JPA: How to fill related entity after the master is inserted - jpa

Question

I have two tables called SL_DOCUMENT and SL_PROPOSE. The SL_DOCUMENT has its own ID (ID_DOCUMENT) and a foreign key to SL_PROPOSE (ID_PROPOSE). The SL_PROPOSE ID column is ID_PROPOSE. The particularity is that SL_PROPOSE ID value is actually the SL_DOCUMENT.ID_DOCUMENT value. i.e., after a new SL_DOCUMENT is inserted, the related SL_PROPOSE should be inserted with the SL_DOCUMENT.ID_DOCUMENT as ID and later the same value should be used in SL_DOCUMENT.ID_PROPOSE column.
I did my JPA mapping as follows:
#Entity
#Table(name = "SL_DOCUMENT")
public class DocumentORM {
#Id
#Column(name = "ID_DOCUMENT")
#SequenceGenerator(name = "SEQ_SL_DOCUMENT", sequenceName = "SEQ_SL_DOCUMENT")
#GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "SEQ_SL_DOCUMENT")
private Long id;
#OneToOne(mappedBy = "document", cascade = { CascadeType.PERSIST })
// #JoinColumn(name = "ID_PROPOSE", updatable = false)
private ProposeORM propose;
// ...
}
#Entity
#Table(name = "SL_PROPOSE")
public class ProposeORM {
#Id
#Column(name = "ID_PROPOSE")
private Long id;
#MapsId
#OneToOne
#JoinColumn(name="ID_PROPOSE")
private DocumentORM document;
// ...
public ProposeORM(DocumentORM document) {
super();
this.document = document;
this.document.setPropositura(this);
}
}
To create the new instances of of DocumentORM and ProposeORM:
DocumentORM document = new DocumentORM();
ProposeORM propose = new ProposeORM(document);
And finally to insert the new Document with ProposeORM:
this.documentoDAO.insert(document);
When I really insert a document, according the snippets above, I see in the console (Websphere 8.5) the INSERT commands for the SL_DOCUMENT, SL_PROPOSE running correctly. However, when I see the tables, the column SL_DOCUMENT.ID_PROPOSE is still NULL. Even If I uncomment the #JoinColumn annotation over DocumentORM.propose, the SL_DOCUMENT.ID_PROPOSE column continues to be not filled.
The ideal would be if SL_DOCUMENT had a discriminator column and ProposeORM was a DocumentORM subclass, using the JOINED InheritanceType (there are other tables with the same kind of relationship with SL_DOCUMENT). However, these are legacy tables and it is not possible to change it.
So, what is the alternative to fill SL_DOCUMENT.ID_PROPOSE? A workaround I was thinking is fill this column using a native SQL. Do you have better ideas?
Thanks,
Rafael Afonso

Answer 1

The solution I see is to make ProposeORM's ID not auto-generated, since you always want it to have the ID of the document it's linked to, AND still have a join column in the document table:
#Entity
#Table(name = "SL_DOCUMENT")
public class DocumentORM {
#Id
#Column(name = "ID_DOCUMENT")
#SequenceGenerator(name = "SEQ_SL_DOCUMENT", sequenceName = "SEQ_SL_DOCUMENT")
#GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "SEQ_SL_DOCUMENT")
private Long id;
#OneToOne
#JoinColumn(name = "ID_PROPOSE")
private ProposeORM propose;
// ...
}
#Entity
#Table(name = "SL_PROPOSE")
public class ProposeORM {
#Id
#Column(name = "ID_PROPOSE")
private Long id;
#OneToOne(mappedBy = propose)
private DocumentORM document;
// ...
public ProposeORM(DocumentORM document) {
super();
this.id = document.getId();
this.document = document;
this.document.setPropositura(this);
}
}
You'll have to persist the document first, flush the EntityManager to make sure the document has a generated ID, and then persist the propose and set it into the document.