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From Michael Duffy <>
Subject RE: Populating One <select> Based On The Value In Another
Date Tue, 06 May 2003 16:47:32 GMT

I've got a front controller servlet that takes
requests, executes commands, puts results into the
request, and forwards them onto the next page.  The
next page can certainly do this:

<jsp:useBean id="something" class="java.util.Map"/>

Now I can access the map by writing:


If the Map has String keys and java.util.List values,
I can get the value and stuff it into a JSTL
<c:forEach> tag.

Actually , I haven't gone to ANY trouble yet because
I've just started on this effort.  ;)  It was just an
idea.  I thought that if there was a way to get the
value out of DHTML and into JSTL that I was ignorant
of I'd be glad to know it.

But the dearth of information has brought me to the
same conclusion that you're drawing: it's not
possible.  I'll just populate both drop-downs at the
same time.  Thanks. - MOD

--- Wendy Smoak <> wrote:
> Michael wrote:
> > Exactly.  It's a choice between doing it on the
> client
> > side or enduring another round-trip to the server.
>  I
> > know how to get it from the server, but I was
> hoping
> > that I could send a java.util.Map down when the
> page
> > is rendered and save myself a trip.
> All the Java/JSP/JSTL code executes on the server,
> so I don't see where you
> could "send" a Map down to the client side.  Maybe
> an applet?  You could
> surely render the *contents* of the Map into a
> JavaScript data structure.
> (Does JavaScript have a Map structure?) And then use
> client-side JavaScript
> to populate the second drop-down once the user has
> made a selection from the
> first.
> > But this is the first time I've had the problem of
> > populating one drop-down using the choice from
> > another.  I know how to get the selection from the
> > first box out of JavaScript.  Getting that value
> into
> > JSTL and the EL is the thing that I'm fuzzy on.
> It's one or the other.  Since JavaScript is
> client-side, and JSTL/EL is
> server-side, you can't get the value out of
> JavaScript and into JSTL.  If
> you want to save a trip to the server, then I don't
> believe JSTL will be of
> any help.
> How much of a load will this site be under?  Is an
> extra round trip to the
> server really that important?  You may be going to a
> lot of trouble to avoid
> something that isn't really going to be a problem.
> -- 
> Wendy Smoak
> Applications Systems Analyst, Sr.
> Arizona State University PA Information Resources
> Management

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