Re: Invalidating objects asynchronously
Re: Invalidating objects asynchronously
- Subject: Re: Invalidating objects asynchronously
- From: Peter Vandoros <email@hidden>
- Date: Tue, 9 Sep 2008 10:59:49 +1000
Yes, but he could link to WOnder or copy that delegate :-)
On 09/09/2008, at 10:56 AM, Chuck Hill wrote:
Yes. But he is not using Wonder. :-)
On Sep 8, 2008, at 5:44 PM, Peter Vandoros wrote:
I think there is a EODatabaseContext Delegate in WOnder (i think
ERXDatabaseContextDelegate) that will return null (or throw an
exception, i can't remember) in such cases instead of a dummy fault.
Regards
Peter
On 09/09/2008, at 10:32 AM, Chuck Hill wrote:
On Sep 8, 2008, at 5:26 PM, Mike Schrag wrote:
Do you mean that attributes of the EO are suddenly null? I
don't see how this is possible _unless_ you are looking at
objects that are in an EOEditingContext that is not locked.
That won't ever work reliably.
I'm assuming the root problem here is the old JMS stuff would
invalidate objects, which means you end up in a very unreliable
state. But I wasn't digging too much into it.
Hmmm, maybe if that happened before willRead() was called, this
might still happen. But after the fault is fired, the attribute
values should be stable if the EC is locked as it queues the
notifications rather than responding to them. So, to be sure you
had a real, live object, you could:
eo.willRead();
if ( ! eo.isDummyFaultEO(eo) ) {
// process
}
/**
* Detecting WO 5 dummy fault EOs. The code below is a
translation of code posted here:
* From http://wodeveloper.com/omniLists/eof/2001/November/msg00023.html
*
* As of WO4.5, EOF resolves faults for objects that don't exist
in the database to a dummy object with mostly empty attributes
(except those
that are set in -init), whereas earlier versions of EOF threw a
_fireFault exception. This method detects whether the receiver is
such a dummy object.
*
* A distinguishing feature of these dummy EOs is that they
don't have a corresponding database context snapshot, so we use
this to detect its dummy-ness. This seems more robust than
checking if all or most attributes are empty, since these can be
changed by client code.
*
* Dummy fault EOs should be removed from the editingContext
(using forgetObject) before it is invalidated
(invalidateAllObjects or invalidateObjectWithGlobalID), otherwise
an unrecoverable "decrementSnapshotCountForGlobalID - unable to
decrement snapshot count for object with global ID" exception is
thrown by EOF.<br><br>
*
* See also: http://www.omnigroup.com/mailman/archive/eof/2001-May/001988.html
andfollowing.
*/
public static boolean isDummyFaultEO(EOEnterpriseObject anObject)
{
/** require [valid_param] anObject != null; **/
JassAdditions.pre("EOObject", "isDummyFaultEO
[object_in_ec]", anObject.editingContext() != null);
JassAdditions.pre("EOObject", "isDummyFaultEO
[object_has_global_id]",
anObject.editingContext().globalIDForObject(anObject) != null);
boolean isDummyFaultEO = false;
// This method will fail if the object is still a fault. We
fire the fault so that the correct result is returned.
if (anObject.isFault())
{
anObject.willRead();
}
EOEditingContext ec = anObject.editingContext();
EOGlobalID globalID = ec.globalIDForObject(anObject);
// NB. objects with temporary globalIDs legitimately have no
DB snapshots, since these are by definition not yet saved to the
database.
if (! globalID.isTemporary())
{
// Find the EODatabaseContext instance associated with
anObject, or null if no databaseContext association can be found.
EOObjectStoreCoordinator rootStore =
(EOObjectStoreCoordinator)ec.rootObjectStore();
rootStore.lock();
try
{
EODatabaseContext dbContext =
(EODatabaseContext)rootStore.objectStoreForObject(anObject);
if (dbContext == null)
{
throw new RuntimeException("Could not locate
EODatabaseContext for object '" +
anObject + "' in
editingContext: " + ec);
}
isDummyFaultEO =
(dbContext.snapshotForGlobalID(globalID) == null);
}
finally
{
rootStore.unlock();
}
}
return isDummyFaultEO;
}
Chuck
--
Chuck Hill Senior Consultant / VP Development
Practical WebObjects - for developers who want to increase their
overall knowledge of WebObjects or who are trying to solve
specific problems.
http://www.global-village.net/products/practical_webobjects
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Chuck Hill Senior Consultant / VP Development
Practical WebObjects - for developers who want to increase their
overall knowledge of WebObjects or who are trying to solve specific
problems.
http://www.global-village.net/products/practical_webobjects
--
This message has been scanned for viruses and
dangerous content by MailScanner, and is
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Software Engineer
Etech Group Pty Ltd
Level 3/21 Victoria St
Melbourne VIC 3000
Australia
Ph: +61 3 9639 9677
Fax: +61 3 9639 9577
----------------------------------
IMPORTANT: This e-mail message and any attachments are confidential
and may be privileged. If received in error, please reply to this
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is limited to resupplying any affected message or attachments. For
more information about Etech Group, please visit us at http://www.etechgroup.com.au
.
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