setting the user agent header

[Marc Esher]

Greetings all. I'm using 1.4, call-style invocation (i.e. not generated with
wsdl2java) and am having trouble overriding the default axis user-agent
header. here's what i'm currently doing:

 Hashtable m = new Hashtable();
            m.put(HTTPConstants.HEADER_USER_AGENT, "Mozilla/5.0(blah blah
blah)");
            call.setProperty(HTTPConstants.REQUEST_HEADERS, m);


Problem is, this basically just doubles up the user agent header instead of
overwriting the existing header.

So... how does one override this header?

Thanks so much.

Marc