What are EJB’s ?
An EJB is a server-side component that executes specific business logic. EJBs run on a server and are invoked by local or remote clients. A standardized contract exists between an application server and its EJB components that enables a component to run within any application server . EJB is a heavyweight framework.
Components built in the JavaBeans specification are intraprocess components that stay in one address space and are typically used for Graphical User Interface (GUI) visual widgets such as buttons, tables, HTML viewers, etc. On the other hand, the EJB specification is based on the javax.ejb package, which is a standard extension package. EJB is one of several specifications grouped into Sun Microsystem's Java 2 Enterprise Edition (J2EE) specification. Components built in the EJB specification are interprocess components that stay in multiple address spaces as distributed objects. These components are used as transactional business objects that are accessed as remote objects.
So we have:
EJB is a framework for writing distributed programs.
EJB involves a standardized agreement that enables a component to run within any application server (increasing code reuse).
The agreement is accomplished by implementing a set of Java interfaces from the EJB API.
EJBs are not GUI components.
Types of EJB
There are three different types of beans in EJB: session, entity, and message-driven. Each has a specific purpose:
Session Beans: Represent an action or process that must be executed synchronously, such as making a reservation or validating a credit card.
Message-Driven Beans: Also represent an action or process. But, message-driven beans are executed asynchronously.
Entity Beans: Represent data; each entity bean represents a unique record in the database.
Certifications In EJB:
Sun Micro System Offering SCBCD:
SCBCD- SCBCD (Sun Certified Business Component Developer) certification exam is for professionals who develop and design Java applications using EJB (Enterprise Java Beans). Java programmers and developers who aspire to be SCBCD needs to be SCJP (Sun Certified Java Programmer
Sources:
Website: http://www.sun.com
