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.broker.region.policy;
018    
019    import java.io.IOException;
020    import java.util.Iterator;
021    import java.util.LinkedList;
022    
023    import org.apache.activemq.broker.region.MessageReference;
024    
025    /**
026     * An eviction strategy which evicts the oldest message with the lowest priority first.
027     * 
028     * @org.apache.xbean.XBean
029     * 
030     * messageEvictionStrategy
031     */
032    public class OldestMessageWithLowestPriorityEvictionStrategy extends MessageEvictionStrategySupport {
033    
034        public MessageReference[] evictMessages(LinkedList messages) throws IOException {
035            byte lowestPriority = Byte.MAX_VALUE;
036            int pivot = 0;
037            Iterator iter = messages.iterator();
038            for (int i = 0; iter.hasNext(); i++) {
039                MessageReference reference = (MessageReference) iter.next();
040                byte priority = reference.getMessage().getPriority();
041                if (priority < lowestPriority) {
042                    lowestPriority = priority;
043                    pivot = i;
044                }
045            }
046            return new MessageReference[] {(MessageReference) messages.remove(pivot)};
047        }
048    }