There's also the org.apache.tapestry.event.ChangeObserver interface, though
this is currently only used by the services in tapestry.persist to observe
page property changes when they are being managed via a particular
persistence strategy. (like session/client/etc..)
~Maybe~ it's an oversight, and maybe not..I guess that depends on what/why
you are trying to do. You'll find that there is very little in the framework
that wasn't put there for an actual need, so adding in support for things
that no one has needed yet doesn't seem to fall in line with sound design.
(imho of course..)
If you can outline why you need this, and exactly what properties/conditions
you'd want to observe we might be able to work something out...A general
"anything" is harder to understand / design around.
There is no such thing as a "parameter" property listener because parameters
have no meaning in the context of something taking a parameter...There has
to be a source for that parameter value (usually a page ) somewhere.
On 10/9/06, Epstein, Ezra <[EMAIL PROTECTED]> wrote:
Hi Jesse,
Thanks for that reply.
If I read it correctly, it sounds, simply, like the framework is missing
this feature. It's a pretty common thing to ask for listener call-backs on
framework events. ("Listener" here in the generic sense rather than the way
tapestry uses the term for direct-link targets.) In short, this sounds like
a design over-sight. It's common when beans are bound to be able to receive
a call-back -- Hibernate, for example, offers this. So much of Tapestry
seems "automagic" I'm surprised that there's no way to register to be
informed of the events as they occur.
If Howard's reading this perhaps he has a better perspective that he may
offer.
Thanks,
Ezra Epstein
Amazon.com - Developer Tools
206-266-2259
-----Original Message-----
From: Jesse Kuhnert [mailto:[EMAIL PROTECTED]
Sent: Friday, October 06, 2006 7:22 PM
To: Tapestry users
Subject: Re: How to observe property binding events
Yes, but the usefulness of my answer largely depends on how
clever/efficient you are trying to be doing it.
Now, there is IBinding. The one object to bind them all ;)
If you work your way down the type hierarchy you'll find AbstractBinding,
which holds the method you care about most - "setObject". This will be
called by tapestry when managing all of the page properties "automagically"
for you.
Some of the magic happens in (for your exact case at least)
org.apache.tapestry.enhance.ParameterPropertyWorker.
The other half of the work happens in each specific binding implementation
that will handle these set/get object calls..(Like ognl bindings, etc..)
I'm not sure where you are going with this but I guess you could use the
hivemind chain of command service sort of configuration (like I did for
org.apache.tapestry.services.ComponentRenderWorker ) to generically call a
single interface method for a hivemind configuration point...Then you can
contribute as many workers into the chain you like if you decide that you
have more than one use for it.
Again...Not knowing what you are doing - and taking the exact parameters
given I'd probably extend and override the default ParameterPropertyWorker
(a hivemind service, so replacing it inline with what Tapestry does already
should be easy ) and just override whatever section of code I needed to in
that implementation to inject + call my service reference.
It may look a little complicated in there at first, but the whole
org.apache.tapestry.enhance package is filled with lots of different
enhancement works - and most of them inject a service into the object they
work on...So finding an easier to follow worker to reference before
modifying ParameterPropertyWorker might be easier.
Hope that helps.
On 10/6/06, Epstein, Ezra <[EMAIL PROTECTED]> wrote:
>
> I've got a component which accepts a parameter. I want to listen
> (receive a callback) when the parameter is set (bound). Does Tapestry
> provide such a facility?
>
> Thanks,
>
> Ezra Epstein
>
>
>
>
--
Jesse Kuhnert
Tapestry/Dojo/(and a dash of TestNG), team member/developer
Open source based consulting work centered around
dojo/tapestry/tacos/hivemind. http://blog.opencomponentry.com
---------------------------------------------------------------------
To unsubscribe, e-mail: [EMAIL PROTECTED]
For additional commands, e-mail: [EMAIL PROTECTED]
--
Jesse Kuhnert
Tapestry/Dojo/(and a dash of TestNG), team member/developer
Open source based consulting work centered around
dojo/tapestry/tacos/hivemind. http://blog.opencomponentry.com
