code: function wrapHandler(fn) {
      return function (req, res, next) {
          // 防止重入
          if (req._routed) {
              return next();
          }
  
          req._routed = true;
          var query = extend({}, req.params, req.query);
          fn(req.path, query, res, next);
      };
  }
docs: 封装路由处理函数
  
  @inner
  @param {Function} fn 实际的路由处理函数
  @return {Function}