EJB

EJB is a server-side software element that summarizes business logic of an application

Enterprise Java Beans web repository yields a runtime domain for web related software elements including computer reliability, Java Servlet Lifecycle (JSL) management, transaction procedure and other web services.

Types

• Session Bean: Session bean contains business logic that can be invoked by local, remote or webservice client.
• Message Driven Bean: Like Session Bean, it contains the business logic but it is invoked by passing message.
• Entity Bean: It summarizes the state that can be remained in the database. It is deprecated. Now, it is replaced with JPA (Java Persistent API).

When to use Enterprise Java Beans

• Application needs Remote Access. In other words, it is distributed.
• Application needs to be scalable. EJB applications supports load balancing, clustering and fail-over.
• Application needs encapsulated business logic. EJB application is differentiated from demonstration and persistent layer.