Java Project with native libraries for different platforms

Question

I have a java project that uses JOGL and therefore needs to include different native libraries for different platforms. Now I want to set up the eclipse project to automatically chose the correct libraries. In the .classpath file you can specify one native location:

<classpathentry kind="lib" path="lib/jogl/jar/jogl.all.jar">
    <attributes>
        <attribute name="org.eclipse.jdt.launching.CLASSPATH_ATTR_LIBRARY_PATH_ENTRY" value="de.yogularm.desktop/lib/jogl/windows-amd64"/>
    </attributes>
</classpathentry>

If multiply classpathentries specify a native location, Eclipse also tries to load the libraries for other platforms and fails.

How can I make eclipse chose the directory? I want to share the project and make setup for further developers as easy as possible.

Answer 1

You can create several .classpath files (.classpath_Windows, .classpath_Linux etc.) and then create symbolic link to required version (Win/Lin/Mac) named ".classpath"
The problem will appear whan you want to change any entry inside any .classpath_XXXXXXX - then you will have to update other .classpath files.

Answer 2

Eclipse lacks the feature you want. So, you can do it from Java.

Instead of calling System.loadLibrary , call System.load . This requires you to write code to calculate the correct pathname based on the current platform. You'll need to use -D to pass a value in to say what the current platform is, or read it from a file.

This removes java.library.path from the equation.

If your JNI library has dependencies, you will also need to set PATH, LD_LIBRARY_PATH, or DYLD_LIBRARY_PATH. Unless you take the further step of looking at https://github.com/bimargulies/jni-origin-testbed . For Windows, however, the necessary machinations with the delay-loader aren't in there.

Answer 3

I may be wrong, but I think the native libraries are things like DLLs, shared objects, etc., and don't go on the classpath at all. Each environment will have something like a PATH variable or the like, which will need to include the native libraries. The user may have to some configuration (either within Eclipse, or via environment variables).

Answer 4

Libraries are not searched within the classpath, the system PATH and the property java.library.path .

In your case may be a custom ClassLoader implementation, especially the findLibrary(..) and loadLibrary(..) methods. This would allow to select an appropriate library based on the detected OS.