I suspect that is an internal class that is instantiated once the "WWW-Authenticate: NTLM" header is seen. Apparently you need to set up a subclass of
java.net.Authenticator to return the required authentication information (see
Http Authentication) and then set it as the default by calling
java.net.Authenticator.setDefault(myAuthenticator). Of course this will only work if your JAX-RPC implementation actually uses the
java.net.HttpURLConnection class.
Then again it may just be a matter of setting the correct properties as there is a
http.auth.ntlm.domain property (see
Networking Properties).