/*
* 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.catalina.webresources;
import java.net.URL;
import java.net.URLStreamHandler;
import java.net.URLStreamHandlerFactory;
import java.util.Iterator;
import java.util.List;
import java.util.concurrent.CopyOnWriteArrayList;
public class TomcatURLStreamHandlerFactory implements URLStreamHandlerFactory {
private static final String WAR_PROTOCOL = "war";
// Singleton instance
private static volatile TomcatURLStreamHandlerFactory instance = null;
/**
* Obtain a reference to the singleton instance. It is recommended that
* callers check the value of {@link #isRegistered()} before using the
* returned instance.
*/
public static TomcatURLStreamHandlerFactory getInstance() {
getInstanceInternal(true);
return instance;
}
private static TomcatURLStreamHandlerFactory getInstanceInternal(boolean register) {
// Double checked locking. OK because instance is volatile.
if (instance == null) {
synchronized (TomcatURLStreamHandlerFactory.class) {
if (instance == null) {
instance = new TomcatURLStreamHandlerFactory(register);
}
}
}
return instance;
}
private final boolean registered;
// List of factories for application defined stream handler factories.
private List<URLStreamHandlerFactory> userFactories =
new CopyOnWriteArrayList<>();
/**
* Register this factory with the JVM. May be called more than once. The
* implementation ensures that registration only occurs once.
*
* @return <code>true</code> if the factory is already registered with the
* JVM or was successfully registered as a result of this call.
* <code>false</code> if the factory was disabled prior to this
* call.
*/
public static boolean register() {
return getInstanceInternal(true).isRegistered();
}
/**
* Prevent this this factory from registering with the JVM. May be called
* more than once.
*
* @return <code>true</code> if the factory is already disabled or was
* successfully disabled as a result of this call.
* <code>false</code> if the factory was already registered prior
* to this call.
*/
public static boolean disable() {
return !getInstanceInternal(false).isRegistered();
}
/**
* Release references to any user provided factories that have been loaded
* using the provided class loader. Called during web application stop to
* prevent memory leaks.
*/
public static void release(ClassLoader classLoader) {
Iterator<URLStreamHandlerFactory> iter = instance.userFactories.iterator();
while (iter.hasNext()) {
ClassLoader factoryLoader = iter.next().getClass().getClassLoader();
while (factoryLoader != null) {
if (classLoader.equals(factoryLoader)) {
iter.remove();
break;
}
factoryLoader = factoryLoader.getParent();
}
}
}
private TomcatURLStreamHandlerFactory(boolean register) {
// Hide default constructor
// Singleton pattern to ensure there is only one instance of this
// factory
this.registered = register;
if (register) {
URL.setURLStreamHandlerFactory(this);
}
}
public boolean isRegistered() {
return registered;
}
/**
* Since the JVM only allows a single call to
* {@link URL#setURLStreamHandlerFactory(URLStreamHandlerFactory)} and
* Tomcat needs to register a handler, provide a mechanism to allow
* applications to register their own handlers.
*/
public void addUserFactory(URLStreamHandlerFactory factory) {
userFactories.add(factory);
}
@Override
public URLStreamHandler createURLStreamHandler(String protocol) {
// Tomcat's handler always takes priority so applications can't override
// it.
if (WAR_PROTOCOL.equals(protocol)) {
return new WarURLStreamHandler();
}
// Application handlers
for (URLStreamHandlerFactory factory : userFactories) {
URLStreamHandler handler =
factory.createURLStreamHandler(protocol);
if (handler != null) {
return handler;
}
}
// Unknown protocol
return null;
}
}