EJB Full Form- Enterprise Java Bean

What is EJB? The full form of EJB is Enterprise Java Bean. One of the many Java APIs used in the typical manufacturing of enterprise software is Enterprise Java Beans (EJB). A server-side software component called EJB condenses an application's business logic. The web repository for Enterprise Java Beans provides a runtime domain for web-related software components, such as transaction processing, Java Servlet Lifecycle (JSL) management, computer dependability, and other online services. A subset of the Java EE enumeration is the EJB enumeration.  Originally created by IBM in 1997, Sun Microsystems adopted the EJB enumeration in 1999 and improved it under the Java Community Process. 

How EJB Works 

The goal of the EJB enumeration is to offer a uniform approach to implementing server-side business applications, which are commonly seen in enterprise applications. The same kinds of issues are addressed by such machine code, and programmers frequently reimplement fixes for these issues. Programmers are free to concentrate on the specific components of the enterprise product at hand because Enterprise Java Beans are designed to handle common concerns like durability, transactional probity, and security in a standard manner. 

An application server (EJB Container), such as Jboss, Glassfish, Weblogic, Websphere, etc., is required to run EJB applications. It performs 

• Security
• Life Cycle Management 
• Object Pooling
• Transaction Management 

Different Types of EJB

Three varieties of EJB exist: 

1. Session Bean: A local, remote, or web service client can call the business logic contained in a session bean. Two varieties of session beans exist: (i) Stateful session beans and (ii) stateless session beans, respectively.  

(i) Stateful Session Bean: This type of bean uses a state to assist it in carrying out business tasks. A stateful session bean stores the data in an instance variable, which can be utilized to access different method calls. Certain applications necessitate the storage of data across distinct method calls. The things that a customer chooses on a shopping website need to be kept as data; this is an example of a stateful session bean. 

 (ii) Stateless Session Bean: Stateless session beans can leverage shared data and carry out business logic without requiring a persistent storage mechanism like a state or database. When data is not needed to be shared across call methods, a stateless session bean can be used. 

2. Message Driven Bean: This bean has business logic just like the Session Bean, but it's called upon by passing a message. 

3. Entity Bean: It provides an overview of the states that a database can maintain. It is no longer supported. These days, JPA (Java Persistence API) takes its place. Two types of entity beans exist: 

(i) Bean Managed Persistence: The code for database calls must be written by the programmer for an entity bean that uses bean managed persistence. It holds true for numerous clients and sessions.  

(ii) Container Managed Persistence: An enterprise bean with persistence across databases is known as container managed persistence. Database calls are handled by the container in container controlled persistence. 

Advantages of EJB

Some of the advantages of EJB are listed below:

1. Enterprise beans can access system-level services through the EJB repository, freeing up the bean developer to concentrate on addressing business issues. Transaction management and security authorization are examples of system-level functions that fall under the purview of the EJB repository, not the bean developer. 

2. The business logic of the application is contained in the beans rather than the clients, allowing the client developer to concentrate on the client's presentation. The pattern that accesses databases and runs business rules does not require coding on the part of the client developer. As a result, the clients are slimmer—a feature that is especially significant for those who use small devices.

3. Business Java Beans are elements that are portable; existing beans can be used by the application assembler to create new applications.