Should isRendered return 'false' on error?

[Ri...@mail.thomson.com]

Dear All,

Could I please confirm the logic of the following code from javax.faces.component.UIComponentBase...

    public boolean isRendered()
    {
        if (_rendered != null) return _rendered.booleanValue();
        ValueBinding vb = getValueBinding("rendered");
        Boolean v = vb != null ? (Boolean)vb.getValue(getFacesContext()) : null;
        return v != null ? v.booleanValue() : DEFAULT_RENDERED;
    }

...this code throws a very ugly Exception and halts page rendering if the value binding cannot be evaluated. However, shouldn't it instead catch the Exception and return false? Because I thought the logic of the EL was to degrade gracefully with 'reasonable defaults' (and 'false' is the default for a boolean)?

Of course, I could have gotten this completely wrong,

Thanks,

Richard.

Re: Should isRendered return 'false' on error?

[Simon Kitching <sk...@obsidium.com>]

Richard.Kennard@mail.thomson.com wrote:
> Dear All,
> 
> Could I please confirm the logic of the following code from javax.faces.component.UIComponentBase...
> 
>     public boolean isRendered()
>     {
>         if (_rendered != null) return _rendered.booleanValue();
>         ValueBinding vb = getValueBinding("rendered");
>         Boolean v = vb != null ? (Boolean)vb.getValue(getFacesContext()) : null;
>         return v != null ? v.booleanValue() : DEFAULT_RENDERED;
>     }
> 
> ...this code throws a very ugly Exception and halts page rendering if the value binding cannot be evaluated. However, shouldn't it instead catch the Exception and return false? Because I thought the logic of the EL was to degrade gracefully with 'reasonable defaults' (and 'false' is the default for a boolean)?

I'd be inclined to say no. When there is a bug in my program such that 
the binding I've provided can't be evaluated I don't want MyFaces to 
silently fail to render the component; I want an exception message so I 
can fix the problem. Of course applications should be configured so end 
users are routed to a nice error page rather than seeing the exception 
directly.

Under what situation could the binding fail, but the program continue to 
work correctly? Not too many I would have thought. For example, in an 
online tax form failing to render a component because of an application 
error could have *very* expensive consequences.

The spec might require certain behaviour here anyway, though I'm not sure.


Regards,

Simon