.png)
If you are a B.Tech student (especially CSE/IT), then you must have seen the word Servlet in your Java or Web Technology subject. I still remember when I first saw it in 3rd semester. It sounded very complicated. But honestly, once I understood how it actually works, it became one of the easiest backend concepts.
In simple words, Servlet is a Java program that runs on a server and handles client requests.
Whenever you:
- Fill a login form
- Submit exam registration
- Book a train ticket online
There is some backend program processing your request. That backend program can be a Servlet.
In this blog, we will understand:
Let’s start step by step.
What is a Servlet?
A Servlet is a server-side Java class used to create dynamic web applications.
It runs inside a Servlet Container like Apache Tomcat and handles HTTP requests and responses.
Exam Definition
A Servlet is a server-side Java program that processes client requests and generates dynamic responses.
Servlet Syntax (Very Important for Exams & Practicals)
Many students understand theory but get confused in syntax. When I first wrote my Servlet in lab, I made so many small mistakes like missing import statements.
Let’s see the basic syntax properly.
Basic Servlet Syntax Using HttpServlet
import java.io.IOException;
import java.io.PrintWriter;
import jakarta.servlet.ServletException;
import jakarta.servlet.annotation.WebServlet;
import jakarta.servlet.http.HttpServlet;
import jakarta.servlet.http.HttpServletRequest;
import jakarta.servlet.http.HttpServletResponse;
@WebServlet("/MyServlet")
public class MyServlet extends HttpServlet {
// Initialization method
public void init() throws ServletException {
System.out.println("Servlet Initialized");
}
// Handles GET request
protected void doGet(HttpServletRequest request,
HttpServletResponse response)
throws ServletException, IOException {
response.setContentType("text/html");
PrintWriter out = response.getWriter();
out.println("<h1>Hello Students!</h1>");
out.println("<p>This is my first Servlet.</p>");
}
// Handles POST request
protected void doPost(HttpServletRequest request,
HttpServletResponse response)
throws ServletException, IOException {
String name = request.getParameter("username");
response.setContentType("text/html");
PrintWriter out = response.getWriter();
out.println("<h2>Welcome " + name + "</h2>");
}
// Destroy method
public void destroy() {
System.out.println("Servlet Destroyed");
}
}
Important Points in Syntax
Let’s understand what is happening here.
Extending HttpServlet
public class MyServlet extends HttpServlet
This means our class is inheriting features of HttpServlet.
Basically, without extending HttpServlet, it won’t behave like a Servlet.
@WebServlet Annotation
@WebServlet("/MyServlet")
This maps the Servlet to a URL pattern.
Instead of writing mapping in web.xml, we use annotation. It is simpler and modern.
doGet() Method
Used when client sends GET request.
Example:
- Opening a webpage
- Clicking a link
doPost() Method
Used when client submits form data.
Example:
- Login form
- Registration form
request and response Objects
HttpServletRequest → Used to get client data
HttpServletResponse → Used to send response
Many students get confused here. Just remember:
Request = Incoming data
Response = Outgoing data
Servlet Life Cycle
This is one of the most important theory questions.
Servlet life cycle has three main methods:
- init()
- service()
- destroy()
init() Method
Called only once when Servlet is loaded.
Used for:
- Database connection
- Resource initialization
I remember this as:
init() = Setup time
service() Method
Called for every request.
Internally it calls:
- doGet()
- doPost()
So whenever user sends request, service() handles it.
destroy() Method
Called once before Servlet is removed.
Used to:
- Close database connection
- Free resources
Life Cycle Flow
- Client sends request
- Servlet is loaded
- init() is called
- service() is called for each request
- destroy() is called when server stops
How Servlet Works
Let’s understand this with a simple college example.
Imagine you created a login form for your college mini project.
Step 1: User Enters Data
User enters:
- Username
- Password
Clicks submit.
Step 2: Request Sent to Server
Browser sends HTTP request to Tomcat server.
Step 3: Servlet Container
Servlet container:
- Checks URL mapping
- Finds correct Servlet
- Calls doPost()
Step 4: Processing Logic
Inside doPost():
request.getParameter("username");
Connect to database
Validate user
Step 5: Send Response
PrintWriter out = response.getWriter();
Browser shows result.
Simple Working Diagram
Client → Server → Servlet Container → Servlet → Database → Response → Client
Advantages of Servlet
Now let’s see why we use it.
Fast Performance
Uses threads instead of creating new process like CGI.
Better for multiple users.
Platform Independent
Runs on any OS with JVM.
Secure
Java provides strong security features.
Scalable
Can handle many users at same time.
Foundation for Spring
Spring Boot internally uses Servlet API.
So learning Servlet makes backend journey easier.
Use Cases of Servlet
Login System
Most common use case in student projects.
Registration Forms
Storing student data into database.
Online Result Portal
Fetching marks from database.
E-commerce Websites
Handling cart and orders.
Banking Applications
Processing transactions securely.
Servlet vs JSP (Quick Comparison)
| Feature | Servlet | JSP |
|---|---|---|
| Type | Java Class | HTML + Java |
| Used For | Backend Logic | Frontend View |
| Code Style | More Java | More HTML |
| Role | Controller | View |
In simple words:
Servlet = Brain
JSP = Face
FAQs
What is Servlet Container?
It is a part of web server that manages Servlets. Example: Apache Tomcat.
What is difference between GET and POST?
GET → Data visible in URL
POST → Data hidden and more secure
Is Servlet outdated?
No. It is foundation of modern Java backend frameworks.
Can we connect database using Servlet?
Yes, using JDBC.
Is Servlet important for exams?
Yes, especially life cycle and working.
Conclusion
So friends, this was a complete and beginner-friendly explanation of Servlet including syntax.
When I first learned Servlet in lab, I was honestly confused. But once I built small projects like login form and student registration system, everything started making sense.
If you:
- Understand syntax properly
- Remember life cycle
- Practice small programs
Then Servlet becomes very easy.
And trust me, once you master Servlet, learning Spring Boot feels much smoother.
Keep practicing, build small backend projects, and don’t just read theory.
That’s how we actually grow as engineers 🚀
Read Also : What is JDBC in Java? Complete Beginner Guide with Architecture & CRUD
.png)