Article directory
1. Basic use of koa
- Install
npm i koa - What koa exports is a class, which must
newbe created using keywords - Koa also completes request operations by registering middleware
const koa = require('koa');
// 导出的类，必须用new关键字
const app = new koa()
app.listen(8000, () => {
console.log('koa 服务器启动~')
})
// 使用koa这里传递两个参数 cxt 与next
app.use((cxt, next) => {
console.log('匹配中间')
cxt.body = '使用cxt中的body返回数据'
})
2. Parameter analysis
- The middleware registered by koa provides two parameters:
- ctx: context object;
- Koa does not separate req and res like express, but uses them as attributes of ctx;
- ctx represents the context object of a request;
- ctx.request: Get the request object;
- ctx.response: Get the response object;
- next: essentially a dispatch, similar to the previous next;
注意点
cxtThe context has两a request object, one isrequest既koa本身的对象, and anothernode 封装的请求对象:req- Two response objects:
cxt.response 是koa封装的响应式对象 ，txt.res 是node封装的响应式对象
app.use((cxt, next) => {
/** 注意点 两个请求对象
* @description: cxt 上下文有两个请求对象一个是request既koa本身的对象，还有一个node封装的请求对象:req
* @param {type}
*/
cxt.request //
cxt.req
/** 响应对象 两个响应对象
* @description: cxt.response 是koa封装的响应式对象
* @param {type} txt.res 是node封装的响应式对象
* @return:
*/
cxt.body = '使用cxt中的body返回数据'
})
3. Request path distinction
- Through the app object created by koa, the middleware can only be registered through the use method:
- Koa does not provide
methods的方式来注册中间件； - Neither
提供path中间件来匹配路径;
- Koa does not provide
- But how do we separate paths and methods in development?
- Method 1:
根据request自己来判断; - Method 2:
使用第三方路由中间件;
- Method 1:
// path
// app.use((cxt, next) => {
// if (cxt.path === '/users') {
// } else if (cxt.path === '/login') {
// cxt.body = '登录成功'
// } else { }
// })
// method
app.use((cxt, next) => {
if (cxt.method === 'POST') {
cxt.body = '登录成功'
} else {
}
})
4. Routing
- Install
npm install @koa/router
const koa = require('koa');
const router = require('@koa/router')
const app = new koa()
// 1. 安装路由使用 npm i @koa/router
const userRouter = new router({
prefix: '/users' })
//2. 注册路由中间件
userRouter.get('/', (cxt, next) => {
cxt.body = '路由使用'
})
userRouter.get('/:id', (cxt, next) => {
const id = cxt.params.id
console.log(id);
cxt.body=id
})
// 3. 路由生效
app.use(userRouter.routes())
// allowedMethods路径或者方法匹配配置
app.use(userRouter.allowedMethods())
app.listen(8000, () => {
console.log('koa 服务器启动~')
})
Note :allowedMethods用于判断某一个method是否支持：某个请求或者路径是否正确
5 Parameter analysis
- get params method example
:/:id - Example of get query method:
?name=admin&age=18 - post json method example
{name:"admin" pass:123456} - post x-www-form-urlencoded
- post form-data
注意点The following routes are uniformly registered asusers
const userRouter = new router({
prefix: '/users' })
5.1 params and query parsing
- params parametercxt.params.id
- query parametercxt.query
userRouter.get('/:id', (cxt, next) => {
const id = cxt.params.id
cxt.body = id
})
userRouter.get('/', (cxt, next) => {
const query = cxt.query
cxt.body = query
})
5.2 Body parameters and urlencoded analysis
- Install dependencies:
npm install koa-bodyparser; - Use and register the koa-bodyparser middleware;
app.use(bodyparser())
// 3. post/json body参数
// 安装库 npm install koa - bodyparser
// app.use(bodyparser())
// userRouter.post('/', (cxt, next) => {
// const body= cxt.request.body
// cxt.body=body
// })
// 4. urlencoded
app.use(bodyparser())
userRouter.post('/', (cxt, next) => {
const body = cxt.request.body
cxt.body = body
})
5.3 form-data parameter
- To parse the data in the body, you need to use multer
- Install dependencies:
npm install --save @koa/multer multer
const upload =multer({
})
app.use(upload.any())
app.use((cxt,next)=>{
console.log(cxt.req.body);
})
6. File upload
Specific configuration reference
const koa = require('koa');
const router = require('@koa/router')
const multer = require('@koa/multer')
const app = new koa()
app.listen(8000, () => {
console.log('koa 服务器启动~')
})
const userRouter = new router({
prefix: '/users' })
/**
* 5. post form-data
*/
let storage = multer.diskStorage({
destination: (req, file, cb) => {
cb(null, './uploads/')
},
filename: (ctx, file, cb) => {
cb(null, file.originalname);
}
});
const upload = multer({
storage
})
userRouter.post('/', upload.single('file'), (cxt, next) => {
})
// 5. form-data 解析 需要使用multer
app.use(userRouter.routes())
7. Static server
- Koa does not have built-in deployment-related functions, so you need to use a third-party library:
- Install dependencies
npm install koa-static
const static=require("koa-static")
const app = new koa()
app.use(static('./upload'))
8 response data
- Response result: body sets the response body to one of the following:
string ：string dataBuffer:Buffer dataStream: streaming dataObject|| Array：object or arraynull ：output nothing- if
response.status尚未设置，Koa会自动将状态设置为200或204.
const userRouter = new router({
prefix: '/users' })
userRouter.post('/', (cxt, next) => {
// 1.buffer 响应数据
// cxt.body=Buffer.from('hello node')
// 2. 文件流
// const readerStream = fs.createReadStream('./upload/th5TYWK266.jpg')
// cxt.type = 'image/jpeg' // 请求展示图片
// cxt.body = readerStream
// 3.响应数组或者对象类型
cxt.body={
name:'admin',
password:123456
}
})
9 Error handling
- When doing unified encapsulation of error handling:
cxt上下文可以触发一个emit事件 - Therefore, you can use
app.onto listen for events
const koa = require('koa');
const router = require('@koa/router')
const app = new koa()
app.listen(8000, () => {
console.log('koa 服务器启动~')
})
const userRouter = new router({
prefix: '/users' })
userRouter.get('/', (cxt, next) => {
const isAuth = false
if (isAuth) {
cxt.body = '登录成功，返回token'
} else {
// cxt.body = {
// code: 1001,
// message: '没有进行授权'
// }
// 统一处理错误
cxt.app.emit('errorEvent', 1001,cxt)
}
})
app.on('errorEvent', (code,cxt) => {
let message = ''
switch (code) {
case 1001:
message = '没有授权'
break
default: 1002
message = '成功'
}
const body = {
code,
message
}
cxt.body=body
})
app.use(userRouter.routes())