I want to authenticate a user using the zm_auth_token that I dispose :

For the moment, I'm doing this :

Code:
            LmcAuthRequest auth = new LmcAuthRequest();
            auth.setUsername(userName);
            auth.setPassword(password);
            LmcAuthResponse authResp = (LmcAuthResponse) auth.invoke(serverURL);
            LmcSession session = authResp.getSession();
But I want to use the zm_auth_token that I have. How to do this ???
Thnx