@Entity
public class Company
        implements Serializable
{

  @Id
  private Long id;

  @Column(nullable = false, unique=true)
  private String name; 

  public Company()
  {
  }
  getter .. setter...
}



@Embeddable
public class Apk
        implements Serializable
{

  @ManyToOne(optional = false)
  private Company company;

  @NotNull
  @Column(nullable = false)
  private Long id;

  public Apk()
  {
  }
  getters.. setter...
}


@Entity
@Inheritance(strategy=InheritanceType.JOINED)
public abstract class A
        implements Serializable
{

  @Id
  private Apk id;
  private String jpt;
 
  public A()
  {
  }
}


@Entity
@DiscriminatorValue(value="B")
public class B
        extends A
        implements Serializable
{
 
  public B()
  {
  }
}