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上一节实现 express 的请求处理，这一节来进行实现 express 的优化处理

1. 让 layer 提供 match 方法去匹配 pathname，方便拓展
2. 让 layer 提供 handle_request 方法，方便拓展
3. 利用第三方库 methods 批量生成方法
4. 性能优化问题
   • 进行路由懒加载，当进行 get/post... 请求时，或者 listen 时，才加载 route
   • layer 进行加速匹配，在 layer 层判断是否请求方法在 route 里有

methods 库地址：https://www.npmjs.com/package/methods

['acl',        'bind',        'checkout','connect',    'copy',        'delete','get',        'head',        'link','lock',       'm-search',    'merge','mkactivity', 'mkcalendar',  'mkcol','move',       'notify',      'options','patch',      'post',        'pri','propfind',   'proppatch',   'purge','put',        'rebind',      'report','search',     'source',      'subscribe','trace',      'unbind',      'unlink','unlock',     'unsubscribe'
]

批量生成方法测试 demo 如下

const express = require("./kaimo-express");
const app = express();app.get("/", (req, res, next) => {res.end("get okk end");
});
app.post("/", (req, res, next) => {res.end("post okk end");
});app.listen(3000, () => {console.log(`server start 3000`);console.log(`在线访问地址：http://localhost:3000/`);
});

控制台执行下面命令：

curl -v -X POST http://localhost:3000/

layer 进行加速匹配 demo

const express = require("./kaimo-express");
const app = express();app.post("/", (req, res, next) => {res.end("post okk end");
});
app.put("/", (req, res, next) => {res.end("put okk end");
});
app.delete("/", (req, res, next) => {res.end("delete okk end");
});
app.options("/", (req, res, next) => {res.end("delete okk end");
});app.listen(3000, () => {console.log(`server start 3000`);console.log(`在线访问地址：http://localhost:3000/`);
});

然后去访问：http://localhost:3000/，可以看到没有优化的时候会请求这些方法

优化之后可以看到就没有请求了

优化的代码如下：

application.js

const http = require("http");
const Router = require("./router");
const methods = require("methods");
console.log("methods----->", methods);function Application() {}// 调用此方法才开始创建，不是创建应用时直接装载路由
Application.prototype.lazy_route = function () {if (!this._router) {this._router = new Router();}
};methods.forEach((method) => {Application.prototype[method] = function (path, ...handlers) {this.lazy_route();this._router[method](path, handlers);};
});Application.prototype.listen = function () {const server = http.createServer((req, res) => {function done() {res.end(`kaimo-express Cannot ${req.method} ${req.url}`);}this.lazy_route();this._router.handle(req, res, done);});server.listen(...arguments);
};module.exports = Application;

router/index.js

const url = require("url");
const Route = require("./route");
const Layer = require("./layer");
const methods = require("methods");function Router() {// 维护所有的路由this.stack = [];
}Router.prototype.route = function (path) {// 产生 routelet route = new Route();// 产生 layer 让 layer 跟 route 进行关联let layer = new Layer(path, route.dispatch.bind(route));// 每个路由都具备一个 route 属性，稍后路径匹配到后会调用 route 中的每一层layer.route = route;// 把 layer 放到路由的栈中this.stack.push(layer);return route;
};methods.forEach((method) => {Router.prototype[method] = function (path, handlers) {// 1.用户调用 method 时，需要保存成一个 layer 当道栈中// 2.产生一个 Route 实例和当前的 layer 创造关系// 3.要将 route 的 dispatch 方法存到 layer 上let route = this.route(path);// 让 route 记录用户传入的 handler 并且标记这个 handler 是什么方法route[method](handlers);};
});Router.prototype.handle = function (req, res, out) {console.log("请求到了");// 需要取出路由系统中 Router 存放的 layer 依次执行const { pathname } = url.parse(req.url);let idx = 0;let next = () => {// 遍历完后没有找到就直接走出路由系统if (idx >= this.stack.length) return out();let layer = this.stack[idx++];// 需要判断 layer 上的 path 和当前请求路由是否一致，一致就执行 dispatch 方法if (layer.match(pathname)) {// 将遍历路由系统中下一层的方法传入// 加速匹配，如果用户注册过这个类型的方法在去执行if (layer.route.methods[req.method.toLowerCase()]) {layer.handle_request(req, res, next);} else {next();}} else {next();}};next();
};module.exports = Router;

route.js

const Layer = require("./layer");
const methods = require("methods");function Route() {this.stack = [];// 用来描述内部存过哪些方法this.methods = {};
}Route.prototype.dispatch = function (req, res, out) {// 稍后调用此方法时，回去栈中拿出对应的 handler 依次执行let idx = 0;console.log("this.stack----->", this.stack);let next = () => {// 遍历完后没有找到就直接走出路由系统if (idx >= this.stack.length) return out();let layer = this.stack[idx++];console.log("dispatch----->", layer.method);if (layer.method === req.method.toLowerCase()) {layer.handle_request(req, res, next);} else {next();}};next();
};
methods.forEach((method) => {Route.prototype[method] = function (handlers) {console.log("handlers----->", handlers);handlers.forEach((handler) => {// 这里的路径没有意义let layer = new Layer("/", handler);layer.method = method;// 做个映射表this.methods[method] = true;this.stack.push(layer);});};
});module.exports = Route;

layer.js

function Layer(path, handler) {this.path = path;this.handler = handler;
}Layer.prototype.match = function (pathname) {return this.path === pathname;
};
Layer.prototype.handle_request = function (req, res, next) {this.handler(req, res, next);
};
module.exports = Layer;