Multi-Column Join in Hibernate/JPA Annotations

Posted by bowsie on Stack Overflow See other posts from Stack Overflow or by bowsie
Published on 2012-06-01T07:03:55Z Indexed on 2012/06/06 22:40 UTC
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I have two entities which I would like to join through multiple columns. These columns are shared by an @Embeddable object that is shared by both entities. In the example below, Foo can have only one Bar but Bar can have multiple Foos (where AnEmbeddableObject is a unique key for Bar). Here is an example:

@Entity
@Table(name = "foo")
public class Foo {
    @Id
    @Column(name = "id")
    @GeneratedValue(generator = "seqGen")
    @SequenceGenerator(name = "seqGen", sequenceName = "FOO_ID_SEQ", allocationSize = 1)
    private Long id;
    @Embedded
    private AnEmbeddableObject anEmbeddableObject;
    @ManyToOne(targetEntity = Bar.class, fetch = FetchType.LAZY)
    @JoinColumns( {
        @JoinColumn(name = "column_1", referencedColumnName = "column_1"),
        @JoinColumn(name = "column_2", referencedColumnName = "column_2"),
        @JoinColumn(name = "column_3", referencedColumnName = "column_3"),
        @JoinColumn(name = "column_4", referencedColumnName = "column_4")
})
    private Bar bar;

    // ... rest of class
}

And the Bar class:

@Entity
@Table(name = "bar")
public class Bar {
    @Id
    @Column(name = "id")
    @GeneratedValue(generator = "seqGen")
    @SequenceGenerator(name = "seqGen", sequenceName = "BAR_ID_SEQ", allocationSize = 1)
    private Long id;
    @Embedded
    private AnEmbeddableObject anEmbeddableObject;

    // ... rest of class
}

Finally the AnEmbeddedObject class:

@Embeddable
public class AnEmbeddedObject {
    @Column(name = "column_1")
    private Long column1;
    @Column(name = "column_2")
    private Long column2;
    @Column(name = "column_3")
    private Long column3;
    @Column(name = "column_4")
    private Long column4;

    // ... rest of class
}

Obviously the schema is poorly normalised, it is a restriction that AnEmbeddedObject's fields are repeated in each table.

The problem I have is that I receive this error when I try to start up Hibernate:

org.hibernate.AnnotationException: referencedColumnNames(column_1, column_2, column_3, column_4) of Foo.bar referencing Bar not mapped to a single property

I have tried marking the JoinColumns are not insertable and updatable, but with no luck. Is there a way to express this with Hibernate/JPA annotations?

Thank you.

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