Please explain about: insertable=false, updatable=false

Question

Please rest assure that I did some search trying to understand about this as much as possible, but most of the community posts are about implementation instead of explanation. I guess I just dont understand it correctly, but if a field is annotated insertable=false, updatable=false, doesnt it mean that you cannot insert value nor change the existing value? Why would u want to do that?

EDIT: Do you mean something like this BalusC?

@Entity
public class Person {

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private Long id;

    @OneToMany(mappedBy="person", cascade=CascadeType.ALL)
    private List<Address> addresses;
}

@Entity
public class Address {

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private Long id;

    @ManyToOne
    @JoinColumn(name="ADDRESS_FK")
    @Column(insertable=false, updatable=false)
    private Person person;
}

Answer 1

You would do that when the responsibility of creating/udpating the related entity in question isn't in the current entity. E.g. you have a Person and an Address. You'd like to add insertable=false, updatable=false to the @OneToMany relationship with the Person entity in the Address entity, simply because it's not the responsibility of the Address entity to create or update a Person. It's the other way round. This is not really a technical, but more a semantic/natural decision.

Answer 2

Defining insertable=false, updatable=false is useful when you need to map a field more than once in an entity, typically:

• when using a composite key
• when using a shared primary key
• when using cascaded primary keys

This is IMO not a semantical thing, but definitely a technical one.