login.jsp
```html
<%--
Created by IntelliJ IDEA.
User: wai shao de lenovo
Date: 2021/12/11
Time: 21:46
To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
<title>登录界面</title>
<style>
#frame_{
width: 500px;
height: 400px;
margin-left: 700px;
margin-top: 210px;
background-color: azure;
border: black solid 2px;
}
#inner_{
margin-left: 150px;
margin-top: 150px;
}
</style>
</head>
<body>
<div id="frame_">
<div id="inner_">
用户:<input type="test" id="u_id"><br><br>
密码:<input type="password" id="u_pwd"><br><br>
<button id="btn01">重置</button>
<button style="margin-left: 20px" id="btn02">登陆</button><br>
<span id="error" style= "color: red "></span>
<script>
let btn001 = document.getElementById("btn02");
btn001.onclick=function () {
let id_str = document.getElementById("u_id").value;
if(id_str==null||id_str=="") {
document.getElementById("error").innerHTML="账户不能为空！！"
return;
}
let pwd_str=document.getElementById("u_pwd").value;
if(pwd_str==null||pwd_str=="") {
document.getElementById("error").innerHTML="密码不能为空！！"
return;
}
//开始访问服务器
window.location.herf = "login?u_id="+id_str+"&u_pwd="+pwd_str;
}
</script>
</div>
</div>
</body>
</html>
LoginServlet
```java
package com.studentTest.servlet;
import com.studentTest.bean.User;
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.io.IOException;
/*
起名字，为了让前端页面能访问。
*/
@WebServlet("/login")
public class LoginServlet extends HttpServlet {
@Override
protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
String u_id=req.getParameter("u_id");
String u_pwd=req.getParameter("u_pwd");
User u = new User();
u.setU_id(Integer.valueOf(u_id));
u.setU_pwd(u_pwd);
System.out.println("账户："+u.getU_id()+" 密码："+u.getU_pwd());
}
}
找了好久不知道问题在哪，大 佬救 救 我。
