----- Original Message -----
Sent: Wednesday, January 01, 2003 1:36
AM
Subject: [Tapestry-developer] Action vs.
Direct services
I'm still climbing the Tapestry learning curve.
My latest set of questions have centered around the action and direct
services. Simply, I understand the direct service very well (or at least think
I do). It makes total sense to me in a mode-less, multi-user, distributed web
application scenario. That is, because it encodes the state of things into the
service URLs themselves, things make sense to me.
For the life of me, however, I can't understand
why the action service would be a good idea. It seems totally broken to me and
fraught with danger. That is, the fact that you rewind a page and assume that
everything that was there when the page was first generated is still there now
seems just brittle and likely to fail. For instance, imagine a scenario where
a page is displaying rows out of a database, with links to operate on that
data. If I use the action service, I have to assume that the DB doesn't change
between the time I first rendered the page and when the user clicks a link.
That seems like a bad assumption in an environment where other users could be
adding, deleting, modifying, etc., at the same time, whether that happens 2
milliseconds ago or 10 minutes ago because the user went to grab a cup of java
(pun intended) after fetching the page and before submitting his
action.
So, given all this and the various statements in
the Tapestry tutorial generally suggesting that the direct service is higher
performance and generally more efficient, why would one ever use the action
service?
As a side question, why do the various action and
direct service components default to a stateful session? This seems the wrong
default to me. I'm finding myself overriding this behavior to avoid stale
session exceptions.
Thanks,
-- Dave
