JarUtils

public class JarUtils {
    public static boolean extractFromJar(final String fileName, final String dest, final JarFile jar) throws IOException {
        final File file = new File(dest);
        if (file.isDirectory()) {
            file.mkdir();
            return false;
        }
        if (!file.exists()) {
            file.getParentFile().mkdirs();
        }
        final Enumeration<JarEntry> e = jar.entries();
        while (e.hasMoreElements()) {
            final JarEntry je = e.nextElement();
            //System.out.println(je.getName());
            if (!je.getName().contains(fileName)) {
                continue;
            }
            final InputStream in = new BufferedInputStream(jar.getInputStream(je));
            final OutputStream out = new BufferedOutputStream(new FileOutputStream(file));
            copyInputStream(in, out);
            jar.close();
            return true;
        }
        jar.close();
        return false;
    }

    private final static void copyInputStream(final InputStream in, final OutputStream out) throws IOException {
        try {
            final byte[] buff = new byte[4096];
            int n;
            while ((n = in.read(buff)) > 0) {
                out.write(buff, 0, n);
            }
        } finally {
            out.flush();
            out.close();
            in.close();
        }
    }

    public static void addClassPath(final File file) throws IOException{
        addClassPath(getJarUrl(file));
    }

    public static void addClassPath(final URL url) throws IOException {
        final URLClassLoader sysloader = (URLClassLoader) ClassLoader.getSystemClassLoader();
        final Class<URLClassLoader> sysclass = URLClassLoader.class;
        try {
            final Method method = sysclass.getDeclaredMethod("addURL", new Class[] { URL.class });
            method.setAccessible(true);
            method.invoke(sysloader, new Object[] { url });
        } catch (final Throwable t) {
            t.printStackTrace();
            throw new IOException("Error adding " + url + " to system classloader");
        }
    }

    public static URL getJarUrl(final File file) throws IOException {
        return new URL("jar:" + file.toURI().toURL().toExternalForm() + "!/");
    }
}