express框架, 为什么会混合使用内置的 http(s) 模块？

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在nodejs的网站后端领域里面，express框架可能是入门必备的框架。单独的express就是可以运行的，但是，为啥有的例子里面，会出现和nodejs内置的http/https合用的场景呢？要知道，某种意义上来说，express和http模块解决的是同样的事情。

苏南大叔的“程序如此灵动”博客，记录苏南大叔的代码编程经验总结。测试环境：win10，nodejs@20.18.0，express@4.21.2。本文试图解决一个疑惑，有关express和http合用的合理性问题。

express单独用例

参考代码如下：

var express = require("express");
var app = express();
app.use(express.static('public'));
app.use((request, response, next) => {
    console.log(request.method + " " + request.url);
    next();
});
app.get("*", (request, response, next) => {
    response.end(request.url);
});
app.listen(80, function () { console.log('http://localhost:%s', this.address().port) });

本文并不是解释express的具体使用情况的，所以，更多使用方法可以参考下面的文章：

• https://newsn.net/say/express.html
• https://newsn.net/say/express-catch.html

http模块单独用例

var http = require("http");
var app = http.createServer(function (request, response) {
    console.log(request.method + " " + request.url);
    response.writeHead(200, { "Content-Type": "text/plain" });
    response.end(request.url);
});
app.listen(80, () => console.log('http://localhost:%s', app.address().port));

express和http模块合用例子

既生瑜何生亮？为啥两者要合用？那是因为：express框架本来就是基于http模块的，两者本身也没有太明显的竞争关系。

let express = require("express");
let _express = express();
_express.use(express.static('public'));
_express.use((request, response, next) => {
    console.log(request.method + " " + request.url);
    next();
});
_express.get("*", (request, response, next) => {
    response.end(request.url);
});
// _express.listen(80, function(){console.log('http://localhost:%s', this.address().port)});
let http = require("http");
let httpServer = http.createServer(_express);
httpServer.listen(80, () => console.log('http://localhost:%s', httpServer.address().port));

还可以开两个端口，

// ...
_express.listen(80, function(){console.log('http://localhost:%s', this.address().port)});
// ...
httpServer.listen(81, () => console.log('http://localhost:%s', httpServer.address().port));

本来express就可以.listen()，为啥非要使用http.createServer().listen()包装一下呢？

express源码

点开express.listen()到express的源码。就可以看到express官方推荐使用http或者https模块的注释。不过是个interface，通过关键字找到实现代码的话，就可以看到express.listen()的实现代码：

/**
 * Listen for connections.
 *
 * A node `http.Server` is returned, with this
 * application (which is a `Function`) as its
 * callback. If you wish to create both an HTTP
 * and HTTPS server you may do so with the "http"
 * and "https" modules as shown here:
 *
 *    var http = require('http')
 *      , https = require('https')
 *      , express = require('express')
 *      , app = express();
 *
 *    http.createServer(app).listen(80);
 *    https.createServer({ ... }, app).listen(443);
 *
 * @return {http.Server}
 * @public
 */

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

所以，你所疑惑的代码，其实只是一个变换的写法罢了。express的listen()方法，本来也调用的是http模块。那么，这样来说，两者的合用代码，就显得不那么奇怪了。

express 合用 http 和 https

新的监听三个端口的完整代码：

let express = require("express");
let _express = express();
_express.use(express.static('public'));
_express.use((request, response, next) => {
    console.log(request.method + " " + request.url);
    next();
});
_express.get("*", (request, response, next) => {
    response.end(request.url);
});
_express.listen(80, function () { console.log('http://localhost:%s', this.address().port) });
let http = require("http");
let httpServer = http.createServer(_express);
httpServer.listen(81, () => console.log('http://localhost:%s', httpServer.address().port));
let https = require('https');
let fs = require('fs');
let httpsServer = https.createServer({
    key: fs.readFileSync('./cert/cert-key.pem'),
    cert: fs.readFileSync('./cert/cert.pem')
}, _express);
httpsServer.listen(82, () => console.log('https://localhost:%s', httpsServer.address().port));

结语

所以，结论是：express和http模块的关系，并不是对立，而是amigo的关系。

• https://newsn.net/tag/express/

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