O'Reilly - Java Message Service
O'Reilly - Java Message Service
O'Reilly - Java Message Service
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<strong>Java</strong> <strong>Message</strong> <strong>Service</strong><br />
With the message-driven bean, it is important to understand that messages do not have to<br />
be produced by other beans in order for them to consumed by a message-driven bean.<br />
<strong>Message</strong>-driven beans can consume messages from any topic or queue administered by a<br />
JMS provider. [3] <strong>Message</strong>s consumed by message-driven beans may have come from other<br />
beans (session, entity, or message-driven beans), web components, application client<br />
components, normal non-J2EE JMS clients, or even legacy messaging systems supported<br />
by a JMS provider. A legacy application might, for example, use IBM's MQSeries to<br />
deliver messages to a queue, which is consumed by other legacy applications as well as<br />
message-driven beans.<br />
[3] In most cases the EJB vendor will also be the JMS provider, but it's possible some EJB vendors<br />
will provide hooks that allow third-party JMS providers to manage delivery of messages to an EJB<br />
container's message-driven beans.<br />
The <strong>Message</strong>DrivenBean interface is not specific to JMS-based messaging. While EJB 2.0<br />
requires support for JMS-based messaging, the specification also allows vendors to<br />
support other protocols and messaging systems (e.g., HTTP, ebXML, SMTP) using<br />
proprietary message-driven beans. And this is why the message-driven bean in EJB 2.0<br />
implements both the <strong>Message</strong>DrivenBean interface, as well as the <strong>Message</strong>Listener<br />
interface, to distinguish it as a message-driven bean.<br />
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