/** | |
* Licensed to the Apache Software Foundation (ASF) under one | |
* or more contributor license agreements. See the NOTICE file | |
* distributed with this work for additional information | |
* regarding copyright ownership. The ASF licenses this file | |
* to you under the Apache License, Version 2.0 (the | |
* "License"); you may not use this file except in compliance | |
* with the License. You may obtain a copy of the License at | |
* | |
* http://www.apache.org/licenses/LICENSE-2.0 | |
* | |
* Unless required by applicable law or agreed to in writing, | |
* software distributed under the License is distributed on an | |
* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY | |
* KIND, either express or implied. See the License for the | |
* specific language governing permissions and limitations | |
* under the License. | |
*/ | |
package org.apache.aries.spifly; | |
import java.io.IOException; | |
import java.io.InputStream; | |
import java.net.URL; | |
import java.util.ArrayList; | |
import java.util.Collections; | |
import java.util.Enumeration; | |
import java.util.List; | |
/** A classloader that delegates to a number of other classloaders. | |
* This classloader can be used if a single classloader is needed that has | |
* vibisility of a number of other classloaders. For example if a Thread Context | |
* Classloader is needed that has visibility of a number of bundles so that | |
* ServiceLoader.load() can find all the services provided by these bundles. | |
*/ | |
public class MultiDelegationClassloader extends ClassLoader { | |
private final ClassLoader[] delegates; | |
public MultiDelegationClassloader(ClassLoader ... classLoaders) { | |
if (classLoaders == null) | |
throw new NullPointerException(); | |
delegates = classLoaders.clone(); | |
} | |
@Override | |
public URL getResource(String name) { | |
for (ClassLoader cl : delegates) { | |
URL res = cl.getResource(name); | |
if (res != null) | |
return res; | |
} | |
return null; | |
} | |
@Override | |
public InputStream getResourceAsStream(String name) { | |
for (ClassLoader cl : delegates) { | |
InputStream is = cl.getResourceAsStream(name); | |
if (is != null) | |
return is; | |
} | |
return null; | |
} | |
@Override | |
public Enumeration<URL> getResources(String name) throws IOException { | |
List<URL> urls = new ArrayList<URL>(); | |
for (ClassLoader cl : delegates) { | |
urls.addAll(Collections.list(cl.getResources(name))); | |
} | |
return Collections.enumeration(urls); | |
} | |
@Override | |
public Class<?> loadClass(String name) throws ClassNotFoundException { | |
ClassNotFoundException lastEx = null; | |
for (ClassLoader cl : delegates) { | |
try { | |
return cl.loadClass(name); | |
} catch (ClassNotFoundException e) { | |
lastEx = e; | |
} | |
} | |
throw lastEx; | |
} | |
} |