How can I use generated value within composite keys?
The documentation is a bit confusing on this topic...
To my knowledge, composite keys always had to be assigned by the application (i.e. non generated) at least with standard JPA but also Hibernate Core:
8.4. Components as composite identifiers
...
You cannot use an IdentifierGenerator to generate composite keys. Instead the application must assign its own identifiers.
But things might be a bit different in practice (see HHH-2060 and/or this thread for an alternative using a CompositeUserType together with an IdentifierGenerator).
Now, the most confusing part, from the Hibernate Annotations 3.5 documentation:
2.2.3.2.4. Partial identifier generation
Hibernate supports the automatic generation of some of the identifier properties. Simply use the
@GeneratedValue
annotation on one or several id properties....
You can also generate properties inside an
@EmbeddedId
class.
(and please also read the warning from the Hibernate Team against using this feature).
I don't have any practical experience with it though.
References
- Hibernate Core Reference Guide
- Hibernate Annotations 3.5 Reference Guide
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Updated on June 06, 2022Comments
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Admin almost 2 years
I have two classes documentlog and documentversion(with primary keys: int doc_id and int docVersionID) with a many-to-one relationship. I used a composite key class called CompundKey to manage the compound primary key. I need to auto increment docversionID but I am not able to do that. Could you please help me in this regard?
@Entity @Table(name = "Documentversion", schema = "DocumentManagement") public class DocumentVersion implements Serializable { private CompoundKey id; private List<DocumentLog> documentLog; @OneToMany(mappedBy="documentVersion", targetEntity=DocumentLog.class, cascade ={CascadeType.PERSIST, CascadeType.MERGE, CascadeType.REFRESH}) public List<DocumentLog> getDocumentLog() { return documentLog; } public void setDocumentLog(List<DocumentLog> documentLog) { this.documentLog = documentLog; } @EmbeddedId @AttributeOverride(name="doc_Id", column=@Column(name="doc_Id") ) public CompoundKey getId() { return id; } public void setId(CompoundKey id) { this.id = id; } }