The document discusses Java Message Service (JMS) which provides a common interface for sending messages between two or more clients. It covers JMS concepts like producers, consumers, queues and topics. It also describes the different message types and the typical algorithm for using JMS including obtaining connections and creating producers/consumers. Additionally, it shows how to implement synchronous and asynchronous messaging and how to use JMS within Spring applications including configuration, message listeners and templates.

1. JMS
java messaging
service
bolkimen@yahoo.com

2. General concepts
Producer/Publisher Consumer/Subscriber
QueueTopic
Message > JMS Message >
provider
...
...

3. Queues
Producer Consumer
Queue

4. Topics
Producer Topic Consumer

5. Message types
JMS specification provides standard implementations of javax.jms.Message:
1. javax.jms.BytesMessage - array of bytes
2. javax.jms.MapMessage - key-value pairs
3. javax.jms.ObjectMessage - serialized Java object
4. javax.jms.StreamMessage - stream of Java primitive values
5. javax.jms.TextMessage - Java String object (used for XML)

6. The working algorithm with JMS
1. Obtain a javax.jms.ConnectionFactory using a JNDI lookup. (The default ConnectionFactory
names are different depending on the JMS provider.)
2. Obtain a javax.jms.Connection from the ConnectionFactory.
3. Obtain a javax.jms.Session from the Connection.
4. Create a javax.jms.MessageProducer or javax.jms.MessageConsumer from the Session.
5. For a MessageProducer, send the message, or for a MessageConsumer, receive the message
(synchronous) or set the message listener (asynchronous).
6. Start the Connection to start message delivery.
7. Ultimately close the Connection.

7. Synchronous messaging
while(true) {
Message message = consumer.receive();
....
}

8. Asynchronous messaging
(listener class)
class AsyncConsumerMessageListener implements MessageListener {
public void onMessage(Message message) {
TextMessage msg = (TextMessage) message;
....
}
}

9. Asynchronous messaging
(listener class usage)
AsyncConsumerMessageListener asyncConsumer = new AsyncConsumerMessageListener();
MessageConsumer consumer = session.createConsumer(destination);
consumer.setMessageListener(asyncConsumer);

10. Spring
amqConnectionFactory
<bean id="amqConnectionFactory" class="org.apache.activemq.ActiveMQConnectionFactory">
<property name="brokerURL" value="${jms.url}" />
</bean>
1) jms.url=tcp://localhost:61616
2) jms.url=vm://localhost

11. Spring
jmsQueueConnectionFactory
<bean id="jmsQueueConnectionFactory"
class="org.springframework.jms.connection.SingleConnectionFactory">
<property name="targetConnectionFactory" ref="amqConnectionFactory" />
</bean>

12. Spring
listener-container
<jms:listener-container
connection-factory="jmsQueueConnectionFactory"
destination-type="queue" container-type="default">
<jms:listener
destination="TESTQUEUE"
ref="webConsumer"
method="onMessage" />
</jms:listener-container>

13. Spring
jmsTemplate
<bean id="jmsTemplate" class="org.springframework.jms.core.JmsTemplate">
<constructor-arg ref="jmsQueueConnectionFactory" />
</bean>

14. Spring
message listener
@Component
public class WebConsumer implements MessageListener
{
public void onMessage( final Message message ) {…}
}

15. Spring
producer
@Component
public class WebProducer
{
@Autowired
private JmsTemplate jmsTemplate;
public void send(String message) throws JMSException
{
jmsTemplate.convertAndSend("TESTQUEUE", message);
}
}

16. Sources & useful links
1. Official JMS tutorial book
2. http://www.thirdeyeconsulting.com/indyjug/jms/jms.html
3. http://www2.sys-con.com/itsg/virtualcd/Java/archives/0604/chappell/index.html