Hibernate Unidirectional OneToMany with composite key

Question

I wanted to frame Hibernate OneToMany relationship where Parent has a composite primary key and Child has a primary key (hibernate-auto generated). Below is my working sample code :

class Parent{

    @EmbeddedId
    private ParentPk parentPk;

    @OneToMany( mappedBy="parent")
    private List<ChildType1>;

    @OneToMany( mappedBy="parent")
    private List<ChildType2>;

    @OneToMany( mappedBy="parent")
    private List<ChildType3>;

    //--setters and getters
}

@Embeddable
public class ParentPk {

    private Long parentId;

    private BigDecimal version;

    //..setters and getters
}

class ChildType1{
    @Id
    private Long childId;

    @ManyToOne(cascade = CascadeType.ALL)
    @JoinColumns({ @JoinColumn(name = "parentId"),
            @JoinColumn(name = "version") })
    private Parent parent;

    //..other fields and setters and getters
}

//--ChildType2 and ChildType3 like above

But now I wanted to model above as OneToMany unidirectional relationship, i.e., a child should not reference the parent (want to omit Parent instance in the child class). Is it possible?

Yes, it's possible. Put the JoinColumns annotation on the List in the parent class. — JB Nizet, May 02 '15 at 07:38

score 4 · Accepted Answer · answered May 02 '15 at 07:48

An example approach:

@Entity
class Parent {
    @EmbeddedId
    private ParentPk parentPk;

    @OneToMany
    @JoinColumns({ 
        @JoinColumn(name = "parentId", referencedColumnName = "parentId"), 
        @JoinColumn(name = "version", referencedColumnName = "version")
    })
    private List<ChildType1> children1;

    // exactly the same annotations as for children1
    private List<ChildType2> children2;

    // exactly the same annotations as for children1
    private List<ChildType3> children3;

    //..other fields and setters and getters
}

@Entity
class ChildType1 {
    @Id
    private Long childId;

    //..other fields and setters and getters
}

//--ChildType2 and ChildType3 like above

What if I have EmbeddedId at both parent and child side(both has different columns), and I want to map OneToMany from Parent to Child. I can't use @JoinColumns as one column is not at both end. and not working with mappedBy also... any idea? — Bhaumik Thakkar, Jan 28 '22 at 12:04

Hibernate Unidirectional OneToMany with composite key

1 Answers1