• 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：

     

     

    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：

     

    常用 API

     

    参考文档：

     

    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()

     
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  • 原文地址：https://www.cnblogs.com/zhanghuajie/p/express.html
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