Messaging is a form of loosely coupled distributed communication, where in this context the term 'communication' can be understood as an exchange of messages between software components. Message-oriented technologies attempt to relax tightly coupled communication by the introduction of an intermediary component. This approach allows software components to communicate with each other indirectly. Benefits of this include message senders not needing to have precise knowledge of their receivers. The advantages of messaging include the ability to integrate heterogeneous platforms, reduce system bottlenecks, increase scalability, and respond more quickly to change.
Version history
JMS 1.0
JMS 1.0.1
JMS 1.0.1a
JMS 1.0.2
JMS 1.0.2a
JMS 1.0.2b
JMS 1.1
JMS 2.0
JMS 2.0a
JMS 2.0 is currently maintained under the Java Community Process as JSR 343. JMS 3.0 is under early development as part of Jakarta EE.
Elements
The following are JMS elements: ; JMS provider ; JMS client ; JMS producer/publisher ; JMS consumer/subscriber ; JMS message ; JMS queue ; JMS topic
Models
The JMS API supports two distinct models:
Point-to-point
Publish-and-subscribe
Point-to-point model
Under the point-to-pointmessaging system, messages are routed to individual consumers who maintain queues of incoming messages. This messaging type is built on the concept of message queues, senders, and receivers. Each message is addressed to a specific queue, and the receiving clients extract messages from the queues established to hold their messages. While any number of producers can send messages to the queue, each message is guaranteed to be delivered, and consumed by one consumer. Queues retain all messages sent to them until the messages are consumed or until the messages expire. If no consumers are registered to consume the messages, the queue holds them until a consumer registers to consume them.
Publish-and-subscribe model
The publish-and-subscribe model supports publishing messages to a particular message "topic". Subscribers may register interest in receiving messages published on a particular message topic. In this model, neither the publisher nor the subscriber knows about each other. A good analogy for this is an anonymous bulletin board.
Zero or more consumers will receive the message.
There is a timing dependency between publishers and subscribers. The publisher has to create a message topic for clients to subscribe. The subscriber has to remain continuously active to receive messages, unless it has established a durable subscription. In that case, messages published while the subscriber is not connected will be redistributed whenever it reconnects.
JMS provides a way of separating the application from the transport layer of providing data. The same Java classes can be used to communicate with different JMS providers by using the Java Naming and Directory Interface information for the desired provider. The classes first use a connection factory to connect to the queue or topic, and then use populate and send or publish the messages. On the receiving side, the clients then receive or subscribe to the messages.
RFC 6167 defines a jms: URI scheme for the Java Message Service.
Provider implementations
To use JMS, one must have a JMS provider that can manage the sessions, queues and topics. Starting from Java EEversion 1.4, a JMS provider has to be contained in allJava EE application servers. This can be implemented using the message inflow management of the Java EE Connector Architecture, which was first made available in that version. The following is a list of common JMS providers:
