Epoch 8 – Introduction to MVC in JSP/Servlets

1. What is MVC?

MVC (Model–View–Controller) is a software architectural pattern that separates the application into three main components:

Component	Responsibility	Example in the project
Model	Represents the data and business logic. Contains POJO classes and DAO classes for database operations.	User.java, Product.java, UserDAO.java, ProductDAO.java
View	Handles the presentation layer. Displays data to users using HTML, CSS, JSTL, EL. No JDBC code here.	login.jsp, home.jsp, product_list.jsp
Controller	Acts as an intermediary: receives requests, calls the Model for processing, and selects the View for the response.	LoginServlet.java, LogoutServlet.java, ProductServlet.java

2. MVC Flow

• The user submits a request (e.g., a login form).
• The Controller (Servlet) receives the request and retrieves form data.
• The Controller calls the Model (DAO) to process business logic and query the database.
• The Model returns the result to the Controller.
• The Controller sets attributes using request.setAttribute(…) and forwards to a View (JSP).
• The View renders the result to the user.

Flow Diagram:

3. Model 1 vs Model 2 (MVC)

Criteria	Model 1 (Direct JSP)	Model 2 (MVC)
Code organization	HTML, JDBC, and logic mixed in JSP	Separated into Model, View, Controller
Maintainability	Changing UI may break logic	UI and logic are separated, easier to maintain
Code reusability	Hard to reuse DAO/business logic	DAO and Model are reusable
Security	Logic code may be exposed to clients	Logic stays in Servlet, not exposed
Project scale	Fits small apps only	Scales well for medium/large projects

4. Benefits of Applying MVC to the E-Commerce Project

• Clear role separation: Frontend developers focus on JSP/Bootstrap, backend developers focus on DAO and Servlets.
• Easy to extend: Features like shopping cart and order management can be added without breaking existing code.
• Reusable DAO classes: For example, UserDAO can be used for both login and admin user management.
• Professional learning: Helps students become familiar with industry patterns like Spring MVC, JSF, Struts, etc.

5. Direction for Epoch 9

Follow this folder structure:

/src/
  ├── Controllers
  │     ├── LoginServlet.java
  │     ├── LogoutServlet.java
  ├── Models
  │     ├── User.java
  ├── DALs
  │     ├── UserDAO.java
  ├── Utils
  │     ├── DBContext.java
/webapp/
  ├── WEB-INF/
  │     ├── web.xml
  ├── views/
  │     ├── pages
  │     │     ├── login.jsp
  │     │     ├── home.jsp
  │     ├── layouts
  │     │     ├── layout.jsp

• Move all JDBC code from JSP to DAO classes in /DALs.
• Create Servlet Controllers for each function (e.g., LoginServlet, LogoutServlet).
• Ensure JSP pages only contain HTML + JSTL, no JDBC scriptlets.