In my application I have bi-directional one-to-many relationship
between Venue and Tip.
@Entity
public class Venue implements Serializable {
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
private Key key;
@OneToMany(cascade = CascadeType.ALL, mappedBy="venue")
private List<Tip> tips;
@Entity
public class Tip implements Serializable {
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
private Key key;
private Integer version;
@ManyToOne(fetch = FetchType.LAZY)
private Venue venue;
I have venue object persisted and then tip is added to the venue. I
don't any any problem in doing this.
Venue venue = venueService.find(key);
venue.addTip(tip);
venueService.merge(venue);
Then I expand the relationship to have another bi-directional one-to-
many relationship between Person and Tip. Tip is posted by a Person
and for a Venue. One Person can post more than one Tips for a Venue.
@Entity
public class Tip implements Serializable {
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
private Key key;
@ManyToOne(fetch = FetchType.LAZY)
private Venue venue;
@ManyToOne(fetch = FetchType.LAZY)
private Person postedBy;
@Entity
public class Person implements Serializable, UserDetails {
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
private Key key;
@OneToMany(cascade = CascadeType.ALL, mappedBy="postedBy")
private List<Tip> tips;
Venue venue = venueService.find(key);
Person person = personService.find(userId);
venue.addTip(tip);
person.addTip(tip);
venueService.merge(venue);
I am getting the following error:
Detected attempt to establish Person(29)/Tip(125) as the parent of
Venue(2) but the entity identified by Venue(2) has already been
persisted without a parent. A parent cannot be established or changed
once an object has been persisted.
org.datanucleus.store.appengine.FatalNucleusUserException: Detected
attempt to establish Person(29)/Tip(125) as the parent of Venue(2) but
the entity identified by Venue(2) has already been persisted without a
parent. A parent cannot be established or changed once an object has
been persisted. at
org.datanucleus.store.appengine.DatastoreRelationFieldManager.checkForParentSwitch
(DatastoreRelationFieldManager.java:204) at
org.datanucleus.store.appengine.DatastoreRelationFieldManager
$1.setObjectViaMapping(DatastoreRelationFieldManager.java:125) at
org.datanucleus.store.appengine.DatastoreRelationFieldManager$1.apply
(DatastoreRelationFieldManager.java:104) at
org.datanucleus.store.appengine.DatastoreRelationFieldManager.storeRelations
(DatastoreRelationFieldManager.java:78) at
org.datanucleus.store.appengine.DatastoreFieldManager.storeRelations
(DatastoreFieldManager.java:812) at
org.datanucleus.store.appengine.DatastorePersistenceHandler.insertPostProcess
(DatastorePersistenceHandler.java:288) at
org.datanucleus.store.appengine.DatastorePersistenceHandler.insertObjects
(DatastorePersistenceHandler.java:241) at
org.datanucleus.store.appengine.DatastorePersistenceHandler.insertObject
(DatastorePersistenceHandler.java:225) at
org.datanucleus.state.JDOStateManagerImpl.internalMakePersistent
(JDOStateManagerImpl.java:3185) at
org.datanucleus.state.JDOStateManagerImpl.flush
(JDOStateManagerImpl.java:4513) at
org.datanucleus.sco.SCOUtils.validateObjectForWriting(SCOUtils.java:
1494) at
org.datanucleus.store.mapped.scostore.ElementContainerStore.validateElementForWriting
(ElementContainerStore.java:380) at
org.datanucleus.store.mapped.scostore.FKListStore.validateElementForWriting
(FKListStore.java:609) at
org.datanucleus.store.mapped.scostore.FKListStore.internalAdd
(FKListStore.java:344) at
org.datanucleus.store.mapped.scostore.AbstractListStore.add
(AbstractListStore.java:105) at org.datanucleus.sco.backed.List.add
(List.java:649) at guestbook.domain.Person.addTip(Person.java:164) at
guestbook.web.mvc.TipController.create(TipController.java:94) at
Any idea? Your help is very much appreciated.
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