密码错误，未提示错误信息

<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<!DOCTYPE html>
<html>
    <head>
        <meta charset="UTF-8">
        <title>登录</title>
        <link rel="stylesheet" href="${pageContext.request.contextPath}/css/login.css">
    </head>
    <body>

        <div class="login">
            <div class="header">
                <h1>
                    <a href="/login.do">登录</a>
                </h1>
                <button></button>
            </div>

            <form action="/login.do" method="post">
                <div class="name">
                    <input type="text" id="name" name="username">
                    <p></p>
                </div>
                <div class="pwd">
                    <input type="password" id="pwd" name="password">
                    <p></p>
                </div>
                <div class="btn-red">
                    <input type="submit" value="登录" id="login-btn">
                </div>
                <div class="error">
<c:if test="${USER.username}==null">
                        <span class="error"> ${MSG}</span>
</c:if>
                </div>
            </form>
        </div>
    </body>
</html>

//    /toLogin.do           /login.jsp
public void toLogin(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    request.getRequestDispatcher("login.jsp").forward(request,response);
}
//      /login.do
public void login(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
String username =request.getParameter("username");
String password = request.getParameter("password");
User user = userService.get(username,password);
if(user==null){
        response.sendRedirect("toLogin.do");
        request.setAttribute("MSG","密码或用户名错误，请重新登录");
    }else{
HttpSession session = request.getSession();
session.setAttribute("USER",user);
        response.sendRedirect("../category/list.do");
    }
}

复java_n 2021-04-27

源自：项目：人员管理系统开发 6-4 项目作业

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3回答

好帮手慕小脸 2021-04-28 18:36:47

同学你好，这里同学访问的是login.do吧？如果是，出现这种情况是正常的，这里应先访问jsp，然后输入用户名和密码，点击登录跳转至表单对应的路径上(login.do)，举例如下：

祝学习愉快~

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好帮手慕小脸 2021-04-27 18:59:49

同学你好，如下代码位置处，将其修改为请求转发再试试:

祝学习愉快~

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提问者复java_n #1

还是没有输出输入错误的提示呀

2021-04-28 14:06:15
好帮手慕小脸回复提问者复java_n #2
同学你好，先进行setAttribute然后再进行请求转发：
```
if(user==null){
request.setAttribute("MSG","密码或用户名错误，请重新登录");
//请求转发
}
```
祝学习愉快~
2021-04-28 15:17:56

提问者复java_n 回复好帮手慕小脸 #3

按照老师的说法修改了，还没有输入账号和密码的时候就显示了

//    /toLogin.do           /login.jsp
public void toLogin(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    request.getRequestDispatcher("login.jsp").forward(request, response);
}

//      /login.do
public void login(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
String username = request.getParameter("username");
String password = request.getParameter("password");
User user = userService.get(username, password);
if (user == null) {
        request.setAttribute("MSG", "密码或用户名错误，请重新登录");
        request.getRequestDispatcher("toLogin.do").forward(request, response);

    } else {
HttpSession session = request.getSession();
session.setAttribute("USER", user);
        response.sendRedirect("../category/list.do");
    }
}

<form action="/login.do" method="post">
    <div class="name">
        <input type="text" id="name" name="username">
        <p></p>
    </div>
    <div class="pwd">
        <input type="password" id="pwd" name="password">
        <p></p>
    </div>
    <div class="btn-red">
        <input type="submit" value="登录" id="login-btn">
    </div>
${MSG}
</form>