Java hibernate-validator @interface load from properties

Question

I saw following hibernate validator code

package org.hibernate.validator.constraints;
...
public @interface CreditCardNumber {
   String message() default "{org.hibernate.validator.constraints.CreditCardNumber.message}";
...
}

and in the properties files has key value the credit card error message like

org.hibernate.validator.constraints.CreditCardNumber.message        = invalid credit card number

how do hibernate validator do such things
i mean load properties on @interface?

Answer 1

Doc: https://docs.spring.io/spring-boot/docs/current/reference/htmlsingle/#features.developing-auto-configuration

#1. create the autoconfig class

@AutoConfiguration
public class ObiValidatorAutoConfiguration {

    private MessageSource messageSource() {
        ReloadableResourceBundleMessageSource messageSource = new ReloadableResourceBundleMessageSource();
        messageSource.setBasename("classpath:messages");
        messageSource.setDefaultEncoding("UTF-8");
        return messageSource;
    }

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

#2. Locating Auto-configuration Candidates
create file META-INF/spring/org.springframework.boot.autoconfigure.AutoConfiguration.imports
with content like
package.location.ObiValidatorAutoConfiguration

#3. create the default error message file (for ex: resources/messages.properties)
with content
package.cc.message=contains invalid character

#4. the annotation class

@Pattern(regexp = "[\\.a-zA-Z0-9]*")
@Target({ FIELD, PARAMETER })
@Retention(RUNTIME)
@Constraint(validatedBy = {})
@ReportAsSingleViolation
public @interface CreditCard {
    String message() default "{package.cc.message}";
    Class<?>[] groups() default {};
    Class<? extends Payload>[] payload() default {};
}

#5. use that annotation on spring-boot app, and when value is not valid then the default value (contains invalid character) is show up