http servlets

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HttpServlet is an abstract class in the Java Servlet API that provides a convenient way to handle HTTP requests and responses. HttpServlet extends the GenericServlet class and provides additional methods for handling HTTP-specific features such as cookies, sessions, and form data.

To use HttpServlet, we define a new class that extends HttpServlet and override its methods to handle HTTP requests. Here's an example of a simple HttpServlet that responds to GET requests with a "Hello, World!" message:

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

public class HelloWorld extends HttpServlet {

  public void doGet(HttpServletRequest request, HttpServletResponse response)
      throws ServletException, IOException {
      
    // Set response content type
    response.setContentType("text/html");

    // Actual logic goes here.
    PrintWriter out = response.getWriter();
    out.println("<html><body>");
    out.println("# Hello, World!");
    out.println("</body></html>");
  }
}

In this example, we define a new servlet class called HelloWorld that extends the HttpServlet class. The doGet() method is overridden to handle GET requests, and it simply generates an HTML response that says "Hello, World!"

To deploy this servlet, we need to compile it and package it as a WAR (Web Application Archive) file. We can then deploy the WAR file to a servlet container such as Apache Tomcat.

Assuming we have deployed the WAR file to a servlet container running on localhost at port 8080, we can access the servlet by visiting http://localhost:8080/HelloWorld in a web browser. This will send a GET request to the servlet, which will respond with the "Hello, World!" message.