YourNote 201: Java EE

1. What is Java EE (Jakarta EE)?

• Java EE is a platform for building large-scale, enterprise web applications.
• Today, it is known as Jakarta EE

Built on top of Java SE, it provides:

• Web development tools
• Database integration
• Security
• Scalability features

2. Core Idea

Java EE is about:

Multi-user + Scalable + Secure + Distributed applications

Examples:

• banking systems
• university systems
• e-commerce platforms

3. Main Components

a) Servlets

• Handle HTTP requests
• Backend logic

b) JSP (JavaServer Pages)

• UI layer
• Display data

c) EJB (Enterprise JavaBeans)

• Business logic (advanced / enterprise level)

Note:

EJB is less popular now, but still an important concept.

d) JPA (Java Persistence API)

• Database interaction
• Replace raw JDBC

Example:

@Entity
public class Student {
    @Id
    private Long id;
}

e) REST APIs (JAX-RS)

• Build web services
• Used in modern apps

4. Architecture (VERY IMPORTANT FOR EXAM)

Typical 3-tier architecture:

• Presentation Layer → JSP
• Business Layer → Servlet / EJB
• Data Layer → Database (JPA/JDBC)

This is the foundation of enterprise systems

5. Application Server

Java EE apps run on servers like:

• Apache Tomcat (Servlet container)
• GlassFish
• WildFly

Students must know:

difference between web server vs application server

6. Packaging & Deployment

Applications are packaged as:

• WAR (Web Archive) → Servlet/JSP apps
• EAR (Enterprise Archive) → large enterprise systems

7. Security Concepts

Java EE provides:

• authentication (login)
• authorization (roles)

Example:

• Admin vs User access

8. Transactions Used in:

• banking
• payment systems

Ensures:

• data consistency
• rollback if error

9. Dependency Injection (DI)

Java EE supports DI:

@Inject
StudentService service;

Makes code cleaner and modular