code: function () {
  
      function getRider() {
        if (process.env.LIGHTSQLSERVER_HOST) {
          return sqlserverRider;
        }
        if (process.env.LIGHTMYSQL_HOST) {
          return mysqlRider;
        }
        return mongoRider;
      }
  
      // 遍历所有board，以class名注册类，并添加board方法
      this.board.forEach(item => {
        this[item.class] = this[item.class] || {};
  
        log.debug(`>>>> ${item.api} ${item.class} ${item.action} ${CONST.METHOD[item.type]}`);
  
        this[item.class][item.action] = (handler, params, callback) => {
  
          // params参数未指定
          if (typeof params === 'function') {
            callback = params;
            params = undefined;
          }
  
          // 添加参数
          handler = handler.copy(params || handler.params);
          handler.api = item;
  
          const func = getRider()[CONST.BOARD_TYPE[item.type]];
          if (func) {
            return func.call(this, handler, callback);
          }
  
          log.debug('no method. ' + item.class + '#' + item.action);
          callback(new error.class.MethodNotFoundError());
        };
      });
    }
docs: 根据board定义，创建访问类
  @returns {*}