Enterprise JavaBeans (EJB) Overview

1. Introduction

Enterprise JavaBeans (EJB) is a server-side software component that encapsulates the business logic of an application. EJBs are part of the Java EE (Enterprise Edition) specification and are designed to simplify the development and deployment of large-scale applications.

2. Key Concepts

• EJBs are reusable components that can be accessed remotely.
• They provide transaction management, security, and concurrency control.
• EJBs can be classified into session beans and entity beans.
• They are managed by a container which handles lifecycle management.

3. Types of EJBs

1. Session Beans: Used for business logic. They can be stateful or stateless.
2. Entity Beans: Represent persistent data and are used to manage data stored in databases.
3. Message-Driven Beans: Used to handle asynchronous messaging.

4. EJB Lifecycle

The lifecycle of an EJB is managed by its container. Here is a simplified flowchart of the EJB lifecycle:

graph TD;
    A[Start] --> B[Create];
    B --> C[Ready];
    C --> D[Remove];
    D --> E[End];
            

Each EJB goes through different states: New, Ready, Passivated, and Removed.

5. Best Practices

• Use stateless session beans for operations that do not require maintaining state.
• Implement proper transaction management to ensure data integrity.
• Utilize dependency injection to manage resources efficiently.
• Keep business logic within EJBs and avoid placing it in servlets or other components.

6. FAQ