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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  
18  package org.apache.log4j.helpers;
19  
20  import java.util.Hashtable;
21  
22  /**
23     <code>ThreadLocalMap</code> extends {@link InheritableThreadLocal}
24     to bequeath a copy of the hashtable of the MDC of the parent
25     thread.
26  
27     @author Ceki G&uuml;lc&uuml;
28     @since 1.2
29  */
30  final public class ThreadLocalMap extends InheritableThreadLocal {
31  
32    public
33    final
34    Object childValue(Object parentValue) {
35      Hashtable ht = (Hashtable) parentValue;
36      if(ht != null) {
37        return ht.clone();
38      } else {
39        return null;
40      }
41    }
42  }