Kotlin JPA id fo composite key

Composite keys in Kotlin JPA have a few specific requirements that aren’t obvious from the documentation. The class must implement Serializable (Hibernate requires it), and serialVersionUID needs to be set explicitly. The @Id annotation goes on each field that’s part of the composite key — not on a separate @EmbeddedId class in this approach.

• Sample Table

Create table DataTable(
MainID number(19),
SecondaryId number(19),
TernaryId varchar2(20)
);

• Add composite key to the table

create unique index DataTable_idx on DataTable (MainID, SecondaryId, TernaryId);

• Kotlin code for composite key

@id is added to all the composite key fields

Serializable is added as it is required by kotlin

serialVersionUID is added as it is required by hibernate

@Entity 
@Table(name = "DataTable")
class DataIDLinks(
@Id@Column(name = "MainID", nullable = false) val mainID: Long,
@Id@Column(name = "SecondaryId", nullable = false) val secondaryId: Long,
@Id @Column(name = "TernaryId", nullable = true) val ternaryId: String ) : Serializable{
    companion object {
        private const val serialVersionUID: Long = 170010121L
    }
}