Introduction to EJB Architecture

Here we are going to learn about the EJB Architecture and the difference between JB and EJB. So let’s explore more about it.

Java beans – Java beans encompasses multiple objects into a comprehensible object that can be accessed from any applications. This object is reusable, customizable and easily maintainable. It’s governed by two methods setter/getter and a single public constructor. It is possible to update the value of any variable in an object using the setter method and read its value using the getting method for display purposes or further processing. Lightweight Swing and Heavyweight Abstract Tool kit are part of Java beans.

Enterprise Java beans – It is a server-based architecture, adhering to the specifications and requirements of the enterprise environment. The beans run in a container in four-tier architecture J2EE consisting of Client layer, Web layer, Application Layer, and Data layer.

Difference between JB and EJB

Here is the difference between table mention below

Java Beans	Enterprise Java beans
Visible	Not visible, Runs as remote
Local, Single process and runs in the Client machine Server-side beans are possible not preferred	Executed in the server-side
Applets and applications are built using generic components created by Java Beans.	It uses component technology but it is not built or extended over Beans.
It has an external interface to interpret bean’s functionality	Works seamlessly with IDE or external builder tool.
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No types, No support for transactions	Have three types and transactions are supported

EJB is an ideal platform for the development of large scale distributed applications for any business and it is a server-based deployment. Client machines get connected to the EJB beans either through EJB remote interface (ERI) or through home interface housed in through EJB container in the EJB application server.

Methods present in EJB in the application server provide the necessary business logic in a centralized manner and these methods can be opened remotely or locally for reading the data as well as updating the data.

In this architecture, there are three components viz., Java beans, EJB container holding these beans and application server housing the containers.

Architecture of EJB

The architecture of EJB is mention below

1. Application Server

This server is the outermost layer in the architecture and it holds the container. It provides the necessary environment to execute the applications developed using the beans. Web-logic, Web-sphere, JBoss, Tomcat, Wildfly, and Glass-finish are some of the application servers popular in the market.

The main functionality of Application servers is a. Manage Interfaces, b. Execution of the processes, c. Connecting to the database, d. Manage other resources.

2. Container

Container is the second outermost layer in EJB structure and it provides the following supporting services to the enterprise beans housed in it.

Transactional service like Registering the objects, assign remote interface, purge the instances
Monitoring the activities of the objects and coordinating distributed components
Security service and Pooling of resources
Manages Life-cycle of beans and its concurrency
Provide a platform for the developer to concentrate on business logic

3. Beans

Enterprise java bean installed in the container is something like Plain old java object (POJO) and they are registered to the container. Beans provide business logic for developing robust, secured and large scale business applications.

Types of Enterprise Java Beans

Enterprise Java Beans is of three types viz., Session beans, Entity beans, and Message-driven beans.

1. Session beans

It is the most common beans called by the client and it covers a major portion of business logic. The client may be remote or local thru JVM.

Stateless beans: These beans don’t have to meet the status of the backend and are used to deploy stateless business logic. Stateless bean is a right fit for a mere data capturing scenario where back end status is not
Stateful beans: Used in Scenarios in which the status of the back end should be maintained. For example applications like shipping, cart need to keep track of back end status as part of the application
Singleton beans: It refers to a class instantiated once and remains for the lifecycle for an application.

2. Entity beans

These beans hold the data even after the app is closed (Persistent) and the persistence can occur at the container level and bean level.

3. Message-driven beans

These beans play a major role in sending and receiving messages through message broker as per Java messaging server spec.

Advantages of EJB Architecture

Below are the advanatages:

Since Application built on EJB has API characteristics, it can run on any Java enterprise edition (EE) application
The developer can focus on business logic and solving business pain
EJB containers provide several services during the execution of beans
Helps in building a robust, secured large scale application with
It has many portable components refreshing current java beans applications becomes

Conclusion

EJB provides a robust platform for rolling out large scale applications using reusable business logic present in beans. EJB option can be evaluated for application development at the organization level.