Java Messaging Service (JMS)

Messaging is a common integration pattern used by Java applications. The Java messaging API (JMS) supports message creation, delivery, receipt and the ability to read messages. JMS defines roles for messaging services known as JMS providers and guarantees delivery between systems. Popular implementations of JMS are Active MQ, IBM MQ and Open MQ.

Common messaging models

1) Point-to-point

A JMS producer will write a message to a queue which is then consumed off the queue by a single JMS consumer.

2) Publish-subscribe

The pub-sub messaging model uses a topic instead of a queue which facilitates messages to be distributed to multiple JMS consumers instead of a single consumer.

Message Structure

A JMS message contains 3 sections:

a) Headers

The JMS headers are fixed across all JMS messages and include the destination, delivery method, message ID, delivery time and other envelope information.

b) Properties

The properties section of the message allows producers or the JMS provider to add optional headers to the message that can be read by the consumers.

c) Body

The body of the JMS message can be one of five types, providing support for streams, maps, text, objects or bytes.

JMS interfaces

API	Description
ConnectionFactory	Encapsulates the connection configuration parameters
JMSContext	Provides a combination of session and connection; allows for the creation of consumers and producers
JMSConsumer	Client object for reading messages from a queue or topic
JMSProducer	Object for building and sending messages to a queue or topic

JMS Producers

Within the JMS API, the producer interface is used to send messages to a JMS Queue or topic. The approach for creating a producer and sending a message has been simplified with the use of annotations since JMS 2.0.