DefaultedHttpParams.java revision 417f3b92ba4549b2f22340e3107d869d2b9c5bb8 
1/*
2 * $HeadURL: http://svn.apache.org/repos/asf/httpcomponents/httpcore/trunk/module-main/src/main/java/org/apache/http/params/DefaultedHttpParams.java $
3 * $Revision: 610763 $
4 * $Date: 2008-01-10 04:01:13 -0800 (Thu, 10 Jan 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.params;
33
34import org.apache.http.params.HttpParams;
35
36/**
37 * {@link HttpParams} implementation that delegates resolution of a parameter
38 * to the given default {@link HttpParams} instance if the parameter is not
39 * present in the local one. The state of the local collection can be mutated,
40 * whereas the default collection is treated as read-only.
41 *
42 * @author <a href="mailto:oleg at ural.ru">Oleg Kalnichevski</a>
43 *
44 * @version $Revision: 610763 $
45 */
46public final class DefaultedHttpParams extends AbstractHttpParams {
47
48    private final HttpParams local;
49    private final HttpParams defaults;
50
51    public DefaultedHttpParams(final HttpParams local, final HttpParams defaults) {
52        super();
53        if (local == null) {
54            throw new IllegalArgumentException("HTTP parameters may not be null");
55        }
56        this.local = local;
57        this.defaults = defaults;
58    }
59
60    /**
61     * Creates a copy of the local collection with the same default
62     */
63    public HttpParams copy() {
64        HttpParams clone = this.local.copy();
65        return new DefaultedHttpParams(clone, this.defaults);
66    }
67
68    /**
69     * Retrieves the value of the parameter from the local collection and, if the
70     * parameter is not set locally, delegates its resolution to the default
71     * collection.
72     */
73    public Object getParameter(final String name) {
74        Object obj = this.local.getParameter(name);
75        if (obj == null && this.defaults != null) {
76            obj = this.defaults.getParameter(name);
77        }
78        return obj;
79    }
80
81    /**
82     * Attempts to remove the parameter from the local collection. This method
83     * <i>does not</i> modify the default collection.
84     */
85    public boolean removeParameter(final String name) {
86        return this.local.removeParameter(name);
87    }
88
89    /**
90     * Sets the parameter in the local collection. This method <i>does not</i>
91     * modify the default collection.
92     */
93    public HttpParams setParameter(final String name, final Object value) {
94        return this.local.setParameter(name, value);
95    }
96
97    public HttpParams getDefaults() {
98        return this.defaults;
99    }
100
101}
102