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Posted to user@cayenne.apache.org by Detlef Burt <th...@gmx.net> on 2007/11/29 12:33:23 UTC
Replace Objects in a Database?
Hello,
after being able to keep my Data after sending my Objects via JMS
(Thanks Andrus) I now have a problem when I try to write the Objects
back into the Database.
After sending the Objects to the Client-Application, the Client changes
some data ( Just a timestamp in my Testcase ) and then sends an
Update-Request to the Server. Due to the fact, that the Client has no
access to the DataContext or the underlying ObjectStore, the changes
made to the Object won't be recorded.
After the Server receives the Object, it reconnects the Object to the
DataContext, thus being able to get a snapshot from the database or even
create an UpdateQuery.
But I can't go anywhere from here.
Executing the UpdateQuery won't have any effect because Cayenne doesn't
know what changed.
I also tried to get a Snapshot from the DB, convert my DataObject to a
DataRow and then create and register the diff of those by myself. But I
couldn't find anything like that :/
To sum it all up:
- Can I tell Cayenne to replace the Database Contents with the data from
my Object while retaining the ObjectId ?
- Can I tell Cayenne to "scan" an Object for changes and register the
differences, so that calling commitChanges will update the Object?
- Or is it possible to create a DataRow from a DataObject so I can
create and register an ObjectDiff ?
NOTE:
When updating the Object, I don't know what class is being updated and
what properties it has, all I have is my CayennePersistableObject
Baseclass, which extends CayenneDataObject.
Detlef
Re: Replace Objects in a Database?
Posted by Andrus Adamchik <an...@objectstyle.org>.
no estimates... still "nearest future" ;-)
On Apr 14, 2008, at 4:52 PM, Borut Bolčina wrote:
> Andrus,
>
> what is the "status" of this merge functionality? Any estimates?
>
> Thanks,
> Borut
>
> 2007/11/29 Andrus Adamchik <an...@objectstyle.org>:
>
>> In the nearest future we'll be adding a "merge" method to the
>> DataContext
>> that would do exactly what you described here - reattach an already
>> persistent and possibly modified object to the context. For now the
>> closest
>> analog is "localObject", but it will require some hacking. A
>> reattach method
>> may look like this:
>>
>> void reattach(Persistent object) {
>> // force "modified" on the object
>> object.setPersistenceState(PersistenceState.MODIFIED);
>> context.localObject(object.getObjectId(), object);
>> }
>>
>> This will do the right thing for objects not changed, but WILL NOT
>> do the
>> right thing for the newly inserted objects.
>>
>> Andrus
>>
>>
>>
>> On Nov 29, 2007, at 1:33 PM, Detlef Burt wrote:
>>
>> Hello,
>>>
>>> after being able to keep my Data after sending my Objects via JMS
>>> (Thanks Andrus) I now have a problem when I try to write the
>>> Objects back
>>> into the Database.
>>>
>>> After sending the Objects to the Client-Application, the Client
>>> changes
>>> some data ( Just a timestamp in my Testcase ) and then sends an
>>> Update-Request to the Server. Due to the fact, that the Client has
>>> no access
>>> to the DataContext or the underlying ObjectStore, the changes made
>>> to the
>>> Object won't be recorded.
>>> After the Server receives the Object, it reconnects the Object to
>>> the
>>> DataContext, thus being able to get a snapshot from the database
>>> or even
>>> create an UpdateQuery.
>>> But I can't go anywhere from here.
>>> Executing the UpdateQuery won't have any effect because Cayenne
>>> doesn't
>>> know what changed.
>>>
>>> I also tried to get a Snapshot from the DB, convert my DataObject
>>> to a
>>> DataRow and then create and register the diff of those by myself.
>>> But I
>>> couldn't find anything like that :/
>>>
>>> To sum it all up:
>>> - Can I tell Cayenne to replace the Database Contents with the
>>> data from
>>> my Object while retaining the ObjectId ?
>>> - Can I tell Cayenne to "scan" an Object for changes and register
>>> the
>>> differences, so that calling commitChanges will update the Object?
>>> - Or is it possible to create a DataRow from a DataObject so I can
>>> create and register an ObjectDiff ?
>>>
>>> NOTE:
>>> When updating the Object, I don't know what class is being updated
>>> and
>>> what properties it has, all I have is my CayennePersistableObject
>>> Baseclass,
>>> which extends CayenneDataObject.
>>>
>>> Detlef
>>>
>>>
>>>
>>
Re: Replace Objects in a Database?
Posted by Borut Bolčina <bo...@gmail.com>.
Andrus,
what is the "status" of this merge functionality? Any estimates?
Thanks,
Borut
2007/11/29 Andrus Adamchik <an...@objectstyle.org>:
> In the nearest future we'll be adding a "merge" method to the DataContext
> that would do exactly what you described here - reattach an already
> persistent and possibly modified object to the context. For now the closest
> analog is "localObject", but it will require some hacking. A reattach method
> may look like this:
>
> void reattach(Persistent object) {
> // force "modified" on the object
> object.setPersistenceState(PersistenceState.MODIFIED);
> context.localObject(object.getObjectId(), object);
> }
>
> This will do the right thing for objects not changed, but WILL NOT do the
> right thing for the newly inserted objects.
>
> Andrus
>
>
>
> On Nov 29, 2007, at 1:33 PM, Detlef Burt wrote:
>
> Hello,
> >
> > after being able to keep my Data after sending my Objects via JMS
> > (Thanks Andrus) I now have a problem when I try to write the Objects back
> > into the Database.
> >
> > After sending the Objects to the Client-Application, the Client changes
> > some data ( Just a timestamp in my Testcase ) and then sends an
> > Update-Request to the Server. Due to the fact, that the Client has no access
> > to the DataContext or the underlying ObjectStore, the changes made to the
> > Object won't be recorded.
> > After the Server receives the Object, it reconnects the Object to the
> > DataContext, thus being able to get a snapshot from the database or even
> > create an UpdateQuery.
> > But I can't go anywhere from here.
> > Executing the UpdateQuery won't have any effect because Cayenne doesn't
> > know what changed.
> >
> > I also tried to get a Snapshot from the DB, convert my DataObject to a
> > DataRow and then create and register the diff of those by myself. But I
> > couldn't find anything like that :/
> >
> > To sum it all up:
> > - Can I tell Cayenne to replace the Database Contents with the data from
> > my Object while retaining the ObjectId ?
> > - Can I tell Cayenne to "scan" an Object for changes and register the
> > differences, so that calling commitChanges will update the Object?
> > - Or is it possible to create a DataRow from a DataObject so I can
> > create and register an ObjectDiff ?
> >
> > NOTE:
> > When updating the Object, I don't know what class is being updated and
> > what properties it has, all I have is my CayennePersistableObject Baseclass,
> > which extends CayenneDataObject.
> >
> > Detlef
> >
> >
> >
>
Re: Replace Objects in a Database?
Posted by Andrus Adamchik <an...@objectstyle.org>.
In the nearest future we'll be adding a "merge" method to the
DataContext that would do exactly what you described here - reattach
an already persistent and possibly modified object to the context. For
now the closest analog is "localObject", but it will require some
hacking. A reattach method may look like this:
void reattach(Persistent object) {
// force "modified" on the object
object.setPersistenceState(PersistenceState.MODIFIED);
context.localObject(object.getObjectId(), object);
}
This will do the right thing for objects not changed, but WILL NOT do
the right thing for the newly inserted objects.
Andrus
On Nov 29, 2007, at 1:33 PM, Detlef Burt wrote:
> Hello,
>
> after being able to keep my Data after sending my Objects via JMS
> (Thanks Andrus) I now have a problem when I try to write the Objects
> back into the Database.
>
> After sending the Objects to the Client-Application, the Client
> changes some data ( Just a timestamp in my Testcase ) and then sends
> an Update-Request to the Server. Due to the fact, that the Client
> has no access to the DataContext or the underlying ObjectStore, the
> changes made to the Object won't be recorded.
> After the Server receives the Object, it reconnects the Object to
> the DataContext, thus being able to get a snapshot from the database
> or even create an UpdateQuery.
> But I can't go anywhere from here.
> Executing the UpdateQuery won't have any effect because Cayenne
> doesn't know what changed.
>
> I also tried to get a Snapshot from the DB, convert my DataObject to
> a DataRow and then create and register the diff of those by myself.
> But I couldn't find anything like that :/
>
> To sum it all up:
> - Can I tell Cayenne to replace the Database Contents with the data
> from my Object while retaining the ObjectId ?
> - Can I tell Cayenne to "scan" an Object for changes and register
> the differences, so that calling commitChanges will update the Object?
> - Or is it possible to create a DataRow from a DataObject so I can
> create and register an ObjectDiff ?
>
> NOTE:
> When updating the Object, I don't know what class is being updated
> and what properties it has, all I have is my
> CayennePersistableObject Baseclass, which extends CayenneDataObject.
>
> Detlef
>
>