| Summary: | Adding concurrency to an application in the J2EE (Java 2 Platform, Enterprise Edition) framework is severely restricted because of two main reasons; first, the EJB (Enterprise JavaBeans) specification restricts spawning new user threads in an EJB container, and second, methods on a session bean can only be invoked synchronously. However, many applications require concurrent implementations to ensure an acceptable response time. There are multiple ways to overcome these limitations. Messaging becomes the obvious choice because of its inherent asynchronous nature and strong integration with J2EE application servers via JMS (Java Message Service) and message-driven beans (MDBs). This article describes in detail how MDBs can effectively provide concurrency to J2EE applications. (2,900 words; July 18, 2003)
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