Message Group Example

To run the example, simply type mvn verify from this directory, 
or mvn -PnoServer verify if you want to start and create the server manually.

This example shows you how to configure and use message groups via a connection factory with ActiveMQ Artemis.

Message groups are sets of messages that has the following characteristics:

You can make any message belong to a message group by setting a 'group-id' on the connection factory. All producers created via this connection factory will set that group id on its messages. In this example we set the group id 'Group-0'on a connection factory and send messages via 2 different producers and check that only 1 consumer receives them.

Alternatively, ActiveMQ's connection factories can be configured to auto group messages. By setting autogroup to true on the ActiveMQConnectionFactory (or setting <autogroup>true</autogroup> in activemq-jms.xml's connection factory settings), a random unique id will be picked to create a message group. Every messages sent by a producer created from this connection factory will automatically be part of this message group.

Example step-by-step

1. First we need to get an initial context so we can look-up the JMS connection factory and destination objects from JNDI. This initial context will get it's properties from the client-jndi.properties file in the directory ../common/config

           InitialContext initialContext = getContext();
        

2. We look-up the JMS queue object from JNDI

           Queue queue = (Queue) initialContext.lookup("/queue/exampleQueue");
        

3. We look-up the JMS connection factory object from JNDI

           ConnectionFactory cf = (ConnectionFactory) initialContext.lookup("/ConnectionFactory");
        

4. We create a JMS connection

           connection = cf.createConnection();
        

5. We create a JMS session. The session is created as non transacted and will auto acknowledge messages.

           Session session = connection.createSession(false, Session.AUTO_ACKNOWLEDGE);
        

6. We create 2 JMS message producers on the session. This will be used to send the messages.

          
              MessageProducer producer1 = session.createProducer(queue);

              MessageProducer producer2 = session.createProducer(queue);
       

7. We create two consumers.

           
          MessageConsumer consumer1 = session.createConsumer(queue);
          consumer1.setMessageListener(new SimpleMessageListener("consumer-1"));
          MessageConsumer consumer2 = session.createConsumer(queue);
          consumer2.setMessageListener(new SimpleMessageListener("consumer-2"));
          
        

8. We create and send 10 text messages using each producer

           
         int msgCount = 10;
         for (int i = 0; i < msgCount; i++)
         {
            TextMessage m = session.createTextMessage("producer1 message " + i);
            producer1.send(m);
            System.out.println("Sent message: " + m.getText());
            TextMessage m2 = session.createTextMessage("producer2 message " + i);
            producer2.send(m2);
            System.out.println("Sent message: " + m2.getText());
         }
           
        

9. We start the connection.

           connection.start();
        

10. We check the group messages are received by only one consumer

           
            String trueReceiver = messageReceiverMap.get("producer1 message " + 0);
            for (int i = 0; i < msgCount; i++)
            {
               String receiver = messageReceiverMap.get("producer1 message " + i);
               if (!trueReceiver.equals(receiver))
               {
                  System.out.println("Group message [producer1 message " + i + "] went to wrong receiver: " + receiver);
                  result = false;
               }
               receiver = messageReceiverMap.get("producer2 message " + i);
               if (!trueReceiver.equals(receiver))
               {
                  System.out.println("Group message [producer2 message " + i + "] went to wrong receiver: " + receiver);
                  result = false;
               }
            }

           
        

11. And finally, always remember to close your JMS connections and resources after use, in a finally block. Closing a JMS connection will automatically close all of its sessions, consumers, producer and browser objects

           finally
           {
              if (initialContext != null)
              {
                initialContext.close();
              }
              if (connection != null)
              {
                 connection.close();
              }
           }
        

More information

• User Manual's Message Grouping chapter