MVC (Model-View-Controller) is a design pattern used in JEE web applications where Servlets act as Controllers, JSP pages act as Views, and JavaBeans/DAO classes act as Models, providing a clear separation between presentation, business logic, and data access.

The Model contains:

• Business logic
• Data processing
• Database access (JDBC, JPA, Hibernate)
• JavaBeans

Example:

public class Student {
    private String matricNo;
    private String name;

    // Getter and Setter
}

or

public class StudentDAO {

    public Student getStudent(String matricNo) {
        // Retrieve data from database
    }
}

The View is responsible for:

• User Interface
• Displaying data
• Receiving user input

In JEE, View is usually:

• JSP
• HTML
• CSS
• JavaScript

Example:

<h2>Student Information</h2>
<p>Name: ${student.name}</p>
<p>Matric No: ${student.matricNo}</p>

The View should NOT contain database code.

The Controller acts as the middleman.

Responsibilities:

• Receive user requests
• Validate input
• Call Model
• Send data to View

In JEE, Controller is usually a Servlet.

Example:

@WebServlet("/student")
public class StudentServlet extends HttpServlet {

    protected void doGet(HttpServletRequest request,
                         HttpServletResponse response)
                         throws ServletException, IOException {

        StudentDAO dao = new StudentDAO();

        Student student = dao.getStudent("A123");

        request.setAttribute("student", student);

        RequestDispatcher rd =
            request.getRequestDispatcher("student.jsp");

        rd.forward(request, response);
    }
}

Browser
   |
   | Request
   v
Servlet (Controller)
   |
   | Calls
   v
Model (JavaBean/DAO)
   |
   | Returns Data
   v
Servlet (Controller)
   |
   | Forward
   v
JSP (View)
   |
   | Response
   v
Browser

1. User opens:

http://localhost:8080/login.jsp

2. Request goes to Servlet.
3. Servlet calls DAO.
4. DAO retrieves data from MySQL.
5. DAO returns data to Servlet.
6. Servlet stores data:

request.setAttribute("student", student);

7. Servlet forwards to JSP.
8. JSP displays the data.
9. Browser shows the result.

StudentMVC
│
├── src
│   └── my/zhamri
│       ├── Student.java
│       ├── StudentDAO.java
│       └── StudentServlet.java
│
├── webapp
│   ├── student.jsp
│   └── index.jsp
│
└── WEB-INF

<%
Connection con =
DriverManager.getConnection(...);

Statement stmt =
con.createStatement();

ResultSet rs =
stmt.executeQuery("SELECT * FROM student");
%>

Problems:

• SQL inside JSP
• Difficult to maintain
• Difficult to debug
• Poor scalability