Using AbstractAjaxBehavior.getCallbackUrl during page construction

[Pointbreak <po...@ml1.net>]

We have recently upgraded our application from Wicket 1.4 to Wicket 1.5.
One problem we encounter is with Ajax handlers we have that use
AbstractAjaxBehavior.getCallbackUrl to bind serverside code to actions
in the browser. I have been debugging this, and the problem seems to be
that the callback-url puts a renderCount parameter in the url that gets
created. That renderCount however is invalid if you call
AbstractAjaxBehavior.getCallbackUrl during page construction, because in
the render phase the renderCount will be incremented. Effect: a
StalePageException will allways be thrown for such behaviours, because
the renderCount of the behaviour is always invalid. The
StalePageException leads to a new instance of the page, but again with
the same problems for these Ajax behaviours. 

I can probably workaround this by either changing the code to not use
renderCount for these bahviours (not so nice), or to change the
behaviours to move the rendering of the urls from page-construction to
page-render (is going to be a big change).

My question is: why is renderCount of a page not coupled to the page
construction, instead of to the page render. I believe many wicket pages
use a pattern that initializes their state during constructions, instead
of during render, and this renderCount issue affects all these pages
when they use Ajax. Comments?

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Re: Using AbstractAjaxBehavior.getCallbackUrl during page construction

[Dan Retzlaff <dr...@gmail.com>]

I sympathize with your situation, but IMHO it's reasonable to
require AbstractAjaxBehavior#getCallbackUrl to happen during rendering. I'm
actually confused about how the behavior can get its URL during
construction, before it's associated with a page. I tried in quickstart and
it blew up with "No Page found for component".

Maybe getCallbackUrl should issue a warning if called outside render phase.
It's not obvious to me how it can determine this, though.

On Thu, Mar 22, 2012 at 3:55 AM, Pointbreak
<po...@ml1.net>wrote:

> We have recently upgraded our application from Wicket 1.4 to Wicket 1.5.
> One problem we encounter is with Ajax handlers we have that use
> AbstractAjaxBehavior.getCallbackUrl to bind serverside code to actions
> in the browser. I have been debugging this, and the problem seems to be
> that the callback-url puts a renderCount parameter in the url that gets
> created. That renderCount however is invalid if you call
> AbstractAjaxBehavior.getCallbackUrl during page construction, because in
> the render phase the renderCount will be incremented. Effect: a
> StalePageException will allways be thrown for such behaviours, because
> the renderCount of the behaviour is always invalid. The
> StalePageException leads to a new instance of the page, but again with
> the same problems for these Ajax behaviours.
>
> I can probably workaround this by either changing the code to not use
> renderCount for these bahviours (not so nice), or to change the
> behaviours to move the rendering of the urls from page-construction to
> page-render (is going to be a big change).
>
> My question is: why is renderCount of a page not coupled to the page
> construction, instead of to the page render. I believe many wicket pages
> use a pattern that initializes their state during constructions, instead
> of during render, and this renderCount issue affects all these pages
> when they use Ajax. Comments?
>
> ---------------------------------------------------------------------
> To unsubscribe, e-mail: users-unsubscribe@wicket.apache.org
> For additional commands, e-mail: users-help@wicket.apache.org
>
>