This pretty much confirms to me that there's a lack of a notification feature for parameter binding events. Seems pretty basic and would be easy to add. May I add that in a way that might make its way back into the code base?
Thanks, Ezra Epstein Amazon.com - Developer Tools 206-266-2259 -----Original Message----- From: Jesse Kuhnert [mailto:[EMAIL PROTECTED] Sent: Tuesday, October 10, 2006 1:09 PM To: Tapestry users Subject: Re: How to observe property binding events I'm not sure what the requirements are wrt properties and specific users. I've done similar things on a "per request" basis via doing something like: public abstract int getProp(); public abstract void setProp(int value); public int getComplicatedValue() { if(getProp() == -1) { // do something complicated setProp(newVal); } return getProp(); } The idea being that the heavy operation will only happen once for that request/response cycle. This all changes if you want it to be done for "all users" ? You can do that as well I suppose but I think I probably need more clarification on who the properties are supposed to be exposed to/etc.. On 10/10/06, Epstein, Ezra <[EMAIL PROTECTED]> wrote: > > That's the opposite of the functionality I want. These are not PER > request. They are per instance of a component. Thus true instance > variables are the way to go. Tapestry recycles Components and it seems > that within a request the same component is re-used but not cleared > (ivars reset) even though it is re-parametrized. So, I don't think > request vars would work. > > Thanks, > > Ezra Epstein > Amazon.com - Developer Tools > 206-266-2259 > > > -----Original Message----- > From: andyhot [mailto:[EMAIL PROTECTED] > Sent: Tuesday, October 10, 2006 12:35 AM > To: Tapestry users > Subject: Re: How to observe property binding events > > Why store them in local variables? > Store it in the current request cycle... > First do a cycle.getAttribute("myexpensivevar") if that returns null, > do the computations and store the result back cycle.setAttribute > ("myexpensivevar",obj); > > See > > http://tapestry.apache.org/tapestry4/tapestry/apidocs/org/apache/tapes > try/IRequestCycle.html > > > Epstein, Ezra wrote: > > OK, let's get to brass tacks. > > > > I have some derived values that are somewhat expensive to compute so > > I > compute them once per request/response cycle and then they're in local > instance variables (non-persisted). > > > > The particular component in question (with the semi-expensive > > derived > values) is used inside a loop and so may appear multiple times on a > page. By default the first time I use the component I compute the > value and then display from that computed value... The 2nd, 3rd, etc > instance of those component on the page is actually the exact same > Java instance and so the computed/derived ivar is still set. I've > added a hack that records an original property value when the derived > ivar is computed and if the original and current property values don't > match I reset the derived ivar. It works, but it a total hack. > > > > The common way I'd imagine doing it is to listen to when the > > property > (parameter) is set by Tapestry. But now that I've lain out the use > case maybe some knows the "right" way to do this in Tapestry. > > > > > > Thanks, > > > > Ezra Epstein > > > > > > -----Original Message----- > > From: Jesse Kuhnert [mailto:[EMAIL PROTECTED] > > Sent: Monday, October 09, 2006 3:33 PM > > To: Tapestry users > > Subject: Re: How to observe property binding events > > > > 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 > > > > -------------------------------------------------------------------- > > - To unsubscribe, e-mail: [EMAIL PROTECTED] > > For additional commands, e-mail: [EMAIL PROTECTED] > > > > > > > > > > > -- > Andreas Andreou - [EMAIL PROTECTED] - http://andyhot.di.uoa.gr > Tapestry / Tacos developer Open Source / J2EE Consulting > > > --------------------------------------------------------------------- > To unsubscribe, e-mail: [EMAIL PROTECTED] > For additional commands, e-mail: [EMAIL PROTECTED] > > --------------------------------------------------------------------- > 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 --------------------------------------------------------------------- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
