return null;
final CallbackHandler callbackHandler = connectContext.getCallbackHandler();
if (callbackHandler == null)
return null;
final NameCallback usernameCallback = new NameCallback(USERNAME_PREFIX);
final ObjectCallback passwordCallback = new ObjectCallback();
callbackHandler.handle(new Callback[] {usernameCallback, passwordCallback});
username = usernameCallback.getName();
password = (String) passwordCallback.getObject();
return new UsernamePasswordCredentials(username, password);
}