add jar to classpath at runtime but not able to access resource in jar

Hi,

I have exteneded URLClassLoader to:

import java.net.URL;
import java.net.URLClassLoader;

/**
 * The ExtenedClassLoader class.
 */
public class ExtendedClassLoader extends URLClassLoader {
    /**
     * @param urls, to carryforward the existing classpath.
     */
    public ExtendedClassLoader(URL[] urls) {
        super(urls);
    }

    @Override
    /**
     * add ckasspath to the loader.
     */
    public void addURL(URL url) {
        super.addURL(url);
    }
}

Then to add my jar file to classpath at runtime I use the following
code ( see below).

 private void addToClasspath(){
        try
        {
            URL urls [] = {};

            String path = "/home/xddmid/out/xml.jar";
            String urlPath = "jar:file://" + path + "!/";
            URL url = new URL (urlPath);
            ExtendedClassLoader cl = new ExtendedClassLoader (urls);
            cl.addURL(url);
            String resource =
ClassLoader.getSystemClassLoader().getResource("test.xml").toExternalForm();
            System.out.println ("Success! Resource "+resource + "
found!");
        }
        catch (Exception ex)
        {
            System.out.println ("Failed.");
            ex.printStackTrace ();
        }

I have verified that the jarfile exists and that it contains "test.xml
file" ( "jar tvf xml.jar).
The "test.xml" file is directly in root ( no package name).

I get a NullPointerException for this line:

 String resource =
ClassLoader.getSystemClassLoader().getResource("test.xml").toExternalForm();

Any help or ideas are very much appreciated.

br,

//mike