http和express - 深度笔记

NoteDeep
const app = require('express')();
const server = require('http').Server(app);

上面这段的意思，
require('http').Server()  和 require('http').createServer() 的意义是一样的。都接收一个这样的函数作为参数
function(req, res)
而app = require('express')()  就正好是这样的函数

http.createServer的用法
var http=require("http");  
http.createServer(function(req,res){     
 res.writeHead(200,{         
 "content-type":"text/plain"     
 });     
 res.write("hello nodejs");     
 res.end(); 
}).listen(3000);
源码解读
 app = require('express')(); //infact, app is a requestListener function. 

var http = require('http').Server(app); // infact, function Server eqs http.createServer;

// infact,app.listen eqs http.listen 
other code from nodejs and express model

we can see, require("express")() return app is a function.

//express/lib/express.js   https://github.com/strongloop/express/blob/master/lib/express.js

var proto = require('./application');

exports = module.exports = createApplication;

function createApplication() {
  var app = function(req, res, next) {
    app.handle(req, res, next);
  };

  mixin(app, EventEmitter.prototype, false);
  mixin(app, proto, false);

  app.request = { __proto__: req, app: app };
  app.response = { __proto__: res, app: app };
  app.init();
  return app;
}
we can see, node.createServer eqs Server

//nodejs/lib/http.js  https://github.com/nodejs/node/blob/master/lib/http.js

exports.createServer = function(requestListener) {
  return new Server(requestListener);
};
we can see, express app.listen eqs http.listen

//express/lib/application.js  https://github.com/strongloop/express/blob/master/lib/application.js

app.listen = function listen() {
  var server = http.createServer(this);
  return server.listen.apply(server, arguments);
};


//nodejs/lib/_http_server.js  https://github.com/nodejs/node/blob/master/lib/_http_server.js
function Server(requestListener) {
  if (!(this instanceof Server)) return new Server(requestListener);
  net.Server.call(this, { allowHalfOpen: true });

  if (requestListener) {
    this.addListener('request', requestListener);
  }

  this.httpAllowHalfOpen = false;

  this.addListener('connection', connectionListener);

  this.addListener('clientError', function(err, conn) {
    conn.destroy(err);
  });


参考文档：
https://nodejs.org/api/http.html#http_class_http_server
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