Modeling JPA entities

Previously, we learned how to define the basic unit of persistence—an entity, using a Kotlin data class. Let's now look at how we can define and map relations to the domain entities using JPA.

Mapping entities

We can establish a mapping between the entities using JPA's @OneToOne, @OneToMany, @ManyToOne, and @ManyToMany annotations.

Let's consider PersonEntity:

@Entity
class Person : Identity() {
    @Id
    lateinit var identifier: UUID
    lateinit var name: PersonName
    lateinit var loginId: String
    var preferredLanguage: PreferredLanguage? = null
}

Here, preferredLanguage is an enum, so it can be included with the @Enumerated annotation within the entity:

@Entity
class Person : Identity...