Design

By using message-driven beans, you get the features of a JMS listener plus functions performed by the container. Compared to method calls and events, MDB is a good choice for an application that:

• Requires components to communicate without knowing about each other.
• Must function even if all components are not running at the same time.
• Must be able to send messages and continue processing withou waiting for a response.

In the FBS 10g, alerts can be generated by numerous application modules, and OTN developers used MDBs to centralize the alert mechanism. By removing the tight coupling between the execution of a trade transaction and sending back the user response, the application can serve multiple users without compromising response times. MDBs allow asynchronous processing and thereby reduce the wait time for the customers.

All trade requests (both buy and sell) are sent as messages. When a message is posted to the queue, the application invokes an MDB which extracts the trade details and sends them to the exchange for processing. Once the processing is done, the result is mailed to the customer. Since posting a message is not a costly operation, the customers get split-second response times.