javascript - Express 中的中间件链接

Question

我正在编写 API，想了解添加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执行相同的操作，例如验证主机/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，例如 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();
    }

或者类似这样的东西:

    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 的可配置性比您想象的要高得多。您还可以在公共(public)路径中安装公共(public)中间件:

1. 如果所有路由都使用中间件:

   // 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);
   

2. 如果只有特定模式网址使用中间件:

   // 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);
   

3. 如果子路径中的所有 url 都使用中间件。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);
   

<小时/>

如果上述任何一个都不吸引您，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);
            });
        });
    });
}

可以用更少嵌套的方式编写:

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);
}