[SOLVED] Load .so file from a jar

Load .so file from a jar

I made a library in C and I call it from Java with JNI so I have my package and a lib folder with the libMYLIB.so file. I recall it from Java writing:

static{
    System.loadLibrary("MYLIB");
}

If I execute it with the option -Djava.library.path=../lib it works well.

But I need to create a jar file with my package and lib folder; so I made it and import in a more complex project.

In the big project the classes of my package are seen and used but at run-time Java fails to load MYLIB.

Is it possible to tell Java to load it from jar file? How?

Solution

First, we need to make sure the JAR file is in the class path. Then, here is a simple way of loading the library, assuming it is found under /com/example/libMYLIB.so in the JAR:

    InputStream is = ClassLoader.class.getResourceAsStream("/com/example/libMYLIB.so");
    File file = File.createTempFile("lib", ".so");
    OutputStream os = new FileOutputStream(file);
    byte[] buffer = new byte[1024];
    int length;
    while ((length = is.read(buffer)) != -1) {
        os.write(buffer, 0, length);
    }
    is.close();
    os.close();

    System.load(file.getAbsolutePath());
    file.deleteOnExit();

But this glosses over a lot of corner cases and portability issues that are covered by JavaCPP inside the Loader class.