Bug in Idea suggestion for JPA efficient hashCode?

Question

When you annotate some JPA Entity with Lombok:

@Entity
@EqualsAndHashCode
public class Person {

IntelliJ Idea will show a suggestion that it is not optimal:

Using @EqualsAndHashCode for JPA entities is not recommended. It can cause severe performance and memory consumption issues.

And it generates the following code:

@Override
public final boolean equals(Object object) {
    if (this == object) return true;
    if (object == null) return false;
    Class<?> oEffectiveClass = object instanceof HibernateProxy ? ((HibernateProxy) object).getHibernateLazyInitializer().getPersistentClass() : object.getClass();
    Class<?> thisEffectiveClass = this instanceof HibernateProxy ? ((HibernateProxy) this).getHibernateLazyInitializer().getPersistentClass() : this.getClass();
    if (thisEffectiveClass != oEffectiveClass) return false;
    ConfigAudit that = (ConfigAudit) object;
    return getId() != null && Objects.equals(getId(), that.getId());
}

@Override
public final int hashCode() {
    return this instanceof HibernateProxy ? ((HibernateProxy) this).getHibernateLazyInitializer().getPersistentClass().hashCode() : getClass().hashCode();
}

I just noticed that the hashCode() is actually called on the class and not on the object. Is this bug?

Javadoc:

If two objects are equal according to the equals method, then calling the hashCode method on each of the two objects must produce the same integer result.

Answer 1

Yes, this was made intentionally - with this hashCode() implementation entities are grouped by classes and then can be compared by equals(). More details in this article https://jpa-buddy.com/blog/hopefully-the-final-article-about-equals-and-hashcode-for-jpa-entities-with-db-generated-ids/