Question

Is there a way to create a composite key in Hibernate, with annotations, without creating a new PK class (ie, @EmbeddedId)?

My problem is, I have a abstract class CommonClass that have many attributes, and I neen to inherit it for many Entity classes. Each class has an different type of id, but all of them need to be a composite key with a attribute that is at CommonClass.
Example:

@MappedSuperclass
abstract class CommonClass {
    @Id
    int typed;

    int a0;
    int a1;
    //many other attributes
}

@Entity
class EntityString extends CommonClass {
    @Id
    String id;
    //ID need to be id+typed from CommonClass

    //other attributes
}

@Entity
class EntityInteger extends CommonClass {
    @Id
    Integer id;
    //ID need to be id+typed from CommonClass

    //other attributes
}

So, what is the best way to do this?

Answer 1

Section 2.2.3.2.2 of the following hibernate doc.

Another, arguably more natural, approach is to place @Id on multiple
properties of my entity. This approach is only supported by Hibernate
but does not require an extra embeddable component.

@Entity
class Customer implements Serializable {
  @Id @OneToOne
  @JoinColumns({
    @JoinColumn(name="userfirstname_fk", referencedColumnName="firstName"),
    @JoinColumn(name="userlastname_fk", referencedColumnName="lastName")
  })
  User user;

  @Id String customerNumber;

  boolean preferredCustomer;
}

@Entity 
class User {
  @EmbeddedId UserId id;
  Integer age;
}

@Embeddable
class UserId implements Serializable {
  String firstName;
  String lastName;
}