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Introduction to Servlets: Your First Servlet Program

Pankaj Sharma ·

In the world of web development, servlets are like the little helpers that run on a server and respond to requests from web browsers. If you’ve ever clicked a button on a website and seen the page change, there’s a good chance a servlet was involved!

What is a Servlet?

A servlet is a Java program that runs on a server. It handles requests (like clicking a button) and responses (like showing you a new webpage). Think of it as a waiter in a restaurant: you tell the waiter (the servlet) what you want (the request), and the waiter brings you your food (the response).

Your First Servlet Program

Let's dive into creating a simple servlet that says "Hello, World!" when you visit it.

Step-by-Step Guide

  1. Set Up Your Environment:
    • Java Development Kit (JDK): Make sure you have the JDK installed on your computer.
    • Apache Tomcat: This is a popular web server for running servlets. Download and install Apache Tomcat.
    • Integrated Development Environment (IDE): Use an IDE like Eclipse or IntelliJ IDEA to write your code.
  2. Create a New Project:
    • Open your IDE and create a new Dynamic Web Project (in Eclipse) or a new Web Application (in IntelliJ IDEA).
  3. Write Your Servlet Code:
    • Create a new Java class in your project. Name it HelloServlet.java.

Here's the code for our first servlet:

import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

@WebServlet("/hello")
public class HelloServlet extends HttpServlet {
private static final long serialVersionUID = 1L;

protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    response.setContentType("text/html");
    response.getWriter().println("<h1>Hello, World!</h1>");
}

}

Explaining the Code

  • Imports: At the top, we import the necessary classes. These classes help our servlet interact with web requests and responses.
  • @WebServlet("/hello"): This line tells the server that this servlet should respond to requests sent to the /hello URL.
  • doGet Method: This method handles GET requests. When someone visits the URL /hello, this method is called.
    • response.setContentType("text/html");: This tells the browser that we are sending back an HTML response.
    • response.getWriter().println("<h1>Hello, World!</h1>");: This sends back a simple HTML message: "Hello, World!"
  1. Deploy Your Servlet:
    • Copy your project to the webapps folder of your Tomcat installation.
    • Start Tomcat.
  2. Access Your Servlet:
    • Open your web browser and go to http://localhost:8080/your_project_name/hello.
    • You should see the message "Hello, World!" displayed on the page.