Java Programming

Extends thread http://forum.java.sun.com/thread.jspa?threadID=5246791&tstart=15 in order to give away more duke points.

Is it possible to load a static object with a custom class loader that makes calls to this object without reflection?

Some code:

package tests.classloader;

import java.io.DataInputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.util.Hashtable;

public class UnloadingTest {
	public static void main(String[] args) throws Exception {
		CustomClassLoader test = new CustomClassLoader();
		
        Object o = test.loadClass("tests.classloader.Singleton").newInstance();
        
        System.out.println("Instantiated Singleton: " + o.getClass());
        System.out.println("Instantiated Singleton classloader: " + o.getClass().getClassLoader());        
        System.out.println("Static Singleton outside singleton constructor:" + Singleton.class.getClassLoader());
	}
}

class CustomClassLoader extends ClassLoader {
	private Hashtable<String, Class<?>> classes = new Hashtable<String, Class<?>>();
	
    public CustomClassLoader(){
        super(CustomClassLoader.class.getClassLoader());    	
    }
  
    public Class loadClass(String className) throws ClassNotFoundException {
         return findClass(className);
    }
 
    public Class findClass(String className){
        byte classByte[];
        Class result=null;
        result = (Class)classes.get(className);
        if(result != null){
            return result;
        }
        
        // since findClass is overloaded we'll get a recursive
        // call from system class loader here
        if (className.indexOf("java") >= 0) {
	        try{
	        	result = findSystemClass(className);
	        	classes.put(className,result);
	            return result;
	        }catch(Exception e){
	        }
        }
        
        try{
           String classPath =  File.separatorChar +   ((String)ClassLoader.getSystemResource(className.replace('.',File.separatorChar)+".class").getFile()).substring(1);
           classByte = loadClassData(classPath);
            result = defineClass(className,classByte,0,classByte.length,null);
            classes.put(className,result);
            return result;
        }catch(Exception e){
            return null;
        } 
    }
 
    private byte[] loadClassData(String className) throws IOException {
 
        File f ;
        f = new File(className);
        int size = (int)f.length();
        byte buff[] = new byte[size];
        FileInputStream fis = new FileInputStream(f);
        DataInputStream dis = new DataInputStream(fis);
        dis.readFully(buff);
        dis.close();
        return buff;
    }    
}

And the separate singleton class:

package tests.classloader;

public class Singleton {
	public static boolean loaded = false;
	
	private static Singleton s;
	
	private static int accesses = 0;
	
	public Singleton() {
		System.out.println("Singleton constructor: " + Singleton.class.getClassLoader());		
		if (loaded) {
			System.out.println("Already loaded.");
		}
		loaded = true;
	}
	
	public static Singleton getInstance() {
		if (!loaded) {
			s = new Singleton();
		}
		return s;
	}
	
	public static int getAccesses() {
		return accesses++;		
	}
	
	public static void dispose() {
		loaded = false;
		s = null;
	}
}

The output is:

Singleton constructor: tests.classloader.CustomClassLoader@ca318a
Instantiated Singleton: class tests.classloader.Singleton
Instantiated Singleton classloader: tests.classloader.CustomClassLoader@ca318a
Static Singleton outside singleton constructor:sun.misc.Launcher$AppClassLoader@a9c85c

But I'd like the last line of output to be:

Static Singleton outside singleton constructor: tests.classloader.CustomClassLoader@ca318a

Which seems to be the case in the Singleton constructor.

Is this possible?

Regards
rimu