How to make an entity out of a join table without primary key
- by tputkonen
I'm trying to generate JPA entities out of an existing database having an "interesting" design.
Database has a table called UserSet, which can have links to several other UserSets. There is a one to many relation between UserSets and LinkedUserSets. LinkedUserSets also has one to one relation to UserSets.
I tried to generate a JPA Entity out of the database structure using Dali JPA Tools. The resulting entity Linkeduserset misses @Id or @EmbeddedId annotation and thus failes to compile. As the resulting entity contains only two @JoinColumns (which cannot be marked as @Id), I have not so far found a way around this issue.
Database structure can not be modified in any way.
Is there a way to overcome this somehow?
Relevant pars of create table statements:
CREATE TABLE `LinkedUserSets` (
`UsrSetID` INT(11) NOT NULL DEFAULT '0' ,
`ChildID` INT(11) NOT NULL DEFAULT '0' ,
CONSTRAINT `fk_LinkedUserSets_UserSet1`
FOREIGN KEY (`UsrSetID` )
REFERENCES `UserSet` (`UsrSetID` ));
CREATE TABLE `UserSet` (
`UsrSetID` INT(11) NOT NULL AUTO_INCREMENT ,
PRIMARY KEY (`UsrSetID`),
CONSTRAINT `fk_UserSet_LinkedUserSets1`
FOREIGN KEY (`UsrSetID` )
REFERENCES `LinkedUserSets` (`ChildID` ));
Generated entities:
@Entity
@Table(name="linkedusersets")
public class Linkeduserset {
//bi-directional many-to-one association to Userset
@ManyToOne
@JoinColumn(name="UsrSetID")
private Userset userset1;
//bi-directional one-to-one association to Userset
@OneToOne
@JoinColumn(name="ChildID")
private Userset userset2;
}
@Entity
@Table(name="userset")
public class Userset {
private static final long serialVersionUID = 1L;
@Id
@Column(name="UsrSetID")
private int jngSetID;
//bi-directional many-to-one association to Linkeduserset
@OneToMany(mappedBy="userset1")
private Set<Linkeduserset> linkedusersets;
//bi-directional one-to-one association to Linkeduserset
@OneToOne(mappedBy="userset2")
private Linkeduserset linkeduserset;
}
Error message:
Entity "Linkeduserset" has no Id or EmbeddedId
