On Tue, 23 Apr 2002, Morgan Delagrange wrote:
> > > I was just wondering while reading the
> > specification - how do I test
> > > on something being not empty?
> > >
> > > <c:if test="${!empty param.name}">
> > > You specified a name.
> > > </c:if>
> > >
> > > Is this correct?
> >
> > Sure - or
> >
> > ${not empty param.name}
>
> or ${param.name != null}
Careful with that, though. A parameter isn't guaranteed to be null if a
user didn't specify it; empty text boxes typically come through as empty
strings (""). So checks like
<c:if test="${param.name != null}">
You must specify a name
</c:if>
are prone to errors; you should use
<c:if test="${not empty param.name}">
instead.
Of course, "== null" and "!= null" are still useful when you want to check
specifically against Java null -- but this isn't usually what you want
with request parameters.
--
Shawn Bayern
"JSP Standard Tag Library" http://www.jstlbook.com
(coming this summer from Manning Publications)
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