JMS Examples

The following sections discuss the basics needed to use the JBoss JMS implementation. JMS leaves the details of accessing JMS connection factories and destinations as provider-specific details. You need to know the following to use the JBossMQ layer:

The location of the queue and topic connect factories In JBoss both connection factory implementations are located under the JNDI name ConnectionFactory.
How to look up JMS destinations (queues and topics) Destinations are configured via MBeans, as you will see later in this chapter. JBoss comes with a few queues and topics preconfigured. You can find them under the jboss.mq.destination domain in the JMX Console.
Which JARS JMS requires These include concurrent.jar, jbossmq-client.jar, jboss-common-client.jar, jboss-system-client.jar, jnp-client.jar, and log4j.jar.

The following sections look at examples of the various JMS messaging models and message-driven beans. You can find the source for this chapter's examples under the src/main/org/jboss/chap6 directory of the book examples.

A Point-to-Point Example

Let's start out with a point-to-point (P2P) example. In the P2P model, a sender delivers messages to a queue, and a single receiver pulls the message off the queue. The receiver does not need to be listening to the queue at the time the message is sent. Listing 6.1 shows a complete P2P example that sends a javax.jms.TextMessage to the queue queue/testQueue and asynchronously receives the message from the same queue.

Listing 6.1. A P2P JMS Client Example

 package org.jboss.chap6.ex1; import javax.jms.JMSException; import javax.jms.Message; import javax.jms.MessageListener; import javax.jms.Queue; import javax.jms.QueueConnection; import javax.jms.QueueConnectionFactory; import javax.jms.QueueReceiver; import javax.jms.QueueSender; import javax.jms.QueueSession; import javax.jms.TextMessage; import javax.naming.InitialContext; import javax.naming.NamingException; import EDU.oswego.cs.dl.util.concurrent.CountDown; import org.apache.log4j.Logger; import org.jboss.util.ChapterExRepository; /**  * A complete JMS client example program that sends a  * TextMessage to a Queue and asynchronously receives the  * message from the same Queue.  *  * @author Scott.Stark@jboss.org  * @version $Revision: 1.4 $  */ public class SendRecvClient {     static Logger log;     static CountDown done = new CountDown(1);     QueueConnection conn;     QueueSession session;     Queue que;     public static class ExListener         implements MessageListener     {         public void onMessage(Message msg)         {             done.release();             TextMessage tm = (TextMessage) msg;             try {                 log.info("onMessage, recv text=" + tm.getText());             } catch(Throwable t) {                 t.printStackTrace();             }         }     }     public void setupPTP()         throws JMSException,                NamingException     {         InitialContext iniCtx = new InitialContext();         Object tmp = iniCtx.lookup("ConnectionFactory");         QueueConnectionFactory qcf = (QueueConnectionFactory) tmp;         conn = qcf.createQueueConnection();         que = (Queue) iniCtx.lookup("queue/testQueue");         session = conn.createQueueSession(false,                                           QueueSession.AUTO_ACKNOWLEDGE);         conn.start();     }     public void sendRecvAsync(String text)         throws JMSException,                NamingException     {         log.info("Begin sendRecvAsync");         // Set up the PTP connection, session         setupPTP();         // Set the async listener         QueueReceiver recv = session.createReceiver(que);         recv.setMessageListener(new ExListener());         // Send a text msg         QueueSender send = session.createSender(que);         TextMessage tm = session.createTextMessage(text);         send.send(tm);         log.info("sendRecvAsync, sent text=" + tm.getText());         send.close();         log.info("End sendRecvAsync");     }     public void stop()         throws JMSException     {         conn.stop();         session.close();         conn.close();     }     public static void main(String args[])         throws Exception     {         ChapterExRepository.init(SendRecvClient.class);         log = Logger.getLogger("SendRecvClient");         log.info("Begin SendRecvClient, now=" + System.currentTimeMillis());         SendRecvClient client = new SendRecvClient();         client.sendRecvAsync("A text msg");         client.done.acquire();         client.stop();         log.info("End SendRecvClient");         System.exit(0);     } }

You can run the client by using the following command line:

 [examples]$ ant -Dchap=chap6 -Dex=1p2p run-example ... run-example1p2p:      [java] [INFO,SendRecvClient] Begin SendRecvClient, now=1102808673386      [java] [INFO,SendRecvClient] Begin sendRecvAsync      [java] [INFO,SendRecvClient] onMessage, recv text=A text msg      [java] [INFO,SendRecvClient] sendRecvAsync, sent text=A text msg      [java] [INFO,SendRecvClient] End sendRecvAsync      [java] [INFO,SendRecvClient] End SendRecvClient

A Pub-Sub Example

The JMS publish/subscribe (pub-sub) message model is a one-to-many model. A publisher sends a message to a topic, and all active subscribers of the topic receive the message. Subscribers that are not actively listening to the topic will miss the published message. Listing 6.2 shows a complete JMS client that sends javax.jms.TextMessage to a topic and asynchronously receives the message from the same topic.

Listing 6.2. A Pub-Sub JMS Client Example

 package org.jboss.chap6.ex1; import javax.jms.JMSException; import javax.jms.Message; import javax.jms.MessageListener; import javax.jms.Topic; import javax.jms.TopicConnection; import javax.jms.TopicConnectionFactory; import javax.jms.TopicPublisher; import javax.jms.TopicSubscriber; import javax.jms.TopicSession; import javax.jms.TextMessage; import javax.naming.InitialContext; import javax.naming.NamingException; import EDU.oswego.cs.dl.util.concurrent.CountDown; /**  *  A complete JMS client example program that sends a TextMessage to  *  a Topic and asynchronously receives the message from the same  *  Topic.  *  *  @author Scott.Stark@jboss.org  *  @version $Revision: 1.4 $  */ public class TopicSendRecvClient {     static CountDown done = new CountDown(1);     TopicConnection conn = null;     TopicSession session = null;     Topic topic = null;     public static class ExListener implements MessageListener     {         public void onMessage(Message msg)         {             done.release();             TextMessage tm = (TextMessage) msg;             try {                 System.out.println("onMessage, recv text=" + tm.getText());             } catch(Throwable t) {                 t.printStackTrace();             }         }     }     public void setupPubSub()         throws JMSException, NamingException     {         InitialContext iniCtx = new InitialContext();         Object tmp = iniCtx.lookup("ConnectionFactory");         TopicConnectionFactory tcf = (TopicConnectionFactory) tmp;         conn = tcf.createTopicConnection();         topic = (Topic) iniCtx.lookup("topic/testTopic");         session = conn.createTopicSession(false,                                           TopicSession.AUTO_ACKNOWLEDGE);         conn.start();     }     public void sendRecvAsync(String text)         throws JMSException, NamingException     {         System.out.println("Begin sendRecvAsync");         // Setup the PubSub connection, session         setupPubSub();         // Set the async listener         TopicSubscriber recv = session.createSubscriber(topic);         recv.setMessageListener(new ExListener());         // Send a text msg         TopicPublisher send = session.createPublisher(topic);         TextMessage tm = session.createTextMessage(text);         send.publish(tm);         System.out.println("sendRecvAsync, sent text=" + tm.getText());         send.close();         System.out.println("End sendRecvAsync");     }     public void stop() throws JMSException     {         conn.stop();         session.close();         conn.close();     }     public static void main(String args[]) throws Exception     {         System.out.println("Begin TopicSendRecvClient, now=" +                            System.currentTimeMillis());         TopicSendRecvClient client = new TopicSendRecvClient();         client.sendRecvAsync("A text msg, now="+System.currentTimeMillis());         client.done.acquire();         client.stop();         System.out.println("End TopicSendRecvClient");         System.exit(0);     } }

You can run the client by using the following command line:

 [examples]$ ant -Dchap=chap6 -Dex=1ps run-example ... run-example1ps:      [java] Begin TopicSendRecvClient, now=1102809427043      [java] Begin sendRecvAsync      [java] onMessage, recv text=A text msg, now=1102809427071      [java] sendRecvAsync, sent text=A text msg, now=1102809427071      [java] End sendRecvAsync      [java] End TopicSendRecvClient

Now let's break the publisher and subscribers into separate programs to demonstrate that subscribers only receive messages while they are listening to a topic. Listing 6.3 shows a variation of the pub-sub client from Listing 6.2 that only publishes messages to the topic/testTopic topic. The subscriber client is shown in Listing 6.4.

Listing 6.3. A JMS Publisher Client

 package org.jboss.chap6.ex1; import javax.jms.JMSException; import javax.jms.Message; import javax.jms.MessageListener; import javax.jms.Topic; import javax.jms.TopicConnection; import javax.jms.TopicConnectionFactory; import javax.jms.TopicPublisher; import javax.jms.TopicSubscriber; import javax.jms.TopicSession; import javax.jms.TextMessage; import javax.naming.InitialContext; import javax.naming.NamingException; /**  *  A JMS client example program that sends a TextMessage to a Topic  *  *  @author Scott.Stark@jboss.org  *  @version $Revision: 1.4 $  */ public class TopicSendClient {     TopicConnection conn = null;     TopicSession session = null;     Topic topic = null;     public void setupPubSub()         throws JMSException, NamingException     {         InitialContext iniCtx = new InitialContext();         Object tmp = iniCtx.lookup("ConnectionFactory");         TopicConnectionFactory tcf = (TopicConnectionFactory) tmp;         conn = tcf.createTopicConnection();         topic = (Topic) iniCtx.lookup("topic/testTopic");         session = conn.createTopicSession(false,                                           TopicSession.AUTO_ACKNOWLEDGE);         conn.start();     }     public void sendAsync(String text)         throws JMSException, NamingException     {         System.out.println("Begin sendAsync");         // Set up the pub/sub connection, session         setupPubSub();         // Send a text msg         TopicPublisher send = session.createPublisher(topic);         TextMessage tm = session.createTextMessage(text);         send.publish(tm);         System.out.println("sendAsync, sent text=" +  tm.getText());         send.close();         System.out.println("End sendAsync");     }     public void stop()         throws JMSException     {         conn.stop();         session.close();         conn.close();     }     public static void main(String args[])         throws Exception     {         System.out.println("Begin TopicSendClient, now=" +                                    System.currentTimeMillis());         TopicSendClient client = new TopicSendClient();             client.sendAsync("A text msg, now="+System.currentTimeMillis());         client.stop();         System.out.println("End TopicSendClient");         System.exit(0);     } }

Listing 6.4. A JMS Subscriber Client

 package org.jboss.chap6.ex1; import javax.jms.JMSException; import javax.jms.Message; import javax.jms.MessageListener; import javax.jms.Topic; import javax.jms.TopicConnection; import javax.jms.TopicConnectionFactory; import javax.jms.TopicPublisher; import javax.jms.TopicSubscriber; import javax.jms.TopicSession; import javax.jms.TextMessage; import javax.naming.InitialContext; import javax.naming.NamingException; /**  * A JMS client example program that synchronously receives a message a Topic  *  * @author Scott.Stark@jboss.org  * @version $Revision: 1.4 $  */ public class TopicRecvClient {     TopicConnection conn = null;     TopicSession session = null;     Topic topic = null;     public void setupPubSub()         throws JMSException, NamingException     {         InitialContext iniCtx = new InitialContext();         Object tmp = iniCtx.lookup("ConnectionFactory");         TopicConnectionFactory tcf = (TopicConnectionFactory) tmp;         conn = tcf.createTopicConnection();         topic = (Topic) iniCtx.lookup("topic/testTopic");         session = conn.createTopicSession(false,                                           TopicSession.AUTO_ACKNOWLEDGE);         conn.start();     }     public void recvSync()         throws JMSException, NamingException     {         System.out.println("Begin recvSync");         // Set up the pub/sub connection, session         setupPubSub();         // Wait up to 5 seconds for the message         TopicSubscriber recv = session.createSubscriber(topic);         Message msg = recv.receive(5000);         if (msg == null) {             System.out.println("Timed out waiting for msg");         } else {             System.out.println("TopicSubscriber.recv, msgt="+msg);         }     }     public void stop()         throws JMSException     {         conn.stop();         session.close();         conn.close();     }     public static void main(String args[])         throws Exception     {         System.out.println("Begin TopicRecvClient, now=" +                            System.currentTimeMillis());         TopicRecvClient client = new TopicRecvClient();         client.recvSync();         client.stop();         System.out.println("End TopicRecvClient");         System.exit(0);     } }

You run TopicSendClient followed by TopicRecvClient as follows:

 [examples]$ ant -Dchap=chap6 -Dex=1ps2 run-example ... run-example1ps2:      [java] Begin TopicSendClient, now=1102810007899      [java] Begin sendAsync      [java] sendAsync, sent text=A text msg, now=1102810007909      [java] End sendAsync      [java] End TopicSendClient      [java] Begin TopicRecvClient, now=1102810011524      [java] Begin recvSync      [java] Timed out waiting for msg      [java] End TopicRecvClient

The output shows that the topic subscriber client (TopicRecvClient) fails to receive the message sent by the publisher due to a timeout.

An Example of a Pub-Sub with a Durable Topic

JMS supports a messaging model that is a cross between the P2P and pub-sub models. When a pub-sub client wants to receive all messages posted to the topic it subscribes to, even when it is not actively listening to the topic, it may achieve this behavior by using a durable topic. Let's look at a variation of the Listing 6.4 subscriber client that uses a durable topic to ensure that it receives all messages, including those published when the client is not listening to the topic. Listing 6.5 shows the durable topic client.

Listing 6.5. A Durable Topic JMS Client Example

 package org.jboss.chap6.ex1; import javax.jms.JMSException; import javax.jms.Message; import javax.jms.MessageListener; import javax.jms.Topic; import javax.jms.TopicConnection; import javax.jms.TopicConnectionFactory; import javax.jms.TopicPublisher; import javax.jms.TopicSubscriber; import javax.jms.TopicSession; import javax.jms.TextMessage; import javax.naming.InitialContext; import javax.naming.NamingException; /**  *  A JMS client example program that synchronously receives a message a Topic  *  *  @author Scott.Stark@jboss.org  *  @version $Revision: 1.4 $  */ public class DurableTopicRecvClient {     TopicConnection conn = null;     TopicSession session = null;     Topic topic = null;     public void setupPubSub()         throws JMSException, NamingException     {         InitialContext iniCtx = new InitialContext();         Object tmp = iniCtx.lookup("ConnectionFactory");         TopicConnectionFactory tcf = (TopicConnectionFactory) tmp;         conn = tcf.createTopicConnection("john", "needle");         topic = (Topic) iniCtx.lookup("topic/testTopic");         session = conn.createTopicSession(false,                                           TopicSession.AUTO_ACKNOWLEDGE);         conn.start();     }     public void recvSync()         throws JMSException, NamingException     {         System.out.println("Begin recvSync");         // Set up the pub/sub connection, session         setupPubSub();         // Wait up to 5 seconds for the message         TopicSubscriber recv = session.createDurableSubscriber(topic, "chap6-ex1dtps");         Message msg = recv.receive(5000);         if (msg == null) {             System.out.println("Timed out waiting for msg");         } else {             System.out.println("DurableTopicRecvClient.recv, msgt=" + msg);         }     }     public void stop()         throws JMSException     {         conn.stop();         session.close();         conn.close();     }     public static void main(String args[])         throws Exception     {         System.out.println("Begin DurableTopicRecvClient, now=" +                            System.currentTimeMillis());         DurableTopicRecvClient client = new DurableTopicRecvClient();         client.recvSync();         client.stop();         System.out.println("End DurableTopicRecvClient");         System.exit(0);     } }

Now you can run the previous topic publisher with the durable topic subscriber, as follows:

[View full width]
 [examples]$ ant -Dchap=chap6 -Dex=1psdt run-example ... run-example1psdt:      [java] Begin DurableTopicSetup      [java] End DurableTopicSetup      [java] Begin TopicSendClient, now=1102899834273      [java] Begin sendAsync      [java] sendAsync, sent text=A text msg, now=1102899834345      [java] End sendAsync      [java] End TopicSendClient      [java] Begin DurableTopicRecvClient, now=1102899840043      [java] Begin recvSync      [java] DurableTopicRecvClient.recv, msgt=SpyTextMessage {      [java] Header {      [java]    jmsDestination :  TOPIC.testTopic .DurableSubscription[clientId=DurableSubscriberExample name=chap6-ex1dtps selector=null]      [java]    jmsDeliveryMode : 2      [java]    jmsExpiration   : 0      [java]    jmsPriority     : 4      [java]    jmsMessageID    : ID:3-11028998375501      [java]    jmsTimeStamp    : 1102899837550      [java]    jmsCorrelationID: null      [java]    jmsReplyTo      : null      [java]    jmsType         : null      [java]    jmsRedelivered  : false      [java]    jmsProperties   : {}      [java]    jmsPropReadWrite: false      [java]    msgReadOnly     : true      [java]    producerClientId: ID:3      [java] }      [java] Body {      [java]    text            :A text msg, now=1102899834345      [java] }      [java] }      [java] End DurableTopicRecvClient

Items of note for the durable topic example include the following:

The TopicConnectionFactory creation in the durable topic client uses a username and password, and the TopicSubscriber creation is done via the createDurableSubscriber(Topic,String) method. This is a requirement of durable topic subscribers: The messaging server needs to know what client is requesting the durable topic and what the name of the durable topic subscription is. We will discuss the details of durable topic setup later in this chapter.
An org.jboss.chap6.DurableTopicSetup client is run prior to the TopicSendClient. The reason for this is that a durable topic subscriber must have registered a subscription at some point in the past in order for the messaging server to save messages. JBoss supports dynamic durable topic subscribers, and the DurableTopicSetup client simply creates a durable subscription receiver and then exits. This leaves an active durable topic subscriber on the topic/testTopic, and the messaging server knows that any messages posted to this topic must be saved for latter delivery.
The TopicSendClient does not change for the durable topic. The notion of a durable topic is a subscriber-only notion.
The DurableTopicRecvClient sees the message published to the topic/testTopic even though it was not listening to the topic at the time the message was published.

An Example of P2P with MDB

Listing 6.6 shows a message-driven bean (MDB) that transforms the TextMessages it receives and sends the transformed messages to the queue found in the incoming message JMSReplyTo header.

Listing 6.6. A `TextMessage`-Processing MDB

 package org.jboss.chap6.ex2; import javax.ejb.MessageDrivenBean; import javax.ejb.MessageDrivenContext; import javax.ejb.EJBException; import javax.jms.JMSException; import javax.jms.Message; import javax.jms.MessageListener; import javax.jms.Queue; import javax.jms.QueueConnection; import javax.jms.QueueConnectionFactory; import javax.jms.QueueSender; import javax.jms.QueueSession; import javax.jms.TextMessage; import javax.naming.InitialContext; import javax.naming.NamingException; /**  * An MDB that transforms the TextMessages it receives and sends the  * transformed messages to the Queue found in the incoming message  * JMSReplyTo header.  *  * @author Scott.Stark@jboss.org  * @version $Revision: 1.4 $  */ public class TextMDB     implements MessageDrivenBean, MessageListener {     private MessageDrivenContext ctx = null;     private QueueConnection conn;     private QueueSession session;     public TextMDB()     {         System.out.println("TextMDB.ctor, this="+hashCode());     }     public void setMessageDrivenContext(MessageDrivenContext ctx)     {         this.ctx = ctx;         System.out.println("TextMDB.setMessageDrivenContext, this=" +                            hashCode());     }     public void ejbCreate()     {         System.out.println("TextMDB.ejbCreate, this="+hashCode());         try {             setupPTP();         } catch (Exception e) {             throw new EJBException("Failed to init TextMDB", e);         }     }     public void ejbRemove()     {         System.out.println("TextMDB.ejbRemove, this="+hashCode());         ctx = null;         try {             if (session != null) {                 session.close();             }             if (conn != null) {                 conn.close();             }         } catch(JMSException e) {             e.printStackTrace();         }     }     public void onMessage(Message msg)     {         System.out.println("TextMDB.onMessage, this="+hashCode());         try {             TextMessage tm = (TextMessage) msg;             String text = tm.getText() + "processed by: "+hashCode();             Queue dest = (Queue) msg.getJMSReplyTo();             sendReply(text, dest);         } catch(Throwable t) {             t.printStackTrace();         }     }     private void setupPTP()         throws JMSException, NamingException     {         InitialContext iniCtx = new InitialContext();         Object tmp = iniCtx.lookup("java:comp/env/jms/QCF");         QueueConnectionFactory qcf = (QueueConnectionFactory) tmp;         conn = qcf.createQueueConnection();         session = conn.createQueueSession(false,                                           QueueSession.AUTO_ACKNOWLEDGE);         conn.start();     }     private void sendReply(String text, Queue dest)         throws JMSException     {         System.out.println("TextMDB.sendReply, this=" +                            hashCode() + ", dest="+dest);         QueueSender sender = session.createSender(dest);         TextMessage tm = session.createTextMessage(text);         sender.send(tm);         sender.close();     } }

The MDB ejb-jar.xml and jboss.xml deployment descriptors are shown in Listings 6.7 and 6.8, respectively.

Listing 6.7. The MDB `ejb-jar.xml` Descriptor

 <?xml version="1.0"?> <!DOCTYPE ejb-jar PUBLIC           "-//Sun Microsystems, Inc.//DTD Enterprise JavaBeans 2.0//EN"           "http://java.sun.com/dtd/ejb-jar_2_0.dtd"> <ejb-jar>     <enterprise-beans>         <message-driven>             <ejb-name>TextMDB</ejb-name>             <ejb-class>org.jboss.chap6.ex2.TextMDB</ejb-class>             <transaction-type>Container</transaction-type>             <acknowledge-mode>AUTO_ACKNOWLEDGE</acknowledge-mode>             <message-driven-destination>                 <destination-type>javax.jms.Queue</destination-type>             </message-driven-destination>             <res-ref-name>jms/QCF</res-ref-name>             <resource-ref>                 <res-type>javax.jms.QueueConnectionFactory</res-type>                 <res-auth>Container</res-auth>             </resource-ref>         </message-driven>     </enterprise-beans> </ejb-jar>

Listing 6.8. The MDB `jboss.xml` Descriptor

 <?xml version="1.0"?> <jboss>     <enterprise-beans>         <message-driven>             <ejb-name>TextMDB</ejb-name>             <destination-jndi-name>queue/B</destination-jndi-name>             <resource-ref>                 <res-ref-name>jms/QCF</res-ref-name>                 <jndi-name>ConnectionFactory</jndi-name>             </resource-ref>         </message-driven>     </enterprise-beans> </jboss>

Listing 6.9 shows a variation of the P2P client that sends several messages to the queue/B destination and asynchronously receives the messages as modified by TextMDB from Queue A.

Listing 6.9. A JMS Client That Interacts with `TextMDB`

 package org.jboss.chap6.ex2; import javax.jms.JMSException; import javax.jms.Message; import javax.jms.MessageListener; import javax.jms.Queue; import javax.jms.QueueConnection; import javax.jms.QueueConnectionFactory; import javax.jms.QueueReceiver; import javax.jms.QueueSender; import javax.jms.QueueSession; import javax.jms.TextMessage; import javax.naming.InitialContext; import javax.naming.NamingException; import EDU.oswego.cs.dl.util.concurrent.CountDown; /**  *  A complete JMS client example program that sends N TextMessages to  *  a Queue B and asynchronously receives the messages as modified by  *  TextMDB from Queue A.  *  *  @author Scott.Stark@jboss.org  *  @version $Revision: 1.4 $  */ public class SendRecvClient {     static final int N = 10;     static CountDown done = new CountDown(N);     QueueConnection conn;     QueueSession session;     Queue queA;     Queue queB;     public static class ExListener         implements MessageListener     {         public void onMessage(Message msg)         {             done.release();             TextMessage tm = (TextMessage) msg;             try {                 System.out.println("onMessage, recv text="+tm.getText());             } catch(Throwable t) {                 t.printStackTrace();             }         }     }     public void setupPTP()         throws JMSException, NamingException     {         InitialContext iniCtx = new InitialContext();         Object tmp = iniCtx.lookup("ConnectionFactory");         QueueConnectionFactory qcf = (QueueConnectionFactory) tmp;         conn = qcf.createQueueConnection();         queA = (Queue) iniCtx.lookup("queue/A");         queB = (Queue) iniCtx.lookup("queue/B");         session = conn.createQueueSession(false,                                           QueueSession.AUTO_ACKNOWLEDGE);         conn.start();     }     public void sendRecvAsync(String textBase)         throws JMSException, NamingException, InterruptedException     {         System.out.println("Begin sendRecvAsync");         // Set up the PTP connection, session         setupPTP();         // Set the async listener for queA         QueueReceiver recv = session.createReceiver(queA);         recv.setMessageListener(new ExListener());         // Send a few text msgs to queB         QueueSender send = session.createSender(queB);         for(int m = 0; m < 10; m ++) {             TextMessage tm = session.createTextMessage(textBase+"#"+m);             tm.setJMSReplyTo(queA);             send.send(tm);             System.out.println("sendRecvAsync, sent text=" + tm.getText());         }         System.out.println("End sendRecvAsync");     }     public void stop()         throws JMSException     {         conn.stop();         session.close();         conn.close();     }     public static void main(String args[])         throws Exception     {         System.out.println("Begin SendRecvClient,now=" +                            System.currentTimeMillis());         SendRecvClient client = new SendRecvClient();         client.sendRecvAsync("A text msg");         client.done.acquire();         client.stop();         System.exit(0);         System.out.println("End SendRecvClient");     } }

You can run the client as follows:

 [examples]$ ant -Dchap=chap6 -Dex=2 run-example ... run-example2:      [copy] Copying 1 file to /tmp/jboss-4.0.1/server/default/deploy      [echo] Waiting 5 seconds for deploy...      [java] Begin SendRecvClient, now=1102900541558      [java] Begin sendRecvAsync      [java] sendRecvAsync, sent text=A text msg#0      [java] sendRecvAsync, sent text=A text msg#1      [java] sendRecvAsync, sent text=A text msg#2      [java] sendRecvAsync, sent text=A text msg#3      [java] sendRecvAsync, sent text=A text msg#4      [java] sendRecvAsync, sent text=A text msg#5      [java] sendRecvAsync, sent text=A text msg#6      [java] sendRecvAsync, sent text=A text msg#7      [java] sendRecvAsync, sent text=A text msg#8      [java] sendRecvAsync, sent text=A text msg#9      [java] End sendRecvAsync      [java] onMessage, recv text=A text msg#0processed by: 12855623      [java] onMessage, recv text=A text msg#5processed by: 9399816      [java] onMessage, recv text=A text msg#9processed by: 6598158      [java] onMessage, recv text=A text msg#3processed by: 8153998      [java] onMessage, recv text=A text msg#4processed by: 10118602      [java] onMessage, recv text=A text msg#2processed by: 1792333      [java] onMessage, recv text=A text msg#7processed by: 14251014      [java] onMessage, recv text=A text msg#1processed by: 10775981      [java] onMessage, recv text=A text msg#8processed by: 6056676      [java] onMessage, recv text=A text msg#6processed by: 15679078

The corresponding JBoss server console output looks like this:

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 19:15:40,232 INFO  [EjbModule] Deploying TextMDB 19:15:41,498 INFO  [EJBDeployer] Deployed:file:/private/tmp/jboss-4.0.1/server/default /deploy/chap6-ex2.jar 19:15:45,606 INFO  [TextMDB] TextMDB.ctor, this=10775981 19:15:45,620 INFO  [TextMDB] TextMDB.ctor, this=1792333 19:15:45,627 INFO  [TextMDB] TextMDB.setMessageDrivenContext, this=10775981 19:15:45,638 INFO  [TextMDB] TextMDB.ejbCreate, this=10775981 19:15:45,640 INFO  [TextMDB] TextMDB.setMessageDrivenContext, this=1792333 19:15:45,640 INFO  [TextMDB] TextMDB.ejbCreate, this=1792333 19:15:45,649 INFO  [TextMDB] TextMDB.ctor, this=12855623 19:15:45,658 INFO  [TextMDB] TextMDB.setMessageDrivenContext, this=12855623 19:15:45,661 INFO  [TextMDB] TextMDB.ejbCreate, this=12855623 19:15:45,742 INFO  [TextMDB] TextMDB.ctor, this=8153998 19:15:45,744 INFO  [TextMDB] TextMDB.setMessageDrivenContext, this=8153998 19:15:45,744 INFO  [TextMDB] TextMDB.ejbCreate, this=8153998 19:15:45,763 INFO  [TextMDB] TextMDB.ctor, this=10118602 19:15:45,764 INFO  [TextMDB] TextMDB.setMessageDrivenContext, this=10118602 19:15:45,764 INFO  [TextMDB] TextMDB.ejbCreate, this=10118602 19:15:45,777 INFO  [TextMDB] TextMDB.ctor, this=9399816 19:15:45,779 INFO  [TextMDB] TextMDB.setMessageDrivenContext, this=9399816 19:15:45,779 INFO  [TextMDB] TextMDB.ejbCreate, this=9399816 19:15:45,792 INFO  [TextMDB] TextMDB.ctor, this=15679078 19:15:45,798 INFO  [TextMDB] TextMDB.setMessageDrivenContext, this=15679078 19:15:45,799 INFO  [TextMDB] TextMDB.ejbCreate, this=15679078 19:15:45,815 INFO  [TextMDB] TextMDB.ctor, this=14251014 19:15:45,816 INFO  [TextMDB] TextMDB.setMessageDrivenContext, this=14251014 19:15:45,817 INFO  [TextMDB] TextMDB.ejbCreate, this=14251014 19:15:45,829 INFO  [TextMDB] TextMDB.ctor, this=6056676 19:15:45,831 INFO  [TextMDB] TextMDB.setMessageDrivenContext, this=6056676 19:15:45,864 INFO  [TextMDB] TextMDB.ctor, this=6598158 19:15:45,903 INFO  [TextMDB] TextMDB.ejbCreate, this=6056676 19:15:45,906 INFO  [TextMDB] TextMDB.setMessageDrivenContext, this=6598158 19:15:45,906 INFO  [TextMDB] TextMDB.ejbCreate, this=6598158 19:15:46,236 INFO  [TextMDB] TextMDB.onMessage, this=12855623 19:15:46,238 INFO  [TextMDB] TextMDB.sendReply, this=12855623, dest=QUEUE.A 19:15:46,734 INFO  [TextMDB] TextMDB.onMessage, this=9399816 19:15:46,736 INFO  [TextMDB] TextMDB.onMessage, this=8153998 19:15:46,737 INFO  [TextMDB] TextMDB.onMessage, this=6598158 19:15:46,768 INFO  [TextMDB] TextMDB.sendReply, this=9399816, dest=QUEUE.A 19:15:46,768 INFO  [TextMDB] TextMDB.sendReply, this=6598158, dest=QUEUE.A 19:15:46,774 INFO  [TextMDB] TextMDB.sendReply, this=8153998, dest=QUEUE.A 19:15:46,903 INFO  [TextMDB] TextMDB.onMessage, this=10118602 19:15:46,904 INFO  [TextMDB] TextMDB.sendReply, this=10118602, dest=QUEUE.A 19:15:46,927 INFO  [TextMDB] TextMDB.onMessage, this=1792333 19:15:46,928 INFO  [TextMDB] TextMDB.sendReply, this=1792333, dest=QUEUE.A 19:15:47,002 INFO  [TextMDB] TextMDB.onMessage, this=14251014 19:15:47,007 INFO  [TextMDB] TextMDB.sendReply, this=14251014, dest=QUEUE.A 19:15:47,051 INFO  [TextMDB] TextMDB.onMessage, this=10775981 19:15:47,051 INFO  [TextMDB] TextMDB.sendReply, this=10775981, dest=QUEUE.A 19:15:47,060 INFO  [TextMDB] TextMDB.onMessage, this=6056676 19:15:47,061 INFO  [TextMDB] TextMDB.sendReply, this=6056676, dest=QUEUE.A 19:15:47,064 INFO  [TextMDB] TextMDB.onMessage, this=15679078 19:15:47,065 INFO  [TextMDB] TextMDB.sendReply, this=15679078, dest=QUEUE.A

Items of note in this example include the following:

The JMS client has no explicit knowledge that it is dealing with an MDB. The client simply uses the standard JMS APIs to send messages to a queue and receive messages from another queue.
The MDB declares whether it will listen to a queue or topic in the ejb-jar.xml descriptor. The name of the queue or topic must be specified using a jboss.xml descriptor. In this example, the MDB also sends messages to a JMS queue. MDBs may act as queue senders or topic publishers within their onMessage callback.
The messages received by the client include a "processed by: NNN" suffix, where NNN is the hashCode value of the MDB instance that processed the message. This shows that many MDBs may actively process messages posted to a destination. Concurrent processing is one of the benefits of MDBs.