Spring boot SpelEvaluationException：属性或字段'；用户名'；在null上找不到

我的项目基于springboot和bootstrap，我将保留用户名 当一个人错误地登录时，但我不想使用ajax。所以我使用thymeleaf来显示来自模型的消息。这是我的项目入口：

@Configuration
public class WebMvcConfigure extends WebMvcConfigurerAdapter {

@Override
public void addViewControllers(ViewControllerRegistry registry) {
    ModelMap modelMap = new ModelMap();
    modelMap.addAttribute("user", new User());
    registry.addViewController("/").setViewName("pages/admin3/login_soft");
    registry.setOrder(Ordered.HIGHEST_PRECEDENCE);
    super.addViewControllers(registry);
    String os = System.getProperty("os.name");
    if(os.toLowerCase().startsWith("win")){
        Browse("http://localhost:8085");
    }

}

这是我的控制器：

@RestController
@RequestMapping("user")
public class UserController extends BaseController {

@Autowired
UserRepository userRepository;

@RequestMapping(value = "/login", method = RequestMethod.POST)
public ModelAndView login(@ModelAttribute User user) {
    User byUsernameOrEmail = 
    userRepository.findUserByUsernameOrEmail(user.getUsername(), 
    user.getUsername());

    ModelAndView mv = new ModelAndView();
    mv.addObject("user", user);
    if (CommonUtils.isEmpty(byUsernameOrEmail)) {
        mv.addObject("message", ExceptionMsg.LoginNameNotExist.getMsg());
        mv.setViewName("redirect:/");
        return mv;
    } else if (!PasswordUtils.getMD5(user.getPassword() + 
            byUsernameOrEmail.getSalt())
            .equals(byUsernameOrEmail.getPassword())) {
     mv.addObject("message",ExceptionMsg.LoginNameOrPassWordError.getMsg());
        mv.setViewName("redirect:/");
        return mv;
    }

    mv.setViewName("pages/admin3/login_soft");

    return mv;
}

这是我的html：

 <form class="login-form"  th:action="@{/user/login}" th:object="${user}"  method="post" >

                <h3 class="form-title">登录</h3>
                <div class="alert alert-danger"  th:if="${#httpServletRequest.getParameter('message')}">
                    <button class="close" data-close="alert"></button>
                    <span th:text="${#httpServletRequest.getParameter('message')}"></span>
                </div>
                <div class="form-group">
                    <!--ie8, ie9 does not support html5 placeholder, so we just show field title for that request.getCookies()-->
                    <label class="control-label visible-ie8 visible-ie9">Username</label>
                    <div class="input-icon">
                        <i class="fa fa-user"></i>
                        <input class="form-control placeholder-no-fix" type="text" autocomplete="off" placeholder="用户名|邮箱"
                               name="username"  th:value="${user.username}"  />
                    </div>
                </div>
                <div class="form-group">
                    <label class="control-label visible-ie8 visible-ie9">Password</label>
                    <div class="input-icon">
                        <i class="fa fa-lock"></i>
                        <input class="form-control placeholder-no-fix" type="password" autocomplete="off" placeholder="密码" name="password"/>
                    </div>
                </div>
                <div class="form-actions">
                    <label class="checkbox">
                    <input type="checkbox" name="remember" value="1"/> 记住密码 </label>
                    <button type="submit" class="btn blue pull-right">
                    登录 <i class="m-icon-swapright m-icon-white"></i>
                    </button>
                </div>

        </form>

我搜索了许多其他问题，他们建议将[用户]放入模型，我是如何做到的，为什么它仍然显示此错误

您在th:object

th:object=“${user}”

尝试使用其他方法重命名用户对象，并确保传递给模型的对象已正确填充

类似于

mv.addObject（“userDetails”，user）然后在html中：

<input class="form-control placeholder-no-fix" type="text" autocomplete="off" placeholder="用户名|邮箱" name="username" th:value="${userDetails.username}"/>


您还在th:object
th:object=“${user}”中使用user

尝试使用其他方法重命名用户对象，并确保传递给模型的对象已正确填充

类似于
mv.addObject（“userDetails”，user）然后在html中：

<input class="form-control placeholder-no-fix" type="text" autocomplete="off" placeholder="用户名|邮箱" name="username" th:value="${userDetails.username}"/>