Creating a Durable Topic Subscription

Introduction

Durable topics keep messages persistently until a suitable consumer is available to consume them. Durable topic subscribers are used when an application needs to receive messages that are published even while the application is inactive. See Managing Durable Topic Subscriptions for more information.

Prerequisites

See Prerequisites to Run the MB Samples for a list of prerequisites.

Building the sample

The <MB_HOME>/Samples/DurableTopicSubscriber/src/org/sample/jms directory has the following classes.

DurableTopicSubscriber.java creates a durable topic subscription named mySub1. The configuration of this file is as follows.

/*
*  Copyright (c) 2005-2010, WSO2 Inc. (http://www.wso2.org) All Rights Reserved.
*
*  WSO2 Inc. 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.sample.jms;
import javax.jms.*;
import javax.naming.Context;
import javax.naming.InitialContext;
import java.util.Properties;
public class DurableTopicSubscriber {
    public static final String ANDES_ICF = "org.wso2.andes.jndi.PropertiesFileInitialContextFactory";
    private static final String CF_NAME_PREFIX = "connectionfactory.";
    private static final String CF_NAME = "andesConnectionfactory";
    String userName = "admin";
    String password = "admin";
    private static String CARBON_CLIENT_ID = "carbon";
    private static String CARBON_VIRTUAL_HOST_NAME = "carbon";
    private static String CARBON_DEFAULT_HOSTNAME = "localhost";
    private static String CARBON_DEFAULT_PORT = "5672";
    private String topicName = "newTopic";
    private String subscriptionId = "mySub1";
    private boolean useListener = true;
    private int delayBetMessages = 200;
    private int messageCount = 10;
    private SampleMessageListener messageListener;
    private TopicConnection topicConnection;
    private TopicSession topicSession;
    private TopicSubscriber topicSubscriber;
    public void subscribe() {
        try {
            System.out.println("Starting the subscriber");
            Properties properties = new Properties();
            properties.put(Context.INITIAL_CONTEXT_FACTORY, ANDES_ICF);
            properties.put(CF_NAME_PREFIX + CF_NAME, getTCPConnectionURL(userName, password));
            properties.put("topic." + topicName, topicName);
            InitialContext ctx = new InitialContext(properties);
            // Lookup connection factory
            TopicConnectionFactory connFactory = (TopicConnectionFactory) ctx.lookup(CF_NAME);
            topicConnection = connFactory.createTopicConnection();
            topicConnection.start();
            topicSession =
                    topicConnection.createTopicSession(false, QueueSession.AUTO_ACKNOWLEDGE);
            // create durable subscriber with subscription ID
            Topic topic = (Topic) ctx.lookup(topicName);
            topicSubscriber = topicSession.createDurableSubscriber(topic, subscriptionId);
            if (!useListener) {
                for (int count = 0; count < messageCount; count++) {
                    Message message = topicSubscriber.receive();
                    System.out.println("count = " + count);
                    if (message instanceof TextMessage) {
                        TextMessage textMessage = (TextMessage) message;
                        System.out.println(count + ". textMessage.getText() = " + textMessage.getText());
                    }
                    if (delayBetMessages != 0) {
                        Thread.sleep(delayBetMessages);
                    }
                }
                topicConnection.close();
            } else {
                messageListener = new SampleMessageListener(delayBetMessages);
                topicSubscriber.setMessageListener(messageListener);
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
    public String getTCPConnectionURL(String username, String password) {
        return new StringBuffer()
                .append("amqp://").append(username).append(":").append(password)
                .append("@").append(CARBON_CLIENT_ID)
                .append("/").append(CARBON_VIRTUAL_HOST_NAME)
                .append("?brokerlist='tcp://").append(CARBON_DEFAULT_HOSTNAME).append(":").append(CARBON_DEFAULT_PORT).append("'")
                .toString();
    }
    public void stopSubscriber() throws JMSException {
        topicSubscriber.close();
        topicSession.close();
        topicConnection.close();
        System.out.println("Closing Subscriber");
    }
}

SampleMessageListener.java creates a consumer for the durable topic subscription. The configuration of this file is as follows.

/*
 * Copyright 2004,2005 The Apache Software Foundation.
 *
 * Licensed 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.sample.jms;
import javax.jms.*;
public class SampleMessageListener implements MessageListener {
    private int delay = 0;
    private int currentMsgCount = 0;
    public SampleMessageListener(int delay) {
        this.delay = delay;
    }
    public void onMessage(Message message) {
        TextMessage receivedMessage = (TextMessage) message;
        try {
            System.out.println("Got the message ==> " + (currentMsgCount+1) + " - "+ receivedMessage.getText());
            currentMsgCount++;
            if(delay != 0) {
                try {
                    Thread.sleep(delay);
                } catch (InterruptedException e) {
                    //silently ignore
                }
            }
        } catch (JMSException e) {
            e.printStackTrace();
        }
    }
}

TopicPublisher.java creates a publisher to publish messages in the durable topic. The configuration of this file is as follows.

Main.java defines the method for calling the three clients mentioned above. The configuration of this file is as follows.

/*
*  Copyright (c) 2005-2010, WSO2 Inc. (http://www.wso2.org) All Rights Reserved.
*
*  WSO2 Inc. 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.sample.jms;
import javax.jms.JMSException;
import javax.jms.MessageConsumer;
import javax.naming.NamingException;

public class Main {
    public static void main(String[] args) throws NamingException, JMSException, InterruptedException {
        DurableTopicSubscriber durableTopicSubscriber = new DurableTopicSubscriber();
        durableTopicSubscriber.subscribe();
        TopicPublisher topicPublisher = new TopicPublisher();
        topicPublisher.publishMessage(5);
        Thread.sleep(5000);
        durableTopicSubscriber.stopSubscriber();
        TopicPublisher topicPublisher2 = new TopicPublisher();
        topicPublisher2.publishMessage(5);
        Thread.sleep(5000);
        DurableTopicSubscriber durableTopicSubscriber2 = new DurableTopicSubscriber();
        durableTopicSubscriber2.subscribe();
        TopicPublisher topicPublisher3 = new TopicPublisher();
        topicPublisher3.publishMessage(5);
        Thread.sleep(5000);
        durableTopicSubscriber2.stopSubscriber();
    }
}

Executing the sample

Run the ant command from the <MB_Home>/samples/DurableTopicSubscriber directory.

Analyzing the output

The scenario used in this sample to demonstrate durable topic subscriptions is as follows.

durableTopicSubscriber is run to create a durable topic subscriber.
5 messages are sent to the myTopic topic. The messages will be received and printed by the subscriber named durableTopicSubscriber.
The durableTopicSubscriber is stopped.
The publisher is run again and 5 more messages are sent.
While running durableTopicSubscriber again, 5 different messages are sent to the same topic. You will see that all 10 messages (including the messages sent to the topic when the subscriber was absent) are consumed by the durableTopicSubscriber.