At 15:50 -0400 6/21/02, Shawn Bayern wrote: >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.)
Except that, for database programming, sometimes you *do* care very much. > >-- >Shawn Bayern >"JSTL in Action" http://www.jstlbook.com >(coming in July 2002 from Manning Publications) -- To unsubscribe, e-mail: <mailto:[EMAIL PROTECTED]> For additional commands, e-mail: <mailto:[EMAIL PROTECTED]>