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From Shawn Bayern <bay...@essentially.net>
Subject Re: Addition to allow alternate ExpressionEvaluators
Date Sun, 19 Oct 2003 22:35:55 GMT
On Sun, 19 Oct 2003, Frederick N. Brier wrote:

> There is not a standard framework yet, and even if there was, creating a
> perfect, one size fits all, is a tall order.  Declaring the JSTL a
> standard, while preventing its integration with existing frameworks is
> putting the cart before the horse, and hamstrings its applicability.  I
> think a standard expression language is a good idea.  It just should not
> be - the only one.

One advantage of JSTL -- and of course JSP itself -- is that it can be
implemented differently by different vendors; this allows for
optimizations and other behind-the-scenes improvements by specific
vendors.  The text "${x}" -- in appropriate context -- has a meaning
defined by the JSTL standard; if you add hooks to one JSTL implementation
to alter this meaning, then pages that are based on such hooks will be
tied to the specific implementation you've modified.  For instance, your
page wouldn't be portable from the Standard Taglib (Jakarta Taglibs's
implementation of JSTL) to Resin's implementation or any other.

Moreover, JSTL -- and the expression language generally, as part of JSP
2.0 -- is aimed at page authors.  If you alter the meaning of "${x}", such
page authors will need to look beneath the surface of the page they're
writing to determine what's going on; one hypothesis of JSTL is that its
users might not even be aware of deployment descriptors.

I've never suggested that a single framework or language should be used to
the exclusion of all others.  The mechanism you propose for integrating
different frameworks, however, creates more problems than it addresses;
the language isn't the appropriate point of extension in JSTL.  I'd
suggest thinking in terms of back-end logic that exposes objects or custom
taglibs that interact with JSTL.  (I'm not particularly familiar with
WebWork -- and not even working in information technology anymore! -- so I
regret that I can't be more helpful in suggesting specific alternatives.)

Shawn


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