docs: @Ok("json:full")
      @At("/api/purchase")
      public NutMap purchase(String userId, String commodityCode, int orderCount, boolean dofail) {
          try {
              businessService.purchase(userId, commodityCode, orderCount, dofail);
              return new NutMap("ok", true);
          }
          catch (Throwable e) {
              log.debug("purchase fail", e);
              return new NutMap("ok", false);
          }
      }