Merge with JPA and subclass ID - jpa

Question

I got two entities like this (second one have a relation with first one) :
#Entity
#Table(name="FOA_ADRESSE_ICX")
public class FoaAdresseIcx implements Serializable {
private static final long serialVersionUID = 1L;
#Id
#Column(name="ID_ADRESSE", unique=true, nullable=false, precision=5)
private long idAdresse;
#Column(length=32)
private String bat;
#Column(name="COD_POSTAL", length=5)
private String codPostal;
// getters and setters ....
}
#Entity
#Table(name="FOA_INFOS_ICX")
public class FoaInfosIcx implements Serializable {
private static final long serialVersionUID = 1L;
#Id
#Column(name="COD_ICX", unique=true, nullable=false, length=8)
private String codIcx;
#Column(name="DATE_RAFFRAICHISEMENT")
#Temporal(TemporalType.TIMESTAMP)
private Date dateRaffraichisement;
#Column(name="LIB_AGENCE", nullable=false, length=98)
private String libAgence;
//uni-directional many-to-one association to FoaAdresseIcx
#ManyToOne
#JoinColumn(name="ID_ADRESSE", nullable=false)
private FoaAdresseIcx foaAdresseIcx;
// getters and setters....
}
I got a problem with the merge :
myEntityMgr.merge(myFoaInfosIcx);
Got this exception :
GRAVE: EJB Exception: : javax.persistence.EntityNotFoundException: Unable to find com.groupama.middlgan.entities.FoaAdresseIcx with id 0
In myFoaInfosIcx id is 0 because I don't initialise it, because I want JPA to create new FoaAdresseIcx in database if doesn't exist.
How can I do that ?

Answer 1

Using primitive types as DB ids has the downside you are currently experiencing. The default value is 0, which is a perfectly valid value for a DB id.
The persistence provider assumes that the entity is not new, but detached and behaves accordingly.
A solution is to use wrapper classes (or other non-primitive classes like UUID) as ids - Long in you case. Unless explicitly instantiated, the id attributes will be null and the provider will correctly identify an entity as new.