code: @Override
      public Callback[] getRequiredCallbacks(CallbackHandler callbackHandler) throws IOException, UnsupportedCallbackException {
          Callback[] callbacks = new Callback[1];
          callbacks[0] = new WSX509CertificateChainCallback(null);
  
          callbackHandler.handle(callbacks);
          return callbacks;
      }
docs: Gets the required Callback objects needed by this login module.
  
  @param callbackHandler
  @return
  @throws IOException
  @throws UnsupportedCallbackException