Package jakarta.jms


package jakarta.jms

The Jakarta Messaging API provides a common way for Java programs to create, send, receive and read an enterprise messaging system's messages.

Jakarta Messaging Applications

A Jakarta Messaging application is composed of the following parts:

  • Jakarta Messaging provider - a messaging system that implements the Jakarta Messaging API in addition to the other administrative and control functionality required of a full-featured messaging product
  • Jakarta Messaging clients - the Java language programs that send and receive messages
  • Messages - objects that are used to communicate information between the clients of an application
  • Administered objects - provider-specific objects that clients look up and use to interact portably with a Jakarta Messaging provider
  • Non-Jakarta Messaging clients - clients that use a message system's native client API instead of the Jakarta Messaging API. If the application predated the availability of the Jakarta Messaging API, it is likely that it will include both Jakarta Messaging clients and non-Jakarta Messaging clients.

Administration

Jakarta Messaging providers differ significantly in their implementations of underlying messaging technology. There are also major differences in how a Jakarta Messaging provider's system is installed and administered.

For Jakarta Messaging clients to be portable, they must be isolated from these proprietary aspects of a provider. This is done by defining Jakarta Messaging administered objects that are created and customised by a provider's administrator and later used by clients. The client uses them through Jakarta Messaging interfaces that are portable. The administrator creates them using provider-specific facilities.

There are two types of Jakarta Messaging administered objects:

  • ConnectionFactory - the object a client uses to create a connection with a Jakarta Messaging provider
  • Destination - the object a client uses to specify the destination of messages it is sending and the source of messages it receives

Administered objects are placed by an administrator in a JNDI (Java Naming and Directory Interface) namespace. A Jakarta Messaging client typically notes in its documentation the Jakarta Messaging administered objects it requires and how the JNDI names of these objects should be provided to it.

Two Messaging Styles

Jakarta Messaging supports two styles of messaging:

  • point-to-point (PTP) messaging using queues
  • publish-and-subscribe (pub/sub)messaging using topics

These two styles represent two of the dominant approaches to messaging currently in use.

Jakarta Messaging APIs

For historical reasons Jakarta Messaging offers four alternative sets of interfaces for sending and receiving messages:

  • Java Message Service 1.0 defined two domain-specific APIs, one for point-to-point messaging (queues) and one for pub/sub (topics). Although these remain part of Jakarta Messaging for reasons of backwards compatibility they should be considered to be completely superseded by the later APIs.
  • Java Message Service 1.1 introduced a new unified API which offered a single set of interfaces that could be used for both point-to-point and pub/sub messaging. This is referred to here as the classic API.
  • Jakarta Messaging 2.0 introduces a simplified API which offers all the features of the classic API but which requires fewer interfaces and is simpler to use.

Each API offers a different set of interfaces for connecting to a Jakarta Messaging provider and for sending and receiving messages. However they all share a common set of interfaces for representing messages and message destinations and to provide various utility features.

All interfaces are in the jakarta.jms package.

Interfaces common to multiple APIs

The main interfaces common to multiple APIs are as follows:

  • Message, BytesMessage, MapMessage, ObjectMessage, StreamMessage and TextMessage - a message sent to or received from a Jakarta Messaging provider.
  • Queue - an administered object that encapsulates the identity of a message destination for point-to-point messaging
  • Topic - an administered object that encapsulates the identity of a message destination for pub/sub messaging.
  • Destination - the common supertype of Queue and Topic

Classic API interfaces

The main interfaces provided by the classic API are as follows:
  • ConnectionFactory - an administered object used by a client to create a Connection. This interface is also used by the simplified API.
  • Connection - an active connection to a Jakarta Messaging provider
  • Session - a single-threaded context for sending and receiving messages
  • MessageProducer - an object created by a Session that is used for sending messages to a queue or topic
  • MessageConsumer - an object created by a Session that is used for receiving messages sent to a queue or topic

Simplified API interfaces

The simplified API provides the same messaging functionality as the classic API but requires fewer interfaces and is simpler to use. The main interfaces provided by the simplified API are as follows:
  • ConnectionFactory - an administered object used by a client to create a JMSContext. This interface is also used by the classic API.
  • JMSContext - an active connection to a Jakarta Messaging provider and a single-threaded context for sending and receiving messages
  • JMSProducer - an object created by a JMSContext that is used for sending messages to a queue or topic
  • JMSConsumer - an object created by a JMSContext that is used for receiving messages sent to a queue or topic

Legacy domain-specific API interfaces

Although the domain-specific API remains part of Jakarta Messaging for reasons of backwards compatibility it should be considered to be completely superseded by the classic and simplified APIs.

The main interfaces provided by the domain-specific API for point-to-point messaging are as follows:

  • QueueConnectionFactory - an administered object used by a client to create a QueueConnection.
  • QueueConnection - an active connection to a Jakarta Messaging provider
  • QueueSession - a single-threaded context for sending and receiving messages
  • QueueSender - an object created by a QueueSession that is used for sending messages to a queue
  • QueueReceiver - an object created by a QueueSession that is used for receiving messages sent to a queue
The main interfaces provided by the domain-specific API for pub/sub messaging are as follows:
  • TopicConnectionFactory - an administered object used by a client to create a TopicConnection.
  • TopicConnection - an active connection to a Jakarta Messaging provider
  • TopicSession - a single-threaded context for sending and receiving messages
  • TopicPublisher - an object created by a TopicSession that is used for sending messages to a topic
  • TopicSubscriber - an object created by a TopicSession that is used for receiving messages sent to a topic

Terminology for sending and receiving messages

The term consume is used in this document to mean the receipt of a message by a Jakarta Messaging client; that is, a Jakarta Messaging provider has received a message and has given it to its client. Since Jakarta Messaging supports both synchronous and asynchronous receipt of messages, the term consume is used when there is no need to make a distinction between them.

The term produce is used as the most general term for sending a message. It means giving a message to a Jakarta Messaging provider for delivery to a destination.

Developing a Jakarta Messaging Application

Broadly speaking, a Jakarta Messaging application is one or more Jakarta Messaging clients that exchange messages. The application may also involve non-Jakarta Messaging clients; however, these clients use the Jakarta Messaging provider's native API in place of the Jakarta Messaging API.

A Jakarta Messaging application can be architected and deployed as a unit. In many cases, Jakarta Messaging clients are added incrementally to an existing application.

The message definitions used by an application may originate with JMS, or they may have been defined by the non-Jakarta Messaging part of the application.

Developing a Jakarta Messaging Client

A typical Jakarta Messaging client using the classic API executes the following Jakarta Messaging setup procedure:

  • Use JNDI to find a ConnectionFactory object
  • Use JNDI to find one or more Destination objects
  • Use the ConnectionFactory to create a Jakarta Messaging Connection object with message delivery inhibited
  • Use the Connection to create one or more Jakarta Messaging Session objects
  • Use a Session and the Destinations to create the MessageProducer and MessageConsumer objects needed
  • Tell the Connection to start delivery of messages

In contrast, a typical Jakarta Messaging client using the simplified API does the following:

  • Use JNDI to find a ConnectionFactory object
  • Use JNDI to find one or more Destination objects
  • Use the ConnectionFactory to create a JMSContext object
  • Use the JMSContext to create the JMSProducer and JMSConsumer objects needed.
  • Delivery of message is started automatically

At this point a client has the basic Jakarta Messaging setup needed to produce and consume messages.

Package Specification

Jakarta Messaging 3.1 specification
Jakarta Enterprise Edition Technical Documentation