"`javascript' is not supported as a JSP scripting language."

I thought Resin was unique in that it supported server-side Javascript, 
(compiled to bytecode no less). I assumed that this could be enabled by 
a simple page declaration:

<%@ page language="javascript" contentType="text/html; 
charset=ISO-8859-1" pageEncoding="ISO-8859-1"%>

Is there some trick in getting this to work? I have to admit I was all 
excited to install Resin and get this working and was disappointed when 
I got a 500 error. I'm not looking forward to mashing Rhino into Resin. :(

http://www.caucho.com/articles/990129.xtp

refers to javascript, but if that article name is what I think it is, 
it's over 7 years old. Here's another reference that looks mighty aged:

http://www.caucho.com/articles/resin_js.xtp

This next one looks more hopeful (JavaDocs for 3.0.13):

http://www.caucho.com/resin-javadoc/resin//com/caucho/es/package-summary.html

(from google => javascript site:www.caucho.com)

Thanks,
Josh

P.S. Am I the only one who thinks that it makes sense to use the same 
javascript for doing form validation on the server as on the client?