Constraints validation in a postconstruct method

Question

Hello I have the next piece of code:

@Setter
@Getter
@Builder
public class User {
  
  @Pattern(regexp = "[a-zA-Z]*")
  private String username;

  public User(String username){
    this.username = username;
    ValidatorFactory factory = Validation.buildDefaultValidatorFactory();
    Set<ConstraintValidation<User>> violations = factory.getValidator().validate(this);
    if(!violations.isEmpty) throw new ConstraintViolationExcetion(violations);
}

It is working, and when I try to create an User it always check the constraints (also with builder pattern), but i would like to avoid to generate the constructor and use the lombok anotation @AllArgsConstructor and use the PostConstruct from javax to validate.

@Setter
@Getter
@AllArgsConstructor
@Builder
public class User {
  
  @Pattern(regexp = "[a-zA-Z]*")
  private String username;

  @PostConstruct
  public void valid() {
    ValidatorFactory factory = Validation.buildDefaultValidatorFactory();
    Set<ConstraintValidation<User>> violations = factory.getValidator().validate(this);
    if(!violations.isEmpty) throw new ConstraintViolationExcetion(violations);
}

I'm using JAVA11 including javax.annotation dependency. User is a regular object, not a bean of spring. But this way is not working... How can I make it work? Thanks.

Is `User` an EJB / Spring bean or a regular object? – João Dias Dec 01 '21 at 17:20 — João Dias, Dec 01 '21 at 17:20
Its a regular object – rubengonzalez96 Dec 02 '21 at 08:24 — rubengonzalez96, Dec 02 '21 at 08:24

Fastaca Girasol · Answer 1 · 2021-12-01T17:21:53.317

1

if you are using a java version of 9 or above @PostConstruct is deprecated, so you might need to add a dependency manually. could you add which java version are you using?

another reason why it is not working is because you did not apply @Component annotation and @PostConstruct only works with beans managed by spring container.

ref: Why is PostConstruct not called?

I would recommend you to look at BeanPostProccessor for AOP since it is more flexible and will allow you to do validations on your bean. this is also pure aop.

edited Dec 01 '21 at 17:21

answered Dec 01 '21 at 17:13

Fastaca Girasol

70
6

Added! Thanks. But i wold not like to include the `@Component` annotation because I think it is not the same as a controller or a service. May I be wrong? – rubengonzalez96 Dec 02 '21 at 08:26
`@Service`, `@Rpository`, `@Controller` are a `@Component` but just look at them as different roles. or as children of `@Component`, however, without one of those annotations `@PostConstruct` won't be able to work since no framework responds and manages them. so you must use it under a POJO with a `@Component` annotation. otherwise its ignored. – Fastaca Girasol Dec 02 '21 at 11:44

score 0 · Accepted Answer · answered Apr 01 '22 at 11:18

Finally I found the behavour I was looking for.

@Setter
@Getter
public class User {
  
  @Pattern(regexp = "[a-zA-Z]*")
  private String username;

  @Builder
  public User(String username){
    this.username = username;
    ValidatorFactory factory = Validation.buildDefaultValidatorFactory();
    Set<ConstraintValidation<User>> violations = factory.getValidator().validate(this);
    if(!violations.isEmpty) throw new ConstraintViolationExcetion(violations);
}

Furthermore, I would implement a self validable class to be reusable.

public abstract class SelfValidating < T > {
    private Validator validator;
    public SelfValidating() {
        ValidatorFactory factory = Validation.buildDefaultValidatorFactory();
        validator = factory.getValidator();
    }
    protected void validateSelf() {
        Set < ConstraintViolation < T >> violations = validator.validate((T) this);
        if (!violations.isEmpty()) {
            throw new ConstraintViolationException(violations);
        }
    }
}

And then, my User class just would:

@Setter
@Getter
public class User extends SelfValidating<User> {
  
  @Pattern(regexp = "[a-zA-Z]*")
  private String username;

  @Builder
  public User(String username){
    this.username = username;
    this.validateSelf();
}

This idea is taken from Get Your Hands Dirty on Clean Architecture

Constraints validation in a postconstruct method

2 Answers2