Shawn Church wrote:
The problem with this is that it does not address the issue of
reattaching detached objects to the currently-open session. Since it is
natural in Tapestry to instantiate an object, use it in a page, and then
to persist the (potentially) changed object, the object must first be
reattached to the Hibernate session. Even if the object is not
persisted, if it contains lazy collection references it is necessary to
reattach the object in order for the collection to be properly initialized.
100% correct. That's why I'm also re-attaching those objects, though not
using a HibernateService, but explicit DAO calls.
Perhaps the 'best' solution is the one using custom DataSqueezers
http://wiki.apache.org/jakarta-tapestry/FrequentlyAskedQuestions/SpringHibernate
but i have yet to try it...
The only reliable solution I have found is to use Spring's
OpenSessionInView filter with singleSession=true, and then to explicitly
reattach objects in pageBeginRender(). I use a custom HibernateService
class which implements methods for attach(), evict(), and merge(). The
attach() method actually does a getSession().lock(object,
LockMode.NONE), but it handles NonUniqueObjectExceptions which will
commonly be thrown when using lazy collections if one of the collection
objects happens to already exist in the session.
Shawn
Quoting Andreas Andreou <[EMAIL PROTECTED]>:
Regarding to not using servlet filters for the OpenSessionInView
approach, I can confirm that other approaches work!
First of all,
i've always used the HibernateUtil class posted in hibernate forums
(and maybe also included in Hibernate in Action) that stores and
gets
session and transaction objects in thread local variables.
So, opening a hibernate session is never a problem (whichever method
first uses one, creates it) and so it only remains the issue of
closing it
somewhere.
I haven't tried the cleanupAfterRequest() of Engine approach.
Instead i've always extended the
pageEndRender(PageEvent event)
in a BasePage (that all my pages extend) and there I just do:
super.pageEndRender(event);
HibernateUtil.closeSession();
The nice thing is that this closeSession() never complains, no
matter
if no session is found, or if it has already been closed.
Anyway, I can post the HibernateUtil class here if you want to...
Andreas
Alejandro Scandroli wrote:
Henry Chen wrote:
I have been searching around desperately for solution of handling
lazy-loading database objects in tapestry. I configured
OpenSessionInViewFilter for Tapestry pages. It worked for some
cases
but not all. For example, in the table component, the first page
was
good, but when I selected other pages, it gave me the
LazyInitialization exception - owning session was closed. Is there
any
way around it now? Thanks a lot!
Hi , I'm having the same problem on Trails.
This quote may help.
quote form Open Session in View discussion on Hibernate site.
<quote>
Open Session pattern and Tapestry web framework
24 Mar 2004, 19:27 wassup
If you develop your application with Tapestry framework it is
better
do not use Servlet Filters to manage request cycle. More preferable
to
override setupForRequest() and cleanupAfterRequest() of Engine
class.
</quote>
I have no time to try this.
Please let me know if it works for you, or if you find another
workaround.
Saludos.
Alejandro.
PD:- please, excuse my English.
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