1 /*
2 * Licensed to the Apache Software Foundation (ASF) under one or more
3 * contributor license agreements. See the NOTICE file distributed with
4 * this work for additional information regarding copyright ownership.
5 * The ASF licenses this file to You under the Apache License, Version 2.0
6 * (the "License"); you may not use this file except in compliance with
7 * the License. You may obtain a copy of the License at
8 *
9 * http://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the License for the specific language governing permissions and
15 * limitations under the License.
16 */
17 package org.apache.commons.jnet;
18
19 import java.net.URLStreamHandler;
20 import java.net.URLStreamHandlerFactory;
21
22 /**
23 * A dynamic url stream handler factory that stores the current delegate factory
24 * in a thread local variable.
25 *
26 * This allows to change the url handler factory at runtime dynamically through
27 * the {@link #push(URLStreamHandlerFactory)} and {@link #pop()} methods.
28 */
29 public class DynamicURLStreamHandlerFactory extends ParentAwareURLStreamHandlerFactory {
30
31 /** The thread local holding the current factory. */
32 protected static final ThreadLocal FACTORY = new InheritableThreadLocal();
33
34 /**
35 * Push a url stream handler factory on top of the stack.
36 */
37 public static void push(URLStreamHandlerFactory factory) {
38 // no need to synchronize as we use a thread local
39 if ( !(factory instanceof ParentAwareURLStreamHandlerFactory) ) {
40 factory = new URLStreamHandlerFactoryWrapper(factory);
41 }
42 URLStreamHandlerFactory old = (URLStreamHandlerFactory) FACTORY.get();
43 ((ParentAwareURLStreamHandlerFactory)factory).setParentFactory(old);
44 FACTORY.set(factory);
45 }
46
47 /**
48 * Pop the lastest url stream handler factory from the stack.
49 */
50 public static void pop() {
51 ParentAwareURLStreamHandlerFactory factory = (ParentAwareURLStreamHandlerFactory)FACTORY.get();
52 if ( factory != null ) {
53 FACTORY.set(factory.getParent());
54 }
55 }
56
57 /**
58 * @see org.apache.commons.jnet.ParentAwareURLStreamHandlerFactory#create(java.lang.String)
59 */
60 protected URLStreamHandler create(String protocol) {
61 ParentAwareURLStreamHandlerFactory factory = (ParentAwareURLStreamHandlerFactory)FACTORY.get();
62 if ( factory != null ) {
63 return factory.createURLStreamHandler(protocol);
64 }
65 return null;
66 }
67 }