How do I map a set of string objects using JPA Annotations?

Question

@Entity
public class TestClass implements Serializable{
    private Integer id;
    private Set<String> mySet;

    @Id
    @GeneratedValue
    public Integer getId() {
        return id;
    }
    @OneToMany(cascade={CascadeType.ALL})
    public Set<String> getMySet() {
        return mySet;
    }
}

I get the following error.

Caused by: org.hibernate.AnnotationException: Use of @OneToMany or @ManyToMany targeting an unmapped class: TestClass.mySet[java.lang.String]

or if I leave off the @OneToMany

org.hibernate.MappingException: Could not determine type for: java.util.Set, at table: test_class, for columns: [org.hibernate.mapping.Column(my_sets)]

Hibernate's @CollectionOfElements annotation solved the problem for me. It's hibernate specific, but I don't plan on swapping out my JPA implementation. — ScArcher2
– ScArcher2, Commented May 28, 2009 at 18:46

Community · Accepted Answer · 2017-05-23 12:32:02Z

8

You'll find a pretty decent answer here. The rules for Lists apply to Sets too.

edited May 23, 2017 at 12:32

CommunityBot

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answered May 28, 2009 at 15:43

Cogsy

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Comments

Martin Schröder · Accepted Answer · 2018-02-01 14:42:09Z

6

Ooh oh, I had to do this one.

@CollectionOfElements(targetElement = String.class)

edited Feb 1, 2018 at 14:42

Martin Schröder

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answered May 30, 2009 at 0:01

Joshua

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2 Comments

ScArcher2 Over a year ago

This is also what I had to do, but it is hibernate specific. In my situation that's fine with me.

pdem Over a year ago

@ElementCollection in JPA2, this answer is the better approach. see stackoverflow.com/questions/287201/…

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