Express 中的中间件链接

Question

我正在编写 API，想了解添加由多个路由共享的中间件的好方法是什么。中间件在每个路由中做同样的事情，比如验证 hosts/ip、验证用户等。 req 对象与每个中间件中的其他对象一起加载，如 req.host、req.ip、req.username 等

    app.post("/route1", middleware1, middleware2, middleware3, middleware4);
    app.post("/route2", middleware1, middleware2, middleware3, middleware4);

    const middleware1 = (req, res, next) => {
     // does something to validate user
     req.username = "username"
     next();
    }
    const middleware2 = (req, res, next) => {
     // host validation
     req.host = "something modified in validation"
     next();
    }
    const middleware3 = (req, res, next) => {
     // checks for mac and ip
     req.mac = "mac addr"
     next();
    }
    const middleware4 = (req, res, next) => {
     res.send();
    }

或者像这样：


    app.post("/route1", middleware1);
    app.post("/route2", middleware1);


    const middleware1 = (req, res) => {
      // does something to validate user
      req.username = "username"
      middleware2(req, res);
    }
    const middleware2 = (req, res) => {
      // host validation
      req.host = "something modified in validation"
      middleware3(req, res);
    }
    const middleware3 = (req, res) => {
      // checks for mac and ip
      req.mac = "mac addr"
      middleware4(req, res);
    }
    const middleware1 = (req, res) => {
      res.send();
    }

谢谢。

Answer 1

通常我不会直接从另一个中间件调用中间件。它混合了中间件逻辑的职责和中间件的使用位置。

Express 比您想象的更易于配置。也可以在常用路径下安装常用中间件：

如果所有路由使用中间件：

// How common middlewares are normally installed:
app.post(middleware1);
app.post(middleware2);
app.post(middleware3);
app.post(middleware4);

// Alternative, less common way to do it:
app.post(middleware1,middleware2,middleware3,middleware4);

如果只有 url 的特定模式使用中间件：

// Use a regexp:
app.post(/route(1|2)/, middleware1, middleware2, middleware3, middleware4);

// Or if you don't like regexp, use globs:
app.post('route*', middleware1, middleware2, middleware3, middleware4);
// Or a more specific glob pattern:
app.post('route1?2?', middleware1, middleware2, middleware3, middleware4);

如果子路径中的所有 url 使用中间件。例如，假设 /route/... 中的所有 url 都使用中间件：

const route = express.Router();

app.use('/route',route);
route.post(middleware1);
route.post(middleware2);
route.post(middleware3);
route.post(middleware4);

如果上述 none 对您有吸引力，您仍然可以使用第二个选项，但不是在彼此内部调用中间件，而是编写一个中间件来初始化中间件：

function commonMiddlewares (req, res, next) {

    middleware1(req,res,function() {
        middleware2(req,res,function() {
            middleware3(req,res,function() {
                middleware4(req,res,next);
            });
        });
    });
}

可以写成少嵌套的方式：

function commonMiddlewares (req, res, next) {
    function runMiddleware4 () {
        middleware4(req,res,next);
    }
    function runMiddleware3 () {
        middleware3(req,res,runMiddleware4);
    }
    function runMiddleware2 () {
        middleware2(req,res,runMiddleware3);
    }

    middleware1(req,res,runMiddleware2);
}

Answer 2

const express = require('express')
const { routesMiddleware } =require('./middlewares')
const { pureVaidationsFunctions1 } =require('./services')

const rout1 =express.Router()
const rout2 =express.Router()

const app = express()

app.use('/route1',route1)
app.use('/route2',route2)

// routesMiddleware a middleware to handle the execution of list of functions

// pureVaidationsFunctions1 list of funtions that `routesMiddleware` will consume
route1.post(routesMiddleware(pureVaidationsFunctions1))
route2.post(routesMiddleware(pureVaidationsFunctions2))

有道理吗？

Answer 3

您可以指定多个中间件，参见the app.use docs:

An array of combinations of any of the above.

您可以创建一个包含所有中间件的文件，例如 -

middlewares.js

module.exports = [
  function(req, res, next){...},
  function(req, res, next){...},
  function(req, res, next){...},
  .
  .
  .
  function(req, res, next){...},
]

然后简单地添加它：

/*
you can pass any of the below inside app.use()
A middleware function.
A series of middleware functions (separated by commas).
An array of middleware functions.
A combination of all of the above.
*/
app.use(require('./middlewares.js'));

注意 - 仅对所有此类请求通用的中间件执行此操作。

Express 中的中间件链接

Chaining of middleware in Express

javascript

api

middleware

node.js

express