Enterprise JavaBeans, Third Edition

Message-Driven Beans

Message-driven beans (MDBs) are stateless, server-side, transaction-aware components for processing asynchronous JMS messages. Newly introduced in EJB 2.0, message-driven beans process messages delivered via the Java Message Service.

Message-driven beans can receive JMS messages and process them. While a message-driven bean is responsible for processing messages, its container takes care of automatically managing the component’s entire environment, including transactions, security, resources, concurrency, and message acknowledgment.

One of the most important aspects of message-driven beans is that they can consume and process messages concurrently. This capability provides a significant advantage over traditional JMS clients, which must be custom-built to manage resources, transactions, and security in a multithreaded environment. The message-driven bean containers provided by EJB manage concurrency automatically, so the bean developer can focus on the business logic of processing the messages. The MDB can receive hundreds of JMS messages from various applications and process them all at the same time, because numerous instances of the MDB can execute concurrently in the container.

A message-driven bean is a complete enterprise bean, just like a session or entity bean, but there are some important differences. While a message-driven bean has a bean class and XML deployment descriptor, it does not have component interfaces. The component interfaces are absent ...