code: private boolean _isRedirectTrueOnPreviousRequest(FacesContext facesContext)
      {
          ExternalContext externalContext = facesContext.getExternalContext();
          Map<String, Object> requestMap = externalContext.getRequestMap();
          Boolean redirect = (Boolean) requestMap.get(FLASH_PREVIOUS_REQUEST_REDIRECT);
          
          return Boolean.TRUE.equals(redirect);
      }
docs: Return true if setRedirect(true) was called on the previous request.
  Precondition: doPrePhaseActions() must have been called on restore view phase.
  @param facesContext
  @return