Kotlin for Enterprise Applications using Java EE

ManyToOne mapping

It is also possible to back reference from the ContactDetails entity to the Person entity using the @ManyToOne annotation:

@Table(name = "contacts")@Entityclass ContactDetails {    @Id    private lateinit var id: Integer    lateinit var number: String    @Enumerated(EnumType.STRING)    private var type: ContactType? = null    @ManyToOne(cascade = arrayOf(CascadeType.ALL), fetch =      FetchType.LAZY)    lateinit var person: Person}

In the preceding code snippets, we have illustrated an example of the OneToMany and ManyToOne annotations. Similarly, we can use the OneToOne and ManyToMany annotations.

A relationship between two classes can be one of the following:

• Bidirectional: Both classes hold a reference to the other
• Unidirectional: Only one class ...