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 */
017package org.apache.activemq.util;
018
019import java.io.Serializable;
020import java.util.Comparator;
021
022import javax.jms.Message;
023
024/**
025 * A base class for comparators which works on JMS {@link Message} objects
026 * 
027 * 
028 */
029public abstract class MessageComparatorSupport implements Comparator, Serializable {
030
031    public int compare(Object object1, Object object2) {
032        Message command1 = (Message)object1;
033        Message command2 = (Message)object2;
034        return compareMessages(command1, command2);
035    }
036
037    protected abstract int compareMessages(Message message1, Message message2);
038
039    protected int compareComparators(final Comparable comparable, final Comparable comparable2) {
040        if (comparable == null && comparable2 == null) {
041            return 0;
042        } else if (comparable != null) {
043            if (comparable2 == null) {
044                return 1;
045            }
046            return comparable.compareTo(comparable2);
047        } else if (comparable2 != null) {
048            if (comparable == null) {
049                return -11;
050            }
051            return comparable2.compareTo(comparable) * -1;
052        }
053        return 0;
054    }
055
056}