Organizational Communications and Distributed Object Technologies

95-702 OCT1Master of Information System

Management

Organizational Communications and Distributed Object Technologies

Lecture 5: JMS


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.


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.


Management

JMS Communications• Point to point Asynchronous. Similar to email. 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.


Management

Main Players

• Messaging clients (produce and consume messages)

• Message destinations (to send and receive messages)

• A JMS Message Provider


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.


Management

JMS API from Sun’s Tutorial

Connection Factory

Connection

Message Producer Session Message Consumer

Destination Message Destination

creates

creates

receives fromsends to creates

creates


Management


Connection Factory

Connection



creates

creates


creates

Subtypes provide implementationsfor different types of content.


Management


Connection Factory

Connection



creates

creates


creates

Attach MessageListenersthat implement the onMessage()method. Or, usea Message DrivenBean.


Management


Connection Factory

Connection



creates

creates


creates

Perform a JNDI lookUp()for this administratedobject.

QueueConnectionFactory or TopicConnectionFactory

Perform a JNDI lookUp()for this administratedobject.

Destination resources maybe Queues or Topics.


Management


Connection Factory

Connection



creates


creates

A live connection to theprovider.

May be a QueueConnection or aTopicConnection

Must be ‘started’before receivingmessages.


Management


Connection Factory

Connection



creates

creates


creates

The producer writes.QueueSender or TopicPublisher

The consumer retrieves.QueueReceiverTopicSubscriber


Management


Connection Factory

Connection



creates

creates


creates

A single, serialized flow of messagesbetween the client and a provider.This flow may be transacted.

QueueSession orToipcSession


Management

Java Messaging Architecture (Centralized)

Client Application

MessageBroker

Client Application

ClientApplication

Client Application

Client Application


Management

Java Messaging Architecture

MessageBroker

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 acknowledgementmodes.

Connection


Management

JMS Transaction

MessageBroker

Client Application

Client Application

Connectionscontain transacted sessions

Begin transaction send M1 send M2 send M3commit or rollback

M1 M2 M3

Messages are staged by the broker until thecommit.After commit the message may be deliveredto other clients. Upon rollback, the messages are disposed.


Management

JMS Acknowledgements

MessageBroker

Client Application

Client Application

Connectionscontain sessions with acknowledgement modes.These are low level acknowldgements, not associated with replies thatfollow requests.

M1

I got it!


Management

JMS Acknowledgements

MessageBroker

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.


Management

JMS Between Organizations(1)

JMSMessageBroker

Client Application

JMS Bridge

Products exist allowing these two brokers to talk. This degree of interconnectedness may be inappropriate.

MQSeriesMessageBroker


Management


JMSMessageBroker

Client Application

Web Components may act as JMS clients.

ServletClient

Application

BrowserClient

HTTP


Management


JMSMessageBroker

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 Webclient and pass data to the JMS broker.This is less tightly coupled than connecting two JMS providers with a bridge.

Web ServiceClient

Application

WebClient

Using SOAP

HTTP

Documents

Organizational Communications and Distributed Object Technologies