On Fri, 21 Jun 2002, John Hicks wrote:
> On Friday 21 June 2002 03:09 pm, you wrote:
> > > I finally traced this problem to undefined request
> > > parameter fields, specifically radio buttons and check
> > > boxes (i.e. whenever a check box was left unchecked or
> > > when the user didn't select any of a set of radio
> > > buttons).
> >
> > Actually, this looks like a bug in our implementation of
> > <sql:param>; a null 'value' should cause the
> > corresponding column to be set to SQL NULL.
>
> In my case, the response parameter is not defined at all.
> (Apparently this is an attribute of checkboxes in HTML forms.) Should
> an undefined attribute produce the same results as a defined attribute
> with a null value?
Yeah - there's no difference, formally in the Servlet API, between an
undefined parameter and a parameter with no value. That is, if
request.getParameter("foo") returns null, that means that the parameter
doesn't exist. Whether it doesn't exist because a browser didn't set it
or because it was never in a form isn't a detail that's accessible to a
servlet or JSP page.
Note that there *is* a difference between "" and null, which was the main
reason we introduced the 'empty' keyword. (That is, we wanted to provide
page authors with a way to combine the two cases, since most of the time,
you don't care whether a parameter is "" or null.)
--
Shawn Bayern
"JSTL in Action" http://www.jstlbook.com
(coming in July 2002 from Manning Publications)
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