Re: NullPointerException only after first call to batchFetchRelationship

Hi!

Thanks for answering!

I have multiple EOF stacks in two components in this application, but 
these components are not releated to the place I get this exception.



At 19:54 -0800 15-12-03, Chuck Hill wrote:
>Yeah, that was probably me on about locking.  ;-)
>
>Good catch on the original problem!  I couldn't figure out what was
>different at first then AAARAUGH - multiple EOF stacks.  How many times can
>one person forget the same thing?  EOModelGroup().defaultGroup() is not
>safe to use when there are multiple stacks.  I'm not using them in the app
>where I'm prefetching which would explain why I've not seen this bug yet.
>
>If anyone's interested, related to this problem with
>EOModelGroup.defaultGroup() are the methods:
>EOModelGroup.modelGroupForObjectStoreCoordinator(EOObjectStoreCoordinator)
>EOUtilities.modelGroup(EOEditingContext)
>EOUtilities.databaseContextForModelNamed(EOEditingContext, String)
>
>Kaj, do you have multiple EOF stacks?
>
>I've added a little code here with a twist on Lenny's implementation (just
>'cause I like to play with all the different ways from point A to point B
>in EOF):
>http://wodev.spearway.com/cgi-bin/WebObjects/WODev.woa/wa/Main?wikiPage=EODa
>tabaseContext.batchFetchRelationship
>
>
>Chuck
>
>
>At 09:45 PM 15/12/2003 -0500, Lenny Marks wrote:
>>Sorry, I'd gotten mixed up on which list this was from.
>>
>>On Monday, Dec 15, 2003, at 20:49 America/New_York, Lenny Marks wrote:
>>
>>>  I had tracked it down in my case, see if this helps you any.
>>>
>>>  http://www.omnigroup.com/mailman/archive/eof/2003-August/003393.html
>>
>>Of course the EOObjectStoreCoordinator should be manually locked and 
>>unlocked in the code from that posting. (As originally pointed out by 
>>Chuck if I remember correctly)
>>
>>-lenny
>>
>>EOObjectStoreCoordinator osc = 
>>(EOObjectStoreCoordinator)ec.rootObjectStore();
>>
>>osc.lock();
>>try {
>>      EODatabaseContext dbContext = (EODatabaseContext)
>>              osc.objectStoreForObject(this);
>>
>>      EOEntity correspondenceEntity =
>>              EOUtilities.entityNamed(ec, "CorrespondenceEvent");
>>
>>      EORelationship corrRelationship =
>>              correspondenceEntity.relationshipNamed("correspondence");
>>
>>       dbContext.batchFetchRelationship
>>              (corrRelationship, correspondenceEvents, ec);
>>} finally {
>>     osc.unlock();
>>}
>>
>>>
>>>  On Sunday, Dec 14, 2003, at 12:08 America/New_York, Kaj Hejer wrote:
>>>
>>>>  At 08:57 -0400 17-08-03, Lenny Marks wrote:
>>>>>  I have a direct action to render all information for a specified
>>>>>  'Manuscript' in our database. The rendering of this page traces deep 
>>>>>  into
>>>>>  the manuscript's relationships and was slow so I was attempting to 
>>>>>  use
>>>>>  EODatabaseContext.batchFetchRelationship to limit the hits to the
>>>>>  database. I added a method batchFetchManuscriptEvents(the root of 
>>>>>  the deep
>>>>>  relationships) to my Manuscript EOEnterpriseObject class. I was 
>>>>>  hoping
>>>>>  that the application could call this in anticipation of its 
>>>>>  particular
>>>>>  display needs. The method would batchFetch all the relationships so 
>>>>>  that
>>>>>  by the time the WOComponent was generating its response, all the
>>>>>  relationships would have already been faulted. This actually worked, 
>>>>>  but
>>>>>  only the first time the method is invoked on a Manuscript instance 
>>>>>  within
>>>>>  a single EOF stack. The first time I access the direct action for a
>>>>>  manuscript, it works, but if I hit reload I get the exception below.
>>>>>
>>>>>  Any clues would be greatly appreciated!
>>>>>
>>>>>  -Lenny Marks
>>>>>
>>>>>  <ManView>[2003-08-17 07:49:16 EDT] <Thread-6>
>>>>>  java.lang.NullPointerException
>>>>>          at
>>>>>  com.webobjects.eocontrol._EOMutableKnownKeyDictionary.<init>(_EOMutab
>>>>>  leKnownKeyDictionary.java:90)
>>>>>          at
>>>>>  com.webobjects.eoaccess.EORelationship._foreignKeyForSourceRow(EORela
>>>>>  tionship.java:1094)
>  >>>
>>>>
>>>>
>>>>
>>>>  Hi!
>>>>
>>>>  I now saw the same exception when using prefetching.
>>>>
>>>>  The stacktrace and the method where I get this exception can be found
>  >>> at http://folk.uio.no/kajh/tmp/wo20031214.txt
>>>>
>>>>  Has anybody else here seen this?
>>>>
>>>>  The ec I use here is a childEC of session.defaulteditingContext and 
>>>>  this childEC has been locked.
>>>>
>>>>  I have only managed to reproduced this issue two times while testing 
>>>>  this application for about an hour, so it seems that it does not 
>>>>  appear so very often.
>>>>
>>>>
>>>>  -Kaj :)
>>>
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>>>  http://www.omnigroup.com/mailman/listinfo/webobjects-dev
>>
>>_______________________________________________
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>>
>
>--
>
>Chuck Hill                                 [email protected]
>Global Village Consulting Inc.             http://www.global-village.net