">prometheus:</span></span><br><span class="line">    <span class="attr">image:</span> <span class="string">bitnami/prometheus:2.45.0</span></span><br><span class="line">    <span class="attr">container_name:</span> <span class="string">prometheus</span></span><br><span class="line">    <span class="attr">ports:</span></span><br><span class="line">      <span class="bullet">-</span> <span class="number">19090</span><span class="string">:9090</span></span><br><span class="line">    <span class="attr">volumes:</span> </span><br><span class="line">      <span class="bullet">-</span> <span class="string">prometheus-data:/opt/bitnami/prometheus/data</span></span><br><span class="line">      <span class="bullet">-</span> <span class="string">$PWD/conf/prometheus.yml:/opt/bitnami/prometheus/conf/prometheus.yml</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">volumes:</span></span><br><span class="line">  <span class="attr">prometheus-data:</span></span><br><span class="line">    <span class="attr">driver:</span> <span class="string">local</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="操作数栈和本地变量表的大小"><a href="#操作数栈和本地变量表的大小" class="headerlink" title="操作数栈和本地变量表的大小"></a>操作数栈和本地变量表的大小</h3><p>在编译期间就可计算得到操作数栈和本地变量表的大小。</p>
+<figure class="highlight console"><table><tr><td class="code"><pre><span class="line">stack=2, locals=4, args_size=1</span><br></pre></td></tr></table></figure>
 
-<h4 id="配置文件-prometheus-yml"><a href="#配置文件-prometheus-yml" class="headerlink" title="配置文件 prometheus.yml"></a>配置文件 prometheus.yml</h4><figure class="highlight yaml"><table><tr><td class="code"><pre><span class="line"><span class="attr">global:</span></span><br><span class="line">  <span class="attr">scrape_interval:</span> <span class="string">15s</span></span><br><span class="line"></span><br><span class="line"><span class="attr">scrape_configs:</span></span><br><span class="line"><span class="comment"># Ubuntu</span></span><br><span class="line"><span class="bullet">-</span> <span class="attr">job_name:</span> <span class="string">node</span></span><br><span class="line">  <span class="attr">static_configs:</span></span><br><span class="line">  <span class="bullet">-</span> <span class="attr">targets:</span> [<span class="string">&#x27;192.168.46.135:9100&#x27;</span>]</span><br><span class="line"><span class="comment"># Windows</span></span><br><span class="line"><span class="bullet">-</span> <span class="attr">job_name:</span> <span class="string">windows</span></span><br><span class="line">  <span class="attr">static_configs:</span></span><br><span class="line">  <span class="bullet">-</span> <span class="attr">targets:</span> [<span class="string">&#x27;192.168.46.1:9182&#x27;</span>]</span><br><span class="line"><span class="comment"># Redis</span></span><br><span class="line"><span class="bullet">-</span> <span class="attr">job_name:</span> <span class="string">redis-exporter</span></span><br><span class="line">  <span class="attr">static_configs:</span></span><br><span class="line">  <span class="bullet">-</span> <span class="attr">targets:</span> [<span class="string">&#x27;redis-exporter:9121&#x27;</span>]</span><br><span class="line"><span class="comment"># MySQL</span></span><br><span class="line"><span class="bullet">-</span> <span class="attr">job_name:</span> <span class="string">mysqld-exporter</span></span><br><span class="line">  <span class="attr">static_configs:</span></span><br><span class="line">  <span class="bullet">-</span> <span class="attr">targets:</span> [<span class="string">&#x27;mysqld-exporter:9104&#x27;</span>]</span><br></pre></td></tr></table></figure>
+<h3 id="本地变量表"><a href="#本地变量表" class="headerlink" title="本地变量表"></a>本地变量表</h3><p>Slot，即槽位，可理解为索引。</p>
+<figure class="highlight console"><table><tr><td class="code"><pre><span class="line">Start  Length  Slot  Name   Signature</span><br><span class="line">    0      18     0  args   [Ljava/lang/String;</span><br><span class="line">    3      15     1     a   I</span><br><span class="line">    6      12     2     b   I</span><br><span class="line">   10       8     3     c   I</span><br></pre></td></tr></table></figure>
 
-<h3 id="Ubuntu-监控"><a href="#Ubuntu-监控" class="headerlink" title="Ubuntu 监控"></a>Ubuntu 监控</h3><h4 id="node-exporter"><a href="#node-exporter" class="headerlink" title="node_exporter"></a>node_exporter</h4><p>node_exporter 被设计为监控主机系统，因为它需要访问主机系统，所以不推荐使用 Docker 容器部署。</p>
-<ul>
-<li><a href="https://github.com/prometheus/node_exporter">node_exporter Github 仓库</a></li>
-<li><a href="https://prometheus.io/download/#node_exporter">node_exporter 下载地址</a></li>
-<li><a href="https://prometheus.io/docs/guides/node-exporter/">node_exporter 使用指南</a></li>
-</ul>
-<h4 id="步骤"><a href="#步骤" class="headerlink" title="步骤"></a>步骤</h4><ol>
-<li>下载解压得到 node_exporter 二进制可执行文件。</li>
-<li>修改权限，<code>chmod u+x node_exporter</code></li>
-<li><code>./node_exporter</code> 启动</li>
-<li>Prometheus 配置文件<figure class="highlight yaml"><table><tr><td class="code"><pre><span class="line"><span class="attr">global:</span></span><br><span class="line">  <span class="attr">scrape_interval:</span> <span class="string">15s</span></span><br><span class="line"></span><br><span class="line"><span class="attr">scrape_configs:</span></span><br><span class="line"><span class="bullet">-</span> <span class="attr">job_name:</span> <span class="string">node</span></span><br><span class="line">  <span class="attr">static_configs:</span></span><br><span class="line">  <span class="bullet">-</span> <span class="attr">targets:</span> [<span class="string">&#x27;localhost:9100&#x27;</span>]</span><br></pre></td></tr></table></figure></li>
-</ol>
-<h4 id="设置-node-exporter-自启动"><a href="#设置-node-exporter-自启动" class="headerlink" title="设置 node_exporter 自启动"></a>设置 node_exporter 自启动</h4><ol>
-<li>路径 <code>/etc/systemd/system</code></li>
-<li>创建 <code>node_exporter.service</code><figure class="highlight shell"><table><tr><td class="code"><pre><span class="line">[Unit]</span><br><span class="line">Description=node_exporter</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">Restart=on-failure</span><br><span class="line">ExecStart=/opt/node_exporter</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>
-</ol>
-<img src="/2023/11/18/setup-monitoring-using-grafana-and-prometheus/Snipaste_2023-11-19_01-11-22.png" class="" title="Ubuntu 监控">
+<h3 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</h3><figure class="highlight console"><table><tr><td class="code"><pre><span class="line"><span class="meta prompt_">#</span><span class="language-bash">3 = Integer            32768</span></span><br><span class="line"><span class="meta prompt_">#</span><span class="language-bash">4 = Fieldref           <span class="comment">#27.#28        // java/lang/System.out:Ljava/io/PrintStream;</span></span></span><br><span class="line"><span class="meta prompt_">#</span><span class="language-bash">5 = Methodref          <span class="comment">#29.#30        // java/io/PrintStream.println:(I)V</span></span> </span><br></pre></td></tr></table></figure>
 
-<h3 id="Windows-监控"><a href="#Windows-监控" class="headerlink" title="Windows 监控"></a>Windows 监控</h3><h4 id="windows-exporter"><a href="#windows-exporter" class="headerlink" title="windows_exporter"></a>windows_exporter</h4><ul>
-<li><a href="https://github.com/prometheus-community/windows_exporter">windows_exporter Github 仓库</a></li>
-<li><a href="https://github.com/prometheus-community/windows_exporter/releases">windows_exporter 下载地址</a></li>
-<li><a href="https://prometheus.io/docs/guides/node-exporter/">windows_exporter 使用指南</a></li>
-</ul>
-<h4 id="步骤-1"><a href="#步骤-1" class="headerlink" title="步骤"></a>步骤</h4><ol>
-<li>下载得到 windows_exporter-0.24.0-amd64.msi 安装程序。</li>
-<li>以默认方式安装</li>
-<li>Prometheus 配置文件<figure class="highlight yaml"><table><tr><td class="code"><pre><span class="line"><span class="attr">global:</span></span><br><span class="line">  <span class="attr">scrape_interval:</span> <span class="string">15s</span></span><br><span class="line"></span><br><span class="line"><span class="attr">scrape_configs:</span></span><br><span class="line"><span class="bullet">-</span> <span class="attr">job_name:</span> <span class="string">windows</span></span><br><span class="line"><span class="comment"># Windows</span></span><br><span class="line">  <span class="attr">static_configs:</span></span><br><span class="line">  <span class="bullet">-</span> <span class="attr">targets:</span> [<span class="string">&#x27;192.168.46.1:9182&#x27;</span>]</span><br></pre></td></tr></table></figure></li>
-</ol>
-<img src="/2023/11/18/setup-monitoring-using-grafana-and-prometheus/Snipaste_2023-11-19_01-16-05.png" class="" title="Windows 监控">
+<img src="/2023/11/09/some-examples-of-Java-bytecode-instruction-analysis/Snipaste_2023-11-10_00-28-14.png" class="" title="字节码指令执行栈帧示意图">
 
-<h3 id="Redis-监控"><a href="#Redis-监控" class="headerlink" title="Redis 监控"></a>Redis 监控</h3><h4 id="redis-exporter"><a href="#redis-exporter" class="headerlink" title="redis_exporter"></a>redis_exporter</h4><ul>
-<li><a href="https://github.com/oliver006/redis_exporter">redis_exporter Github 仓库</a></li>
-<li><a href="https://hub.docker.com/r/oliver006/redis_exporter/">redis_exporter Docker 官方镜像</a></li>
-<li><a href="https://hub.docker.com/r/oliver006/redis_exporter/">redis_exporter Docker bitnami 镜像</a></li>
+<h3 id="字节码指令"><a href="#字节码指令" class="headerlink" title="字节码指令"></a>字节码指令</h3><figure class="highlight console"><table><tr><td class="code"><pre><span class="line"> 0: bipush        10</span><br><span class="line"> 2: istore_1</span><br><span class="line"> 3: ldc           #3             // int 32768</span><br><span class="line"> 5: istore_2</span><br><span class="line"> 6: iload_1</span><br><span class="line"> 7: iload_2</span><br><span class="line"> 8: iadd</span><br><span class="line"> 9: istore_3</span><br><span class="line">10: getstatic     #4             // Field java/lang/System.out:Ljava/io/PrintStream;</span><br><span class="line">13: iload_3</span><br><span class="line">14: invokevirtual #5             // Method java/io/PrintStream.println:(I)V</span><br><span class="line">17: return</span><br></pre></td></tr></table></figure>
+<ul>
+<li>bipush，将一个 byte，推入操作数栈。<ul>
+<li>short 范围内的数是和字节码指令一起存储的，范围外的数是存储在运行时常量池中的。</li>
+<li>操作数栈的宽度是 4 个字节，short 范围内的数在推入操作数栈前会经过符号扩展成为 int。</li>
 </ul>
-<h4 id="docker-compose-部署-2"><a href="#docker-compose-部署-2" class="headerlink" title="docker-compose 部署"></a>docker-compose 部署</h4><p>使用 bitnami 提供的镜像代替官方镜像并没有特殊考量。使用环境变量 REDIS_ADDR 指定目标 Redis。</p>
-<figure class="highlight yaml"><table><tr><td class="code"><pre><span class="line"><span class="attr">version:</span> <span class="string">&#x27;2&#x27;</span></span><br><span class="line"><span class="attr">services:</span></span><br><span class="line">  <span class="attr">redis:</span></span><br><span class="line">    <span class="attr">image:</span> <span class="string">&#x27;redis:4.0&#x27;</span></span><br><span class="line">    <span class="attr">container_name:</span> <span class="string">redis</span></span><br><span class="line">    <span class="attr">ports:</span></span><br><span class="line">      <span class="bullet">-</span> <span class="number">6379</span><span class="string">:6379</span></span><br><span class="line">    <span class="attr">volumes:</span></span><br><span class="line">      <span class="bullet">-</span> <span class="string">redis-data:/data</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 class="attr">redis-exporter:</span></span><br><span class="line">    <span class="attr">image:</span> <span class="string">bitnami/redis-exporter:1.55.0</span></span><br><span class="line">    <span class="attr">container_name:</span> <span class="string">redis-exporter</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 class="attr">environment:</span></span><br><span class="line">      <span class="bullet">-</span> <span class="string">REDIS_ADDR=redis://redis:6379</span></span><br><span class="line">    <span class="attr">depends_on:</span></span><br><span class="line">      <span class="bullet">-</span> <span class="string">redis</span></span><br><span class="line"></span><br><span class="line"><span class="attr">volumes:</span></span><br><span class="line">  <span class="attr">redis-data:</span></span><br><span class="line">    <span class="attr">driver:</span> <span class="string">local</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>
-
-<img src="/2023/11/18/setup-monitoring-using-grafana-and-prometheus/Snipaste_2023-11-19_01-16-54.png" class="" title="Redis 监控">
-
-<h3 id="MySQL-监控"><a href="#MySQL-监控" class="headerlink" title="MySQL 监控"></a>MySQL 监控</h3><h4 id="mysqld-exporter"><a href="#mysqld-exporter" class="headerlink" title="mysqld_exporter"></a>mysqld_exporter</h4><ul>
-<li><a href="https://github.com/prometheus/mysqld_exporter">mysqld_exporter Github 仓库</a></li>
-<li><a href="https://registry.hub.docker.com/r/prom/mysqld-exporter/">mysqld_exporter Docker 官方镜像</a></li>
+</li>
+<li>istore_1，将栈顶的 int，存入局部变量表，槽位 1。</li>
+<li>ldc，从运行时常量池中将指定常量推入操作数栈。</li>
+<li>istore_2，将栈顶的 int，存入局部变量表，槽位 2。</li>
+<li>iload_1 iload_2，依次从局部变量表将两个 int 推入操作数栈，槽位分别是 1 和 2。</li>
+<li>iadd，将栈顶的两个 int 弹出并相加，将结果推入操作数栈。</li>
+<li>istore_3，将栈顶的 int，存入局部变量表，槽位 3。</li>
+<li>getstatic，获取类的静态属性，推入操作数栈。</li>
+<li>iload_3，从局部变量表将 int 推入操作数栈，槽位 3。</li>
+<li>invokevirtual，将栈顶的参数依次弹出，调用实例方法。</li>
+<li>return，返回 void</li>
 </ul>
-<h4 id="docker-compose-部署-3"><a href="#docker-compose-部署-3" class="headerlink" title="docker-compose 部署"></a>docker-compose 部署</h4><ol>
-<li>使用 volume 将配置文件 .my.cnf 挂载到容器中</li>
-<li>使用 command 指定启动时的参数</li>
-</ol>
-<blockquote>
-<p><strong>坑！！！</strong>在文档中找配置文件的默认挂载路径或者如何配置启动时的配置文件，找了好久都没找到。搭配上后来的坑，直接迷失数小时。</p>
-</blockquote>
-<figure class="highlight yaml"><table><tr><td class="code"><pre><span class="line"><span class="attr">version:</span> <span class="string">&#x27;1.0&#x27;</span></span><br><span class="line"><span class="attr">services:</span></span><br><span class="line">  <span class="attr">mysql_57:</span></span><br><span class="line">    <span class="attr">image:</span> <span class="string">mysql:5.7</span></span><br><span class="line">    <span class="attr">container_name:</span> <span class="string">mysql_57</span></span><br><span class="line">    <span class="attr">ports:</span></span><br><span class="line">      <span class="bullet">-</span> <span class="number">13306</span><span class="string">:3306</span></span><br><span class="line">    <span class="attr">environment:</span></span><br><span class="line">      <span class="bullet">-</span> <span class="string">MYSQL_ROOT_PASSWORD=123456</span></span><br><span class="line">      <span class="bullet">-</span> <span class="string">TZ=Asia/Shanghai</span></span><br><span class="line">    <span class="attr">volumes:</span></span><br><span class="line">      <span class="bullet">-</span> <span class="string">/opt/mysql_5.7/data:/var/lib/mysql</span></span><br><span class="line">      <span class="bullet">-</span> <span class="string">/opt/mysql_5.7/conf/my.cnf:/etc/my.cnf</span></span><br><span class="line">      <span class="bullet">-</span> <span class="string">./sql:/docker-entrypoint-initdb.d</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 class="attr">mysqld-exporter:</span></span><br><span class="line">    <span class="attr">image:</span> <span class="string">prom/mysqld-exporter:v0.15.0</span></span><br><span class="line">    <span class="attr">container_name:</span> <span class="string">mysqld-exporter</span></span><br><span class="line">    <span class="attr">ports:</span></span><br><span class="line">      <span class="bullet">-</span> <span class="number">19104</span><span class="string">:9104</span></span><br><span class="line">    <span class="attr">volumes:</span></span><br><span class="line">      <span class="bullet">-</span> <span class="string">./exporter/.my.cnf:/cfg/.my.cnf</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 class="attr">command:</span> </span><br><span class="line">      <span class="bullet">-</span> <span class="string">--config.my-cnf=/cfg/.my.cnf</span></span><br><span class="line">    <span class="attr">depends_on:</span></span><br><span class="line">      <span class="bullet">-</span> <span class="string">mysql_57</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>
-
-<h4 id="mysqld-exporter-配置文件"><a href="#mysqld-exporter-配置文件" class="headerlink" title="mysqld_exporter 配置文件"></a>mysqld_exporter 配置文件</h4><p>创建一个专用的 MySQL 用户。</p>
-<figure class="highlight plaintext"><table><tr><td class="code"><pre><span class="line">CREATE USER &#x27;exporter&#x27;@&#x27;localhost&#x27; IDENTIFIED BY &#x27;XXXXXXXX&#x27; WITH MAX_USER_CONNECTIONS 3;</span><br><span class="line">GRANT PROCESS, REPLICATION CLIENT, SELECT ON *.* TO &#x27;exporter&#x27;@&#x27;localhost&#x27;;</span><br></pre></td></tr></table></figure>
+<h2 id="分析-a-和-a"><a href="#分析-a-和-a" class="headerlink" title="分析 a++ 和 ++a"></a>分析 a++ 和 ++a</h2><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_">ByteCodeTest_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">        <span class="type">int</span> <span class="variable">a</span> <span class="operator">=</span> <span class="number">10</span>;</span><br><span class="line">        <span class="type">int</span> <span class="variable">b</span> <span class="operator">=</span> a++ + ++a + a--;</span><br><span class="line">        System.out.println(a);</span><br><span class="line">        System.out.println(b);</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
 
-<figure class="highlight shell"><table><tr><td class="code"><pre><span class="line">[client]</span><br><span class="line">host=mysql_57</span><br><span class="line">port=3306</span><br><span class="line">user=exporter</span><br><span class="line">password=123456</span><br></pre></td></tr></table></figure>
+<h3 id="字节码指令-1"><a href="#字节码指令-1" class="headerlink" title="字节码指令"></a>字节码指令</h3><figure class="highlight console"><table><tr><td class="code"><pre><span class="line"> 0: bipush        10</span><br><span class="line"> 2: istore_1</span><br><span class="line"> 3: iload_1</span><br><span class="line"> 4: iinc          1, 1</span><br><span class="line"> 7: iinc          1, 1</span><br><span class="line">10: iload_1</span><br><span class="line">11: iadd</span><br><span class="line">12: iload_1</span><br><span class="line">13: iinc          1, -1</span><br><span class="line">16: iadd</span><br><span class="line">17: istore_2</span><br></pre></td></tr></table></figure>
 
-<p><strong>坑！！！</strong>根据 <a href="https://github.com/prometheus/mysqld_exporter/releases/tag/v0.15.0">0.15.0 CHANGE LOG</a>，不再支持使用环境变量 DATA_SOURCE_NAME 设置 MySQL 的信息。Docker 镜像的文档未及时更新。需使用 <code>.my.cnf</code> 或命令行参数进行配置。<br>Docker 镜像文档更新不及时。</p>
-<figure class="highlight console"><table><tr><td class="code"><pre><span class="line">Error parsing host config&quot; file=.my.cnf err=&quot;no configuration found</span><br></pre></td></tr></table></figure>
+<ul>
+<li>a++ 和 ++a 的区别是先 load 还是先 iinc。</li>
+<li>iinc，将局部变量表指定槽位的数加上一个常数。</li>
+<li>注意 a 只 load 到操作数栈并没有 store 回局部变量表。</li>
+<li>b &#x3D; 10 + 12 + 12 &#x3D; 34</li>
+<li>a &#x3D; 10 + 1 + 1 - 1 &#x3D; 11</li>
+</ul>
+<h2 id="分析判断条件"><a href="#分析判断条件" class="headerlink" title="分析判断条件"></a>分析判断条件</h2><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_">ByteCodeTest_4</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="type">int</span> <span class="variable">a</span> <span class="operator">=</span> <span class="number">0</span>;</span><br><span class="line">        <span class="comment">// ifeq, goto</span></span><br><span class="line">        <span class="keyword">if</span> (a == <span class="number">0</span>) &#123;</span><br><span class="line">            a = <span class="number">10</span>;</span><br><span class="line">        &#125; <span class="keyword">else</span> &#123;</span><br><span class="line">            a = <span class="number">20</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><strong>坑！！！</strong>带字符的复杂密码不能被正确解析。MySQL 使用了随机生成的复杂密码，怎么都连接不上。</p>
-<figure class="highlight console"><table><tr><td class="code"><pre><span class="line">caller=exporter.go:152 level=error msg=&quot;Error pinging mysqld&quot; err=&quot;Error 1045 (28000): Access denied for user &#x27;exporter&#x27;@&#x27;172.19.0.13&#x27; (using password: YES)&quot;</span><br></pre></td></tr></table></figure>
+<h3 id="字节码指令-2"><a href="#字节码指令-2" class="headerlink" title="字节码指令"></a>字节码指令</h3><figure class="highlight console"><table><tr><td class="code"><pre><span class="line"> 0: iconst_0</span><br><span class="line"> 1: istore_1</span><br><span class="line"> 2: iload_1</span><br><span class="line"> 3: ifne          12</span><br><span class="line"> 6: bipush        10</span><br><span class="line"> 8: istore_1</span><br><span class="line"> 9: goto          15</span><br><span class="line">12: bipush        20</span><br><span class="line">14: istore_1</span><br><span class="line">15: return</span><br></pre></td></tr></table></figure>
 
-<blockquote>
-<p>数坑并发，搜遍全网，折腾半夜，痛不欲生。</p>
-</blockquote>
-<img src="/2023/11/18/setup-monitoring-using-grafana-and-prometheus/Snipaste_2023-11-19_01-17-25.png" class="" title="MySQL 监控">]]></content>
+<ul>
+<li>iconst，将一个 int 常量推入操作数栈。</li>
+<li>if<code>&lt;cond&gt;</code>，一个 int 和 0 的比较成立时进入分支，跳转到指定行号。</li>
+<li>goto，总是进入的分支，跳转到指定行号。</li>
+</ul>
+<h2 id="涉及的字节码指令"><a href="#涉及的字节码指令" class="headerlink" title="涉及的字节码指令"></a>涉及的字节码指令</h2><ul>
+<li>bipush，将一个 byte 符号扩展为一个 int，推入操作数栈。</li>
+<li>istore，将栈顶的 int，存入局部变量表的指定槽位。</li>
+<li>iload，将局部变量表指定槽位的 int，推入操作数栈。</li>
+<li>ldc，从运行时常量池将指定常量推入操作数栈。</li>
+<li>iadd，将栈顶的两个 int 弹出并相加，将结果推入操作数栈。</li>
+<li>getstatic，获取类的静态属性，推入操作数栈。</li>
+<li>invokevirtual，将栈顶的参数依次弹出，调用实例方法。</li>
+<li>return，返回 void。</li>
+<li>iinc，将局部变量表中指定槽位的数加一个常量。</li>
+<li>if<code>&lt;cond&gt;</code>，一个 int 和 0 的比较成立时进入分支，跳转到指定行号。<ul>
+<li>ifeq，equals</li>
+<li>ifne，not equals</li>
+<li>iflt，less than</li>
+<li>ifge，greater than or equals</li>
+<li>ifgt，great than</li>
+<li>ifle，less than or equals</li>
+</ul>
+</li>
+<li>goto，总是进入的分支，跳转到指定行号。</li>
+</ul>
+]]></content>
       <tags>
-        <tag>grafana</tag>
-        <tag>prometheus</tag>
+        <tag>java</tag>
+        <tag>bytecode</tag>
       </tags>
   </entry>
   <entry>
@@ -1954,144 +2004,151 @@
       </tags>
   </entry>
   <entry>
-    <title>Spring AOP 如何创建代理 beans</title>
-    <url>/2023/11/19/how-does-Spring-AOP-create-proxy-beans/</url>
-    <content><![CDATA[<p>Spring AOP 是基于代理实现的，它既支持 JDK 动态代理也支持 CGLib。</p>
+    <title>使用 Grafana 和 Prometheus 搭建监控</title>
+    <url>/2023/11/18/setup-monitoring-using-grafana-and-prometheus/</url>
+    <content><![CDATA[<h3 id="Grafana"><a href="#Grafana" class="headerlink" title="Grafana"></a>Grafana</h3><h4 id="docker-compose-部署"><a href="#docker-compose-部署" class="headerlink" title="docker-compose 部署"></a>docker-compose 部署</h4><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">grafana:</span></span><br><span class="line">    <span class="attr">image:</span> <span class="string">grafana/grafana:9.5.6</span></span><br><span class="line">    <span class="attr">container_name:</span> <span class="string">grafana</span></span><br><span class="line">    <span class="attr">ports:</span></span><br><span class="line">      <span class="bullet">-</span> <span class="number">3000</span><span class="string">:3000</span></span><br><span class="line">    <span class="attr">volumes:</span></span><br><span class="line">      <span class="bullet">-</span> <span class="string">grafana-storage:/var/lib/grafana</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">volumes:</span></span><br><span class="line">  <span class="attr">grafana-storage:</span></span><br><span class="line">    <span class="attr">driver:</span> <span class="string">local</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="Prometheus"><a href="#Prometheus" class="headerlink" title="Prometheus"></a>Prometheus</h3><h4 id="docker-compose-部署-1"><a href="#docker-compose-部署-1" class="headerlink" title="docker-compose 部署"></a>docker-compose 部署</h4><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">prometheus:</span></span><br><span class="line">    <span class="attr">image:</span> <span class="string">bitnami/prometheus:2.45.0</span></span><br><span class="line">    <span class="attr">container_name:</span> <span class="string">prometheus</span></span><br><span class="line">    <span class="attr">ports:</span></span><br><span class="line">      <span class="bullet">-</span> <span class="number">19090</span><span class="string">:9090</span></span><br><span class="line">    <span class="attr">volumes:</span> </span><br><span class="line">      <span class="bullet">-</span> <span class="string">prometheus-data:/opt/bitnami/prometheus/data</span></span><br><span class="line">      <span class="bullet">-</span> <span class="string">$PWD/conf/prometheus.yml:/opt/bitnami/prometheus/conf/prometheus.yml</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">volumes:</span></span><br><span class="line">  <span class="attr">prometheus-data:</span></span><br><span class="line">    <span class="attr">driver:</span> <span class="string">local</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>
+
+<h4 id="配置文件-prometheus-yml"><a href="#配置文件-prometheus-yml" class="headerlink" title="配置文件 prometheus.yml"></a>配置文件 prometheus.yml</h4><figure class="highlight yaml"><table><tr><td class="code"><pre><span class="line"><span class="attr">global:</span></span><br><span class="line">  <span class="attr">scrape_interval:</span> <span class="string">15s</span></span><br><span class="line"></span><br><span class="line"><span class="attr">scrape_configs:</span></span><br><span class="line"><span class="comment"># Ubuntu</span></span><br><span class="line"><span class="bullet">-</span> <span class="attr">job_name:</span> <span class="string">node</span></span><br><span class="line">  <span class="attr">static_configs:</span></span><br><span class="line">  <span class="bullet">-</span> <span class="attr">targets:</span> [<span class="string">&#x27;192.168.46.135:9100&#x27;</span>]</span><br><span class="line"><span class="comment"># Windows</span></span><br><span class="line"><span class="bullet">-</span> <span class="attr">job_name:</span> <span class="string">windows</span></span><br><span class="line">  <span class="attr">static_configs:</span></span><br><span class="line">  <span class="bullet">-</span> <span class="attr">targets:</span> [<span class="string">&#x27;192.168.46.1:9182&#x27;</span>]</span><br><span class="line"><span class="comment"># Redis</span></span><br><span class="line"><span class="bullet">-</span> <span class="attr">job_name:</span> <span class="string">redis-exporter</span></span><br><span class="line">  <span class="attr">static_configs:</span></span><br><span class="line">  <span class="bullet">-</span> <span class="attr">targets:</span> [<span class="string">&#x27;redis-exporter:9121&#x27;</span>]</span><br><span class="line"><span class="comment"># MySQL</span></span><br><span class="line"><span class="bullet">-</span> <span class="attr">job_name:</span> <span class="string">mysqld-exporter</span></span><br><span class="line">  <span class="attr">static_configs:</span></span><br><span class="line">  <span class="bullet">-</span> <span class="attr">targets:</span> [<span class="string">&#x27;mysqld-exporter:9104&#x27;</span>]</span><br></pre></td></tr></table></figure>
+
+<h3 id="Ubuntu-监控"><a href="#Ubuntu-监控" class="headerlink" title="Ubuntu 监控"></a>Ubuntu 监控</h3><h4 id="node-exporter"><a href="#node-exporter" class="headerlink" title="node_exporter"></a>node_exporter</h4><p>node_exporter 被设计为监控主机系统，因为它需要访问主机系统，所以不推荐使用 Docker 容器部署。</p>
 <ul>
-<li>在什么时候创建代理对象的？</li>
-<li>怎么创建代理对象的？</li>
+<li><a href="https://github.com/prometheus/node_exporter">node_exporter Github 仓库</a></li>
+<li><a href="https://prometheus.io/download/#node_exporter">node_exporter 下载地址</a></li>
+<li><a href="https://prometheus.io/docs/guides/node-exporter/">node_exporter 使用指南</a></li>
 </ul>
-<h2 id="过程简单图解"><a href="#过程简单图解" class="headerlink" title="过程简单图解"></a>过程简单图解</h2><img src="/2023/11/19/how-does-Spring-AOP-create-proxy-beans/Pasted%20image%2020231120223506.png" class="" title="Spring AOP 创建代理的过程">
+<h4 id="步骤"><a href="#步骤" class="headerlink" title="步骤"></a>步骤</h4><ol>
+<li>下载解压得到 node_exporter 二进制可执行文件。</li>
+<li>修改权限，<code>chmod u+x node_exporter</code></li>
+<li><code>./node_exporter</code> 启动</li>
+<li>Prometheus 配置文件<figure class="highlight yaml"><table><tr><td class="code"><pre><span class="line"><span class="attr">global:</span></span><br><span class="line">  <span class="attr">scrape_interval:</span> <span class="string">15s</span></span><br><span class="line"></span><br><span class="line"><span class="attr">scrape_configs:</span></span><br><span class="line"><span class="bullet">-</span> <span class="attr">job_name:</span> <span class="string">node</span></span><br><span class="line">  <span class="attr">static_configs:</span></span><br><span class="line">  <span class="bullet">-</span> <span class="attr">targets:</span> [<span class="string">&#x27;localhost:9100&#x27;</span>]</span><br></pre></td></tr></table></figure></li>
+</ol>
+<h4 id="设置-node-exporter-自启动"><a href="#设置-node-exporter-自启动" class="headerlink" title="设置 node_exporter 自启动"></a>设置 node_exporter 自启动</h4><ol>
+<li>路径 <code>/etc/systemd/system</code></li>
+<li>创建 <code>node_exporter.service</code><figure class="highlight shell"><table><tr><td class="code"><pre><span class="line">[Unit]</span><br><span class="line">Description=node_exporter</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">Restart=on-failure</span><br><span class="line">ExecStart=/opt/node_exporter</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>
+</ol>
+<img src="/2023/11/18/setup-monitoring-using-grafana-and-prometheus/Snipaste_2023-11-19_01-11-22.png" class="" title="Ubuntu 监控">
 
-<h2 id="准备工作"><a href="#准备工作" class="headerlink" title="准备工作"></a>准备工作</h2><ul>
-<li>引入依赖<figure class="highlight xml"><table><tr><td class="code"><pre><span class="line"><span class="tag">&lt;<span class="name">dependency</span>&gt;</span></span><br><span class="line">    <span class="tag">&lt;<span class="name">groupId</span>&gt;</span>org.springframework<span class="tag">&lt;/<span class="name">groupId</span>&gt;</span></span><br><span class="line">    <span class="tag">&lt;<span class="name">artifactId</span>&gt;</span>spring-context<span class="tag">&lt;/<span class="name">artifactId</span>&gt;</span></span><br><span class="line">    <span class="tag">&lt;<span class="name">version</span>&gt;</span>4.3.12.RELEASE<span class="tag">&lt;/<span class="name">version</span>&gt;</span></span><br><span class="line"><span class="tag">&lt;/<span class="name">dependency</span>&gt;</span></span><br><span class="line"><span class="tag">&lt;<span class="name">dependency</span>&gt;</span></span><br><span class="line">    <span class="tag">&lt;<span class="name">groupId</span>&gt;</span>org.springframework<span class="tag">&lt;/<span class="name">groupId</span>&gt;</span></span><br><span class="line">    <span class="tag">&lt;<span class="name">artifactId</span>&gt;</span>spring-aspects<span class="tag">&lt;/<span class="name">artifactId</span>&gt;</span></span><br><span class="line">    <span class="tag">&lt;<span class="name">version</span>&gt;</span>4.3.12.RELEASE<span class="tag">&lt;/<span class="name">version</span>&gt;</span></span><br><span class="line"><span class="tag">&lt;/<span class="name">dependency</span>&gt;</span></span><br></pre></td></tr></table></figure></li>
-<li>目标对象类<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_">MathCalculator</span> &#123;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">public</span> <span class="type">int</span> <span class="title function_">div</span><span class="params">(<span class="type">int</span> i, <span class="type">int</span> j)</span> &#123;</span><br><span class="line">        <span class="keyword">return</span> i / j;</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure></li>
-<li>切面类<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="meta">@Aspect</span></span><br><span class="line"><span class="keyword">public</span> <span class="keyword">class</span> <span class="title class_">LogAspects</span> &#123;</span><br><span class="line"></span><br><span class="line">    <span class="meta">@Pointcut(&quot;execution(public int com.moralok.aop.MathCalculator.*(..))&quot;)</span></span><br><span class="line">    <span class="keyword">public</span> <span class="keyword">void</span> <span class="title function_">pointCut</span><span class="params">()</span> &#123;</span><br><span class="line"></span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="meta">@Before(&quot;pointCut()&quot;)</span></span><br><span class="line">    <span class="keyword">public</span> <span class="keyword">void</span> <span class="title function_">logStart</span><span class="params">(JoinPoint joinPoint)</span> &#123;</span><br><span class="line">        System.out.println(joinPoint.getSignature().getName() + <span class="string">&quot;除法运行@Before。。。参数列表为 &quot;</span> + Arrays.asList(joinPoint.getArgs()) + <span class="string">&quot;&quot;</span>);</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="meta">@After(&quot;pointCut()&quot;)</span></span><br><span class="line">    <span class="keyword">public</span> <span class="keyword">void</span> <span class="title function_">logEnd</span><span class="params">(JoinPoint joinPoint)</span> &#123;</span><br><span class="line">        System.out.println(joinPoint.getSignature().getName() + <span class="string">&quot;除法结束@After。。。&quot;</span>);</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="meta">@AfterReturning(value = &quot;pointCut()&quot;, returning = &quot;result&quot;)</span></span><br><span class="line">    <span class="keyword">public</span> <span class="keyword">void</span> <span class="title function_">logReturn</span><span class="params">(JoinPoint joinPoint, Object result)</span> &#123;</span><br><span class="line">        System.out.println(joinPoint.getSignature().getName() + <span class="string">&quot;除法正常返回@AfterReturning。。。运行结果 &quot;</span> + result);</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="meta">@AfterThrowing(value = &quot;pointCut()&quot;, throwing = &quot;e&quot;)</span></span><br><span class="line">    <span class="keyword">public</span> <span class="keyword">void</span> <span class="title function_">logException</span><span class="params">(JoinPoint joinPoint, Exception e)</span> &#123;</span><br><span class="line">        System.out.println(joinPoint.getSignature().getName() + <span class="string">&quot;除法异常@AfterThrowing。。。异常信息 &quot;</span> + e.getMessage());</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="meta">@Around(value = &quot;execution(public String com.moralok.bean.Car.getName(..))&quot;)</span></span><br><span class="line">    <span class="keyword">public</span> Object <span class="title function_">logAround</span><span class="params">(ProceedingJoinPoint joinPoint)</span> <span class="keyword">throws</span> Throwable &#123;</span><br><span class="line">        System.out.println(joinPoint.getSignature().getName() + <span class="string">&quot; @Around开始&quot;</span>);</span><br><span class="line">        <span class="type">Object</span> <span class="variable">proceed</span> <span class="operator">=</span> joinPoint.proceed();</span><br><span class="line">        System.out.println(joinPoint.getSignature().getName() + <span class="string">&quot; @Around结束&quot;</span>);</span><br><span class="line">        <span class="keyword">return</span> proceed;</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure></li>
-<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="meta">@EnableAspectJAutoProxy</span></span><br><span class="line"><span class="keyword">public</span> <span class="keyword">class</span> <span class="title class_">AopConfig</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> MathCalculator <span class="title function_">mathCalculator</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_">MathCalculator</span>();</span><br><span class="line">    &#125;</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> LogAspects <span class="title function_">logAspects</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_">LogAspects</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="keyword">public</span> <span class="keyword">class</span> <span class="title class_">AopTest</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">public</span> <span class="keyword">void</span> <span class="title function_">aopTest</span><span class="params">()</span> &#123;</span><br><span class="line">        <span class="type">AnnotationConfigApplicationContext</span> <span class="variable">ac</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">AnnotationConfigApplicationContext</span>(AopConfig.class);</span><br><span class="line">        <span class="type">MathCalculator</span> <span class="variable">mathCalculator</span> <span class="operator">=</span> ac.getBean(MathCalculator.class);</span><br><span class="line">        mathCalculator.div(<span class="number">1</span>, <span class="number">1</span>);</span><br><span class="line">        mathCalculator.div(<span class="number">1</span>, <span class="number">0</span>);</span><br><span class="line">        ac.close();</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure></li>
-<li>Debug 断点的判断条件（可选）<figure class="highlight console"><table><tr><td class="code"><pre><span class="line">beanName.equals(&quot;mathCalculator&quot;)</span><br></pre></td></tr></table></figure></li>
+<h3 id="Windows-监控"><a href="#Windows-监控" class="headerlink" title="Windows 监控"></a>Windows 监控</h3><h4 id="windows-exporter"><a href="#windows-exporter" class="headerlink" title="windows_exporter"></a>windows_exporter</h4><ul>
+<li><a href="https://github.com/prometheus-community/windows_exporter">windows_exporter Github 仓库</a></li>
+<li><a href="https://github.com/prometheus-community/windows_exporter/releases">windows_exporter 下载地址</a></li>
+<li><a href="https://prometheus.io/docs/guides/node-exporter/">windows_exporter 使用指南</a></li>
 </ul>
-<h2 id="创建代理-Bean-和创建普通-Bean-的区别"><a href="#创建代理-Bean-和创建普通-Bean-的区别" class="headerlink" title="创建代理 Bean 和创建普通 Bean 的区别"></a>创建代理 Bean 和创建普通 Bean 的区别</h2><p>其实创建代理 Bean 的过程和<a href="/2023/08/10/how-does-Spring-load-beans/" title="Spring Bean 加载过程">创建普通 Bean 的过程</a>直到进行初始化处理（initializeBean）前都是一样的。更具体地说，如很多资料所言，Spring 创建代理对象的工作，是在应用后置处理器阶段完成的。</p>
-<h3 id="常规的入口-getBean"><a href="#常规的入口-getBean" class="headerlink" title="常规的入口 getBean"></a>常规的入口 getBean</h3><p>mathCalculator 以 getBean 方法为起点，开始创建的过程。</p>
-<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="comment">// ...（mathCalculator）</span></span><br><span class="line">    getBean(beanName);</span><br><span class="line">    <span class="comment">// ...</span></span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
-
-<h3 id="应用后置处理器"><a href="#应用后置处理器" class="headerlink" title="应用后置处理器"></a>应用后置处理器</h3><p>在正常地实例化 Bean 后，初始化 Bean 时，会对 Bean 实例应用后置处理器。</p>
-<p>可是，<strong>究竟是哪一个后置处理器做的呢</strong>？</p>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">protected</span> Object <span class="title function_">initializeBean</span><span class="params">(<span class="keyword">final</span> String beanName, <span class="keyword">final</span> Object bean, RootBeanDefinition mbd)</span> &#123;</span><br><span class="line">    <span class="comment">// ...</span></span><br><span class="line">    wrappedBean = applyBeanPostProcessorsBeforeInitialization(wrappedBean, beanName);</span><br><span class="line">    <span class="comment">// ...</span></span><br><span class="line">    invokeInitMethods(beanName, wrappedBean, mbd);</span><br><span class="line">    <span class="comment">// ...</span></span><br><span class="line">    wrappedBean = applyBeanPostProcessorsAfterInitialization(wrappedBean, beanName);</span><br><span class="line">    <span class="keyword">return</span> wrappedBean;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+<h4 id="步骤-1"><a href="#步骤-1" class="headerlink" title="步骤"></a>步骤</h4><ol>
+<li>下载得到 windows_exporter-0.24.0-amd64.msi 安装程序。</li>
+<li>以默认方式安装</li>
+<li>Prometheus 配置文件<figure class="highlight yaml"><table><tr><td class="code"><pre><span class="line"><span class="attr">global:</span></span><br><span class="line">  <span class="attr">scrape_interval:</span> <span class="string">15s</span></span><br><span class="line"></span><br><span class="line"><span class="attr">scrape_configs:</span></span><br><span class="line"><span class="bullet">-</span> <span class="attr">job_name:</span> <span class="string">windows</span></span><br><span class="line"><span class="comment"># Windows</span></span><br><span class="line">  <span class="attr">static_configs:</span></span><br><span class="line">  <span class="bullet">-</span> <span class="attr">targets:</span> [<span class="string">&#x27;192.168.46.1:9182&#x27;</span>]</span><br></pre></td></tr></table></figure></li>
+</ol>
+<img src="/2023/11/18/setup-monitoring-using-grafana-and-prometheus/Snipaste_2023-11-19_01-16-05.png" class="" title="Windows 监控">
 
-<h3 id="AnnotationAwareAspectJAutoProxyCreator"><a href="#AnnotationAwareAspectJAutoProxyCreator" class="headerlink" title="AnnotationAwareAspectJAutoProxyCreator"></a>AnnotationAwareAspectJAutoProxyCreator</h3><p>在本示例中，创建代理的后置处理器就是 AnnotationAwareAspectJAutoProxyCreator，它继承自 AbstractAutoProxyCreator，AbstractAutoProxyCreator 实现了 BeanPostProcessor 接口。</p>
-<p>那么，<strong>它是什么时候，怎么加入到 beanFactory 中呢</strong>？</p>
-<p>PS: 显然，还有其他继承自 AbstractAutoProxyCreator 的后置处理器，暂时不谈。</p>
-<h4 id="BeanPostProcessor-的方法"><a href="#BeanPostProcessor-的方法" class="headerlink" title="BeanPostProcessor 的方法"></a>BeanPostProcessor 的方法</h4><p>postProcessBeforeInitialization 和 postProcessAfterInitialization 方法，前者什么都没做，后者在必要时对 Bean 进行包装。</p>
-<ul>
-<li><strong><code>AbstractAutoProxyCreator#postProcessAfterInitialization</code> 就是创建代理对象的入口。</strong></li>
-<li><strong>wrapIfNecessary 就是将 Bean 包装成代理 Bean 的入口方法</strong>。</li>
+<h3 id="Redis-监控"><a href="#Redis-监控" class="headerlink" title="Redis 监控"></a>Redis 监控</h3><h4 id="redis-exporter"><a href="#redis-exporter" class="headerlink" title="redis_exporter"></a>redis_exporter</h4><ul>
+<li><a href="https://github.com/oliver006/redis_exporter">redis_exporter Github 仓库</a></li>
+<li><a href="https://hub.docker.com/r/oliver006/redis_exporter/">redis_exporter Docker 官方镜像</a></li>
+<li><a href="https://hub.docker.com/r/oliver006/redis_exporter/">redis_exporter Docker bitnami 镜像</a></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_">AbstractAutoProxyCreator</span> <span class="keyword">extends</span> <span class="title class_">ProxyProcessorSupport</span></span><br><span class="line">    <span class="keyword">implements</span> <span class="title class_">SmartInstantiationAwareBeanPostProcessor</span>, BeanFactoryAware &#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_">postProcessBeforeInitialization</span><span class="params">(Object bean, String beanName)</span> &#123;</span><br><span class="line">        <span class="comment">// 什么都没做</span></span><br><span class="line">        <span class="keyword">return</span> bean;</span><br><span class="line">    &#125;</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_">postProcessAfterInitialization</span><span class="params">(Object bean, String beanName)</span> <span class="keyword">throws</span> BeansException &#123;</span><br><span class="line">        <span class="keyword">if</span> (bean != <span class="literal">null</span>) &#123;</span><br><span class="line">            <span class="type">Object</span> <span class="variable">cacheKey</span> <span class="operator">=</span> getCacheKey(bean.getClass(), beanName);</span><br><span class="line">            <span class="keyword">if</span> (!<span class="built_in">this</span>.earlyProxyReferences.contains(cacheKey)) &#123;</span><br><span class="line">                <span class="comment">// 如有必要，将 bean 包装成代理对象</span></span><br><span class="line">                <span class="keyword">return</span> wrapIfNecessary(bean, beanName, cacheKey);</span><br><span class="line">            &#125;</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 class="comment">// ...</span></span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+<h4 id="docker-compose-部署-2"><a href="#docker-compose-部署-2" class="headerlink" title="docker-compose 部署"></a>docker-compose 部署</h4><p>使用 bitnami 提供的镜像代替官方镜像并没有特殊考量。使用环境变量 REDIS_ADDR 指定目标 Redis。</p>
+<figure class="highlight yaml"><table><tr><td class="code"><pre><span class="line"><span class="attr">version:</span> <span class="string">&#x27;2&#x27;</span></span><br><span class="line"><span class="attr">services:</span></span><br><span class="line">  <span class="attr">redis:</span></span><br><span class="line">    <span class="attr">image:</span> <span class="string">&#x27;redis:4.0&#x27;</span></span><br><span class="line">    <span class="attr">container_name:</span> <span class="string">redis</span></span><br><span class="line">    <span class="attr">ports:</span></span><br><span class="line">      <span class="bullet">-</span> <span class="number">6379</span><span class="string">:6379</span></span><br><span class="line">    <span class="attr">volumes:</span></span><br><span class="line">      <span class="bullet">-</span> <span class="string">redis-data:/data</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 class="attr">redis-exporter:</span></span><br><span class="line">    <span class="attr">image:</span> <span class="string">bitnami/redis-exporter:1.55.0</span></span><br><span class="line">    <span class="attr">container_name:</span> <span class="string">redis-exporter</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 class="attr">environment:</span></span><br><span class="line">      <span class="bullet">-</span> <span class="string">REDIS_ADDR=redis://redis:6379</span></span><br><span class="line">    <span class="attr">depends_on:</span></span><br><span class="line">      <span class="bullet">-</span> <span class="string">redis</span></span><br><span class="line"></span><br><span class="line"><span class="attr">volumes:</span></span><br><span class="line">  <span class="attr">redis-data:</span></span><br><span class="line">    <span class="attr">driver:</span> <span class="string">local</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>
 
-<h2 id="创建代理-Bean-的过程"><a href="#创建代理-Bean-的过程" class="headerlink" title="创建代理 Bean 的过程"></a>创建代理 Bean 的过程</h2><h3 id="按需包装成代理-wrapIfNecessary"><a href="#按需包装成代理-wrapIfNecessary" class="headerlink" title="按需包装成代理 wrapIfNecessary"></a>按需包装成代理 wrapIfNecessary</h3><figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">protected</span> Object <span class="title function_">wrapIfNecessary</span><span class="params">(Object bean, String beanName, Object cacheKey)</span> &#123;</span><br><span class="line">    <span class="comment">// 判断是否直接返回 bean</span></span><br><span class="line">    <span class="keyword">if</span> (beanName != <span class="literal">null</span> &amp;&amp; <span class="built_in">this</span>.targetSourcedBeans.contains(beanName)) &#123;</span><br><span class="line">        <span class="keyword">return</span> bean;</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="keyword">if</span> (Boolean.FALSE.equals(<span class="built_in">this</span>.advisedBeans.get(cacheKey))) &#123;</span><br><span class="line">        <span class="keyword">return</span> bean;</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="keyword">if</span> (isInfrastructureClass(bean.getClass()) || shouldSkip(bean.getClass(), beanName)) &#123;</span><br><span class="line">        <span class="built_in">this</span>.advisedBeans.put(cacheKey, Boolean.FALSE);</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="comment">// 如果有适用于当前 bean 的 advise 则为其创建代理</span></span><br><span class="line">    Object[] specificInterceptors = getAdvicesAndAdvisorsForBean(bean.getClass(), beanName, <span class="literal">null</span>);</span><br><span class="line">    <span class="keyword">if</span> (specificInterceptors != DO_NOT_PROXY) &#123;</span><br><span class="line">        <span class="built_in">this</span>.advisedBeans.put(cacheKey, Boolean.TRUE);</span><br><span class="line">        <span class="type">Object</span> <span class="variable">proxy</span> <span class="operator">=</span> createProxy(</span><br><span class="line">                bean.getClass(), beanName, specificInterceptors, <span class="keyword">new</span> <span class="title class_">SingletonTargetSource</span>(bean));</span><br><span class="line">        <span class="built_in">this</span>.proxyTypes.put(cacheKey, proxy.getClass());</span><br><span class="line">        <span class="keyword">return</span> proxy;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="built_in">this</span>.advisedBeans.put(cacheKey, Boolean.FALSE);</span><br><span class="line">    <span class="keyword">return</span> bean;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+<img src="/2023/11/18/setup-monitoring-using-grafana-and-prometheus/Snipaste_2023-11-19_01-16-54.png" class="" title="Redis 监控">
 
-<h3 id="AbstractAutoProxyCreator-视角，创建代理"><a href="#AbstractAutoProxyCreator-视角，创建代理" class="headerlink" title="AbstractAutoProxyCreator 视角，创建代理"></a>AbstractAutoProxyCreator 视角，创建代理</h3><p>AbstractAutoProxyCreator#createProxy，创建一个 ProxyFactory，将工作交给它处理。</p>
-<ol>
-<li>创建一个代理工厂 ProxyFactory</li>
-<li>设置相关信息</li>
-<li>通过 ProxyFactory 获取代理</li>
+<h3 id="MySQL-监控"><a href="#MySQL-监控" class="headerlink" title="MySQL 监控"></a>MySQL 监控</h3><h4 id="mysqld-exporter"><a href="#mysqld-exporter" class="headerlink" title="mysqld_exporter"></a>mysqld_exporter</h4><ul>
+<li><a href="https://github.com/prometheus/mysqld_exporter">mysqld_exporter Github 仓库</a></li>
+<li><a href="https://registry.hub.docker.com/r/prom/mysqld-exporter/">mysqld_exporter Docker 官方镜像</a></li>
+</ul>
+<h4 id="docker-compose-部署-3"><a href="#docker-compose-部署-3" class="headerlink" title="docker-compose 部署"></a>docker-compose 部署</h4><ol>
+<li>使用 volume 将配置文件 .my.cnf 挂载到容器中</li>
+<li>使用 command 指定启动时的参数</li>
 </ol>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">protected</span> Object <span class="title function_">createProxy</span><span class="params">(</span></span><br><span class="line"><span class="params">        Class&lt;?&gt; beanClass, String beanName, Object[] specificInterceptors, TargetSource targetSource)</span> &#123;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">if</span> (<span class="built_in">this</span>.beanFactory <span class="keyword">instanceof</span> ConfigurableListableBeanFactory) &#123;</span><br><span class="line">        AutoProxyUtils.exposeTargetClass((ConfigurableListableBeanFactory) <span class="built_in">this</span>.beanFactory, beanName, beanClass);</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="type">ProxyFactory</span> <span class="variable">proxyFactory</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">ProxyFactory</span>();</span><br><span class="line">    proxyFactory.copyFrom(<span class="built_in">this</span>);</span><br><span class="line"></span><br><span class="line">    <span class="keyword">if</span> (!proxyFactory.isProxyTargetClass()) &#123;</span><br><span class="line">        <span class="keyword">if</span> (shouldProxyTargetClass(beanClass, beanName)) &#123;</span><br><span class="line">            proxyFactory.setProxyTargetClass(<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">            evaluateProxyInterfaces(beanClass, proxyFactory);</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    Advisor[] advisors = buildAdvisors(beanName, specificInterceptors);</span><br><span class="line">    proxyFactory.addAdvisors(advisors);</span><br><span class="line">    proxyFactory.setTargetSource(targetSource);</span><br><span class="line">    customizeProxyFactory(proxyFactory);</span><br><span class="line"></span><br><span class="line">    proxyFactory.setFrozen(<span class="built_in">this</span>.freezeProxy);</span><br><span class="line">    <span class="keyword">if</span> (advisorsPreFiltered()) &#123;</span><br><span class="line">        proxyFactory.setPreFiltered(<span class="literal">true</span>);</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">return</span> proxyFactory.getProxy(getProxyClassLoader());</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
-
-<h3 id="ProxyFactory-视角，获取代理"><a href="#ProxyFactory-视角，获取代理" class="headerlink" title="ProxyFactory 视角，获取代理"></a>ProxyFactory 视角，获取代理</h3><p>ProxyFactory#getProxy，创建一个 AopProxy 并委托它实现 getProxy。</p>
 <blockquote>
-<p>AopProxy 的含义与职责从字面上有点不好理解。</p>
+<p><strong>坑！！！</strong>在文档中找配置文件的默认挂载路径或者如何配置启动时的配置文件，找了好久都没找到。搭配上后来的坑，直接迷失数小时。</p>
 </blockquote>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> Object <span class="title function_">getProxy</span><span class="params">(ClassLoader classLoader)</span> &#123;</span><br><span class="line">    <span class="keyword">return</span> createAopProxy().getProxy(classLoader);</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
-
-<h4 id="ProxyFactor视角，创建-AopProxy"><a href="#ProxyFactor视角，创建-AopProxy" class="headerlink" title="ProxyFactor视角，创建 AopProxy"></a>ProxyFactor视角，创建 AopProxy</h4><p>ProxyFactory#createAopProxy，获取一个 AopProxyFactory 创建 AopProxy。</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">synchronized</span> AopProxy <span class="title function_">createAopProxy</span><span class="params">()</span> &#123;</span><br><span class="line">    <span class="keyword">if</span> (!<span class="built_in">this</span>.active) &#123;</span><br><span class="line">        activate();</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="comment">// 获取 AopProxy 工厂并创建一个 AopProxy</span></span><br><span class="line">    <span class="keyword">return</span> getAopProxyFactory().createAopProxy(<span class="built_in">this</span>);</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+<figure class="highlight yaml"><table><tr><td class="code"><pre><span class="line"><span class="attr">version:</span> <span class="string">&#x27;1.0&#x27;</span></span><br><span class="line"><span class="attr">services:</span></span><br><span class="line">  <span class="attr">mysql_57:</span></span><br><span class="line">    <span class="attr">image:</span> <span class="string">mysql:5.7</span></span><br><span class="line">    <span class="attr">container_name:</span> <span class="string">mysql_57</span></span><br><span class="line">    <span class="attr">ports:</span></span><br><span class="line">      <span class="bullet">-</span> <span class="number">13306</span><span class="string">:3306</span></span><br><span class="line">    <span class="attr">environment:</span></span><br><span class="line">      <span class="bullet">-</span> <span class="string">MYSQL_ROOT_PASSWORD=123456</span></span><br><span class="line">      <span class="bullet">-</span> <span class="string">TZ=Asia/Shanghai</span></span><br><span class="line">    <span class="attr">volumes:</span></span><br><span class="line">      <span class="bullet">-</span> <span class="string">/opt/mysql_5.7/data:/var/lib/mysql</span></span><br><span class="line">      <span class="bullet">-</span> <span class="string">/opt/mysql_5.7/conf/my.cnf:/etc/my.cnf</span></span><br><span class="line">      <span class="bullet">-</span> <span class="string">./sql:/docker-entrypoint-initdb.d</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 class="attr">mysqld-exporter:</span></span><br><span class="line">    <span class="attr">image:</span> <span class="string">prom/mysqld-exporter:v0.15.0</span></span><br><span class="line">    <span class="attr">container_name:</span> <span class="string">mysqld-exporter</span></span><br><span class="line">    <span class="attr">ports:</span></span><br><span class="line">      <span class="bullet">-</span> <span class="number">19104</span><span class="string">:9104</span></span><br><span class="line">    <span class="attr">volumes:</span></span><br><span class="line">      <span class="bullet">-</span> <span class="string">./exporter/.my.cnf:/cfg/.my.cnf</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 class="attr">command:</span> </span><br><span class="line">      <span class="bullet">-</span> <span class="string">--config.my-cnf=/cfg/.my.cnf</span></span><br><span class="line">    <span class="attr">depends_on:</span></span><br><span class="line">      <span class="bullet">-</span> <span class="string">mysql_57</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>
 
-<h4 id="AopProxyFactory视角，创建-AopProxy"><a href="#AopProxyFactory视角，创建-AopProxy" class="headerlink" title="AopProxyFactory视角，创建 AopProxy"></a>AopProxyFactory视角，创建 AopProxy</h4><p>AopProxyFactory#createAopProxy。</p>
-<ul>
-<li>AopProxyFactory 有且仅有一个默认实现 DefaultAopProxyFactory。</li>
-<li>createAopProxy 方法会根据配置信息，返回具体实现：开箱即用的有 JdkDynamicAopProxy 或者 ObjenesisCglibAopProxy。</li>
-</ul>
-<p>这里的处理，决定了 Spring AOP 会使用哪一种动态代理实现。比如 Spring AOP 默认使用 JDK 动态代理，如果目标对象实现了接口 Spring 会使用 JDK 动态代理，这些结论的依据就在于此。</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_">DefaultAopProxyFactory</span> <span class="keyword">implements</span> <span class="title class_">AopProxyFactory</span>, Serializable &#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> AopProxy <span class="title function_">createAopProxy</span><span class="params">(AdvisedSupport config)</span> <span class="keyword">throws</span> AopConfigException &#123;</span><br><span class="line">		<span class="keyword">if</span> (config.isOptimize() || config.isProxyTargetClass() || hasNoUserSuppliedProxyInterfaces(config)) &#123;</span><br><span class="line">			Class&lt;?&gt; targetClass = config.getTargetClass();</span><br><span class="line">			<span class="keyword">if</span> (targetClass == <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_">AopConfigException</span>(<span class="string">&quot;TargetSource cannot determine target class: &quot;</span> +</span><br><span class="line">						<span class="string">&quot;Either an interface or a target is required for proxy creation.&quot;</span>);</span><br><span class="line">			&#125;</span><br><span class="line">			<span class="keyword">if</span> (targetClass.isInterface() || Proxy.isProxyClass(targetClass)) &#123;</span><br><span class="line">				<span class="keyword">return</span> <span class="keyword">new</span> <span class="title class_">JdkDynamicAopProxy</span>(config);</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_">ObjenesisCglibAopProxy</span>(config);</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="keyword">new</span> <span class="title class_">JdkDynamicAopProxy</span>(config);</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="mysqld-exporter-配置文件"><a href="#mysqld-exporter-配置文件" class="headerlink" title="mysqld_exporter 配置文件"></a>mysqld_exporter 配置文件</h4><p>创建一个专用的 MySQL 用户。</p>
+<figure class="highlight plaintext"><table><tr><td class="code"><pre><span class="line">CREATE USER &#x27;exporter&#x27;@&#x27;localhost&#x27; IDENTIFIED BY &#x27;XXXXXXXX&#x27; WITH MAX_USER_CONNECTIONS 3;</span><br><span class="line">GRANT PROCESS, REPLICATION CLIENT, SELECT ON *.* TO &#x27;exporter&#x27;@&#x27;localhost&#x27;;</span><br></pre></td></tr></table></figure>
 
-<h3 id="获取代理-AopProxy-getProxy"><a href="#获取代理-AopProxy-getProxy" class="headerlink" title="获取代理 AopProxy#getProxy"></a>获取代理 AopProxy#getProxy</h3><p>AopProxy 视角，获取代理。</p>
-<h4 id="JDK-动态代理"><a href="#JDK-动态代理" class="headerlink" title="JDK 动态代理"></a>JDK 动态代理</h4><p>JdkDynamicAopProxy。</p>
-<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> Object <span class="title function_">getProxy</span><span class="params">(ClassLoader classLoader)</span> &#123;</span><br><span class="line">    <span class="comment">// ...</span></span><br><span class="line">    <span class="comment">// JDK 动态代理，已经和 Spring 无关</span></span><br><span class="line">    <span class="keyword">return</span> Proxy.newProxyInstance(classLoader, proxiedInterfaces, <span class="built_in">this</span>);</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+<figure class="highlight shell"><table><tr><td class="code"><pre><span class="line">[client]</span><br><span class="line">host=mysql_57</span><br><span class="line">port=3306</span><br><span class="line">user=exporter</span><br><span class="line">password=123456</span><br></pre></td></tr></table></figure>
 
-<h5 id="InvocationHandler-的-invoke-方法"><a href="#InvocationHandler-的-invoke-方法" class="headerlink" title="InvocationHandler 的 invoke 方法"></a>InvocationHandler 的 invoke 方法</h5><p>根据 <code>Proxy.newProxyInstance(classLoader, proxiedInterfaces, this)</code> 可知，this 也就是 JdkDynamicAopProxy 同时也是一个 InvocationHandler，它必然实现了 invoke 方法，当代理对象调用方法时，就会进入到 invoke 方法中。</p>
-<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> Object <span class="title function_">invoke</span><span class="params">(Object proxy, Method method, Object[] args)</span> <span class="keyword">throws</span> Throwable &#123;</span><br><span class="line">    <span class="comment">// ...</span></span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+<p><strong>坑！！！</strong>根据 <a href="https://github.com/prometheus/mysqld_exporter/releases/tag/v0.15.0">0.15.0 CHANGE LOG</a>，不再支持使用环境变量 DATA_SOURCE_NAME 设置 MySQL 的信息。Docker 镜像的文档未及时更新。需使用 <code>.my.cnf</code> 或命令行参数进行配置。<br>Docker 镜像文档更新不及时。</p>
+<figure class="highlight console"><table><tr><td class="code"><pre><span class="line">Error parsing host config&quot; file=.my.cnf err=&quot;no configuration found</span><br></pre></td></tr></table></figure>
 
-<h4 id="CGLib-动态代理"><a href="#CGLib-动态代理" class="headerlink" title="CGLib 动态代理"></a>CGLib 动态代理</h4><p>ObjenesisCglibAopProxy。</p>
-<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> Object <span class="title function_">getProxy</span><span class="params">(ClassLoader classLoader)</span> &#123;</span><br><span class="line">    <span class="comment">// ...</span></span><br><span class="line">    <span class="comment">// CGLib 动态代理，已经和 Spring 无关</span></span><br><span class="line">    <span class="type">Enhancer</span> <span class="variable">enhancer</span> <span class="operator">=</span> createEnhancer();</span><br><span class="line">    <span class="comment">// ...</span></span><br><span class="line">    <span class="keyword">return</span> createProxyClassAndInstance(enhancer, callbacks);</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+<p><strong>坑！！！</strong>带字符的复杂密码不能被正确解析。MySQL 使用了随机生成的复杂密码，怎么都连接不上。</p>
+<figure class="highlight console"><table><tr><td class="code"><pre><span class="line">caller=exporter.go:152 level=error msg=&quot;Error pinging mysqld&quot; err=&quot;Error 1045 (28000): Access denied for user &#x27;exporter&#x27;@&#x27;172.19.0.13&#x27; (using password: YES)&quot;</span><br></pre></td></tr></table></figure>
 
-<h5 id="为什么-Spring-中没有依赖-CGLib"><a href="#为什么-Spring-中没有依赖-CGLib" class="headerlink" title="为什么 Spring 中没有依赖 CGLib"></a>为什么 Spring 中没有依赖 CGLib</h5><p>你可能会注意到 Spring 中并没有直接依赖 CGLib，像 Enhancer 所在的包是 <code>org.springframework.cglib.proxy</code>。根据文档：</p>
 <blockquote>
-<p>从 spring 3.2 开始，不再需要将 cglib 添加到类路径中，因为 cglib 类在 org.springframework 下重新打包并分布在 spring-core jar 中。 这样做既是为了方便，也是为了避免与使用不同版本 cglib 的其他项目发生潜在冲突。</p>
+<p>数坑并发，搜遍全网，折腾半夜，痛不欲生。</p>
 </blockquote>
-<h2 id="创建代理前的准备"><a href="#创建代理前的准备" class="headerlink" title="创建代理前的准备"></a>创建代理前的准备</h2><p>在前面预留了一些问题，当初我在看网上的资料时就有这些困惑。</p>
-<h3 id="Bean-后置处理器-AspectJAwareAdvisorAutoProxyCreator-在什么时候，怎么加入到-beanFactory-中的？"><a href="#Bean-后置处理器-AspectJAwareAdvisorAutoProxyCreator-在什么时候，怎么加入到-beanFactory-中的？" class="headerlink" title="Bean 后置处理器 AspectJAwareAdvisorAutoProxyCreator 在什么时候，怎么加入到 beanFactory 中的？"></a>Bean 后置处理器 AspectJAwareAdvisorAutoProxyCreator 在什么时候，怎么加入到 beanFactory 中的？</h3><p>Debug 停留在 Spring 上下文刷新方法中的 finishBeanFactoryInitialization。</p>
-<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_">refresh</span><span class="params">()</span> <span class="keyword">throws</span> BeansException, IllegalStateException &#123;</span><br><span class="line">    <span class="comment">// ...</span></span><br><span class="line">    invokeBeanFactoryPostProcessors(beanFactory);</span><br><span class="line">    <span class="comment">// ...</span></span><br><span class="line">    finishBeanFactoryInitialization(beanFactory);</span><br><span class="line">    <span class="comment">// ...</span></span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
-
-<p>从 beanFatory 的 beanDefinitionMap 可以观察到，配置类 AopConfig 中的 MathCalculator 和 LogAspect 的信息已经就位。</p>
-<img src="/2023/11/19/how-does-Spring-AOP-create-proxy-beans/Snipaste_2023-11-20_15-51-48.png" class="" title="初始化 beanFactory 时的 beanDefinitionMap">
+<img src="/2023/11/18/setup-monitoring-using-grafana-and-prometheus/Snipaste_2023-11-19_01-17-25.png" class="" title="MySQL 监控">]]></content>
+      <tags>
+        <tag>grafana</tag>
+        <tag>prometheus</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>从 beanFactory 的 beanProcessor 可以观察到，AnnotationAwareAspectJAutoProxyCreator 已经就位。</p>
-<img src="/2023/11/19/how-does-Spring-AOP-create-proxy-beans/Snipaste_2023-11-20_15-56-15.png" class="" title="初始化 beanFactory 时的 beanPostProcessor">
+<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>
 
-<h4 id="EnableXXX-的魔法"><a href="#EnableXXX-的魔法" class="headerlink" title="@EnableXXX 的魔法"></a>@EnableXXX 的魔法</h4><p>注解 @EnableXXX 往往伴随着注解 @Import，在 invokeBeanFactoryPostProcessors(beanFactory) 中，工厂后置处理器 ConfigurationClassPostProcessor 会处理它。</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(AspectJAutoProxyRegistrar.class)</span></span><br><span class="line"><span class="keyword">public</span> <span class="meta">@interface</span> EnableAspectJAutoProxy &#123;</span><br><span class="line">    <span class="type">boolean</span> <span class="title function_">proxyTargetClass</span><span class="params">()</span> <span class="keyword">default</span> <span class="literal">false</span>;</span><br><span class="line">    <span class="type">boolean</span> <span class="title function_">exposeProxy</span><span class="params">()</span> <span class="keyword">default</span> <span class="literal">false</span>;</span><br><span class="line">&#125;</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">
 
-<p>在 ConfigurationClassPostProcessor 的处理中，因为 AspectJAutoProxyRegistrar 实现了 ImportBeanDefinitionRegistrar，registerBeanDefinitions 方法会被调用，AnnotationAwareAspectJAutoProxyCreator 的 beanDefinition 随之被注册到 beanFactory，因 AnnotationAwareAspectJAutoProxyCreator 实现了 BeanPostProcessor 被提前创建。</p>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">class</span> <span class="title class_">AspectJAutoProxyRegistrar</span> <span class="keyword">implements</span> <span class="title class_">ImportBeanDefinitionRegistrar</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_">registerBeanDefinitions</span><span class="params">(</span></span><br><span class="line"><span class="params">            AnnotationMetadata importingClassMetadata, BeanDefinitionRegistry registry)</span> &#123;</span><br><span class="line">        <span class="comment">// 如有必要注册 AspectJAnnotationAutoProxyCreator</span></span><br><span class="line">        AopConfigUtils.registerAspectJAnnotationAutoProxyCreatorIfNecessary(registry);</span><br><span class="line">        <span class="comment">// 根据配置设置一些属性</span></span><br><span class="line">        <span class="type">AnnotationAttributes</span> <span class="variable">enableAspectJAutoProxy</span> <span class="operator">=</span></span><br><span class="line">                AnnotationConfigUtils.attributesFor(importingClassMetadata, EnableAspectJAutoProxy.class);</span><br><span class="line">        <span class="keyword">if</span> (enableAspectJAutoProxy.getBoolean(<span class="string">&quot;proxyTargetClass&quot;</span>)) &#123;</span><br><span class="line">            AopConfigUtils.forceAutoProxyCreatorToUseClassProxying(registry);</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="keyword">if</span> (enableAspectJAutoProxy.getBoolean(<span class="string">&quot;exposeProxy&quot;</span>)) &#123;</span><br><span class="line">            AopConfigUtils.forceAutoProxyCreatorToExposeProxy(registry);</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>
 
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">static</span> BeanDefinition <span class="title function_">registerAspectJAnnotationAutoProxyCreatorIfNecessary</span><span class="params">(BeanDefinitionRegistry registry, Object source)</span> &#123;</span><br><span class="line">    <span class="keyword">return</span> registerOrEscalateApcAsRequired(AnnotationAwareAspectJAutoProxyCreator.class, registry, source);</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="切面类-LogAspect-的解析是在什么时候？"><a href="#切面类-LogAspect-的解析是在什么时候？" class="headerlink" title="切面类 LogAspect 的解析是在什么时候？"></a>切面类 LogAspect 的解析是在什么时候？</h3><p>进入创建 Bean 的方法 createBean 后，除了 doCreateBean，应额外留意 resolveBeforeInstantiation 方法。</p>
-<ol>
-<li><code>Object bean = resolveBeforeInstantiation(beanName, mbdToUse)</code>，在实例化前进行解析。</li>
-<li><code>Object beanInstance = doCreateBean(beanName, mbdToUse, args)</code>，创建 Bean 的具体过程。</li>
-</ol>
-<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">protected</span> Object <span class="title function_">createBean</span><span class="params">(String beanName, RootBeanDefinition mbd, Object[] args)</span> <span class="keyword">throws</span> BeanCreationException &#123; </span><br><span class="line">    <span class="comment">// ...</span></span><br><span class="line">    <span class="keyword">try</span> &#123;</span><br><span class="line">        <span class="type">Object</span> <span class="variable">bean</span> <span class="operator">=</span> resolveBeforeInstantiation(beanName, mbdToUse);</span><br><span class="line">        <span class="keyword">if</span> (bean != <span class="literal">null</span>) &#123;</span><br><span class="line">            <span class="keyword">return</span> bean;</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"></span><br><span class="line">    <span class="type">Object</span> <span class="variable">beanInstance</span> <span class="operator">=</span> doCreateBean(beanName, mbdToUse, args);</span><br><span class="line">    <span class="comment">// ...</span></span><br><span class="line">    <span class="keyword">return</span> beanInstance;</span><br><span class="line">&#125;</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="入口方法-resolveBeforeInstantiation"><a href="#入口方法-resolveBeforeInstantiation" class="headerlink" title="入口方法 resolveBeforeInstantiation"></a>入口方法 resolveBeforeInstantiation</h4><p>根据注释，该方法给 BeanPostProcessors 一个机会提前返回一个代理对象。在本示例中，返回 null，但是方法在第一次执行后已经提前解析得到 advisors 并缓存。</p>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">protected</span> Object <span class="title function_">resolveBeforeInstantiation</span><span class="params">(String beanName, RootBeanDefinition mbd)</span> &#123;</span><br><span class="line">    <span class="type">Object</span> <span class="variable">bean</span> <span class="operator">=</span> <span class="literal">null</span>;</span><br><span class="line">    <span class="keyword">if</span> (!Boolean.FALSE.equals(mbd.beforeInstantiationResolved)) &#123;</span><br><span class="line">        <span class="keyword">if</span> (!mbd.isSynthetic() &amp;&amp; hasInstantiationAwareBeanPostProcessors()) &#123;</span><br><span class="line">            Class&lt;?&gt; targetType = determineTargetType(beanName, mbd);</span><br><span class="line">            <span class="keyword">if</span> (targetType != <span class="literal">null</span>) &#123;</span><br><span class="line">                <span class="comment">// 注意，应用的是实例化前的处理</span></span><br><span class="line">                bean = applyBeanPostProcessorsBeforeInstantiation(targetType, beanName);</span><br><span class="line">                <span class="keyword">if</span> (bean != <span class="literal">null</span>) &#123;</span><br><span class="line">                    <span class="comment">// 注意，应用的是初始化后的处理</span></span><br><span class="line">                    bean = applyBeanPostProcessorsAfterInitialization(bean, beanName);</span><br><span class="line">                &#125;</span><br><span class="line">            &#125;</span><br><span class="line">        &#125;</span><br><span class="line">        mbd.beforeInstantiationResolved = (bean != <span class="literal">null</span>);</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></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>
 
-<h4 id="InstantiationAwareBeanPostProcessor"><a href="#InstantiationAwareBeanPostProcessor" class="headerlink" title="InstantiationAwareBeanPostProcessor"></a>InstantiationAwareBeanPostProcessor</h4><p>应用 InstantiationAwareBeanPostProcessor 的 postProcessBeforeInstantiation。</p>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">protected</span> Object <span class="title function_">applyBeanPostProcessorsBeforeInstantiation</span><span class="params">(Class&lt;?&gt; beanClass, String beanName)</span> &#123;</span><br><span class="line">    <span class="keyword">for</span> (BeanPostProcessor bp : getBeanPostProcessors()) &#123;</span><br><span class="line">        <span class="keyword">if</span> (bp <span class="keyword">instanceof</span> InstantiationAwareBeanPostProcessor) &#123;</span><br><span class="line">            <span class="type">InstantiationAwareBeanPostProcessor</span> <span class="variable">ibp</span> <span class="operator">=</span> (InstantiationAwareBeanPostProcessor) bp;</span><br><span class="line">            <span class="comment">// 循环依次处理</span></span><br><span class="line">            <span class="type">Object</span> <span class="variable">result</span> <span class="operator">=</span> ibp.postProcessBeforeInstantiation(beanClass, beanName);</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">return</span> <span class="literal">null</span>;</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>
 
-<p>AnnotationAwareAspectJAutoProxyCreator 不仅仅是一个 BeanPostProcessor，它还是一个 InstantiationAwareBeanPostProcessor。</p>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> Object <span class="title function_">postProcessBeforeInstantiation</span><span class="params">(Class&lt;?&gt; beanClass, String beanName)</span> <span class="keyword">throws</span> BeansException &#123;</span><br><span class="line">    <span class="type">Object</span> <span class="variable">cacheKey</span> <span class="operator">=</span> getCacheKey(beanClass, beanName);</span><br><span class="line">    </span><br><span class="line">    <span class="keyword">if</span> (beanName == <span class="literal">null</span> || !<span class="built_in">this</span>.targetSourcedBeans.contains(beanName)) &#123;</span><br><span class="line">        <span class="keyword">if</span> (<span class="built_in">this</span>.advisedBeans.containsKey(cacheKey)) &#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">if</span> (isInfrastructureClass(beanClass) || shouldSkip(beanClass, beanName)) &#123;</span><br><span class="line">            <span class="built_in">this</span>.advisedBeans.put(cacheKey, Boolean.FALSE);</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">    </span><br><span class="line">    <span class="keyword">if</span> (beanName != <span class="literal">null</span>) &#123;</span><br><span class="line">        <span class="type">TargetSource</span> <span class="variable">targetSource</span> <span class="operator">=</span> getCustomTargetSource(beanClass, beanName);</span><br><span class="line">        <span class="keyword">if</span> (targetSource != <span class="literal">null</span>) &#123;</span><br><span class="line">            <span class="built_in">this</span>.targetSourcedBeans.add(beanName);</span><br><span class="line">            Object[] specificInterceptors = getAdvicesAndAdvisorsForBean(beanClass, beanName, targetSource);</span><br><span class="line">            <span class="type">Object</span> <span class="variable">proxy</span> <span class="operator">=</span> createProxy(beanClass, beanName, specificInterceptors, targetSource);</span><br><span class="line">            <span class="built_in">this</span>.proxyTypes.put(cacheKey, proxy.getClass());</span><br><span class="line">            <span class="keyword">return</span> proxy;</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>
+<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>和 wrapIfNecessary 方法对比，容易发现两者有不少相似的处理。</p>
-<img src="/2023/11/19/how-does-Spring-AOP-create-proxy-beans/Snipaste_2023-11-20_21-33-34.png" class="" title="实例化前后创建代理的对比">
+<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>
 
-<blockquote>
-<p><strong>注意：以下方法应注意是否被子类重写</strong>。</p>
-</blockquote>
-<p>org.springframework.aop.aspectj.autoproxy.AspectJAwareAdvisorAutoProxyCreator#shouldSkip</p>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">protected</span> <span class="type">boolean</span> <span class="title function_">shouldSkip</span><span class="params">(Class&lt;?&gt; beanClass, String beanName)</span> &#123;</span><br><span class="line">    <span class="comment">// 查找并缓存 advisors</span></span><br><span class="line">    List&lt;Advisor&gt; candidateAdvisors = findCandidateAdvisors();</span><br><span class="line">    <span class="comment">// ...</span></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>org.springframework.aop.framework.autoproxy.AbstractAdvisorAutoProxyCreator#getAdvicesAndAdvisorsForBean</p>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">protected</span> Object[] getAdvicesAndAdvisorsForBean(Class&lt;?&gt; beanClass, String beanName, TargetSource targetSource) &#123;</span><br><span class="line">    List&lt;Advisor&gt; advisors = findEligibleAdvisors(beanClass, beanName);</span><br><span class="line">    <span class="comment">// ...</span></span><br><span class="line">&#125;</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">
 
-<p>org.springframework.aop.framework.autoproxy.AbstractAdvisorAutoProxyCreator#findEligibleAdvisors</p>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">protected</span> List&lt;Advisor&gt; <span class="title function_">findEligibleAdvisors</span><span class="params">(Class&lt;?&gt; beanClass, String beanName)</span> &#123;</span><br><span class="line">    <span class="comment">// 查找并缓存 advisors</span></span><br><span class="line">    List&lt;Advisor&gt; candidateAdvisors = findCandidateAdvisors();</span><br><span class="line">    <span class="comment">// ...</span></span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+<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>容易注意到两者在创建代理前，<strong>都会调用 findCandidateAdvisors 方法查找候选的 advisors</strong>，其实这也是我们想要找的对切面类的解析处理所在。</p>
-<h4 id="查找并缓存-advisors"><a href="#查找并缓存-advisors" class="headerlink" title="查找并缓存 advisors"></a>查找并缓存 advisors</h4><p>org.springframework.aop.aspectj.annotation.AnnotationAwareAspectJAutoProxyCreator#findCandidateAdvisors</p>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">protected</span> List&lt;Advisor&gt; <span class="title function_">findCandidateAdvisors</span><span class="params">()</span> &#123;</span><br><span class="line">    List&lt;Advisor&gt; advisors = <span class="built_in">super</span>.findCandidateAdvisors();</span><br><span class="line">    advisors.addAll(<span class="built_in">this</span>.aspectJAdvisorsBuilder.buildAspectJAdvisors());</span><br><span class="line">    <span class="keyword">return</span> advisors;</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>
 
-<p>org.springframework.aop.aspectj.annotation.BeanFactoryAspectJAdvisorsBuilder#buildAspectJAdvisors</p>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> List&lt;Advisor&gt; <span class="title function_">buildAspectJAdvisors</span><span class="params">()</span> &#123;</span><br><span class="line">    List&lt;String&gt; aspectNames = <span class="built_in">this</span>.aspectBeanNames;  </span><br><span class="line">    <span class="keyword">if</span> (aspectNames == <span class="literal">null</span>) &#123;</span><br><span class="line">        <span class="comment">// 第一次进入，没有缓存</span></span><br><span class="line">        <span class="keyword">synchronized</span> (<span class="built_in">this</span>) &#123;</span><br><span class="line">            aspectNames = <span class="built_in">this</span>.aspectBeanNames;</span><br><span class="line">            <span class="keyword">if</span> (aspectNames == <span class="literal">null</span>) &#123;</span><br><span class="line">                List&lt;Advisor&gt; advisors = <span class="keyword">new</span> <span class="title class_">LinkedList</span>&lt;Advisor&gt;();</span><br><span class="line">                aspectNames = <span class="keyword">new</span> <span class="title class_">LinkedList</span>&lt;String&gt;();</span><br><span class="line">                String[] beanNames = BeanFactoryUtils.beanNamesForTypeIncludingAncestors(</span><br><span class="line">                        <span class="built_in">this</span>.beanFactory, Object.class, <span class="literal">true</span>, <span class="literal">false</span>);</span><br><span class="line">                <span class="keyword">for</span> (String beanName : beanNames) &#123;</span><br><span class="line">                    <span class="comment">// ...</span></span><br><span class="line">                    <span class="comment">// 如果是切面，解析得到 advisors</span></span><br><span class="line">                    <span class="keyword">if</span> (<span class="built_in">this</span>.advisorFactory.isAspect(beanType)) &#123;</span><br><span class="line">                        aspectNames.add(beanName);</span><br><span class="line">                        <span class="comment">// ...</span></span><br><span class="line">                        <span class="keyword">if</span> (<span class="built_in">this</span>.beanFactory.isSingleton(beanName)) &#123;</span><br><span class="line">                            <span class="built_in">this</span>.advisorsCache.put(beanName, classAdvisors);</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>.aspectFactoryCache.put(beanName, factory);</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="built_in">this</span>.aspectBeanNames = aspectNames;</span><br><span class="line">                <span class="keyword">return</span> advisors;</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">if</span> (aspectNames.isEmpty()) &#123;</span><br><span class="line">        <span class="keyword">return</span> Collections.emptyList();</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="comment">// 以后进来读缓存</span></span><br><span class="line">    List&lt;Advisor&gt; advisors = <span class="keyword">new</span> <span class="title class_">LinkedList</span>&lt;Advisor&gt;();</span><br><span class="line">    <span class="keyword">for</span> (String aspectName : aspectNames) &#123;</span><br><span class="line">        List&lt;Advisor&gt; cachedAdvisors = <span class="built_in">this</span>.advisorsCache.get(aspectName);</span><br><span class="line">        <span class="keyword">if</span> (cachedAdvisors != <span class="literal">null</span>) &#123;</span><br><span class="line">            advisors.addAll(cachedAdvisors);</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="keyword">else</span> &#123;</span><br><span class="line">            <span class="type">MetadataAwareAspectInstanceFactory</span> <span class="variable">factory</span> <span class="operator">=</span> <span class="built_in">this</span>.aspectFactoryCache.get(aspectName);</span><br><span class="line">            advisors.addAll(<span class="built_in">this</span>.advisorFactory.getAdvisors(factory));</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="keyword">return</span> advisors;</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>
 
-<p>可以通过 <code>beanFactory-&gt;beanPostProcessors-&gt;aspectJAdvisorsBuilder-&gt;advisorsCache</code> 观察 advisors 的查找情况。</p>
-<img src="/2023/11/19/how-does-Spring-AOP-create-proxy-beans/Snipaste_2023-11-20_20-50-04.png" class="" title="观察 advisors">]]></content>
+<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>
+<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>《Redis 深度历险，核心原理与应用实践》</li>
+</ul>
+]]></content>
       <tags>
-        <tag>java</tag>
-        <tag>spring</tag>
-        <tag>aop</tag>
+        <tag>distributed lock</tag>
+        <tag>redis</tag>
       </tags>
   </entry>
   <entry>
@@ -2281,335 +2338,202 @@
 
 <figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> Object <span class="title function_">resolveValueIfNecessary</span><span class="params">(Object argName, Object value)</span> &#123;</span><br><span class="line">    <span class="comment">// ...</span></span><br><span class="line">    <span class="comment">// 如果是 RuntimeBeanReference 类型，就解析引用</span></span><br><span class="line">    <span class="keyword">if</span> (value <span class="keyword">instanceof</span> RuntimeBeanReference) &#123;</span><br><span class="line">        <span class="type">RuntimeBeanReference</span> <span class="variable">ref</span> <span class="operator">=</span> (RuntimeBeanReference) value;</span><br><span class="line">        <span class="keyword">return</span> resolveReference(argName, ref);</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>
 
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">private</span> Object <span class="title function_">resolveReference</span><span class="params">(Object argName, RuntimeBeanReference ref)</span> &#123;</span><br><span class="line">    <span class="comment">// ...</span></span><br><span class="line">    <span class="comment">// 解析引用将调用 getBean</span></span><br><span class="line">    <span class="type">Object</span> <span class="variable">bean</span> <span class="operator">=</span> <span class="built_in">this</span>.beanFactory.getBean(refName);</span><br><span class="line">    <span class="built_in">this</span>.beanFactory.registerDependentBean(refName, <span class="built_in">this</span>.beanName);</span><br><span class="line">    <span class="keyword">return</span> bean;</span><br><span class="line">    <span class="comment">// ...</span></span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
-
-<h3 id="获取-circularB"><a href="#获取-circularB" class="headerlink" title="获取 circularB"></a>获取 circularB</h3><p>AbstractBeanFactory#doGetBean(circularB)，获取 circularB 将经过和 circularA 一样的流程，进入 populateBean(circularB) 对其进行依赖注入，进而再次去获取 circularA。</p>
-<h2 id="第二次获取-circularA"><a href="#第二次获取-circularA" class="headerlink" title="第二次获取 circularA"></a>第二次获取 circularA</h2><h3 id="doGetBean-circularA-1"><a href="#doGetBean-circularA-1" class="headerlink" title="doGetBean(circularA)"></a>doGetBean(circularA)</h3><ol>
-<li>第二次获取 circularA 时，仍然先尝试从缓存中获取</li>
-<li>这次将从缓存中得到先前创建的 circularA。</li>
-</ol>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">protected</span> &lt;T&gt; T <span class="title function_">doGetBean</span><span class="params">(</span></span><br><span class="line"><span class="params">        <span class="keyword">final</span> String name, <span class="keyword">final</span> Class&lt;T&gt; requiredType, <span class="keyword">final</span> Object[] args, <span class="type">boolean</span> typeCheckOnly)</span></span><br><span class="line">        <span class="keyword">throws</span> BeansException &#123;</span><br><span class="line">    <span class="comment">// ...</span></span><br><span class="line">    <span class="comment">// 尝试从缓存中获取 circularA，结果为 null</span></span><br><span class="line">    <span class="type">Object</span> <span class="variable">sharedInstance</span> <span class="operator">=</span> getSingleton(beanName);</span><br><span class="line">    <span class="comment">// ...</span></span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
-
-<p>在第一次获取 circularA 时，我们跳过了查看 getSingleton(String) 的代码。其实代码的逻辑并不复杂，但是要理解为什么这么做，却需要回过头来反复品味和思考。</p>
-<h3 id="从缓存中获取-circularA"><a href="#从缓存中获取-circularA" class="headerlink" title="从缓存中获取 circularA"></a>从缓存中获取 circularA</h3><figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">protected</span> Object <span class="title function_">getSingleton</span><span class="params">(String beanName, <span class="type">boolean</span> allowEarlyReference)</span> &#123;</span><br><span class="line">    <span class="type">Object</span> <span class="variable">singletonObject</span> <span class="operator">=</span> <span class="built_in">this</span>.singletonObjects.get(beanName);</span><br><span class="line">    <span class="comment">// 如果 singletonObjects 中不存在，且 bean 正在创建过程中</span></span><br><span class="line">    <span class="keyword">if</span> (singletonObject == <span class="literal">null</span> &amp;&amp; isSingletonCurrentlyInCreation(beanName)) &#123;</span><br><span class="line">        <span class="keyword">synchronized</span> (<span class="built_in">this</span>.singletonObjects) &#123;</span><br><span class="line">            <span class="comment">// 从 earlySingletonObjects 获取</span></span><br><span class="line">            singletonObject = <span class="built_in">this</span>.earlySingletonObjects.get(beanName);</span><br><span class="line">            <span class="keyword">if</span> (singletonObject == <span class="literal">null</span> &amp;&amp; allowEarlyReference) &#123;</span><br><span class="line">                <span class="comment">// 如果 earlySingletonObjects 中不存在，且允许早期引用，就从 singletonFactories 中获取</span></span><br><span class="line">                ObjectFactory&lt;?&gt; singletonFactory = <span class="built_in">this</span>.singletonFactories.get(beanName);</span><br><span class="line">                <span class="keyword">if</span> (singletonFactory != <span class="literal">null</span>) &#123;</span><br><span class="line">                    singletonObject = singletonFactory.getObject();</span><br><span class="line">                    <span class="built_in">this</span>.earlySingletonObjects.put(beanName, singletonObject);</span><br><span class="line">                    <span class="built_in">this</span>.singletonFactories.remove(beanName);</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="keyword">return</span> (singletonObject != NULL_OBJECT ? singletonObject : <span class="literal">null</span>);</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
-
-<ol>
-<li>从 singletonObjects（一级缓存） 获取 circularA，不存在</li>
-<li>circularA 属于正在创建中，从 earlySingletonObjects（二级缓存） 获取，仍然不存在</li>
-<li>allowEarlyReference 为真，从 singletonFactories（三级缓存） 获取（circularA 实例化后被包装为 ObjectFactory 保存在这里）</li>
-<li>调用 getObject 获得对象</li>
-</ol>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line">addSingletonFactory(beanName, <span class="keyword">new</span> <span class="title class_">ObjectFactory</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_">getObject</span><span class="params">()</span> <span class="keyword">throws</span> BeansException &#123;</span><br><span class="line">        <span class="keyword">return</span> getEarlyBeanReference(beanName, mbd, bean);</span><br><span class="line">    &#125;</span><br><span class="line">&#125;);</span><br></pre></td></tr></table></figure>
-
-<h3 id="回调-getEarlyBeanReference"><a href="#回调-getEarlyBeanReference" class="headerlink" title="回调 getEarlyBeanReference"></a>回调 getEarlyBeanReference</h3><p>如果存在 SmartInstantiationAwareBeanPostProcessor，将使用这些后处理器获得早期 bean 引用。</p>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">protected</span> Object <span class="title function_">getEarlyBeanReference</span><span class="params">(String beanName, RootBeanDefinition mbd, Object bean)</span> &#123;</span><br><span class="line">    <span class="type">Object</span> <span class="variable">exposedObject</span> <span class="operator">=</span> bean;</span><br><span class="line">    <span class="keyword">if</span> (bean != <span class="literal">null</span> &amp;&amp; !mbd.isSynthetic() &amp;&amp; hasInstantiationAwareBeanPostProcessors()) &#123;</span><br><span class="line">        <span class="comment">// 如果存在 InstantiationAwareBeanPostProcessors</span></span><br><span class="line">        <span class="keyword">for</span> (BeanPostProcessor bp : getBeanPostProcessors()) &#123;</span><br><span class="line">            <span class="keyword">if</span> (bp <span class="keyword">instanceof</span> SmartInstantiationAwareBeanPostProcessor) &#123;</span><br><span class="line">                <span class="comment">// 如果 bp 是 SmartInstantiationAwareBeanPostProcessor 类型</span></span><br><span class="line">                <span class="type">SmartInstantiationAwareBeanPostProcessor</span> <span class="variable">ibp</span> <span class="operator">=</span> (SmartInstantiationAwareBeanPostProcessor) bp;</span><br><span class="line">                <span class="comment">// 尝试创建代理</span></span><br><span class="line">                exposedObject = ibp.getEarlyBeanReference(exposedObject, beanName);</span><br><span class="line">                <span class="keyword">if</span> (exposedObject == <span class="literal">null</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">            &#125;</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="keyword">return</span> exposedObject;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
-
-<h3 id="获取早期-bean-引用"><a href="#获取早期-bean-引用" class="headerlink" title="获取早期 bean 引用"></a>获取早期 bean 引用</h3><p>了解<a href="/2023/11/19/how-does-Spring-AOP-create-proxy-beans/" title="Spring AOP 如何创建代理 beans">Spring AOP 如何创建代理 beans</a>，才能更好地理解这部分内容。</p>
-<p>通过后处理器 getEarlyBeanReference 获取早期 bean 引用时，可能返回的就是 circularA 对象，但是如果 circularA 属于需要创建代理的 bean，就会在这时候立即为它创建代理，而在之后 BeanPostProcessor 处理时就不会再创建代理了。</p>
-<p>以 AbstractAutoProxyCreator 为例，它是自动代理创建者的抽象类，同时实现了 SmartInstantiationAwareBeanPostProcessor 和 BeanPostProcessor 接口。</p>
-<h4 id="SmartInstantiationAwareBeanPostProcessor-的方法实现"><a href="#SmartInstantiationAwareBeanPostProcessor-的方法实现" class="headerlink" title="SmartInstantiationAwareBeanPostProcessor 的方法实现"></a>SmartInstantiationAwareBeanPostProcessor 的方法实现</h4><p>SmartInstantiationAwareBeanPostProcessor 接口允许在获取 circularA 的早期引用时，就尝试将 circular A 包装为代理。</p>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> Object <span class="title function_">getEarlyBeanReference</span><span class="params">(Object bean, String beanName)</span> <span class="keyword">throws</span> BeansException &#123;</span><br><span class="line">    <span class="type">Object</span> <span class="variable">cacheKey</span> <span class="operator">=</span> getCacheKey(bean.getClass(), beanName);</span><br><span class="line">    <span class="keyword">if</span> (!<span class="built_in">this</span>.earlyProxyReferences.contains(cacheKey)) &#123;</span><br><span class="line">        <span class="built_in">this</span>.earlyProxyReferences.add(cacheKey);</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="comment">// 如有必要，包装为代理</span></span><br><span class="line">    <span class="keyword">return</span> wrapIfNecessary(bean, beanName, cacheKey);</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
-
-<h4 id="BeanPostProcessor-的方法实现"><a href="#BeanPostProcessor-的方法实现" class="headerlink" title="BeanPostProcessor 的方法实现"></a>BeanPostProcessor 的方法实现</h4><p>BeanPostProcessor 接口允许在初始化时，调用初始化方法后，尝试将 circular A 包装为代理。如果已经在获取 circularA 的早期引用时就将其包装为代理，则不再进行包装。</p>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> Object <span class="title function_">postProcessAfterInitialization</span><span class="params">(Object bean, String beanName)</span> <span class="keyword">throws</span> BeansException &#123;</span><br><span class="line">    <span class="keyword">if</span> (bean != <span class="literal">null</span>) &#123;</span><br><span class="line">        <span class="type">Object</span> <span class="variable">cacheKey</span> <span class="operator">=</span> getCacheKey(bean.getClass(), beanName);</span><br><span class="line">        <span class="comment">// 判断早期代理引用中是否存在</span></span><br><span class="line">        <span class="keyword">if</span> (!<span class="built_in">this</span>.earlyProxyReferences.contains(cacheKey)) &#123;</span><br><span class="line">            <span class="keyword">return</span> wrapIfNecessary(bean, beanName, cacheKey);</span><br><span class="line">        &#125;</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></pre></td></tr></table></figure>
-
-<h2 id="再思-Spring-bean-的三级缓存"><a href="#再思-Spring-bean-的三级缓存" class="headerlink" title="再思 Spring bean 的三级缓存"></a>再思 Spring bean 的三级缓存</h2><h3 id="三级缓存还是三个缓存"><a href="#三级缓存还是三个缓存" class="headerlink" title="三级缓存还是三个缓存"></a>三级缓存还是三个缓存</h3><p>著名的“三级缓存”，实际上就是三个存放 Bean 的 map：</p>
-<ul>
-<li>singletonObjects</li>
-<li>earlySingletonObjects</li>
-<li>singletonFactories</li>
-</ul>
-<p>在很多网上的资料中，都称 Spring 通过使用三级缓存的设计解决了循环引用问题。<br>同时我也看到有人反思，这样翻译对学习者造成了很大的困扰，代码中并没有多级 cache 的意味，称之为“三个缓存”比“三级缓存”更合理也更容易理解。<br>三个存放 Bean 的 map 事实上是相互独立的，甚至说它们是互斥的，<strong>一个 Bean 在同一时间最多只能存在于其中一个 map 中</strong>。</p>
-<p>对我个人而言，我对反对者的观点深有同感，如果我没有看过面经，即使我熟读并理解代码，我可能都无法回答 Spring 中的三级缓存是什么。甚至我会被三级缓存这个名词所震慑，在了解它之前在心里放大它的复杂性。<br>但是在不断阅读的过程中（可能也有已有记忆的加持），我也会感受到称之为“三级缓存”的合理性。这里的分级含义更多体现的是 Bean 的“晋升”过程。</p>
-<h3 id="缓存中的添加和删除"><a href="#缓存中的添加和删除" class="headerlink" title="缓存中的添加和删除"></a>缓存中的添加和删除</h3><p>网上很多资料在讨论 Bean 在缓存中的添加和删除时，大多一笔带过，并没有谈到细节。但是 Bean 并不是在这三个缓存中连续晋级，甚至有时候，添加和移除的都不是一个对象。</p>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">protected</span> Object <span class="title function_">doCreateBean</span><span class="params">(<span class="keyword">final</span> String beanName, <span class="keyword">final</span> RootBeanDefinition mbd, <span class="keyword">final</span> Object[] args)</span></span><br><span class="line">        <span class="keyword">throws</span> BeanCreationException &#123;</span><br><span class="line">    <span class="comment">// 实例化</span></span><br><span class="line">    instanceWrapper = createBeanInstance(beanName, mbd, args);</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 单例+允许循环引用+当前正在被创建=可能需要提前暴露</span></span><br><span class="line">    <span class="type">boolean</span> <span class="variable">earlySingletonExposure</span> <span class="operator">=</span> (mbd.isSingleton() &amp;&amp; <span class="built_in">this</span>.allowCircularReferences &amp;&amp;</span><br><span class="line">            isSingletonCurrentlyInCreation(beanName));</span><br><span class="line">    <span class="keyword">if</span> (earlySingletonExposure) &#123;</span><br><span class="line">        addSingletonFactory(beanName, <span class="keyword">new</span> <span class="title class_">ObjectFactory</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_">getObject</span><span class="params">()</span> <span class="keyword">throws</span> BeansException &#123;</span><br><span class="line">                <span class="keyword">return</span> getEarlyBeanReference(beanName, mbd, bean);</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="type">Object</span> <span class="variable">exposedObject</span> <span class="operator">=</span> bean;</span><br><span class="line">    <span class="keyword">try</span> &#123;</span><br><span class="line">        <span class="comment">// 这里面会进行依赖注入</span></span><br><span class="line">        populateBean(beanName, mbd, instanceWrapper);</span><br><span class="line">        <span class="keyword">if</span> (exposedObject != <span class="literal">null</span>) &#123;</span><br><span class="line">            <span class="comment">// 这里面会尝试创建代理</span></span><br><span class="line">            exposedObject = initializeBean(beanName, exposedObject, mbd);</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> (earlySingletonExposure) &#123;</span><br><span class="line">        <span class="comment">// 如果允许早期暴露，尝试获取早期 bean 引用</span></span><br><span class="line">        <span class="type">Object</span> <span class="variable">earlySingletonReference</span> <span class="operator">=</span> getSingleton(beanName, <span class="literal">false</span>);</span><br><span class="line">        <span class="comment">// 如果为 null 说明没有早期暴露，返回的其实还是最初的 exposedObject</span></span><br><span class="line">        <span class="comment">// 三级缓存里的 ObjectFactory 完全没用上，会在 exposedObject 添加到一级缓存时直接删除</span></span><br><span class="line">        <span class="keyword">if</span> (earlySingletonReference != <span class="literal">null</span>) &#123;</span><br><span class="line">            <span class="comment">// 如果不为 null，说明确实早期暴露过</span></span><br><span class="line">            <span class="keyword">if</span> (exposedObject == bean) &#123;</span><br><span class="line">                <span class="comment">// 如果早期暴露过，常规情况下，exposedObject 不会再创建代理，应 == bean</span></span><br><span class="line">                <span class="comment">// 如果没有代理，exposedObject == bean == earlySingletonReference</span></span><br><span class="line">                <span class="comment">// 如果创建过代理，earlySingletonReference 才是包装过的代理</span></span><br><span class="line">                exposedObject = earlySingletonReference;</span><br><span class="line">            &#125;</span><br><span class="line">            <span class="keyword">else</span> <span class="keyword">if</span> (!<span class="built_in">this</span>.allowRawInjectionDespiteWrapping &amp;&amp; hasDependentBean(beanName)) &#123;</span><br><span class="line">                <span class="comment">// 如果 exposedObject 在 initializeBean 中再次被创建代理</span></span><br><span class="line">                <span class="comment">// 但是存在 Bean 依赖了这个 Bean（由于拿到的是早期引用），它们拿到的和最终的是不同的对象</span></span><br><span class="line">                <span class="comment">// 如果不允许尽管会被包装仍然注入原始类型，就需要抛出异常</span></span><br><span class="line">                String[] dependentBeans = getDependentBeans(beanName);</span><br><span class="line">                Set&lt;String&gt; actualDependentBeans = <span class="keyword">new</span> <span class="title class_">LinkedHashSet</span>&lt;String&gt;(dependentBeans.length);</span><br><span class="line">                <span class="keyword">for</span> (String dependentBean : dependentBeans) &#123;</span><br><span class="line">                    <span class="keyword">if</span> (!removeSingletonIfCreatedForTypeCheckOnly(dependentBean)) &#123;</span><br><span class="line">                        actualDependentBeans.add(dependentBean);</span><br><span class="line">                    &#125;</span><br><span class="line">                &#125;</span><br><span class="line">                <span class="keyword">if</span> (!actualDependentBeans.isEmpty()) &#123;</span><br><span class="line">                    <span class="comment">// 抛异常</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 class="keyword">return</span> exposedObject;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
-
-<img src="/2023/11/22/circular-dependencies-in-Spring/Pasted%20image%2020231123013242.png" class="" title="循环引用-三级缓存添加和删除">
-
-<h4 id="无需早期暴露的情况"><a href="#无需早期暴露的情况" class="headerlink" title="无需早期暴露的情况"></a>无需早期暴露的情况</h4><p>在无需早期暴露的情况下，二级缓存没有用到，虽然三级缓存中保存了一个 ObjectFactory，但是也是没有用到的。bean 直接保存到了一级缓存。</p>
-<h4 id="需要早期暴露但无需代理"><a href="#需要早期暴露但无需代理" class="headerlink" title="需要早期暴露但无需代理"></a>需要早期暴露但无需代理</h4><p>在需要早期暴露但无需代理的情况下，尽管获取早期引用后保存在二级缓存中，以供重复使用，但是二级缓存中和原始的 bean 仍然是同一个对象，bean 仍然是直接保存到了一级缓存，再删掉二级缓存。</p>
-<h4 id="需要早期暴露也需要代理"><a href="#需要早期暴露也需要代理" class="headerlink" title="需要早期暴露也需要代理"></a>需要早期暴露也需要代理</h4><p>只有在需要早期暴露和需要代理的情况下，二级缓存中保存的是代理对象，需要从二级缓存中获取再保存到一级缓存中，然后再删除二级缓存。</p>
-<h3 id="必须要三个缓存吗"><a href="#必须要三个缓存吗" class="headerlink" title="必须要三个缓存吗"></a>必须要三个缓存吗</h3><p>网上有很多资料在分析为什么需要三个缓存，才能解决在需要创建代理的情况下发生的循环依赖问题。<br>但是个人觉得有些分析缺乏逻辑，也有点违和感。将当前的解决方案套到只有两个缓存的情况下去分析不太合理，就像你把四轮机动车卸掉一个轮子，说机动车必须要四个轮子才可以，不然不平衡，事实上三个轮子的机动车是存在的。</p>
-<p>在分析两个缓存如何解决在需要创建代理的情况下发生的循环依赖问题时，应该抛开现有的处理逻辑，回归本质问题：既然 circularA 需要创建代理，如果 circularA 依赖的 beans 也依赖了 circular A，在为它们获取 circularA 时立即创建代理即可。<br>一个 map 必须用于存放完成品，另一个 map 用于存放半成品。创建的代理作为升级版的半成品，完全可以覆盖原始的半成品继续存放在第二个 map 中。为了避免重复创建代理，只要能够标识半成品是已经经过代理包装的即可。beanDefinition、bean 自身、创建代理的地方，都有能力实现标识一个 bean 的半成品是否经过包装，最不济使用一个 map 存放标识（但是这也就等同于使用三个 map 了，从这个角度看，三级缓存的缓存意味更加淡了）。<br>甚至可以将半成品 circularA 直接尝试包装成代理，再存放入半成品 map 中。本质上是将创建代理的步骤从初始化 Bean 中分离到初始化 Bean 之前。</p>
-<p>综上，使用两个 map 解决在技术上是没有问题的，很多分析中考虑的问题相当于把 Spring 现有的处理逻辑当成枷锁限制了自己。既然你都在问不这么打地基可不可以，我难道不得考虑挪一挪上面的砖墙吗？当然我不能保证这么设计不会破坏 Spring 现有全部功能的兼容性和扩展性，但是这并不是代理为循环依赖引入的问题。</p>
-]]></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>
-    <content><![CDATA[<h3 id="组织类加载工作：loadClass"><a href="#组织类加载工作：loadClass" class="headerlink" title="组织类加载工作：loadClass"></a>组织类加载工作：loadClass</h3><p>当 <code>Java</code> 程序启动的时候，<code>Java</code> 虚拟机会调用 <code>java.lang.ClassLoader#loadClass(java.lang.String)</code> 加载 <code>main</code> 方法所在的类。</p>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> Class&lt;?&gt; loadClass(String name) <span class="keyword">throws</span> ClassNotFoundException &#123;</span><br><span class="line">    <span class="keyword">return</span> loadClass(name, <span class="literal">false</span>);</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
-
-<p>根据注释可知，此方法加载具有指定二进制名称的类，它由 <code>Java</code> 虚拟机调用来解析类引用，调用它等同于调用 <code>loadClass(name, false)</code>。</p>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">protected</span> Class&lt;?&gt; loadClass(String name, <span class="type">boolean</span> resolve)</span><br><span class="line">    <span class="keyword">throws</span> ClassNotFoundException</span><br><span class="line">&#123;</span><br><span class="line">    <span class="comment">// 以二进制名称获取类加载的锁进行同步</span></span><br><span class="line">    <span class="keyword">synchronized</span> (getClassLoadingLock(name)) &#123;</span><br><span class="line">        <span class="comment">// First, check if the class has already been loaded</span></span><br><span class="line">        <span class="comment">// 首先检查类是否已加载，根据该方法注释可知：</span></span><br><span class="line">        <span class="comment">// 如果当前类加载器已经被 Java 虚拟机记录为具有该二进制名称的类的加载器（initiating loader），Java 虚拟机可以直接返回 Class 对象。</span></span><br><span class="line">        Class&lt;?&gt; c = findLoadedClass(name);</span><br><span class="line">        <span class="keyword">if</span> (c == <span class="literal">null</span>) &#123;</span><br><span class="line">            <span class="type">long</span> <span class="variable">t0</span> <span class="operator">=</span> System.nanoTime();</span><br><span class="line">            <span class="keyword">try</span> &#123;</span><br><span class="line">                <span class="comment">// 如果类还未加载，先委派给父·类加载器进行加载，如果父·类加载器为 null，则使用虚拟机内建的类加载器进行加载</span></span><br><span class="line">                <span class="keyword">if</span> (parent != <span class="literal">null</span>) &#123;</span><br><span class="line">                    <span class="comment">// 递归调用</span></span><br><span class="line">                    c = parent.loadClass(name, <span class="literal">false</span>);</span><br><span class="line">                &#125; <span class="keyword">else</span> &#123;</span><br><span class="line">                    <span class="comment">// 递归调用的终结点</span></span><br><span class="line">                    c = findBootstrapClassOrNull(name);</span><br><span class="line">                &#125;</span><br><span class="line">            &#125; <span class="keyword">catch</span> (ClassNotFoundException e) &#123;</span><br><span class="line">                <span class="comment">// ClassNotFoundException thrown if class not found</span></span><br><span class="line">                <span class="comment">// from the non-null parent class loader</span></span><br><span class="line">                <span class="comment">// 当父·类加载器长尝试加载但是失败，捕获异常但是什么都不做，因为接下来，当前类加载器需要自己也尝试加载。</span></span><br><span class="line">            &#125;</span><br><span class="line"></span><br><span class="line">            <span class="keyword">if</span> (c == <span class="literal">null</span>) &#123;</span><br><span class="line">                <span class="comment">// If still not found, then invoke findClass in order</span></span><br><span class="line">                <span class="comment">// to find the class.</span></span><br><span class="line">                <span class="type">long</span> <span class="variable">t1</span> <span class="operator">=</span> System.nanoTime();</span><br><span class="line">                <span class="comment">// 父·类加载器未找到类，当前类加载器自己找。</span></span><br><span class="line">                c = findClass(name);</span><br><span class="line"></span><br><span class="line">                <span class="comment">// this is the defining class loader; record the stats</span></span><br><span class="line">                sun.misc.PerfCounter.getParentDelegationTime().addTime(t1 - t0);</span><br><span class="line">                sun.misc.PerfCounter.getFindClassTime().addElapsedTimeFrom(t1);</span><br><span class="line">                sun.misc.PerfCounter.getFindClasses().increment();</span><br><span class="line">            &#125;</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="keyword">if</span> (resolve) &#123;</span><br><span class="line">            resolveClass(c);</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="keyword">return</span> c;</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
-
-<p>根据注释可知，<code>java.lang.ClassLoader#loadClass(java.lang.String, boolean)</code> 同样是加载“具有指定二进制名称的类”，此方法的实现按以下顺序搜索类：</p>
-<ol>
-<li>调用 <code>findLoadedClass(String)</code> 以检查该类是否已加载。</li>
-<li>在父·类加载器上调用 <code>loadClass</code> 方法。如果父·类加载器为空，则使用虚拟机内置的类加载器。</li>
-<li>调用 <code>findClass(String)</code> 方法来查找该类。</li>
-</ol>
-<p>如果使用上述步骤找到了该类（找到并定义类），并且解析标志为 <code>true</code>，则此方法将对生成的 <code>Class</code> 对象调用 <code>resolveClass(Class)</code> 方法。鼓励 <code>ClassLoader</code> 的子类重写 <code>findClass(String)</code>，而不是此方法。除非被重写，否则此方法在整个类加载过程中以 <code>getClassLoadingLock</code> 方法的结果进行同步。</p>
-<blockquote>
-<p>注意：<strong>父·类加载器</strong>并非<strong>父类·类加载器</strong>（当前类加载器的父类），而是当前的类加载器的 <code>parent</code> 属性被赋值另外一个类加载器实例，其含义更接近于“可以委派类加载工作的另一个类加载器（一个帮忙干活的上级）”。虽然绝大多数说法中，当一个类加载器的 <code>parent</code> 值为 <code>null</code> 时，它的父·类加载器是引导类加载器（<code>bootstrap class loader</code>），但是当看到 <code>findBootstrapClassOrNull</code> 方法时，我有点困惑，因为我以为会看到语义类似于 <code>loadClassByBootstrapClassLoader</code> 这样的方法名。从注释和代码的语义上看，<code>bootstrap class loader</code> 不像是任何一个类加载器的父·类加载器，但是从类加载的机制设计上说，它是，只是因为它并非由 Java 语言编写而成，不能实例化并赋值给 <code>parent</code> 属性。<code>findBootstrapClassOrNull</code> 方法的语义更接近于：当一个类加载器的父·类加载器为 <code>null</code> 时，将准备加载的目标类先当作启动类（<code>Bootstrap Class</code>）尝试查找，如果找不到就返回 <code>null</code>。</p>
-</blockquote>
-<h4 id="怎么并行地加载类-getClassLoadingLock"><a href="#怎么并行地加载类-getClassLoadingLock" class="headerlink" title="怎么并行地加载类 getClassLoadingLock"></a>怎么并行地加载类 getClassLoadingLock</h4><p>需要加载的类可能很多很多，我们很容易想到如果可以并行地加载类就好了。显然，<code>JDK</code> 的编写者考虑到了这一点。<br>此方法返回类加载操作的锁对象。为了向后兼容，此方法的默认实现的行为如下。如果此 <code>ClassLoader</code> 对象注册为具备并行能力，则该方法返回与指定类名关联的专用对象。 否则，该方法返回此 <code>ClassLoader</code> 对象。<br>简单地说，如果 <code>ClassLoader</code> 对象注册为具备并行能力，那么一个 <code>name</code> 一个锁对象，已创建的锁对象保存在 <code>ConcurrentHashMap</code> 类型的 <code>parallelLockMap</code> 中，这样类加载工作可以并行；否则所有类加载工作共用一个锁对象，就是 <code>ClassLoader</code> 对象本身。<br>这个方案意味着非同名的目标类可以认为在加载时没有冲突？</p>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">protected</span> Object <span class="title function_">getClassLoadingLock</span><span class="params">(String className)</span> &#123;</span><br><span class="line">    <span class="type">Object</span> <span class="variable">lock</span> <span class="operator">=</span> <span class="built_in">this</span>;</span><br><span class="line">    <span class="keyword">if</span> (parallelLockMap != <span class="literal">null</span>) &#123;</span><br><span class="line">        <span class="type">Object</span> <span class="variable">newLock</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">Object</span>();</span><br><span class="line">        lock = parallelLockMap.putIfAbsent(className, newLock);</span><br><span class="line">        <span class="keyword">if</span> (lock == <span class="literal">null</span>) &#123;</span><br><span class="line">            lock = newLock;</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="keyword">return</span> lock;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
-
-<h5 id="什么是-“ClassLoader-对象注册为具有并行能力”呢？"><a href="#什么是-“ClassLoader-对象注册为具有并行能力”呢？" class="headerlink" title="什么是 “ClassLoader 对象注册为具有并行能力”呢？"></a>什么是 “<code>ClassLoader</code> 对象注册为具有并行能力”呢？</h5><p><code>AppClassLoader</code> 中有一段 <code>static</code> 代码。事实上 <code>java.lang.ClassLoader#registerAsParallelCapable</code> 是将 <code>ClassLoader</code> 对象注册为具有并行能力唯一的入口。因此，所有想要注册为具有并行能力的 <code>ClassLoader</code> 都需要调用一次该方法。</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">    ClassLoader.registerAsParallelCapable();</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
-
-<p><code>java.lang.ClassLoader#registerAsParallelCapable</code> 方法有一个注解 <code>@CallerSensitive</code>，这是因为它的代码中调用的 <code>native</code> 方法 <code>sun.reflect.Reflection#getCallerClass()</code> 方法。由注释可知，当且仅当以下所有条件全部满足时才注册成功：</p>
-<ol>
-<li>尚未创建调用者的实例（类加载器尚未实例化）</li>
-<li>调用者的所有超类（<code>Object</code> 类除外）都注册为具有并行能力。</li>
-</ol>
-<h5 id="怎么保证这两个条件成立呢？"><a href="#怎么保证这两个条件成立呢？" class="headerlink" title="怎么保证这两个条件成立呢？"></a>怎么保证这两个条件成立呢？</h5><ol>
-<li>对于第一个条件，可以通过将调用的代码写在 <code>static</code> 代码块中来实现。如果写在构造器方法里，并且通过单例模式保证只实例化一次可以吗？答案是不行的，后续会解释这个“注册”行为在构造器方法中是如何被使用以及为何不能写在构造器方法里。</li>
-<li>对于第二个条件，由于 <code>Java</code> 虚拟机加载类时，总是会先尝试加载其父类，又因为加载类时会先调用 <code>static</code> 代码块，因此父类的 <code>static</code> 代码块总是先于子类的 <code>static</code> 代码块。</li>
-</ol>
-<p>你可以看到 <code>AppClassLoader-&gt;URLClassLoader-&gt;SecureClassLoader-&gt;ClassLoader</code> 均在 <code>static</code> 代码块实现注册，以保证满足以上两个条件。</p>
-<h5 id="注册工作做了什么？"><a href="#注册工作做了什么？" class="headerlink" title="注册工作做了什么？"></a>注册工作做了什么？</h5><p>简单地说就是保存了类加载器所属 <code>Class</code> 的 <code>Set</code>。</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">protected</span> <span class="keyword">static</span> <span class="type">boolean</span> <span class="title function_">registerAsParallelCapable</span><span class="params">()</span> &#123;</span><br><span class="line">    <span class="comment">// 获得此方法的调用者的 Class 实例，asSubClass 可以将 Class&lt;?&gt; 类型的 Class 转换为代表指定类的子类的 Class&lt;? extends U&gt; 类型的 Class。</span></span><br><span class="line">    Class&lt;? <span class="keyword">extends</span> <span class="title class_">ClassLoader</span>&gt; callerClass =</span><br><span class="line">        Reflection.getCallerClass().asSubclass(ClassLoader.class);</span><br><span class="line">    <span class="comment">// 注册调用者的 Class 为具有并行能力</span></span><br><span class="line">    <span class="keyword">return</span> ParallelLoaders.register(callerClass);</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
-
-<p>方法 <code>java.lang.ClassLoader.ParallelLoaders#register</code>。<code>ParallelLoaders</code> 封装了一组具有并行能力的加载器类型。就是持有 <code>ClassLoader</code> 的 <code>Class</code> 实例的集合，并保证添加时加同步锁。</p>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="comment">// private 修饰，只有其外部类 ClassLoader 才可以使用</span></span><br><span class="line"><span class="comment">// static 修饰，内部类如果需要定义 static 方法或者 static 变量，必须用 static 修饰</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_">ParallelLoaders</span> &#123;</span><br><span class="line">    <span class="comment">// private 修饰构造器方法，不希望这个类被实例化，只想要使用它的静态变量和方法。</span></span><br><span class="line">    <span class="keyword">private</span> <span class="title function_">ParallelLoaders</span><span class="params">()</span> &#123;&#125;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// the set of parallel capable loader types</span></span><br><span class="line">    <span class="comment">// 使用 loaderTypes 时通过 synchronized 加同步锁</span></span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">static</span> <span class="keyword">final</span> Set&lt;Class&lt;? <span class="keyword">extends</span> <span class="title class_">ClassLoader</span>&gt;&gt; loaderTypes =</span><br><span class="line">        Collections.newSetFromMap(</span><br><span class="line">            <span class="comment">// todo: 为什么使用弱引用来实现？为了卸载类时的垃圾回收？</span></span><br><span class="line">            <span class="keyword">new</span> <span class="title class_">WeakHashMap</span>&lt;Class&lt;? <span class="keyword">extends</span> <span class="title class_">ClassLoader</span>&gt;, Boolean&gt;());</span><br><span class="line">    <span class="keyword">static</span> &#123;</span><br><span class="line">        <span class="comment">// 将 ClassLoader 本身注册为具有并行能力</span></span><br><span class="line">        <span class="keyword">synchronized</span> (loaderTypes) &#123; loaderTypes.add(ClassLoader.class); &#125;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="comment">/**</span></span><br><span class="line"><span class="comment">     * Registers the given class loader type as parallel capabale.</span></span><br><span class="line"><span class="comment">     * Returns &#123;<span class="doctag">@code</span> true&#125; is successfully registered; &#123;<span class="doctag">@code</span> false&#125; if</span></span><br><span class="line"><span class="comment">     * loader&#x27;s super class is not registered.</span></span><br><span class="line"><span class="comment">     */</span></span><br><span class="line">    <span class="keyword">static</span> <span class="type">boolean</span> <span class="title function_">register</span><span class="params">(Class&lt;? extends ClassLoader&gt; c)</span> &#123;</span><br><span class="line">        <span class="keyword">synchronized</span> (loaderTypes) &#123;</span><br><span class="line">            <span class="keyword">if</span> (loaderTypes.contains(c.getSuperclass())) &#123;</span><br><span class="line">                <span class="comment">// register the class loader as parallel capable</span></span><br><span class="line">                <span class="comment">// if and only if all of its super classes are.</span></span><br><span class="line">                <span class="comment">// Note: given current classloading sequence, if</span></span><br><span class="line">                <span class="comment">// the immediate super class is parallel capable,</span></span><br><span class="line">                <span class="comment">// all the super classes higher up must be too.</span></span><br><span class="line">                <span class="comment">// 当且仅当其所有超类都具有并行能力时，才将类加载器注册为具有并行能力。</span></span><br><span class="line">                <span class="comment">// 注意：给定当前的类加载顺序（加载类时，Java 虚拟机总是先尝试加载其父类），如果直接超类具有并行能力，则所有更高的超类也必然具有并行能力。</span></span><br><span class="line">                loaderTypes.add(c);</span><br><span class="line">                <span class="keyword">return</span> <span class="literal">true</span>;</span><br><span class="line">            &#125; <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">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="comment">/**</span></span><br><span class="line"><span class="comment">     * Returns &#123;<span class="doctag">@code</span> true&#125; if the given class loader type is</span></span><br><span class="line"><span class="comment">     * registered as parallel capable.</span></span><br><span class="line"><span class="comment">     */</span></span><br><span class="line">    <span class="keyword">static</span> <span class="type">boolean</span> <span class="title function_">isRegistered</span><span class="params">(Class&lt;? extends ClassLoader&gt; c)</span> &#123;</span><br><span class="line">        <span class="keyword">synchronized</span> (loaderTypes) &#123;</span><br><span class="line">            <span class="keyword">return</span> loaderTypes.contains(c);</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="“注册”怎么和锁产生联系？"><a href="#“注册”怎么和锁产生联系？" class="headerlink" title="“注册”怎么和锁产生联系？"></a>“注册”怎么和锁产生联系？</h5><p>但是以上的注册过程只是起到一个“标记”作用，没有涉及和锁相关的代码，那么这个“标记”是怎么和真正的锁产生联系呢？<code>ClassLoader</code> 提供了三个构造器方法：</p>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">private</span> <span class="title function_">ClassLoader</span><span class="params">(Void unused, ClassLoader parent)</span> &#123;</span><br><span class="line">    <span class="comment">// 由 private 修饰，不允许子类重写</span></span><br><span class="line">    <span class="built_in">this</span>.parent = parent;</span><br><span class="line">    <span class="keyword">if</span> (ParallelLoaders.isRegistered(<span class="built_in">this</span>.getClass())) &#123;</span><br><span class="line">        <span class="comment">// 如果类加载器已经注册为具有并行能力，则做一些赋值操作</span></span><br><span class="line">        parallelLockMap = <span class="keyword">new</span> <span class="title class_">ConcurrentHashMap</span>&lt;&gt;();</span><br><span class="line">        <span class="comment">// 保存 package-&gt;certs 的 map 映射，相关的工作也可以并行进行</span></span><br><span class="line">        package2certs = <span class="keyword">new</span> <span class="title class_">ConcurrentHashMap</span>&lt;&gt;();</span><br><span class="line">        assertionLock = <span class="keyword">new</span> <span class="title class_">Object</span>();</span><br><span class="line">    &#125; <span class="keyword">else</span> &#123;</span><br><span class="line">        <span class="comment">// no finer-grained lock; lock on the classloader instance</span></span><br><span class="line">        parallelLockMap = <span class="literal">null</span>;</span><br><span class="line">        package2certs = <span class="keyword">new</span> <span class="title class_">Hashtable</span>&lt;&gt;();</span><br><span class="line">        assertionLock = <span class="built_in">this</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">// 由 protect 修饰，允许子类重写，传递了父·类加载器。</span></span><br><span class="line"><span class="keyword">protected</span> <span class="title function_">ClassLoader</span><span class="params">(ClassLoader parent)</span> &#123;</span><br><span class="line">    <span class="built_in">this</span>(checkCreateClassLoader(), parent);</span><br><span class="line">&#125;</span><br><span class="line"></span><br><span class="line"><span class="comment">// 由 protect 修饰，允许子类重写，父·类加载器使用 getSystemClassLoader 方法返回的系统类加载器。</span></span><br><span class="line"><span class="keyword">protected</span> <span class="title function_">ClassLoader</span><span class="params">()</span> &#123;</span><br><span class="line">    <span class="built_in">this</span>(checkCreateClassLoader(), getSystemClassLoader());</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
-
-<p><code>ClassLoader</code> 的构造器方法最终都调用 <code>private</code> 修饰的 <code>java.lang.ClassLoader#ClassLoader(java.lang.Void, java.lang.ClassLoader)</code>，又因为父类的构造器方法总是先于子类的构造器方法被执行，这样一来，所有继承 <code>ClassLoader</code> 的类加载器在创建的时候都会根据在创建实例之前是否注册为具有并行能力而做不同的操作。</p>
-<h5 id="为什么注册的代码不能写在构造器方法里？"><a href="#为什么注册的代码不能写在构造器方法里？" class="headerlink" title="为什么注册的代码不能写在构造器方法里？"></a>为什么注册的代码不能写在构造器方法里？</h5><p>使用“注册”的代码也解释了 <code>java.lang.ClassLoader#registerAsParallelCapable</code> 为了满足调用成功的第一个条件为什么不能写在构造器方法中，因为使用这个机制的代码先于你在子类构造器方法里编写的代码被执行。<br>同时，不论是 <code>loadLoader</code> 还是 <code>getClassLoadingLock</code> 都是由 <code>protect</code> 修饰，允许子类重写，来自定义并行加载类的能力。</p>
-<blockquote>
-<p>todo: 讨论自定义类加载器的时候，印象里似乎对并行加载类的提及比较少，之后留意一下。</p>
-</blockquote>
-<h4 id="检查目标类是否已加载"><a href="#检查目标类是否已加载" class="headerlink" title="检查目标类是否已加载"></a>检查目标类是否已加载</h4><p>加载类之前显然需要检查目标类是否已加载，这项工作最终是交给 <code>native</code> 方法，在虚拟机中执行，就像在黑盒中一样。<br>todo: 不同类加载器同一个类名会如何判定？</p>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">protected</span> <span class="keyword">final</span> Class&lt;?&gt; findLoadedClass(String name) &#123;</span><br><span class="line">    <span class="keyword">if</span> (!checkName(name))</span><br><span class="line">        <span class="keyword">return</span> <span class="literal">null</span>;</span><br><span class="line">    <span class="keyword">return</span> findLoadedClass0(name);</span><br><span class="line">&#125;</span><br><span class="line"></span><br><span class="line"><span class="keyword">private</span> <span class="keyword">native</span> <span class="keyword">final</span> Class&lt;?&gt; findLoadedClass0(String name);</span><br></pre></td></tr></table></figure>
-
-<h4 id="保证核心类库的安全性：双亲委派模型"><a href="#保证核心类库的安全性：双亲委派模型" class="headerlink" title="保证核心类库的安全性：双亲委派模型"></a>保证核心类库的安全性：双亲委派模型</h4><p>正如在代码和注释中所看到的，正常情况下，类的加载工作先委派给自己的父·类加载器，即 <code>parent</code> 属性的值——另一个类加载器实例。一层一层向上委派直到 <code>parent</code> 为 <code>null</code>，代表类加载工作会尝试先委派给虚拟机内建的 <code>bootstrap class loader</code> 处理，然后由 <code>bootstrap class loader</code> 首先尝试加载。如果被委派方加载失败，委派方会自己再尝试加载。<br>正常加载类的是应用类加载器 <code>AppClassLoader</code>，它的 <code>parent</code> 为 <code>ExtClassLoader</code>，<code>ExtClassLoader</code> 的 <code>parent</code> 为 <code>null</code>。</p>
-<blockquote>
-<p>在网上也能看到有人提到以前大家称之为“父·类加载器委派机制”，“双亲”一词易引人误解。</p>
-</blockquote>
-<h5 id="为什么要用这套奇怪的机制"><a href="#为什么要用这套奇怪的机制" class="headerlink" title="为什么要用这套奇怪的机制"></a>为什么要用这套奇怪的机制</h5><p>这样设计很明显的一个目的就是保证核心类库的类加载安全性。比如 <code>Object</code> 类，设计者不希望编写代码的人重新写一个 <code>Object</code> 类并加载到 <code>Java</code> 虚拟机中，但是加载类的本质就是读取字节数据传递给 <code>Java</code> 虚拟机创建一个 <code>Class</code> 实例，使用这套机制的目的之一就是为了让核心类库先加载，同时先加载的类不会再次被加载。</p>
-<p>通常流程如下：</p>
-<ol>
-<li><code>AppClassLoader</code> 调用 <code>loadClass</code> 方法，先委派给 <code>ExtClassLoader</code>。</li>
-<li><code>ExtClassLoader</code> 调用 <code>loadClass</code> 方法，先委派给 <code>bootstrap class loader</code>。</li>
-<li><code>bootstrap class loader</code> 在其设置的类路径中无法找到 <code>BananaTest</code> 类，抛出 <code>ClassNotFoundException</code> 异常。</li>
-<li><code>ExtClassLoader</code> 捕获异常，然后自己调用 <code>findClass</code> 方法尝试进行加载。</li>
-<li><code>ExtClassLoader</code> 在其设置的类路径中无法找到 <code>BananaTest</code> 类，抛出 <code>ClassNotFoundException</code> 异常。</li>
-<li><code>AppClassLoader</code> 捕获异常，然后自己调用 <code>findClass</code> 方法尝试进行加载。</li>
-</ol>
-<p>注释中提到鼓励重写 <code>findClass</code> 方法而不是 <code>loadClass</code>，因为正是该方法实现了所谓的“双亲委派模型”，<code>java.lang.ClassLoader#findClass</code> 实现了如何查找加载类。如果不是专门为了破坏这个类加载模型，应该选择重写 <code>findClass</code>；其次是因为该方法中涉及并行加载类的机制。</p>
-<h3 id="查找类资源：findClass"><a href="#查找类资源：findClass" class="headerlink" title="查找类资源：findClass"></a>查找类资源：findClass</h3><p>默认情况下，类加载器在自己尝试进行加载时，会调用 <code>java.lang.ClassLoader#findClass</code> 方法，该方法由子类重写。<code>AppClassLoader</code> 和 <code>ExtClassLoader</code> 都是继承 <code>URLClassLoader</code>，而 <code>URLClassLoader</code> 重写了 <code>findClass</code> 方法。根据注释可知，该方法会从 <code>URL</code> 搜索路径查找并加载具有指定名称的类。任何引用 <code>Jar</code> 文件的 <code>URL</code> 都会根据需要加载并打开，直到找到该类。</p>
-<p>过程如下：</p>
-<ol>
-<li>将 <code>name</code> 转换为 <code>path</code>，比如 <code>com.example.BananaTest</code> 转换为 <code>com/example/BananaTest.class</code>。</li>
-<li>使用 <code>URL</code> 搜索路径 <code>URLClassPath</code> 和 <code>path</code> 中获取 <code>Resource</code>，本质上就是轮流将可能存放的目录列表拼接上文件路径进行查找。</li>
-<li>调用 <code>URLClassLoader</code> 的私有方法 <code>defineClass</code>，该方法调用父类 <code>SecureClassLoader</code> 的 <code>defineClass</code> 方法。</li>
-</ol>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">protected</span> Class&lt;?&gt; findClass(<span class="keyword">final</span> String name)</span><br><span class="line">    <span class="keyword">throws</span> ClassNotFoundException</span><br><span class="line">&#123;</span><br><span class="line">    <span class="keyword">final</span> Class&lt;?&gt; result;</span><br><span class="line">    <span class="keyword">try</span> &#123;</span><br><span class="line">        <span class="comment">// todo:</span></span><br><span class="line">        result = AccessController.doPrivileged(</span><br><span class="line">            <span class="keyword">new</span> <span class="title class_">PrivilegedExceptionAction</span>&lt;Class&lt;?&gt;&gt;() &#123;</span><br><span class="line">                <span class="keyword">public</span> Class&lt;?&gt; run() <span class="keyword">throws</span> ClassNotFoundException &#123;</span><br><span class="line">                    <span class="comment">// 将 name 转换为 path</span></span><br><span class="line">                    <span class="type">String</span> <span class="variable">path</span> <span class="operator">=</span> name.replace(<span class="string">&#x27;.&#x27;</span>, <span class="string">&#x27;/&#x27;</span>).concat(<span class="string">&quot;.class&quot;</span>);</span><br><span class="line">                    <span class="comment">// 从 URLClassPath 中查找 Resource</span></span><br><span class="line">                    <span class="type">Resource</span> <span class="variable">res</span> <span class="operator">=</span> ucp.getResource(path, <span class="literal">false</span>);</span><br><span class="line">                    <span class="keyword">if</span> (res != <span class="literal">null</span>) &#123;</span><br><span class="line">                        <span class="keyword">try</span> &#123;</span><br><span class="line">                            <span class="keyword">return</span> defineClass(name, res);</span><br><span class="line">                        &#125; <span class="keyword">catch</span> (IOException e) &#123;</span><br><span class="line">                            <span class="keyword">throw</span> <span class="keyword">new</span> <span class="title class_">ClassNotFoundException</span>(name, e);</span><br><span class="line">                        &#125; <span class="keyword">catch</span> (ClassFormatError e2) &#123;</span><br><span class="line">                            <span class="keyword">if</span> (res.getDataError() != <span class="literal">null</span>) &#123;</span><br><span class="line">                                e2.addSuppressed(res.getDataError());</span><br><span class="line">                            &#125;</span><br><span class="line">                            <span class="keyword">throw</span> e2;</span><br><span class="line">                        &#125;</span><br><span class="line">                    &#125; <span class="keyword">else</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">                &#125;</span><br><span class="line">            &#125;, acc);</span><br><span class="line">    &#125; <span class="keyword">catch</span> (java.security.PrivilegedActionException pae) &#123;</span><br><span class="line">        <span class="keyword">throw</span> (ClassNotFoundException) pae.getException();</span><br><span class="line">    &#125;</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">throw</span> <span class="keyword">new</span> <span class="title class_">ClassNotFoundException</span>(name);</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="keyword">return</span> result;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
-
-<h4 id="查找类的目录列表：URLClassPath"><a href="#查找类的目录列表：URLClassPath" class="headerlink" title="查找类的目录列表：URLClassPath"></a>查找类的目录列表：URLClassPath</h4><p><code>URLClassLoader</code> 拥有一个 <code>URLClassPath</code> 类型的属性 <code>ucp</code>。由注释可知，<code>URLClassPath</code> 类用于维护一个 <code>URL</code> 的搜索路径，以便从 <code>Jar</code> 文件和目录中加载类和资源。<br><code>URLClassPath</code> 的核心构造器方法：</p>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="title function_">URLClassPath</span><span class="params">(URL[] urls,</span></span><br><span class="line"><span class="params">                    URLStreamHandlerFactory factory,</span></span><br><span class="line"><span class="params">                    AccessControlContext acc)</span> &#123;</span><br><span class="line">    <span class="comment">// 将 urls 保存到 ArrayList 类型的属性 path 中，根据注释，path 的含义为 URL 的原始搜索路径。</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; urls.length; i++) &#123;</span><br><span class="line">        path.add(urls[i]);</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="comment">// 将 urls 保存到 Stack 类型的属性 urls 中，根据注释，urls 的含义为未打开的 URL 列表。</span></span><br><span class="line">    push(urls);</span><br><span class="line">    <span class="keyword">if</span> (factory != <span class="literal">null</span>) &#123;</span><br><span class="line">        <span class="comment">// 如果 factory 不为 null，使用它创建一个 URLStreamHandler 实例处理 Jar 文件。</span></span><br><span class="line">        jarHandler = factory.createURLStreamHandler(<span class="string">&quot;jar&quot;</span>);</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="keyword">if</span> (DISABLE_ACC_CHECKING)</span><br><span class="line">        <span class="built_in">this</span>.acc = <span class="literal">null</span>;</span><br><span class="line">    <span class="keyword">else</span></span><br><span class="line">        <span class="built_in">this</span>.acc = acc;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
-
-<h5 id="URLClassPath-getResource"><a href="#URLClassPath-getResource" class="headerlink" title="URLClassPath#getResource"></a>URLClassPath#getResource</h5><p><code>URLClassLoader</code> 调用 <code>sun.misc.URLClassPath#getResource(java.lang.String, boolean)</code> 方法获取指定名称对应的资源。根据注释，该方法会查找 <code>URL</code> 搜索路径上的第一个资源，如果找不到资源，则返回 <code>null</code>。<br>显然，这里的 <code>Loader</code> 不是我们前面提到的类加载器。<code>Loader</code> 是 <code>URLClassPath</code> 的内部类，用于表示根据一个基本 <code>URL</code> 创建的资源和类的加载器。也就是说一个基本 <code>URL</code> 对应一个 <code>Loader</code>。</p>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> Resource <span class="title function_">getResource</span><span class="params">(String name, <span class="type">boolean</span> check)</span> &#123;</span><br><span class="line">    <span class="keyword">if</span> (DEBUG) &#123;</span><br><span class="line">        System.err.println(<span class="string">&quot;URLClassPath.getResource(\&quot;&quot;</span> + name + <span class="string">&quot;\&quot;)&quot;</span>);</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    Loader loader;</span><br><span class="line">    <span class="comment">// 获取缓存（默认没有用）</span></span><br><span class="line">    <span class="type">int</span>[] cache = getLookupCache(name);</span><br><span class="line">    <span class="comment">// 不断获取下一个 Loader 来获取 Resource，直到获取到或者没有下一个 Loader</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>; (loader = getNextLoader(cache, i)) != <span class="literal">null</span>; i++) &#123;</span><br><span class="line">        <span class="type">Resource</span> <span class="variable">res</span> <span class="operator">=</span> loader.getResource(name, check);</span><br><span class="line">        <span class="keyword">if</span> (res != <span class="literal">null</span>) &#123;</span><br><span class="line">            <span class="keyword">return</span> res;</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>
-
-<h5 id="URLClassPath-getNextLoader"><a href="#URLClassPath-getNextLoader" class="headerlink" title="URLClassPath#getNextLoader"></a>URLClassPath#getNextLoader</h5><p>获取下一个 <code>Loader</code>，其实根据 <code>index</code> 从一个存放已创建 <code>Loader</code> 的 <code>ArrayList</code> 中获取。</p>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">private</span> <span class="keyword">synchronized</span> Loader <span class="title function_">getNextLoader</span><span class="params">(<span class="type">int</span>[] cache, <span class="type">int</span> index)</span> &#123;</span><br><span class="line">    <span class="keyword">if</span> (closed) &#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">if</span> (cache != <span class="literal">null</span>) &#123;</span><br><span class="line">        <span class="keyword">if</span> (index &lt; cache.length) &#123;</span><br><span class="line">            <span class="type">Loader</span> <span class="variable">loader</span> <span class="operator">=</span> loaders.get(cache[index]);</span><br><span class="line">            <span class="keyword">if</span> (DEBUG_LOOKUP_CACHE) &#123;</span><br><span class="line">                System.out.println(<span class="string">&quot;HASCACHE: Loading from : &quot;</span> + cache[index]</span><br><span class="line">                                    + <span class="string">&quot; = &quot;</span> + loader.getBaseURL());</span><br><span class="line">            &#125;</span><br><span class="line">            <span class="keyword">return</span> loader;</span><br><span class="line">        &#125; <span class="keyword">else</span> &#123;</span><br><span class="line">            <span class="keyword">return</span> <span class="literal">null</span>; <span class="comment">// finished iterating over cache[]</span></span><br><span class="line">        &#125;</span><br><span class="line">    &#125; <span class="keyword">else</span> &#123;</span><br><span class="line">        <span class="comment">// 获取 Loader</span></span><br><span class="line">        <span class="keyword">return</span> getLoader(index);</span><br><span class="line">    &#125;</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> Object <span class="title function_">resolveReference</span><span class="params">(Object argName, RuntimeBeanReference ref)</span> &#123;</span><br><span class="line">    <span class="comment">// ...</span></span><br><span class="line">    <span class="comment">// 解析引用将调用 getBean</span></span><br><span class="line">    <span class="type">Object</span> <span class="variable">bean</span> <span class="operator">=</span> <span class="built_in">this</span>.beanFactory.getBean(refName);</span><br><span class="line">    <span class="built_in">this</span>.beanFactory.registerDependentBean(refName, <span class="built_in">this</span>.beanName);</span><br><span class="line">    <span class="keyword">return</span> bean;</span><br><span class="line">    <span class="comment">// ...</span></span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
 
-<h5 id="URLClassPath-getLoader-int"><a href="#URLClassPath-getLoader-int" class="headerlink" title="URLClassPath#getLoader(int)"></a>URLClassPath#getLoader(int)</h5><ol>
-<li>用 <code>index</code> 到存放已创建 <code>Loader</code> 的列表中去获取（调用方传入的 <code>index</code> 从 <code>0</code> 开始不断递增直到超过范围）。</li>
-<li>如果 <code>index</code> 超过范围，说明已有的 <code>Loader</code> 都找不到目标 <code>Resource</code>，需要到未打开的 <code>URL</code> 中查找。</li>
-<li>从未打开的 <code>URL</code> 中取出（<code>pop</code>）一个来创建 <code>Loader</code>，如果 <code>urls</code> 已经为空，则返回 <code>null</code>。</li>
+<h3 id="获取-circularB"><a href="#获取-circularB" class="headerlink" title="获取 circularB"></a>获取 circularB</h3><p>AbstractBeanFactory#doGetBean(circularB)，获取 circularB 将经过和 circularA 一样的流程，进入 populateBean(circularB) 对其进行依赖注入，进而再次去获取 circularA。</p>
+<h2 id="第二次获取-circularA"><a href="#第二次获取-circularA" class="headerlink" title="第二次获取 circularA"></a>第二次获取 circularA</h2><h3 id="doGetBean-circularA-1"><a href="#doGetBean-circularA-1" class="headerlink" title="doGetBean(circularA)"></a>doGetBean(circularA)</h3><ol>
+<li>第二次获取 circularA 时，仍然先尝试从缓存中获取</li>
+<li>这次将从缓存中得到先前创建的 circularA。</li>
 </ol>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">private</span> <span class="keyword">synchronized</span> Loader <span class="title function_">getLoader</span><span class="params">(<span class="type">int</span> index)</span> &#123;</span><br><span class="line">    <span class="keyword">if</span> (closed) &#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="comment">// Expand URL search path until the request can be satisfied</span></span><br><span class="line">    <span class="comment">// or the URL stack is empty.</span></span><br><span class="line">    <span class="keyword">while</span> (loaders.size() &lt; index + <span class="number">1</span>) &#123;</span><br><span class="line">        <span class="comment">// Pop the next URL from the URL stack</span></span><br><span class="line">        <span class="comment">// 如果 index 超过数组范围，需要从未打开的 URL 中取出一个，创建 Loader 并返回</span></span><br><span class="line">        URL url;</span><br><span class="line">        <span class="keyword">synchronized</span> (urls) &#123;</span><br><span class="line">            <span class="keyword">if</span> (urls.empty()) &#123;</span><br><span class="line">                <span class="keyword">return</span> <span class="literal">null</span>;</span><br><span class="line">            &#125; <span class="keyword">else</span> &#123;</span><br><span class="line">                url = urls.pop();</span><br><span class="line">            &#125;</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="comment">// Skip this URL if it already has a Loader. (Loader</span></span><br><span class="line">        <span class="comment">// may be null in the case where URL has not been opened</span></span><br><span class="line">        <span class="comment">// but is referenced by a JAR index.)</span></span><br><span class="line">        <span class="type">String</span> <span class="variable">urlNoFragString</span> <span class="operator">=</span> URLUtil.urlNoFragString(url);</span><br><span class="line">        <span class="keyword">if</span> (lmap.containsKey(urlNoFragString)) &#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">// Otherwise, create a new Loader for the URL.</span></span><br><span class="line">        Loader loader;</span><br><span class="line">        <span class="keyword">try</span> &#123;</span><br><span class="line">            <span class="comment">// 根据 URL 创建 Loader</span></span><br><span class="line">            loader = getLoader(url);</span><br><span class="line">            <span class="comment">// If the loader defines a local class path then add the</span></span><br><span class="line">            <span class="comment">// URLs to the list of URLs to be opened.</span></span><br><span class="line">            URL[] urls = loader.getClassPath();</span><br><span class="line">            <span class="keyword">if</span> (urls != <span class="literal">null</span>) &#123;</span><br><span class="line">                push(urls);</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">            <span class="comment">// Silently ignore for now...</span></span><br><span class="line">            <span class="keyword">continue</span>;</span><br><span class="line">        &#125; <span class="keyword">catch</span> (SecurityException se) &#123;</span><br><span class="line">            <span class="comment">// Always silently ignore. The context, if there is one, that</span></span><br><span class="line">            <span class="comment">// this URLClassPath was given during construction will never</span></span><br><span class="line">            <span class="comment">// have permission to access the URL.</span></span><br><span class="line">            <span class="keyword">if</span> (DEBUG) &#123;</span><br><span class="line">                System.err.println(<span class="string">&quot;Failed to access &quot;</span> + url + <span class="string">&quot;, &quot;</span> + se );</span><br><span class="line">            &#125;</span><br><span class="line">            <span class="keyword">continue</span>;</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="comment">// Finally, add the Loader to the search path.</span></span><br><span class="line">        validateLookupCache(loaders.size(), urlNoFragString);</span><br><span class="line">        loaders.add(loader);</span><br><span class="line">        lmap.put(urlNoFragString, loader);</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="keyword">if</span> (DEBUG_LOOKUP_CACHE) &#123;</span><br><span class="line">        System.out.println(<span class="string">&quot;NOCACHE: Loading from : &quot;</span> + index );</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="keyword">return</span> loaders.get(index);</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">protected</span> &lt;T&gt; T <span class="title function_">doGetBean</span><span class="params">(</span></span><br><span class="line"><span class="params">        <span class="keyword">final</span> String name, <span class="keyword">final</span> Class&lt;T&gt; requiredType, <span class="keyword">final</span> Object[] args, <span class="type">boolean</span> typeCheckOnly)</span></span><br><span class="line">        <span class="keyword">throws</span> BeansException &#123;</span><br><span class="line">    <span class="comment">// ...</span></span><br><span class="line">    <span class="comment">// 尝试从缓存中获取 circularA，结果为 null</span></span><br><span class="line">    <span class="type">Object</span> <span class="variable">sharedInstance</span> <span class="operator">=</span> getSingleton(beanName);</span><br><span class="line">    <span class="comment">// ...</span></span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<p>在第一次获取 circularA 时，我们跳过了查看 getSingleton(String) 的代码。其实代码的逻辑并不复杂，但是要理解为什么这么做，却需要回过头来反复品味和思考。</p>
+<h3 id="从缓存中获取-circularA"><a href="#从缓存中获取-circularA" class="headerlink" title="从缓存中获取 circularA"></a>从缓存中获取 circularA</h3><figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">protected</span> Object <span class="title function_">getSingleton</span><span class="params">(String beanName, <span class="type">boolean</span> allowEarlyReference)</span> &#123;</span><br><span class="line">    <span class="type">Object</span> <span class="variable">singletonObject</span> <span class="operator">=</span> <span class="built_in">this</span>.singletonObjects.get(beanName);</span><br><span class="line">    <span class="comment">// 如果 singletonObjects 中不存在，且 bean 正在创建过程中</span></span><br><span class="line">    <span class="keyword">if</span> (singletonObject == <span class="literal">null</span> &amp;&amp; isSingletonCurrentlyInCreation(beanName)) &#123;</span><br><span class="line">        <span class="keyword">synchronized</span> (<span class="built_in">this</span>.singletonObjects) &#123;</span><br><span class="line">            <span class="comment">// 从 earlySingletonObjects 获取</span></span><br><span class="line">            singletonObject = <span class="built_in">this</span>.earlySingletonObjects.get(beanName);</span><br><span class="line">            <span class="keyword">if</span> (singletonObject == <span class="literal">null</span> &amp;&amp; allowEarlyReference) &#123;</span><br><span class="line">                <span class="comment">// 如果 earlySingletonObjects 中不存在，且允许早期引用，就从 singletonFactories 中获取</span></span><br><span class="line">                ObjectFactory&lt;?&gt; singletonFactory = <span class="built_in">this</span>.singletonFactories.get(beanName);</span><br><span class="line">                <span class="keyword">if</span> (singletonFactory != <span class="literal">null</span>) &#123;</span><br><span class="line">                    singletonObject = singletonFactory.getObject();</span><br><span class="line">                    <span class="built_in">this</span>.earlySingletonObjects.put(beanName, singletonObject);</span><br><span class="line">                    <span class="built_in">this</span>.singletonFactories.remove(beanName);</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="keyword">return</span> (singletonObject != NULL_OBJECT ? singletonObject : <span class="literal">null</span>);</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
 
-<h5 id="URLClassPath-getLoader-java-net-URL"><a href="#URLClassPath-getLoader-java-net-URL" class="headerlink" title="URLClassPath#getLoader(java.net.URL)"></a>URLClassPath#getLoader(java.net.URL)</h5><p>根据指定的 <code>URL</code> 创建 <code>Loader</code>，不同类型的 <code>URL</code> 会返回不同具体实现的 <code>Loader</code>。</p>
 <ol>
-<li>如果 <code>URL</code> 不是以 <code>/</code> 结尾，认为是 <code>Jar</code> 文件，则返回 <code>JarLoader</code> 类型，比如 <code>file:/C:/Users/xxx/.jdks/corretto-1.8.0_342/jre/lib/rt.jar</code>。</li>
-<li>如果 <code>URL</code> 以 <code>/</code> 结尾，且协议为 <code>file</code>，则返回 <code>FileLoader</code> 类型，比如 <code>file:/C:/Users/xxx/IdeaProjects/java-test/target/classes/</code>。</li>
-<li>如果 <code>URL</code> 以 <code>/</code> 结尾，且协议不会 <code>file</code>，则返回 <code>Loader</code> 类型。</li>
+<li>从 singletonObjects（一级缓存） 获取 circularA，不存在</li>
+<li>circularA 属于正在创建中，从 earlySingletonObjects（二级缓存） 获取，仍然不存在</li>
+<li>allowEarlyReference 为真，从 singletonFactories（三级缓存） 获取（circularA 实例化后被包装为 ObjectFactory 保存在这里）</li>
+<li>调用 getObject 获得对象</li>
 </ol>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">private</span> Loader <span class="title function_">getLoader</span><span class="params">(<span class="keyword">final</span> URL url)</span> <span class="keyword">throws</span> IOException &#123;</span><br><span class="line">    <span class="keyword">try</span> &#123;</span><br><span class="line">        <span class="keyword">return</span> java.security.AccessController.doPrivileged(</span><br><span class="line">            <span class="keyword">new</span> <span class="title class_">java</span>.security.PrivilegedExceptionAction&lt;Loader&gt;() &#123;</span><br><span class="line">            <span class="keyword">public</span> Loader <span class="title function_">run</span><span class="params">()</span> <span class="keyword">throws</span> IOException &#123;</span><br><span class="line">                <span class="type">String</span> <span class="variable">file</span> <span class="operator">=</span> url.getFile();</span><br><span class="line">                <span class="keyword">if</span> (file != <span class="literal">null</span> &amp;&amp; file.endsWith(<span class="string">&quot;/&quot;</span>)) &#123;</span><br><span class="line">                    <span class="keyword">if</span> (<span class="string">&quot;file&quot;</span>.equals(url.getProtocol())) &#123;</span><br><span class="line">                        <span class="keyword">return</span> <span class="keyword">new</span> <span class="title class_">FileLoader</span>(url);</span><br><span class="line">                    &#125; <span class="keyword">else</span> &#123;</span><br><span class="line">                        <span class="keyword">return</span> <span class="keyword">new</span> <span class="title class_">Loader</span>(url);</span><br><span class="line">                    &#125;</span><br><span class="line">                &#125; <span class="keyword">else</span> &#123;</span><br><span class="line">                    <span class="keyword">return</span> <span class="keyword">new</span> <span class="title class_">JarLoader</span>(url, jarHandler, lmap, acc);</span><br><span class="line">                &#125;</span><br><span class="line">            &#125;</span><br><span class="line">        &#125;, acc);</span><br><span class="line">    &#125; <span class="keyword">catch</span> (java.security.PrivilegedActionException pae) &#123;</span><br><span class="line">        <span class="keyword">throw</span> (IOException)pae.getException();</span><br><span class="line">    &#125;</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">addSingletonFactory(beanName, <span class="keyword">new</span> <span class="title class_">ObjectFactory</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_">getObject</span><span class="params">()</span> <span class="keyword">throws</span> BeansException &#123;</span><br><span class="line">        <span class="keyword">return</span> getEarlyBeanReference(beanName, mbd, bean);</span><br><span class="line">    &#125;</span><br><span class="line">&#125;);</span><br></pre></td></tr></table></figure>
 
-<h4 id="URLClassPath-FileLoader-getResource"><a href="#URLClassPath-FileLoader-getResource" class="headerlink" title="URLClassPath.FileLoader#getResource"></a>URLClassPath.FileLoader#getResource</h4><p>以 <code>FileLoader</code> 的 <code>getResource</code> 为例，如果文件找到了，就会将文件包装成一个 <code>FileInputStream</code>，再将 <code>FileInputStream</code> 包装成一个 <code>Resource</code> 返回。</p>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line">Resource <span class="title function_">getResource</span><span class="params">(<span class="keyword">final</span> String name, <span class="type">boolean</span> check)</span> &#123;</span><br><span class="line">    <span class="keyword">final</span> URL url;</span><br><span class="line">    <span class="keyword">try</span> &#123;</span><br><span class="line">        <span class="type">URL</span> <span class="variable">normalizedBase</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">URL</span>(getBaseURL(), <span class="string">&quot;.&quot;</span>);</span><br><span class="line">        url = <span class="keyword">new</span> <span class="title class_">URL</span>(getBaseURL(), ParseUtil.encodePath(name, <span class="literal">false</span>));</span><br><span class="line"></span><br><span class="line">        <span class="keyword">if</span> (url.getFile().startsWith(normalizedBase.getFile()) == <span class="literal">false</span>) &#123;</span><br><span class="line">            <span class="comment">// requested resource had ../..&#x27;s in path</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"></span><br><span class="line">        <span class="keyword">if</span> (check)</span><br><span class="line">            URLClassPath.check(url);</span><br><span class="line"></span><br><span class="line">        <span class="keyword">final</span> File file;</span><br><span class="line">        <span class="keyword">if</span> (name.indexOf(<span class="string">&quot;..&quot;</span>) != -<span class="number">1</span>) &#123;</span><br><span class="line">            file = (<span class="keyword">new</span> <span class="title class_">File</span>(dir, name.replace(<span class="string">&#x27;/&#x27;</span>, File.separatorChar)))</span><br><span class="line">                    .getCanonicalFile();</span><br><span class="line">            <span class="keyword">if</span> ( !((file.getPath()).startsWith(dir.getPath())) ) &#123;</span><br><span class="line">                <span class="comment">/* outside of base dir */</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 class="keyword">else</span> &#123;</span><br><span class="line">            file = <span class="keyword">new</span> <span class="title class_">File</span>(dir, name.replace(<span class="string">&#x27;/&#x27;</span>, File.separatorChar));</span><br><span class="line">        &#125;</span><br><span class="line"></span><br><span class="line">        <span class="keyword">if</span> (file.exists()) &#123;</span><br><span class="line">            <span class="keyword">return</span> <span class="keyword">new</span> <span class="title class_">Resource</span>() &#123;</span><br><span class="line">                <span class="keyword">public</span> String <span class="title function_">getName</span><span class="params">()</span> &#123; <span class="keyword">return</span> name; &#125;;</span><br><span class="line">                <span class="keyword">public</span> URL <span class="title function_">getURL</span><span class="params">()</span> &#123; <span class="keyword">return</span> url; &#125;;</span><br><span class="line">                <span class="keyword">public</span> URL <span class="title function_">getCodeSourceURL</span><span class="params">()</span> &#123; <span class="keyword">return</span> getBaseURL(); &#125;;</span><br><span class="line">                <span class="keyword">public</span> InputStream <span class="title function_">getInputStream</span><span class="params">()</span> <span class="keyword">throws</span> IOException</span><br><span class="line">                    &#123; <span class="keyword">return</span> <span class="keyword">new</span> <span class="title class_">FileInputStream</span>(file); &#125;;</span><br><span class="line">                <span class="keyword">public</span> <span class="type">int</span> <span class="title function_">getContentLength</span><span class="params">()</span> <span class="keyword">throws</span> IOException</span><br><span class="line">                    &#123; <span class="keyword">return</span> (<span class="type">int</span>)file.length(); &#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">        <span class="keyword">return</span> <span class="literal">null</span>;</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>
+<h3 id="回调-getEarlyBeanReference"><a href="#回调-getEarlyBeanReference" class="headerlink" title="回调 getEarlyBeanReference"></a>回调 getEarlyBeanReference</h3><p>如果存在 SmartInstantiationAwareBeanPostProcessor，将使用这些后处理器获得早期 bean 引用。</p>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">protected</span> Object <span class="title function_">getEarlyBeanReference</span><span class="params">(String beanName, RootBeanDefinition mbd, Object bean)</span> &#123;</span><br><span class="line">    <span class="type">Object</span> <span class="variable">exposedObject</span> <span class="operator">=</span> bean;</span><br><span class="line">    <span class="keyword">if</span> (bean != <span class="literal">null</span> &amp;&amp; !mbd.isSynthetic() &amp;&amp; hasInstantiationAwareBeanPostProcessors()) &#123;</span><br><span class="line">        <span class="comment">// 如果存在 InstantiationAwareBeanPostProcessors</span></span><br><span class="line">        <span class="keyword">for</span> (BeanPostProcessor bp : getBeanPostProcessors()) &#123;</span><br><span class="line">            <span class="keyword">if</span> (bp <span class="keyword">instanceof</span> SmartInstantiationAwareBeanPostProcessor) &#123;</span><br><span class="line">                <span class="comment">// 如果 bp 是 SmartInstantiationAwareBeanPostProcessor 类型</span></span><br><span class="line">                <span class="type">SmartInstantiationAwareBeanPostProcessor</span> <span class="variable">ibp</span> <span class="operator">=</span> (SmartInstantiationAwareBeanPostProcessor) bp;</span><br><span class="line">                <span class="comment">// 尝试创建代理</span></span><br><span class="line">                exposedObject = ibp.getEarlyBeanReference(exposedObject, beanName);</span><br><span class="line">                <span class="keyword">if</span> (exposedObject == <span class="literal">null</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">            &#125;</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="keyword">return</span> exposedObject;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
 
-<h4 id="ClassLoader-的搜索路径"><a href="#ClassLoader-的搜索路径" class="headerlink" title="ClassLoader 的搜索路径"></a>ClassLoader 的搜索路径</h4><p>从上文可知，<code>ClassLoader</code> 调用 <code>findClass</code> 方法查找类的时候，并不是漫无目的地查找，而是根据设置的类路径进行查找，不同的 <code>ClassLoader</code> 有不同的类路径。</p>
-<p>以下是通过 <code>IDEA</code> 启动 <code>Java</code> 程序时的命令，可以看到其中通过 <code>-classpath</code> 指定了应用·类加载器 <code>AppClassLoader</code> 的类路径，该类路径除了包含常规的 <code>JRE</code> 的文件路径外，还额外添加了当前 <code>maven</code> 工程编译生成的 <code>target\classes</code> 目录。</p>
-<figure class="highlight shell"><table><tr><td class="code"><pre><span class="line">C:\Users\xxx\.jdks\corretto-1.8.0_342\bin\java.exe -agentlib:jdwp=transport=dt_socket,address=127.0.0.1:52959,suspend=y,server=n -javaagent:C:\Users\xxx\AppData\Local\JetBrains\IntelliJIdea2022.3\captureAgent\debugger-agent.jar -Dfile.encoding=UTF-8 -classpath &quot;C:\Users\xxx\.jdks\corretto-1.8.0_342\jre\lib\charsets.jar;C:\Users\xxx\.jdks\corretto-1.8.0_342\jre\lib\ext\access-bridge-64.jar;C:\Users\xxx\.jdks\corretto-1.8.0_342\jre\lib\ext\cldrdata.jar;C:\Users\xxx\.jdks\corretto-1.8.0_342\jre\lib\ext\dnsns.jar;C:\Users\xxx\.jdks\corretto-1.8.0_342\jre\lib\ext\jaccess.jar;C:\Users\xxx\.jdks\corretto-1.8.0_342\jre\lib\ext\jfxrt.jar;C:\Users\xxx\.jdks\corretto-1.8.0_342\jre\lib\ext\localedata.jar;C:\Users\xxx\.jdks\corretto-1.8.0_342\jre\lib\ext\nashorn.jar;C:\Users\xxx\.jdks\corretto-1.8.0_342\jre\lib\ext\sunec.jar;C:\Users\xxx\.jdks\corretto-1.8.0_342\jre\lib\ext\sunjce_provider.jar;C:\Users\xxx\.jdks\corretto-1.8.0_342\jre\lib\ext\sunmscapi.jar;C:\Users\xxx\.jdks\corretto-1.8.0_342\jre\lib\ext\sunpkcs11.jar;C:\Users\xxx\.jdks\corretto-1.8.0_342\jre\lib\ext\zipfs.jar;C:\Users\xxx\.jdks\corretto-1.8.0_342\jre\lib\jce.jar;C:\Users\xxx\.jdks\corretto-1.8.0_342\jre\lib\jfr.jar;C:\Users\xxx\.jdks\corretto-1.8.0_342\jre\lib\jfxswt.jar;C:\Users\xxx\.jdks\corretto-1.8.0_342\jre\lib\jsse.jar;C:\Users\xxx\.jdks\corretto-1.8.0_342\jre\lib\management-agent.jar;C:\Users\xxx\.jdks\corretto-1.8.0_342\jre\lib\resources.jar;C:\Users\xxx\.jdks\corretto-1.8.0_342\jre\lib\rt.jar;C:\Users\xxx\IdeaProjects\java-test\target\classes;C:\Program Files\JetBrains\IntelliJ IDEA 2022.3.3\lib\idea_rt.jar&quot; org.example.BananaTest</span><br></pre></td></tr></table></figure>
+<h3 id="获取早期-bean-引用"><a href="#获取早期-bean-引用" class="headerlink" title="获取早期 bean 引用"></a>获取早期 bean 引用</h3><p>了解<a href="/2023/11/19/how-does-Spring-AOP-create-proxy-beans/" title="Spring AOP 如何创建代理 beans">Spring AOP 如何创建代理 beans</a>，才能更好地理解这部分内容。</p>
+<p>通过后处理器 getEarlyBeanReference 获取早期 bean 引用时，可能返回的就是 circularA 对象，但是如果 circularA 属于需要创建代理的 bean，就会在这时候立即为它创建代理，而在之后 BeanPostProcessor 处理时就不会再创建代理了。</p>
+<p>以 AbstractAutoProxyCreator 为例，它是自动代理创建者的抽象类，同时实现了 SmartInstantiationAwareBeanPostProcessor 和 BeanPostProcessor 接口。</p>
+<h4 id="SmartInstantiationAwareBeanPostProcessor-的方法实现"><a href="#SmartInstantiationAwareBeanPostProcessor-的方法实现" class="headerlink" title="SmartInstantiationAwareBeanPostProcessor 的方法实现"></a>SmartInstantiationAwareBeanPostProcessor 的方法实现</h4><p>SmartInstantiationAwareBeanPostProcessor 接口允许在获取 circularA 的早期引用时，就尝试将 circular A 包装为代理。</p>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> Object <span class="title function_">getEarlyBeanReference</span><span class="params">(Object bean, String beanName)</span> <span class="keyword">throws</span> BeansException &#123;</span><br><span class="line">    <span class="type">Object</span> <span class="variable">cacheKey</span> <span class="operator">=</span> getCacheKey(bean.getClass(), beanName);</span><br><span class="line">    <span class="keyword">if</span> (!<span class="built_in">this</span>.earlyProxyReferences.contains(cacheKey)) &#123;</span><br><span class="line">        <span class="built_in">this</span>.earlyProxyReferences.add(cacheKey);</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="comment">// 如有必要，包装为代理</span></span><br><span class="line">    <span class="keyword">return</span> wrapIfNecessary(bean, beanName, cacheKey);</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
 
-<h5 id="bootstrap-class-loader"><a href="#bootstrap-class-loader" class="headerlink" title="bootstrap class loader"></a>bootstrap class loader</h5><p>启动·类加载器 <code>bootstrap class loader</code>，加载核心类库，即 <code>&lt;JRE_HOME&gt;/lib</code> 目录中的部分类库，如 <code>rt.jar</code>，只有名字符合要求的 <code>jar</code> 才能被识别。 启动 Java 虚拟机时可以通过选项 <code>-Xbootclasspath</code> 修改默认的类路径，有三种使用方式：</p>
-<ul>
-<li><code>-Xbootclasspath:</code>：完全覆盖核心类库的类路径，不常用，除非重写核心类库。</li>
-<li><code>-Xbootclasspath/a:</code> 以后缀的方式拼接在原搜索路径后面，常用。</li>
-<li><code>-Xbootclasspath/p:</code> 以前缀的方式拼接再原搜索路径前面.不常用，避免引起不必要的冲突。</li>
-</ul>
-<p>在 <code>IDEA</code> 中编辑启动配置，添加 <code>VM</code> 选项，<code>-Xbootclasspath:C:\Software</code>，里面没有类文件，启动虚拟机失败，提示：</p>
-<figure class="highlight shell"><table><tr><td class="code"><pre><span class="line">Error occurred during initialization of VM</span><br><span class="line">java/lang/NoClassDefFoundError: java/lang/Object</span><br><span class="line"></span><br><span class="line">进程已结束,退出代码1</span><br></pre></td></tr></table></figure>
+<h4 id="BeanPostProcessor-的方法实现"><a href="#BeanPostProcessor-的方法实现" class="headerlink" title="BeanPostProcessor 的方法实现"></a>BeanPostProcessor 的方法实现</h4><p>BeanPostProcessor 接口允许在初始化时，调用初始化方法后，尝试将 circular A 包装为代理。如果已经在获取 circularA 的早期引用时就将其包装为代理，则不再进行包装。</p>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> Object <span class="title function_">postProcessAfterInitialization</span><span class="params">(Object bean, String beanName)</span> <span class="keyword">throws</span> BeansException &#123;</span><br><span class="line">    <span class="keyword">if</span> (bean != <span class="literal">null</span>) &#123;</span><br><span class="line">        <span class="type">Object</span> <span class="variable">cacheKey</span> <span class="operator">=</span> getCacheKey(bean.getClass(), beanName);</span><br><span class="line">        <span class="comment">// 判断早期代理引用中是否存在</span></span><br><span class="line">        <span class="keyword">if</span> (!<span class="built_in">this</span>.earlyProxyReferences.contains(cacheKey)) &#123;</span><br><span class="line">            <span class="keyword">return</span> wrapIfNecessary(bean, beanName, cacheKey);</span><br><span class="line">        &#125;</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></pre></td></tr></table></figure>
 
-<h5 id="ExtClassLoader"><a href="#ExtClassLoader" class="headerlink" title="ExtClassLoader"></a>ExtClassLoader</h5><p>扩展·类加载器 <code>ExtClassLoader</code>，加载 <code>&lt;JRE_HOME&gt;/lib/ext/</code> 目录中的类库。启动 <code>Java</code> 虚拟机时可以通过选项 <code>-Djava.ext.dirs</code> 修改默认的类路径。显然修改不当同样可能会引起 <code>Java</code> 程序的异常。</p>
-<h5 id="AppClassLoader"><a href="#AppClassLoader" class="headerlink" title="AppClassLoader"></a>AppClassLoader</h5><p>应用·类加载器 <code>AppClassLoader</code> ，加载应用级别的搜索路径中的类库。可以使用系统的环境变量 <code>CLASSPATH</code> 的值，也可以在启动 Java 虚拟机时通过选项 <code>-classpath</code> 修改。</p>
-<p><code>CLASSPATH</code> 在 <code>Windows</code> 中，多个文件路径使用分号 <code>;</code> 分隔，而 <code>Linux</code> 中则使用冒号 <code>:</code> 分隔。以下例子表示当前目录和另一个文件路径拼接而成的类路径。</p>
+<h2 id="再思-Spring-bean-的三级缓存"><a href="#再思-Spring-bean-的三级缓存" class="headerlink" title="再思 Spring bean 的三级缓存"></a>再思 Spring bean 的三级缓存</h2><h3 id="三级缓存还是三个缓存"><a href="#三级缓存还是三个缓存" class="headerlink" title="三级缓存还是三个缓存"></a>三级缓存还是三个缓存</h3><p>著名的“三级缓存”，实际上就是三个存放 Bean 的 map：</p>
 <ul>
-<li>Windows：<code>.;C:\path\to\classes</code></li>
-<li>Linux：<code>.:/path/to/classes</code></li>
+<li>singletonObjects</li>
+<li>earlySingletonObjects</li>
+<li>singletonFactories</li>
 </ul>
-<p>事实上，<code>AppClassLoader</code> 最终的类路径，不仅仅包含 <code>-classpath</code> 的值，还会包含 <code>-javaagent</code> 指定的值。</p>
-<h3 id="字节数据转换为-Class-实例：defineClass"><a href="#字节数据转换为-Class-实例：defineClass" class="headerlink" title="字节数据转换为 Class 实例：defineClass"></a>字节数据转换为 Class 实例：defineClass</h3><p>方法 <code>defineClass</code>，顾名思义，就是定义类，将字节数据转换为 <code>Class</code> 实例。在 <code>ClassLoader</code> 以及其子类中有很多同名方法，方法内各种处理和包装，最终都是为了使用 <code>name</code> 和字节数据等参数，调用 <code>native</code> 方法获得一个 <code>Class</code> 实例。<br>以下是定义类时最终可能调用的 <code>native</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">native</span> Class&lt;?&gt; defineClass0(String name, <span class="type">byte</span>[] b, <span class="type">int</span> off, <span class="type">int</span> len,</span><br><span class="line">                                     ProtectionDomain pd);</span><br><span class="line"></span><br><span class="line"><span class="keyword">private</span> <span class="keyword">native</span> Class&lt;?&gt; defineClass1(String name, <span class="type">byte</span>[] b, <span class="type">int</span> off, <span class="type">int</span> len,</span><br><span class="line">                                     ProtectionDomain pd, String source);</span><br><span class="line"></span><br><span class="line"><span class="keyword">private</span> <span class="keyword">native</span> Class&lt;?&gt; defineClass2(String name, java.nio.ByteBuffer b,</span><br><span class="line">                                     <span class="type">int</span> off, <span class="type">int</span> len, ProtectionDomain pd,</span><br><span class="line">                                     String source);</span><br></pre></td></tr></table></figure>
+<p>在很多网上的资料中，都称 Spring 通过使用三级缓存的设计解决了循环引用问题。<br>同时我也看到有人反思，这样翻译对学习者造成了很大的困扰，代码中并没有多级 cache 的意味，称之为“三个缓存”比“三级缓存”更合理也更容易理解。<br>三个存放 Bean 的 map 事实上是相互独立的，甚至说它们是互斥的，<strong>一个 Bean 在同一时间最多只能存在于其中一个 map 中</strong>。</p>
+<p>对我个人而言，我对反对者的观点深有同感，如果我没有看过面经，即使我熟读并理解代码，我可能都无法回答 Spring 中的三级缓存是什么。甚至我会被三级缓存这个名词所震慑，在了解它之前在心里放大它的复杂性。<br>但是在不断阅读的过程中（可能也有已有记忆的加持），我也会感受到称之为“三级缓存”的合理性。这里的分级含义更多体现的是 Bean 的“晋升”过程。</p>
+<h3 id="缓存中的添加和删除"><a href="#缓存中的添加和删除" class="headerlink" title="缓存中的添加和删除"></a>缓存中的添加和删除</h3><p>网上很多资料在讨论 Bean 在缓存中的添加和删除时，大多一笔带过，并没有谈到细节。但是 Bean 并不是在这三个缓存中连续晋级，甚至有时候，添加和移除的都不是一个对象。</p>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">protected</span> Object <span class="title function_">doCreateBean</span><span class="params">(<span class="keyword">final</span> String beanName, <span class="keyword">final</span> RootBeanDefinition mbd, <span class="keyword">final</span> Object[] args)</span></span><br><span class="line">        <span class="keyword">throws</span> BeanCreationException &#123;</span><br><span class="line">    <span class="comment">// 实例化</span></span><br><span class="line">    instanceWrapper = createBeanInstance(beanName, mbd, args);</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 单例+允许循环引用+当前正在被创建=可能需要提前暴露</span></span><br><span class="line">    <span class="type">boolean</span> <span class="variable">earlySingletonExposure</span> <span class="operator">=</span> (mbd.isSingleton() &amp;&amp; <span class="built_in">this</span>.allowCircularReferences &amp;&amp;</span><br><span class="line">            isSingletonCurrentlyInCreation(beanName));</span><br><span class="line">    <span class="keyword">if</span> (earlySingletonExposure) &#123;</span><br><span class="line">        addSingletonFactory(beanName, <span class="keyword">new</span> <span class="title class_">ObjectFactory</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_">getObject</span><span class="params">()</span> <span class="keyword">throws</span> BeansException &#123;</span><br><span class="line">                <span class="keyword">return</span> getEarlyBeanReference(beanName, mbd, bean);</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="type">Object</span> <span class="variable">exposedObject</span> <span class="operator">=</span> bean;</span><br><span class="line">    <span class="keyword">try</span> &#123;</span><br><span class="line">        <span class="comment">// 这里面会进行依赖注入</span></span><br><span class="line">        populateBean(beanName, mbd, instanceWrapper);</span><br><span class="line">        <span class="keyword">if</span> (exposedObject != <span class="literal">null</span>) &#123;</span><br><span class="line">            <span class="comment">// 这里面会尝试创建代理</span></span><br><span class="line">            exposedObject = initializeBean(beanName, exposedObject, mbd);</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> (earlySingletonExposure) &#123;</span><br><span class="line">        <span class="comment">// 如果允许早期暴露，尝试获取早期 bean 引用</span></span><br><span class="line">        <span class="type">Object</span> <span class="variable">earlySingletonReference</span> <span class="operator">=</span> getSingleton(beanName, <span class="literal">false</span>);</span><br><span class="line">        <span class="comment">// 如果为 null 说明没有早期暴露，返回的其实还是最初的 exposedObject</span></span><br><span class="line">        <span class="comment">// 三级缓存里的 ObjectFactory 完全没用上，会在 exposedObject 添加到一级缓存时直接删除</span></span><br><span class="line">        <span class="keyword">if</span> (earlySingletonReference != <span class="literal">null</span>) &#123;</span><br><span class="line">            <span class="comment">// 如果不为 null，说明确实早期暴露过</span></span><br><span class="line">            <span class="keyword">if</span> (exposedObject == bean) &#123;</span><br><span class="line">                <span class="comment">// 如果早期暴露过，常规情况下，exposedObject 不会再创建代理，应 == bean</span></span><br><span class="line">                <span class="comment">// 如果没有代理，exposedObject == bean == earlySingletonReference</span></span><br><span class="line">                <span class="comment">// 如果创建过代理，earlySingletonReference 才是包装过的代理</span></span><br><span class="line">                exposedObject = earlySingletonReference;</span><br><span class="line">            &#125;</span><br><span class="line">            <span class="keyword">else</span> <span class="keyword">if</span> (!<span class="built_in">this</span>.allowRawInjectionDespiteWrapping &amp;&amp; hasDependentBean(beanName)) &#123;</span><br><span class="line">                <span class="comment">// 如果 exposedObject 在 initializeBean 中再次被创建代理</span></span><br><span class="line">                <span class="comment">// 但是存在 Bean 依赖了这个 Bean（由于拿到的是早期引用），它们拿到的和最终的是不同的对象</span></span><br><span class="line">                <span class="comment">// 如果不允许尽管会被包装仍然注入原始类型，就需要抛出异常</span></span><br><span class="line">                String[] dependentBeans = getDependentBeans(beanName);</span><br><span class="line">                Set&lt;String&gt; actualDependentBeans = <span class="keyword">new</span> <span class="title class_">LinkedHashSet</span>&lt;String&gt;(dependentBeans.length);</span><br><span class="line">                <span class="keyword">for</span> (String dependentBean : dependentBeans) &#123;</span><br><span class="line">                    <span class="keyword">if</span> (!removeSingletonIfCreatedForTypeCheckOnly(dependentBean)) &#123;</span><br><span class="line">                        actualDependentBeans.add(dependentBean);</span><br><span class="line">                    &#125;</span><br><span class="line">                &#125;</span><br><span class="line">                <span class="keyword">if</span> (!actualDependentBeans.isEmpty()) &#123;</span><br><span class="line">                    <span class="comment">// 抛异常</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 class="keyword">return</span> exposedObject;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
 
-<p>其方法参数有：</p>
+<img src="/2023/11/22/circular-dependencies-in-Spring/Pasted%20image%2020231123013242.png" class="" title="循环引用-三级缓存添加和删除">
+
+<h4 id="无需早期暴露的情况"><a href="#无需早期暴露的情况" class="headerlink" title="无需早期暴露的情况"></a>无需早期暴露的情况</h4><p>在无需早期暴露的情况下，二级缓存没有用到，虽然三级缓存中保存了一个 ObjectFactory，但是也是没有用到的。bean 直接保存到了一级缓存。</p>
+<h4 id="需要早期暴露但无需代理"><a href="#需要早期暴露但无需代理" class="headerlink" title="需要早期暴露但无需代理"></a>需要早期暴露但无需代理</h4><p>在需要早期暴露但无需代理的情况下，尽管获取早期引用后保存在二级缓存中，以供重复使用，但是二级缓存中和原始的 bean 仍然是同一个对象，bean 仍然是直接保存到了一级缓存，再删掉二级缓存。</p>
+<h4 id="需要早期暴露也需要代理"><a href="#需要早期暴露也需要代理" class="headerlink" title="需要早期暴露也需要代理"></a>需要早期暴露也需要代理</h4><p>只有在需要早期暴露和需要代理的情况下，二级缓存中保存的是代理对象，需要从二级缓存中获取再保存到一级缓存中，然后再删除二级缓存。</p>
+<h3 id="必须要三个缓存吗"><a href="#必须要三个缓存吗" class="headerlink" title="必须要三个缓存吗"></a>必须要三个缓存吗</h3><p>网上有很多资料在分析为什么需要三个缓存，才能解决在需要创建代理的情况下发生的循环依赖问题。<br>但是个人觉得有些分析缺乏逻辑，也有点违和感。将当前的解决方案套到只有两个缓存的情况下去分析不太合理，就像你把四轮机动车卸掉一个轮子，说机动车必须要四个轮子才可以，不然不平衡，事实上三个轮子的机动车是存在的。</p>
+<p>在分析两个缓存如何解决在需要创建代理的情况下发生的循环依赖问题时，应该抛开现有的处理逻辑，回归本质问题：既然 circularA 需要创建代理，如果 circularA 依赖的 beans 也依赖了 circular A，在为它们获取 circularA 时立即创建代理即可。<br>一个 map 必须用于存放完成品，另一个 map 用于存放半成品。创建的代理作为升级版的半成品，完全可以覆盖原始的半成品继续存放在第二个 map 中。为了避免重复创建代理，只要能够标识半成品是已经经过代理包装的即可。beanDefinition、bean 自身、创建代理的地方，都有能力实现标识一个 bean 的半成品是否经过包装，最不济使用一个 map 存放标识（但是这也就等同于使用三个 map 了，从这个角度看，三级缓存的缓存意味更加淡了）。<br>甚至可以将半成品 circularA 直接尝试包装成代理，再存放入半成品 map 中。本质上是将创建代理的步骤从初始化 Bean 中分离到初始化 Bean 之前。</p>
+<p>综上，使用两个 map 解决在技术上是没有问题的，很多分析中考虑的问题相当于把 Spring 现有的处理逻辑当成枷锁限制了自己。既然你都在问不这么打地基可不可以，我难道不得考虑挪一挪上面的砖墙吗？当然我不能保证这么设计不会破坏 Spring 现有全部功能的兼容性和扩展性，但是这并不是代理为循环依赖引入的问题。</p>
+]]></content>
+      <tags>
+        <tag>java</tag>
+        <tag>spring</tag>
+      </tags>
+  </entry>
+  <entry>
+    <title>Spring AOP 如何创建代理 beans</title>
+    <url>/2023/11/19/how-does-Spring-AOP-create-proxy-beans/</url>
+    <content><![CDATA[<p>Spring AOP 是基于代理实现的，它既支持 JDK 动态代理也支持 CGLib。</p>
 <ul>
-<li><code>name</code>，目标类的名称。</li>
-<li><code>byte[]</code> 或 <code>ByteBuffer</code> 类型的字节数据，<code>off</code> 和 <code>len</code> 只是为了定位传入的字节数组中关于目标类的字节数据，通常分别是 0 和字节数组的长度，毕竟专门构造一个包含无关数据的字节数组很无聊。</li>
-<li><code>ProtectionDomain</code>，保护域，todo:</li>
-<li><code>source</code>，<code>CodeSource</code> 的位置。</li>
+<li>在什么时候创建代理对象的？</li>
+<li>怎么创建代理对象的？</li>
 </ul>
-<p><code>defineClass</code> 方法的调用过程，其实就是从 <code>URLClassLoader</code> 开始，一层一层处理后再调用父类的 <code>defineClass</code> 方法，分别经过了 <code>SecureClassLoader</code> 和 <code>ClassLoader</code>。</p>
-<h4 id="URLClassLoader-defineClass"><a href="#URLClassLoader-defineClass" class="headerlink" title="URLClassLoader#defineClass"></a>URLClassLoader#defineClass</h4><p>此方法是再 <code>URLClassLoader</code> 的 <code>findClass</code> 方法中，获得正确的 <code>Resource</code> 之后调用的，由 <code>private</code> 修饰。根据注释，它使用从指定资源获取的类字节来定义类，生成的类必须先解析才能使用。</p>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">private</span> Class&lt;?&gt; defineClass(String name, Resource res) <span class="keyword">throws</span> IOException &#123;</span><br><span class="line">    <span class="type">long</span> <span class="variable">t0</span> <span class="operator">=</span> System.nanoTime();</span><br><span class="line">    <span class="comment">// 获取最后一个 . 的位置</span></span><br><span class="line">    <span class="type">int</span> <span class="variable">i</span> <span class="operator">=</span> name.lastIndexOf(<span class="string">&#x27;.&#x27;</span>);</span><br><span class="line">    <span class="comment">// 返回资源的 CodeSourceURL</span></span><br><span class="line">    <span class="type">URL</span> <span class="variable">url</span> <span class="operator">=</span> res.getCodeSourceURL();</span><br><span class="line">    <span class="keyword">if</span> (i != -<span class="number">1</span>) &#123;</span><br><span class="line">        <span class="comment">// 截取包名 com.example</span></span><br><span class="line">        <span class="type">String</span> <span class="variable">pkgname</span> <span class="operator">=</span> name.substring(<span class="number">0</span>, i);</span><br><span class="line">        <span class="comment">// Check if package already loaded.</span></span><br><span class="line">        <span class="type">Manifest</span> <span class="variable">man</span> <span class="operator">=</span> res.getManifest();</span><br><span class="line">        definePackageInternal(pkgname, man, url);</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="comment">// Now read the class bytes and define the class</span></span><br><span class="line">    <span class="comment">// 先尝试以 ByteBuffer 的形式返回字节数据，如果资源的输入流不是在 ByteBuffer 之上实现的，则返回 null</span></span><br><span class="line">    java.nio.<span class="type">ByteBuffer</span> <span class="variable">bb</span> <span class="operator">=</span> res.getByteBuffer();</span><br><span class="line">    <span class="keyword">if</span> (bb != <span class="literal">null</span>) &#123;</span><br><span class="line">        <span class="comment">// Use (direct) ByteBuffer:</span></span><br><span class="line">        <span class="comment">// 不常用</span></span><br><span class="line">        CodeSigner[] signers = res.getCodeSigners();</span><br><span class="line">        <span class="type">CodeSource</span> <span class="variable">cs</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">CodeSource</span>(url, signers);</span><br><span class="line">        sun.misc.PerfCounter.getReadClassBytesTime().addElapsedTimeFrom(t0);</span><br><span class="line">        <span class="comment">// 调用 java.security.SecureClassLoader#defineClass(java.lang.String, java.nio.ByteBuffer, java.security.CodeSource)</span></span><br><span class="line">        <span class="keyword">return</span> defineClass(name, bb, cs);</span><br><span class="line">    &#125; <span class="keyword">else</span> &#123;</span><br><span class="line">        <span class="comment">// 以字节数组的形式返回资源数据</span></span><br><span class="line">        <span class="type">byte</span>[] b = res.getBytes();</span><br><span class="line">        <span class="comment">// must read certificates AFTER reading bytes.</span></span><br><span class="line">        <span class="comment">// 必须再读取字节数据后读取证书，todo:</span></span><br><span class="line">        CodeSigner[] signers = res.getCodeSigners();</span><br><span class="line">        <span class="comment">// 根据 URL 和签名者创建 CodeSource</span></span><br><span class="line">        <span class="type">CodeSource</span> <span class="variable">cs</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">CodeSource</span>(url, signers);</span><br><span class="line">        sun.misc.PerfCounter.getReadClassBytesTime().addElapsedTimeFrom(t0);</span><br><span class="line">        <span class="comment">// 调用 java.security.SecureClassLoader#defineClass(java.lang.String, byte[], int, int, java.security.CodeSource)</span></span><br><span class="line">        <span class="keyword">return</span> defineClass(name, b, <span class="number">0</span>, b.length, cs);</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
-
-<p><code>Resource</code> 类提供了 <code>getBytes</code> 方法，此方法以字节数组的形式返回字节数据。</p>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="type">byte</span>[] getBytes() <span class="keyword">throws</span> IOException &#123;</span><br><span class="line">    <span class="type">byte</span>[] b;</span><br><span class="line">    <span class="comment">// Get stream before content length so that a FileNotFoundException</span></span><br><span class="line">    <span class="comment">// can propagate upwards without being caught too early</span></span><br><span class="line">    <span class="comment">// 在获取内容长度之前获取流，以便 FileNotFoundException 可以向上传播而不会过早被捕获（todo: 不理解）</span></span><br><span class="line">    <span class="comment">// 获取缓存的 InputStream</span></span><br><span class="line">    <span class="type">InputStream</span> <span class="variable">in</span> <span class="operator">=</span> cachedInputStream();</span><br><span class="line"></span><br><span class="line">    <span class="comment">// This code has been uglified to protect against interrupts.</span></span><br><span class="line">    <span class="comment">// Even if a thread has been interrupted when loading resources,</span></span><br><span class="line">    <span class="comment">// the IO should not abort, so must carefully retry, failing only</span></span><br><span class="line">    <span class="comment">// if the retry leads to some other IO exception.</span></span><br><span class="line">    <span class="comment">// 该代码为了防止中断有点丑陋。即使线程在加载资源时被中断，IO 也不应该中止，因此必须小心重试，只有当重试导致其他 IO 异常时才会失败。</span></span><br><span class="line">    <span class="comment">// 检测当前线程是否收到中断信号，收到的话则返回 true 且清除中断状态，重新变更为未中断状态。</span></span><br><span class="line">    <span class="type">boolean</span> <span class="variable">isInterrupted</span> <span class="operator">=</span> Thread.interrupted();</span><br><span class="line">    <span class="type">int</span> len;</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">// 获取内容长度，顺利的话就跳出循环</span></span><br><span class="line">            len = getContentLength();</span><br><span class="line">            <span class="keyword">break</span>;</span><br><span class="line">        &#125; <span class="keyword">catch</span> (InterruptedIOException iioe) &#123;</span><br><span class="line">            <span class="comment">// 如果获取内容长度时，线程被中断抛出了异常，捕获后清除中断状态</span></span><br><span class="line">            Thread.interrupted();</span><br><span class="line">            isInterrupted = <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="keyword">try</span> &#123;</span><br><span class="line">        b = <span class="keyword">new</span> <span class="title class_">byte</span>[<span class="number">0</span>];</span><br><span class="line">        <span class="keyword">if</span> (len == -<span class="number">1</span>) len = Integer.MAX_VALUE;</span><br><span class="line">        <span class="type">int</span> <span class="variable">pos</span> <span class="operator">=</span> <span class="number">0</span>;</span><br><span class="line">        <span class="keyword">while</span> (pos &lt; len) &#123;</span><br><span class="line">            <span class="type">int</span> bytesToRead;</span><br><span class="line">            <span class="keyword">if</span> (pos &gt;= b.length) &#123; <span class="comment">// Only expand when there&#x27;s no room</span></span><br><span class="line">                <span class="comment">// 如果当前读取位置已经大于等于数组长度</span></span><br><span class="line">                <span class="comment">// 本次待读取字节长度 = 剩余未读取长度和 1024 取较小值</span></span><br><span class="line">                bytesToRead = Math.min(len - pos, b.length + <span class="number">1024</span>);</span><br><span class="line">                <span class="keyword">if</span> (b.length &lt; pos + bytesToRead) &#123;</span><br><span class="line">                    <span class="comment">// 如果当前读取位置 + 本次待读取字节长度 &gt; 数组长度，则创建新数组并复制数据</span></span><br><span class="line">                    b = Arrays.copyOf(b, pos + bytesToRead);</span><br><span class="line">                &#125;</span><br><span class="line">            &#125; <span class="keyword">else</span> &#123;</span><br><span class="line">                <span class="comment">// 数组还有空间，待读取字节长度 = 数组剩余空间</span></span><br><span class="line">                bytesToRead = b.length - pos;</span><br><span class="line">            &#125;</span><br><span class="line">            <span class="type">int</span> <span class="variable">cc</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">// 读取数据</span></span><br><span class="line">                cc = in.read(b, pos, bytesToRead);</span><br><span class="line">            &#125; <span class="keyword">catch</span> (InterruptedIOException iioe) &#123;</span><br><span class="line">                <span class="comment">// 如果读取时，线程被中断抛出了异常，捕获后清除中断状态</span></span><br><span class="line">                Thread.interrupted();</span><br><span class="line">                isInterrupted = <span class="literal">true</span>;</span><br><span class="line">            &#125;</span><br><span class="line">            <span class="keyword">if</span> (cc &lt; <span class="number">0</span>) &#123;</span><br><span class="line">                <span class="comment">// 如果读取返回值 &lt; 0</span></span><br><span class="line">                <span class="keyword">if</span> (len != Integer.MAX_VALUE) &#123;</span><br><span class="line">                    <span class="comment">// 且长度并未无限，表示提前检测到 EOF，抛出异常</span></span><br><span class="line">                    <span class="keyword">throw</span> <span class="keyword">new</span> <span class="title class_">EOFException</span>(<span class="string">&quot;Detect premature EOF&quot;</span>);</span><br><span class="line">                &#125; <span class="keyword">else</span> &#123;</span><br><span class="line">                    <span class="comment">// 如果长度无限，表示读到了文件结尾，数组长度大于当前读取位置，创建新数组并复制长度</span></span><br><span class="line">                    <span class="keyword">if</span> (b.length != pos) &#123;</span><br><span class="line">                        b = Arrays.copyOf(b, pos);</span><br><span class="line">                    &#125;</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">            pos += cc;</span><br><span class="line">        &#125;</span><br><span class="line">    &#125; <span class="keyword">finally</span> &#123;</span><br><span class="line">        <span class="keyword">try</span> &#123;</span><br><span class="line">            in.close();</span><br><span class="line">        &#125; <span class="keyword">catch</span> (InterruptedIOException iioe) &#123;</span><br><span class="line">            isInterrupted = <span class="literal">true</span>;</span><br><span class="line">        &#125; <span class="keyword">catch</span> (IOException ignore) &#123;&#125;</span><br><span class="line"></span><br><span class="line">        <span class="keyword">if</span> (isInterrupted) &#123;</span><br><span class="line">            <span class="comment">// 如果 isInterrupted 为 true，代表中断过，重新将线程状态置为中断。</span></span><br><span class="line">            Thread.currentThread().interrupt();</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="keyword">return</span> b;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+<h2 id="过程简单图解"><a href="#过程简单图解" class="headerlink" title="过程简单图解"></a>过程简单图解</h2><img src="/2023/11/19/how-does-Spring-AOP-create-proxy-beans/Pasted%20image%2020231120223506.png" class="" title="Spring AOP 创建代理的过程">
 
-<p>在 <code>getByteBuffer</code> 之后会缓存 <code>InputStream</code> 以便调用 <code>getBytes</code> 时使用，方法由 <code>synchronized</code> 修饰。</p>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">private</span> <span class="keyword">synchronized</span> InputStream <span class="title function_">cachedInputStream</span><span class="params">()</span> <span class="keyword">throws</span> IOException &#123;</span><br><span class="line">    <span class="keyword">if</span> (cis == <span class="literal">null</span>) &#123;</span><br><span class="line">        cis = getInputStream();</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="keyword">return</span> cis;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+<h2 id="准备工作"><a href="#准备工作" class="headerlink" title="准备工作"></a>准备工作</h2><ul>
+<li>引入依赖<figure class="highlight xml"><table><tr><td class="code"><pre><span class="line"><span class="tag">&lt;<span class="name">dependency</span>&gt;</span></span><br><span class="line">    <span class="tag">&lt;<span class="name">groupId</span>&gt;</span>org.springframework<span class="tag">&lt;/<span class="name">groupId</span>&gt;</span></span><br><span class="line">    <span class="tag">&lt;<span class="name">artifactId</span>&gt;</span>spring-context<span class="tag">&lt;/<span class="name">artifactId</span>&gt;</span></span><br><span class="line">    <span class="tag">&lt;<span class="name">version</span>&gt;</span>4.3.12.RELEASE<span class="tag">&lt;/<span class="name">version</span>&gt;</span></span><br><span class="line"><span class="tag">&lt;/<span class="name">dependency</span>&gt;</span></span><br><span class="line"><span class="tag">&lt;<span class="name">dependency</span>&gt;</span></span><br><span class="line">    <span class="tag">&lt;<span class="name">groupId</span>&gt;</span>org.springframework<span class="tag">&lt;/<span class="name">groupId</span>&gt;</span></span><br><span class="line">    <span class="tag">&lt;<span class="name">artifactId</span>&gt;</span>spring-aspects<span class="tag">&lt;/<span class="name">artifactId</span>&gt;</span></span><br><span class="line">    <span class="tag">&lt;<span class="name">version</span>&gt;</span>4.3.12.RELEASE<span class="tag">&lt;/<span class="name">version</span>&gt;</span></span><br><span class="line"><span class="tag">&lt;/<span class="name">dependency</span>&gt;</span></span><br></pre></td></tr></table></figure></li>
+<li>目标对象类<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_">MathCalculator</span> &#123;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">public</span> <span class="type">int</span> <span class="title function_">div</span><span class="params">(<span class="type">int</span> i, <span class="type">int</span> j)</span> &#123;</span><br><span class="line">        <span class="keyword">return</span> i / j;</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure></li>
+<li>切面类<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="meta">@Aspect</span></span><br><span class="line"><span class="keyword">public</span> <span class="keyword">class</span> <span class="title class_">LogAspects</span> &#123;</span><br><span class="line"></span><br><span class="line">    <span class="meta">@Pointcut(&quot;execution(public int com.moralok.aop.MathCalculator.*(..))&quot;)</span></span><br><span class="line">    <span class="keyword">public</span> <span class="keyword">void</span> <span class="title function_">pointCut</span><span class="params">()</span> &#123;</span><br><span class="line"></span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="meta">@Before(&quot;pointCut()&quot;)</span></span><br><span class="line">    <span class="keyword">public</span> <span class="keyword">void</span> <span class="title function_">logStart</span><span class="params">(JoinPoint joinPoint)</span> &#123;</span><br><span class="line">        System.out.println(joinPoint.getSignature().getName() + <span class="string">&quot;除法运行@Before。。。参数列表为 &quot;</span> + Arrays.asList(joinPoint.getArgs()) + <span class="string">&quot;&quot;</span>);</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="meta">@After(&quot;pointCut()&quot;)</span></span><br><span class="line">    <span class="keyword">public</span> <span class="keyword">void</span> <span class="title function_">logEnd</span><span class="params">(JoinPoint joinPoint)</span> &#123;</span><br><span class="line">        System.out.println(joinPoint.getSignature().getName() + <span class="string">&quot;除法结束@After。。。&quot;</span>);</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="meta">@AfterReturning(value = &quot;pointCut()&quot;, returning = &quot;result&quot;)</span></span><br><span class="line">    <span class="keyword">public</span> <span class="keyword">void</span> <span class="title function_">logReturn</span><span class="params">(JoinPoint joinPoint, Object result)</span> &#123;</span><br><span class="line">        System.out.println(joinPoint.getSignature().getName() + <span class="string">&quot;除法正常返回@AfterReturning。。。运行结果 &quot;</span> + result);</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="meta">@AfterThrowing(value = &quot;pointCut()&quot;, throwing = &quot;e&quot;)</span></span><br><span class="line">    <span class="keyword">public</span> <span class="keyword">void</span> <span class="title function_">logException</span><span class="params">(JoinPoint joinPoint, Exception e)</span> &#123;</span><br><span class="line">        System.out.println(joinPoint.getSignature().getName() + <span class="string">&quot;除法异常@AfterThrowing。。。异常信息 &quot;</span> + e.getMessage());</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="meta">@Around(value = &quot;execution(public String com.moralok.bean.Car.getName(..))&quot;)</span></span><br><span class="line">    <span class="keyword">public</span> Object <span class="title function_">logAround</span><span class="params">(ProceedingJoinPoint joinPoint)</span> <span class="keyword">throws</span> Throwable &#123;</span><br><span class="line">        System.out.println(joinPoint.getSignature().getName() + <span class="string">&quot; @Around开始&quot;</span>);</span><br><span class="line">        <span class="type">Object</span> <span class="variable">proceed</span> <span class="operator">=</span> joinPoint.proceed();</span><br><span class="line">        System.out.println(joinPoint.getSignature().getName() + <span class="string">&quot; @Around结束&quot;</span>);</span><br><span class="line">        <span class="keyword">return</span> proceed;</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure></li>
+<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="meta">@EnableAspectJAutoProxy</span></span><br><span class="line"><span class="keyword">public</span> <span class="keyword">class</span> <span class="title class_">AopConfig</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> MathCalculator <span class="title function_">mathCalculator</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_">MathCalculator</span>();</span><br><span class="line">    &#125;</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> LogAspects <span class="title function_">logAspects</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_">LogAspects</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="keyword">public</span> <span class="keyword">class</span> <span class="title class_">AopTest</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">public</span> <span class="keyword">void</span> <span class="title function_">aopTest</span><span class="params">()</span> &#123;</span><br><span class="line">        <span class="type">AnnotationConfigApplicationContext</span> <span class="variable">ac</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">AnnotationConfigApplicationContext</span>(AopConfig.class);</span><br><span class="line">        <span class="type">MathCalculator</span> <span class="variable">mathCalculator</span> <span class="operator">=</span> ac.getBean(MathCalculator.class);</span><br><span class="line">        mathCalculator.div(<span class="number">1</span>, <span class="number">1</span>);</span><br><span class="line">        mathCalculator.div(<span class="number">1</span>, <span class="number">0</span>);</span><br><span class="line">        ac.close();</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure></li>
+<li>Debug 断点的判断条件（可选）<figure class="highlight console"><table><tr><td class="code"><pre><span class="line">beanName.equals(&quot;mathCalculator&quot;)</span><br></pre></td></tr></table></figure></li>
+</ul>
+<h2 id="创建代理-Bean-和创建普通-Bean-的区别"><a href="#创建代理-Bean-和创建普通-Bean-的区别" class="headerlink" title="创建代理 Bean 和创建普通 Bean 的区别"></a>创建代理 Bean 和创建普通 Bean 的区别</h2><p>其实创建代理 Bean 的过程和<a href="/2023/08/10/how-does-Spring-load-beans/" title="Spring Bean 加载过程">创建普通 Bean 的过程</a>直到进行初始化处理（initializeBean）前都是一样的。更具体地说，如很多资料所言，Spring 创建代理对象的工作，是在应用后置处理器阶段完成的。</p>
+<h3 id="常规的入口-getBean"><a href="#常规的入口-getBean" class="headerlink" title="常规的入口 getBean"></a>常规的入口 getBean</h3><p>mathCalculator 以 getBean 方法为起点，开始创建的过程。</p>
+<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="comment">// ...（mathCalculator）</span></span><br><span class="line">    getBean(beanName);</span><br><span class="line">    <span class="comment">// ...</span></span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
 
-<p>在这个例子中，<code>Resource</code> 的实例是 <code>URLClassPath</code> 中的匿名类 <code>FileLoader</code> 以 <code>Resource</code> 的匿名类的方式创建的。</p>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> InputStream <span class="title function_">getInputStream</span><span class="params">()</span> <span class="keyword">throws</span> IOException</span><br><span class="line">&#123;</span><br><span class="line">    <span class="comment">// 在该匿名类中，getInputStream 的实现就是简单地根据 FileLoader 中保存的 File 实例创建 FileInputStream 并返回。</span></span><br><span class="line">    <span class="keyword">return</span> <span class="keyword">new</span> <span class="title class_">FileInputStream</span>(file);</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_">getContentLength</span><span class="params">()</span> <span class="keyword">throws</span> IOException</span><br><span class="line">&#123;</span><br><span class="line">    <span class="comment">// 在该匿名类中，getContentLength 的实现就是简单地根据 FileLoader 中保存的 File 实例获取长度。</span></span><br><span class="line">    <span class="keyword">return</span> (<span class="type">int</span>)file.length();</span><br><span class="line">&#125;;</span><br></pre></td></tr></table></figure>
+<h3 id="应用后置处理器"><a href="#应用后置处理器" class="headerlink" title="应用后置处理器"></a>应用后置处理器</h3><p>在正常地实例化 Bean 后，初始化 Bean 时，会对 Bean 实例应用后置处理器。</p>
+<p>可是，<strong>究竟是哪一个后置处理器做的呢</strong>？</p>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">protected</span> Object <span class="title function_">initializeBean</span><span class="params">(<span class="keyword">final</span> String beanName, <span class="keyword">final</span> Object bean, RootBeanDefinition mbd)</span> &#123;</span><br><span class="line">    <span class="comment">// ...</span></span><br><span class="line">    wrappedBean = applyBeanPostProcessorsBeforeInitialization(wrappedBean, beanName);</span><br><span class="line">    <span class="comment">// ...</span></span><br><span class="line">    invokeInitMethods(beanName, wrappedBean, mbd);</span><br><span class="line">    <span class="comment">// ...</span></span><br><span class="line">    wrappedBean = applyBeanPostProcessorsAfterInitialization(wrappedBean, beanName);</span><br><span class="line">    <span class="keyword">return</span> wrappedBean;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
 
-<h4 id="SecureClassLoader-defineClass"><a href="#SecureClassLoader-defineClass" class="headerlink" title="SecureClassLoader#defineClass"></a>SecureClassLoader#defineClass</h4><p><code>URLClassLoader</code> 继承自 <code>SecureClassLoader</code>，<code>SecureClassLoader</code> 提供并重载了 <code>defineClass</code> 方法，两个方法的注释均比代码长得多。<br>由注释可知，方法的作用是将字节数据（<code>byte[]</code> 类型或者 <code>ByteBuffer</code> 类型）转换为 <code>Class</code> 类型的实例，有一个可选的 <code>CodeSource</code> 类型的参数。</p>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">protected</span> <span class="keyword">final</span> Class&lt;?&gt; defineClass(String name,</span><br><span class="line">                                     <span class="type">byte</span>[] b, <span class="type">int</span> off, <span class="type">int</span> len,</span><br><span class="line">                                     CodeSource cs)</span><br><span class="line">&#123;</span><br><span class="line">    <span class="keyword">return</span> defineClass(name, b, off, len, getProtectionDomain(cs));</span><br><span class="line">&#125;</span><br><span class="line"></span><br><span class="line"><span class="keyword">protected</span> <span class="keyword">final</span> Class&lt;?&gt; defineClass(String name, java.nio.ByteBuffer b,</span><br><span class="line">                                     CodeSource cs)</span><br><span class="line">&#123;</span><br><span class="line">    <span class="keyword">return</span> defineClass(name, b, getProtectionDomain(cs));</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+<h3 id="AnnotationAwareAspectJAutoProxyCreator"><a href="#AnnotationAwareAspectJAutoProxyCreator" class="headerlink" title="AnnotationAwareAspectJAutoProxyCreator"></a>AnnotationAwareAspectJAutoProxyCreator</h3><p>在本示例中，创建代理的后置处理器就是 AnnotationAwareAspectJAutoProxyCreator，它继承自 AbstractAutoProxyCreator，AbstractAutoProxyCreator 实现了 BeanPostProcessor 接口。</p>
+<p>那么，<strong>它是什么时候，怎么加入到 beanFactory 中呢</strong>？</p>
+<p>PS: 显然，还有其他继承自 AbstractAutoProxyCreator 的后置处理器，暂时不谈。</p>
+<h4 id="BeanPostProcessor-的方法"><a href="#BeanPostProcessor-的方法" class="headerlink" title="BeanPostProcessor 的方法"></a>BeanPostProcessor 的方法</h4><p>postProcessBeforeInitialization 和 postProcessAfterInitialization 方法，前者什么都没做，后者在必要时对 Bean 进行包装。</p>
+<ul>
+<li><strong><code>AbstractAutoProxyCreator#postProcessAfterInitialization</code> 就是创建代理对象的入口。</strong></li>
+<li><strong>wrapIfNecessary 就是将 Bean 包装成代理 Bean 的入口方法</strong>。</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_">AbstractAutoProxyCreator</span> <span class="keyword">extends</span> <span class="title class_">ProxyProcessorSupport</span></span><br><span class="line">    <span class="keyword">implements</span> <span class="title class_">SmartInstantiationAwareBeanPostProcessor</span>, BeanFactoryAware &#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_">postProcessBeforeInitialization</span><span class="params">(Object bean, String beanName)</span> &#123;</span><br><span class="line">        <span class="comment">// 什么都没做</span></span><br><span class="line">        <span class="keyword">return</span> bean;</span><br><span class="line">    &#125;</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_">postProcessAfterInitialization</span><span class="params">(Object bean, String beanName)</span> <span class="keyword">throws</span> BeansException &#123;</span><br><span class="line">        <span class="keyword">if</span> (bean != <span class="literal">null</span>) &#123;</span><br><span class="line">            <span class="type">Object</span> <span class="variable">cacheKey</span> <span class="operator">=</span> getCacheKey(bean.getClass(), beanName);</span><br><span class="line">            <span class="keyword">if</span> (!<span class="built_in">this</span>.earlyProxyReferences.contains(cacheKey)) &#123;</span><br><span class="line">                <span class="comment">// 如有必要，将 bean 包装成代理对象</span></span><br><span class="line">                <span class="keyword">return</span> wrapIfNecessary(bean, beanName, cacheKey);</span><br><span class="line">            &#125;</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 class="comment">// ...</span></span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
 
-<p>方法中只是简单地将 <code>CodeSource</code> 类型的参数转换成 <code>ProtectionDomain</code> 类型，就调用 <code>ClassLoader</code> 的 <code>defineClass</code> 方法。</p>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">private</span> ProtectionDomain <span class="title function_">getProtectionDomain</span><span class="params">(CodeSource cs)</span> &#123;</span><br><span class="line">    <span class="comment">// 如果 CodeSource 为 null，直接返回 null</span></span><br><span class="line">    <span class="keyword">if</span> (cs == <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><br><span class="line">    <span class="type">ProtectionDomain</span> <span class="variable">pd</span> <span class="operator">=</span> <span class="literal">null</span>;</span><br><span class="line">    <span class="keyword">synchronized</span> (pdcache) &#123;</span><br><span class="line">        <span class="comment">// 先从 Map 缓存中获取 ProtectionDomain</span></span><br><span class="line">        pd = pdcache.get(cs);</span><br><span class="line">        <span class="keyword">if</span> (pd == <span class="literal">null</span>) &#123;</span><br><span class="line">            <span class="comment">// 从 CodeSource 中获取 PermissionCollection</span></span><br><span class="line">            <span class="type">PermissionCollection</span> <span class="variable">perms</span> <span class="operator">=</span> getPermissions(cs);</span><br><span class="line">            <span class="comment">// 缓存中没有，则创建一个 ProtectionDomain 并放入缓存</span></span><br><span class="line">            pd = <span class="keyword">new</span> <span class="title class_">ProtectionDomain</span>(cs, perms, <span class="built_in">this</span>, <span class="literal">null</span>);</span><br><span class="line">            pdcache.put(cs, pd);</span><br><span class="line">            <span class="keyword">if</span> (debug != <span class="literal">null</span>) &#123;</span><br><span class="line">                debug.println(<span class="string">&quot; getPermissions &quot;</span>+ pd);</span><br><span class="line">                debug.println(<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><span class="line">    <span class="keyword">return</span> pd;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+<h2 id="创建代理-Bean-的过程"><a href="#创建代理-Bean-的过程" class="headerlink" title="创建代理 Bean 的过程"></a>创建代理 Bean 的过程</h2><h3 id="按需包装成代理-wrapIfNecessary"><a href="#按需包装成代理-wrapIfNecessary" class="headerlink" title="按需包装成代理 wrapIfNecessary"></a>按需包装成代理 wrapIfNecessary</h3><figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">protected</span> Object <span class="title function_">wrapIfNecessary</span><span class="params">(Object bean, String beanName, Object cacheKey)</span> &#123;</span><br><span class="line">    <span class="comment">// 判断是否直接返回 bean</span></span><br><span class="line">    <span class="keyword">if</span> (beanName != <span class="literal">null</span> &amp;&amp; <span class="built_in">this</span>.targetSourcedBeans.contains(beanName)) &#123;</span><br><span class="line">        <span class="keyword">return</span> bean;</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="keyword">if</span> (Boolean.FALSE.equals(<span class="built_in">this</span>.advisedBeans.get(cacheKey))) &#123;</span><br><span class="line">        <span class="keyword">return</span> bean;</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="keyword">if</span> (isInfrastructureClass(bean.getClass()) || shouldSkip(bean.getClass(), beanName)) &#123;</span><br><span class="line">        <span class="built_in">this</span>.advisedBeans.put(cacheKey, Boolean.FALSE);</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="comment">// 如果有适用于当前 bean 的 advise 则为其创建代理</span></span><br><span class="line">    Object[] specificInterceptors = getAdvicesAndAdvisorsForBean(bean.getClass(), beanName, <span class="literal">null</span>);</span><br><span class="line">    <span class="keyword">if</span> (specificInterceptors != DO_NOT_PROXY) &#123;</span><br><span class="line">        <span class="built_in">this</span>.advisedBeans.put(cacheKey, Boolean.TRUE);</span><br><span class="line">        <span class="type">Object</span> <span class="variable">proxy</span> <span class="operator">=</span> createProxy(</span><br><span class="line">                bean.getClass(), beanName, specificInterceptors, <span class="keyword">new</span> <span class="title class_">SingletonTargetSource</span>(bean));</span><br><span class="line">        <span class="built_in">this</span>.proxyTypes.put(cacheKey, proxy.getClass());</span><br><span class="line">        <span class="keyword">return</span> proxy;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="built_in">this</span>.advisedBeans.put(cacheKey, Boolean.FALSE);</span><br><span class="line">    <span class="keyword">return</span> bean;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
 
-<h5 id="getPermissions"><a href="#getPermissions" class="headerlink" title="getPermissions"></a>getPermissions</h5><p>根据注释可知，此方法会返回给定 <code>CodeSource</code> 对象的权限。此方法由 <code>protect</code> 修饰，<code>AppClassLoader</code> 和 <code>URLClassLoader</code> 都有重写。当前 <code>ClassLoader</code> 是 <code>AppClassLoader</code>。</p>
-<p><code>AppClassLoader#getPermissions</code>，添加允许从类路径加载的任何类退出 VM的权限。</p>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">protected</span> PermissionCollection <span class="title function_">getPermissions</span><span class="params">(CodeSource codesource)</span></span><br><span class="line">&#123;</span><br><span class="line">    <span class="comment">// 调用父类 URLClassLoader 的 getPermissions</span></span><br><span class="line">    <span class="type">PermissionCollection</span> <span class="variable">perms</span> <span class="operator">=</span> <span class="built_in">super</span>.getPermissions(codesource);</span><br><span class="line">    <span class="comment">// 允许从类路径加载的任何类退出 VM的权限。</span></span><br><span class="line">    <span class="comment">// todo: 这是否自定义的类加载器加载的类，可能不能退出 VM。</span></span><br><span class="line">    perms.add(<span class="keyword">new</span> <span class="title class_">RuntimePermission</span>(<span class="string">&quot;exitVM&quot;</span>));</span><br><span class="line">    <span class="keyword">return</span> perms;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+<h3 id="AbstractAutoProxyCreator-视角，创建代理"><a href="#AbstractAutoProxyCreator-视角，创建代理" class="headerlink" title="AbstractAutoProxyCreator 视角，创建代理"></a>AbstractAutoProxyCreator 视角，创建代理</h3><p>AbstractAutoProxyCreator#createProxy，创建一个 ProxyFactory，将工作交给它处理。</p>
+<ol>
+<li>创建一个代理工厂 ProxyFactory</li>
+<li>设置相关信息</li>
+<li>通过 ProxyFactory 获取代理</li>
+</ol>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">protected</span> Object <span class="title function_">createProxy</span><span class="params">(</span></span><br><span class="line"><span class="params">        Class&lt;?&gt; beanClass, String beanName, Object[] specificInterceptors, TargetSource targetSource)</span> &#123;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">if</span> (<span class="built_in">this</span>.beanFactory <span class="keyword">instanceof</span> ConfigurableListableBeanFactory) &#123;</span><br><span class="line">        AutoProxyUtils.exposeTargetClass((ConfigurableListableBeanFactory) <span class="built_in">this</span>.beanFactory, beanName, beanClass);</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="type">ProxyFactory</span> <span class="variable">proxyFactory</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">ProxyFactory</span>();</span><br><span class="line">    proxyFactory.copyFrom(<span class="built_in">this</span>);</span><br><span class="line"></span><br><span class="line">    <span class="keyword">if</span> (!proxyFactory.isProxyTargetClass()) &#123;</span><br><span class="line">        <span class="keyword">if</span> (shouldProxyTargetClass(beanClass, beanName)) &#123;</span><br><span class="line">            proxyFactory.setProxyTargetClass(<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">            evaluateProxyInterfaces(beanClass, proxyFactory);</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    Advisor[] advisors = buildAdvisors(beanName, specificInterceptors);</span><br><span class="line">    proxyFactory.addAdvisors(advisors);</span><br><span class="line">    proxyFactory.setTargetSource(targetSource);</span><br><span class="line">    customizeProxyFactory(proxyFactory);</span><br><span class="line"></span><br><span class="line">    proxyFactory.setFrozen(<span class="built_in">this</span>.freezeProxy);</span><br><span class="line">    <span class="keyword">if</span> (advisorsPreFiltered()) &#123;</span><br><span class="line">        proxyFactory.setPreFiltered(<span class="literal">true</span>);</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">return</span> proxyFactory.getProxy(getProxyClassLoader());</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
 
-<p><code>SecureClassLoader#getPermissions</code>，添加一个读文件或读目录的权限。</p>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">protected</span> PermissionCollection <span class="title function_">getPermissions</span><span class="params">(CodeSource codesource)</span></span><br><span class="line">&#123;</span><br><span class="line">    <span class="comment">// 调用父类 SecureClassLoader 的 getPermissions</span></span><br><span class="line">    <span class="type">PermissionCollection</span> <span class="variable">perms</span> <span class="operator">=</span> <span class="built_in">super</span>.getPermissions(codesource);</span><br><span class="line"></span><br><span class="line">    <span class="type">URL</span> <span class="variable">url</span> <span class="operator">=</span> codesource.getLocation();</span><br><span class="line"></span><br><span class="line">    Permission p;</span><br><span class="line">    URLConnection urlConnection;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">try</span> &#123;</span><br><span class="line">        <span class="comment">// FileURLConnection 实例</span></span><br><span class="line">        urlConnection = url.openConnection();</span><br><span class="line">        <span class="comment">// 允许 read 的 FilePermission 实例</span></span><br><span class="line">        p = urlConnection.getPermission();</span><br><span class="line">    &#125; <span class="keyword">catch</span> (java.io.IOException ioe) &#123;</span><br><span class="line">        p = <span class="literal">null</span>;</span><br><span class="line">        urlConnection = <span class="literal">null</span>;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">if</span> (p <span class="keyword">instanceof</span> FilePermission) &#123;</span><br><span class="line">        <span class="comment">// if the permission has a separator char on the end,</span></span><br><span class="line">        <span class="comment">// it means the codebase is a directory, and we need</span></span><br><span class="line">        <span class="comment">// to add an additional permission to read recursively</span></span><br><span class="line">        <span class="comment">// 如果文件路径以文件分隔符结尾，表示目录，需要在末尾添加&quot;-&quot;改为递归读的权限</span></span><br><span class="line">        <span class="type">String</span> <span class="variable">path</span> <span class="operator">=</span> p.getName();</span><br><span class="line">        <span class="keyword">if</span> (path.endsWith(File.separator)) &#123;</span><br><span class="line">            path += <span class="string">&quot;-&quot;</span>;</span><br><span class="line">            p = <span class="keyword">new</span> <span class="title class_">FilePermission</span>(path, SecurityConstants.FILE_READ_ACTION);</span><br><span class="line">        &#125;</span><br><span class="line">    &#125; <span class="keyword">else</span> <span class="keyword">if</span> ((p == <span class="literal">null</span>) &amp;&amp; (url.getProtocol().equals(<span class="string">&quot;file&quot;</span>))) &#123;</span><br><span class="line">        <span class="type">String</span> <span class="variable">path</span> <span class="operator">=</span> url.getFile().replace(<span class="string">&#x27;/&#x27;</span>, File.separatorChar);</span><br><span class="line">        path = ParseUtil.decode(path);</span><br><span class="line">        <span class="keyword">if</span> (path.endsWith(File.separator))</span><br><span class="line">            path += <span class="string">&quot;-&quot;</span>;</span><br><span class="line">        p =  <span class="keyword">new</span> <span class="title class_">FilePermission</span>(path, SecurityConstants.FILE_READ_ACTION);</span><br><span class="line">    &#125; <span class="keyword">else</span> &#123;</span><br><span class="line">        <span class="comment">/**</span></span><br><span class="line"><span class="comment">         * Not loading from a &#x27;file:&#x27; URL so we want to give the class</span></span><br><span class="line"><span class="comment">         * permission to connect to and accept from the remote host</span></span><br><span class="line"><span class="comment">         * after we&#x27;ve made sure the host is the correct one and is valid.</span></span><br><span class="line"><span class="comment">         */</span></span><br><span class="line">        <span class="type">URL</span> <span class="variable">locUrl</span> <span class="operator">=</span> url;</span><br><span class="line">        <span class="keyword">if</span> (urlConnection <span class="keyword">instanceof</span> JarURLConnection) &#123;</span><br><span class="line">            locUrl = ((JarURLConnection)urlConnection).getJarFileURL();</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="type">String</span> <span class="variable">host</span> <span class="operator">=</span> locUrl.getHost();</span><br><span class="line">        <span class="keyword">if</span> (host != <span class="literal">null</span> &amp;&amp; (host.length() &gt; <span class="number">0</span>))</span><br><span class="line">            p = <span class="keyword">new</span> <span class="title class_">SocketPermission</span>(host,</span><br><span class="line">                                        SecurityConstants.SOCKET_CONNECT_ACCEPT_ACTION);</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// make sure the person that created this class loader</span></span><br><span class="line">    <span class="comment">// would have this permission</span></span><br><span class="line"></span><br><span class="line">    <span class="keyword">if</span> (p != <span class="literal">null</span>) &#123;</span><br><span class="line">        <span class="keyword">final</span> <span class="type">SecurityManager</span> <span class="variable">sm</span> <span class="operator">=</span> System.getSecurityManager();</span><br><span class="line">        <span class="keyword">if</span> (sm != <span class="literal">null</span>) &#123;</span><br><span class="line">            <span class="keyword">final</span> <span class="type">Permission</span> <span class="variable">fp</span> <span class="operator">=</span> p;</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> <span class="keyword">throws</span> SecurityException &#123;</span><br><span class="line">                    sm.checkPermission(fp);</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;, acc);</span><br><span class="line">        &#125;</span><br><span class="line">        perms.add(p);</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="keyword">return</span> perms;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+<h3 id="ProxyFactory-视角，获取代理"><a href="#ProxyFactory-视角，获取代理" class="headerlink" title="ProxyFactory 视角，获取代理"></a>ProxyFactory 视角，获取代理</h3><p>ProxyFactory#getProxy，创建一个 AopProxy 并委托它实现 getProxy。</p>
+<blockquote>
+<p>AopProxy 的含义与职责从字面上有点不好理解。</p>
+</blockquote>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> Object <span class="title function_">getProxy</span><span class="params">(ClassLoader classLoader)</span> &#123;</span><br><span class="line">    <span class="keyword">return</span> createAopProxy().getProxy(classLoader);</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
 
-<p><code>SecureClassLoader#getPermissions</code>，延迟设置权限，在创建 <code>ProtectionDomain</code> 时再设置。</p>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">protected</span> PermissionCollection <span class="title function_">getPermissions</span><span class="params">(CodeSource codesource)</span></span><br><span class="line">&#123;</span><br><span class="line">    <span class="comment">// 检查以确保类加载器已初始化。在 SecureClassLoader 构造器最后会用一个布尔变量表示加载器初始化成功。</span></span><br><span class="line">    <span class="comment">// 从代码上看，似乎只能保证 SecureClassLoader 的构造器方法已执行完毕？</span></span><br><span class="line">    check();</span><br><span class="line">    <span class="comment">// ProtectionDomain 延迟绑定，Permissions 继承 PermissionCollection 类。</span></span><br><span class="line">    <span class="keyword">return</span> <span class="keyword">new</span> <span class="title class_">Permissions</span>(); <span class="comment">// ProtectionDomain defers the binding</span></span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+<h4 id="ProxyFactor视角，创建-AopProxy"><a href="#ProxyFactor视角，创建-AopProxy" class="headerlink" title="ProxyFactor视角，创建 AopProxy"></a>ProxyFactor视角，创建 AopProxy</h4><p>ProxyFactory#createAopProxy，获取一个 AopProxyFactory 创建 AopProxy。</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">synchronized</span> AopProxy <span class="title function_">createAopProxy</span><span class="params">()</span> &#123;</span><br><span class="line">    <span class="keyword">if</span> (!<span class="built_in">this</span>.active) &#123;</span><br><span class="line">        activate();</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="comment">// 获取 AopProxy 工厂并创建一个 AopProxy</span></span><br><span class="line">    <span class="keyword">return</span> getAopProxyFactory().createAopProxy(<span class="built_in">this</span>);</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
 
-<h5 id="ProtectionDomain"><a href="#ProtectionDomain" class="headerlink" title="ProtectionDomain"></a>ProtectionDomain</h5><p><code>ProtectionDomain</code> 的相关构造器参数：</p>
+<h4 id="AopProxyFactory视角，创建-AopProxy"><a href="#AopProxyFactory视角，创建-AopProxy" class="headerlink" title="AopProxyFactory视角，创建 AopProxy"></a>AopProxyFactory视角，创建 AopProxy</h4><p>AopProxyFactory#createAopProxy。</p>
 <ul>
-<li><code>CodeSource</code></li>
-<li><code>PermissionCollection</code>，如果不为 <code>null</code>，会设置权限为只读，表示权限在使用过程中不再修改；同时检查是否需要设置拥有全部权限。</li>
-<li><code>ClassLoader</code></li>
-<li><code>Principal[]</code></li>
+<li>AopProxyFactory 有且仅有一个默认实现 DefaultAopProxyFactory。</li>
+<li>createAopProxy 方法会根据配置信息，返回具体实现：开箱即用的有 JdkDynamicAopProxy 或者 ObjenesisCglibAopProxy。</li>
 </ul>
-<p>这样看来，<code>SecureClassLoader</code> 为了定义类做的处理，就是简单地创建一些关于权限的对象，并保存了 <code>CodeSource-&gt;ProtectionDomain</code> 的映射作为缓存。</p>
-<h4 id="ClassLoader-defineClass"><a href="#ClassLoader-defineClass" class="headerlink" title="ClassLoader#defineClass"></a>ClassLoader#defineClass</h4><p>抽象类 <code>ClassLoader</code> 中最终用于定义类的 <code>native</code> 方法 <code>define0</code>，<code>define1</code>，<code>define2</code> 都是由 <code>private</code> 修饰的，<code>ClassLoader</code> 提供并重载了 <code>defineClass</code> 方法作为使用它们的入口，这些 <code>defineClass</code> 方法都由 <code>protect</code> <code>final</code> 修饰，这意味着这些方法只能被子类使用，并且不能被重写。</p>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">protected</span> <span class="keyword">final</span> Class&lt;?&gt; defineClass(String name, <span class="type">byte</span>[] b, <span class="type">int</span> off, <span class="type">int</span> len)</span><br><span class="line">    <span class="keyword">throws</span> ClassFormatError</span><br><span class="line">&#123;</span><br><span class="line">    <span class="keyword">return</span> defineClass(name, b, off, len, <span class="literal">null</span>);</span><br><span class="line">&#125;</span><br><span class="line"></span><br><span class="line"><span class="keyword">protected</span> <span class="keyword">final</span> Class&lt;?&gt; defineClass(String name, <span class="type">byte</span>[] b, <span class="type">int</span> off, <span class="type">int</span> len,</span><br><span class="line">                                     ProtectionDomain protectionDomain)</span><br><span class="line">    <span class="keyword">throws</span> ClassFormatError</span><br><span class="line">&#123;</span><br><span class="line">    protectionDomain = preDefineClass(name, protectionDomain);</span><br><span class="line">    <span class="type">String</span> <span class="variable">source</span> <span class="operator">=</span> defineClassSourceLocation(protectionDomain);</span><br><span class="line">    Class&lt;?&gt; c = defineClass1(name, b, off, len, protectionDomain, source);</span><br><span class="line">    postDefineClass(c, protectionDomain);</span><br><span class="line">    <span class="keyword">return</span> c;</span><br><span class="line">&#125;</span><br><span class="line"></span><br><span class="line"><span class="keyword">protected</span> <span class="keyword">final</span> Class&lt;?&gt; defineClass(String name, java.nio.ByteBuffer b,</span><br><span class="line">                                     ProtectionDomain protectionDomain)</span><br><span class="line">    <span class="keyword">throws</span> ClassFormatError</span><br><span class="line">&#123;</span><br><span class="line">    <span class="type">int</span> <span class="variable">len</span> <span class="operator">=</span> b.remaining();</span><br><span class="line"></span><br><span class="line">    <span class="comment">// Use byte[] if not a direct ByteBufer:</span></span><br><span class="line">    <span class="keyword">if</span> (!b.isDirect()) &#123;</span><br><span class="line">        <span class="keyword">if</span> (b.hasArray()) &#123;</span><br><span class="line">            <span class="keyword">return</span> defineClass(name, b.array(),</span><br><span class="line">                                b.position() + b.arrayOffset(), len,</span><br><span class="line">                                protectionDomain);</span><br><span class="line">        &#125; <span class="keyword">else</span> &#123;</span><br><span class="line">            <span class="comment">// no array, or read-only array</span></span><br><span class="line">            <span class="type">byte</span>[] tb = <span class="keyword">new</span> <span class="title class_">byte</span>[len];</span><br><span class="line">            b.get(tb);  <span class="comment">// get bytes out of byte buffer.</span></span><br><span class="line">            <span class="keyword">return</span> defineClass(name, tb, <span class="number">0</span>, len, protectionDomain);</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    protectionDomain = preDefineClass(name, protectionDomain);</span><br><span class="line">    <span class="type">String</span> <span class="variable">source</span> <span class="operator">=</span> defineClassSourceLocation(protectionDomain);</span><br><span class="line">    Class&lt;?&gt; c = defineClass2(name, b, b.position(), len, protectionDomain, source);</span><br><span class="line">    postDefineClass(c, protectionDomain);</span><br><span class="line">    <span class="keyword">return</span> c;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+<p>这里的处理，决定了 Spring AOP 会使用哪一种动态代理实现。比如 Spring AOP 默认使用 JDK 动态代理，如果目标对象实现了接口 Spring 会使用 JDK 动态代理，这些结论的依据就在于此。</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_">DefaultAopProxyFactory</span> <span class="keyword">implements</span> <span class="title class_">AopProxyFactory</span>, Serializable &#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> AopProxy <span class="title function_">createAopProxy</span><span class="params">(AdvisedSupport config)</span> <span class="keyword">throws</span> AopConfigException &#123;</span><br><span class="line">		<span class="keyword">if</span> (config.isOptimize() || config.isProxyTargetClass() || hasNoUserSuppliedProxyInterfaces(config)) &#123;</span><br><span class="line">			Class&lt;?&gt; targetClass = config.getTargetClass();</span><br><span class="line">			<span class="keyword">if</span> (targetClass == <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_">AopConfigException</span>(<span class="string">&quot;TargetSource cannot determine target class: &quot;</span> +</span><br><span class="line">						<span class="string">&quot;Either an interface or a target is required for proxy creation.&quot;</span>);</span><br><span class="line">			&#125;</span><br><span class="line">			<span class="keyword">if</span> (targetClass.isInterface() || Proxy.isProxyClass(targetClass)) &#123;</span><br><span class="line">				<span class="keyword">return</span> <span class="keyword">new</span> <span class="title class_">JdkDynamicAopProxy</span>(config);</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_">ObjenesisCglibAopProxy</span>(config);</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="keyword">new</span> <span class="title class_">JdkDynamicAopProxy</span>(config);</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>主要步骤：</p>
-<ol>
-<li><code>preDefineClass</code> 前置处理</li>
-<li><code>defineClassX</code></li>
-<li><code>postDefineClass</code> 后置处理</li>
-</ol>
-<h5 id="preDefineClass"><a href="#preDefineClass" class="headerlink" title="preDefineClass"></a>preDefineClass</h5><p>确定保护域 <code>ProtectionDomain</code>，并检查：</p>
-<ol>
-<li>未定义 <code>java.*</code> 类</li>
-<li>该类的签名者与包（<code>package</code>）中其余类的签名者相匹配</li>
-</ol>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">private</span> ProtectionDomain <span class="title function_">preDefineClass</span><span class="params">(String name,</span></span><br><span class="line"><span class="params">                                        ProtectionDomain pd)</span></span><br><span class="line">&#123;</span><br><span class="line">    <span class="comment">// 检查 name 为 null 或者有可能是有效的二进制名称</span></span><br><span class="line">    <span class="keyword">if</span> (!checkName(name))</span><br><span class="line">        <span class="keyword">throw</span> <span class="keyword">new</span> <span class="title class_">NoClassDefFoundError</span>(<span class="string">&quot;IllegalName: &quot;</span> + name);</span><br><span class="line"></span><br><span class="line">    <span class="comment">// Note:  Checking logic in java.lang.invoke.MemberName.checkForTypeAlias</span></span><br><span class="line">    <span class="comment">// relies on the fact that spoofing is impossible if a class has a name</span></span><br><span class="line">    <span class="comment">// of the form &quot;java.*&quot;</span></span><br><span class="line">    <span class="comment">// 如果 name 以 java. 开头，则抛出异常</span></span><br><span class="line">    <span class="keyword">if</span> ((name != <span class="literal">null</span>) &amp;&amp; name.startsWith(<span class="string">&quot;java.&quot;</span>)) &#123;</span><br><span class="line">        <span class="keyword">throw</span> <span class="keyword">new</span> <span class="title class_">SecurityException</span></span><br><span class="line">            (<span class="string">&quot;Prohibited package name: &quot;</span> +</span><br><span class="line">                name.substring(<span class="number">0</span>, name.lastIndexOf(<span class="string">&#x27;.&#x27;</span>)));</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="keyword">if</span> (pd == <span class="literal">null</span>) &#123;</span><br><span class="line">        <span class="comment">// 如果未传入 ProtectionDomain，取默认的 ProtectionDomain</span></span><br><span class="line">        pd = defaultDomain;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 存放了 package-&gt;certs 的 map 映射作为缓存，检查一个包内的 certs 都是一样的</span></span><br><span class="line">    <span class="comment">// todo: certs</span></span><br><span class="line">    <span class="keyword">if</span> (name != <span class="literal">null</span>) checkCerts(name, pd.getCodeSource());</span><br><span class="line"></span><br><span class="line">    <span class="keyword">return</span> pd;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+<h3 id="获取代理-AopProxy-getProxy"><a href="#获取代理-AopProxy-getProxy" class="headerlink" title="获取代理 AopProxy#getProxy"></a>获取代理 AopProxy#getProxy</h3><p>AopProxy 视角，获取代理。</p>
+<h4 id="JDK-动态代理"><a href="#JDK-动态代理" class="headerlink" title="JDK 动态代理"></a>JDK 动态代理</h4><p>JdkDynamicAopProxy。</p>
+<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> Object <span class="title function_">getProxy</span><span class="params">(ClassLoader classLoader)</span> &#123;</span><br><span class="line">    <span class="comment">// ...</span></span><br><span class="line">    <span class="comment">// JDK 动态代理，已经和 Spring 无关</span></span><br><span class="line">    <span class="keyword">return</span> Proxy.newProxyInstance(classLoader, proxiedInterfaces, <span class="built_in">this</span>);</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
 
-<h5 id="defineClassSourceLocation"><a href="#defineClassSourceLocation" class="headerlink" title="defineClassSourceLocation"></a>defineClassSourceLocation</h5><p>确定 <code>Class</code> 的 <code>CodeSource</code> 位置。</p>
-<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">private</span> String <span class="title function_">defineClassSourceLocation</span><span class="params">(ProtectionDomain pd)</span></span><br><span class="line">&#123;</span><br><span class="line">    <span class="type">CodeSource</span> <span class="variable">cs</span> <span class="operator">=</span> pd.getCodeSource();</span><br><span class="line">    <span class="type">String</span> <span class="variable">source</span> <span class="operator">=</span> <span class="literal">null</span>;</span><br><span class="line">    <span class="keyword">if</span> (cs != <span class="literal">null</span> &amp;&amp; cs.getLocation() != <span class="literal">null</span>) &#123;</span><br><span class="line">        source = cs.getLocation().toString();</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="keyword">return</span> source;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+<h5 id="InvocationHandler-的-invoke-方法"><a href="#InvocationHandler-的-invoke-方法" class="headerlink" title="InvocationHandler 的 invoke 方法"></a>InvocationHandler 的 invoke 方法</h5><p>根据 <code>Proxy.newProxyInstance(classLoader, proxiedInterfaces, this)</code> 可知，this 也就是 JdkDynamicAopProxy 同时也是一个 InvocationHandler，它必然实现了 invoke 方法，当代理对象调用方法时，就会进入到 invoke 方法中。</p>
+<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> Object <span class="title function_">invoke</span><span class="params">(Object proxy, Method method, Object[] args)</span> <span class="keyword">throws</span> Throwable &#123;</span><br><span class="line">    <span class="comment">// ...</span></span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
 
-<h5 id="defineClassX-方法"><a href="#defineClassX-方法" class="headerlink" title="defineClassX 方法"></a>defineClassX 方法</h5><p>这些 <code>native</code> 方法使用了 <code>name</code>，字节数据，<code>ProtectionDomain</code> 和 <code>source</code> 等参数，像黑盒一样，在虚拟机中定义了一个类。</p>
-<h5 id="postDefineClass"><a href="#postDefineClass" class="headerlink" title="postDefineClass"></a>postDefineClass</h5><p>在定义类后使用 <code>ProtectionDomain</code> 中的 <code>certs</code> 补充 <code>Class</code> 实例的 <code>signer</code> 信息，猜测在 <code>native</code> 方法 <code>defineClassX</code> 方法中，对 <code>ProtectionDomain</code> 做了一些修改。事实上，从代码上看，将 <code>CodeSource</code> 包装为 <code>ProtectionDomain</code> 传入后，除了 <code>defineClassX</code> 方法外，其他地方都是取出 <code>CodeSource</code> 使用。</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_">postDefineClass</span><span class="params">(Class&lt;?&gt; c, ProtectionDomain pd)</span></span><br><span class="line">&#123;</span><br><span class="line">    <span class="keyword">if</span> (pd.getCodeSource() != <span class="literal">null</span>) &#123;</span><br><span class="line">        <span class="comment">// 获取证书</span></span><br><span class="line">        Certificate certs[] = pd.getCodeSource().getCertificates();</span><br><span class="line">        <span class="keyword">if</span> (certs != <span class="literal">null</span>)</span><br><span class="line">            setSigners(c, certs);</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>]]></content>
-      <tags>
-        <tag>java</tag>
-        <tag>class loader</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>
+<h4 id="CGLib-动态代理"><a href="#CGLib-动态代理" class="headerlink" title="CGLib 动态代理"></a>CGLib 动态代理</h4><p>ObjenesisCglibAopProxy。</p>
+<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> Object <span class="title function_">getProxy</span><span class="params">(ClassLoader classLoader)</span> &#123;</span><br><span class="line">    <span class="comment">// ...</span></span><br><span class="line">    <span class="comment">// CGLib 动态代理，已经和 Spring 无关</span></span><br><span class="line">    <span class="type">Enhancer</span> <span class="variable">enhancer</span> <span class="operator">=</span> createEnhancer();</span><br><span class="line">    <span class="comment">// ...</span></span><br><span class="line">    <span class="keyword">return</span> createProxyClassAndInstance(enhancer, callbacks);</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
 
+<h5 id="为什么-Spring-中没有依赖-CGLib"><a href="#为什么-Spring-中没有依赖-CGLib" class="headerlink" title="为什么 Spring 中没有依赖 CGLib"></a>为什么 Spring 中没有依赖 CGLib</h5><p>你可能会注意到 Spring 中并没有直接依赖 CGLib，像 Enhancer 所在的包是 <code>org.springframework.cglib.proxy</code>。根据文档：</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>从 spring 3.2 开始，不再需要将 cglib 添加到类路径中，因为 cglib 类在 org.springframework 下重新打包并分布在 spring-core jar 中。 这样做既是为了方便，也是为了避免与使用不同版本 cglib 的其他项目发生潜在冲突。</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="创建代理前的准备"><a href="#创建代理前的准备" class="headerlink" title="创建代理前的准备"></a>创建代理前的准备</h2><p>在前面预留了一些问题，当初我在看网上的资料时就有这些困惑。</p>
+<h3 id="Bean-后置处理器-AspectJAwareAdvisorAutoProxyCreator-在什么时候，怎么加入到-beanFactory-中的？"><a href="#Bean-后置处理器-AspectJAwareAdvisorAutoProxyCreator-在什么时候，怎么加入到-beanFactory-中的？" class="headerlink" title="Bean 后置处理器 AspectJAwareAdvisorAutoProxyCreator 在什么时候，怎么加入到 beanFactory 中的？"></a>Bean 后置处理器 AspectJAwareAdvisorAutoProxyCreator 在什么时候，怎么加入到 beanFactory 中的？</h3><p>Debug 停留在 Spring 上下文刷新方法中的 finishBeanFactoryInitialization。</p>
+<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_">refresh</span><span class="params">()</span> <span class="keyword">throws</span> BeansException, IllegalStateException &#123;</span><br><span class="line">    <span class="comment">// ...</span></span><br><span class="line">    invokeBeanFactoryPostProcessors(beanFactory);</span><br><span class="line">    <span class="comment">// ...</span></span><br><span class="line">    finishBeanFactoryInitialization(beanFactory);</span><br><span class="line">    <span class="comment">// ...</span></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>从 beanFatory 的 beanDefinitionMap 可以观察到，配置类 AopConfig 中的 MathCalculator 和 LogAspect 的信息已经就位。</p>
+<img src="/2023/11/19/how-does-Spring-AOP-create-proxy-beans/Snipaste_2023-11-20_15-51-48.png" class="" title="初始化 beanFactory 时的 beanDefinitionMap">
 
-<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>
+<p>从 beanFactory 的 beanProcessor 可以观察到，AnnotationAwareAspectJAutoProxyCreator 已经就位。</p>
+<img src="/2023/11/19/how-does-Spring-AOP-create-proxy-beans/Snipaste_2023-11-20_15-56-15.png" class="" title="初始化 beanFactory 时的 beanPostProcessor">
 
-<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>
+<h4 id="EnableXXX-的魔法"><a href="#EnableXXX-的魔法" class="headerlink" title="@EnableXXX 的魔法"></a>@EnableXXX 的魔法</h4><p>注解 @EnableXXX 往往伴随着注解 @Import，在 invokeBeanFactoryPostProcessors(beanFactory) 中，工厂后置处理器 ConfigurationClassPostProcessor 会处理它。</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(AspectJAutoProxyRegistrar.class)</span></span><br><span class="line"><span class="keyword">public</span> <span class="meta">@interface</span> EnableAspectJAutoProxy &#123;</span><br><span class="line">    <span class="type">boolean</span> <span class="title function_">proxyTargetClass</span><span class="params">()</span> <span class="keyword">default</span> <span class="literal">false</span>;</span><br><span class="line">    <span class="type">boolean</span> <span class="title function_">exposeProxy</span><span class="params">()</span> <span class="keyword">default</span> <span class="literal">false</span>;</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>在 ConfigurationClassPostProcessor 的处理中，因为 AspectJAutoProxyRegistrar 实现了 ImportBeanDefinitionRegistrar，registerBeanDefinitions 方法会被调用，AnnotationAwareAspectJAutoProxyCreator 的 beanDefinition 随之被注册到 beanFactory，因 AnnotationAwareAspectJAutoProxyCreator 实现了 BeanPostProcessor 被提前创建。</p>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">class</span> <span class="title class_">AspectJAutoProxyRegistrar</span> <span class="keyword">implements</span> <span class="title class_">ImportBeanDefinitionRegistrar</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_">registerBeanDefinitions</span><span class="params">(</span></span><br><span class="line"><span class="params">            AnnotationMetadata importingClassMetadata, BeanDefinitionRegistry registry)</span> &#123;</span><br><span class="line">        <span class="comment">// 如有必要注册 AspectJAnnotationAutoProxyCreator</span></span><br><span class="line">        AopConfigUtils.registerAspectJAnnotationAutoProxyCreatorIfNecessary(registry);</span><br><span class="line">        <span class="comment">// 根据配置设置一些属性</span></span><br><span class="line">        <span class="type">AnnotationAttributes</span> <span class="variable">enableAspectJAutoProxy</span> <span class="operator">=</span></span><br><span class="line">                AnnotationConfigUtils.attributesFor(importingClassMetadata, EnableAspectJAutoProxy.class);</span><br><span class="line">        <span class="keyword">if</span> (enableAspectJAutoProxy.getBoolean(<span class="string">&quot;proxyTargetClass&quot;</span>)) &#123;</span><br><span class="line">            AopConfigUtils.forceAutoProxyCreatorToUseClassProxying(registry);</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="keyword">if</span> (enableAspectJAutoProxy.getBoolean(<span class="string">&quot;exposeProxy&quot;</span>)) &#123;</span><br><span class="line">            AopConfigUtils.forceAutoProxyCreatorToExposeProxy(registry);</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="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">
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> <span class="keyword">static</span> BeanDefinition <span class="title function_">registerAspectJAnnotationAutoProxyCreatorIfNecessary</span><span class="params">(BeanDefinitionRegistry registry, Object source)</span> &#123;</span><br><span class="line">    <span class="keyword">return</span> registerOrEscalateApcAsRequired(AnnotationAwareAspectJAutoProxyCreator.class, registry, source);</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<h3 id="切面类-LogAspect-的解析是在什么时候？"><a href="#切面类-LogAspect-的解析是在什么时候？" class="headerlink" title="切面类 LogAspect 的解析是在什么时候？"></a>切面类 LogAspect 的解析是在什么时候？</h3><p>进入创建 Bean 的方法 createBean 后，除了 doCreateBean，应额外留意 resolveBeforeInstantiation 方法。</p>
+<ol>
+<li><code>Object bean = resolveBeforeInstantiation(beanName, mbdToUse)</code>，在实例化前进行解析。</li>
+<li><code>Object beanInstance = doCreateBean(beanName, mbdToUse, args)</code>，创建 Bean 的具体过程。</li>
+</ol>
+<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">protected</span> Object <span class="title function_">createBean</span><span class="params">(String beanName, RootBeanDefinition mbd, Object[] args)</span> <span class="keyword">throws</span> BeanCreationException &#123; </span><br><span class="line">    <span class="comment">// ...</span></span><br><span class="line">    <span class="keyword">try</span> &#123;</span><br><span class="line">        <span class="type">Object</span> <span class="variable">bean</span> <span class="operator">=</span> resolveBeforeInstantiation(beanName, mbdToUse);</span><br><span class="line">        <span class="keyword">if</span> (bean != <span class="literal">null</span>) &#123;</span><br><span class="line">            <span class="keyword">return</span> bean;</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"></span><br><span class="line">    <span class="type">Object</span> <span class="variable">beanInstance</span> <span class="operator">=</span> doCreateBean(beanName, mbdToUse, args);</span><br><span class="line">    <span class="comment">// ...</span></span><br><span class="line">    <span class="keyword">return</span> beanInstance;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<h4 id="入口方法-resolveBeforeInstantiation"><a href="#入口方法-resolveBeforeInstantiation" class="headerlink" title="入口方法 resolveBeforeInstantiation"></a>入口方法 resolveBeforeInstantiation</h4><p>根据注释，该方法给 BeanPostProcessors 一个机会提前返回一个代理对象。在本示例中，返回 null，但是方法在第一次执行后已经提前解析得到 advisors 并缓存。</p>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">protected</span> Object <span class="title function_">resolveBeforeInstantiation</span><span class="params">(String beanName, RootBeanDefinition mbd)</span> &#123;</span><br><span class="line">    <span class="type">Object</span> <span class="variable">bean</span> <span class="operator">=</span> <span class="literal">null</span>;</span><br><span class="line">    <span class="keyword">if</span> (!Boolean.FALSE.equals(mbd.beforeInstantiationResolved)) &#123;</span><br><span class="line">        <span class="keyword">if</span> (!mbd.isSynthetic() &amp;&amp; hasInstantiationAwareBeanPostProcessors()) &#123;</span><br><span class="line">            Class&lt;?&gt; targetType = determineTargetType(beanName, mbd);</span><br><span class="line">            <span class="keyword">if</span> (targetType != <span class="literal">null</span>) &#123;</span><br><span class="line">                <span class="comment">// 注意，应用的是实例化前的处理</span></span><br><span class="line">                bean = applyBeanPostProcessorsBeforeInstantiation(targetType, beanName);</span><br><span class="line">                <span class="keyword">if</span> (bean != <span class="literal">null</span>) &#123;</span><br><span class="line">                    <span class="comment">// 注意，应用的是初始化后的处理</span></span><br><span class="line">                    bean = applyBeanPostProcessorsAfterInitialization(bean, beanName);</span><br><span class="line">                &#125;</span><br><span class="line">            &#125;</span><br><span class="line">        &#125;</span><br><span class="line">        mbd.beforeInstantiationResolved = (bean != <span class="literal">null</span>);</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></pre></td></tr></table></figure>
+
+<h4 id="InstantiationAwareBeanPostProcessor"><a href="#InstantiationAwareBeanPostProcessor" class="headerlink" title="InstantiationAwareBeanPostProcessor"></a>InstantiationAwareBeanPostProcessor</h4><p>应用 InstantiationAwareBeanPostProcessor 的 postProcessBeforeInstantiation。</p>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">protected</span> Object <span class="title function_">applyBeanPostProcessorsBeforeInstantiation</span><span class="params">(Class&lt;?&gt; beanClass, String beanName)</span> &#123;</span><br><span class="line">    <span class="keyword">for</span> (BeanPostProcessor bp : getBeanPostProcessors()) &#123;</span><br><span class="line">        <span class="keyword">if</span> (bp <span class="keyword">instanceof</span> InstantiationAwareBeanPostProcessor) &#123;</span><br><span class="line">            <span class="type">InstantiationAwareBeanPostProcessor</span> <span class="variable">ibp</span> <span class="operator">=</span> (InstantiationAwareBeanPostProcessor) bp;</span><br><span class="line">            <span class="comment">// 循环依次处理</span></span><br><span class="line">            <span class="type">Object</span> <span class="variable">result</span> <span class="operator">=</span> ibp.postProcessBeforeInstantiation(beanClass, beanName);</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">return</span> <span class="literal">null</span>;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<p>AnnotationAwareAspectJAutoProxyCreator 不仅仅是一个 BeanPostProcessor，它还是一个 InstantiationAwareBeanPostProcessor。</p>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> Object <span class="title function_">postProcessBeforeInstantiation</span><span class="params">(Class&lt;?&gt; beanClass, String beanName)</span> <span class="keyword">throws</span> BeansException &#123;</span><br><span class="line">    <span class="type">Object</span> <span class="variable">cacheKey</span> <span class="operator">=</span> getCacheKey(beanClass, beanName);</span><br><span class="line">    </span><br><span class="line">    <span class="keyword">if</span> (beanName == <span class="literal">null</span> || !<span class="built_in">this</span>.targetSourcedBeans.contains(beanName)) &#123;</span><br><span class="line">        <span class="keyword">if</span> (<span class="built_in">this</span>.advisedBeans.containsKey(cacheKey)) &#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">if</span> (isInfrastructureClass(beanClass) || shouldSkip(beanClass, beanName)) &#123;</span><br><span class="line">            <span class="built_in">this</span>.advisedBeans.put(cacheKey, Boolean.FALSE);</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">    </span><br><span class="line">    <span class="keyword">if</span> (beanName != <span class="literal">null</span>) &#123;</span><br><span class="line">        <span class="type">TargetSource</span> <span class="variable">targetSource</span> <span class="operator">=</span> getCustomTargetSource(beanClass, beanName);</span><br><span class="line">        <span class="keyword">if</span> (targetSource != <span class="literal">null</span>) &#123;</span><br><span class="line">            <span class="built_in">this</span>.targetSourcedBeans.add(beanName);</span><br><span class="line">            Object[] specificInterceptors = getAdvicesAndAdvisorsForBean(beanClass, beanName, targetSource);</span><br><span class="line">            <span class="type">Object</span> <span class="variable">proxy</span> <span class="operator">=</span> createProxy(beanClass, beanName, specificInterceptors, targetSource);</span><br><span class="line">            <span class="built_in">this</span>.proxyTypes.put(cacheKey, proxy.getClass());</span><br><span class="line">            <span class="keyword">return</span> proxy;</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>和 wrapIfNecessary 方法对比，容易发现两者有不少相似的处理。</p>
+<img src="/2023/11/19/how-does-Spring-AOP-create-proxy-beans/Snipaste_2023-11-20_21-33-34.png" class="" title="实例化前后创建代理的对比">
+
+<blockquote>
+<p><strong>注意：以下方法应注意是否被子类重写</strong>。</p>
+</blockquote>
+<p>org.springframework.aop.aspectj.autoproxy.AspectJAwareAdvisorAutoProxyCreator#shouldSkip</p>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">protected</span> <span class="type">boolean</span> <span class="title function_">shouldSkip</span><span class="params">(Class&lt;?&gt; beanClass, String beanName)</span> &#123;</span><br><span class="line">    <span class="comment">// 查找并缓存 advisors</span></span><br><span class="line">    List&lt;Advisor&gt; candidateAdvisors = findCandidateAdvisors();</span><br><span class="line">    <span class="comment">// ...</span></span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<p>org.springframework.aop.framework.autoproxy.AbstractAdvisorAutoProxyCreator#getAdvicesAndAdvisorsForBean</p>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">protected</span> Object[] getAdvicesAndAdvisorsForBean(Class&lt;?&gt; beanClass, String beanName, TargetSource targetSource) &#123;</span><br><span class="line">    List&lt;Advisor&gt; advisors = findEligibleAdvisors(beanClass, beanName);</span><br><span class="line">    <span class="comment">// ...</span></span><br><span class="line">&#125;</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>
-<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>
+<p>org.springframework.aop.framework.autoproxy.AbstractAdvisorAutoProxyCreator#findEligibleAdvisors</p>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">protected</span> List&lt;Advisor&gt; <span class="title function_">findEligibleAdvisors</span><span class="params">(Class&lt;?&gt; beanClass, String beanName)</span> &#123;</span><br><span class="line">    <span class="comment">// 查找并缓存 advisors</span></span><br><span class="line">    List&lt;Advisor&gt; candidateAdvisors = findCandidateAdvisors();</span><br><span class="line">    <span class="comment">// ...</span></span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<p>容易注意到两者在创建代理前，<strong>都会调用 findCandidateAdvisors 方法查找候选的 advisors</strong>，其实这也是我们想要找的对切面类的解析处理所在。</p>
+<h4 id="查找并缓存-advisors"><a href="#查找并缓存-advisors" class="headerlink" title="查找并缓存 advisors"></a>查找并缓存 advisors</h4><p>org.springframework.aop.aspectj.annotation.AnnotationAwareAspectJAutoProxyCreator#findCandidateAdvisors</p>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">protected</span> List&lt;Advisor&gt; <span class="title function_">findCandidateAdvisors</span><span class="params">()</span> &#123;</span><br><span class="line">    List&lt;Advisor&gt; advisors = <span class="built_in">super</span>.findCandidateAdvisors();</span><br><span class="line">    advisors.addAll(<span class="built_in">this</span>.aspectJAdvisorsBuilder.buildAspectJAdvisors());</span><br><span class="line">    <span class="keyword">return</span> advisors;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<p>org.springframework.aop.aspectj.annotation.BeanFactoryAspectJAdvisorsBuilder#buildAspectJAdvisors</p>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="keyword">public</span> List&lt;Advisor&gt; <span class="title function_">buildAspectJAdvisors</span><span class="params">()</span> &#123;</span><br><span class="line">    List&lt;String&gt; aspectNames = <span class="built_in">this</span>.aspectBeanNames;  </span><br><span class="line">    <span class="keyword">if</span> (aspectNames == <span class="literal">null</span>) &#123;</span><br><span class="line">        <span class="comment">// 第一次进入，没有缓存</span></span><br><span class="line">        <span class="keyword">synchronized</span> (<span class="built_in">this</span>) &#123;</span><br><span class="line">            aspectNames = <span class="built_in">this</span>.aspectBeanNames;</span><br><span class="line">            <span class="keyword">if</span> (aspectNames == <span class="literal">null</span>) &#123;</span><br><span class="line">                List&lt;Advisor&gt; advisors = <span class="keyword">new</span> <span class="title class_">LinkedList</span>&lt;Advisor&gt;();</span><br><span class="line">                aspectNames = <span class="keyword">new</span> <span class="title class_">LinkedList</span>&lt;String&gt;();</span><br><span class="line">                String[] beanNames = BeanFactoryUtils.beanNamesForTypeIncludingAncestors(</span><br><span class="line">                        <span class="built_in">this</span>.beanFactory, Object.class, <span class="literal">true</span>, <span class="literal">false</span>);</span><br><span class="line">                <span class="keyword">for</span> (String beanName : beanNames) &#123;</span><br><span class="line">                    <span class="comment">// ...</span></span><br><span class="line">                    <span class="comment">// 如果是切面，解析得到 advisors</span></span><br><span class="line">                    <span class="keyword">if</span> (<span class="built_in">this</span>.advisorFactory.isAspect(beanType)) &#123;</span><br><span class="line">                        aspectNames.add(beanName);</span><br><span class="line">                        <span class="comment">// ...</span></span><br><span class="line">                        <span class="keyword">if</span> (<span class="built_in">this</span>.beanFactory.isSingleton(beanName)) &#123;</span><br><span class="line">                            <span class="built_in">this</span>.advisorsCache.put(beanName, classAdvisors);</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>.aspectFactoryCache.put(beanName, factory);</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="built_in">this</span>.aspectBeanNames = aspectNames;</span><br><span class="line">                <span class="keyword">return</span> advisors;</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">if</span> (aspectNames.isEmpty()) &#123;</span><br><span class="line">        <span class="keyword">return</span> Collections.emptyList();</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="comment">// 以后进来读缓存</span></span><br><span class="line">    List&lt;Advisor&gt; advisors = <span class="keyword">new</span> <span class="title class_">LinkedList</span>&lt;Advisor&gt;();</span><br><span class="line">    <span class="keyword">for</span> (String aspectName : aspectNames) &#123;</span><br><span class="line">        List&lt;Advisor&gt; cachedAdvisors = <span class="built_in">this</span>.advisorsCache.get(aspectName);</span><br><span class="line">        <span class="keyword">if</span> (cachedAdvisors != <span class="literal">null</span>) &#123;</span><br><span class="line">            advisors.addAll(cachedAdvisors);</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="keyword">else</span> &#123;</span><br><span class="line">            <span class="type">MetadataAwareAspectInstanceFactory</span> <span class="variable">factory</span> <span class="operator">=</span> <span class="built_in">this</span>.aspectFactoryCache.get(aspectName);</span><br><span class="line">            advisors.addAll(<span class="built_in">this</span>.advisorFactory.getAdvisors(factory));</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="keyword">return</span> advisors;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<p>可以通过 <code>beanFactory-&gt;beanPostProcessors-&gt;aspectJAdvisorsBuilder-&gt;advisorsCache</code> 观察 advisors 的查找情况。</p>
+<img src="/2023/11/19/how-does-Spring-AOP-create-proxy-beans/Snipaste_2023-11-20_20-50-04.png" class="" title="观察 advisors">]]></content>
       <tags>
-        <tag>nginx</tag>
-        <tag>reverse proxy</tag>
+        <tag>java</tag>
+        <tag>spring</tag>
+        <tag>aop</tag>
       </tags>
   </entry>
   <entry>
@@ -2730,194 +2654,79 @@
       </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>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>
 
-<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>
-
-<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>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>
-<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>
-
-<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>
+<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="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>
+<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>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>
+<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>
 
-<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>
+<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>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>
+<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>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>
+<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">
 
-<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>
+<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>
 <thead>
 <tr>
-<th>参数</th>
-<th>说明</th>
+<th>正向代理</th>
+<th>反向代理</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>
+<td>客户端的代理</td>
+<td>服务端的代理</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>
+<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>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>
+<td>请求发向目标服务器</td>
+<td>请求发向代理</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>
+<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://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>
+<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>docker</tag>
         <tag>nginx</tag>
-        <tag>logrotate</tag>
+        <tag>reverse proxy</tag>
       </tags>
   </entry>
   <entry>
@@ -3158,6 +2967,197 @@
         <tag>spring</tag>
       </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>
+<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>
+<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>
+
+<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>
+
+<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>
+
+<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>Dubbo SPI 自适应拓展的工作原理</title>
     <url>/2023/11/29/how-does-Dubbo-SPI-adaptive-extension-works/</url>
@@ -3341,4 +3341,144 @@
         <tag>spi</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[<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>
+
+<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>
+<li><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></li>
+</ul>
+<h3 id="获取要导入的目标"><a href="#获取要导入的目标" class="headerlink" title="获取要导入的目标"></a>获取要导入的目标</h3><p>在 <code>doProcessConfigurationClass</code> 方法中处理配置类构建配置模型时，会调用 <code>processImports</code> 方法处理 <code>Import</code> 注解。在进入方法前，会调用 <code>getImports</code> 方法从 <code>sourceClass</code> 获取要导入的目标。</p>
+<blockquote>
+<p>注意：目标不仅仅来自直接标注在 <code>sourceClass</code> 上的 <code>Import</code> 注解，因为 <code>sourceClass</code> 上可能还有其他的注解，这些注解自身可能标注了 <code>Import</code> 注解，因此需要递归地遍历所有注解，找到所有的 <code>Import</code> 注解。</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">// 前后省略 @PropertySource、@ComponentScan、@ImportSource、@Bean 等注解的处理</span></span><br><span class="line">    <span class="comment">// 处理 Import 注解</span></span><br><span class="line">    processImports(configClass, sourceClass, getImports(sourceClass), <span class="literal">true</span>);</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<p><code>collectImports</code> 方法是一种常见的递归写法（深度优先遍历）。<code>imports</code> 存放要导入的目标，<code>visited</code> 存放已经访问过的 <code>sourceClass</code>。<code>sourceClass</code> 在入口处包装了一个普通的 <code>Class</code>，在递归的过程中包装的都是一个注解 <code>Class</code>。</p>
+<blockquote>
+<p>注意：这里还没有检测循环导入的情况并抛出异常，但 <code>visited</code> 保证了只会遍历一次。</p>
+</blockquote>
+<figure class="highlight java"><table><tr><td class="code"><pre><span class="line"><span class="comment">// 获取 Import 注解 value 中的 Class 对象，并包装为 SourceClass 返回</span></span><br><span class="line"><span class="keyword">private</span> Set&lt;SourceClass&gt; <span class="title function_">getImports</span><span class="params">(SourceClass sourceClass)</span> <span class="keyword">throws</span> IOException &#123;</span><br><span class="line">    Set&lt;SourceClass&gt; imports = <span class="keyword">new</span> <span class="title class_">LinkedHashSet</span>&lt;SourceClass&gt;();</span><br><span class="line">    Set&lt;SourceClass&gt; visited = <span class="keyword">new</span> <span class="title class_">LinkedHashSet</span>&lt;SourceClass&gt;();</span><br><span class="line">    collectImports(sourceClass, imports, visited);</span><br><span class="line">    <span class="keyword">return</span> imports;</span><br><span class="line">&#125;</span><br><span class="line"></span><br><span class="line"><span class="comment">// 递归地收集要导入的目标（包装为 SourceClass）</span></span><br><span class="line"><span class="keyword">private</span> <span class="keyword">void</span> <span class="title function_">collectImports</span><span class="params">(SourceClass sourceClass, Set&lt;SourceClass&gt; imports, Set&lt;SourceClass&gt; visited)</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">// 如果 sourceClass 尚未访问过</span></span><br><span class="line">    <span class="keyword">if</span> (visited.add(sourceClass)) &#123;</span><br><span class="line">        <span class="comment">// 遍历 sourceClass 上的注解</span></span><br><span class="line">        <span class="keyword">for</span> (SourceClass annotation : sourceClass.getAnnotations()) &#123;</span><br><span class="line">            <span class="type">String</span> <span class="variable">annName</span> <span class="operator">=</span> annotation.getMetadata().getClassName();</span><br><span class="line">            <span class="comment">// 只要注解的名称不是 java 开头或者不是 Import 注解</span></span><br><span class="line">            <span class="keyword">if</span> (!annName.startsWith(<span class="string">&quot;java&quot;</span>) &amp;&amp; !annName.equals(Import.class.getName())) &#123;</span><br><span class="line">                <span class="comment">// 将该注解作为 sourceClass 递归地调用</span></span><br><span class="line">                collectImports(annotation, imports, visited);</span><br><span class="line">            &#125;</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="comment">// 将 Import 注解的 value 的值转换为 sourceClass 加入 imports</span></span><br><span class="line">        imports.addAll(sourceClass.getAnnotationAttributes(Import.class.getName(), <span class="string">&quot;value&quot;</span>));</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<p>这时候，并不区分要导入的目标的 <code>Class</code> 有什么特别之处，<code>Import</code> 注解的语义，此时宽泛地说就是：“将 <code>value</code> 中的类导入”。但是显而易见，这样的方式不够灵活，因此才有了另外两种更有灵活性的导入方式：<code>ImportSelector</code> 和 <code>ImportBeanDefinitionRegistrar</code>，<code>Spring</code> 最终不会真的注册这两种类，而是注册它们“介绍”的类，相当于把确定导入什么类的工作委托给它们。</p>
+<h3 id="处理要导入的目标"><a href="#处理要导入的目标" class="headerlink" title="处理要导入的目标"></a>处理要导入的目标</h3><p><code>processImports</code> 方法是处理 <code>Import</code> 注解的核心方法，这里的处理逻辑就对应着 <code>Import</code> 注解的三种使用方式。主要步骤如下：</p>
+<ul>
+<li>检测要导入的候选者不为空</li>
+<li>判断是否要检测循环导入以及是否存在循环导入</li>
+<li>处理要导入的候选者<ul>
+<li>如果是 <code>ImportSelector</code> 类型，调用 <code>selectImports</code> 方法获取新的要导入的目标，递归调用 <code>processImports</code> 处理</li>
+<li>如果是 <code>ImportBeanDefinitionRegistrar</code> 类型，添加到配置模型 <code>configClass</code>（出口 <code>1</code>）</li>
+<li>如果是其他剩余情况，作为配置类处理（出口 <code>2</code>）</li>
+</ul>
+</li>
+</ul>
+<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_">processImports</span><span class="params">(ConfigurationClass configClass, SourceClass currentSourceClass,</span></span><br><span class="line"><span class="params">			Collection&lt;SourceClass&gt; importCandidates, <span class="type">boolean</span> checkForCircularImports)</span> <span class="keyword">throws</span> IOException &#123;</span><br><span class="line">    <span class="comment">// 如果要导入的目标为空，直接返回</span></span><br><span class="line">    <span class="keyword">if</span> (importCandidates.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="keyword">if</span> (checkForCircularImports &amp;&amp; isChainedImportOnStack(configClass)) &#123;</span><br><span class="line">        <span class="comment">// 如果要检查循环导入，且确实存在循环导入，则抛出异常</span></span><br><span class="line">        <span class="built_in">this</span>.problemReporter.error(<span class="keyword">new</span> <span class="title class_">CircularImportProblem</span>(configClass, <span class="built_in">this</span>.importStack));</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">// 将配置模型放入 importStack，用于检查循环导入</span></span><br><span class="line">        <span class="built_in">this</span>.importStack.push(configClass);</span><br><span class="line">        <span class="keyword">try</span> &#123;</span><br><span class="line">            <span class="comment">// 遍历每一个准备导入的目标</span></span><br><span class="line">            <span class="keyword">for</span> (SourceClass candidate : importCandidates) &#123;</span><br><span class="line">                <span class="comment">// 如果是 ImportSelector 类型，委托给它确定导入目标</span></span><br><span class="line">                <span class="keyword">if</span> (candidate.isAssignable(ImportSelector.class)) &#123;</span><br><span class="line">                    <span class="comment">// 加载类</span></span><br><span class="line">                    Class&lt;?&gt; candidateClass = candidate.loadClass();</span><br><span class="line">                    <span class="comment">// 实例化得到 ImportSelector 实例</span></span><br><span class="line">                    <span class="type">ImportSelector</span> <span class="variable">selector</span> <span class="operator">=</span> BeanUtils.instantiateClass(candidateClass, ImportSelector.class);</span><br><span class="line">                    <span class="comment">// 调用其 Aware 接口</span></span><br><span class="line">                    ParserStrategyUtils.invokeAwareMethods(</span><br><span class="line">                            selector, <span class="built_in">this</span>.environment, <span class="built_in">this</span>.resourceLoader, <span class="built_in">this</span>.registry);</span><br><span class="line">                    <span class="keyword">if</span> (<span class="built_in">this</span>.deferredImportSelectors != <span class="literal">null</span> &amp;&amp; selector <span class="keyword">instanceof</span> DeferredImportSelector) &#123;</span><br><span class="line">                        <span class="comment">// 如果是 DeferredImportSelector 类型，存入 deferredImportSelectors 推迟调用</span></span><br><span class="line">                        <span class="built_in">this</span>.deferredImportSelectors.add(</span><br><span class="line">                                <span class="keyword">new</span> <span class="title class_">DeferredImportSelectorHolder</span>(configClass, (DeferredImportSelector) selector));</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">// 调用 selectImports 方法，返回要导入的目标的全限定类名</span></span><br><span class="line">                        String[] importClassNames = selector.selectImports(currentSourceClass.getMetadata());</span><br><span class="line">                        <span class="comment">// 包装为 SourceClass</span></span><br><span class="line">                        Collection&lt;SourceClass&gt; importSourceClasses = asSourceClasses(importClassNames);</span><br><span class="line">                        <span class="comment">// 递归调用 processImports</span></span><br><span class="line">                        <span class="comment">// 从这里看，ImportSelector 本质上是更加灵活的 Import</span></span><br><span class="line">                        processImports(configClass, currentSourceClass, importSourceClasses, <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">// 如果是 ImportBeanDefinitionRegistrar 类型，委托给它注册额外的 BeanDefinitions</span></span><br><span class="line">                <span class="keyword">else</span> <span class="keyword">if</span> (candidate.isAssignable(ImportBeanDefinitionRegistrar.class)) &#123;</span><br><span class="line">                    <span class="comment">// 加载类</span></span><br><span class="line">                    Class&lt;?&gt; candidateClass = candidate.loadClass();</span><br><span class="line">                    <span class="comment">// 实例化得到 ImportBeanDefinitionRegistrar 实例</span></span><br><span class="line">                    <span class="type">ImportBeanDefinitionRegistrar</span> <span class="variable">registrar</span> <span class="operator">=</span></span><br><span class="line">                            BeanUtils.instantiateClass(candidateClass, ImportBeanDefinitionRegistrar.class);</span><br><span class="line">                    <span class="comment">// 调用其 Aware 接口</span></span><br><span class="line">                    ParserStrategyUtils.invokeAwareMethods(</span><br><span class="line">                            registrar, <span class="built_in">this</span>.environment, <span class="built_in">this</span>.resourceLoader, <span class="built_in">this</span>.registry);</span><br><span class="line">                    <span class="comment">// 添加到配置模型</span></span><br><span class="line">                    configClass.addImportBeanDefinitionRegistrar(registrar, currentSourceClass.getMetadata());</span><br><span class="line">                &#125;</span><br><span class="line">                <span class="comment">// 既不是 ImportSelector，也不是 ImportBeanDefinitionRegistrar 的其他剩余情况，将其视为被 Configuration 注解标注的配置类进行处理</span></span><br><span class="line">                <span class="keyword">else</span> &#123;</span><br><span class="line">                    <span class="built_in">this</span>.importStack.registerImport(</span><br><span class="line">                            currentSourceClass.getMetadata(), candidate.getMetadata().getClassName());</span><br><span class="line">                    <span class="comment">// asConfigClass 方法建立了 candidate importBy configClass 的关系</span></span><br><span class="line">                    processConfigurationClass(candidate.asConfigClass(configClass));</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> (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 process import candidates for configuration class [&quot;</span> +</span><br><span class="line">                    configClass.getMetadata().getClassName() + <span class="string">&quot;]&quot;</span>, ex);</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="keyword">finally</span> &#123;</span><br><span class="line">            <span class="comment">// pop 配置模型</span></span><br><span class="line">            <span class="built_in">this</span>.importStack.pop();</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="类型一：ImportSelector"><a href="#类型一：ImportSelector" class="headerlink" title="类型一：ImportSelector"></a>类型一：ImportSelector</h4><p>如果要导入的目标是 <code>ImportSelector</code> 类型，那么 <code>Spring</code> 将确定真正导入什么目标的工作委托给它，不导入目标本身，实际上只导入目标“介绍”的类。具体步骤是：</p>
+<ol>
+<li>先获取 <code>Class</code> 对象</li>
+<li>再实例化得到一个 <code>ImportSelector</code> 实例</li>
+<li>调用 <code>selectImports</code> 方法，该方法返回的是类的全限定名，这样就得到了真正要导入的目标</li>
+<li>再次递归调用 <code>processImports</code></li>
+</ol>
+<p><code>ImportSelector</code> 就像它名字的含义一样，本质上是一种导入选择器，是一种更加灵活的 <code>getImports</code> 方法。由于返回的目标可能属于三种情形中的任意一种，所以对这些目标的处理还是要回到 <code>processImports</code> 方法。可以说 <code>ImportSelector</code> 类型本身不是 <code>processImports</code> 方法的出口，它最终会转换为 <code>ImportBeanDefinitionRegistrar</code> 或其他剩余情况。</p>
+<p><code>ImportSelector</code> 灵活性的来源：</p>
+<ul>
+<li><code>selectImports</code> 的 <code>AnnotationMetadata</code> 参数，为它提供了根据注解信息返回要导入的目标的能力</li>
+<li><code>ImportSelector</code> 可以实现 <code>Aware</code> 接口，用以感知到一些容器级别的资源，如 <code>BeanFactory</code>，这为它提供了根据这些资源中的信息返回要导入的目标的能力</li>
+</ul>
+<h4 id="类型二：ImportBeanDefinitionRegistrar"><a href="#类型二：ImportBeanDefinitionRegistrar" class="headerlink" title="类型二：ImportBeanDefinitionRegistrar"></a>类型二：ImportBeanDefinitionRegistrar</h4><p>如果要导入的目标是 <code>ImportBeanDefinitionRegistrar</code>，它会和 <code>ImportSelector</code> 有些相似却又有所不同。<code>Spring</code> 同样将确定真正导入什么目标的工作委托给它，不导入目标本身，实际上只导入目标“介绍”的类。</p>
+<ol>
+<li>先获取 <code>Class</code> 对象</li>
+<li>再实例化得到一个 <code>ImportBeanDefinitionRegistrar</code> 实例</li>
+<li>添加到配置模型 <code>configClass</code> 的 <code>importBeanDefinitionRegistrars</code> 属性</li>
+</ol>
+<p><code>ImportBeanDefinitionRegistrar</code> 不像 <code>ImportSelector</code> 需要进一步处理，它本身就代表着一个返回出口，成为了配置模型的一部分。但是请注意，<code>registerBeanDefinitions</code> 方法此时并没有被调用。</p>
+<p><code>ImportBeanDefinitionRegistrar</code> 灵活性的来源：</p>
+<ul>
+<li><code>registerBeanDefinitions</code> 的 <code>AnnotationMetadata</code> 参数，为它提供了根据注解信息决定注册 <code>BeanDefinition</code> 的能力</li>
+<li><code>registerBeanDefinitions</code> 的 <code>BeanDefinitionRegistry</code> 参数，为它提供了根据 <code>BeanDefinitionRegistry</code> 中的信息决定注册 <code>BeanDefinition</code> 的能力</li>
+<li><code>ImportBeanDefinitionRegistrar</code> 可以实现 <code>Aware</code> 接口，用以感知到一些容器级别的资源，如 <code>BeanFactory</code>，这为它提供了根据这些资源中的信息返回要导入的目标的能力</li>
+</ul>
+<h4 id="类型三：其他剩余情况"><a href="#类型三：其他剩余情况" class="headerlink" title="类型三：其他剩余情况"></a>类型三：其他剩余情况</h4><p>如果要导入的目标属于既不是 <code>ImportSelector</code> 也不是 <code>ImportBeanDefinitionRegistrar</code> 的其他剩余情况，那么 <code>Spring</code> 将其视为被 <code>Configuration</code> 注解标注的配置类进行处理。这里的处理逻辑是，<code>Import</code> 注解导入的类可能不是一个普通的类，而是一个配置类，因此需要回到 <code>processConfigurationClass</code> 进行处理。<code>processConfigurationClass</code> 方法正是本文开头的 <code>doProcessConfigurationClass</code> 方法的调用方，这里有两个地方值得注意：</p>
+<ul>
+<li><code>Import</code> 注解产生的 <code>ConfigurationClass</code> 根据不同的情况需要合并或者被抛弃，显式声明比 Import 导入的优先级更高。</li>
+<li>其他剩余情况下，目标最终会转换为一个配置模型，添加到 <code>parser</code> 的 <code>configurationClasses</code> 属性。</li>
+</ul>
+<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">// 判断是否跳过处理</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">// 如果配置模型已经存在</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="keyword">if</span> (existingClass != <span class="literal">null</span>) &#123;</span><br><span class="line">        <span class="comment">// 如果新的配置模型代表的类，是 Import 导入的</span></span><br><span class="line">        <span class="keyword">if</span> (configClass.isImported()) &#123;</span><br><span class="line">            <span class="comment">// 如果已存在的配置模型也是 Import 导入的</span></span><br><span class="line">            <span class="keyword">if</span> (existingClass.isImported()) &#123;</span><br><span class="line">                <span class="comment">// 合并它们的来源</span></span><br><span class="line">                <span class="comment">// 比如一个类 A 既被 Config1 上的 Import 注解导入，也被 Config2 上的 Import 导入</span></span><br><span class="line">                existingClass.mergeImportedBy(configClass);</span><br><span class="line">            &#125;</span><br><span class="line">            <span class="comment">// 否则忽略新的因为 Import 导入而产生的配置模型</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">// 使用显式定义的代替 Import 导入的（显式定义的和 Import 导入的有什么不同吗）</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">// 先递归地处理配置类和它的父类，因为配合各种注解，可能引入更多的类</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">// 一个配置类，本身最终被解析成配置模型（配置模型在后续将会解析出 BeanDefinition）</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>
+
+<h3 id="DeferredImportSelector-的调用时机"><a href="#DeferredImportSelector-的调用时机" class="headerlink" title="DeferredImportSelector 的调用时机"></a>DeferredImportSelector 的调用时机</h3><p>在解析完每一批（注释中说“全部”）的配置类后，会统一调用 <code>DeferredImportSelector</code>。它作为一个标记接口推迟了 <code>selectImports</code> 的时机，打破了处理顺序的限制，在方法被调用时，可以得到更加完整的信息。注释中说“在选择导入的目标是 <code>@Conditional</code> 时，这个类型的选择器会很有用”，但是我不太理解，因为这个时候，处理配置类得到的信息尚未转换为 <code>ImportSelector</code> 可以感知到的信息，不像 <code>ImportBeanDefinitionRegistrar</code>，它被调用的时机在最后，也因此可以感知到更多的信息。</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="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">                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 class="comment">// 调用 DeferredImportSelectors</span></span><br><span class="line">    processDeferredImportSelectors();</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_">processDeferredImportSelectors</span><span class="params">()</span> &#123;</span><br><span class="line">    <span class="comment">// 获取处理这一批配置类获得的 DeferredImportSelectors</span></span><br><span class="line">    List&lt;DeferredImportSelectorHolder&gt; deferredImports = <span class="built_in">this</span>.deferredImportSelectors;</span><br><span class="line">    <span class="comment">// 清空</span></span><br><span class="line">    <span class="built_in">this</span>.deferredImportSelectors = <span class="literal">null</span>;</span><br><span class="line">    <span class="comment">// 排序</span></span><br><span class="line">    Collections.sort(deferredImports, DEFERRED_IMPORT_COMPARATOR);</span><br><span class="line">    <span class="comment">// 遍历</span></span><br><span class="line">    <span class="keyword">for</span> (DeferredImportSelectorHolder deferredImport : deferredImports) &#123;</span><br><span class="line">        <span class="type">ConfigurationClass</span> <span class="variable">configClass</span> <span class="operator">=</span> deferredImport.getConfigurationClass();</span><br><span class="line">        <span class="keyword">try</span> &#123;</span><br><span class="line">            <span class="comment">// 调用 selectImports 获取要导入的目标</span></span><br><span class="line">            String[] imports = deferredImport.getImportSelector().selectImports(configClass.getMetadata());</span><br><span class="line">            <span class="comment">// 调用 processImports 处理要导入的目标，这里不管循环导入？竟然是任由 StackOverFlow</span></span><br><span class="line">            processImports(configClass, asSourceClass(configClass), asSourceClasses(imports), <span class="literal">false</span>);</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 process import candidates for configuration class [&quot;</span> +</span><br><span class="line">                    configClass.getMetadata().getClassName() + <span class="string">&quot;]&quot;</span>, 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>
+
+<h3 id="ImportBeanDefinitionRegistrar-的调用时机"><a href="#ImportBeanDefinitionRegistrar-的调用时机" class="headerlink" title="ImportBeanDefinitionRegistrar 的调用时机"></a>ImportBeanDefinitionRegistrar 的调用时机</h3><p><code>ConfigurationClassPostProcessor</code> 在每次解析得到新的一批配置模型后，都会调用 <code>ConfigurationClassBeanDefinitionReader</code> 的 <code>loadBeanDefinitions</code> 方法加载 <code>BeanDefinition</code>，在这过程的最后会从 <code>ImportBeanDefinitionRegistrar</code> 加载 <code>BeanDefinition</code>。这代表在处理同一批配置类时，在 <code>registerBeanDefinitions</code> 方法中总是能感知到以其他方式注册到 <code>BeanDefinitionRegistry</code> 中的 <code>BeanDefinition</code>，不论书面定义的顺序如何。</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">// 遍历每一个配置模型</span></span><br><span class="line">    <span class="keyword">for</span> (ConfigurationClass configClass : configurationModel) &#123;</span><br><span class="line">        <span class="comment">// 从配置模型中加载 BeanDefinistion</span></span><br><span class="line">        loadBeanDefinitionsForConfigurationClass(configClass, trackedConditionEvaluator);</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_">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="comment">// 如果配置模型本身是导入的，为自身注册 BeanDefinition</span></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="comment">// 为 BeanMethod 加载 BeanDefinition（Bean 注解）</span></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">    <span class="comment">// 为 ImportResources 加载 BeanDefinition（ImportResource 注解）</span></span><br><span class="line">    loadBeanDefinitionsFromImportedResources(configClass.getImportedResources());</span><br><span class="line">    <span class="comment">// 从 ImportBeanDefinitionRegistrar 加载 BeanDefinition</span></span><br><span class="line">    loadBeanDefinitionsFromRegistrars(configClass.getImportBeanDefinitionRegistrars());</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_">loadBeanDefinitionsFromRegistrars</span><span class="params">(Map&lt;ImportBeanDefinitionRegistrar, AnnotationMetadata&gt; registrars)</span> &#123;</span><br><span class="line">    <span class="comment">// 遍历 ImportBeanDefinitionRegistrar 调用 registerBeanDefinitions 方法注册 BeanDefinition</span></span><br><span class="line">    <span class="keyword">for</span> (Map.Entry&lt;ImportBeanDefinitionRegistrar, AnnotationMetadata&gt; entry : registrars.entrySet()) &#123;</span><br><span class="line">        entry.getKey().registerBeanDefinitions(entry.getValue(), <span class="built_in">this</span>.registry);</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
+
+<h3 id="循环导入的检测"><a href="#循环导入的检测" class="headerlink" title="循环导入的检测"></a>循环导入的检测</h3><p>在处理导入的目标前将配置类放入 <code>importStack</code>，处理完毕移除。如果要导入的目标属于其他剩余情况时，注册被导入类-&gt;所有导入类集合的映射关系。</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_">processImports</span><span class="params">(ConfigurationClass configClass, SourceClass currentSourceClass,</span></span><br><span class="line"><span class="params">			Collection&lt;SourceClass&gt; importCandidates, <span class="type">boolean</span> checkForCircularImports)</span> <span class="keyword">throws</span> IOException &#123;</span><br><span class="line">    <span class="comment">// ...</span></span><br><span class="line">    <span class="keyword">if</span> (checkForCircularImports &amp;&amp; isChainedImportOnStack(configClass)) &#123;</span><br><span class="line">        <span class="comment">// 如果要检查循环导入，且确实存在循环导入，则抛出异常</span></span><br><span class="line">        <span class="built_in">this</span>.problemReporter.error(<span class="keyword">new</span> <span class="title class_">CircularImportProblem</span>(configClass, <span class="built_in">this</span>.importStack));</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">// 将配置模型放入 importStack，用于检查循环导入</span></span><br><span class="line">        <span class="built_in">this</span>.importStack.push(configClass);</span><br><span class="line">        <span class="keyword">try</span> &#123;</span><br><span class="line">            <span class="comment">// 遍历每一个准备导入的目标</span></span><br><span class="line">            <span class="keyword">for</span> (SourceClass candidate : importCandidates) &#123;</span><br><span class="line">                <span class="comment">// ...</span></span><br><span class="line">                <span class="keyword">else</span> &#123;</span><br><span class="line">                    <span class="comment">// 记录了被导入类-&gt;所有导入类集合的映射关系</span></span><br><span class="line">                    <span class="built_in">this</span>.importStack.registerImport(</span><br><span class="line">                            currentSourceClass.getMetadata(), candidate.getMetadata().getClassName());</span><br><span class="line">                    <span class="comment">// asConfigClass 方法建立了 candidate importBy configClass 的关系</span></span><br><span class="line">                    processConfigurationClass(candidate.asConfigClass(configClass));</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">        <span class="keyword">finally</span> &#123;</span><br><span class="line">            <span class="comment">// pop 配置模型</span></span><br><span class="line">            <span class="built_in">this</span>.importStack.pop();</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>检测是否发生循环导入。以当前类开始，循环向上查找最近一个导入自身的类，如果找到自身，说明发生循环导入。</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_">isChainedImportOnStack</span><span class="params">(ConfigurationClass configClass)</span> &#123;</span><br><span class="line">    <span class="comment">// 如果 importStack 已存在该配置模型</span></span><br><span class="line">    <span class="keyword">if</span> (<span class="built_in">this</span>.importStack.contains(configClass)) &#123;</span><br><span class="line">        <span class="type">String</span> <span class="variable">configClassName</span> <span class="operator">=</span> configClass.getMetadata().getClassName();</span><br><span class="line">        <span class="comment">// 获取最新一个导入 configClass 的类</span></span><br><span class="line">        <span class="type">AnnotationMetadata</span> <span class="variable">importingClass</span> <span class="operator">=</span> <span class="built_in">this</span>.importStack.getImportingClassFor(configClassName);</span><br><span class="line">        <span class="comment">// 循环查找导入类的最近一个导入类，如果找到了自身，表示发生循环导入</span></span><br><span class="line">        <span class="keyword">while</span> (importingClass != <span class="literal">null</span>) &#123;</span><br><span class="line">            <span class="keyword">if</span> (configClassName.equals(importingClass.getClassName())) &#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">            importingClass = <span class="built_in">this</span>.importStack.getImportingClassFor(importingClass.getClassName());</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">false</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><table>
+<thead>
+<tr>
+<th></th>
+<th><code>ImportSelector</code></th>
+<th><code>ImportBeanDefinitionRegistrar</code></th>
+<th>其他剩余情况</th>
+</tr>
+</thead>
+<tbody><tr>
+<td>灵活性</td>
+<td>中</td>
+<td>高</td>
+<td>低</td>
+</tr>
+<tr>
+<td>处理结果</td>
+<td></td>
+<td>转换为配置模型的一部分</td>
+<td>转换为一个配置模型</td>
+</tr>
+<tr>
+<td>方法调用时机</td>
+<td>立即（或解析配置类的最后）</td>
+<td>加载 <code>BeanDefinition</code> 的最后</td>
+<td></td>
+</tr>
+<tr>
+<td>方法的结果</td>
+<td>获取 Import 目标</td>
+<td>直接注册 <code>BeanDefinition</code></td>
+<td></td>
+</tr>
+</tbody></table>
+]]></content>
+      <tags>
+        <tag>java</tag>
+        <tag>spring</tag>
+      </tags>
+  </entry>
 </search>
diff --git a/tags/aop/index.html b/tags/aop/index.html
index 66dfc80f..c5ffff2a 100644
--- a/tags/aop/index.html
+++ b/tags/aop/index.html
@@ -152,7 +152,7 @@
   <nav class="site-state">
       <div class="site-state-item site-state-posts">
         <a href="/archives/">
-          <span class="site-state-item-count">28</span>
+          <span class="site-state-item-count">29</span>
           <span class="site-state-item-name">日志</span>
         </a>
       </div>
@@ -251,13 +251,13 @@ <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">74k</span>
+    <span title="站点总字数">77k</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">4:06</span>
+    <span title="站点阅读时长">4:18</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 a4029139..dbb8e7d3 100644
--- a/tags/bytecode/index.html
+++ b/tags/bytecode/index.html
@@ -152,7 +152,7 @@
   <nav class="site-state">
       <div class="site-state-item site-state-posts">
         <a href="/archives/">
-          <span class="site-state-item-count">28</span>
+          <span class="site-state-item-count">29</span>
           <span class="site-state-item-name">日志</span>
         </a>
       </div>
@@ -251,13 +251,13 @@ <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">74k</span>
+    <span title="站点总字数">77k</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">4:06</span>
+    <span title="站点阅读时长">4:18</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 86091008..57a580a9 100644
--- a/tags/cglib/index.html
+++ b/tags/cglib/index.html
@@ -152,7 +152,7 @@
   <nav class="site-state">
       <div class="site-state-item site-state-posts">
         <a href="/archives/">
-          <span class="site-state-item-count">28</span>
+          <span class="site-state-item-count">29</span>
           <span class="site-state-item-name">日志</span>
         </a>
       </div>
@@ -251,13 +251,13 @@ <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">74k</span>
+    <span title="站点总字数">77k</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">4:06</span>
+    <span title="站点阅读时长">4:18</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 5d56385e..c7e7fc89 100644
--- a/tags/clash/index.html
+++ b/tags/clash/index.html
@@ -152,7 +152,7 @@
   <nav class="site-state">
       <div class="site-state-item site-state-posts">
         <a href="/archives/">
-          <span class="site-state-item-count">28</span>
+          <span class="site-state-item-count">29</span>
           <span class="site-state-item-name">日志</span>
         </a>
       </div>
@@ -251,13 +251,13 @@ <h1 class="collection-header">clash
     <span class="post-meta-item-icon">
       <i class="fa fa-chart-line"></i>
     </span>
-    <span title="站点总字数">74k</span>
+    <span title="站点总字数">77k</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">4:06</span>
+    <span title="站点阅读时长">4:18</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 d584296b..e62a82b4 100644
--- a/tags/class-loader/index.html
+++ b/tags/class-loader/index.html
@@ -152,7 +152,7 @@
   <nav class="site-state">
       <div class="site-state-item site-state-posts">
         <a href="/archives/">
-          <span class="site-state-item-count">28</span>
+          <span class="site-state-item-count">29</span>
           <span class="site-state-item-name">日志</span>
         </a>
       </div>
@@ -251,13 +251,13 @@ <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">74k</span>
+    <span title="站点总字数">77k</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">4:06</span>
+    <span title="站点阅读时长">4:18</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 891006b2..02326cfb 100644
--- a/tags/distributed-lock/index.html
+++ b/tags/distributed-lock/index.html
@@ -152,7 +152,7 @@
   <nav class="site-state">
       <div class="site-state-item site-state-posts">
         <a href="/archives/">
-          <span class="site-state-item-count">28</span>
+          <span class="site-state-item-count">29</span>
           <span class="site-state-item-name">日志</span>
         </a>
       </div>
@@ -251,13 +251,13 @@ <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">74k</span>
+    <span title="站点总字数">77k</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">4:06</span>
+    <span title="站点阅读时长">4:18</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 fa40ffa5..c9ee3ef0 100644
--- a/tags/docker/index.html
+++ b/tags/docker/index.html
@@ -152,7 +152,7 @@
   <nav class="site-state">
       <div class="site-state-item site-state-posts">
         <a href="/archives/">
-          <span class="site-state-item-count">28</span>
+          <span class="site-state-item-count">29</span>
           <span class="site-state-item-name">日志</span>
         </a>
       </div>
@@ -294,13 +294,13 @@ <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">74k</span>
+    <span title="站点总字数">77k</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">4:06</span>
+    <span title="站点阅读时长">4:18</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 6b9775f6..c72988cf 100644
--- a/tags/dubbo/index.html
+++ b/tags/dubbo/index.html
@@ -152,7 +152,7 @@
   <nav class="site-state">
       <div class="site-state-item site-state-posts">
         <a href="/archives/">
-          <span class="site-state-item-count">28</span>
+          <span class="site-state-item-count">29</span>
           <span class="site-state-item-name">日志</span>
         </a>
       </div>
@@ -271,13 +271,13 @@ <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">74k</span>
+    <span title="站点总字数">77k</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">4:06</span>
+    <span title="站点阅读时长">4:18</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 de727ce6..e66f4f87 100644
--- a/tags/grafana/index.html
+++ b/tags/grafana/index.html
@@ -152,7 +152,7 @@
   <nav class="site-state">
       <div class="site-state-item site-state-posts">
         <a href="/archives/">
-          <span class="site-state-item-count">28</span>
+          <span class="site-state-item-count">29</span>
           <span class="site-state-item-name">日志</span>
         </a>
       </div>
@@ -251,13 +251,13 @@ <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">74k</span>
+    <span title="站点总字数">77k</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">4:06</span>
+    <span title="站点阅读时长">4:18</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 53542339..9f4bfe7f 100644
--- a/tags/index.html
+++ b/tags/index.html
@@ -27,7 +27,7 @@
 <meta property="og:description" content="Moralok&#39;s blog">
 <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="2023-12-04T08:27:13.956Z">
+<meta property="article:modified_time" content="2023-12-05T08:44:37.419Z">
 <meta property="article:author" content="Moralok">
 <meta name="twitter:card" content="summary">
 
@@ -155,7 +155,7 @@
   <nav class="site-state">
       <div class="site-state-item site-state-posts">
         <a href="/archives/">
-          <span class="site-state-item-count">28</span>
+          <span class="site-state-item-count">29</span>
           <span class="site-state-item-name">日志</span>
         </a>
       </div>
@@ -246,13 +246,13 @@ <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">74k</span>
+    <span title="站点总字数">77k</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">4:06</span>
+    <span title="站点阅读时长">4:18</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 9f3f303d..bfe375e6 100644
--- a/tags/java/index.html
+++ b/tags/java/index.html
@@ -152,7 +152,7 @@
   <nav class="site-state">
       <div class="site-state-item site-state-posts">
         <a href="/archives/">
-          <span class="site-state-item-count">28</span>
+          <span class="site-state-item-count">29</span>
           <span class="site-state-item-name">日志</span>
         </a>
       </div>
@@ -205,6 +205,26 @@ <h1 class="collection-header">java
       <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="2023-12-04T08:36:21+08:00"
+              content="2023-12-04">
+          12-04
+        </time>
+      </div>
+
+      <div class="post-title">
+          <a class="post-title-link" href="/2023/12/04/use-and-analysis-of-Import-annotation-in-Spring/" itemprop="url">
+            <span itemprop="name">Spring 中 @Import 注解的使用和源码分析</span>
+          </a>
+      </div>
+
+      
+    </header>
+  </article>
+
   <article itemscope itemtype="http://schema.org/Article">
     <header class="post-header">
       <div class="post-meta-container">
@@ -385,26 +405,6 @@ <h1 class="collection-header">java
     </header>
   </article>
 
-  <article itemscope itemtype="http://schema.org/Article">
-    <header class="post-header">
-      <div class="post-meta-container">
-        <time itemprop="dateCreated"
-              datetime="2023-11-03T15:57:47+08:00"
-              content="2023-11-03">
-          11-03
-        </time>
-      </div>
-
-      <div class="post-title">
-          <a class="post-title-link" href="/2023/11/03/testing-and-analysis-of-StringTable/" itemprop="url">
-            <span itemprop="name">字符串常量池的测试和分析</span>
-          </a>
-      </div>
-
-      
-    </header>
-  </article>
-
     </div>
   </div>
   
@@ -434,13 +434,13 @@ <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">74k</span>
+    <span title="站点总字数">77k</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">4:06</span>
+    <span title="站点阅读时长">4:18</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 312b0681..c4af4c7e 100644
--- a/tags/java/page/2/index.html
+++ b/tags/java/page/2/index.html
@@ -152,7 +152,7 @@
   <nav class="site-state">
       <div class="site-state-item site-state-posts">
         <a href="/archives/">
-          <span class="site-state-item-count">28</span>
+          <span class="site-state-item-count">29</span>
           <span class="site-state-item-name">日志</span>
         </a>
       </div>
@@ -205,6 +205,26 @@ <h1 class="collection-header">java
       <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="2023-11-03T15:57:47+08:00"
+              content="2023-11-03">
+          11-03
+        </time>
+      </div>
+
+      <div class="post-title">
+          <a class="post-title-link" href="/2023/11/03/testing-and-analysis-of-StringTable/" itemprop="url">
+            <span itemprop="name">字符串常量池的测试和分析</span>
+          </a>
+      </div>
+
+      
+    </header>
+  </article>
+
   <article itemscope itemtype="http://schema.org/Article">
     <header class="post-header">
       <div class="post-meta-container">
@@ -314,13 +334,13 @@ <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">74k</span>
+    <span title="站点总字数">77k</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">4:06</span>
+    <span title="站点阅读时长">4:18</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 b336d43e..63c6a0c3 100644
--- a/tags/jdk-proxy/index.html
+++ b/tags/jdk-proxy/index.html
@@ -152,7 +152,7 @@
   <nav class="site-state">
       <div class="site-state-item site-state-posts">
         <a href="/archives/">
-          <span class="site-state-item-count">28</span>
+          <span class="site-state-item-count">29</span>
           <span class="site-state-item-name">日志</span>
         </a>
       </div>
@@ -251,13 +251,13 @@ <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">74k</span>
+    <span title="站点总字数">77k</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">4:06</span>
+    <span title="站点阅读时长">4:18</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 cc4f5347..ea226050 100644
--- a/tags/jvm/index.html
+++ b/tags/jvm/index.html
@@ -152,7 +152,7 @@
   <nav class="site-state">
       <div class="site-state-item site-state-posts">
         <a href="/archives/">
-          <span class="site-state-item-count">28</span>
+          <span class="site-state-item-count">29</span>
           <span class="site-state-item-name">日志</span>
         </a>
       </div>
@@ -311,13 +311,13 @@ <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">74k</span>
+    <span title="站点总字数">77k</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">4:06</span>
+    <span title="站点阅读时长">4:18</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 9fa3cb1b..16579179 100644
--- a/tags/logrotate/index.html
+++ b/tags/logrotate/index.html
@@ -152,7 +152,7 @@
   <nav class="site-state">
       <div class="site-state-item site-state-posts">
         <a href="/archives/">
-          <span class="site-state-item-count">28</span>
+          <span class="site-state-item-count">29</span>
           <span class="site-state-item-name">日志</span>
         </a>
       </div>
@@ -251,13 +251,13 @@ <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">74k</span>
+    <span title="站点总字数">77k</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">4:06</span>
+    <span title="站点阅读时长">4:18</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 ceb44094..54ebc3e0 100644
--- a/tags/minikube/index.html
+++ b/tags/minikube/index.html
@@ -152,7 +152,7 @@
   <nav class="site-state">
       <div class="site-state-item site-state-posts">
         <a href="/archives/">
-          <span class="site-state-item-count">28</span>
+          <span class="site-state-item-count">29</span>
           <span class="site-state-item-name">日志</span>
         </a>
       </div>
@@ -251,13 +251,13 @@ <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">74k</span>
+    <span title="站点总字数">77k</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">4:06</span>
+    <span title="站点阅读时长">4:18</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 a8bb3b3d..9e162a71 100644
--- a/tags/nginx/index.html
+++ b/tags/nginx/index.html
@@ -152,7 +152,7 @@
   <nav class="site-state">
       <div class="site-state-item site-state-posts">
         <a href="/archives/">
-          <span class="site-state-item-count">28</span>
+          <span class="site-state-item-count">29</span>
           <span class="site-state-item-name">日志</span>
         </a>
       </div>
@@ -271,13 +271,13 @@ <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">74k</span>
+    <span title="站点总字数">77k</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">4:06</span>
+    <span title="站点阅读时长">4:18</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 a353195f..49f75ba2 100644
--- a/tags/openvpn/index.html
+++ b/tags/openvpn/index.html
@@ -152,7 +152,7 @@
   <nav class="site-state">
       <div class="site-state-item site-state-posts">
         <a href="/archives/">
-          <span class="site-state-item-count">28</span>
+          <span class="site-state-item-count">29</span>
           <span class="site-state-item-name">日志</span>
         </a>
       </div>
@@ -291,13 +291,13 @@ <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">74k</span>
+    <span title="站点总字数">77k</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">4:06</span>
+    <span title="站点阅读时长">4:18</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 e22d3b13..fdd2c607 100644
--- a/tags/prometheus/index.html
+++ b/tags/prometheus/index.html
@@ -152,7 +152,7 @@
   <nav class="site-state">
       <div class="site-state-item site-state-posts">
         <a href="/archives/">
-          <span class="site-state-item-count">28</span>
+          <span class="site-state-item-count">29</span>
           <span class="site-state-item-name">日志</span>
         </a>
       </div>
@@ -251,13 +251,13 @@ <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">74k</span>
+    <span title="站点总字数">77k</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">4:06</span>
+    <span title="站点阅读时长">4:18</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 63a2c774..3a819ead 100644
--- a/tags/proxy/index.html
+++ b/tags/proxy/index.html
@@ -152,7 +152,7 @@
   <nav class="site-state">
       <div class="site-state-item site-state-posts">
         <a href="/archives/">
-          <span class="site-state-item-count">28</span>
+          <span class="site-state-item-count">29</span>
           <span class="site-state-item-name">日志</span>
         </a>
       </div>
@@ -271,13 +271,13 @@ <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">74k</span>
+    <span title="站点总字数">77k</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">4:06</span>
+    <span title="站点阅读时长">4:18</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 d626cf0a..a954c5d2 100644
--- a/tags/redis/index.html
+++ b/tags/redis/index.html
@@ -152,7 +152,7 @@
   <nav class="site-state">
       <div class="site-state-item site-state-posts">
         <a href="/archives/">
-          <span class="site-state-item-count">28</span>
+          <span class="site-state-item-count">29</span>
           <span class="site-state-item-name">日志</span>
         </a>
       </div>
@@ -251,13 +251,13 @@ <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">74k</span>
+    <span title="站点总字数">77k</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">4:06</span>
+    <span title="站点阅读时长">4:18</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 196729c1..2a818cae 100644
--- a/tags/reverse-proxy/index.html
+++ b/tags/reverse-proxy/index.html
@@ -152,7 +152,7 @@
   <nav class="site-state">
       <div class="site-state-item site-state-posts">
         <a href="/archives/">
-          <span class="site-state-item-count">28</span>
+          <span class="site-state-item-count">29</span>
           <span class="site-state-item-name">日志</span>
         </a>
       </div>
@@ -251,13 +251,13 @@ <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">74k</span>
+    <span title="站点总字数">77k</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">4:06</span>
+    <span title="站点阅读时长">4:18</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 fac0bd7a..aa1b46e2 100644
--- a/tags/spi/index.html
+++ b/tags/spi/index.html
@@ -152,7 +152,7 @@
   <nav class="site-state">
       <div class="site-state-item site-state-posts">
         <a href="/archives/">
-          <span class="site-state-item-count">28</span>
+          <span class="site-state-item-count">29</span>
           <span class="site-state-item-name">日志</span>
         </a>
       </div>
@@ -271,13 +271,13 @@ <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">74k</span>
+    <span title="站点总字数">77k</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">4:06</span>
+    <span title="站点阅读时长">4:18</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 9010fec4..83463e52 100644
--- a/tags/spring/index.html
+++ b/tags/spring/index.html
@@ -152,7 +152,7 @@
   <nav class="site-state">
       <div class="site-state-item site-state-posts">
         <a href="/archives/">
-          <span class="site-state-item-count">28</span>
+          <span class="site-state-item-count">29</span>
           <span class="site-state-item-name">日志</span>
         </a>
       </div>
@@ -205,6 +205,26 @@ <h1 class="collection-header">spring
       <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="2023-12-04T08:36:21+08:00"
+              content="2023-12-04">
+          12-04
+        </time>
+      </div>
+
+      <div class="post-title">
+          <a class="post-title-link" href="/2023/12/04/use-and-analysis-of-Import-annotation-in-Spring/" itemprop="url">
+            <span itemprop="name">Spring 中 @Import 注解的使用和源码分析</span>
+          </a>
+      </div>
+
+      
+    </header>
+  </article>
+
   <article itemscope itemtype="http://schema.org/Article">
     <header class="post-header">
       <div class="post-meta-container">
@@ -331,13 +351,13 @@ <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">74k</span>
+    <span title="站点总字数">77k</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">4:06</span>
+    <span title="站点阅读时长">4:18</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 84ee5cc5..3ebf2c11 100644
--- a/tags/ssh/index.html
+++ b/tags/ssh/index.html
@@ -152,7 +152,7 @@
   <nav class="site-state">
       <div class="site-state-item site-state-posts">
         <a href="/archives/">
-          <span class="site-state-item-count">28</span>
+          <span class="site-state-item-count">29</span>
           <span class="site-state-item-name">日志</span>
         </a>
       </div>
@@ -251,13 +251,13 @@ <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">74k</span>
+    <span title="站点总字数">77k</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">4:06</span>
+    <span title="站点阅读时长">4:18</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 40063fe1..a2da572b 100644
--- a/tags/tmux/index.html
+++ b/tags/tmux/index.html
@@ -152,7 +152,7 @@
   <nav class="site-state">
       <div class="site-state-item site-state-posts">
         <a href="/archives/">
-          <span class="site-state-item-count">28</span>
+          <span class="site-state-item-count">29</span>
           <span class="site-state-item-name">日志</span>
         </a>
       </div>
@@ -251,13 +251,13 @@ <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">74k</span>
+    <span title="站点总字数">77k</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">4:06</span>
+    <span title="站点阅读时长">4:18</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 0f9374a6..4f6d7b9b 100644
--- a/tags/ubuntu/index.html
+++ b/tags/ubuntu/index.html
@@ -152,7 +152,7 @@
   <nav class="site-state">
       <div class="site-state-item site-state-posts">
         <a href="/archives/">
-          <span class="site-state-item-count">28</span>
+          <span class="site-state-item-count">29</span>
           <span class="site-state-item-name">日志</span>
         </a>
       </div>
@@ -251,13 +251,13 @@ <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">74k</span>
+    <span title="站点总字数">77k</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">4:06</span>
+    <span title="站点阅读时长">4:18</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