Jakarta Messaging

The Jakarta Messaging API (formerly Java Message Service or JMS API) is a Java application programming interface (API) for message-oriented middleware. It provides generic messaging models, able to handle the producer–consumer problem, that can be used to facilitate the sending and receiving of messages between software systems. Jakarta Messaging is a part of Jakarta EE and was originally defined by a specification developed at Sun Microsystems before being guided by the Java Community Process.
General idea of messaging.
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 (such as TCP network sockets, CORBA or RMI) 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 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:
Models.
The JMS API supports two distinct models:
Point-to-point model.
Under the "point-to-point" messaging 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.
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 (JNDI) 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.
URI scheme.
RFC 6167 defines a codice_1 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 EE version 1.4, a JMS provider has to be contained in "all" Java 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: