Hi,
Configuration:
- Appengine sdk 1.3.1
- 2 Entities: Indicator, Graph
/*
* INDICATOR.java
*/
@PersistenceCapable(identityType = IdentityType.APPLICATION,
detachable = "true")
@FetchGroup(name="graph", members = { @Persistent(name = "graph")})
public class Indicator {
@PrimaryKey
@Persistent
private String code;
@Persistent(defaultFetchGroup = "true", dependent = "true")
private Graph graph;
}
/*
* GRAPH.java
*/
public class Graph {
@PrimaryKey
@Persistent(valueStrategy = IdGeneratorStrategy.IDENTITY)
private Key id;
@Persistent
private String title;
}
/*
* DAO
*/
public Indicator saveOrUpdate(Indicator newIndicator) {
Indicator result;
PersistenceManager pm =PMF.getPersistenceManager();
try {
result = pm.makePersistent(newIndicator);
result = pm.detachCopy(result);
} finally {
pm.close();
}
return result;
}
/*
* UNIT_TEST
*/
public void test() {
Indicator withoutGraph = new Indicator("TEST");
assertEquals(null, withoutGraph.getGraph());
Indicator indicatorPersisted = dao.saveOrUpdate(withoutGraph);
assertEquals(null, indicatorPersisted.getGraph());
// create graph
Graph graph = new Graph();
graph.setTitle("Graphe TEST");
// add graph
indicatorPersisted.setGraph(graph);
assertNotNull(indicatorPersisted.getGraph());
Indicator indicatorPersisted =
dao.saveOrUpdate(indicatorPersisted);
}
BUT, here what i got:
"Detected attempt to establish Indicator("TEST") as the parent of
Graph(3) but the entity identified by Graph(3) has already been
persisted without a parent. A parent cannot be established or changed
once an object has been persisted.
org.datanucleus.store.appengine.DatastoreRelationFieldManager
$ChildWithoutParentException: Detected attempt to establish
Indicator("TEST") as the parent of Graph(3) but the entity identified
by Graph(3) 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:
207)
at org.datanucleus.store.appengine.DatastoreRelationFieldManager
$1.setObjectViaMapping(DatastoreRelationFieldManager.java:132)
at org.datanucleus.store.appengine.DatastoreRelationFieldManager
$1.apply(DatastoreRelationFieldManager.java:111)
at
org.datanucleus.store.appengine.DatastoreRelationFieldManager.storeRelations(DatastoreRelationFieldManager.java:
80)
at
org.datanucleus.store.appengine.DatastoreFieldManager.storeRelations(DatastoreFieldManager.java:
955)
at
org.datanucleus.store.appengine.DatastorePersistenceHandler.storeRelations(DatastorePersistenceHandler.java:
527)
at
org.datanucleus.store.appengine.DatastorePersistenceHandler.updateObject(DatastorePersistenceHandler.java:
519)
..."
Here the doc:
http://code.google.com/intl/fr-FR/appengine/docs/java/datastore/relationships.html#Owned_One_to_One_Relationships
It says that:
"Similarly, if the Employee object has already been saved and the
related ContactInfo object is new, App Engine creates the ContactInfo
entity using the existing Employee entity as the parent."
Thanks!
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