Should embeddable jpa class implement equals and hashCode?

Question

Let's say I have the following scenario:

@Entity
public class Person {
    @Id
    private Long id; //Surrogate key

    @Embedded
    private Name name; //Natural key

    public int hashCode() {
        ... //based on natural key Name
    }
    public boolean equals(Object obj) {
        ... //based on natural key Name
    }
}

@Embeddable
public class Name {
    private String firstName;
    private String middleName;
    private String lastName;

    //Should I implement equals/hashCode baseed on the three fields?
}

Should Name class implement equals and hashCode on Name class in order that Person equals work properly?.

For an Embeddable object that will be used as an EmbeddedId is a must. But in this example I'm using surrogate key.

are you sure "name" is going to be truly unique? Not hard to imagine a situation where two people have the same name. — matt b, Jan 21 '11 at 18:54
Just a note... Your *Person* class ain't *final*. You should realize that if you extend *Person* your *equals* is broken because, as Joshua Bloch puts it in *"Effective Java"* : **there is simply no way to extend an instantiable class while preserving the equals contract**. I don't know when *"Effective Java"* came out (2001?), but I'm sure one day people will admit that having *equals()* and *hashCode()* at the top of the Java OO-hierarchy was one of Gosling's biggest brain fart ;) [that OO problem was known before that but *Effective Java* tends to be authoritative] — SyntaxT3rr0r, Jan 21 '11 at 19:44

score 6 · Accepted Answer · answered Jan 21 '11 at 18:49

6

I don't believe JPA ever requires you to implement equals and hashcode. Hibernate used to, but a recent review of the docs shows that this is no longer a requirement.

But of course it's always a good idea to implement hashcode and equals.

answered Jan 21 '11 at 18:49

Karthik Ramachandran

11,925
10
45
53

Should embeddable jpa class implement equals and hashCode?

1 Answers1

Linked