如何在 Thymeleaf 中显示错误

Question

我使用

ConstraintValidator

实现了自定义密码验证，并且我需要在验证失败时显示错误消息。但验证失败时不会显示错误消息。

界面：

@Target({FIELD})
@Retention(RUNTIME)
@Constraint(validatedBy = {PasswordConstraintValidator.class})
@Documented
public @interface Password {
    String message() default "{messages.validation.password}";

    int maxLength() default 100;

    int minLength() default 8;

    int upperCaseCount() default 2;

    int lowerCaseCount() default 2;

    int specialCharCount() default 1;

    Class<?>[] groups() default {};

    Class<? extends Payload>[] payload() default {};

实施

@Component
public class PasswordConstraintValidator implements ConstraintValidator<Password, String> {

    private int minLength;

    private int maxLength;

    private int upperCaseCount;

    private int lowerCaseCount;

    private int specialCharCount;

    @Override
    public void initialize(final Password password) {
        minLength = password.minLength();
        maxLength = password.maxLength();
        upperCaseCount = password.upperCaseCount();
        lowerCaseCount = password.lowerCaseCount();
        specialCharCount = password.specialCharCount();
    }

    @Override
    public boolean isValid(final String string, final ConstraintValidatorContext constraintValidatorContext) {
        return validatePassword(string);
    }

// method validatePassword(string){}

我的注册表如下所示：

<form xmlns:th="http://www.thymeleaf.org" th:action="@{/register/user}" method="post"
      th:object="${userDto}" style="width: 22rem;" th:fragment="reg-user-form">

<!-- Password -->
    <div class="form-outline mb-4">
        <label class="form-label text-white h5" for="password" th:text="#{label.password}">Password</label>
        <input type="password" id="password" th:field="*{password}" class="form-control bg-dark text-white rounded border-2" style="border-color: #2f3944;" required />
        <div class="text-danger" th:if="${#fields.hasErrors('password')}" th:errors="*{password}"></div>
    </div>

</form>

控制器方法如下所示：

 @GetMapping(USER_REGISTER_URL)
 public String regUser(final Model model) {
    model.addAttribute("userDto", new RequestUserDto());
    return USER_REGISTER_PAGE;
 }


@PostMapping(USER_REGISTER_URL)
public String regUser(@Valid @ModelAttribute final RequestUserDto userDto,
                          final BindingResult bindingResult, final Model model) {

     if (bindingResult.hasErrors()) {
         model.addAttribute("userDto", userDto);
         model.addAttribute("errors", bindingResult.getAllErrors());
         return USER_REGISTER_PAGE;
     }

      userService.createUser(userDto);
      return LOGIN_PAGE_REDIRECT;
}

我通过用

bindingResult

 打印出来来检查 

System.out.println

中是否有错误

Field error in object 'requestUserDto' on field 'password': rejected value [awdsaw]; codes [Password.requestUserDto.password,Password.password,Password.java.lang.String,Password]; arguments [org.springframework.context.support.DefaultMessageSourceResolvable: codes [requestUserDto.password,password]; arguments []; default message [password],2,100,8,1,2]; default message [The Password is incorrect. Max length of password - 100, min length of password 8, must contain: upper case—at least 2, lower case - at least 2, special char - 1]

但是，Thymeleaf 不会显示错误消息，这种情况不仅会发生在自定义验证中，还会发生在像

@Size:

这样的注释中

Field error in object 'requestUserDto' on field 'firstName': rejected value [a]; codes [Size.requestUserDto.firstName,Size.firstName,Size.java.lang.String,Size]; arguments [org.springframework.context.support.DefaultMessageSourceResolvable: codes [requestUserDto.firstName,firstName]; arguments []; default message [firstName],50,10]; default message [size must be between 10 and 50]

Answer 1

尝试更新到此：

<div class="text-danger" th:text="${errors}"></div>