jna.loadLibrary cannot find native library file

Question

I have created own jar with native library wrapper. The structure of resulting jar is:

library.jar
 |- com (there are my .java classes)
 |- libs (there is the native - libmylib.so)
 |- META-INF

I load native lib as follows:

MyLibClass instance = (MyLibClass) Native.loadLibrary("mylib", MyLibClass.class);

Now I want to add this library in other project and use it. But when I create an instance of MyLibClass I receive an error:

Exception in thread "main" java.lang.UnsatisfiedLinkError: Unable to load library 'mylib':
libmylib.so: cannot open shared object file: No such file or directory

How should i fix this problem?

Answer 1

I've done that using static Loader class as follows:

static class Loader {

    private Loader() {
    }

    static String getNative() {
        InputStream in = null;
        FileOutputStream fos = null;
        File fileOut = null;
        System.setProperty("jna.library.path",
                System.getProperty("java.io.tmpdir"));

        in = Loader.class.getResourceAsStream(
                        "/libs/libmylib.so");

        if (in != null) {
            try {
                fileOut = File.createTempFile("mylib", ".so");
                fileOut.deleteOnExit();

                fos = new FileOutputStream(fileOut);

                int count;
                byte[] buf = new byte[1024];

                while ((count = in.read(buf, 0, buf.length)) > 0) {
                    fos.write(buf, 0, count);
                }

            } catch (IOException ex) {
                throw new Error("Failed to create temporary file: " + ex);
            } finally {
                try {
                    in.close();
                } catch (IOException ex) {
                }

                if (fos != null) {
                    try {
                        fos.close();
                    } catch (IOException ex) {
                    }
                }

                return fileOut.getAbsolutePath();
            }
        } else {
            throw new Error("Couldn't open native library file");
        }
    }
}

There I load library file from resources and copy its contents to the temporary dir. As you can see before doing that I set jna.library.path to temp folder, so JNA will search libraries there.

Futher I'm loading library as this:

MyLibClass instance = (MyLibClass) Native.loadLibrary(Loader.getNative(), MyLibClass.class);