RE: [Springframework-developer] RE: Reworkings and new features

[<jue...@we...>]

Chris,

No doubt about that: I've been reluctant to add OpenSessionInView =
support to Spring for quite a while, as I don't want to offer to keep =
transactions open during view rendering - or even worse, to dispense =
with transactions altogether just to get lazy-loading in views.

But now, I consider our solution of keeping a non-transactional Session =
open as appropriate for the case where you simply don't care about data =
loading exceptions in the view: Such exceptions don't affect =
transactions anymore but "just" cause a broken view page if additional =
data can't be loaded - and that won't happen too often. Accepting that =
risk is a valid tradeoff for view-driven lazy loading.

Personally, I prefer appropriate initialization of the model in the =
controller too. The point is that we don't force users into a single =
choice anymore: It's up to them now. I consider this an important new =
feature that turns Spring's Hibernate support into a viable option for =
Hibernate users who prefer lazy-loading in views.

I believe that the tradeoff that our OpenSessionInView handling offers =
is as good as possible: After all, you can't have lazy loading in views =
without the drawback of risking broken views in case of exceptions. =
Ad-hoc solutions as typically seen with Hibernate, involving custom =
ThreadLocals and the like, are arguably worse choices than our =
out-of-the-box solution.

Juergen


-----Original Message-----
From: spr...@li...
[mailto:spr...@li...]On Behalf
Of Chris Nokleberg
Sent: Wednesday, December 10, 2003 8:18 PM
To: spr...@li...
Subject: [Springframework-developer] RE: Reworkings and new features


j=FCrgen h=F6ller [werk3AT] wrote:
> Essentially, this isn't different from normal business and data access
> code based on Spring: Fatal runtime exceptions like =
DataAccessException or
> TransactionExceptions should not be handled by application code but =
always
> be propagated to the surrounding transaction or data access template. =
I
> don't see why views are different in that respect, but maybe I just =
don't
> get the point...

It can lead to broken pages if the exception occurs after the view =
writes
enough to cause a flush of the underlying response buffer. Either you =
get
half a page with an appended stack trace or you have to do some tricks =
to
close all open tags and write out a meta tag to redirect.

For these reasons I agree it is better to avoid "open session in view" =
but
in practice it can be difficult to make sure all of the lazy-loading
objects in your model have been initialized.

Chris




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