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From "" <>
Subject Re: Setter not called for conditionally rendered fields
Date Tue, 05 Aug 2008 14:23:43 GMT schrieb:
> Hi,
> I keep running into a problem where the setter of a field (say/ Field 
> 1/) in my backing bean (in request scope) that is rendered 
> conditionally is not called.
> I think what happens is that Trinidad evaluates the rendered condition 
> to determine if the setter should be called. My backing bean is sort 
> of stateless and needs to be filled with data from the form.
> Because the condition depends on another field (/Field 2/) in the 
> backing bean, the outcome of this evaluation will only be correct if 
> the setter of Field 2 was already called, which may or may not be the 
> case. So for some fields it will work but for other it will not.
> How can I get around this?
It is standard behaviour for JSF components to evaluate their "rendered" 
expression, and NOT write to the "value" property if rendered is false. 
This is nothing to do with Trinidad.

If you have a view where the rendered property of a component depends 
upon the user-provided value of another field, then I don't think that 
is going to work. I wouldn't think it even depends on component order in 
the page; an EL expression uses only values that have already been 
pushed into the model, but a component uses the "rendered" state to 
determine whether to accept data from the posted form in an earlier 
phase, ie before any values are pushed to the model.

See specification/javadoc for methods UIComponent.decode and 

I can't think of any solution for this. And I don't really understand 
why you are trying to do this either. You are trying to switch the 
"rendered" state of a component in the middle of the postback phase. 
Why? JSF really expects the rendered state during postback to match the 
rendered state that existed during the earlier render phase.

As a side-point, does the JSF spec actually say that "rendered" EL 
expressions should be re-evaluated during postback? That's what MyFaces 
currently does, but it seems to me that the true/false state should 
really be part of the component's saved state and the restored value 
simply used during postback (and recalculated in render phase). That 
doesn't make any difference to the original question however.


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