Hi Anita. I don't understand your data model -- if you are modeling the
relationship between entities of type A and entities of type B using
entities of type C, why do entities of type A have direct references to
entities of type B and vice versa?
Either way, the reason you're getting this error is because you're
inadvertently attempting to set an owned relationship between entities of
types A and B under type C, and doing this tries to modify the keys of types
A and B after they've been persisted, which you can't do. Try changing the
following:
@PersistenceCapable(identityType = IdentityType.APPLICATION)
public class TableC implements Serializable{
@PrimaryKey
@Persistent(valueStrategy = IdGeneratorStrategy.IDENTITY)
private Key id;
@Persistent
private Key tablea;
@Persistent
private Key tableb;
.....
This should just store a reference to the entity's key (unowned
relationship) rather than trying to modify the keys of the A and B entities.
- Jason
On Tue, Sep 15, 2009 at 1:34 AM, Anita <an...@ensarm.com> wrote:
>
> Hi Jason,
>
> I could solve my previous problem. But now i am facing some other
> problem with many to many relationship tables.
>
> My schema looks as follows:
>
> TableA ---> TableC <----- TableB
> which means there is many to many relationship between TableA &
> TableB. So i want TableA and TableB primary keys into TableC as
> foreign key.
>
> TableA class looks as follows:
>
> @PersistenceCapable(identityType = IdentityType.APPLICATION)
> public class TableA implements Serializable{
> @PrimaryKey
> @Persistent(valueStrategy = IdGeneratorStrategy.IDENTITY)
> private Key id;
> ......
> @Persistent(defaultFetchGroup="true")
> private Set<Key> tableB = new HashSet<Key>();
> ......
> (some getter & setter)
>
> TableB class looks as follows:
>
> @PersistenceCapable(identityType = IdentityType.APPLICATION)
> public class TableB implements Serializable{
> @PrimaryKey
> @Persistent(valueStrategy = IdGeneratorStrategy.IDENTITY)
> private Key id;
> ......
> @Persistent(defaultFetchGroup="true")
> private Set<Key> tableA = new HashSet<Key>();
> ......
> (some getter & setter)
>
> TableC class looks as follows:
> @PersistenceCapable(identityType = IdentityType.APPLICATION)
> public class TableC implements Serializable{
> @PrimaryKey
> @Persistent(valueStrategy = IdGeneratorStrategy.IDENTITY)
> private Key id;
>
> @Persistent
> private TableA tablea;
>
> @Persistent
> private TableB tableb;
> .....
> (some getter & setter)
>
> While adding data into TableC i use following code:
>
> Query query1 = pm.newQuery(TableA.class);
> List<TableA> results1 = (List<TableA>) query1.execute();
> TableA tableA= results1.get(0);
>
> Query query2 = pm.newQuery(TableB.class);
> List<TableB> results2 = (List<TableB>) query2.execute();
> TableB tableB= results2.get(0);
>
> tableA.add(tableB);
> tableB.add(tableA);
>
> At this point TableA and TableB values are getting update but while
> entering data into TableC the problem comes.
> TableC tableC = new TableC();
> tableC.setTableA(tableA);
> tableC.setTableB(tableB);
> pm.makePersistent(tableC); --> at this point it gives me "A parent
> cannot be established or changed once an object has been persisted."
>
> Can you please tell me were i am going wrong?
>
> Thanks
> Anita
>
> On Sep 15, 3:54 am, "Jason (Google)" <apija...@google.com> wrote:
> > From the error message, it sounds like the parent isn't getting set
> > correctly. You'll need to share some of your code in order for me to help
> > you further -- what does your Release class look like and how are you
> > persisting it?
> >
> > - Jason
> >
> > On Sat, Sep 12, 2009 at 4:36 AM, Anita <an...@ensarm.com> wrote:
> >
> > > Hi Jason,
> >
> > > Our schema looks as follows:
> > > ProductType 1--------->M Product 1-------->M Release
> >
> > > Data is inserting into Release table. But while fetching data from
> > > release table i am getting following exception:
> >
> > > Field com.ensarm.server.domain.Release.products should be able to
> > > provide a reference to its parent but the entity does not have a
> > > parent. Did you perhaps try to establish an instance of
> > > com.ensarm.server.domain.Release as the child of an instance of
> > > com.ensarm.server.domain.Products after the child had already been
> > > persisted?
> > > org.datanucleus.exceptions.NucleusUserException: Field
> > > com.ensarm.server.domain.Release.products should be able to provide a
> > > reference to its parent but the entity does not have a parent. Did
> > > you perhaps try to establish an instance of
> > > com.ensarm.server.domain.Release as the child of an instance of
> > > com.ensarm.server.domain.Products after the child had already been
> > > persisted?
> > > at
> > >
> org.datanucleus.store.appengine.DatastoreRelationFieldManager.lookupParent
> > > (DatastoreRelationFieldManager.java:302)
> > > at
> >
> > >
> org.datanucleus.store.appengine.DatastoreRelationFieldManager.fetchRelationField
> > > (DatastoreRelationFieldManager.java:289)
> > > at
> > > org.datanucleus.store.appengine.DatastoreFieldManager.fetchObjectField
> > > (DatastoreFieldManager.java:271)
> > > at
> org.datanucleus.state.AbstractStateManager.replacingObjectField
> > > (AbstractStateManager.java:1197)
> > > at
> com.ensarm.server.domain.Release.jdoReplaceField(Release.java)
> > > at
> com.ensarm.server.domain.Release.jdoReplaceFields(Release.java)
> > > at org.datanucleus.state.JDOStateManagerImpl.replaceFields
> > > (JDOStateManagerImpl.java:2772)
> > > at org.datanucleus.state.JDOStateManagerImpl.replaceFields
> > > (JDOStateManagerImpl.java:2791)
> > > at
> > > org.datanucleus.store.appengine.DatastorePersistenceHandler.fetchObject
> > > (DatastorePersistenceHandler.java:349)
> > > at
> org.datanucleus.store.appengine.query.DatastoreQuery.entityToPojo
> > > (DatastoreQuery.java:384)
> > > at
> org.datanucleus.store.appengine.query.DatastoreQuery.entityToPojo
> > > (DatastoreQuery.java:345)
> > > at
> org.datanucleus.store.appengine.query.DatastoreQuery.access$700
> > > (DatastoreQuery.java:96)
> > > at org.datanucleus.store.appengine.query.DatastoreQuery$5.apply
> > > (DatastoreQuery.java:454)
> > > at org.datanucleus.store.appengine.query.DatastoreQuery$5.apply
> > > (DatastoreQuery.java:453)
> > > at
> > > org.datanucleus.store.appengine.query.StreamingQueryResult.resolveNext
> > > (StreamingQueryResult.java:137)
> > > at org.datanucleus.store.appengine.query.StreamingQueryResult
> > > $1.computeNext(StreamingQueryResult.java:163)
> > > at
> > > org.datanucleus.store.appengine.query.AbstractIterator.tryToComputeNext
> > > (AbstractIterator.java:132)
> > > at
> org.datanucleus.store.appengine.query.AbstractIterator.hasNext
> > > (AbstractIterator.java:127)
> > > at org.datanucleus.store.appengine.query.StreamingQueryResult
> > > $AbstractListIterator.hasNext(StreamingQueryResult.java:229)
> > > at com.ensarm.server.servlet.GetData.getRelease(GetData.java:87)
> > > at com.ensarm.server.servlet.GetData.doGet(GetData.java:32)
> > > at javax.servlet.http.HttpServlet.service(HttpServlet.java:693)
> > > at javax.servlet.http.HttpServlet.service(HttpServlet.java:806)
> > > at
> > > org.mortbay.jetty.servlet.ServletHolder.handle(ServletHolder.java:
> > > 487)
> > > at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter
> > > (ServletHandler.java:1093)
> > > at
> > > com.google.apphosting.utils.servlet.TransactionCleanupFilter.doFilter
> > > (TransactionCleanupFilter.java:43)
> > > at
> org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter
> > > (ServletHandler.java:1084)
> > > at
> com.google.appengine.tools.development.StaticFileFilter.doFilter
> > > (StaticFileFilter.java:124)
> > > at
> org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter
> > > (ServletHandler.java:1084)
> > > at org.mortbay.jetty.servlet.ServletHandler.handle
> > > (ServletHandler.java:360)
> > > at org.mortbay.jetty.security.SecurityHandler.handle
> > > (SecurityHandler.java:216)
> > > at org.mortbay.jetty.servlet.SessionHandler.handle
> > > (SessionHandler.java:181)
> > > at org.mortbay.jetty.handler.ContextHandler.handle
> > > (ContextHandler.java:712)
> > > at
> org.mortbay.jetty.webapp.WebAppContext.handle(WebAppContext.java:
> > > 405)
> > > at
> > > com.google.apphosting.utils.jetty.DevAppEngineWebAppContext.handle
> > > (DevAppEngineWebAppContext.java:54)
> > > at org.mortbay.jetty.handler.HandlerWrapper.handle
> > > (HandlerWrapper.java:139)
> > > at com.google.appengine.tools.development.JettyContainerService
> > > $ApiProxyHandler.handle(JettyContainerService.java:313)
> > > at org.mortbay.jetty.handler.HandlerWrapper.handle
> > > (HandlerWrapper.java:139)
> > > at org.mortbay.jetty.Server.handle(Server.java:313)
> > > at
> > > org.mortbay.jetty.HttpConnection.handleRequest(HttpConnection.java:
> > > 506)
> > > at
> org.mortbay.jetty.HttpConnection$RequestHandler.headerComplete
> > > (HttpConnection.java:830)
> > > at org.mortbay.jetty.HttpParser.parseNext(HttpParser.java:514)
> > > at
> org.mortbay.jetty.HttpParser.parseAvailable(HttpParser.java:211)
> > > at
> org.mortbay.jetty.HttpConnection.handle(HttpConnection.java:381)
> > > at org.mortbay.io.nio.SelectChannelEndPoint.run
> > > (SelectChannelEndPoint.java:396)
> > > at org.mortbay.thread.BoundedThreadPool$PoolThread.run
> > > (BoundedThreadPool.java:442)
> >
> > > What should be done for this problem?
> >
> > > Anita
> >
>
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