Question

I have a model objects relationship such as this:

@Table(name="cables")
class Cable {
    @Id
    private Long id;
    @Column(name="dstport_id")
    private Port dstPort;
    @Column(name="srcport_id")
    private Port srcPort;
}
@Table(name="ports")
class Port {
    @Id
    private Long id;
    private Cable cable; // Here's the mapping that should point to cables.dstport_id or cables.srcport_id whatever is present
}

In this relationship the mapping is a One-to-One mapping through Cable’s dstport_id OR srcport_id columns. A cable could be connected to none, one or two (exclusively different) ports. A Port could be connected to none or only one cable and to it’s either endpoint. So, is there a way in Hibernate to map such a relationship inside the Port entity (there’s no tricks to map it inside the Cable entity)?

Answer 1

I don’t believe it is possible to define the relationship from Port to Cable with only one association in Port.

In my view, your best option would be to define 2 optional, one-to-one associations to Cable in Port (dstPortCable and srcPortCable, say) using the ‘mappedBy’ joining method, and then define a method in Port, thus:

public Cable getCable() {
    if (dstPortCable != null) {
        return dstPortCable;
    }
    if (srcPortCable != null) {
        return srcPortCable;
    }
    return null;
}