当我发送表单时，它会执行action="userlogin"method="post"。这是我的代码：

package com.home_project.oop_project.controllers;

import java.sql.*;
import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.*;

@Controller
public class UserController {

int adminlogcheck = 0;
String usernameforclass = "";

//Some code
@GetMapping("userlogin")
public String userlog(Model model) {
    
    return "userLogin";
}
@RequestMapping(value = "userlogin", method = RequestMethod.POST)
public String userlogin( @RequestParam("username") String username, @RequestParam("password") String pass,Model model) {
    try
    {
        System.out.println(username);
        Class.forName("com.mysql.jdbc.Driver");
        Connection con = DriverManager.getConnection("jdbc:mysql://localhost:3306/springproject","root","");
        Statement stmt = con.createStatement();
        ResultSet rst = stmt.executeQuery("select * from users where username = '"+username+"' and password = '"+ pass+"' ;");
        if(rst.next()) {
            usernameforclass = rst.getString(2);
            return "redirect:/index";
            }
        else {
            model.addAttribute("message", "Invalid Username or Password");
            return "userLogin";
        }
        
    }
    catch(Exception e)
    {
        System.out.println("Exception:"+e);
    }
    return "userLogin";
    }
}

但它不会像我预期的那样转到'index'。当我通过postman检查问题时，它说：""trace"："org. springframe.web.bind.MissingServletRequest estParameterException：方法参数类型String的必需请求参数'username'不存在\r\n\tat"和"message"："必需参数'username'不存在。"我该怎么办。谢谢