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From: Andrus Adamchik <andrus@objectstyle.org>
Subject: Re: Nested data context problems
Date: Thu, 9 Nov 2006 17:24:38 -0500
To: cayenne-user@incubator.apache.org

I don't think I fully follow the sequence of events here, so my  
comments are a bit random...

> 3. I commit it on the first page,  so it goes to the database -  
> here i can see sql updates but also indication of event i think is  
> used for cache synchronisation
> DataRowStore [DEBUG] postSnapshotsChangeEvent: [SnapshotEvent]  
> source: org.objectstyle.cayenne.access.DataRowStore@ca8f43,  
> modified 1 id(s)

This message is only related to synching between peer DataContexts at  
the top level, so it is benign.

> 4. I go to the second page and it gets rendered with current  
> (modified) version of dataobjects
>     - when i debug converting of dataobjects to strings i notice  
> that my dataobject is in the same, new, state as i would expect, i  
> get the expected data with
>         DataObjectUtils.objectForPK(object.getDataContext(),  
> "Object", DataObjectUtils.pkForObject(object))

This looks suspicious. No objects should be in the "new" state after  
commit.

Andrus


On Nov 8, 2006, at 8:53 AM, Damir Bijuklic wrote:
> Hi,
>
> I'm playing around with nested data context's and tapestry.
> Using tapestry 4.1.1 and cayenne 1.2.1.
>
> I have encountered an issue with cayenne that i don't quite  
> understand. I will describe my setup and what I'm trying to do.
>
> I'm trying to use nested data context's on subforms/subpages.
> This way i can discard changes inside subforms although my  
> dataobject that is rendered on the form is updated (i either call  
> commitChangesToParent on nested data context, or i don't).
>
> I'm also using tapestry data squeezer, which is mechanism in  
> tapestry for converting from data object to string and vice versa.
>
> DataSqueezer has two methods that look similar to this: String  
> squeeze(Object) and Object unsqueeze(String) .
>
> In testing i have encountered an issue which i have tried to  
> reproduce with test case, but have not been able to do so, so far.
>
> When i navigate between three pages, each having it's own  
> datacontext, where top page uses session bound datacontext and  
> subpages use ones derived with
> createChildDataContext (so third page has datacontext that derives  
> from derived datacontext from second page).
>
> 1. I go to the third page,change some data and commit it
> 2. I commit it on the second page also
> 3. I commit it on the first page,  so it goes to the database -  
> here i can see sql updates but also indication of event i think is  
> used for cache synchronisation
> DataRowStore [DEBUG] postSnapshotsChangeEvent: [SnapshotEvent]  
> source: org.objectstyle.cayenne.access.DataRowStore@ca8f43,  
> modified 1 id(s)
> 4. I go to the second page and it gets rendered with current  
> (modified) version of dataobjects
>     - when i debug converting of dataobjects to strings i notice  
> that my dataobject is in the same, new, state as i would expect, i  
> get the expected data with
>         DataObjectUtils.objectForPK(object.getDataContext(),  
> "Object", DataObjectUtils.pkForObject(object))
>     - it gets converted to something like "Object:200" where Object  
> is entity name and 200 is PK
> 5. during the next request i try to parse string back into the  
> object, here the funny stuff happens:
>     - i parse "Object:200" and use DataObjectUtils.objectForPk 
> (dataContext, "Object", 200) to fetch the object
>     - i have checked few times that the datacontext i use here is  
> the same as one above
>     - the object i receive is NOT the one i have just rendered to  
> the string, it has it's properties changed to what they were before  
> step 1
>     - during this step i notice message in tho log
> DataRowStore [DEBUG] postSnapshotsChangeEvent: [SnapshotEvent]  
> source: org.objectstyle.cayenne.access.DataRowStore@ca8f43,  
> modified 1 id(s)
>      - tracing objectForPK shows that it reads the old values from  
> the cache though they should not be there and it seems they weret  
> there a few moments ago??
>
> I'm using shared cache, single jvm. What else could be wrong. If i  
> restart the app to reload the caches it's all ok. Also i would like  
> to load this object from the cache because it should have correct  
> values in it.
>
> Any ideas what I'm missing? Any further info i could post?
>
> Damir