Loading JNI lib on Mac OS X?

Question

Background

So I am attempting to load a jnilib (specifically JOGL) into Java on Mac OS X at runtime. I have been following along the relevant Stack Overflow questions:

• Maven and the JOGL Library
• Loading DLL in Java - Eclipse - JNI
• How to make a jar file that include all jar files

The end goal for me is to package platform specific JOGL files into a JAR and unzip them into a temp directory and load them at start-up. I worked my problem back to simply attempting to load JOGL using hard-coded paths:

    File f = new File("/var/folders/+n/+nfb8NHsHiSpEh6AHMCyvE+++TI/-Tmp-/libjogl.jnilib");
    System.load(f.toString());
    f = new File ("/var/folders/+n/+nfb8NHsHiSpEh6AHMCyvE+++TI/-Tmp-/libjogl_awt.jnilib");
    System.load(f.toString());

I get the following exception when attempting to use the JOGL API:

    Exception in thread "main" java.lang.UnsatisfiedLinkError: no jogl in java.library.path

But when I specify java.library.path by adding the following JVM option:

    -Djava.library.path="/var/folders/+n/+nfb8NHsHiSpEh6AHMCyvE+++TI/-Tmp-/" 

Everything works fine.

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Question

Is it possible use System.load (or some other variant) on Mac OS X as a replacement for -Djava.library.path that is invoked at runtime?

Alta

Answer 1

Jogl always tries to auto-load all dependent libraries. To avoid this, there should be a NativeLibLoader class where you can call disableLoading() before you load the libraries yourself via the System.load()

Abbottson

Sweet! Thanks for this, calling NativeLibLoader.disableLoading() before manually loading the libraries worked brilliantly. – Alta

Answer 2

You don't have to provide the java.library.path at startup. You can programmatically set it with

System.setProperty("java.library.path", "/var/folder/bla/foo/bar/");

I don't know if System.load() will work somehow without this library path.

Guayule

Thanks for the suggestion. However in my experience setting the 'java.library.path' at run time did not have any effect. I think this may be for similar reasons as to why you can not change the classpath at run time - #272006 – Alta

Then you might have had another problem with a dependent library. Setting the lib path at runtime works perfectly fine, I used to load my libraries just like that. – Guayule

That's not quite true, there is a way to force re-initializing classloader with the new lib.path. – Gunslinger

Do something like this: System.setProperty( "java.library.path", newPath); Field fieldSysPath = ClassLoader.class.getDeclaredField("sys_paths"); fieldSysPath.setAccessible(true); fieldSysPath.set(null, null); – Gunslinger

Answer 3

System.load(...) takes libraryName as argument. It doesn't take path to library as argument. JVM searches for a library with specified name in the list of paths specified in -Djava.library.path;

Here there is nothing specific to Mac OS X. It searches for libraries in the same way on all operating systems.

Realtor

that is wrong actually, System.load() will take the complete file name and System.loadLibrary will take the lib name – Trajan

I think loading jnilib is mac specific (it is in my case). I have it working on Linux (.so), in mac after compilation jnilib does not load. I use mvn jetty:deploy-war -Djava.library.path=/path/to/jnilib. I have even used System.setProperty("mylib.systemclassloader", "false"); so that it would run in a servlet environment (it disables automatic loading of that library). What might be the cause? – Oscular