001/*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements.  See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License.  You may obtain a copy of the License at
008 * 
009 *      http://www.apache.org/licenses/LICENSE-2.0
010 * 
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017
018package org.apache.log4j.helpers;
019
020import java.util.Hashtable;
021
022/**
023   <code>ThreadLocalMap</code> extends {@link InheritableThreadLocal}
024   to bequeath a copy of the hashtable of the MDC of the parent
025   thread.
026
027   @author Ceki G&uuml;lc&uuml;
028   @since 1.2
029*/
030final public class ThreadLocalMap extends InheritableThreadLocal {
031
032  public
033  final
034  Object childValue(Object parentValue) {
035    Hashtable ht = (Hashtable) parentValue;
036    if(ht != null) {
037      return ht.clone();
038    } else {
039      return null;
040    }
041  }
042}