import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.lang.reflect.Type;
import java.net.URL;
import java.util.jar.Attributes;
import java.util.jar.JarFile;
import java.util.jar.Manifest;

public class JarAuslesen {

	@SuppressWarnings("unused")
	private InputStream readStreamFromJar(String pkgname, String fname) {
		String res = "/" + pkgname.replace('.', '/') + "/" + fname;
		Class<?> clazz = readClassFromJar(pkgname, fname);
		return clazz.getResourceAsStream(res);
	}

	private Class<?> readClassFromJar(String pkgname, String fname) {
		Class<?> clazz = null;
		ClassLoader cl = getClass().getClassLoader();
		// hier wird die *.jar ermittelt
		URL url = cl.getResource(pkgname + "/" + fname);

		// Manifest ermitteln
		File f = new File(url.getFile());
		JarFile jf;
		Manifest manifest = null;
		try {
			jf = new JarFile(f);
			manifest = jf.getManifest();
		} catch (IOException e) {
			System.err.println("Ein-Ausgabe-Fehler bei Manifestermittlung.");
		}

		// Mainklasse ermitteln
		String mc = null;
		if (manifest != null) {
			Attributes att = manifest.getMainAttributes();
			mc = att.getValue(Attributes.Name.MAIN_CLASS);
		}
		try {
			// hier muss der Packagename (mit '.') innerhalb der *.jar
			// ohne Dateiendung angegeben werden
			mc = mc.replace('/', '.');
			clazz = cl.loadClass(mc);
		} catch (ClassNotFoundException e) {
			e.printStackTrace();
		}
		return clazz;
	}

	private void loadMethods(String name) throws Exception {
		Class<?> c;
		c = Class.forName(name);
		Object o = c.newInstance();
		Method m[] = c.getDeclaredMethods();
		for (int i = 0; i < m.length; i++) {
			System.out.println("\nMethode: " + m[i].toString());
			System.out.println("Methodenname: " + m[i].getName());
			System.out.println("Return-Typ: " + m[i].getGenericReturnType());
			try {
				Type[] pType = m[i].getGenericParameterTypes();
				for (Type type : pType) {
					System.out.println("Parameter-Typ: " + type.toString());
					if (type.equals(double.class))
						m[i].invoke(o, Math.PI);
					if (type.equals(int.class))
						m[i].invoke(o, 4711);
				}
			} catch (IllegalArgumentException e) {
				e.printStackTrace();
			} catch (IllegalAccessException e) {
				e.printStackTrace();
			} catch (InvocationTargetException e) {
				e.printStackTrace();
			}
		}
	}
	
	public static void main(String[] args) throws Exception {
		String path = "jar";
		String file = "Test.jar";

		JarAuslesen ja = new JarAuslesen();

		System.out.println(ja.readClassFromJar(path, file));

		ja.loadMethods(ja.readClassFromJar(path, file).getName());

	}
}