无法使activemq消费者出队

Question

I am creating a JMS chat application using activemq and spring boot. I am trying to send message from producer to multiple subscribers. I am able to send message ie message is en-queued. but in my receiver part message is unable to de-queue.` I am using the below code for communicating message from producer to multiple subscribers.

public class WelcomeController implements MessageListener {

    public static Boolean TRANSACTIONAL = false;
    public static String TOPIC_NAME = "firstTopic";

    public static String BROKER_URL = "tcp://localhost:61616";
    public static String BROKER_USERNAME = "admin";
    public static String BROKER_PASSWORD = "admin";


    public void createProducer() throws JMSException {
       Connection connection = null;
        Session session = null;
        try {
            ActiveMQConnectionFactory connectionFactory = new ActiveMQConnectionFactory();
            connectionFactory.setBrokerURL(BROKER_URL);
            connectionFactory.setPassword(BROKER_USERNAME);
            connectionFactory.setUserName(BROKER_PASSWORD);

            connection = connectionFactory.createConnection();
            connection.setClientID("CircliTopic");
            connection.start();
             session = connection.createSession(false, Session.AUTO_ACKNOWLEDGE);


            for (int i = 1; i <= 3; i++) {
               session = connection.createSession(TRANSACTIONAL,
                  Session.AUTO_ACKNOWLEDGE);
              Topic destination = session.createTopic(TOPIC_NAME);
              MessageProducer producer = session.createProducer(destination);
              TextMessage message = session.createTextMessage();
              message.setText( "My text message was send and received");//
                System.out.println("Sending text '" + message + "'");
                producer.send(message);
              MessageConsumer consumer = session
                  .createDurableSubscriber(destination, "Listener" + i);

              consumer.setMessageListener(new WelcomeController());

            }



        } finally {
            connection.close();
        }`
}

@Override
public void onMessage(Message message) {

     try {

          if (message instanceof TextMessage) {
            TextMessage text = (TextMessage) message;
            System.out.println(" - Consuming text msg: " + text.getText());
          } else if (message instanceof ObjectMessage) {
            ObjectMessage objmsg = (ObjectMessage) message;
            Object obj = objmsg.getObject();
            System.out.println(" - Consuming object msg: " + obj);
          } else {
            System.out.println(
                " - Unrecognized Message type " + message.getClass());
          }
        } catch (JMSException e) {
          e.printStackTrace();
        }

}

I am able to get consuming text message in my console but my message is not de-queued to the subscribers and also in my activemq server message is not dequeued.

Answer 1

You are creating a Topic subscription only after the message has been sent and that won't work because these are Topics and a Topic with no subscriptions simply discards all messages sent to it. You need to establish a durable Topic subscription prior to any messages being sent, or switch to Queues if your design allows as a Queue will store a message sent to it until consumed.

It is hard to say more without knowing your requirements but it seems you need to spend a little bit more time understanding how Topics work.