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From Gabriel Belingueres <>
Subject Re: Struts2 Conversation/OptimisticLockException Handling
Date Sat, 16 Nov 2013 02:47:43 GMT
Hi Chris.

One alternative is to use CDI which supports conversation scope too (I know
there is a CDI plugin. I never used though). Last time I checked the spring-
webflow integration was pretty outdated (it did not integrate with version
2.x). Another alternative is to go use JBoss Seam.

I made myself a conversation plugin which used successfully in some small
projects (I promised myself to publish the code sometime...I need to polish
it a little and translate it to english first). The great thing about
conversations is that you get almost for free the "extended persistent
context", that is the entity manager itself is stored inside the current
conversation along with your domain object (which remain attached to this
persistent context) and then you just use your forms without rewriting the
version number. Before the conversation ends, the entity manager is flushed
and a version conflict can be detected.


2013/11/15 CRANFORD, CHRIS <>

> Recently I was looking at a particular pattern we used and noticed that it
> exposed a bit of risk.
> In the past we generally queried our domain object, showed the user the
> form where they could maintain the record and within a hidden field, we
> maintained the version of that record.  During the submission, the database
> record was queried again, the changes applied to the entity, including the
> version from the form.  Should another user had modified the same record in
> between this session's save, naturally a collision would have been detected
> by the JPA framework.
> It was suggested that rather than expose the version and reset it during
> the submission phase, why not just cache the original fetched object, set
> the values on that object during save and persist the saved object when the
> time occurs.  To do this, there has to be some link between the cached
> version of the object and the requests, hence some conversation framework.
> I stumbled across struts2-conversation plugin that seems to offer this
> functionality and I know of spring-webflow.
> Are there other alternatives anyone has used?  Anyone have experiences
> they can share regarding the struts2-conversation plugin or integrating
> spring-webflow with Struts2?  Or have you simply just exposed the version
> in your forms and resent it back with every on submit, finding your domain
> object, detaching it, making changes (including setting your version), and
> the merging it back to be able to catch OptimisticLockException exceptions
> during database collisions?

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