ManyToOne relation where a column is referenced with concatenation of two columns

Question

I'm trying to create a ManyToOne relation between two entities. The tables are looking like this:

---

Table:EQUIPMENT
----------------
ID (Integer PK)    
FIXTURE_NO(Varchar 16)

Table:FIXTURE
----------------
ID(Integer PK)
TNO(Varchar 4)
DNO(Varchar 12)

---

While creating entities, I want to create a many to one relation where fixture No = tNo+dNo (concatenation of these two values.)

Here are the code samples of my models:

    @Entity
    @Table(name="EQUIPMENT", schema="EQP")
    public class Equipment {

        @Id
        @GeneratedValue(strategy=GenerationType.IDENTITY)
        @NotNull
        @Column(unique=true)
        private int id;

        @NotNull
        @ManyToOne
        @JoinColumn(name="FIXTURE_NO")
        private Fixture fixture;

        //getters and setters etc...
    }

    @Entity
    @Table(name="FIXTURE", schema="FIX")
    public class Fixture {

        @Id
        @GeneratedValue(strategy=GenerationType.IDENTITY)
        @NotNull
        @Column(unique=true)
        private int id;

        @Size(max=4)
        @Column(name="TNO")
        private String tNo;

        @Size(max=12)
        @Column(name="DNO")
        private String dNo;

        //getters and setters etc...
    }

Right now, I see that the ManyToOne mapping is relating to EQUIPMENT.FIXTURE_NO with FIXTURE.ID, but I couldn't find a way to map the concatenation of TNO and DNO with FIXTURE_NO.

Thanks for the help!

Answer 1

It will not work with concatenation but if you change your datamodel to:

Table:EQUIPMENT
----------------
ID (Integer PK)    
TNO(Varchar 4)
DNO(Varchar 12)

Table:FIXTURE
----------------
ID(Integer PK)
TNO(Varchar 4)
DNO(Varchar 12)

You can add a relationship like this:

@ManyToOne
@JoinColumns({
    @JoinColumn(name="TNO", referencedColumnName="TNO"),
    @JoinColumn(name="DNO", referencedColumnName="DNO")
})
private Fixture fixture;