code: function (handler, group, callback) {
  
      if (typeof group === 'function') {
        callback = group;
        group = undefined;
      }
  
      const validation = cache.get(constant.SYSTEM_DB_VALIDATOR).filter(item => {
        return item.group === (group || handler.req.path);
      });
  
      async.mapSeries(validation, (item, next) => {
  
        const func = rule[item.rule];
        if (func) {
          return func.call(this, handler, item, next);
        }
  
        log.debug('Rule does not define : ' + item.rule);
        next();
      }, (err, result) => {
        if (err) {
          return callback(err);
        }
  
        result = _.compact(_.flatten(result));
        if (_.isEmpty(result)) {
          return callback();
        }
  
        log.info(result);
        callback(new error.ParamError(), result);
      });
    }
docs: 校验
  @param handler
  @param group 可选 指定特定的校验组进行校验
  @param callback