Write the steps to create and run servlet program. Explain with example.

Creating and running a servlet in Java involves several steps, including setting up a development environment, creating the servlet class, configuring deployment descriptors, and deploying the servlet to a servlet container. In this explanation, we’ll use a simple example to guide you through the process of creating and running a basic servlet.

Steps to Create and Run a Servlet in Java

Step 1: Set Up the Development Environment:

1. Install Java Development Kit (JDK):
   • Ensure that you have the Java Development Kit (JDK) installed on your system. You can download it from the official Oracle website or use an OpenJDK distribution.
2. Install an Integrated Development Environment (IDE):
   • Choose an IDE for Java development. Popular choices include Eclipse, IntelliJ IDEA, and NetBeans. Install and set up the chosen IDE.

Step 2: Create a Dynamic Web Project:

1. Create a New Dynamic Web Project:
   • Open your IDE and create a new Dynamic Web Project. This project type is suitable for web applications and servlet development.
2. Configure Project Settings:
   • Set up project settings, including the project name, runtime (select a servlet container, such as Apache Tomcat), and target runtime version.

Step 3: Create a Servlet Class:

1. Create a Servlet Class:
   • In the src folder of your Dynamic Web Project, create a new Java class that extends HttpServlet. This class will represent your servlet.

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

public class MyServlet extends HttpServlet {
    protected void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        // Servlet logic for handling GET requests
        response.getWriter().println("Hello, this is my servlet!");
    }
}

1. In this example, the doGet method is overridden to handle HTTP GET requests. It simply writes a “Hello, this is my servlet!” message to the response.
2. Configure Deployment Descriptors:
   • Open the web.xml file in the WEB-INF folder (create it if it doesn’t exist) and configure the servlet and its mapping.

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd"
         version="4.0">
    <servlet>
        <servlet-name>MyServlet</servlet-name>
        <servlet-class>com.example.MyServlet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>MyServlet</servlet-name>
        <url-pattern>/my-servlet</url-pattern>
    </servlet-mapping>
</web-app>

1. This configuration associates the servlet class MyServlet with the URL pattern /my-servlet.

Step 4: Deploy and Run the Servlet:

1. Deploy to Servlet Container:
   • Deploy your Dynamic Web Project to a servlet container. This involves packaging your application and deploying it to the servlet container’s webapps directory.
2. Start the Servlet Container:
   • Start the servlet container. If you are using Apache Tomcat, you can start it by running the startup.sh or startup.bat script in the Tomcat bin directory.
3. Access the Servlet:
   • Open a web browser and navigate to http://localhost:8080/your-project-name/my-servlet. Adjust the port and context path based on your servlet container configuration.
   You should see the “Hello, this is my servlet!” message, indicating that your servlet is successfully running.

Explanation with Example:

Let’s break down the key components of the example:

Servlet Class (MyServlet):

The MyServlet class extends HttpServlet, which is part of the Java Servlet API. It overrides the doGet method to handle HTTP GET requests.

public class MyServlet extends HttpServlet {
    protected void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        // Servlet logic for handling GET requests
        response.getWriter().println("Hello, this is my servlet!");
    }
}

Here, the doGet method is responsible for processing GET requests. It obtains the PrintWriter from the response and writes the “Hello, this is my servlet!” message.

Deployment Descriptors (web.xml):

The web.xml file is a deployment descriptor that configures servlets and their mappings. In this example, it associates the MyServlet class with the URL pattern /my-servlet.

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd"
         version="4.0">
    <servlet>
        <servlet-name>MyServlet</servlet-name>
        <servlet-class>com.example.MyServlet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>MyServlet</servlet-name>
        <url-pattern>/my-servlet</url-pattern>
    </servlet-mapping>
</web-app>

MyServlet com.example.MyServlet MyServlet /my-servlet