Spring Boot - Hibernate custom constraint doesn't inject Service

Question

I will try to ignore other details and make it short:

@Entity
public class User
    @UniqueEmail
    @Column(unique = true)
    private String email;
}

@Component
public class UniqueEmailValidatior implements ConstraintValidator<UniqueEmail,String>, InitializingBean {

    @Autowired private UserService userService;

    @Override
    public void initialize(UniqueEmail constraintAnnotation) {

    }

    @Override
    public boolean isValid(String value, ConstraintValidatorContext context) {
        if(userService == null) throw new IllegalStateException();
        if(value == null) return false;
        return !userService.isEmailExisted(value);
    }

}

This will work when the validation is made in Spring (Spring MVC @Valid or inject the Validator using @Autowire), everything will be fine. But as soon as I save the entity using Spring Data JPA:

User save = userRepository.save(newUser);

Hibernate will try to instantiate a new UniqueEmailValidatior without inject the UserService bean. So how can I make Hibernate to use my UniqueEmailValidatior component without it instantiate a new one. I could disable hibernate validation using spring.jpa.properties.javax.persistence.validation.mode=none but I hope there is another way

Update: Here is my UserService:

   @Autowired private Validator validator;
   @Transactional
    public SimpleUserDTO newUser(UserRegisterDTO user) {
        validator.validate(user);
        System.out.println("This passes");
        User newUser = new User(user.getUsername(),
                passwordEncoder.encode(user.getPassword()),user.getEmail(),
                "USER",
                user.getAvatar());
        User save = userRepository.save(newUser);
        System.out.println("This won't pass");
        return ....
    }

Answer 1

I would expect that Spring Boot would wire the existing validator to the EntityManager apparently it doesn't.

You can use a HibernatePropertiesCustomizer and add properties to the existing EntityManagerFactoryBuilder and register the Validator.

NOTE: I'm assuming here that you are using Spring Boot 2.0

@Component
public class ValidatorAddingCustomizer implements HibernatePropertiesCustomizer {

    private final ObjectProvider<javax.validation.Validator> provider;

    public ValidatorAddingCustomizer(ObjectProvider<javax.validation.Validator> provider) {
        this.provider=provider;
    }

    public void customize(Map<String, Object> hibernateProperties) {
        Validator validator = provider.getIfUnique();
        if (validator != null) {
            hibernateProperties.put("javax.persistence.validation.factory", validator);
        }
    }
}

Something like this should wire the existing validator with hibernate and with that it will make use of auto wiring.

NOTE: You don't need to use @Component on the validator the autowiring is build into the validator factory before returning the instance of the Validator.