Express

中间件的组成

中间件函数可以执行以下任何任务：

执行任何代码

修改 request 或者 response 响应对象

结束请求响应周期

调用下一个中间件

中间件分类

应用程序级别中间件

路由级别中间件

错误处理中间件

内置中间件

第三方中间件

应用程序级别中间件

不关心请求路径：

 
var app = express();

app.use(function(req, res, next) {
  console.log("Time:", Date.now());
  next();
});

限定请求路径：

app.use("/user/:id", function(req, res, next) {
  console.log("Request Type:", req.method);
  next();
});

限定请求方法：

app.get("/user/:id", function(req, res, next) {
  res.send("USER");
});

多个处理函数：

app.use(
  "/user/:id",
  function(req, res, next) {
    console.log("Request URL:", req.originalUrl);
    next();
  },
  function(req, res, next) {
    console.log("Request Type:", req.method);
    next();
  }
);

多个路由处理函数：

app.get(
  "/user/:id",
  function(req, res, next) {
    console.log("ID:", req.params.id);
    next();
  },
  function(req, res, next) {
    res.send("User Info");
  }
);

// handler for the /user/:id path, which prints the user ID
app.get("/user/:id", function(req, res, next) {
  res.end(req.params.id);
});

最后一个例子：

app.get(
  "/user/:id",
  function(req, res, next) {
    // if the user ID is 0, skip to the next route
    if (req.params.id === "0") next("route");
    // otherwise pass the control to the next middleware function in this stack
    else next();
  },
  function(req, res, next) {
    // render a regular page
    res.render("regular");
  }
);

// handler for the /user/:id path, which renders a special page
app.get("/user/:id", function(req, res, next) {
  res.render("special");
});

路由级别中间件

创建路由实例：

var router = express.Router();

示例：

var app = express();
var router = express.Router();

// a middleware function with no mount path. This code is executed for every request to the router
router.use(function(req, res, next) {
  console.log("Time:", Date.now());
  next();
});

// a middleware sub-stack shows request info for any type of HTTP request to the /user/:id path
router.use(
  "/user/:id",
  function(req, res, next) {
    console.log("Request URL:", req.originalUrl);
    next();
  },
  function(req, res, next) {
    console.log("Request Type:", req.method);
    next();
  }
);

// a middleware sub-stack that handles GET requests to the /user/:id path
router.get(
  "/user/:id",
  function(req, res, next) {
    // if the user ID is 0, skip to the next router
    if (req.params.id === "0") next("route");
    // otherwise pass control to the next middleware function in this stack
    else next();
  },
  function(req, res, next) {
    // render a regular page
    res.render("regular");
  }
);

// handler for the /user/:id path, which renders a special page
router.get("/user/:id", function(req, res, next) {
  console.log(req.params.id);
  res.render("special");
});

// mount the router on the app
app.use("/", router);

另一个示例：

var app = express();
var router = express.Router();

// predicate the router with a check and bail out when needed
router.use(function(req, res, next) {
  if (!req.headers["x-auth"]) return next("router");
  next();
});

router.get("/", function(req, res) {
  res.send("hello, user!");
});

// use the router and 401 anything falling through
app.use("/admin", router, function(req, res) {
  res.sendStatus(401);
});

错误处理中间件

app.use(function(err, req, res, next) {
  console.error(err.stack);
  res.status(500).send("Something broke!");
});

内置中间件

express.static serves static assets such as HTML files, images, and so on.

express.json parses incoming requests with JSON payloads. NOTE: Available with Express 4.16.0+

express.urlencoded parses incoming requests with URL-encoded payloads. NOTE: Available with Express 4.16.0+

官方支持的中间件列表：

https://github.com/senchalabs/connect#middleware

第三方中间件

官方中间件资源：http://expressjs.com/en/resources/middleware.html

早期的 Express 内置了很多中间件。后来 Express 在 4.x 之后移除了这些内置中间件，官方把这些功能性中间件以包的形式单独提供出来。这样做的目的是为了保持 Express 本身极简灵活的特性，开发人员可以根据自己的需求去灵活的定制。下面是官方提供的一些常用的中间件解决方案。

Middleware module	Description	Replaces built-in function (Express 3)
body-parser	Parse HTTP request body. See also: body , co-body , and raw-body .	express.bodyParser
compression	Compress HTTP responses.	express.compress
connect-rid	Generate unique request ID.	NA
cookie-parser	Parse cookie header and populate `req.cookies` . See also cookies and keygrip .	express.cookieParser
cookie-session	Establish cookie-based sessions.	express.cookieSession
cors	Enable cross-origin resource sharing (CORS) with various options.	NA
csurf	Protect from CSRF exploits.	express.csrf
errorhandler	Development error-handling/debugging.	express.errorHandler
method-override	Override HTTP methods using header.	express.methodOverride
morgan	HTTP request logger.	express.logger
multer	Handle multi-part form data.	express.bodyParser
response-time	Record HTTP response time.	express.responseTime
serve-favicon	Serve a favicon.	express.favicon
serve-index	Serve directory listing for a given path.	express.directory
serve-static	Serve static files.	express.static
session	Establish server-based sessions (development only).	express.session
timeout	Set a timeout period for HTTP request processing.	express.timeout
vhost	Create virtual domains.	express.vhost

中间件应用

输出请求日志中间件

功能：实现为任何请求打印请求日志的功能。

logger.js 定义并导出一个中间件处理函数：

module.exports = (req, res, next) => {
  console.log(`${req.method} -- ${req.path}`);
  next();
};

app.js 加载使用中间件处理函数：

app.use(logger);

统一处理静态资源中间件

功能：实现 express.static() 静态资源处理功能

static.js 定义并导出一个中间件处理函数：

const fs = require("fs");
const path = require("path");

module.exports = function static(pathPrefix) {
  return function(req, res, next) {
    const filePath = path.join(pathPrefix, req.path);
    fs.readFile(filePath, (err, data) => {
      if (err) {
        // 继续往后匹配查找能处理该请求的中间件
        // 如果找不到，则 express 会默认发送 can not get xxx
        return next();
      }
      res.end(data);
    });
  };
};

app.js 加载并使用 static 中间件处理函数：

// 不限定请求路径前缀
app.use(static("./public"));
app.use(static("./node_modules"));

// 限定请求路径前缀
app.use("/public", static("./public"));
app.use("/node_modules", static("./node_modules"));

错误处理

参考文档：

Error handling

常用 API

参考文档：

4.x API

express

express.json

express.static

express.Router

express.urlencoded()

Application

app.set

app.get

app.locals

Request

req.app

req.query

req.body

req.cookies

req.ip

req.hostname

Req.method

req.params

req.path

req.get()

Response

res.locals

res.append()

res.cookie()

res.clearCookie()

res.download()

res.end()

res.json()

res.jsonp()

res.redirect()

res.render()

res.send()

res.sendStatus()

res.set()

res.status()

Router

router.all()

router.METHOD()

router.use()

node

Express

中间件的组成

中间件分类

应用程序级别中间件

路由级别中间件

错误处理中间件

内置中间件

第三方中间件

中间件应用

输出请求日志中间件

统一处理静态资源中间件

错误处理

常用 API

express

Application

Request

Response

Router

相关

在虚拟机(centos)上安装或卸载nodejs

Prometheus之node exporter使用帮助

k8s-调度亲和性和污点容忍、指定调度节点(nodeSelector)

nodejs 一个简单的web服务器，用于前端自己快速测试部署

node-scss npm的时候报错

nodejs搭建web服务器初级

在Mac OS上将Node.js连接到XAMPP MySQL服务器一直报错error connecting: Error: conne

Node.js安装和配置npm

Node 接入阿里云实现短信验证码

node-pre-gyp WARN Pre-bui 在此解决方案中一次生成一个项目。若要启用并行生成，请添加

nodemon运行提示错误：无法加载文件 C:\Users\gxf\AppData\Roaming\npm\nodemon.

nvm安装以及管理多版本node教程

标签