Enterprise JavaBeans

(specification, business, programming)

(EJB) A server-side component architecture for writing reusable business logic and portable enterprise applications. EJB is the basis of Sun's Java 2 Platform, Enterprise Edition (J2EE).

Enterprise JavaBean components are written entirely in Java and run on any EJB compliant server. They are operating system, platform, and middleware independent, preventing vendor lock-in.

EJB servers provide system-level services (the "plumbing") such as transactions, security, threading, and persistence.

The EJB architecture is inherently transactional, distributed, multi-tier, scalable, secure, and wire protocol neutral - any protocol can be used: IIOP, JRMP, HTTP, DCOM etc. EJB 1.1 requires RMI for communication with components. EJB 2.0 is expected to require support for RMI/IIOP.

EJB applications can serve assorted clients: browsers, Java, ActiveX, CORBA etc. EJB can be used to wrap legacy systems.

EJB 1.1 was released in December 1999. EJB 2.0 is in development.

Sun claims broad industry adoption. 30 vendors are shipping server products implementing EJB. Supporting vendors include IBM, Fujitsu, Sybase, Borland, Oracle, and Symantec.

An alternative is Microsoft's MTS (Microsoft Transaction Server).

http://java.sun.com/products/ejb/.

FAQ.

This article is provided by FOLDOC - Free Online Dictionary of Computing (foldoc.org)

EJB

(Enterprise JavaBeans) A software component in the Java EE platform, which provides a pure Java environment for developing and running distributed applications. EJBs are written as software modules that contain the business logic of the application. They reside in and are executed in a runtime engine called an "EJB Container," which provides a host of common interfaces and services to the EJB, including security and transaction support. At the wire level, EJBs look like CORBA components.

Three Types of EJBs
The three types of EJBs are: (1) session beans perform processing, (2) entity beans represent data, which can be a row or a table in a database, and (3) message driven beans are generated to process Java Messaging Service (JMS) messages.

Very Versatile
EJBs inherently provide future scalability and also allow multiple user interfaces to be used. For example, both a Web browser and a Java application could be used to access EJBs, or one could be switched for the other at a later date. However, if these are not important issues, servlets, JSPs and regular Java applications can be used for business logic rather than EJBs. See Java EE, EJB container, EJB local interface, JavaBeans, distributed objects and component software.

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