Validation of Optional

Question

Consider this code

import org.hibernate.validator.constraints.Range;
import javax.validation.ConstraintViolation;
import javax.validation.Validation;
import javax.validation.Validator;
import javax.validation.constraints.NotBlank;
import javax.validation.constraints.NotNull;
import java.util.List;
import java.util.Optional;
import java.util.Set;

class Scratch {
    public static void main(String[] args) {
        final Person alice = new Person("Alice", 54, Optional.of("Tiddles"));// Valid has pet with valid name
        final Person frank = new Person("Frank", 75, Optional.of("  ")); // Should be invalid pet name is blank
        final Person oliver = new Person("Oliver", 75, null); // Should be invalid pet name is null
        final Person bob = new Person("Bob", 33, Optional.empty()); // Valid no pet

        final List<Person> people = List.of(alice, frank, oliver, bob);

        final Validator validator = Validation.buildDefaultValidatorFactory().getValidator();

        for (Person person : people) {
            final Set<ConstraintViolation<Person>> violations = validator.validate(person);
            if (violations.isEmpty()) {
                System.out.println(String.format( "[%s] is valid", person.name));
            } else {
                System.out.println(String.format("[%s] is invalid [%s]", person.name, violations));
            }

        }
    }

    static class Person {
        @NotBlank
        public String name;
        @Range(min = 0, max = 150)
        public int age;
        @NotNull
        public Optional<@NotBlank String> petsName;

        public Person(String name, int age, Optional<String> petsName) {
            this.name = name;
            this.age = age;
            this.petsName = petsName;
        }
    }
}

The question is how to validate Optional fields. Its valid for petsName to be an empty Optional (i.e. no pet) but if there is a pet it should have a valid (i.e. non-blank) name. When I run this code it outputs

Dec 22, 2021 11:50:25 AM org.hibernate.validator.internal.util.Version <clinit>
INFO: HV000001: Hibernate Validator 6.1.7.Final
[Alice] is valid
[Frank] is invalid [[ConstraintViolationImpl{interpolatedMessage='must not be blank', propertyPath=petsName, rootBeanClass=class Scratch$Person, messageTemplate='{javax.validation.constraints.NotBlank.message}'}]]
[Oliver] is invalid [[ConstraintViolationImpl{interpolatedMessage='must not be null', propertyPath=petsName, rootBeanClass=class Scratch$Person, messageTemplate='{javax.validation.constraints.NotNull.message}'}]]
[Bob] is invalid [[ConstraintViolationImpl{interpolatedMessage='must not be blank', propertyPath=petsName, rootBeanClass=class Scratch$Person, messageTemplate='{javax.validation.constraints.NotBlank.message}'}]

So its close to working. Only the last case of bob is wrong. Is there any obvious solution i'm missing?