jsp转到servlet出现错误


<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>首页</title>
</head>
<body>
    ${message }<br>
    <form action="${pageContext.request.contextPath }/loginServlet" method="POST">
        学号：<input type="text" name="num"/><br>
        密码：<input type="password" name="password"/><br>
        <input type="submit" value="登录">
    </form>
    <a href="#">注册</a>
</body>
</html>

package com.project.sms.servlets;

import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

import com.project.sms.beans.Student;
import com.project.sms.service.IStudentService;
import com.project.sms.service.StudentServiceImpl;


//servlet调用service
public class LoginServlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {

        // 1.接受请求参数
        String num = request.getParameter("num");
        String password = request.getParameter("password");
// 4.验证未通过，则跳转到登录页面，让用户再次输入登录信息。此时页面需要给出用户一些提示
        if(student == null) {
            session.setAttribute("message", "用户名或密码输入有误");
            response.sendRedirect(request.getContextPath() + "/login.jsp");
            return;
        }
        // 5.验证通过，则跳转到系统主页index.jsp
        response.sendRedirect(request.getContextPath() + "/index.jsp");
    }

}

在初始页面login.jsp输入学号密码后点击登录报错：
HTTP Status 404 – Not Found
Type Status Report

Message /sms/loginServlet

Description The origin server did not find a current representation for the target resource or is not willing to disclose that one exists.

我在创建servlet时设置了URL Mapping为/loginServlet，现在就是页面跳转不到index.jsp
，请问这是怎么回事？

form表单的action直接写 /loginServlet 看看吧