Spring Boot custom constraint validation component

Question

config class

@ComponentScan(basePackages = {"validator"})
class AppConfiguration { ... }

annotation class

@Target({ElementType.METHOD, ElementType.FIELD})
@Retention(RetentionPolicy.RUNTIME)
@Constraint(validatedBy = UniqueLoginValidator.class)
public @interface UniqueLogin {
    String message() default "{com.dolszewski.blog.UniqueLogin.message}";
    Class<?>[] groups() default {};
    Class<? extends Payload>[] payload() default {};
}

validator class

@Component
class UniqueLoginValidator implements ConstraintValidator<UniqueLogin, String> {

    private UserRepository userRepository;

    public UniqueLoginValidator(UserRepository userRepository) {
        this.userRepository = userRepository;
    }

    public void initialize(UniqueLogin constraint) {
    }

    public boolean isValid(String login, ConstraintValidatorContext context) {
        return login != null && !userRepository.findByLogin(login).isPresent();
    }

}

I have a class with property @UniqueLogin String login, I also use other annotations like @Size and @Max, the last 2 works, but my custom annotation does not work.

Can you please help to understand why spring do not call custom validator?

check A Spring Custom Annotation for a Better DAO article. You need to define a BeanPostProcessor for spring to know about the annotation — user10386912
– user10386912, Commented Dec 13, 2018 at 14:58

Roberto Canini · Accepted Answer · 2018-12-13 15:25:53Z

2

It worked for me to create inside src/main/resources/META-INF/services a file named javax.validation.ConstraintValidator with a list new line separated of all qualified name of custom constraint validators you created.

This way, Spring will automatically register the custom validator.

This file will be automatically checked from Spring and included into built artifact.

Be careful of annotation configuration after applying this solution. You should annotate with @Constraint(validatedBy = { }) to prevent double validator initialization.

answered Dec 13, 2018 at 15:25

Roberto Canini

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2 Comments

Roberto Canini Over a year ago

This make sense because javax Validation is not a Spring native function, but it is well integrated with the framework

jahoza Over a year ago

it is not native, but the object is created by spring

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