OCT 1 Master of Information System Management Organizational Communications and Distributed Object Technologies Lecture 5: JMS

OCT 2 Master of Information System Management Java Message Service Introduced by Sun J2EE in 1999 See Chapter 10 of “Java Enterprise in a Nutshell” by Farley, Crawford and Flanagan Web Services, CORBA, and Java RMI use, by default, synchronous communications. In the synchronous approach, the client makes a call and waits for a response. This is an example of tight coupling. In this respect, JMS promotes loose coupling.

OCT 3 Master of Information System Management Java Message Service An API for performing asynchronous messaging. Uses the provider architecture. It is an abstraction API like JNDI and JDBC. Sits on top of Message Oriented Middleware (MOM). The MOM might be IBM MQ Series, Sonic MQ, Tibco EMS or Apache’s Active MQ. Microsoft has a non-JMS MOM called MSMQ. IBM’s WebSphere Application Server offers a JMS implementation that is reused by WebSphere ESB. The ESB adds features. We’ll be using the provider from Sun that is installed with Netbeans and Glassfish V2.

OCT 4 Master of Information System Management JMS Communications Point to point Asynchronous. Similar to . Guaranteed delivery. Publish Subscribe Asynchronous. Similar to a bulletin board or newsgroup (one to many). One publishes to a topic and many subscribe to a topic. Guarantees may be configured.

OCT 5 Master of Information System Management Main Players Messaging clients (produce and consume messages) Message destinations (to send and receive messages) A JMS Message Provider

OCT 6 Master of Information System Management Where Do The Players Live? Typically, JMS would be deployed within an enterprise. The enterprise has administrative control over the entire environment. It may be a centralized or decentralized deployment. In the decentralized case, queuing logic is distributed to clients. In the centralized case, queuing logic is centralized (hub and spoke). The provider may use TCP/IP, UDP/IP or IP multicasting.

OCT 7 Master of Information System Management JMS API from Sun’s Tutorial Connection Factory Connection Message Producer Session Message Consumer Destination Message Destination creates receives fromsends to creates

OCT 8 Master of Information System Management JMS API from Sun’s Tutorial Connection Factory Connection Message Producer Session Message Consumer Destination Message Destination creates receives fromsends to creates Subtypes provide implementations for different types of content.

OCT 9 Master of Information System Management JMS API from Sun’s Tutorial Connection Factory Connection Message Producer Session Message Consumer Destination Message Destination creates receives fromsends to creates Attach MessageListeners that implement the onMessage() method. Or, use a Message Driven Bean.

OCT 10 Master of Information System Management JMS API from Sun’s Tutorial Connection Factory Connection Message Producer Session Message Consumer Destination Message Destination creates receives fromsends to creates Perform a JNDI lookUp() for this administrated object. QueueConnection Factory or TopicConnection Factory Perform a JNDI lookUp() for this administrated object. Destination resources may be Queues or Topics.

OCT 11 Master of Information System Management JMS API from Sun’s Tutorial Connection Factory Connection Message Producer Session Message Consumer Destination Message Destination creates receives fromsends to creates A live connection to the provider. May be a QueueConnection or a TopicConnection Must be ‘started’ before receiving messages.

OCT 12 Master of Information System Management JMS API from Sun’s Tutorial Connection Factory Connection Message Producer Session Message Consumer Destination Message Destination creates receives fromsends to creates The producer writes. QueueSender or TopicPublisher The consumer retrieves. QueueReceiver TopicSubscriber

OCT 13 Master of Information System Management JMS API from Sun’s Tutorial Connection Factory Connection Message Producer Session Message Consumer Destination Message Destination creates receives fromsends to creates A single, serialized flow of messages between the client and a provider. This flow may be transacted. QueueSession or ToipcSession

OCT 14 Master of Information System Management Java Messaging Architecture (Centralized) Client Application Message Broker Client Application Client Application Client Application Client Application

OCT 15 Master of Information System Management Java Messaging Architecture Message Broker Client Application Client Application Broker located through JNDI. Establish a connection through a connection factory. Create sessions from the connection. Sessions have transactional characteristics and acknowledgement modes. Connection

OCT 16 Master of Information System Management JMS Transaction Message Broker Client Application Client Application Connections contain transacted sessions Begin transaction send M1 send M2 send M3 commit or rollback M1 M2 M3 Messages are staged by the broker until the commit. After commit the message may be delivered to other clients. Upon rollback, the messages are disposed.

OCT 17 Master of Information System Management JMS Acknowledgements Message Broker Client Application Client Application Connections contain sessions with acknowledgement modes. These are low level acknowldgements, not associated with replies that follow requests. M1 I got it!

OCT 18 Master of Information System Management JMS Acknowledgements Message Broker Client Application Client Application M1 I got it! AUTO_ACKNOWLEDGE If a synchronous client receives the message requested it informs the broker automatically. If an asynchronous client receives the message it informs the broker automatically. CLIENT_ACKNOWLEDGEMENT The client program is responsible for sending an acknowledgement to the broker. Call acknowledge() method on the message received.

OCT 19 Master of Information System Management JMS Between Organizations(1) JMS Message Broker Client Application JMS Bridge Products exist allowing these two brokers to talk. This degree of interconnectedness may be inappropriate. MQSeries Message Broker

OCT 20 Master of Information System Management JMS Between Organizations(2) JMS Message Broker Client Application Web Components may act as JMS clients. Servlet Client Application Browser Client HTTP

OCT 21 Master of Information System Management JMS Between Organizations(2) JMS Message Broker Client Application Web Components may act as JMS clients. In this case, a web services may expose methods to RPC style clients. Or, the web services may collect an XML document from the Web client and pass data to the JMS broker. This is less tightly coupled than connecting two JMS providers with a bridge. Web Service Client Application Web Client Using SOAP HTTP