Spring Boot Mapping Validation Codes to MessageSource Message

Question

Problem:

I am trying to use as much Spring Boot Auto-configuration as possible to reduce boiler plate code. I cannot get the Spring Validation codes to automatically map to my externalized messages.properties. It will only work if I add my own LocalValidatorFactoryBean and use the fully qualified javax constraint message.

Goal

I want to override the defaultMessage for @javax.validation.constraints.NotNull globally in my application based on Spring Validation codes.

The first thing I did was register this bean...do I really have to? I see Spring Boot has one but it doesn't seem to correlate to messages.properties.

@Bean
public LocalValidatorFactoryBean validator(MessageSource messageSource) {
  LocalValidatorFactoryBean bean = new LocalValidatorFactoryBean();
  bean.setValidationMessageSource(messageSource);
  return bean;
}

The next one is surprising to me. Spring Validation has this nifty DefaultMessageCodesResolver that provides excellent code strategy for failures that look something like this:

"code": "NotNull",
"codes": [
   "NotNull.user.firstName",
   "NotNull.firstName",
   "NotNull.java.lang.String",
   "NotNull"
],

But these codes aren't even considered for the @NotNull constraint. The spring documentation for Validation Conversion hints that something like this does exist but falls short of anything useful yet.

I wrote a sample application here and you can see that it's not working.

Question

How can I override the default message of Spring Validation errors based on those codes from messages.properties?

Relevant build.gradle

• springBootVersion = '2.0.0.RELEASE'
• compile('org.springframework.boot:spring-boot-starter-web')

src/main/resources/messages.properties:

NotNull.user.firstName=This doesn't work
NotNull.firstName=Or this
NotNull.java.lang.String=This doesn't work either
NotNull=And this doesn't work

javax.validation.constraints.NotNull.message=THIS DOES WORK! But why have codes then?

Spring Auto-Configuration Output proving the auto-config loaded.

   MessageSourceAutoConfiguration matched:
      - ResourceBundle found bundle URL [file:/home/szgaljic/git/jg-github/journey-through-spring/basic-web-validations/build/resources/main/messages.properties] (MessageSourceAutoConfiguration.ResourceBundleCondition)
      - @ConditionalOnMissingBean (types: org.springframework.context.MessageSource; SearchStrategy: current) did not find any beans (OnBeanCondition)

Some other relevant start-up logs:

2018-03-26 14:32:22.970 TRACE 1093 --- [           main] o.s.beans.CachedIntrospectionResults     : Found bean property 'validationMessageSource' of type [org.springframework.context.MessageSource]

Validation Constraint:

public class User {
    @NotNull
    private String username;

    @NotNull
    private String firstName;
}

Controller just for Testing:

@RestController
public class UserController {

    @PostMapping("/users")
    public List<ObjectError> testValidation(@Valid @RequestBody User user){
       return null; // null implies no failed validations.. just for testing
    }

}

Failed to use the codes

I tried to comment/uncomment the messages in messages.properties but it will only take the value of javax.validation.constraints.NotNull.message.

Answer 1

Because of the configuration

@Bean
public LocalValidatorFactoryBean validator(MessageSource messageSource) {
    LocalValidatorFactoryBean bean = new LocalValidatorFactoryBean();
    bean.setValidationMessageSource(messageSource);
    return bean;
}

So you're using Bean Validation then spring get the messages from message.properties file that override from org.hibernate.validator.ValidationMessages.properties file using the key javax.validation.constraints.NotNull.message. If you would like to have key-value pairs:

NotNull.user.firstName=This doesn't work
NotNull.firstName=Or this
NotNull.java.lang.String=This doesn't work either
NotNull=And this doesn't work

to work you have to write as follows:

@Autowired
private MessageSource messageSource;

@PostMapping("/users")
public List<ObjectError> testValidation(@Valid @RequestBody User user, BindingResult bindingResult){
   bindingResult.getFieldErrors().forEach(fieldError -> new ObjectError(
   /*Assumes that ObjectError has constructor of ObjectError(String message) */
          messageSource.getMessage(fieldError, Locale.getDefault())
   ));
   return null; 
}