node.js - Express 中嵌套路由的参数解析两次

Question

当我为下面的代码创建 GET http://localhost:8080/messages/3/sentiments 时，为什么 param 方法被调用两次？那么如果我有 10 条路线，它将被调用 10 次？

var comments = new Router();
comments.get('/comments', function (req, res, next) {
  res.send('Comments by message_id=' + req.message._id);
})

var sentiments = new Router();
sentiments.get('/sentiments', function (req, res, next) {
  res.send('Comments by message_id=' + req.message._id);
})

var messages = new Router();
messages.param('_message', function (req, res, next, _id) {
  console.log("Set message");
  fs.readFile(__filename, function () {
    req.message = { _id: _id };
    next();
  });
})

messages.use('/messages/:_message/', comments);
messages.use('/messages/:_message/', sentiments);

app.use(messages);
app.listen(8080);

Answer 1

已确认是 Express < 4.3 中的错误

https://github.com/visionmedia/express/issues/2121