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 EE specification. EJB is a server-side model that encapsulates the business logic of an application. The EJB specification was originally developed in 1997 by IBM and later adopted by Sun Microsystems (EJB 1.0 and 1.1) in 1999 and enhanced under the Java Community Process as JSR 19 (EJB 2.0), JSR 153 (EJB 2.1), JSR 220 (EJB 3.0) and JSR 318 (EJB 3.1).
The EJB specification intends to provide a standard way to implement the back-end 'business' code typically found in enterprise applications (as opposed to 'front-end' interface code). Such code was frequently found to address the same types of problems, and it was found that solutions to these problems are often repeatedly re-implemented by programmers. Enterprise JavaBeans were intended to handle such common concerns as persistence, transactional integrity, and security in a standard way, leaving programmers free to concentrate on the particular problem at hand.
Accordingly, the EJB specification details how an application server provides:
- Transaction processing
- Integration with the Persistence services offered by the Java Persistence API (JPA)
- Concurrency control
- Events using Java Message Service
- Naming and directory services (JNDI)
- Security (Java Cryptography Extension (JCE) and JAAS)
- Deployment of software components in an application server
- Remote procedure calls using RMI-IIOP.
- Exposing business methods as Web Services.
Additionally, the Enterprise JavaBean specification defines the roles played by the EJB container and the EJBs as well as how to deploy the EJBs in a container. Note that the current EJB specification does not detail anymore how an application server provides persistence (a task delegated to the JPA specification), but instead details how business logic can easily integrate with the persistence services offered by the application server.
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