JMS Topic Selector Example 1

This example shows how messages can be consumed from a topic using Message Selectors.

Consumers (or Subscribers) will only consume messages routed to a topic that match the provided selector

Topics and selectors are a standard part of JMS, please consult the JMS 1.1 specification for full details.

Example step-by-step

To run the example, simply type mvn verify -Pexample from this directory

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 = getContext();
        

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

           Topic topic = (Topic) initialContext.lookup("/topic/exampleTopic");
        

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 a JMS message producer on the session. This will be used to send the messages.

          MessageProducer messageProducer = session.createProducer(topic);
        

7. Create one non-durable subscriber with a specific filter

         MessageConsumer messageConsumer1 = session.createConsumer(topic, "someID=1", false);
        

8. Create a second non-durable subscriber with a specific filter

         MessageConsumer messageConsumer2 = session.createConsumer(topic, "someID=2", false);
        

9. Create a third non-durable subscriber without any filters, and it should receive the complete set of messages

         MessageConsumer messageConsumer3 = session.createConsumer(topic, "someID=2", false);
        

10. Send 20 messages, 10 with someID=1, 10 with someID=2

         for (int i = 1; i < 10; i++)
         {
            for (int someID = 1; someID <= 2; someID++)
            {
               TextMessage message1 = session.createTextMessage("This is a text message " + i +
                                                                " sent for someID=" +
                                                                someID);

               message1.setIntProperty("someID", someID);

               producer.send(message1);

               System.out.println("Sent message: " + message1.getText());
            }
         }

11. We start the connection. In order for delivery to occur on any consumers or subscribers on a connection, the connection must be started

           connection.start();
        

12. Consume the messages from MessageConsumer1, filtering out someID=2

         for (;;)
         {
            TextMessage messageReceivedA = (TextMessage)messageConsumer1.receive(1000);
            if (messageReceivedA == null)
            {
               break;
            }

            System.out.println("messageConsumer1 received " + messageReceivedA.getText() +
                               " someID = " +
                               messageReceivedA.getIntProperty("someID"));
         }

13. Consume the messages from MessageConsumer2, filtering out someID=1

        for (;;)
         {
            TextMessage messageReceivedB = (TextMessage)messageConsumer2.receive(1000);
            if (messageReceivedB == null)
            {
               break;
            }

            System.out.println("messageConsumer2 received " + messageReceivedB.getText() +
                               " someID = " +
                               messageReceivedB.getIntProperty("someID"));
         }

14. Consume the messages from MessageConsumer3, receiving the complete set of messages

         for (;;)
         {
            TextMessage messageReceivedC = (TextMessage)messageConsumer3.receive(1000);
            if (messageReceivedC == null)
            {
               break;
            }
            System.out.println("messageConsumer3 received " + messageReceivedC.getText() +
                               " someID = " +
                               messageReceivedC.getIntProperty("someID"));
         }

15. Close the consumers

subscriberA.close();

subscriberB.close();

16. Delete the subscriptions when you're done

session.unsubscribe("sub-a1");

session.unsubscribe("sub-a2");

17. 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();
              }
           }