What are the new features of EJB 2.1?

Enterprise JavaBeans (EJB) is a managed, server-side component architecture for modular construction of enterprise applications. The EJB specification is one of several Java APIs in the Java Platform, Enterprise Edition. EJB is a server-side model that encapsulates the business logic of an application. The following are the new features of EJB 2.1:

1. Message-driven Bean Enhancements: It can now accept messages from sources other than JMS. The configuration of the MDB is done with a new <messaging-type> tag, and by specifying “configuration properties” with the tag <activation-config-propertyType>. This contains arbitrary name/value pairs that are specific to the messaging service being used. It is more versatile than being forced to use JMS-specific tags, like <message-selector>.
2. EJB-QL Enhancements: EJB 2.1 extends its language to make it more SQL-like by adding few clauses and aggregate functions to the language.
3. Web Services support: In EJB 2.1, the EJB can be used as if it were a Web service, and an EJB directly accessing a Web service. A stateless session EJB can now be accessed through a Web service. In order to do that, the client must use SOAP over HTTP or HTTPS, and use a WSDL descriptor. The new EJB 2.1 specification introduces the concept of a Web service reference. This is exactly the same concept as environment entries, EJB references, and resource references. Adding a Web service reference in ejb-jar.xml is done using the new tag <service-ref>. It is up to the container provider to map the reference to the actual Web service location. The reference can be looked up in the bean implementation, and the resulting factory object can be used to connect to the Web service.
4. EJB Timer Service: The new EJB 2.1 timer service is a mechanism to enable time-based business logic. It provides services such as running a certain query in five minutes, deleting the content of the “garbage can” database table two hour from now, posting an email saying “server shutdown in 1 hour” to all employees, sending a usage report to the administrator every Sunday at 6 p.m., etc.
5. EJB containers now supports the newest specifications: J2SE 1.4, JMS 1.1, JavaMain 1.3, and JAX-RPC 1.0.
6. The ejb-jar.xml standard deployment descriptor is now specified with XML schema, rather than DTD.
7. Message destinations have been added.

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