apollo-client/src/main/java/com/ctrip/framework/apollo/spring/config/PropertySourcesProcessor.java/PropertySourcesProcessor/initializeAutoUpdatePropertiesFeature
class PropertySourcesProcessor:  private void initializeAutoUpdatePropertiesFeature(ConfigurableListableBeanFactory beanFactory) {
    if (!configUtil.isAutoUpdateInjectedSpringPropertiesEnabled() ||
        !AUTO_UPDATE_INITIALIZED_BEAN_FACTORIES.add(beanFactory)) {
      return;
    }

    AutoUpdateConfigChangeListener autoUpdateConfigChangeListener = new AutoUpdateConfigChangeListener(
        environment, beanFactory);

    List<ConfigPropertySource> configPropertySources = configPropertySourceFactory.getAllConfigPropertySources();
    for (ConfigPropertySource configPropertySource : configPropertySources) {
      configPropertySource.addChangeListener(autoUpdateConfigChangeListener);
    }
  }