表单验证错误消息不显示spring mvc thymeleaf

Question

I have add user form doesn't display the error message with thymeleaf. I try to read other solutions and apply other solutions in this forum but still doesn't work.

**userform.html** 

 <form  id="adduser" role="form"  th:action="@{/adduser}" method="post" th:object="${user}">


    <div class="form-group">
                                        <label>First Name</label>
                                        <input class="form-control" th:field="*{first_name}"/>

                                          <p th:if="${#fields.hasErrors('first_name')}" th:errors="${user.first_name}">First name is mandatory</p>
                                    </div>
<button type="submit" name="action" value="adduser" class="btn btn-default" onclick="myFunction()">Submit</button>

  </form>

My spring MVC controller

UserformController.java

// Returns the view with model attached 
     @RequestMapping(value = "/userform", method = RequestMethod.GET) 
     public ModelAndView showuser(HttpServletRequest request, HttpServletResponse response) { 
        LOGGER.info("in get adduser"); 

        ModelAndView mav = new ModelAndView(); 

        mav.setViewName("userform"); 
        mav.addObject("user", new User()); 

        return mav; 

    } 

//Save 

    @RequestMapping(value = "/adduser", method = RequestMethod.POST) 
    public ModelAndView adduser(@Valid @ModelAttribute("userForm")  Userform user, BindingResult result, @RequestParam(value="action", required=true) String action) { 


        ModelAndView mav = new ModelAndView(); 

        if (result.hasErrors()) { 

            mav.setViewName("redirect:userform"); 
            mav.addObject("user", user); 
            return mav; 
        } 
else { 
            utilService.insert(user); 

            mav.setViewName("redirect:userlist"); 

            return mav; 
        } 

    } 

Answer 1

Did you define any constraints in the User class? Please show the User class.

The errors would be based on the constraints in the properties of the User class, so there should be something like this

public class User {

    @NotNull
    private String first_name;

}