O'Reilly - Java Message Service

Java Message Service
recognition of this, JMS provides guaranteed delivery, which ensures that intended
consumers will eventually receive a message even if partial failure occurs.
Guaranteed delivery uses a store-and-forward mechanism, which means that the
underlying message server will write the incoming messages out to a persistent store if the
intended consumers are not currently available. When the receiving applications become
available at a later time, the store-and-forward mechanism will deliver all of the messages
that the consumers missed while unavailable (see Figure 1.10).
Figure 1.10. Underlying store-and-forward mechanism guarantees delivery of messages
To summarize, JMS is not just another event service. It was designed to cover a broad
range of enterprise applications, including EAI, B2B, push models, etc. Through
asynchronous processing, store-and-forward, and guaranteed delivery, it provides high
availability capabilities to keep business applications in continuous operation with
uninterrupted service. It offers flexibility of integration by providing publish-and-subscribe
and point-to-point functionality. Through location transparency and administrative control,
it allows for a robust, service-based architecture. And most importantly, it is extremely
easy to learn and use. In the next chapter we will take a look at how simple it is by
building our first JMS application.
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