为什么将app.get()放在express.js的正确位置很重要？

Question

我刚刚注意到了一些我没想到的东西.我一直试图"搞"它一段时间,但没有完全管理.它让我疯狂......

采用标准的Expressjs文件.我补充说:

/**
 * Module dependencies.
 */

var express = require('express')
  , routes = require('./routes')
  , http = require('http')
  , path = require('path');

var app = express();

app.configure(function(){
  app.set('port', process.env.PORT || 3000);
  app.set('views', __dirname + '/views');
  app.set('view engine', 'jade');
  app.use(express.favicon());
  app.use(express.logger('dev'));

  app.post( '/call/loginAnon', function(req,res, next){
    console.log("IN THE CALL! %j %j %j", req.path, req.body, req.headers );
    next();
  });

  app.use(express.bodyParser());
  app.use(express.methodOverride());
  app.use(app.router);
  app.use(express.static(path.join(__dirname, 'public')));
});

app.configure('development', function(){
  app.use(express.errorHandler());
});


app.get('/', routes.index);

http.createServer(app).listen(app.get('port'), function(){
  console.log("Express server listening on port " + app.get('port'));
});

我还在bodyParser.js中添加了一个调试行,以便我们知道它何时被调用.请注意/ call/loginAnon是在 bodyParser 之前定义的.这是结果:

IN THE CALL! "/call/loginAnon" undefined {"host":"localhost:3000","connection":"keep-alive","content-length":"30","origin":"http://localhost:3000","x-requested-with":"XMLHttpRequest","user-agent":"Mozilla/5.0 (X11; Linux i686) AppleWebKit/537.1 (KHTML, like Gecko) Chrome/21.0.1180.89 Safari/537.1","content-type":"application/json","accept":"application/javascript, application/json","referer":"http://localhost:3000/login","accept-encoding":"gzip,deflate,sdch","accept-language":"en-GB,en-US;q=0.8,en;q=0.6","accept-charset":"ISO-8859-1,utf-8;q=0.7,*;q=0.3","cookie":"sid=s%3ASI%2F9XFcpe2qFdQNrmsL8ihz8.MezqsOBJM%2FWX9BZOJ0za7F1d8UX6sNjmQZBhN3mqFVA"}

Headers IN BODYPARSER.js: /call/loginAnon {"host":"localhost:3000","connection":"keep-alive","content-length":"30","origin":"http://localhost:3000","x-requested-with":"XMLHttpRequest","user-agent":"Mozilla/5.0 (X11; Linux i686) AppleWebKit/537.1 (KHTML, like Gecko) Chrome/21.0.1180.89 Safari/537.1","content-type":"application/json","accept":"application/javascript, application/json","referer":"http://localhost:3000/login","accept-encoding":"gzip,deflate,sdch","accept-language":"en-GB,en-US;q=0.8,en;q=0.6","accept-charset":"ISO-8859-1,utf-8;q=0.7,*;q=0.3","cookie":"sid=s%3ASI%2F9XFcpe2qFdQNrmsL8ihz8.MezqsOBJM%2FWX9BZOJ0za7F1d8UX6sNjmQZBhN3mqFVA"}

IN THE CALL! "/call/loginAnon" {"login":"sd","password":"sd"} {"host":"localhost:3000","connection":"keep-alive","content-length":"30","origin":"http://localhost:3000","x-requested-with":"XMLHttpRequest","user-agent":"Mozilla/5.0 (X11; Linux i686) AppleWebKit/537.1 (KHTML, like Gecko) Chrome/21.0.1180.89 Safari/537.1","content-type":"application/json","accept":"application/javascript, application/json","referer":"http://localhost:3000/login","accept-encoding":"gzip,deflate,sdch","accept-language":"en-GB,en-US;q=0.8,en;q=0.6","accept-charset":"ISO-8859-1,utf-8;q=0.7,*;q=0.3","cookie":"sid=s%3ASI%2F9XFcpe2qFdQNrmsL8ihz8.MezqsOBJM%2FWX9BZOJ0za7F1d8UX6sNjmQZBhN3mqFVA"}

所以,我的回调最终被调用了两次 - 一次是在调用bodyparser之前(所以),之后req.body是null一次调用(req.body实际设置).

在bodyParser下面移动调用有所改善:

Headers IN BODYPARSER.js: /call/loginAnon {"host":"localhost:3000","connection":"keep-alive","content-length":"30","origin":"http://localhost:3000","x-requested-with":"XMLHttpRequest","user-agent":"Mozilla/5.0 (X11; Linux i686) AppleWebKit/537.1 (KHTML, like Gecko) Chrome/21.0.1180.89 Safari/537.1","content-type":"application/json","accept":"application/javascript, application/json","referer":"http://localhost:3000/login","accept-encoding":"gzip,deflate,sdch","accept-language":"en-GB,en-US;q=0.8,en;q=0.6","accept-charset":"ISO-8859-1,utf-8;q=0.7,*;q=0.3","cookie":"sid=s%3ASI%2F9XFcpe2qFdQNrmsL8ihz8.MezqsOBJM%2FWX9BZOJ0za7F1d8UX6sNjmQZBhN3mqFVA"}

IN THE CALL! "/call/loginAnon" {"login":"sd","password":"sd"} {"host":"localhost:3000","connection":"keep-alive","content-length":"30","origin":"http://localhost:3000","x-requested-with":"XMLHttpRequest","user-agent":"Mozilla/5.0 (X11; Linux i686) AppleWebKit/537.1 (KHTML, like Gecko) Chrome/21.0.1180.89 Safari/537.1","content-type":"application/json","accept":"application/javascript, application/json","referer":"http://localhost:3000/login","accept-encoding":"gzip,deflate,sdch","accept-language":"en-GB,en-US;q=0.8,en;q=0.6","accept-charset":"ISO-8859-1,utf-8;q=0.7,*;q=0.3","cookie":"sid=s%3ASI%2F9XFcpe2qFdQNrmsL8ihz8.MezqsOBJM%2FWX9BZOJ0za7F1d8UX6sNjmQZBhN3mqFVA"}

IN THE CALL! "/call/loginAnon" {"login":"sd","password":"sd"} {"host":"localhost:3000","connection":"keep-alive","content-length":"30","origin":"http://localhost:3000","x-requested-with":"XMLHttpRequest","user-agent":"Mozilla/5.0 (X11; Linux i686) AppleWebKit/537.1 (KHTML, like Gecko) Chrome/21.0.1180.89 Safari/537.1","content-type":"application/json","accept":"application/javascript, application/json","referer":"http://localhost:3000/login","accept-encoding":"gzip,deflate,sdch","accept-language":"en-GB,en-US;q=0.8,en;q=0.6","accept-charset":"ISO-8859-1,utf-8;q=0.7,*;q=0.3","cookie":"sid=s%3ASI%2F9XFcpe2qFdQNrmsL8ihz8.MezqsOBJM%2FWX9BZOJ0za7F1d8UX6sNjmQZBhN3mqFVA"}

仍然叫了两次.但是,至少这次它有req.body设置.

在app.configure结束时移动它实际上修复了所有这些:

Headers IN BODYPARSER.js: /call/loginAnon {"host":"localhost:3000","connection":"keep-alive","content-length":"30","origin":"http://localhost:3000","x-requested-with":"XMLHttpRequest","user-agent":"Mozilla/5.0 (X11; Linux i686) AppleWebKit/537.1 (KHTML, like Gecko) Chrome/21.0.1180.89 Safari/537.1","content-type":"application/json","accept":"application/javascript, application/json","referer":"http://localhost:3000/login","accept-encoding":"gzip,deflate,sdch","accept-language":"en-GB,en-US;q=0.8,en;q=0.6","accept-charset":"ISO-8859-1,utf-8;q=0.7,*;q=0.3","cookie":"sid=s%3ASI%2F9XFcpe2qFdQNrmsL8ihz8.MezqsOBJM%2FWX9BZOJ0za7F1d8UX6sNjmQZBhN3mqFVA"}

IN THE CALL! "/call/loginAnon" {"login":"sd","password":"sd"} {"host":"localhost:3000","connection":"keep-alive","content-length":"30","origin":"http://localhost:3000","x-requested-with":"XMLHttpRequest","user-agent":"Mozilla/5.0 (X11; Linux i686) AppleWebKit/537.1 (KHTML, like Gecko) Chrome/21.0.1180.89 Safari/537.1","content-type":"application/json","accept":"application/javascript, application/json","referer":"http://localhost:3000/login","accept-encoding":"gzip,deflate,sdch","accept-language":"en-GB,en-US;q=0.8,en;q=0.6","accept-charset":"ISO-8859-1,utf-8;q=0.7,*;q=0.3","cookie":"sid=s%3ASI%2F9XFcpe2qFdQNrmsL8ihz8.MezqsOBJM%2FWX9BZOJ0za7F1d8UX6sNjmQZBhN3mqFVA"}

这就是我一直以来所做的事情(也是大多数人一直以来所做过的事).我恰好在配置之前定义了一条路线并注意到了它的怪异.

我确信这是因为我没有正确理解expressJs在定义路线时的工作方式.但是......有人可以对此有所了解吗？

谢谢,

芝加哥商业交易所.

Answer 1

您多次访问路径的原因是您在app.router中间件之前定义了处理程序.

原因是中间件将按其定义的顺序使用,每个层都响应请求或将其发送到下一层.所以解释你的例子:

    // The handler is defined before the router so any request that passed the 
    // previous middleware will also be passed into this middleware
    // The method (GET or POST or..) or the path is irrelevant at this point
    app.post( '/call/loginAnon', function(req,res, next){
      // Will run every time
      console.log("IN THE CALL! %j %j %j", req.path, req.body, req.headers );
      next(); // It is sent to the next middleware layer
    });
    // Now the bodyParsel will parse the body and give you the req.body variable
    app.use(express.bodyParser()); 
    app.use(express.methodOverride());
    // This handler will now parse the path of the request and redirect it
    // to the defined handler which is why it is accessed the second time
    app.use(app.router);