JSP vs Servlet

JSP vs Servlet

JSP vs Servlet


In Java web development, JSP (JavaServer Pages) and Servlets are two fundamental technologies that form the foundation of many web applications. 

Even though modern frameworks like Spring MVC and Spring Boot are widely used today, they are internally built on top of servlets and often work alongside JSP for view rendering.

Understanding the differences between JSP and Servlets is essential for beginners, students, and developers maintaining legacy systems. 



1. Overview of JSP and Servlets

1.1 What Is a Servlet?

A Servlet is a Java class that runs on a web server and handles HTTP requests and responses. It is mainly responsible for:

  • Processing user requests

  • Executing business logic

  • Controlling application flow

Servlets typically generate data or decide which page should be displayed next.


1.2 What Is JSP?

JSP (JavaServer Pages) is a server-side technology designed to simplify the creation of dynamic web pages. JSP allows developers to write HTML directly and embed Java-based logic using tags and expressions.

In practice:

  • Servlets act as controllers

  • JSP acts as the view layer



2. Core Differences Between JSP and Servlets

Aspect Servlet JSP
Primary Purpose Business logic & control Presentation (UI)
Code Style Pure Java HTML + Java
Readability Lower Higher
Learning Curve Steeper Easier
Compilation Compiled Java class Converted into a servlet
Best Role Controller View


3. JSP and Servlet Relationship

A common misconception is that JSP and Servlets are competing technologies. In reality, they are complementary.

  • JSP is internally converted into a servlet by the server

  • Both run inside a servlet container (such as Apache Tomcat)

  • Modern MVC architecture uses Servlets for logic and JSP for views



4. JSP Practical Example

4.1 Simple JSP Example

This example demonstrates how JSP generates dynamic content.

4.1.1 hello.jsp 

<%@ page contentType="text/html; charset=UTF-8" %>
<html>
<head>
    <title>JSP Example</title>
</head>
<body>
    <h2>Welcome to JSP</h2>

    <%
        String name = request.getParameter("name");
        if (name == null) {
            name = "Guest";
        }
    %>

    <p>Hello, <%= name %>!</p>
</body>
</html>


4.1.2 How It Works

  1. The browser sends a request with a parameter

  2. JSP reads the parameter using request

  3. Dynamic content is generated and returned as HTML


4.1.3 Access URL 

http://localhost:8080/project-name/hello.jsp?name=Alice




5. Servlet Practical Example

5.1 Simple Servlet Example

This servlet handles a request and generates a response.

5.1.1 HelloServlet.java 

import jakarta.servlet.http.*;
import jakarta.servlet.annotation.WebServlet;
import java.io.IOException;

@WebServlet("/helloServlet")
public class HelloServlet extends HttpServlet {

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

        response.setContentType("text/html");
        response.getWriter().println("<h2>Hello from Servlet!</h2>");
    }
}


5.1.2 How It Works

  1. The servlet container maps the URL to the servlet

  2. doGet() processes the request

  3. The response is written directly to the browser


5.1.3 Access URL 

http://localhost:8080/project-name/helloServlet



6. Combining Servlet and JSP

The most common and recommended approach is to use Servlet + JSP together.

6.1 Servlet as Controller 

@WebServlet("/greet")
public class GreetServlet extends HttpServlet {

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

        request.setAttribute("username", "John");
        request.getRequestDispatcher("greet.jsp").forward(request, response);
    }
}


6.2 JSP as View 

<%@ page contentType="text/html; charset=UTF-8" %>
<html>
<body>
    <h2>Greeting Page</h2>
    <p>Hello, ${username}!</p>
</body>
</html>


6.3 Why This Is Better

  • Clear separation of concerns

  • Cleaner and more maintainable code

  • Easier debugging and testing



7. Advantages of JSP

  • Easier UI development

  • Better readability

  • Supports Expression Language (EL)

  • Works well with JSTL

  • Ideal for presentation logic



8. Advantages of Servlets

  • Strong control over request processing

  • Better for business logic

  • High performance

  • Thread-based request handling

  • Foundation of Java web frameworks



9. Disadvantages of JSP and Servlets

9.1 JSP Limitations

  • Scriptlets can make code messy

  • Not suitable for complex business logic

  • Legacy approach compared to modern templates


9.2 Servlet Limitations

  • Poor readability when generating HTML

  • Verbose code

  • Harder UI maintenance



10. JSP vs Servlet vs Modern Frameworks

Modern frameworks:

  • Abstract servlet complexity

  • Use JSP or template engines for views

  • Provide better architecture and scalability


However, learning JSP and Servlets is still valuable because:

  • Legacy systems depend on them

  • They explain how MVC works internally

  • They build a strong Java web foundation



11. When Should You Use JSP or Servlets?

11.1 Use JSP when:

  • Rendering UI pages

  • Displaying dynamic data

  • Building traditional web views


11.2 Use Servlets when:

  • Handling requests and responses

  • Implementing business logic

  • Acting as a controller



12. Conclusion

JSP and Servlets are not rivals but partners in Java web development. 

Servlets provide powerful request handling and control logic, while JSP simplifies UI rendering and improves code readability. 

When used together following the MVC pattern, they create clean, scalable, and maintainable web applications.

Even in the era of Spring Boot and modern frameworks, understanding JSP and Servlets remains an essential skill. 

It allows developers to maintain legacy systems, understand framework internals, and build a solid foundation in Java web development.

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