Describe the concepts and some practical applications of messaging. Describe the concepts and basic structure of JMS.

Transcription

1 Overview Describe the concepts and some practical applications of messaging. Describe the concepts and basic structure of JMS. Write simple JMS messaging code using the publish and subscribe and point-to-point domains. Discuss advanced JMS issues such as guaranteed messaging, transactions, reliability, and recovery.

2 Part 1: Enterprise Messaging and JMS

3 Enterprise messaging Application A Application B Messaging API Messaging Clients - Oriented Middleware Messaging API Messaging Clients

4 Tightly Coupled RPC Business Application A RPC Client/ Business Application B RPC Client/ Business Application D RPC Client/ Requires n * (n-1) / 2 connections Business Application C RPC Client/

5 JMS messaging Centralized message server (hub and spoke) Decentralized message server (IP multicast) JMS Client JMS Client JMS Client Application A JMS Client Local "server" Router Local "server" Local "server" Local "server" JMS Client JMS Client JMS Client JMS Client JMS Client JMS Client Application B Application C Application D

6 The J2EE platform Client Application J2EE Platform EJB Container Web Container Application Client Container JMS JDBC Database

7 Part 2: JMS Concepts and Coding

8 Wholesaler and retailer Wholesaler Update price (publish) Order product (send) Retailer 1 Retailer 2

9 JMS features Standard Java API delivery modes Two messaging models Transactions Reliability levels Persistent messaging

10 JMS messaging domains Publish and subscribe Many consumers per message Point-to-point One consumer per message

11 Publisher Publish and subscribe: Supply chain management Topic Subscriber

12 Point-to-point: Order and fulfillment Sender Queue Receiver Need Supplies Goods Shipped

13 JMS components JMS Client Connection Session JMS Client Connection Session Producer Destination Consumer

14 Connections and sessions JMS Client Connection Session Session A connection connects to a message server. You can create one or more sessions within a connection. Session

15 Creating connections and sessions JMS Client ConnectionFactory JNDI Store ConnectionFactories Destinations create Connection Session Session Session

16 JMS message types type Text Object Map Stream Bytes body No body A standard Java string A serializable Java object A set of name/value pairs where values are Java primitives A stream of Java primitives A stream of uninterpreted bytes

17 Creating a message TopicSession createstream( ); QueueSession Stream createtext( ); Text

18 JMS message headers Automatically assigned headers JMSDestination JMSDeliveryMode JMSID JMSTimestamp JMSExpiration JMSRedelivered JMSPriority Developer-assigned headers JMSReplyTo JMSCorrelationID JMSType

19 Producers, consumers, and destinations Producer Consumer Bind to destination Bind to destination Read message Send message Destination Consume message

20 Creating destinations JNDI Store JMS Client ConnectionFactories Destinations lookup Topic Queue

21 Producing a message Session create message create Destination Producer produce message

22 Consuming messages Incoming messages acknowledge Incoming messages Listener on(message); acknowledge Consumer receive();

23 Asynchronous message delivery Incoming messages Listener on(message); acknowledge

24 Using receive( ) Incoming messages Consumer receive(); acknowledge

25 Filtering with message selector Publisher Departments.Sales JMSPriority = 2 Pipeline = Subscriber Departments.Sales Pipeline > delivered not delivered Subscriber Departments.Sales Pipeline > Subscriber Departments.Sales JMSPriority > 5 not delivered delivered Subscriber Departments.Sales JMSPriority >= 2 AND Pipeline > 10000

26 Browsing a queue QueueBrowser 1 getenumeration(); 2 Enumeration nextelement(); 3 4

27 Accessing message content get<type>(name); Map Text Object Stream Bytes gettext(); getobject(); read<type>();

28 Part 3: Guaranteed messaging

29 Guaranteeing message delivery Producer PERSISTENT message Acknowledge message Durable Subscriber Or QueueReceiver Persistent store removed after acknowledgment

30 Persistent and non-persistent messages Non-persistent message not guaranteed to survive provider failure Persistent message guaranteed to survive provider failure Persistent store

31 Acknowledgement modes AUTO Consumer I got another message! It might be easy for you to tell me that for every message, but you are using a lot of bandwidth. CLIENT I received all messages up to this point. Where have you been? I have been waiting to delete 50 messages. DUPS_OK Okay, I might seem lazy to you, but it is not important to me if there are some duplicates. When you are lazy like this, I might have to deliver some messages more than once.

32 Durable subscribers Publisher PERSISTENT message Durable Subscriber1 (connected) Undelivered messages delivered to Subscriber2 when reconnected Persistent store Durable Subscriber2 (not connected)

33 Redelivered messages Before message server receives acknowledgement: server has failed and restarted OR Consumer has failed and restarted Consumer JMSRedelivered=true

34 Part 4: Transactions and recovery

35 Transacted session: Producer Before commit( ) Producer Transacted session Upon commit( ) Consumer

36 Transacted session: Consumer Before commit( ) 1 Deliver messages Consumer 2 Consume messages Upon commit( ) 2 Delete messages if all recipients have acknowledged Acknowledge messages 1 Consumer

37 Distributed transaction support JMS Client XAConnectionFactory JNDI Store ConnectionFactories Destinations create XAConnection XASession XASession XASession

38 Recovering from a lost connection Client runtime ExceptionListener Reconnect onexception()

39 Understanding the Java Service: Conclusion