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From Werner Punz <werner.p...@gmail.com>
Subject Myfaces 2.0 PPR ResponseWriter impl
Date Sat, 06 Jun 2009 08:38:17 GMT
Hello everyone

There are some corner cases which are not covered by our current 
implementation of the ppr response writer. (And neither by the RI as the 
comments from Salem seem to show)

I will give an example

PPR Response

It  usually starts with
startUpate on the ppr response writer

then the control tree is walked down and the controls are redrawn

and an endUpdate is offered

So what happens now is following

someone issues a startElement(script)

which means the script is embedded into the update code
while a separate eval cycle which would be possible is omitted!

We already have this covered in our javascript code by parsing the 
scripts, but I want to make a switch to have this turned off if 
performance is an issue. Nevertheless Javascript code should not be 
pushed into the html part of the ppr response anyway.

So here is my proposal and I am working on it already.

Scan for script startElement tags and postpone the rendering of those 
until the endUpdate or endInsert is issued!

Scan for script src and add some dynamic loading code to it (already 
finished in the javascripts)
and postpone it as well!

eval within an active update or insert also causes the same delay behavior!

if non update or insert is issued before then simply render script src 
as eval!

The advantage of all this is we can cover corner cases which can occur 
while not breaking downward compatibility. As far as I have understood 
the reported RI behavior, the component writers should be self aware of 
being in a PPR cycle but I am not sure how to render scripts from the 
component side without this behavior, I doubt this will work out without 
the added delaying behavior and pushing the scripts into the eval stage!
In our solution (which does the same as Trinidad mostly, btw, but in the 
jsf2 specific context) you dont have to care at all!

I have coded the needed ResponseWriterImpl extension class, but I am not 
finished with debugging, but I assume we should add the delaying 
behavior to cover those cases correctly!


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