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From "Karr, David" <david.k...@wamu.net>
Subject RE: Struts EL tag library stability
Date Fri, 23 Jul 2004 16:08:18 GMT
As the implementor of struts-el, and not specifically a user of it, I
can't comment from the POV of a user, but I can clarify some of the
goals of this library, which I think you may have missed.

I implemented struts-el when I saw the need for a "bridge" between
Struts on JSP 1.2 containers and the upcoming JSP 2.0 containers,
concerning use of the JSTL specifically.  Struts-el is intended to be
used in a JSP 1.2 container.  It is not used in a JSP 2.0 container.
So, to address one of your questions, Struts-EL will certainly NOT
become part of the core Struts tag library, as there's no point to it.
The greatest accomplishment of the struts-el library will be when no one
needs it anymore.

I've struggled with the fact that I don't have very much documentation
for Struts-EL, but the important thing to realize is that it's just a
pairing of the Struts tag library with the JSTL EL (not the JSTL).  In
fact, virtually the entire tag library could technically be generated.
Any tags that are implemented in Struts-EL exactly mirror the interface
of the tag in the base tag library (except for two attributes I thought
were very convenient in two tags), mostly because all of the tag classes
in Struts-EL simply inherit from the corresponding class in the base
library, but just pass the parameters through the JSTL EL.

With respect to calling setters of the tags, as Martin Cooper alludes
to, it's important to understand the perspective of why this is
happening.

> -----Original Message-----
> From: Martin Shiveral [mailto:martin_shiverallit@hotmail.com] 
> 
> The purpose of this email is to try and get an idea of the 
> number of users 
> in the struts community currently using the Struts EL tag library and 
> determine if the library is a sensible candidate for use 
> (i.e. whether it 
> will become a fully fledged part of the core Struts tag 
> library as opposed 
> to a contribution and what the level of developer support is 
> likely to be).
> 
> The Struts EL tag library (see 
> http://struts.apache.org/faqs/struts-el.html) 
> is an 
> extension of the Struts tag library that supports expression language 
> attribute values instead of the conventional 
> runtime-expression values. This 
> tag functionalty would prove useful for the project I am 
> involved with but 
> there is not a great deal of Struts-EL documentation 
> available online. The 
> Struts 1.1 source download does contain some doumentation but 
> I find it a 
> worrying sign that the API for these tags is not available 
> online (to my 
> knowledge).
> 
> For the most part we wish to take tags that generate standard 
> HTML elements 
> (button, text, textarea etc.) that support EL attribute 
> values and customise 
> them by wrapping additional elements around the underlying 
> functionality. I 
> have also read in numerous places (most notably the Jakarta 
> Taglib Developer 
> Guideline) that "user code should avoid calling a setter 
> method of a tag 
> handler for properties that correspond to tag attributes". 
> The Struts-EL 
> taglib source seems to break this rule by calling setter 
> methods from within 
> the "evaluateExpressions() private method of each tag, which makes me 
> slightly wary of them.
> 
> Has anyone else extended these tags or encountered any 
> problems with them?
> 
> Best Regards,
> Martin
> 
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