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    package org.apache.activemq.util;
018    
019    import java.io.Serializable;
020    import java.util.Comparator;
021    
022    import javax.jms.Message;
023    
024    /**
025     * A base class for comparators which works on JMS {@link Message} objects
026     * 
027     * 
028     */
029    public 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    }