Custom validation messages are not localized but i18n property key is rendered instead

[ottlinger]

My app performs manual validations of a given form after submit in the controller:

    @PostMapping("/register")
    public ModelAndView processRegisterForm(@Valid @ModelAttribute("register") final RegistrationForm form, final BindingResult result, final RedirectAttributes redirectAttributes) {

           result.addError(new FieldError("register", "captcha", "wrongcaptcha"));
           return new ModelAndView("selfservice.html");
        }

However when rendering the errors within the target template

 <span
                    class="text-danger" th:errors="*{captcha}"
                    th:if="${#fields.hasErrors('captcha')}"></span>

the app shows the message key "wrongcaptcha" instead of the defined i18n.properties element. Other parts of the page are properly localized so it's not a problem of the i18n mechanismus within SpringBoot 3.4.1.

After reading about SpringBoot's message localization I tried multiple combinations of property keys for i18n with no success, e.g.

• register.captcha
• register.captcha.wrongcaptcha
• wrongcaptcha
• captcha.wrongcaptcha

Is there different way to transport validation error i18n keys? I even tried curly braces "{wrongcaptcha}"?

Is this a bug or am I using Thymeleaf in the wrong way?

Thanks for any hint

[ottlinger]

I've provided an example project that shows the problematic behaviour:
https://github.com/ottlinger/custom-validation-messages-1029

I18n is working fine and the language can be changed via the URL param ?lang.
Further actions are described in the app's README.

Default hibernate validation errors are properly translated, but customized messages are not.

Hope this is useful to debug the problem :)

[ottlinger]

Same behaviour with more modern Spring Boot versions, such as 4.0.0-RC2 - the i18n key is shown instead of the translated message during form validation.

[danielfernandez]

You are using the wrong constructor of FieldError here. The constructor you are using is defined as:

public FieldError(String objectName, String field, String defaultMessage)

So your "wrongcaptcha" is being set as the default message, which is precisely the exact text to be shown if there is no internationalized message associated to the code (which, in this case, is no code, because that needs a different constructor of FieldError).

The other constructor looks like:

public FieldError(String objectName, String field, @Nullable Object rejectedValue, boolean bindingFailure,
			@Nullable String[] codes, @Nullable Object[] arguments, @Nullable String defaultMessage)

...and there you can specify the codes array which establishes the keys to be used to resolve i18n messages.

[ottlinger]

@danielfernandez thanks for providing the hint! Would you mind augmenting the javadoc of FieldError make clearer, that

• code - relates to i18n keys that are resolved, while
• defaultMessage is a static message.

Hopefully this will prevent other people from running into the same issue.

Thanks a lot for helping out and solving my issue!

[danielfernandez]

FieldError is a Spring class, not Thymeleaf's.

[ottlinger]

@danielfernandez thanks, filed it as spring-projects/spring-framework#36559