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In-Depth Information
Figure 4.1. Basic MOM flow. When the producer sends a message to the middleware, it's stored immediately and
later collected by the consumer.
MOM systems and vendors aren't a new concept—they've been around since the 1980s.
MOMs evolved as a way to simplify system integration and reduce the amount of custom
integration code. Systems written today must still interact with other systems—both legacy
and new. There are many MOM products on the market today. All Java EE servers come
with a messaging system.
To flesh out messaging concepts a bit more, let's explore a problem in the Action-Bazaar
application. You'll continue working on this problem as we progress through the rest of the
chapter.
4.1.2. Messaging in ActionBazaar
ActionBazaar isn't a self-contained, end-to-end system. It excels at managing and tracking
auctions. But other business functions like accounting and shipping are handled by separate
dedicated systems provided by specialized vendors. ActionBazaar chooses to purchase and
integrate with these vendor services instead of reinventing the services in-house. For ex-
ample, ActionBazaar uses the Turtle Shipping Company to deliver items to winning bid-
ders. When a bidder wins an auction, a shipment request is sent to Turtle's system via a
business-to-business (B2B) connection. Initially, all external vendor systems were integ-
rated in a synchronous fashion.
Figure 4.2
shows how this integration looked and what the
problems with it were.
