/*
* Copyright (c) 2013, grossmann
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* * Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* * Neither the name of the jo-widgets.org nor the
* names of its contributors may be used to endorse or promote products
* derived from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL jo-widgets.org BE LIABLE FOR ANY
* DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH
* DAMAGE.
*/
package org.jowidgets.classloading.api;
import java.io.IOException;
import java.net.URL;
import java.util.Enumeration;
import java.util.LinkedHashSet;
import java.util.LinkedList;
import java.util.List;
import java.util.Set;
import org.jowidgets.util.Assert;
import org.jowidgets.util.CollectionUtils;
public final class SharedClassLoader {
private static final ISharedClassLoader INSTANCE = new SharedClassLoaderImpl();
private SharedClassLoader() {}
public static ISharedClassLoader getInstance() {
return INSTANCE;
}
/**
* Adds a class loader to the shared class loader
*
* @param classLoader The class loader to add
*/
public static void addClassLoader(final IClassLoader classLoader) {
getInstance().addClassLoader(classLoader);
}
/**
* Removes a class loader from the shared class loader
*
* @param classLoader The class loader to remove
*/
public static void removeClassLoader(final IClassLoader classLoader) {
getInstance().removeClassLoader(classLoader);
}
/**
* Gets the composite class loader that uses all registered class loaders to resolve
* the class to load.
* The shared class loader always uses the SystemClassLoader and the ThreadContextLocalClassLoader
* as default (e.g. if no classloader was added)
*
* @return The composite class loader
*/
public static ClassLoader getCompositeClassLoader() {
return getInstance().getCompositeClassLoader();
}
private static final class SharedClassLoaderImpl implements ISharedClassLoader {
private final Set<IClassLoader> classLoaders;
private final ClassLoader compositeClassLoader;
private SharedClassLoaderImpl() {
this.classLoaders = new LinkedHashSet<IClassLoader>();
this.compositeClassLoader = new CompositeClassLoaderImpl();
addClassLoader(ClassLoaderAdapter.create(ClassLoader.getSystemClassLoader()));
addClassLoader(new CurrentThreadClassLoader());
}
@Override
public void addClassLoader(final IClassLoader classLoader) {
Assert.paramNotNull(classLoader, "classLoader");
classLoaders.add(classLoader);
}
@Override
public void removeClassLoader(final IClassLoader classLoader) {
Assert.paramNotNull(classLoader, "classLoader");
classLoaders.remove(classLoader);
}
@Override
public ClassLoader getCompositeClassLoader() {
return compositeClassLoader;
}
private final class CompositeClassLoaderImpl extends ClassLoader {
@Override
protected Class<?> findClass(final String name) throws ClassNotFoundException {
for (final IClassLoader classLoader : new LinkedList<IClassLoader>(classLoaders)) {
try {
return classLoader.findClass(name);
}
catch (final Exception e) {
//Nothing to do, this loader may not know the class
}
}
throw new ClassNotFoundException("Class with the name '" + name + "' not found");
}
@Override
protected URL findResource(final String name) {
for (final IClassLoader classLoader : new LinkedList<IClassLoader>(classLoaders)) {
try {
final URL result = classLoader.findResource(name);
if (result != null) {
return result;
}
}
catch (final Exception e) {
//Nothing to do, this loader may not know the class
}
}
return null;
}
@Override
protected Enumeration<URL> findResources(final String name) throws IOException {
final List<URL> result = new LinkedList<URL>();
for (final IClassLoader classLoader : new LinkedList<IClassLoader>(classLoaders)) {
try {
final Enumeration<URL> resources = classLoader.findResources(name);
CollectionUtils.addFromEnumerationToCollection(result, resources);
}
catch (final Exception e) {
//Nothing to do, this loader may not know the class
}
}
return CollectionUtils.enumerationFromCollection(result);
}
}
}
private static final class CurrentThreadClassLoader implements IClassLoader {
@Override
public Class<?> findClass(final String name) throws ClassNotFoundException {
final ClassLoader tccl = Thread.currentThread().getContextClassLoader();
if (tccl != null) {
return tccl.loadClass(name);
}
else {
throw new ClassNotFoundException("No Thread context classloader set");
}
}
@Override
public URL findResource(final String name) {
final ClassLoader tccl = Thread.currentThread().getContextClassLoader();
if (tccl != null) {
return tccl.getResource(name);
}
else {
return null;
}
}
@Override
public Enumeration<URL> findResources(final String name) throws IOException {
final ClassLoader tccl = Thread.currentThread().getContextClassLoader();
if (tccl != null) {
return tccl.getResources(name);
}
else {
return null;
}
}
}
}