001/**
002 * Logback: the reliable, generic, fast and flexible logging framework.
003 * Copyright (C) 1999-2015, QOS.ch. All rights reserved.
004 *
005 * This program and the accompanying materials are dual-licensed under
006 * either the terms of the Eclipse Public License v1.0 as published by
007 * the Eclipse Foundation
008 *
009 *   or (per the licensee's choosing)
010 *
011 * under the terms of the GNU Lesser General Public License version 2.1
012 * as published by the Free Software Foundation.
013 */
014package ch.qos.logback.classic.util;
015
016import java.util.HashMap;
017
018/**
019 * This class extends InheritableThreadLocal so that children threads get a copy
020 * of the parent's hashmap.
021 * 
022 * @author Ceki Gülcü
023 */
024public class CopyOnInheritThreadLocal extends InheritableThreadLocal<HashMap<String, String>> {
025
026    /**
027     * Child threads should get a copy of the parent's hashmap.
028     */
029    @Override
030    protected HashMap<String, String> childValue(HashMap<String, String> parentValue) {
031        if (parentValue == null) {
032            return null;
033        } else {
034            return new HashMap<String, String>(parentValue);
035        }
036    }
037
038}