How to solve error "java.lang.ClassCastException: Cookie.FirstServlet cannot be cast to jakarta.servlet.Servlet"

Question

I'm facing a problem right now. I just started learning servlets and when I tried to run the program, it shows an error. I tried looking for ways to solve them like adding javax.servlet.jar but couldn't solve the issue. I'm currently using NetBeans 12.4. This is the code I have.

HTML code:

< html >
< head >
    < title >Cookies< /title >
< /head >
< body >
    < form action=`FirstServlet' method="post" >
        Name:< input type="text" name="userName"/ >< br/ >
        < input type="submit" value="go"/ >
    < /form >
< /body >
< /html >

FirstServlet code:

package Cookie;
import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.Cookie;
public class FirstServlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        response.setContentType("text/html;charset=UTF-8");
        try (PrintWriter out = response.getWriter()) {
            String n=request.getParameter("userName");
            out.print("Welcome"+n);
            Cookie ck= new Cookie("uname",n);
            response.addCookie(ck);
            out.print("<form action='servlet2'>");
            out.print("<input type='submit' value='Next page'>");
            out.print("</form");
            out.close();
        }catch(Exception e){
            System.out.println(e);
        }
    }
}

Web.xml:

< ?xml version="1.0" encoding="UTF-8"? >
< web-app version="4.0" 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" >
< servlet >
    < servlet-name >FirstServlet< /servlet-name >
    < servlet-class >Cookie.FirstServlet< /servlet-class >
< /servlet >
< servlet >
    < servlet-name >servlet2< /servlet-name >
    < servlet-class >Cookie.servlet2< /servlet-class >
< /servlet >
< servlet-mapping >
    < servlet-name >FirstServlet< /servlet-name >
    < url-pattern >/FirstServlet< /url-pattern >
< /servlet-mapping >
< servlet-mapping >
    < servlet-name >servlet2< /servlet-name >
    < url-pattern >/servlet2< /url-pattern >
< /servlet-mapping >
< session-config >
    < session-timeout >
        30
    < /session-timeout >
< /session-config >
< /web-app >

Servlet2 code:

package Cookie;

import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.Cookie;
public class servlet2 extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response)
        throws ServletException, IOException {
    response.setContentType("text/html;charset=UTF-8");
    try (PrintWriter out = response.getWriter()) {
        Cookie ck[]=request.getCookies();
        out.print("Servlet 2"+ ck[0].getValue());
        out.close();
    }catch(Exception e){
        System.out.println(e);
    }
}
}

And this is the error I have:

HTTP Status 500 - Internal Server Error type Exception report

message: Internal Server Error

description: The server encountered an internal error that prevented it from fulfilling this request.

exception

jakarta.servlet.ServletException: Class Cookie.FirstServlet is not a Servlet root cause

java.lang.ClassCastException: Cookie.FirstServlet cannot be cast to jakarta.servlet.Servlet note The full stack traces of the exception and its root causes are available in the Eclipse GlassFish 6.0.0 logs.

Eclipse GlassFish 6.0.0