The previous section implemented the error handling middleware. This section implements compatibility with the old routing writing method.
Let’s look at an example of express’s secondary routing.
const express = require("express");
const userRouter = require("./routes/userRouter");
const articleRouter = require("./routes/articleRouter");
const app = express();
// 对用户进行操作，对文章进行操作
app.use("/user", userRouter);
app.use("/article", articleRouter);
app.listen(3000, () => {
console.log(`server start 3000`);
console.log(`在线访问地址：http://localhost:3000/`);
});
/routes/userRouter.js
const express = require("express");
let router = express.Router(); // 是个构造函数
router.get("/add", function (req, res) {
res.end("/user-add");
});
router.get("/remove", function (req, res) {
res.end("/user-remove");
});
module.exports = router;
/routes/articleRouter.js
const express = require("express");
let router = express.Router(); // 是个构造函数
router.get("/add", function (req, res) {
res.end("/article-add");
});
router.get("/remove", function (req, res) {
res.end("/article-remove");
});
module.exports = router;
The core method above is express.Router(), let’s implement this method below
Features of new: When new is a function, the function returns a reference type, then this reference type will be used as this
express.jsAdd Router in
const Application = require("./application");
function createApplication() {
// 通过类来实现分离操作
return new Application();
}
// 提供一个 Router 类，这个类可以 new 也可以当做函数来执行
createApplication.Router = require("./router");
module.exports = createApplication;
Then declare a proto object. By allowing the routing instance to find the original method through the chain, it can be compatible with the old routing writing method.
const url = require("url");
const Route = require("./route");
const Layer = require("./layer");
const methods = require("methods");
function Router() {
// 创建路由系统
let router = (req, res, next) => {
// 二级路由
res.end("req.url----->" + req.url);
};
// 兼容老的路由写法
// 维护所有的路由
router.stack = [];
// router 链上得有 get 等方法
// 让路由的实例可以通过链找到原来的方法
router.__proto__ = proto;
return router;
}
let proto = {
};
proto.route = function (path) {
// 产生 route
let 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) => {
proto[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);
};
});
proto.use = function (path, ...handlers) {
// 默认第一个是路径，后面是一个个的方法，路径可以不传
if (typeof path === "function") {
handlers.unshift(path);
path = "/";
}
// 如果是多个函数需要循环添加层
for (let i = 0; i < handlers.length; i++) {
let layer = new Layer(path, handlers[i]);
// 中间件不需要 route 属性
layer.route = undefined;
this.stack.push(layer);
}
};
proto.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 = (err) => {
// 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++];
if (err) {
console.log("统一对中间件跟路由错误处理");
// 找错误处理中间件
if (!layer.route) {
// 如果是中间件自己处理
layer.handle_error(err, req, res, next);
} else {
// 路由则跳过，继续携带错误向下执行
next(err);
}
} else {
// 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)) {
// 中间件没有方法可以匹配，不能是错误处理中间件
if (!layer.route) {
if (layer.handler.length !== 4) {
layer.handle_request(req, res, next);
} else {
next();
}
} else {
// 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;
The test demo is as follows
const express = require("./kaimo-express");
const userRouter = require("./routes2/userRouter");
const articleRouter = require("./routes2/articleRouter");
const app = express();
// 对用户进行操作，对文章进行操作
app.use("/user", userRouter);
app.use("/article", articleRouter);
app.use("/", (req, res, next) => {
res.end("kaimo");
});
app.listen(3000, () => {
console.log(`server start 3000`);
console.log(`在线访问地址：http://localhost:3000/`);
});
The other two files can be changed to reference express implemented by yourself.
const express = require("../kaimo-express");
