[jsr-314-open] Coercion in the EL

[Lincoln Baxter, III]

Just wanted to make sure I was clear. The reason why I am scared of
changing this in JSF is because I already experience problems when
mixing JSTL and JSF tags. For example, since I cannot figure out how
to register the new Fancy JEE6 EL with the servlet container, <c:if>
behaves differently than the <blah:tag rendered=""> attribute. I
haven't spent a lot of time figuring out why, but I've been avoiding
mixing them with composite components for certain.

The differences between JSF EL and JSTL EL behavior has already caught
me off guard, so there's another side to the principle of least
surprise that needs to be considered.

--Lincoln

On Sun, Oct 18, 2009 at 7:32 AM, Martin Marinschek
<mmarinschek at apache.org> wrote:
> Hi Lincoln,
>
> On 10/16/09, Lincoln Baxter, III <lincolnbaxter at gmail.com> wrote:
>> I'm concerned... what implications does this have? Why is this
>> something we should be fixing? This is a potentially dangerous thing
>> to be tampering with IMO.
>
> I think I explained why this is a problem - it is against the
> "principle of least suprise": I don't expect, if I pass a null into an
> EL expression in the managed-bean, to have a "false" coming out in the
> attribute in my component. I expect the component author to be able to
> pick a sensible default value if I pass null. Same with a string - I
> don't expect an empty string if I pass null.
>
> What happens now is that people are not passing nulls from EL
> expressions, instead picking a default value themselves. It is most
> certainly not a decent solution to place the burden of picking default
> values on the web-app developer...
>
> regards,
>
> Martin
>