Java J2ee Planet

An message-driven EJB is used to receive and process asynchronous messages using JMS. Message-driven EJBs are never directly invoked by other EJBs. However, they in turn can invoke methods of session and entity beans and send JMS messages to be processed by other message-driven EJBs. The topics listed below discuss development of message-driven beans. What are Message-Driven Beans? Message-driven beans are server-side objects used only to process JMS messages. These beans are stateless, in that each method invocation is independent from the next. Unlike session and entity beans, message-driven beans are not invoked by other beans or client applications. Instead a message-driven bean responds to a JMS message. Because message-driven beans are not invoked by other EJBs or clients, these beans do not have interfaces. For each message-driven bean a single method, onMessage , is defined to process a JMS message. Although message-driven beans cannot be invoked by other EJBs, the...

17)What’s the relationship between Enterprise JavaBeans component architecture and CORBA? The Enterprise JavaBeans specification is intended to support compliance with the range of CORBA standards, current and proposed. A Bean’s remote and home interfaces are RMI compliant, and thus can interact with CORBA objects via RMI/IIOP, Sun and IBM’s forthcoming adaptation of RMI that conforms with the CORBA-standard IIOP protocol. As a companion to the Enterprise JavaBeans specification, Sun Microsystems has defined a standard mapping from Enterprise Java Beans API to CORBA IDL. JTA, the transaction API prescribed by the Enterprise JavaBeans specification for bean-managed transactions, is designed to layer easily over the OMG OTS transaction standard. 18)What’s the relationship between Enterprise JavaBeans component architecture and XML technology? The two technologies are complementary: Enterprise JavaBeans defines a standard for portable business logic and XML technology defines a stand...