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Java example source code file (DynamicClassLoader.java)
This example Java source code file (DynamicClassLoader.java) is included in the alvinalexander.com
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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);
}
}
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