express(route、中间件)、log(morgan))

summary_2018/06 express

1、日常工作

• express_route
• express_中间件
• express_log_morgan

2、技术学习

• express_route

### Example
var express = require('express')
var app = express()
// respond with "hello world" when a GET request is made to the homepage
app.get('/', function (req, res) {
  res.send('hello world')
})
### Route paths(支持正则表达式)
//路径将匹配/abe并/abcde。
app.get('/ab(cd)?e', function (req, res) {
  res.send('ab(cd)?e')
})
### app.route（）,便于模块化
app.route('/book')
  .get(function (req, res) {
    res.send('Get a random book')
  })
  .post(function (req, res) {
    res.send('Add a book')
  })
  .put(function (req, res) {
    res.send('Update the book')
  })
### express.Router(一个Router实例是一个完整的中间件和路由系统; 出于这个原因，它通常被称为“迷你应用程序”。)
//birds.js
var express = require('express')
var router = express.Router()
// middleware that is specific to this router
router.use(function timeLog (req, res, next) {
  console.log('Time: ', Date.now())
  next()
})
// define the about route
router.get('/about', function (req, res) {
  res.send('About birds')
})
module.exports = router
//在应用程序中加载路由器模块
var birds = require('./birds')
//http://127.0.0.1:4000/birds/about
app.use('/birds', birds)
### 路由参数
Route path: /users/:userId/books/:bookId
Request URL: http://localhost:3000/users/34/books/8989
req.params: { "userId": "34", "bookId": "8989" }
//querystring,支持async
app.get('/ins', async (req, res) => {
    console.log(req.query)
  }
### responseMethod
Method  Description
res.download()  Prompt a file to be downloaded.
res.end()   End the response process.
res.json()  Send a JSON response.
res.jsonp() Send a JSON response with JSONP support.
res.redirect()  Redirect a request.
res.render()    Render a view template.
res.send()  Send a response of various types.
res.sendFile()  Send a file as an octet stream.
res.sendStatus()    Set the response status code and send its string representation as the response body.

• express中间件
  
  • 注册：use/method
  • next()-如果当前的中间件功能没有结束请求-响应周期，则它必须调用next()以将控制传递给下一个功能。否则，请求将被挂起。

var express = require('express')
var app = express()
//定义中间件
var requestTime = function (req, res, next) {
  req.requestTime = Date.now()
  next()
}
//使用中间件
app.use(requestTime)
app.get('/', function (req, res) {
  var responseText = 'Hello World!<br>'
  responseText += '<small>Requested at: ' + req.requestTime + '</small>'
  res.send(responseText)
})
app.listen(3000)
### 可配置的中间件(传递参数)
文件： my-middleware.js
module.exports = function(options) {
  return function(req, res, next) {
    // 根据参数配置
    next()
  }
}
使用中间件，如下所示。
var mw = require('./my-middleware.js')
app.use(mw({ option1: '1', option2: '2' }))
### 中间件堆栈
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()
})
#### 应用程序级
var app = express()
//没有路由功能，任何应用程序收到都会执行
app.use(function (req, res, next) {
  console.log('Time:', Date.now())
  next()
})
// /user/:id路径上安装的中间件功能
app.use('/user/:id', function (req, res, next) {
  console.log('Request Type:', req.method)
  next()
})
//路由器中间件堆栈
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')
})
Tips：跳过路由器中间件堆栈中的其余中间件功能，调用next('route')以将控制权传递给下一个路由。仅适用于使用app.METHOD()或router.METHOD()功能加载的中间件功能。
// handler for the /user/:id path, which renders a special page
app.get('/user/:id', function (req, res, next) {
  res.render('special')
})
#### 路由级中间件
//由器级中间件的工作方式与应用级中间件的工作方式相同，只是它绑定到一个实例express.Router()。
#### 错误处理中间件
app.use(function (err, req, res, next) {
  console.error(err.stack)
  res.status(500).send('Something broke!')
})
#### 内置中间件和第三方中间件

• express_log_morgan:日志处理