环境:express+sequelize 代码的意图是统一处理router中的异常，想当然的写了段try/catch,

var m = ['get','post','put','delete'];
m.forEach(function(type){
  var handlers = app.routes[type];
  if(handlers){
    handlers.forEach(function(handler){
      //TODO:need to config the excluded handler path,not the hard code. 
      if(handler.path !== '/' && handler.path !== '/auth'){//the '/auth' is the login url.
        handler.callbacks = [authIdentity].concat(handler.callbacks);
      }
      handler.callbacks.forEach(function(callback){
        var packageCallBack = function(req,res,next){
          try{callback(req,res,next);}
          catch(e){
            debugger;
            //TODO:need to implement other logics.  
            if(e instanceof AppError){
              res.send(e);
            }
            next(e);
          }
        };
        callback = packageCallBack;
      });
    });
  }
});

在处理请求的方法中，想当然的抛异常.

exports.authenticate= function(req, res, next){
  var daos = app.get('models')
    ,user = daos.user
    ,_vaule = {};
  user.find({where:{login:req.param('login')}}).success(
      function(value){
        if(value){
          var result = md5.validate(value.hashed_password,req.param('passwd'));
          if(result){
            req.session.userinfo = value.login;
            var url = req.param('url');
            if(url){
              res.redirect(url);
            }
          }else{
            throw new AppError('invalid user or passwd.');
            //next(new AppError('invalid user or passwd.'));
          }
        }
        else{
            throw new AppError('the user does not exist.');
          //next(new AppError('the user does not exist.'));
        }
      });
};

期望就是抛出的异常,有外围的try/catch去捕获,相信很多初学者都会犯类似的错误,在异步回调的时空里，回调方法抛出异常，往往就是噩梦,因为回调方法里的异常,try有啥用?

个人有个不恰当的比喻: node就像是一根绳子，异步回调是无处不在的绳子节点，抛异常好比剪刀,一刀下去，绳子断了. 最终的处理方式,已经很明显了,使用express中的next去传递异常,而不是抛～ 这里强调一下，回调和异步回调不是同一个概念，这里有篇文章讲解了回调捕获异常和异步回调捕获异常的区别 http://www.html-js.com/archives/category/nodejs/page/2

下面几个链接讲述了node中异常处理的基本方式: http://snmaynard.com/2012/12/21/node-error-handling/ http://stackoverflow.com/questions/7151487/error-handling-principles-for-nodejs-express-apps http://stackoverflow.com/questions/7310521/node-js-best-practice-exception-handling