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4.1.1 Running the B2B Application Java Message Service Before looking at the code, let's look at how the application works. As with the Chat application, the Wholesaler class includes a main( ) method so it can be run as a standalone Java application. It's executed from the command line as follows: java chap4.B2B.Wholesaler localhost username password username and password are the authentication information for the client. The Retailer class can be executed in the same manner: java chap4.B2B.Retailer localhost username password Start your JMS server, then run one instance of a Wholesaler client and a Retailer client in separate command windows. In the Wholesaler client you are prompted to enter an item description, an old price, and a new price. Enter the following as shown: Bowling Shoes, 100.00, 55.00 Upon hitting the Enter key, you should see the Retailer application display information on the screen indicating that it has received a price change notice. You should then see the Wholesaler indicating that it has received a "buy" order from the Retailer. Here's the complete interaction with the Wholesaler and the Retailer: [1] [1] WHOLESALER and RETAILER are usernames you have set up when configuring your JMS server. passwd1 and passwd2 are the passwords you've assigned to those usernames. If you are using an evaluation version of a JMS provider, it may not be necessary to set up usernames and passwords; check your vendor's documentation for more information. java chap4.B2B.Wholesaler localhost WHOLESALER passwd1 Enter: Item, Old Price, New Price e.g., Bowling Shoes, 100.00, 55.00 Bowling Shoes, 100.00, 55.00 Order received - 1000 Bowling Shoes from DurableRetailer ----------------------- java chap4.B2B.Retailer localhost RETAILER passwd2 Retailer application started. Received Hot Buy: Bowling Shoes, 100.00, 55.00 Buying 1000 Bowling Shoes Here's what happened. The Wholesaler publishes a price quotation on a topic, "Hot Deals," which is intended for one or more Retailers. The Retailers subscribe to the "Hot Deals" topic in order to receive price quotes. The Retailer application has no interaction with a live user. Instead, it has an autoBuy( ) method that examines the old price and the new price. If the new price represents a reduction of greater than ten percent, the Retailer sends a message back to the Wholesaler on the "Buy Order" topic, telling it to purchase 1,000 items. In JMS terms, the Wholesaler is a producer of the "Hot Deals" topic and a consumer of the "Buy Order" topic. Conversely, the Retailer is a consumer of the "Hot Deals" topic and a producer of the "Buy Order" topic, as illustrated in Figure 4.1. 54
4.1.2 The B2B Source Code Figure 4.1. Producers and consumers in the B2B example Java Message Service The rest of this chapter examines the source code for the Wholesaler and Retailer classes, and covers several advanced subjects related to the pub/sub messaging model. 4.1.2.1 The Wholesaler class After the listing, we will take a brief tour of the methods in this class, and discuss their responsibilities. We will go into detail about the implementation later in this chapter. Now, here is the complete definition of the Wholesaler class, which is responsible for publishing items to the "Hot Deals" topic and receiving "Buy Orders" on those deals from retailers: public class Wholesaler implements javax.jms.MessageListener{ private javax.jms.TopicConnection connect = null; private javax.jms.TopicSession pubSession = null; private javax.jms.TopicSession subSession = null; private javax.jms.TopicPublisher publisher = null; private javax.jms.TopicSubscriber subscriber = null; private javax.jms.Topic hotDealsTopic = null; private javax.jms.TemporaryTopic buyOrdersTopic = null; public Wholesaler(String broker, String username, String password){ try { Properties env = new Properties( ); // ... specify the JNDI properties specific to the vendor InitialContext jndi = new InitialContext(env); TopicConnectionFactory factory = (TopicConnectionFactory)jndi.lookup(broker); connect = factory.createTopicConnection (username, password); pubSession = connect.createTopicSession(false,Session.AUTO_ACKNOWLEDGE); subSession = connect.createTopicSession(false,Session.AUTO_ACKNOWLEDGE); hotDealsTopic = (Topic)jndi.lookup("Hot Deals"); publisher = pubSession.createPublisher(hotDealsTopic); buyOrdersTopic = subSession.createTemporaryTopic( ); subscriber = subSession.createSubscriber(buyOrdersTopic); subscriber.setMessageListener(this); connect.start( ); } catch (javax.jms.JMSException jmse){ jmse.printStackTrace( ); System.exit(1); } catch (javax.naming.NamingException jne){ 55
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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 A vendor may h
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7.2.5 The Bottom Line Java Message
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Chapter 8. J2EE, EJB, and JMS 8.1 J
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Java Message Service JNDI ENC. In a
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8.3 The JMS Resource in J2EE Java M
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Figure 8.3. Lifecycle of a message-
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Java Message Service The FioranoMQ
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Java Message Service The iBus//Mobi
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9.6.2 Next Version Java Message Ser
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A.1.2 Connection Java Message Servi
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A.1.8 JMSException Java Message Ser
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} public Message receiveNoWait( ) t
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} public void writeInt(int value) t
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A.2.6 QueueSender Java Message Serv
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} throws JMSException; public Conne
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Appendix B. Message Headers Java Me
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Java Message Service are delivered
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Java Message Service JMSTimestamp P
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UTC Java Message Service UTC (Unive
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JMSXAppID Java Message Service This
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Appendix D. Message Selectors Java
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The BETWEEN operator can be used to
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D.5 Declaring a Message Selector Ja
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