/*

  * 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.commons.jnet;

 import java.net.URLStreamHandler;

 import java.net.URLStreamHandlerFactory;

 /**

  * A dynamic url stream handler factory that stores the current delegate factory

  * in a thread local variable.

  *

  * This allows to change the url handler factory at runtime dynamically through

  * the {@link #push(URLStreamHandlerFactory)} and {@link #pop()} methods.

  */

 public class DynamicURLStreamHandlerFactory extends ParentAwareURLStreamHandlerFactory {

     /** The thread local holding the current factory. */

     protected static final ThreadLocal FACTORY = new InheritableThreadLocal();

     /**

      * Push a url stream handler factory on top of the stack.

      */

     public static void push(URLStreamHandlerFactory factory) {

         // no need to synchronize as we use a thread local

         if ( !(factory instanceof ParentAwareURLStreamHandlerFactory) ) {

             factory = new URLStreamHandlerFactoryWrapper(factory);

         }

         URLStreamHandlerFactory old = (URLStreamHandlerFactory) FACTORY.get();

         ((ParentAwareURLStreamHandlerFactory)factory).setParentFactory(old);

         FACTORY.set(factory);

     }

     /**

      * Pop the lastest url stream handler factory from the stack.

      */

     public static void pop() {

         ParentAwareURLStreamHandlerFactory factory = (ParentAwareURLStreamHandlerFactory)FACTORY.get();

         if ( factory != null ) {

             FACTORY.set(factory.getParent());

         }

     }

     /**

      * @see org.apache.commons.jnet.ParentAwareURLStreamHandlerFactory#create(java.lang.String)

      */

     protected URLStreamHandler create(String protocol) {

         ParentAwareURLStreamHandlerFactory factory = (ParentAwareURLStreamHandlerFactory)FACTORY.get();

         if ( factory != null ) {

             return factory.createURLStreamHandler(protocol);

         }

         return null;

     }

 }