docs: public static synchronized void registerSystemPropertiesListener(PropertiesListener listener) {
  		Properties currentProperties = System.getProperties();
  
  		// 将System的properties实现替换为ListenableProperties
  		if (!(currentProperties instanceof ListenableProperties)) {
  			ListenableProperties newProperties = new ListenableProperties(currentProperties);
  			System.setProperties(newProperties);
  			currentProperties = newProperties;
  		}
  
  		((ListenableProperties) currentProperties).register(listener);
  	}