Thanks for replying Andrus. I cam up with a solution to the problem that I will detail below. the problem only seemed to manifest itself when I was using Tapestry. It may have to do with Tapestry holding on to objects in memory ot manipulating them in some way that led to Cayenne assuming they were in the same context. I can't be certain as it has been quite erratic but consistently broken.
To get around it, I am creating a new context and I have implemented my own version of localObject as such public static DataObject localDataObject(DataContext dataContext,DataObject dataObject) { DataObject localDataObject = dataObject; if (dataContext != null && dataObject != null && !dataObject.getDataContext().equals(dataContext)) { // in most cases this just works localDataObject = (DataObject)dataContext.localObject( dataObject.getObjectId(),null); //but for new objects in nested contexts it does not work and adding a prototype to the call above returns //a committed dataObject which fails on a fetch as it is a temporary id // so deep merge with the object we are trying to localise from if (dataObject.getObjectId().isTemporary() && localDataObject.getPersistenceState() == PersistenceState.HOLLOW) { CayenneUtil.deepMerge(dataObject,localDataObject); } //don't really need to do this but it did cause issues elsewhere for some odd reason if (localDataObject.getPersistenceState() == PersistenceState.HOLLOW && !dataObject.getObjectId().isTemporary()) { dataContext.getObjectStore().resolveHollow(localDataObject); } } return localDataObject; } And for some reason as you can see in the code above I was getting hollow new dataObjects which would cause a fetch to the database and this is completely wrong. So I have had to force a deepMerge of the object I am trying to localise and these are the details of the method below /** * visit every property of fromDataObject and copy the values to toDataContext making sure the values are in the proper dataContext * * @param fromDataObject * @param toDataObject */ @SuppressWarnings("unchecked") public static void deepMerge(final DataObject fromDataObject, final DataObject toDataObject) { ClassDescriptor descriptor = toDataObject.getDataContext ().getEntityResolver().getClassDescriptor(toDataObject.getObjectId ().getEntityName()); //we want the localised object to have the same state as the other toDataObject.setPersistenceState(fromDataObject.getPersistenceState ()); descriptor.injectValueHolders(toDataObject); descriptor.visitProperties(new PropertyVisitor() { public boolean visitCollectionArc(CollectionProperty property) { PropertyAccessor accessor = new DataObjectAccessor( property.getName()); ToManyList oldList = (ToManyList)property.readProperty(fromDataObject); //lists are annoying. we need to make sure the owner of the list is the new object which requires a copy ToManyList newList = new ToManyList(toDataObject, oldList.getRelationship()); Iterator<DataObject> it = oldList.iterator(); //then we need to localise every object in the list as well otherwise a real mess while (it.hasNext()) { newList.add(CayenneUtil.localDataObject( toDataObject.getDataContext(),it.next())); } accessor.writePropertyDirectly(toDataObject, property.readProperty(toDataObject), newList); return true; } public boolean visitSingleObjectArc(SingleObjectArcProperty property) { PropertyAccessor accessor = new DataObjectAccessor( property.getName()); Object newValue = property.readProperty(fromDataObject); //we need to to make sure relationship pull in objects from the same context so recurse here if (newValue instanceof DataObject) { newValue = CayenneUtil.localDataObject( toDataObject.getDataContext(),(DataObject)newValue); } accessor.writePropertyDirectly(toDataObject, property.readProperty(toDataObject), newValue); return true; } public boolean visitProperty(Property property) { PropertyAccessor accessor = new DataObjectAccessor( property.getName()); accessor.writePropertyDirectly(toDataObject, property.readProperty(toDataObject), property.readProperty(fromDataObject)); return true; } }); } And finally, because I am using a new dataContext, i want to merge the changes back into the threaded context so I have done this newObject().getDataContext().setChannel(this.getDataContext()); // this.getDataContext() is the threaded context CayenneUtil.syncDataContexts(this.getDataContext(), newNode().getDataContext()); newNode().getDataContext().commitChangesToParent(); Seems quite wrong setting the channel like this but it seems to work. The only issue I had was the context failed to merge properly because the objects I fetched in the new context did not exist in the context I was trying to merge in to at commitToParent hence the call CayenneUtil.syncDataContexts(...,...) above. The details are below /** * play with new contexts and add or remove objects or even fetch objects and if you want to merge back * to another context you need to force the existing context to fetch the existing objects as it won't * touch them in the merge * * @param existingDataContext * @param newDataContext */ public static void syncDataContexts(DataContext existingDataContext, DataContext newDataContext) { Iterator it = newDataContext.getGraphManager ().registeredNodes().iterator(); while (it.hasNext()) { try { DataObjectUtils.objectForPK(existingDataContext, ((DataObject)it.next()).getObjectId()); } catch (Exception e) { //we don't care about errors as those will be temp id's in most cases } } } /** * play with new contexts and add or remove objects or even fetch objects and if you want to merge back * to another context you need to force the existing context to fetch the existing objects as it won't * touch them in the merge * * @param existingDataContext * @param newDataContext */ public static void syncDataContexts(DataContext existingDataContext, DataContext newDataContext) { Iterator it = newDataContext.getGraphManager ().registeredNodes().iterator(); while (it.hasNext()) { try { DataObjectUtils.objectForPK(existingDataContext, ((DataObject)it.next()).getObjectId()); } catch (Exception e) { //we don't care about errors as those will be temp id's in most cases } } } It all seems very convoluted but it works. I am not sure what side effects this causes and I am not happy to be manipulating objects at this level as all might change when you move to 3.0 and everything here breaks. I would appreciate any thoughts you may have. Regards ed On 11/01/07, Andrus Adamchik <[EMAIL PROTECTED]> wrote:
Hi Edward, Sorry for delayed reply. >> AnotherClass newObject = >> (AnotherClass)childContext.createAndRegisterNewObject >> (AnotherClass.class); >> AClass localParentObject = (AClass)childContext.localObject >> (parent.getObjectId(),null); >> >> object.setParent(localParent); I assume 'object' is same as 'newObject'? >> For some reason I seem to get the parent having two children, not >> just the >> one! I assume it is because the changes in the childContext are >> propagated >> to the parent context so as a result the first setParent call adds >> the child >> to the parent and on commit changes the child is added again to >> the parent. No - actually the changes are only propagated on commit. So this behavior does look like a bug. I suggest to check whether this happens with the latest code (unofficial 2.0.2 and 1.2.2 builds can be downloaded from here: http://people.apache.org/~aadamchik/release/ 2.0.2/ ) If it still happens, please open a bug report. > What is the real purpose of passing a prototype? To merge data from a different object. I must admit that cramming all possible merge scenarios in a single 'localObject' method does create some confusion. We may come up with a better way to transfer and merge objects in the future. Andrus On Jan 8, 2007, at 11:48 AM, edward pedersson wrote: > Have been digging around the dataContext and I saw this in the > localObject > method > > // TODO: Andrus, 1/24/2006 implement smart merge for > modified > objects... > if (cachedObject != prototype > && state != PersistenceState.MODIFIED > && state != PersistenceState.DELETED) { > > I believe this may be causing one of the problems below. If you call > localObject with a new object and a prototype then the checks above > are true > and as a result this gets called further down the chain in the same > method > > descriptor.shallowMerge(prototype, cachedObject); > > which sets all the relationships to faults and this breaks because > the new > object is not committed. > > Is this a bug? What is the real purpose of passing a prototype? > > On 05/01/07, edward pedersson <[EMAIL PROTECTED]> wrote: >> >> Hi >> >> I am using the latest version of Cayenne with Tapestry 4.0.1. >> >> I am having a bit of trouble using nested dataContexts. I would >> like the >> user to be able to create a new object in a wizrd style >> application but have >> the option to cancel half way through the stages. >> >> I have tried a few different options and noe seem to work. In the >> first >> instance I tried the nested datacontext like this: >> >> AClass parent; //assume this exists and is in the threaded context >> >> DataContext childContext = this.getDataContext().createChildContext >> () // >> this.getDataContext() is the threaded context >> >> AnotherClass newObject = >> (AnotherClass)childContext.createAndRegisterNewObject >> (AnotherClass.class); >> AClass localParentObject = (AClass)childContext.localObject( >> parent.getObjectId(),null); >> >> object.setParent(localParent); >> >> //do other stuff here like set other properties >> >> // now save to parent >> >> childContext.commitChangesToParent(); >> >> For some reason I seem to get the parent having two children, not >> just the >> one! I assume it is because the changes in the childContext are >> propagated >> to the parent context so as a result the first setParent call adds >> the child >> to the parent and on commit changes the child is added again to >> the parent. >> >> So I tried to have separate dataContexts instead by doing this >> >> DataContext anotherContext = DataContext.createDataContext() >> >> AnotherClass newObject = >> (AnotherClass)anotherContext.createAndRegisterNewObject >> (AnotherClass.class >> ); >> AClass localParentObject = (AClass)anotherContext.localObject( >> parent.getObjectId(),null); >> >> object.setParent(localParent); >> >> //do other stuff here like set other properties >> >> // now save to parent >> newObject = (AClass)this.getDataContext().localObject( >> newObject.getObjectId(),null); >> >> >> I get errors like Can't build a query for relationship '...' for >> temporary >> id: >> >> Does anyone knew what I am doing wrong? >> >> many thanks for your help. >> >> -- >> >> >> -- e > > > > > -- > > > -- e
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