Is it possible to map a field in an Entity without defining any association?

Question

I\'ve got the following schema in DB (simplified)

MainTable(
    ID primary key
    SOMEFIELD
    CODE_FK1 -- references OtherTable1 CODE (without declared forei         


        

Answer 1

You can use the @SecondaryTable annotation. See this example:

https://github.com/hibernate/hibernate-orm/blob/823a5c1ede1869fd97471e3b8ebe7ec4ac8068e4/hibernate-core/src/test/java/org/hibernate/test/annotations/join/Dog.java#L20-L24

Answer 2

Another possibility would be using the @Formula annotation to fetch the value from the other table. This will automatically generate a subselect whenever you load your Entity.

I think you'll need something like this:

    @Entity
public class MainEntity{
    @Id
    private Integer ID;

    @Column(name="SOMEFIELD")
    private String SomeField;

    @Formula("(SELECT ot1.LABEL FROM OtherTable1 ot1 WHERE ot1.CODE = CODE_FK_1)")
    private String Label1;

}

There is little information about this in the [Hibernate docs][1], so you may need some trial and error to get it right (but you should be able to work it out with hibernate.show_sql=true.

There are 2 possible downsides to this approach:

1. This is hibernate-specific code
2. This is plain SQL, and may thus be database-specific

HTH

[1]: http://docs.jboss.org/hibernate/stable/annotations/reference/en/html_single/#entity-hibspec-property hibernate docs