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https://issues.apache.org/jira/browse/MYFACES-3596?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13440827#comment-13440827
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Leonardo Uribe commented on MYFACES-3596:
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I checked the patch and I was able to reproduce the problem, thanks for the
example.
I checked the implementation of FlowViewStateManager, and this class has JSF
1.1/1.2 in mind, so if you set javax.faces.PARTIAL_STATE_SAVING config param
to false, the code will work as expected.
The problem is caused because MyFaces has a very optimized algorithm in PSS,
that in some cases generates zero state per view. So, it is possible to set a
view as valid, but return null in the state.
In few words, FlowViewStateManager relies on the old behavior. To implement
Partial State Saving in JSF 2.0, some changes were done. After a lot of
investigation, the right thing to do it is provide a custom
org.apache.myfaces.application.StateCache, overriding it
org.apache.myfaces.renderkit.html.HtmlResponseStateManager . In that way, it is
possible to override the logic involved in store the state (in this case store
it into spring view scope). In this way, PSS logic is preserved.
This is not a MyFaces issue, instead it is a problem that should be solved from
Spring side. I'll close this issue as invalid, because it works with PSS
disabled, and we cannot do anything from MyFaces side. This problem will be
fixed in JSF 2.2, with the introduction of windowId concept, and the
integration of such logic into state saving algorithm.
> NPE exception is thrown during ajax requests from webflow
> ---------------------------------------------------------
>
> Key: MYFACES-3596
> URL: https://issues.apache.org/jira/browse/MYFACES-3596
> Project: MyFaces Core
> Issue Type: Bug
> Components: General
> Affects Versions: 2.1.8
> Environment: myfaces-2.1.8 + richfaces-4.2.2 + webflow-2.3.1
> Reporter: Anton Zukovskij
> Attachments: log.log, swf-rf4.zip
>
>
> When using a4j:commanButton from webflow rendered view NullPointerException
> is thrown during restoreState of component (state==null). Changing to mojarra
> implementation solves this problem, therefore it is myfaces integration
> issue. Please see sample webapp and logs attached.
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