大家帮我看一下我的eclipse和mysql为什么连接不成功？

第一次接触jsp，想利用eclipse和mysql完成账户登录跳转学校网站
但是点击登录后跳转到了只有几个问号的界面
麻烦大家帮我看一下
我的代码如下：
login.jsp

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Insert title here</title>

<script type="text/javascript">
    function check(form){
        if(form.username.value==""){
            alert("用户名不能为空！");
            return false;
        }
        if(form.password.value==""){
            alert("密码不能为空！");
            return false;
        }
    }
</script>
</head>
<body>
<div class=div>
    <form action="LoginServlet" method="post" onsubmit="return check(this);">
        <label>用户名：</label><input type="text" name="username">
        <label>密码：</label><input type="text" name="password">
        
        <input type="submit" value="登录" />

    </form>
</div>
</body>
</html>

LoginServlet.java

package com.pzy.user;

import java.io.IOException;

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 java.sql.*;

/**
 * Servlet implementation class LoginServlet
 */
@WebServlet("/LoginServlet")
public class LoginServlet extends HttpServlet {
    private static final long serialVersionUID = 1L;
       
    /**
     * @see HttpServlet#HttpServlet()
     */
    public LoginServlet() {
        super();
        // TODO Auto-generated constructor stub
    }

    /**
     * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
     */
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
        response.getWriter().append("Served at: ").append(request.getContextPath());
    }

    /**
     * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
     */
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
        //doGet(request, response);
        
        //1.获取用户输入的用户名和密码
        String name= request.getParameter("username");
        String password= request.getParameter("password");
        
        boolean flag=false;
        //2.创建数据库的连接
        
        Connection connection=null;
        PreparedStatement pStatement=null;
        ResultSet rSet=null;
        
        try {
            Class.forName("com.mysql.jdbc.Driver");
            String url="jdbc:mysql://127.0.0.1:3306/testdb";
            connection= DriverManager.getConnection(url,"root","20020404");
        
        //3.连接后执行mysql语句命令并返回执行结果
            String sql="select username,password from tb_user where username=? and password=?";
            pStatement= connection.prepareStatement(sql);
            pStatement.setString(1, name);
            pStatement.setString(2, password);
            
            rSet= pStatement.executeQuery();
            
            if(rSet.next()) {
                flag=true;
                
            }
            rSet.close();
            pStatement.close();
            connection.close();
            
        } catch (Exception e) {
            e.printStackTrace();
        }
        
        //4.根据执行结果做出相应处理
        if(!flag)
        {
            response.getWriter().println("用户名或密码错误！");
        }
        else
        {
            response.sendRedirect("https://www.tsinghua.edu.cn/");
        }
    }

}



response.getWriter().println("用户名或密码错误！");

返回了用户名或者密码错误吧
乱码可以在doPost方法体开头加上


response.setCharacterEncoding("utf-8");    //设置 HttpServletResponse使用utf-8编码
response.setHeader("Content-Type", "text/html;charset=utf-8");  //设置响应头的编码

页面返回？？？ 应该是中文乱码了！建议先把中文乱码问题解决一下，百度一下有很多解决方式；

把页面贴出来