Developing JMS Applications 

Purpose

The Java Message Service (JMS) is an enterprise messaging system that provides a way for business applications to exchange data without needing to be directly connected to each other. The communication is obtained using messages.

Note that JMS is not a product itself, but a set of predefined interfaces provided in the javax.jms package. The applications use this API to send and receive messages to and from a destination located on the JMS Provider. Java programs that send and/or receive messages using JMS are called JMS clients.

The Java applications can use JMS to send and receive messages using an enterprise messaging server in a standardized, vendor-independent way. The actual messaging product that implements the JMS interfaces is the JMS provider.

The AS Java’s JMS provider is compliant with the JMS specifications versions 1.0.

JMS Object Hierarchy

Some of these objects are administered objects according to the JMS specification. These objects are created and configured using an administration tool.

Main JMS Objects

●      Connection factory

An administrated object you use to create JMS connections. Connection factories are obtained (looked up) from the JNDI.

●      Connection

The connection is a factory for session objects.

●      Session

A single-threaded context for sending and receiving messages. Using the session you can create a:

○       Message producer

An object created by the session used to send messages to a destination.

○       Message consumer

An object created by the session used to receive messages sent to a destination.

○       Message

The messages are the actual information exchanged by JMS clients.

●      Destinations

The destination is an administered object that encapsulates the identity of a message destination. The destination messaging model could be:

○       Point-to-point (queue destination)

Use it to send messages that only one specified consumer can receive, that is, “one-to-one” message delivery.

○       Publish-subscribe (topic destination)

Use it to send messages to a group of consumers, that is, “one-to-many” message delivery. The model also allows you to create durable subscribers, which enable you to get a message sent to this destination while the consumer was not active.

Destination objects are set up as administered objects and then retrieved by the JMS client at runtime using JNDI instead of being directly instantiated. The JMS Provider also offers you a way to dynamically instantiate temporary destinations.

Implementation Considerations

The JMS enables applications that use one messaging system to exchange messages easily. With the JMS API, you have a standard for writing applications that have to send, receive or exchange asynchronous messages.

The AS Java’s JMS provider is compliant with the JMS specifications versions 1.0.

Major Features

JMS Provider Major Features

Feature	Description
JMS 1.0 Compliance	Full compliance with the JMS 1.0 specification.
Software High Availability	Software-based high availability solution.
JTA Transactions	Implementation of transactions compliant with the JTA specification.
XA Transactions	Implementation of transactions compliant with the XA specification.
RDBMS Persistence	Message persistence implemented using a relational database.
Message pre-fetching	The feature to pre-fetch JMS messages from the JMS server to a synchronous JMS client. This can improve performance in certain scenarios.
Message Paging / Swapping	The feature to swap necessary parts of the messages to a persistent store to free up main memory. This may cause persisting non-persistent messages.
Multiple Queue Receivers	The JMS specification does not specify the behavior in case several consumers are registered on one and the same queue. The SAP’s JMS Provider supports multiple queue receivers and the behavior is configurable – round-robin delivery or exception on second receiver.
Dead Messages Support	Dead messages are messages that cannot be delivered to the client after a configurable number of attempts. Such messages are moved to a dedicated dead messages queue where an administrator can review them.
HermesJMS Integration	Integration with the popular open-source administration and monitoring tool HermesJMS.
XML Message Export / Import	The ability to export and/or import JMS messages of a particular destination in XML format.
JMX Support	Remote administration and monitoring of the JMS Provider using JMX.
Security Administration	The set of features to define, modify and enforce security restrictions to JMS resources and operations. Note that the JMS specification does not define any security aspects of the JMS service.

 

See also:

●      JMS Overview – for information about how to develop applications using JMS.

●      JMS Administration