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From Shawn Bayern <>
Subject Re: How to pass parameters to method in c:if
Date Mon, 18 Mar 2002 20:26:47 GMT
On Mon, 18 Mar 2002, Dave Newton wrote:

> On Monday 18 March 2002 02:43 pm, you wrote:
> > > <c:if test="${securityBean.check(request, response) }">
> > The JSTL expression language does not support method invocations on
> > objects.  You'll currently need to use a custom tag library or scriptlet
> > code (with the former being recommended over the latter) if you want to
> > access arbitrary methods and pass arguments to them.
> So, from a non-current tag/etc. user does this mean that I'd either
> want a custom tag for All Things Like That (i.e., <c:ifsecurecheck
> ...>) or, perhaps more OOish, <c:ifcheck param=MyBean> and use
> reflection to call a common method for everything I'd ever want to
> .check?

Tags are a great mechanism for providing abstraction.  If you want a
facility to call arbitrary methods from within a JSP page, Java scriptlets
(<% %>) provide this already.  Scriplets' problems don't just stem from
their syntax; they tend to make pages harder to maintain because they
don't create any meaningful abstraction.

Tags do.  When you design tags, I simply recommend you choose the most
convenient abstraction for your users.

There's a theory in linguistic pragmatics (for actual human languages, not
CS languages) that suggests language is a tradeoff between laziness and
effectiveness; as a speaker, you want to be lazy, but as a listener, you
want the speaker to provide as much information as is necessary.  Since
everyone is both a speaker and a listener, languages end up being
balanced:  not too verbose or too clipped, on average.

Anyway, page authors and tag-library developers are in a similar
relationship.  For every environment, there's a particular level of
"verbosity" that's appropriate; one isn't necessarily better than others.  
JSTL works well with either approach; it encourages good design when
unambiguous, but otherwise tries to avoid preaching about how you must
design your applications.

Shawn Bayern
Author, "JSP Standard Tag Library"
(coming this summer from Manning Publications)

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