Using Composite Id in Hibernate 4.2.1.Final

Using composite Id with auto-generated values

If you are planning to use an entity with composite Id in Hibernate as shown in Listing 1, then you cannot auto-generate values of @Id using @GeneratedValue(strategy=GenerationType.IDENTITY).

If you attempt to do so then you’ll get the following exception:
java.lang.IllegalArgumentException: Can not set java.lang.Long field somepackage.StatementId.sequence to org.hibernate.id.IdentifierGeneratorHelper$2

This is a bug in Hibernate HHH-064 which also exists in version 4.2.1.Final

The work around is to explicitly generate @Id value within your Java code instead of using auto-generated value.

@Entity
@IdClass(StatementId.class)
public class Statement {
    @Id
    @ManyToOne
    private Document document;

    @Id
    private Long sequence;

    ...
}

Listing 1. An entity with composite Id

Using @EmbeddedId

Using @EmbeddedId as shown in Listing 2 does not work in Hibernate 4.2.1 though it works in Hibernate 3.5.x.

It gives the following exception in Hibernate 4.2.1.Final:
org.hibernate.annotations.common.AssertionFailure: Declaring class is not found in the inheritance state hierarchy: somepackage.StatementId

The workaround for this is to use @IdClass instead of @EmbeddedId.

@Embeddable
public class StatementId implements Serializable {
    @Id
    @ManyToOne
    private Document document;

    @Id
    private Long sequence;

    /* getters and setters */
}

@Entity
public class Statement {
    @EmbeddedId
    private StatementId id;

    ...
}

Listing 2. Using @EmbeddedId in entity