Lombok: Problem with hashCode() on null attribute when used on hash based structure

The @EqualsAndHashCode annotation that use Long attribute such as pk can cause some unspected behavor when use with hash based structure (like HashSet).

eg.:

@Entity
@EqualsAndHashCode(of = "pk")
class Foo {

    @Id
    private Long pk;

    private LocalDate createdAt;

}

@Entity
class Foo {

    @Id
    private Long pk;

    private LocalDate createdAt;

    public int hashCode() {
        int PRIME = true;
        int result = 1;
        Object $pk = this.getPk();
        int result = result * 59 + ($pk == null ? 43 : $pk.hashCode());
        return result;
    }

    public String toString() {
        return getClass().getName() + "@" + Integer.toHexString(hashCode());
    }
}

So when the instance with pk = null and other with pk = 43, it will return the same hash code and it may be considered as same on hash based structure, wich they aren't.

And in the case to use OmniFaces ListConverter that use toString we have the same problem.

Maybe return a hashcode of the object instance rather than an hardcoded constant

Did you already take this scenario, or do you know some way to workaround this situation?!

Version info

• Lombok => 1.18.8
• Platform => Windows 10 JDK 11.0.4 IntelliJ