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/*******************************************************************************
* Copyright (c) 2009, 2010 VMware Inc.
*
* All rights reserved. This program and the accompanying materials
* are made available under the terms of the Eclipse Public License v1.0
* and Apache License v2.0 which accompanies this distribution.
* The Eclipse Public License is available at
* http://www.eclipse.org/legal/epl-v10.html
* and the Apache License v2.0 is available at
* http://www.opensource.org/licenses/apache2.0.php.
* You may elect to redistribute this code under either of these licenses.
*
* Contributors:
* VMware Inc. - initial contribution
*******************************************************************************/
package org.eclipse.gemini.web.tomcat.internal.loading;
import java.io.IOException;
import java.net.URL;
import java.security.AccessController;
import java.security.PrivilegedAction;
import java.security.PrivilegedActionException;
import java.security.PrivilegedExceptionAction;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Enumeration;
import java.util.List;
import java.util.Vector;
/**
* <strong>Concurrent Semantics</strong><br />
*
* This class is immutable and therefore thread safe.
*/
public final class ChainedClassLoader extends ClassLoader {
/** list of loaders */
private final List<ClassLoader> loaders;
/**
* Constructs a new <code>ChainedClassLoader</code> instance.
*
* @param loaders
* array of non-null class loaders
* @param parent
* parent class loader (can be null)
*/
ChainedClassLoader(ClassLoader... loaders) {
List<ClassLoader> l = new ArrayList<ClassLoader>();
for (int i = 0; i < loaders.length; i++) {
ClassLoader classLoader = loaders[i];
if (!l.contains(classLoader)) {
l.add(classLoader);
}
}
this.loaders = Collections.unmodifiableList(l);
}
public static ChainedClassLoader create(final ClassLoader... loaders) {
return AccessController
.doPrivileged(new PrivilegedAction<ChainedClassLoader>() {
public ChainedClassLoader run() {
return new ChainedClassLoader(loaders);
}
});
}
@Override
public URL getResource(final String name) {
if (System.getSecurityManager() != null) {
return AccessController.doPrivileged(new PrivilegedAction<URL>() {
public URL run() {
return doGetResource(name);
}
});
} else {
return doGetResource(name);
}
}
@Override
public Enumeration<URL> getResources(final String name) throws IOException {
if (System.getSecurityManager() != null) {
try {
return AccessController
.doPrivileged(new PrivilegedExceptionAction<Enumeration<URL>>() {
public Enumeration<URL> run() throws Exception {
return doGetResources(name);
}
});
} catch (PrivilegedActionException e) {
Exception exception = e.getException();
if (exception instanceof RuntimeException) {
throw (RuntimeException) exception;
} else if (exception instanceof IOException) {
throw (IOException) exception;
} else {
throw new IllegalStateException(
"Unexpected Exception from privileged action.",
exception);
}
}
} else {
return doGetResources(name);
}
}
private Enumeration<URL> doGetResources(String name) throws IOException {
Vector<URL> urls = new Vector<URL>();
for (ClassLoader loader : this.loaders) {
Enumeration<URL> resources = loader.getResources(name);
if (resources != null) {
while (resources.hasMoreElements()) {
URL url = (URL) resources.nextElement();
urls.add(url);
}
}
}
return urls.elements();
}
private URL doGetResource(String name) {
URL url = null;
for (int i = 0; i < loaders.size(); i++) {
ClassLoader loader = (ClassLoader) loaders.get(i);
url = loader.getResource(name);
if (url != null)
return url;
}
return url;
}
public Class<?> loadClass(final String name) throws ClassNotFoundException {
if (System.getSecurityManager() != null) {
try {
return AccessController
.doPrivileged(new PrivilegedExceptionAction<Class<?>>() {
public Class<?> run() throws Exception {
return doLoadClass(name);
}
});
} catch (PrivilegedActionException pae) {
throw (ClassNotFoundException) pae.getException();
}
} else {
return doLoadClass(name);
}
}
private Class<?> doLoadClass(String name) throws ClassNotFoundException {
Class<?> clazz = null;
for (int i = 0; i < loaders.size(); i++) {
ClassLoader loader = (ClassLoader) loaders.get(i);
try {
clazz = loader.loadClass(name);
return clazz;
} catch (ClassNotFoundException e) {
// keep moving through the class loaders
}
}
throw new ClassNotFoundException(name);
}
}
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