Java 我的登录servlet页面出现问题，显示tomcat错误

这个项目在我的另一台（坏了的）计算机上运行得很好，但是今天我在我的新lapotp上打开了这个项目，它就是这样，我不知道我能做什么。我不知道问题出在哪里。三个月前我做这件事的时候一切都很好。我以为我没有连接到我的数据库，但一切都很好。

my web.xml：

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" id="WebApp_ID" version="3.0">
  <display-name>E-shopping</display-name>
  <welcome-file-list>
    <welcome-file>index.jsp</welcome-file>
  </welcome-file-list>
  <servlet>
    <servlet-name>Login</servlet-name>
    <servlet-class>com.example.controller.LoginServlet</servlet-class>
  </servlet>
  <servlet-mapping>
    <servlet-name>Login</servlet-name>
    <url-pattern>/LoginServlet</url-pattern>
  </servlet-mapping>
  <servlet>
    <servlet-name>Signup</servlet-name>
    <servlet-class>com.example.controller.SignUpServlet</servlet-class>
  </servlet>
  <servlet-mapping>
    <servlet-name>Signup</servlet-name>
    <url-pattern>/SignUpServlet</url-pattern>
  </servlet-mapping>
  <servlet>
    <servlet-name>Logout</servlet-name>
    <servlet-class>com.example.controller.Logout</servlet-class>
  </servlet>
  <servlet-mapping>
    <servlet-name>Logout</servlet-name>
    <url-pattern>/Signout</url-pattern>
  </servlet-mapping>
  <servlet>
    <servlet-name>CartServlet</servlet-name>
    <servlet-class>com.example.controller.CartServlet</servlet-class>
  </servlet>
  <servlet-mapping>
    <servlet-name>CartServlet</servlet-name>
    <url-pattern>/Cart</url-pattern>
  </servlet-mapping>
  <servlet>
    <servlet-name>HeartServlet</servlet-name>
    <servlet-class>com.example.controller.HeartServlet</servlet-class>
  </servlet>
  <servlet-mapping>
    <servlet-name>HeartServlet</servlet-name>
    <url-pattern>/Heart</url-pattern>
  </servlet-mapping>
  <servlet>
      <servlet-name>BillingController</servlet-name>
      <servlet-class>com.example.controller.BillingServlet</servlet-class>
  </servlet>
  <servlet-mapping>
      <servlet-name>BillingController</servlet-name>
      <url-pattern>/Billing</url-pattern>
  </servlet-mapping>
  <servlet>
    <description></description>
    <display-name>Controller</display-name>
    <servlet-name>Controller</servlet-name>
    <servlet-class>com.controller.Controller</servlet-class>
  </servlet>
  <servlet-mapping>
    <servlet-name>Controller</servlet-name>
    <url-pattern>/Controller</url-pattern>
  </servlet-mapping>

</web-app>

package com.example.controller;

import java.io.*;
import java.sql.*;

import javax.servlet.RequestDispatcher;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

/**
 * Servlet implementation class LoginServlet
 */

public class LoginServlet extends HttpServlet {
    private static final long serialVersionUID = 1L;
       Connection con;
       Statement stmt;
       ResultSet rs;
    /**
     * @see HttpServlet#HttpServlet()
     */
    public LoginServlet() {
        super();

    }

   
    /**
     * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
     */
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

    }

    /**
     * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
     */
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        
        HttpSession sess=request.getSession();
        
        String username=request.getParameter("user");
        String pwd=request.getParameter("password");
                
        
        
        try {
            
            con=DBConnection.getConnection();
            
            stmt=con.createStatement();
            rs=stmt.executeQuery("select * from user_reg");
            
            RequestDispatcher rd;
            
            while(rs.next())
            {
                if(username.equals(rs.getString("user_name"))&& pwd.equals(rs.getString("passwd")))
                {
                    String name=rs.getString("name");
                    int id = rs.getInt("uid");
                    sess.setAttribute("user", name);
                    sess.setAttribute("id", id);
                    rd=request.getRequestDispatcher("/logsucc.jsp");
                    rd.forward(request, response);
                    
                }
            }
            
            rd=request.getRequestDispatcher("/logincust.jsp");
            rd.forward(request, response);
            
        } catch (SQLException e) {

            e.printStackTrace();
        }
        finally
        {
            try {
                con.close();
            } catch (SQLException e) {

                e.printStackTrace();
            }
        }
        
    }

}