Guaranteed messaging uses middleware to ensure that a message is properly delivered to its destination, both ungarbled and in a reasonably timely fashion. The middleware implementing the messaging framework guarantees a message sent to a valid destination eventually arrives, even if the destination is temporarily unreachable.
Guaranteed delivery doesn't imply complete certainty. Specifying a nonexistent destination won't get your message delivered, regardless of how expensive your middleware is. And if a destination system is unavailable for a long period of time, the middleware will probably return the message to its sender rather than wait indefinitely. What is guaranteed, however, is the contract between the messaging client and the server governing how a message will be handled. Undeliverable messages won't vanish into the night but will be handled according to a specific and well-known set of rules.
Message Oriented Middleware systems implement guaranteed messaging. Senders and recipients work through a MOM server, which is responsible for tracking all elements of the message lifecycle. MOM servers often provide a range of options for the message content itself: XML, Java objects, raw binary data, and so on. J2EE clients interact with MOM servers using JMS, the Java Message Service. JMS, which is part of J2EE 1.3, provides a standard programmatic interface to the different MOM implementations, much as JDBC does for database servers. Sonic Software's SonicMQ and IBM's MQSeries products are two of the leading MOM products
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