code: public static boolean isAction(HttpServletRequest request, String action)
      {
          FlowController flowController = PageFlowUtils.getCurrentPageFlow(request);
  
          if (flowController != null) {
              if (action.endsWith(PageFlowConstants.ACTION_EXTENSION)) {
                  action = action.substring(0, action.length() - PageFlowConstants.ACTION_EXTENSION.length());
              }
  
              if (getActionMapping(request, flowController, action) != null) return true;
              FlowController globalApp = PageFlowUtils.getSharedFlow(InternalConstants.GLOBALAPP_CLASSNAME, request);
              return getActionMapping(request, globalApp, action) != null;
          }
  
          return true;
      }
docs: Determine whether a given URI is an Action.
  @param request the current HttpServletRequest.
  @param action  the URI to check.
  @return <code>true</code> if the action is defined in the current page flow
  or in a shared flow. Otherwise, return <code>false</code>.