Enterprise JavaBeans (EJB) technology has gained unprecedented momentum among both platform providers and enterprise developers. The main reason for this is that the EJB component model simplifies the development of middleware applications by providing automatic support for services such as transactions, security, database connectivity, and more. The EJB 2.1 specification enhances the EJB architecture with support for Web services. Enterprise developers can implement and deploy Web service applications with the same level of ease as other server-side applications.
In addition, EJB 2.1 provides a container-managed Timer Service, enhancements to EJB QL, the declarative language for container-managed persistence and support for aggregate and order-by operations. EJB 2.1 also provides support for a generalization of message-driven beans. The EJB timer service is a container-provided service that allows the bean provider to register enterprise beans for timer callbacks that occur after a specified time, after a specified elapsed time, or at specified intervals. This service creates a timer to schedule callbacks.
When the time specified at timer creation elapses, the container invokes the EJBtimeout method of the bean. EJB 2.1 enables web services where a web service client may invoke stateless session beans using the Simple Object Access Protocol or SOAP. A bean’s Web service endpoint interface is described with Web Service Description Language or WSDL. EJB 2.1 supports EJB-QL which is a query language for finder and select methods of CMP entity beans.
The container compiles the queries to a target language for the underlying database. EJB 2.1 also supports message-driven beans, which consume messages only from JMS sources, like Queue or Topic. EJB2.1 extends this functionality so that the beans consume messages from other message sources like XML (JAXM). A message-driven bean can receive messages from a single messaging type only, depending upon the messaging interface it extends.
Java Development India offers EJB 2.1 development, EJB 2.1 consulting and EJB 2.1 related solutions from our offshore software development outsourcing centre at Kochi, Kerala in India.
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