1   /**
2    * Logback: the reliable, generic, fast and flexible logging framework.
3    * Copyright (C) 1999-2015, QOS.ch. All rights reserved.
4    *
5    * This program and the accompanying materials are dual-licensed under
6    * either the terms of the Eclipse Public License v1.0 as published by
7    * the Eclipse Foundation
8    *
9    *   or (per the licensee's choosing)
10   *
11   * under the terms of the GNU Lesser General Public License version 2.1
12   * as published by the Free Software Foundation.
13   */
14  package ch.qos.logback.classic.util;
15  
16  import java.util.HashMap;
17  
18  /**
19   * This class extends InheritableThreadLocal so that children threads get a copy
20   * of the parent's hashmap.
21   * 
22   * @author Ceki Gülcü
23   */
24  public class CopyOnInheritThreadLocal extends InheritableThreadLocal<HashMap<String, String>> {
25  
26      /**
27       * Child threads should get a copy of the parent's hashmap.
28       */
29      @Override
30      protected HashMap<String, String> childValue(HashMap<String, String> parentValue) {
31          if (parentValue == null) {
32              return null;
33          } else {
34              return new HashMap<String, String>(parentValue);
35          }
36      }
37  
38  }