code: @Override
    @SuppressWarnings("unchecked")
    public void stateChanged(AppSession source, Enum oldState, Enum newState) {
      logger.info("Diameter Rf SessionFactory :: stateChanged :: source[{}], oldState[{}], newState[{}]", new Object[] { source, oldState, newState });
    }
docs: /*
  (non-Javadoc)
  
  @see
  org.jdiameter.api.app.StateChangeListener#stateChanged(java.lang.Object,
  java.lang.Enum, java.lang.Enum)