How to Run Servlet in Tomcat?

Servlets are Java programs that run on a web server and handle client requests. In this article, we will learn how to create, compile, configure, and run a simple Hello World Servlet in Apache Tomcat without using any Java IDE like Eclipse.

Create and compile a basic servlet using Java.
Configure the servlet in the web.xml file.
Deploy and run the servlet on the Apache Tomcat server.

Note: Running a server like Tomcat to run our servlet. if it is not already installed, you can install it using this article: How to Install Apache Tomcat on Windows?

Basic Terms we Know

we have a awareness for these terms before directly running a servlet Application

GenericServlet

it is a protocol-independent servlet class that can be extended for different protocols like HTTP, FTP, and SMTP.
Provides implementations of init() and destroy() methods.
Implements the ServletConfig interface.
Used as the parent class for protocol-specific servlets.

HttpServlet

HttpServlet is used for handling HTTP requests in web applications.
Provides implementation for the service() method.
Calls doGet() for GET requests and doPost() for POST requests.
Commonly used for developing web-based servlets.

Prerequisites

Java JDK installed
Apache Tomcat Server installed
Command Prompt and Text Editor

Steps For Creating Servlet Program Using Text Editor

Follow these steps to create a simple Servlet program without Using any IDE.

Step 1: Create Project Directory Structure

Since we are not using any IDE, first create the required directory structure manually inside the webapps folder of Tomcat.

classes folder stores the compiled servlet class files.
WEB-INF contains configuration files for the web application.

TOMCAT_HOME
└── webapps
└── net
└── WEB-INF
├── classes
└── web.xml

Step 2: Create Servlet File

Create a file named HelloWorldServlet.java using any text editor.

Java

import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;

public class HelloWorldServlet extends HttpServlet {

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

        response.setContentType("text/html");

        PrintWriter out = response.getWriter();

        out.println("<html>");
        out.println("<body>");
        out.println("<h1>Hello World!</h1>");
        out.println("</body></html>");

        out.close();
    }
}

Step 3: Compile the Servlet

Compile the servlet using Command Prompt.

javac HelloWorldServlet.java

Step 4: Place Class File

Copy the generated HelloWorldServlet.class file into the WEB-INF/classes folder.

The servlet container loads classes from this directory.
Tomcat uses this class during request processing.

Step 5: Configure Servlet in web.xml

Add servlet configuration in the web.xml file.

<servlet>
<servlet-name>HelloWorld</servlet-name>
<servlet-class>HelloWorldServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>HelloWorld</servlet-name>
<url-pattern>/servlet/HelloWorld</url-pattern>
</servlet-mapping>

Step 6: Start Tomcat Server

Start Tomcat server and it loads and initializes the servlet and servlet becomes ready to handle requests.

Step 7: Access the Servlet

Open the browser and enter the following URL

http://localhost:8080/net/servlet/HelloWorld

Output:

Explanation: The response is displayed in the browser The request is handled by doGet().