To debug jar loading make sure you ...
- built the current version of JNativeLibLoader's source code.
- have a project depending on the project of which jar loading you want to debug. Start debugging from a main function of the depending project.
- opened the source code of all three projects in Netbeans.
- deactivated “compile on save” in Netbeans for the three projects.
To deactivate “compile on save”:
Rightclick the project name -> Properties -> Build -> Compiling. Select "Disable".
Do this for JNativeLibLoader' and your own project.
If “compile on save” is activated (which is the default case), Netbeans shows following hint in Run Output:
Running NetBeans Compile On Save execution. Phase execution is skipped and output directories of dependency projects (with Compile on Save turned on) will be used instead of their jar artifacts.
That will also sometimes prevent the following error:
Exception in thread "main" java.lang.UnsatisfiedLinkError: Can't load library: <Project path>/natives/linux-amd64/<native lib name>
Why?
Netbeans caches the generated .class file before they are copied into the JAR.
NativeLibLoader fetches the path of the .class file of “MyClass” from the JVM within the load() function.
If “compile on save is activated” ...
- Netbeans loads the .class files of it's cache instead of the .class files from the JAR file when you run or debug your project.
- NativeLibLoader will then only get the path of the .class file in the Netbeans cache.
NativeLibLoader can sometimes also load the native libs in the project path. But the aim was to debug the JAR loading.
https://github.com/KeepSafe/ReLinker
https://github.com/scijava/native-lib-loader
https://github.com/LWJGL/lwjgl3
For more information click here.
An Alternative to NativeParsing which would also allow cyclic dependencies:
Implement native lib loading itself via JNI to the OS specific functions.
Linux: dlopen(). Would also allow lazy binding.
Windows: LoadLibraryExA(). Allows to set dependency search path explicitly.
Possible inspiration
https://javadoc.lwjgl.org/org/lwjgl/system/Library.html#loadNative(java.lang.Class,java.lang.String,java.lang.String)
https://javadoc.lwjgl.org/org/lwjgl/system/windows/WinBase.html
https://github.com/jnr/jnr-ffi