code: private String getAuthenticationToken() {
  
          String token = request.getParameter("token");
          if (token != null && !token.isEmpty())
              return token;
          
          return null;
  
      }
docs: Returns the authentication token that is in use in the current session,
  if present, or null if otherwise.
  
  @return
  The authentication token for the current session, or null if no
  token is present.