Java example source code file (DynamicClassLoader.java)

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Java - Java tags/keywords

class, classnotfoundexception, concurrenthashmap, dynamicclassloader, empty_urls, net, network, object, reference, referencequeue, softreference, threading, threads, url, urlclassloader, util

The DynamicClassLoader.java Java example source code

/**
 *   Copyright (c) Rich Hickey. All rights reserved.
 *   The use and distribution terms for this software are covered by the
 *   Eclipse Public License 1.0 (http://opensource.org/licenses/eclipse-1.0.php)
 *   which can be found in the file epl-v10.html at the root of this distribution.
 *   By using this software in any fashion, you are agreeing to be bound by
 * 	 the terms of this license.
 *   You must not remove this notice, or any other, from this software.
 **/

/* rich Aug 21, 2007 */

package clojure.lang;

import java.lang.ref.Reference;
import java.util.HashMap;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
import java.net.URLClassLoader;
import java.net.URL;
import java.lang.ref.ReferenceQueue;
import java.lang.ref.SoftReference;

public class DynamicClassLoader extends URLClassLoader{
HashMap<Integer, Object[]> constantVals = new HashMap();
static ConcurrentHashMap<String, ReferenceclassCache =
        new ConcurrentHashMap<String, Reference();

static final URL[] EMPTY_URLS = new URL[]{};

static final ReferenceQueue rq = new ReferenceQueue();

public DynamicClassLoader(){
    //pseudo test in lieu of hasContextClassLoader()
	super(EMPTY_URLS,(Thread.currentThread().getContextClassLoader() == null ||
                Thread.currentThread().getContextClassLoader() == ClassLoader.getSystemClassLoader())?
                Compiler.class.getClassLoader():Thread.currentThread().getContextClassLoader());
}

public DynamicClassLoader(ClassLoader parent){
	super(EMPTY_URLS,parent);
}

public Class defineClass(String name, byte[] bytes, Object srcForm){
	Util.clearCache(rq, classCache);
	Class c = defineClass(name, bytes, 0, bytes.length);
    classCache.put(name, new SoftReference(c,rq));
    return c;
}

static Class<?> findInMemoryClass(String name) {
    Reference<Class> cr = classCache.get(name);
	if(cr != null)
		{
		Class c = cr.get();
        if(c != null)
            return c;
		else
	        classCache.remove(name, cr);
		}
	return null;
}

protected Class<?>findClass(String name) throws ClassNotFoundException {
	Class c = findInMemoryClass(name);
	if (c != null)
		return c;
	else
		return super.findClass(name);
}

protected synchronized Class<?> loadClass(String name, boolean resolve) throws ClassNotFoundException {
	Class c = findLoadedClass(name);
	if (c == null) {
		c = findInMemoryClass(name);
		if (c == null)
			c = super.loadClass(name, false);
    }
	if (resolve)
		resolveClass(c);
	return c;
}

public void registerConstants(int id, Object[] val){
	constantVals.put(id, val);
}

public Object[] getConstants(int id){
	return constantVals.get(id);
}

public void addURL(URL url){
	super.addURL(url);
}

}