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Date: Thu, 8 Apr 2010 13:16:40 +0000 (UTC)
From: "Jakob Korherr (JIRA)" <dev@myfaces.apache.org>
To: dev@myfaces.apache.org
Subject: [jira] Commented: (MYFACES-2645) The view state is saved before
 encodeAll() is called on every UIViewParameter in an AJAX request
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Jakob Korherr commented on MYFACES-2645:
----------------------------------------

Hi Leo,

To your examples: I tested it with render=3D"@all" and also with execute=3D=
"@all", but it didn't work. And if you understand the background, you will =
know why it can't work that way.

To your question: Basically yes, but in the case of UIViewParameter it aims=
 to store the value in the state. You see, UIViewParameter takes the value =
of a URL parameter as input, but this value is only available for the first=
 (GET) request. Every following postback won't include the value as a reque=
st parameter. Thus we need some way to keep the value from the first reques=
t in the state and the spec tells us to use the submittedValue here. Using =
the submittedValue to store the original value in the state has one advanta=
ge and one disadvantage. The advantage is that in the following request we =
just have to ignore a null-value (don't invoke setSubmittedValue(null)) in =
decode() and we will get our old submittedValue from the state. The disadva=
ntage, however, is that we have to set the submittedValue before the state =
is generated, because after the conversions and validations have happend, t=
he submittedValue is set to null by the JSF-lifecycle. To accomplish this, =
the spec tells us to invoke setSubmittedValue(getStringValue(...)) in UIVie=
wParameter.encodeAll() and furthermore to invoke encodeAll() on every UIVie=
wParameter in the view in UIViewRoot.encodeEnd(), which works perfectly for=
 normal requests. For AJAX-requests, however, the state is generated before=
 UIViewRoot.encodeEnd() is invoked and so the changes of the submittedValue=
 of every UIViewParameter are lost. Thus I applied the code from UIViewRoot=
.encodeEnd() to PartialViewContextImpl.processPartialRendering() before the=
 state of an AJAX-request is generated to have the changes of the submitted=
Value available in the AJAX-state.

So you see my committed code is absolutely correct and should not be revert=
ed. I guess it was just not thought about the correct handling of UIViewPar=
ameters in AJAX-requests when this part of the spec and the javadoc were wr=
itten.

However I wrote an email to jsr-314-open about this, because I think there =
is a better way to solve the problem (see the patch), but we can't apply th=
is code now, because it breaks the spec.

> The view state is saved before encodeAll() is called on every UIViewParam=
eter in an AJAX request
> -------------------------------------------------------------------------=
-----------------------
>
>                 Key: MYFACES-2645
>                 URL: https://issues.apache.org/jira/browse/MYFACES-2645
>             Project: MyFaces Core
>          Issue Type: Bug
>          Components: JSR-314
>    Affects Versions: 2.0.0-beta-3
>            Reporter: Jakob Korherr
>            Assignee: Jakob Korherr
>         Attachments: MYFACES-2645-spec-proposal.patch
>
>
> UIViewParameter calls setSubmittedValue() in encodeAll() to store the cur=
rent value of the view parameter in the state as the submitted value (this =
helps UIViewParameter to restore its value on a postback). UIViewParameter.=
encodeAll() itself is called by UIViewRoot.encodeEnd() for every UIViewPara=
meter in the view.
> If the current request is an ajax-request, the view state is currently al=
ready generated in UIViewRoot.encodeChildren() (before UIViewRoot.encodeEnd=
()). At this time the submitted value for every UIViewParameter is null, be=
cause its encodeAll()-method was not called yet.
> Later, when UIViewRoot.encodeEnd() is called, UIViewParameter.encodeAll()=
 is called and it sets the submitted value correctly, but due to the fact t=
hat the state has already been generated, these changes are dropped.
> This causes the value of every UIViewParameter to be set to null in the n=
ext request, which will most likely end in validation problems with the req=
uired validator.
> The related thread to this issue from the mailing list can be found at: h=
ttp://www.junlu.com/list/43/611590.html

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