Managing Information Access to an Enterprise Information System Using J2EE and Services Oriented Architecture

122 Managing Information Access to an EIS Using J2EE and Services Oriented Architecture

6.1 Message-oriented middleware and JMS

Message-oriented middleware (MOM) is one of the most established areas of

middleware software. It is an intermediary that facilitates enterprise messaging

by allowing enterprise applications to exchange information in the form of

messages across the network. Applications exchange messages through virtual

channels known as destinations. When a message client sends a message, it

sends the message to a destination, and the MOM delivers the message to

applications that register interest to receive messages from that destination.

This asynchronous communication method de-couples the sender and receiver,

allowing the applications to send and receive messages as they see fit. In

addition to asychronous communication, MOM also provides fast, reliable, and

guaranteed message delivery with fault tolerance, load balancing, scalability, and

transactional support. WebSphere MQ is the message-oriented middleware

product available from IBM that is widely used by customers for EIS integration.

WebSphere MQ is the market-leading software product in that segment.

MOM vendors provide application developers with APIs for sending and

receiving messages. While a MOM vendor can use proprietary message formats

and implement its own networking protocols to exchange messages, the basic

semantics of the developer APIs provided by different MOMs are the same. This

similarity in APIs makes the JMS possible.

JMS is an API for enterprise messaging that was created by Sun Microsystems.

JMS is not a messaging system itself. Instead, JMS is a vendor-agnostic API. It

is a set of interfaces and associated semantics that are needed by messaging

clients to communicate with messaging systems. Just as JDBC abstracts

accesses to relational databases, JMS abstracts accesses to MOMs and allows

application developers to reuse the same API to access many different

JMS-compliant messaging systems. Thus, JMS provides a common API and

framework that simplifies the development of enterprise applications and enables

the development of portable, message-based applications.

For more information, refer to the following publications:

򐂰 Richard Monson-Haefel & David A. Chappell, Java Message Service.

O’Reilly, 2001, ISBN 0-595-00068-5

򐂰 Scott Grant et. al., Professional JMS, Wrox Press, 2001, ISBN 1-861004-93-1

򐂰 Enterprise Integration with IBM Connectors and Adapters, SG-2461-22

򐂰 WebSphere Application Server and WebSphere MQ Family Integration,

SG24-6878

򐂰 WebSphere Studio Application Developer Version 5 Programming Guide,

SG24-6957