code: @Override
      public void afterPropertiesSet() throws Exception {
          Assert.notNull(oAuth2ServiceProperties, "An oAuth2ServiceProperties must be set");
          Assert.notNull(oAuth2UserDetailsLoader, "An oAuth2UserDetailsLoader must be set");
          Assert.notNull(oAuth2UserInfoProvider, "An oAuth2UserInfoProvider must be set");
      }
docs: Invoked by a BeanFactory after it has set all bean properties supplied
  (and satisfied BeanFactoryAware and ApplicationContextAware).
  <p>This method allows the bean instance to perform initialization only
  possible when all bean properties have been set and to throw an
  exception in the event of misconfiguration.
  
  @throws Exception in the event of misconfiguration (such
  as failure to set an essential property) or if initialization fails.