1/*
2 * $HeadURL: http://svn.apache.org/repos/asf/httpcomponents/httpcore/trunk/module-main/src/main/java/org/apache/http/protocol/DefaultedHttpContext.java $
3 * $Revision: 654882 $
4 * $Date: 2008-05-09 09:58:59 -0700 (Fri, 09 May 2008) $
5 *
6 * ====================================================================
7 * Licensed to the Apache Software Foundation (ASF) under one
8 * or more contributor license agreements.  See the NOTICE file
9 * distributed with this work for additional information
10 * regarding copyright ownership.  The ASF licenses this file
11 * to you under the Apache License, Version 2.0 (the
12 * "License"); you may not use this file except in compliance
13 * with the License.  You may obtain a copy of the License at
14 *
15 *   http://www.apache.org/licenses/LICENSE-2.0
16 *
17 * Unless required by applicable law or agreed to in writing,
18 * software distributed under the License is distributed on an
19 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
20 * KIND, either express or implied.  See the License for the
21 * specific language governing permissions and limitations
22 * under the License.
23 * ====================================================================
24 *
25 * This software consists of voluntary contributions made by many
26 * individuals on behalf of the Apache Software Foundation.  For more
27 * information on the Apache Software Foundation, please see
28 * <http://www.apache.org/>.
29 *
30 */
31
32package org.apache.http.protocol;
33
34/**
35 * {@link HttpContext} implementation that delegates resolution of an attribute
36 * to the given default {@link HttpContext} instance if the attribute is not
37 * present in the local one. The state of the local context can be mutated,
38 * whereas the default context is treated as read-only.
39 *
40 * @author <a href="mailto:oleg at ural.ru">Oleg Kalnichevski</a>
41 *
42 * @version $Revision: 654882 $
43 */
44public final class DefaultedHttpContext implements HttpContext {
45
46    private final HttpContext local;
47    private final HttpContext defaults;
48
49    public DefaultedHttpContext(final HttpContext local, final HttpContext defaults) {
50        super();
51        if (local == null) {
52            throw new IllegalArgumentException("HTTP context may not be null");
53        }
54        this.local = local;
55        this.defaults = defaults;
56    }
57
58    public Object getAttribute(final String id) {
59        Object obj = this.local.getAttribute(id);
60        if (obj == null) {
61            return this.defaults.getAttribute(id);
62        } else {
63            return obj;
64        }
65    }
66
67    public Object removeAttribute(final String id) {
68        return this.local.removeAttribute(id);
69    }
70
71    public void setAttribute(final String id, final Object obj) {
72        this.local.setAttribute(id, obj);
73    }
74
75    public HttpContext getDefaults() {
76        return this.defaults;
77    }
78
79}
80