Should I write equals() and hashCode() methods in JPA entities?

Question

I want to check if entity is in a Collection member (@OneToMany or @ManyToMany) of another entity:

if (entity2.getEntities1().conta         


        

Answer 1

We tend to let IDE generate hashCode() and equals() for us. Be careful though. When you generate those methods for JPA Entities. Some versions of equals() checks for class identity

// ... inside equals() - wrong approach for Entities (cause of generate proxies)
if (o == null || this.getClass() != o.getClass()) {
        return false;
}
// ...

This would break your collections with some JPA libraries as those libraries create proxies to your entities (subclasses), like for example MyGreatEntity_$$_javassist_7 in Hibernate.

In Entities always allow subclasses in equals().