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      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 
     32 package 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  */
     44 public 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