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From "Ted Husted" <hus...@apache.org>
Subject Re: OpenSessionInView with Struts 2.x
Date Wed, 19 Dec 2007 00:08:18 GMT
There's a wiki page with some examples of accessing Hibernate (or JPA)
from an Action or an Interceptor.

 * http://struts.apache.org/2.x/docs/does-the-framework-integrate-with-hibernate.html

The interceptor case could be improved in a couple of ways. One way
might be to only handle the transaction if the Action implements an
"PersistenceAware" interface. The PersistenceAware interface might
include a boolean property that the Action could set if the
transaction should be rolled back.

-- HTH, Ted
 * <http://www.StrutsMentor.com/>


On Dec 18, 2007 2:04 PM, Alberto A. Flores <aaflores@gmail.com> wrote:
> Thank you everyone for all your input.
>
> I'm currently opting for changing my code (luckily is not that much) to
> never maintained a "persistent" object within the ValueStack, but rather
> a "transient" object. Of course, this is an additional overhead (have to
> copy the object, query, etc, etc), but I think is our best approach
> since Hibernate Validator is not viable option right now (I would also
> argue that validation could/should be pushed back to the model,
> unfortunately we are working with a poorly design db where we use
> reverse engineering to build all hbm and src files and I'm not sure if I
> have enough resources to fix that part of our build, e.g. add Hibernate
> Validator, modify templates, etc).
>
> If I may ask, how to "avoid the transaction commit when validation
> fails" (as you mentioned)?  Is there an interceptor to handle this
> scenario? I see that the workflow interceptor is part of the xwork
> package (not available with Struts2 distribution source code) and before
> I jump into repackaging one from xwork source (which I'm not even sure
> where can I find one), I would probably consider writing one myself to
> handle this case. I also notice that the validate() method is triggered
> before the prepare() method (which makes total sense), however I would
> like to guess that this scenario is best handled by an "interceptor" as
> I sensed such is the recommended approach in the documentation.
>
>
>
> Ted Husted wrote:
> > When a workflow automatically opens and closes a transaction, so that
> > it can cover multiple operations, and something goes wrong during the
> > course of the transaction, then we need to rollback the transaction.
> >
> > In the case of validation, sometimes changes are made to a property
> > which causes it to become (for example) NULL, and later in the
> > lifecycle the validator sees that the property is NULL, and raises the
> > validation error. But, by then, the property is changed, and the
> > Hibernate Session (or JPA EntityManager) will commit the change when
> > the transaction is automatically closed.
> >
> > Since the Hibernate Validator and JSR 299 push validation back to the
> > model (where it arguably belongs), making it easy to signal for a
> > rollback in a multioperation transaction becomes more important.
> >
> > I'm still ramping up on the JPA myself, but in some early tests I
> > found that not committing the transaction has the same affect of a
> > rollback.
> >
> > -- HTH, Ted
> >  * <http://www.StrutsMentor.com/>
> >
> > On Dec 17, 2007 4:04 PM, Alberto A. Flores <aaflores@gmail.com> wrote:
> >> Is anyone using openSessionInView with Struts 2 (Hibernate, Spring)?
> >>
> >> I've found a problem where a domain model is still persisted (even
> >> though I'm not saving it) after validation finishes (showing validation
> >> errors). My prepare method makes a query (using a
> >> HibernateTemplate().get() method) but that's all? Has anyone seen
> >> something similar?
> >>
> >> I'm very sorry if this is not a Struts2 question, but thought of asking
> >> since Struts2 is using Filters now and was wondering if anyone has seen
> >> any similar behavior.
> >>
> >> Thanks,
> >>
> >> --
> >>
> >> Alberto A. Flores
> >> http://www.linkedin.com/in/aflores

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