Domain-Specific and Unified APIs

The JMS API defines interfaces and classes that you can use to implement either of the point-to-point or the publish/subscribe domains. These are the domain-specific API’s shown in columns 2 and 3 of Table 2–1. The JMS API defines an additional unified domain, which allows you to program a generic messaging client. The behavior of such a client is determined by the type of the destination to which it produces messages and from which it consumes messages. If the destination is a queue, messaging will behave according to the point-to-point pattern; if the destination is a topic, messaging will behave according to the publish/subscribe pattern.

The unified domain was introduced with JMS version 1.1. The domain-specific API also provides a clean programming interface that prevents certain types of programming errors: for example, creating a durable subscriber for a queue destination. However, the domain-specific APIs have the disadvantage that you cannot combine point-to-point and publish/subscribe operations in the same transaction or in the same session. If you need to do that, you should choose the unified domain API. See The Request-Reply Pattern for an example of combining the two domains.