JPA org.hibernate.LazyInitializationException / Spring @Transactional

Hi,
ich erhalte folgende Error-message (s.u.), wenn ich auf meine getChildren() Methode meiner TreeNode-Klasse zugreifen will. Hier der Code:

Code (Text):

@Entity
@Transactional
public class TreeNode implements Serializable{

    @Id
    @GeneratedValue
    protected Long id;
    protected String name="";
   
    @ManyToOne
    protected Device device = null;
       
    @ManyToOne
    @JoinColumn(name="parent_id")
    protected TreeNode parent = null;
   
     @OneToMany(mappedBy="parent", fetch...

JPA org.hibernate.LazyInitializationException / Spring @Transactional

JPA org.hibernate.LazyInitializationException / Spring @Transactional