Jsp,servlet,aws my qu. is when i deploy my website it shows error when click on submit button ,404,500

http://nitin.digital This my website of jsp servlet. And when I Deploy in aws ec2 please help me in this project how to remove errors 404 and 500. when I click on send message button in this I install java version 15 on local host and on server side on aws ubuntu I use java version 11. is there any issue.

this is the image link of html or jsp file https://i.stack.imgur.com/FC6Aw.png the error is in this link shows 500 https://i.stack.imgur.com/K4v6V.jpg and after this it shows error 404 https://i.stack.imgur.com/JReDs.png please clarify me how can I eliminate this error.

my code is this `

package com.servlet;




import java.io.IOException;
import java.io.PrintWriter;

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

import dao.CredentiaDAO;



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

    
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        
            response.setContentType("text/html");
            PrintWriter out=response.getWriter();
            String firstname=request.getParameter("firstname");
            String laststname=request.getParameter("Laststname");
            
            String email=request.getParameter("email");
            String phone=request.getParameter("phone");
            String comment=request.getParameter("comment");
            
            model.Credentia obj=new model.Credentia();
            obj.setFirstname(firstname);
            obj.setLaststname(laststname);
            
            obj.setEmail(email);
            obj.setPhone(phone);
            obj.setComment(comment);
            
            
            try {
            CredentiaDAO objDAO=new CredentiaDAO();
            objDAO.insertCredentia(obj);
            }
            catch(Exception e)
            {out.println("Exception Arised:"+e);
            }
            out.println(firstname);
            out.println(laststname);
            out.println(email);
    out.println(phone);
    out.println(comment);
    response.sendRedirect("index.jsp");
    }

}


 package com.servlet;
    
    
    
    
    import java.io.IOException;
    import java.io.PrintWriter;
    
    import javax.servlet.ServletException;
    import javax.servlet.annotation.WebServlet;
    import javax.servlet.http.HttpServlet;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    
    import dao.CredentialDAO;
    
    
    @WebServlet("/registerServlet")
    public class registerServlet extends HttpServlet {
        private static final long serialVersionUID = 1L;
    
        
        protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
            
                response.setContentType("text/html");
                PrintWriter out=response.getWriter();
                String username=request.getParameter("username");
                String email=request.getParameter("email");
                
                String phone=request.getParameter("phonenumber");
                String possible=request.getParameter("possibledateforvisit");
                String subject=request.getParameter("subject");
                String additionalmessage=request.getParameter("additionalmessage");
                
                model.Credential obj=new model.Credential();
                obj.setUsername(username);
                obj.setEmail(email);
                
                obj.setPhonenumber(phone);
                obj.setPossibledateforvisit(possible);
                obj.setSubject(subject);
                obj.setAdditionalmessage(additionalmessage);
                
                try {
                CredentialDAO objDAO=new CredentialDAO();
                objDAO.insertCredential(obj);
                }
                catch(Exception e)
                {out.println("Exception Arised:"+e);
                }
                response.sendRedirect("index.jsp");
    
        }
    
    }





<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
  <modelVersion>4.0.0</modelVersion>
  <groupId>square-i</groupId>
  <artifactId>square-i</artifactId>
  <version>0.0.1-SNAPSHOT</version>
  <packaging>war</packaging>
  <build>
    <sourceDirectory>src</sourceDirectory>
    <plugins>
      <plugin>
        <artifactId>maven-compiler-plugin</artifactId>
        <version>3.8.1</version>
        <configuration>
          <release>15</release>
        </configuration>
      </plugin>
      <plugin>
        <artifactId>maven-war-plugin</artifactId>
        <version>3.2.3</version>
        <configuration>
          <warSourceDirectory>WebContent</warSourceDirectory>
        </configuration>
      </plugin>
    </plugins>
  </build>
  
  
  <dependencies>
        <!-- https://mvnrepository.com/artifact/javax.servlet/javax.servlet-api -->
<dependency>
    <groupId>javax.servlet</groupId>
    <artifactId>javax.servlet-api</artifactId>
    <version>3.1.0</version>
    <scope>provided</scope>
</dependency>

</dependencies>
</project>

<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://xmlns.jcp.org/xml/ns/javaee" xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd" id="WebApp_ID" version="3.1">
  <display-name>square-i</display-name>
  <welcome-file-list>
    <welcome-file>index.html</welcome-file>
    <welcome-file>index.htm</welcome-file>
    <welcome-file>index.jsp</welcome-file>
    <welcome-file>default.html</welcome-file>
    <welcome-file>default.htm</welcome-file>
    <welcome-file>default.jsp</welcome-file>
  </welcome-file-list>
 </web-app>