ActiveMQ example source code file (SimpleMessageList.java)

This example ActiveMQ source code file (SimpleMessageList.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Java - ActiveMQ tags/keywords

arraylist, iterator, linkedlist, list, list, logger, message, messagelist, messagereference, messagereference, object, object, simplemessagelist, simplemessagelist, util

The ActiveMQ SimpleMessageList.java source code

/**
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.activemq.memory.list;

import java.util.ArrayList;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.List;
import org.apache.activemq.broker.region.MessageReference;
import org.apache.activemq.command.ActiveMQDestination;
import org.apache.activemq.command.Message;
import org.apache.activemq.filter.DestinationFilter;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * A simple fixed size {@link MessageList} where there is a single, fixed size
 * list that all messages are added to for simplicity. Though this will lead to
 * possibly slow recovery times as many more messages than is necessary will
 * have to be iterated through for each subscription.
 * 
 * 
 */
public class SimpleMessageList implements MessageList {
    private static final Logger LOG = LoggerFactory.getLogger(SimpleMessageList.class);
    private final LinkedList<MessageReference> list = new LinkedList();
    private int maximumSize = 100 * 64 * 1024;
    private int size;
    private final Object lock = new Object();

    public SimpleMessageList() {
    }

    public SimpleMessageList(int maximumSize) {
        this.maximumSize = maximumSize;
    }

    public void add(MessageReference node) {
        int delta = node.getMessageHardRef().getSize();
        synchronized (lock) {
            list.add(node);
            size += delta;
            while (size > maximumSize) {
                MessageReference evicted = list.removeFirst();
                size -= evicted.getMessageHardRef().getSize();
            }
        }
    }

    public List<MessageReference> getMessages(ActiveMQDestination destination) {
        return getList();
    }

    public Message[] browse(ActiveMQDestination destination) {
        List<Message> result = new ArrayList();
        DestinationFilter filter = DestinationFilter.parseFilter(destination);
        synchronized (lock) {
            for (Iterator<MessageReference> i = list.iterator(); i.hasNext();) {
                MessageReference ref = i.next();
                Message msg;
                msg = ref.getMessage();
                if (filter.matches(msg.getDestination())) {
                    result.add(msg);
                }

            }
        }
        return result.toArray(new Message[result.size()]);
    }

    /**
     * Returns a copy of the list
     */
    public List<MessageReference> getList() {
        synchronized (lock) {
            return new ArrayList<MessageReference>(list);
        }
    }

    public int getSize() {
        synchronized (lock) {
            return size;
        }
    }

    public void clear() {
        synchronized (lock) {
            list.clear();
            size = 0;
        }
    }

}