Dynamic package loading..

Question

Hello all,
Here is what I am trying to do. We have a jar package which is dynamic in nature. To avoid bringing down the server every time it gets changed, we decided to bring in the dynamic mode of loading packages. We decided to use the URLClassLoader against a jar package posted on a remote server.
But I am stuck at a point. Despite the change in the remote package and getting reloaded, the class being executed remains the old one. Here is a sample of what I am trying to do :
import java.net.*;
import java.io.*;
public class TestURLClassLoad {
     public static void main(String[] args) {
          try {
               String urlString = "jar:http://myhost/test.jar!/";
               URL[] urls = new URL[1];
               urls[0] = new URL(urlString);
               URLClassLoader ucl = new URLClassLoader(urls);
               Class myClass = ucl.loadClass("MyClass");
               Object myObject = myClass.newInstance();
               ucl = null;
               myClass = null;
               myObject = null;
               try {
                    Thread.sleep(10000);
                    // I have modified the Jar package at this point ..
               }catch(Exception e1) {}
               ucl = new URLClassLoader(urls);
               myClass = ucl.loadClass("MyClass");
               myObject = myClass.newInstance();
          catch(Exception e) {
               e.printStackTrace();
}The new instance however generates the same, old class. The new class is not being loaded in.
Any inputs on how to make this work ?
Thanks so much.

Answer 1

I realize this post is from a long time ago but someone may be able to help explain why when you create a newInstance() of a class and you check it it is an instanceOf an interface it always returns false. Here is a modified main() of the sample given:
public static void main(String[] args) throws Exception {
      File file = new File("myJAR.jar");
      JARClassLoader2 loader = new JARClassLoader2(file);
      Class[] classes = loader.getClasses();
      for (int i = 1; i < classes.length; i++) {
         System.out.println("Class: " + classes.getName());
Object o = classes[i].newInstance();
if (o instanceof SomeInterface) {
System.out.println("Instance of TextProcessingRoutine = true");
I have noticed this ONLY returns false if the classes are in a package.  If they are in no package (or default package for eclipse) it works fine.
And I know 100% that the classes I am checking are an instance of SomeInterface.
Thanks,