Introduction to J2EE for BCA Sem 3 and IT Students Point by Point

Prepared By : Prof. Uday Shah (HOD-IT)

Unit 1 : Introduction to J2EE

1. Introduction to J2EE

• J2EE (Java 2 Platform, Enterprise Edition) is a platform designed for developing distributed, multi-tier enterprise applications.

• It extends the Java SE platform with APIs for server-side development.

• J2EE applications are typically large-scale, secure, and scalable.

• It provides a framework for web-based and enterprise-level applications.

• The platform supports components like Servlets, JSP, EJB, and more.

• J2EE allows developers to separate business logic from presentation and data layers.

• It offers built-in support for transactions, security, and messaging.

• Applications built with J2EE are portable across compliant servers.

• It includes APIs for database connectivity (JDBC) and directory services (JNDI).

• J2EE promotes reusable, modular, and flexible application design.

2. Enterprise Architecture

• Enterprise Architecture (EA) defines the structure and operation of an organization’s IT systems.

• It aligns IT strategy with business goals.

• EA provides a high-level view of system components and their interactions.

• It focuses on scalability, security, and performance of enterprise systems.

• EA helps in standardizing technology and reducing IT complexity.

• It defines processes, data flows, and system integration points.

• EA allows better decision-making for software and hardware investments.

• It is used as a blueprint for designing new systems or upgrading existing ones.

• It considers both the business processes and the supporting technologies.

• EA enables interoperability among different systems.

3. Enterprise Architecture Styles

a) Two-Tier Architecture

• Divides application into two layers: client and server.

• The client communicates directly with the server for data and services.

• Client layer is responsible for user interface and some business logic.

• Server layer handles database and core business logic.

• It is easy to develop and maintain.

• Suitable for small-scale applications.

• Performance is good for a limited number of users.

• Changes in the server can directly impact the client.

• Security is weaker as client has more access to the server.

• It lacks scalability for large systems.

b) Three-Tier Architecture

• Divides the application into three layers: presentation, business logic, and data.

• The presentation layer handles user interfaces.

• The business logic layer processes rules and computations.

• The data layer interacts with the database.

• It promotes separation of concerns.

• Scalability and security are improved compared to two-tier.

• Each layer can be modified independently.

• Middleware is often used for communication between layers.

• Load balancing is easier in three-tier systems.

• Suitable for medium to large enterprise applications.

c) N-Tier Architecture

• Extends the concept of three-tier into multiple layers.

• Each layer handles a specific responsibility (e.g., caching, service layer).

• Improves modularity and flexibility.

• Allows distribution of layers across multiple servers.

• It is highly scalable and reliable.

• Complex business applications benefit from N-tier.

• It enables easier integration with third-party systems.

• Deployment can be challenging due to multiple layers.

• Performance optimization may be required for communication overhead.

• Commonly used in cloud and microservices architectures.

4. The J2EE Platform

• J2EE provides a multi-tier distributed architecture for enterprise applications.

• It includes specifications for web, business, and integration tiers.

• Supports multiple programming models such as Servlets, JSP, and EJB.

• Includes APIs for messaging, mail, and directory services.

• The platform is independent of hardware and operating systems.

• J2EE promotes component-based development.

• It uses containers to manage components like Servlets and EJBs.

• Security and transaction management are standardized.

• Provides APIs for connecting to enterprise information systems (JCA).

• J2EE is the foundation for Java EE (now Jakarta EE).

5. Introduction to J2EE APIs

• Servlet: Java classes used to handle HTTP requests and responses in web applications.

• JSP (JavaServer Pages): Enables embedding Java code in HTML for dynamic web pages.

• EJB (Enterprise JavaBeans): Provides reusable business components.

• JMS (Java Messaging Service): Allows asynchronous messaging between components.

• JavaMail: API for sending and receiving emails using Java.

• JSF (JavaServer Faces): Framework for building user interfaces for web apps.

• JNDI (Java Naming and Directory Interface): API for accessing naming and directory services.

• These APIs are standardized and portable.

• They reduce boilerplate code by handling low-level services.

• Each API is integrated with containers for easier management.

6. Introduction to Containers

• Containers manage the execution of J2EE components.

• They provide runtime support and system-level services.

• Examples include web containers (for Servlets/JSP) and EJB containers.

• Containers handle tasks like security, transaction management, and resource pooling.

• They allow developers to focus on business logic instead of infrastructure.

• Containers manage component lifecycle automatically.

• They ensure standard compliance with J2EE specifications.

• Containers can provide scalability by distributing load.

• Examples: Apache Tomcat (web container), JBoss (full J2EE server).

• They abstract complexities like connection management and threading.

7. Tomcat as a Web Container

• Apache Tomcat is an open-source web container.

• It implements the Servlet and JSP specifications.

• Tomcat acts as the middleware between client requests and Java web applications.

• It manages the lifecycle of Servlets and JSP pages.

• Tomcat is lightweight and easy to configure.

• Provides support for secure communication (HTTPS).

• It offers features like load balancing and session management.

• Widely used for small to medium-scale web applications.

• Tomcat can be integrated with other servers like Apache HTTP Server.

• It is maintained by the Apache Software Foundation.

8. Configuration of Web Server - Apache Tomcat Server

• Download the Apache Tomcat distribution from the official website.

• Extract the files to a desired installation directory.

• Set the JAVA_HOME environment variable for Java.

• Use the CATALINA_HOME variable to point to Tomcat’s root directory.

• Start the server using the startup.bat (Windows) or startup.sh (Linux) scripts.

• Place web applications in the webapps folder.

• Configure users and roles in the tomcat-users.xml file.

• Adjust the server.xml file for port settings and connectors.

• Access the Tomcat manager through the browser at http://localhost:8080.

• Stop the server using the shutdown.bat or shutdown.sh scripts.