// $Id: ArgoJarClassLoader.java,v 1.4 2004/09/11 09:25:57 mvw Exp $
// Copyright (c) 2003 The Regents of the University of California. All
// Rights Reserved. Permission to use, copy, modify, and distribute this
// software and its documentation without fee, and without a written
// agreement is hereby granted, provided that the above copyright notice
// and this paragraph appear in all copies.  This software program and
// documentation are copyrighted by The Regents of the University of
// California. The software program and documentation are supplied "AS
// IS", without any accompanying services from The Regents. The Regents
// does not warrant that the operation of the program will be
// uninterrupted or error-free. The end-user understands that the program
// was developed for research purposes and is advised not to rely
// exclusively on the program for any reason.  IN NO EVENT SHALL THE
// UNIVERSITY OF CALIFORNIA BE LIABLE TO ANY PARTY FOR DIRECT, INDIRECT,
// SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES, INCLUDING LOST PROFITS,
// ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS DOCUMENTATION, EVEN IF
// THE UNIVERSITY OF CALIFORNIA HAS BEEN ADVISED OF THE POSSIBILITY OF
// SUCH DAMAGE. THE UNIVERSITY OF CALIFORNIA SPECIFICALLY DISCLAIMS ANY
// WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
// MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE SOFTWARE
// PROVIDED HEREUNDER IS ON AN "AS IS" BASIS, AND THE UNIVERSITY OF
// CALIFORNIA HAS NO OBLIGATIONS TO PROVIDE MAINTENANCE, SUPPORT,
// UPDATES, ENHANCEMENTS, OR MODIFICATIONS.

package org.argouml.application.security;

import java.net.URL;
import java.net.URLClassLoader;
import java.net.JarURLConnection;
import java.lang.reflect.Method;
import java.lang.reflect.Modifier;
import java.lang.reflect.InvocationTargetException;
import java.util.jar.Attributes;
import java.io.IOException;

/**
 * A class loader for loading jar files, both local and remote.
 *
 * This source was taken primarily from 
 * Sun's tutorial
 *
 *  @author Unascribed
 */
public class ArgoJarClassLoader extends URLClassLoader {
    private URL url;

    /**
     * Creates a new ClassLoader for the specified url.
     *
     * @param u the url of the jar file
     */
    public ArgoJarClassLoader(URL u) {
	super(new URL[] {
	    u 
	});
	this.url = u;
    }

    /**
     * Returns the name of the jar file main class, or null if
     * no "Main-Class" manifest attributes was defined.
     *
     * @return the name of the main class
     * @throws IOException if we can not access the file
     */
    public String getMainClassName() throws IOException {
	URL u = new URL("jar", "", url + "!/");
	JarURLConnection uc = (JarURLConnection) u.openConnection();
	Attributes attr = uc.getMainAttributes();
	return attr != null ? attr.getValue(Attributes.Name.MAIN_CLASS) : null;
    }

    /**
     * Invokes the application in this jar file given the name of the
     * main class and an array of arguments. The class must define a
     * static method "main" which takes an array of String arguemtns
     * and is of return type "void".
     *
     * @param name the name of the main class
     * @param args the arguments for the application
     * @exception ClassNotFoundException if the specified class could not
     *            be found
     * @exception NoSuchMethodException if the specified class does not
     *            contain a "main" method
     * @exception InvocationTargetException if the application raised an
     *            exception
     */
    public void invokeClass(String name, String[] args)
	throws ClassNotFoundException,
	       NoSuchMethodException,
	       InvocationTargetException
    {
	Class c = loadClass(name);
	Method m = c.getMethod("main", new Class[] {
		args.getClass() 
	});
	m.setAccessible(true);
	int mods = m.getModifiers();
	if (m.getReturnType() != void.class || !Modifier.isStatic(mods) 
            || !Modifier.isPublic(mods)) {
	    throw new NoSuchMethodException("main");
	}
	try {
	    m.invoke(null, new Object[] {
		args 
	    });
	} catch (IllegalAccessException e) {
	    // This should not happen, as we have disabled access checks
	}
    }

}