O'Reilly - Java Message Service

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Figure 8.3. Lifecycle of a message-driven bean Java Message Service The Retailer JMS client developed in Chapter 4 can easily be converted to a messagedriven bean. When messages are received from the wholesalers, RetailerMessageBean can process them quickly and efficiently, providing a more scalable option then the JMS clients we developed in Chapter 4: public class RetailerMessageBean implements javax.ejb.MessageDrivenBean, javax.jms.MessageListener { private javax.jms.QueueConnection connect = null; private javax.jms.QueueSession session = null; private javax.jms.QueueSender sender = null; private javax.jms.Queue buyQueue = null; public void setMessageDrivenContext(MessageDrivenContext mdc){ } public void ejbCreate( ){ try { InitialContext jndiEnc = new InitialContext( ); QueueConnectionFactory factory = (QueueConnectionFactory) jndiEnc.lookup("java:comp/env/jms/broker"); connect = factory.createQueueConnection( ); session = connect.createQueueSession (false,Session.AUTO_ACKNOWLEDGE); buyQueue = (Queue) jndiEnc.lookup("java:comp/env/jms/BuyQueue"); sender = session.createSender(buyQueue); connect.start( ); } catch (javax.jms.JMSException jmse){ throw new javax.ejb.EJBException( ); } catch (javax.naming.NamingException jne){ throw new javax.ejb.EJBException( ); } } public void ejbRemove( ){ try { connect.close( ); 130
} } catch (javax.jms.JMSException jmse){ throw new javax.ejb.EJBException( ); } } public void onMessage(javax.jms.Message aMessage){ try{ autoBuy(aMessage); } catch (java.lang.RuntimeException rte){ throw new javax.ejb.EJBException( ); } } private void autoBuy (javax.jms.Message message){ int count = 1000; try{ StreamMessage strmMsg = (StreamMessage)message; String dealDesc = strmMsg.readString( ); String itemDesc = strmMsg.readString( ); float oldPrice = strmMsg.readFloat( ); float newPrice = strmMsg.readFloat( ); System.out.println("Received Hot Buy :"+dealDesc); } // If price reduction is greater than 10 percent, buy if (newPrice == 0 || oldPrice / newPrice > 1.1){ System.out.println ("\nBuying " + count + " " + itemDesc); TextMessage textMsg = session.createTextMessage( ); textMsg.setText(count + " " + itemdesc ); sender.send( textMsg, javax.jms.DeliveryMode.PERSISTENT, javax.jms.Message.DEFAULT_PRIORITY, 1800000); } else { System.out.println ("\nBad Deal. Not buying"); } } catch (javax.jms.JMSException jmse){ jmse.printStackTrace( ); } Java Message Service The RetailerMessageBean uses the BuyQueue to publish buy orders. The QueueConnectionFactory and BuyQueue destination are obtained from the JNDI ENC. The RetailerMessageBean uses the factory and queue to create a QueueSender, but how does the bean subscribe to the HotDeals topic? Where is the code to set up the HotDeals subscription? A message-driven bean is, by definition, a JMS consumer. The EJB container in which the bean is deployed takes care of subscribing the bean to the desired topic or connecting it to the desired queue, based on JMS configuration information provided by the deployer. Like any other enterprise bean, message-driven beans have an XML deployment descriptor, which is used as a reference by the deployer. The deployment descriptor includes elements for describing the type of destination (topic or queue), whether to use durable or nondurable subscriptions with topics, the acknowledgment mode, and even the message selector used. In addition, the message-driven bean's deployment descriptor contains elements common to all beans, like those for specifying environment entries, bean references, resource connections, etc. This makes the beans very portable across vendors, as well as simplifying configuration. 131
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Java Message Service Richard Monson
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Chapter 7. Deployment Consideration
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Java Message Service Although this
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Java Message Service Examples devel
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Java Message Service Chapter 1. Und
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Java Message Service Before we disc
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Java Message Service to naming and
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1.3.1 Enterprise Application Integr
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Java Message Service Figure 1.5. Dy
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Java Message Service With J2EE, JSP
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Java Message Service recognition of
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TopicConnectionFactory conFactory =
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Java Message Service Before examini
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Understanding JNDI Java Message Ser
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Java Message Service The TopicConne
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protected void writeMessage(String
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Java Message Service When the Topic
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Java Message Service publishing a m
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Java Message Service Messages come
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3.1.1.3 JMSMessageID Java Message S
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3.2 Properties Java Message Service
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Java Message Service The following
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Notification of certain bids on inv
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Java Message Service When a consume
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UTF-8 Java Message Service UTF-8 en
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Java Message Service Table 3.1 show
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Java Message Service Essentially, M
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3.4.9 Interoperability and Portabil
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4.1.1 Running the B2B Application J
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jne.printStackTrace( ); System.exit
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try { Properties env = new Properti
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Java Message Service Once the Retai
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Java Message Service We can demonst
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Java Message Service publish( ) met
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Java Message Service The receive( )
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4.7 Unsubscribing Java Message Serv
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Java Message Service multiple consu
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import javax.jms.TopicConnectionFac
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} } try { System.out.println("\nRet
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TopicConnectionFactory tFactory = n
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public QWholesaler(String broker, S
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Page 90 and 91: 6.2.1 AUTO_ACKNOWLEDGE Java Message
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Page 104 and 105: } return; session.commit(); } else
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Page 108 and 109: XAResource jmsXA = session.getXARes
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Page 120 and 121: 7.2.5 The Bottom Line Java Message
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Page 130 and 131: 8.3 The JMS Resource in J2EE Java M
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Page 140 and 141: Java Message Service The FioranoMQ
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Page 144 and 145: 9.6.2 Next Version Java Message Ser
Page 146 and 147: A.1.2 Connection Java Message Servi
Page 148 and 149: A.1.8 JMSException Java Message Ser
Page 150 and 151: } public void setInt(String name, i
Page 152 and 153: } public Message receiveNoWait( ) t
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Page 156 and 157: A.2.6 QueueSender Java Message Serv
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Page 160 and 161: Appendix B. Message Headers Java Me
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Page 166 and 167: UTC Java Message Service UTC (Unive
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Page 176 and 177: JMSXAppID Java Message Service This
Page 178 and 179: Appendix D. Message Selectors Java
Page 180 and 181: The BETWEEN operator can be used to
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Colophon Java Message Service Our l
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