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ActiveMQ example source code file (TimedSubscriptionRecoveryPolicy.java)

This example ActiveMQ source code file (TimedSubscriptionRecoveryPolicy.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, arraylist, exception, exception, gc_interval, iterator, list, message, messagereference, messagereference, subscriptionrecoverypolicy, timedsubscriptionrecoverypolicy, timestampwrapper, timestampwrapper, util

The ActiveMQ TimedSubscriptionRecoveryPolicy.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.broker.region.policy;

import java.util.ArrayList;
import java.util.Collections;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.List;
import org.apache.activemq.broker.Broker;
import org.apache.activemq.broker.ConnectionContext;
import org.apache.activemq.broker.region.MessageReference;
import org.apache.activemq.broker.region.SubscriptionRecovery;
import org.apache.activemq.broker.region.Topic;
import org.apache.activemq.command.ActiveMQDestination;
import org.apache.activemq.command.Message;
import org.apache.activemq.filter.DestinationFilter;
import org.apache.activemq.thread.Scheduler;

/**
 * This implementation of {@link SubscriptionRecoveryPolicy} will keep a timed
 * buffer of messages around in memory and use that to recover new
 * subscriptions.
 * 
 * @org.apache.xbean.XBean
 * 
 */
public class TimedSubscriptionRecoveryPolicy implements SubscriptionRecoveryPolicy {

    private static final int GC_INTERVAL = 1000;
    private Scheduler scheduler;
    
    // TODO: need to get a better synchronized linked list that has little
    // contention between enqueuing and dequeuing
    private final List<TimestampWrapper> buffer = Collections.synchronizedList(new LinkedList());
    private volatile long lastGCRun = System.currentTimeMillis();

    private long recoverDuration = 60 * 1000; // Buffer for 1 min.

    static class TimestampWrapper {
        public MessageReference message;
        public long timestamp;

        public TimestampWrapper(MessageReference message, long timestamp) {
            this.message = message;
            this.timestamp = timestamp;
        }
    }

    private final Runnable gcTask = new Runnable() {
        public void run() {
            gc();
        }
    };

    public SubscriptionRecoveryPolicy copy() {
        TimedSubscriptionRecoveryPolicy rc = new TimedSubscriptionRecoveryPolicy();
        rc.setRecoverDuration(recoverDuration);
        return rc;
    }

    public boolean add(ConnectionContext context, MessageReference message) throws Exception {
        buffer.add(new TimestampWrapper(message, lastGCRun));
        return true;
    }

    public void recover(ConnectionContext context, Topic topic, SubscriptionRecovery sub) throws Exception {
        // Re-dispatch the messages from the buffer.
        ArrayList<TimestampWrapper> copy = new ArrayList(buffer);
        if (!copy.isEmpty()) {
            for (Iterator<TimestampWrapper> iter = copy.iterator(); iter.hasNext();) {
                TimestampWrapper timestampWrapper = iter.next();
                MessageReference message = timestampWrapper.message;
                sub.addRecoveredMessage(context, message);
            }
        }
    }
    
    public void setBroker(Broker broker) {  
        this.scheduler = broker.getScheduler();
    }

    public void start() throws Exception {
        scheduler.executePeriodically(gcTask, GC_INTERVAL);
    }

    public void stop() throws Exception {
        scheduler.cancel(gcTask);
    }
    

    public void gc() {
        lastGCRun = System.currentTimeMillis();
        while (buffer.size() > 0) {
            TimestampWrapper timestampWrapper = buffer.get(0);
            if (lastGCRun > timestampWrapper.timestamp + recoverDuration) {
                // GC it.
                buffer.remove(0);
            } else {
                break;
            }
        }
    }

    public long getRecoverDuration() {
        return recoverDuration;
    }

    public void setRecoverDuration(long recoverDuration) {
        this.recoverDuration = recoverDuration;
    }

    public Message[] browse(ActiveMQDestination destination) throws Exception {
        List<Message> result = new ArrayList();
        ArrayList<TimestampWrapper> copy = new ArrayList(buffer);
        DestinationFilter filter = DestinationFilter.parseFilter(destination);
        for (Iterator<TimestampWrapper> iter = copy.iterator(); iter.hasNext();) {
            TimestampWrapper timestampWrapper = iter.next();
            MessageReference ref = timestampWrapper.message;
            Message message = ref.getMessage();
            if (filter.matches(message.getDestination())) {
                result.add(message);
            }
        }
        return result.toArray(new Message[result.size()]);
    }

}

Other ActiveMQ examples (source code examples)

Here is a short list of links related to this ActiveMQ TimedSubscriptionRecoveryPolicy.java source code file:

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