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From "Patrick Linskey" <plins...@bea.com>
Subject RE: Merge Detached Entity Problem
Date Fri, 27 Apr 2007 22:19:24 GMT
That is an odd manifestation of the problem. Definitely worth
investigation.

-Patrick

-- 
Patrick Linskey
BEA Systems, Inc.
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> -----Original Message-----
> From: Jason Hanna [mailto:jason.m.hanna.at.coincident@gmail.com] 
> Sent: Friday, April 27, 2007 11:55 AM
> To: open-jpa-dev@incubator.apache.org
> Subject: Re: Merge Detached Entity Problem
> 
> An update - I was not using the @Version annotation in my 
> item definition. After updating my class with the annotation 
> and adding additional database column, my original reported 
> problem disappears.
> 
> My first read of the documentation led me to believe the 
> @Version annotation was a best practice, but not necessary.
> 
> From the OpenJPA User's Guide, Section 1.4:
> 
> ---start
> Note
> 
> OpenJPA fully supports version fields, but does not require 
> them for concurrency detection. OpenJPA can maintain 
> surrogate version values or use state comparisons to detect 
> concurrent modifications. See Section 7, " Additional JPA 
> Mappings " in the Reference Guide.
> 
> ---end
> 
> I seem to have resolved my immediate issue, but perhaps 
> someone can set me straight on the expected behavior when the 
> @Version annotation is not present.
> 
> Thanks,
> -jmh
> 
> 
> On 4/27/07, Jason Hanna <jason.m.hanna.at.coincident@gmail.com> wrote:
> > Hi All,
> >
> > I'm running into a problem developing a web application 
> that utilizes 
> > JSF and JPA. Not sure if my problem is related to an 
> OpenJPA bug, or a 
> > flaw in my approach. I'm hoping you can help.
> >
> > In my web application, a user selects an item to "edit" 
> from a table 
> > of all available items. They are then directed to a page 
> containing a 
> > form which allows them to modify the details of the item 
> they selected 
> > (pretty standard web app stuff).
> >
> > Upon submission, the backing bean connected to this form 
> invokes the 
> > update method of the item's data access object. The DAO in turn 
> > creates and EntityManager from the EntityManagerFactory, starts a 
> > transaction, merges the detached object, and commits the 
> transaction.
> >
> > If any value is modified on the item edit form, the 
> detached object is 
> > merged and successfully committed. That's good. Now for the problem:
> >
> > If the detached object is NOT modifed (edit form submitted w/o any
> > changes) the merge will fail on the EntityManager 
> transaction commit 
> > with the following error:
> >
> > <2|true|0.9.5-incubating>
> > org.apache.openjpa.persistence.RollbackException: 
> Optimistic locking 
> > errors were detected when flushing to the data store.  The 
> following 
> > objects may have been concurrently modified in another transaction:
> > [com.coincident.green.beans.User-com.coincident.green.beans.User-1]
> >
> > I've read through the lifecycle management documentation 
> and don't see 
> > why attempting to merge an unchanged detached entity would 
> result in 
> > an exception.
> >
> > I could probably detect that no updates were made at my JSF managed 
> > bean and avoid the merge operation altogether, but what 
> happens when 
> > my item references other managed entities and I want to utilize 
> > cascade merge?
> >
> > Hoping you all might have some thoughts. Here are a few 
> details about 
> > my environment:
> >
> > Sun JDK 1.5.0_06
> > Apache Tomcat 5.5.20
> > MyFaces 1.1.3
> > OpenJPA 0.9.5 (Packaged w/BEA Workship Studio and Kodo) 
> MySQL 5.0.27 
> > (Community)
> >
> > Thanks! Please let me know if you require any more information.
> >
> > Regards,
> > -jmh
> >
> > Jason M. Hanna
> > President/Founder
> > Coincident, Inc.
> >
> 

Notice:  This email message, together with any attachments, may contain information  of  BEA
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or entity named in this message. If you are not the intended recipient, and have received
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