Custom class level bean validation constraint

Question

I already know how to add annotation based validation on specific attributes in Entity class like :-

public class Person {

    @NotNull
    private String firstName;

    private String lastName;

    //...
}

But is it possible to add annotation on class Person, in order to validate all the attributes inside this class, by creating a Customised Validation Class and handling validation there somewhere like :-

@Retention(value = RetentionPolicy.RUNTIME)      
@Target(value = ElementType.METHOD)
public @interface PersonneName {
public String firstName();
}

I am working on a project to get Constraints from Database and creating Customised Validation Class and applying on the Entity class attributes according to the constaints got from DB. Please suggest.

Answer 1

Yes, of course, it's possible. First, create the definition of your annotation. Pretty much like you did in your example, however, with a different @Target type

@Target({ElementType.TYPE, ElementType.ANNOTATION_TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Constraint(validatedBy = PersonValidator.class)    
public @interface ValidPerson {
    String message () default "Your custom message";
    Class<?>[] groups () default {};
    Class<? extends Payload>[] payload () default {};
}

Then implement the validator whose isValid method takes the instance of your Person class:

 public class PersonValidator implements ConstraintValidator<ValidPerson, Person> {
  
    @Override
    public boolean isValid (Person person, ConstraintValidatorContext context) {
        // your validation logic
    }
}