It is possible to use a reference to objects of the same type. Say for example for a hierarchical list of topics:
@Entity
@Table(name="TOPIC")
@Inheritance(strategy=InheritanceType.JOINED)
public class Topic extends BaseObject implements Serializable {
@OneToMany(mappedBy="parentTopic")
@OrderBy(value="posInParentTopic")
private List<Topic> topics;
@ManyToOne
@JoinColumn(name="TOPIC_ID")
private Topic parentTopic;
@Column(name="POS_IN_PARENT")
private int posInParentTopic;
//...
}
The last attribute is of course only relevant if the order of the elements in your list is important.
--
Wolfram Rittmeyer
Markus Karg wrote:
>I need to model an entity that points to iteself. The idea is to be able
>to build a possibly endless chain of entities of the same type. In SQL
>this is as simple as adding a foreign key to the same table. Is that
>possible in JPA? May an entity have a relation to iteself? Or is there
>another solution to this problem?
>
>Thanks
>Markus