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From Martin Koci <martin.kocicak.k...@gmail.com>
Subject Re: [core] implicit object 'component' in rendered expression (myfaces and spec bug)
Date Wed, 25 May 2011 20:12:25 GMT
Hi,

there are such cases but not many of them: in myfaces code after quick
search I guess about 10 such cases. The "main" is in
UIComponentBase.encodeChildren and in RendererUtils.renderChild (well,
there was, but I removed it incorrectly as part of MYFACES-3126)


This affects all attributes of component, not only rendered. If renderer
encodes children, then must set up context if reads something from
child. Consider:
<a:tabbedPane>
 <a:navigationItem style="#{component.something eq 'b'}" />

if tabbedPaneRenderer iterates over children directly and reads 'style'
property, then it must guarantee that 'component' resolves to
navigationItem otherwise it is incosistent with situation, where
navigationItem encodes itself.

This will affects complex structures like dataTable and panelGrid, I
think.

Regards,

Kočičák
 
Blake Sullivan píše v St 25. 05. 2011 v 12:42 -0700:
> I suspect that there are many cases where parent components are looking 
> at rendered on their children before deciding to traverse into these 
> children.  If EL-binding rendered to the component is supported, then 
> the parent is either going to need to stop performing this optimization, 
> or it is going to have to ensure that the context is setup and torn down 
> around each call to isRendered.
> 
> -- Blake Sullivan
> 
> On 5/25/11 11:27 AM, Martin Koci wrote:
> > Hi,
> >
> > for spec I've created bug few days ago:
> > http://java.net/jira/browse/JAVASERVERFACES_SPEC_PUBLIC-1002
> >
> > but I didn't realize how deep impact this bug have: I did a training
> > about JSF implicit objects in our company and now practically every
> > coder uses #{component.something} :)
> >
> > For myfaces:
> > https://issues.apache.org/jira/browse/MYFACES-3157
> >
> >
> > Leonardo Uribe píše v St 25. 05. 2011 v 12:36 -0500:
> >> Hi
> >>
> >> I have seen that. The problem is in spec javadoc, the behavior for
> >> UIComponent.process*
> >> and encode* is clear about the ordering.
> >>
> >> In theory, pushComponentToEL should be called before any call to
> >> isRendered, but after
> >> isTransient. Look on MyFaces UIComponentBase.processRestoreState. It has this
> >>
> >>      public void processRestoreState(FacesContext context, Object state)
> >>      {
> >>          if (context == null)
> >>          {
> >>              throw new NullPointerException("context");
> >>          }
> >>
> >>          Object[] stateValues = (Object[]) state;
> >>
> >>          try
> >>          {
> >>              // Call
> >> UIComponent.pushComponentToEL(javax.faces.context.FacesContext,
> >> javax.faces.component.UIComponent)
> >>              pushComponentToEL(context, this);
> >>
> >>              // Call the restoreState() method of this component.
> >>              restoreState(context, stateValues[0]);
> >>
> >> The spec javadoc says the opposite, restoreState should be called "before"
> >> pushComponentToEL but in practice that breaks UIComponent.EventListenerWrapper.
> >> I reported the bug long time ago, but it wasn't fixed (I don't know why).
> >>
> >> This case is similar. This should be fixed on the spec, but I don't
> >> see a reason why we shouldn't commit that into myfaces code, because
> >> after all, nobody relies on the buggy behavior.
> >>
> >> I think we should open a new issue on the spec issue tracker:
> >>
> >> http://java.net/jira/browse/JAVASERVERFACES_SPEC_PUBLIC
> >>
> >> but fix it on myfaces code.
> >>
> >> regards,
> >>
> >> Leonardo Uribe
> >>
> >> 2011/5/25 Martin Koci<martin.kocicak.koci@gmail.com>:
> >>> Hi,
> >>>
> >>> <h:form>
> >>>         <h:panelGroup>
> >>>                 <h:inputText id="testId"
> >>>                 rendered="#{component.id eq 'testId'}"                 
                value="#{bean.value}" />
> >>>         </h:panelGroup>
> >>> </h:form>
> >>>
> >>> please notice the expression:
> >>>
> >>> rendered="#{component.id eq 'testId'}"
> >>>
> >>> that is clearly true.
> >>>
> >>> But that does not work as expected: inputText is rendered, but never
> >>> updates model value.
> >>>
> >>>
> >>> Problem 1.
> >>>
> >>> from specification, methods UIComponent.process* and encode*
> >>> 1) If the rendered property of this {@link UIComponent}
> >>> false, skip further processing
> >>> 2) Call {@link #pushComponentToEL}
> >>>
> >>> ->  #{component} resolves in rendered="#{}" to parent!
> >>>
> >>>
> >>> Problem 2.
> >>>
> >>> MyFaces implement that (pointless) requirement inconsistently: from
> >>> UIComponentBase.process*:
> >>>
> >>> (!isRendered())
> >>>   return;
> >>> pushComponentToEL(context, this)
> >>>
> >>> and from UIComponentBase.encodeBegin*
> >>>   pushComponentToEL(context, this);
> >>>   if (isRendered())
> >>>
> >>>
> >>> causes that example above renderes inputText, but never updates model.
> >>>
> >>> Problem 3.
> >>>
> >>> RendererUtils.renderChild(FacesContext, UIComponent):
> >>> in this method it is unappropriate to use following code:
> >>>
> >>> if (!child.isRendered()) {
> >>>             return;
> >>>         }
> >>> child.encodeBegin(facesContext);
> >>>
> >>> because:
> >>> 1) it does not take into account pushComponentToEL ( #{component}
> >>> resolves to parent)
> >>> 2) behaviour is incosistent with UIComponent.encodeBegin : you'll get
> >>> "random" rendering - depends if parent of component renders it's
> >>> children or not! For this case I've created MYFACES-3126, but I'll
> >>> reopen it now, because simple remove of 'if (!child.isRendered())' does
> >>> not solve that problem and causes another problem if component
> >>> getRendersChildren = false;
> >>>
> >>>
> >>> What do yout think about this problem?
> >>>
> >>>
> >>> Regards,
> >>>
> >>> Kočičák
> >>>
> >>>
> >>>
> >
> 
> 



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