title: Unidirectional one-to-one relationship
body: <p>How do I achieve a unidirectional one to one relationship for Person and PersonData?</p>
  
  <pre><code>@Entity
  public class Person  {
      @Id
      @GeneratedValue(strategy=GenerationType.IDENTITY)
      private Long id;
  
      // @OneToOne...?
      // ...?
      private PersonData data;
  }
  
  @Entity
  public class PersonData {
      @Id
      private long personId;
  }
  </code></pre>