南风知我意的技术博客

Appearance

一、koa2 ​

官网参考：https://koa.bootcss.com/

  • express 中间件是异步回调，koa2 原生支持 async/await
  • 新开发框架和系统，都开始基于 koa2，例如 egg.js
  • express 虽然过时，但是 koa2 肯定是未来的趋势
1. async/await 语法，安装和使用 koa2 ​
  • async/await 语法
    • await 后面可以追加 promise 对象，获取 resolve 的值
    • await 必须包裹在 async 函数里面
    • async 函数执行返回的也是一个 promise 对象
    • try-catch 截获 promise 中 reject 的值
  • koa2
    • 安装(使用脚手架)
      shell
      npm i koa-generator -g
Koa2 koa2-test
npm i & npm run dev
    • 初始化代码，处理路由
      • 环境配置
        shell
        npm i cross-env -S 

"dev": "cross-env NODE_ENV=dev ./node_modules/.bin/nodemon bin/www",
"prd": "cross-env NODE_ENV=production pm2 start bin/www",
      • app.js
        js
        const Koa = require('koa')
const app = new Koa()
const views = require('koa-views')
const json = require('koa-json')
const onerror = require('koa-onerror')
const bodyparser = require('koa-bodyparser')
const logger = require('koa-logger')

const index = require('./routes/index')
const users = require('./routes/users')

// error handler
onerror(app)

// middlewares
app.use(bodyparser({
  enableTypes:['json', 'form', 'text']
}))
app.use(json())
app.use(logger())
app.use(require('koa-static')(__dirname + '/public'))

app.use(views(__dirname + '/views', {
  extension: 'pug'
}))

// logger
app.use(async (ctx, next) => {
  const start = new Date()
  await next()
  const ms = new Date() - start
  console.log(`${ctx.method} ${ctx.url} - ${ms}ms`)
})

// routes
app.use(index.routes(), index.allowedMethods())
app.use(users.routes(), users.allowedMethods())

// error-handling
app.on('error', (err, ctx) => {
  console.error('server error', err, ctx)
});

module.exports = app
2. 开发接口、连接数据库、实现登录、日志记录 ​

和 express 类似 基于 koa-generic-session 和 koa-redis ioredis

  • 插件安装

    shell
    npm i koa-generic-session koa-redis ioredis -S

  • session redis 在app.js中的配置

    javascript
    const session = require('koa-generic-session')
const redisStore = require('koa-redis')

  app.use(session({
  // 配置 cookie
  cookie: {
    path: '/',
    httpOnly: true,
    maxAge: 24 * 60 * 60 * 1000
  },
  // 配置 redis
  store: redisStore({
    all: '127.0.0.1:6379'
  })
}))

  • 路由

    • 插件安装
      shell
      npm i mysql xss -S
    • 相关配置

      • mysql redis

        js
        const env = process.env.NODE_ENV;

// 配置
let MYSQL_CONF
let REDIS_CONF

if (env === 'dev') {
  MYSQL_CONF = {
    host: '127.0.0.1',
    user: 'root',
    password: '123qwe!@#',
    port: '3306',
    database: 'myblog'
  }
  REDIS_CONF = {
    port: 6379,
    // host: '139.129.240.151'
    host: '127.0.0.1'
  }
}


if (env === 'production') {
  MYSQL_CONF = {
    host: 'localhost',
    user: 'root',
    password: '123qwe!@#',
    port: '3306',
    database: 'myblog'
  }
  REDIS_CONF = {
    port: 6379,
    // host: '139.129.240.151',
    host: '127.0.0.1'
  }
}
module.exports = {
  MYSQL_CONF,
  REDIS_CONF
}

      • mysql 工具封装

        js
        const mysql = require('mysql');
const { MYSQL_CONF } = require('../config/db');

// 创建连接对象
const con = mysql.createConnection(MYSQL_CONF);

// 开始连接
con.connect()

// 统一执行 sql 的函数
function exec(sql) {
  const promise = new Promise((resolve, reject) => {
    con.query(sql, (err, result) => {
      if (err) {
        reject(err)
        return;
      }
      resolve(result)
    })
  })
  return promise;
}

module.exports = {
  exec,
  escape: mysql.escape
}
        js
        const crypto = require('crypto');

// 秘钥
const SECRET_KEY = 'ASDASD_12';

// md5 加密
function md5(content) {
  let md5 = crypto.createHash('md5');
  return md5.update(content).digest('hex');
}

// 加密函数
function genPassword(password) {
  const str = `password=${password}&key=${SECRET_KEY}`;
  return md5(str);
}

module.exports = {
  genPassword
}

      • 中间件

        js
        const { ErrorModel } = require('../model/resModel');

module.exports = async (ctx, next) => {
  if (req.session.username) {
    await next()
    return;
  }
  ctx.body = new ErrorModel('未登录')
}

      • controller

        js
        const { exec } = require('../db/mysql')

const getList = async (author, keyword) => {
  let sql = `select * from blogs where 1=1 `
  if (author) {
    sql += `and author = '${author}' `
  }
  if (keyword) {
    sql += `and title like '%${keyword}%' `
  }
  sql += `order by createtime desc;`
  return await exec(sql)
}

const getDetail = async (id) => {
  const sql = `select * from blogs where id = '${id}'`;
  const rows = await exec(sql);
  return rows[0];
}

const newBlog = async (blogData = {}) => {
  const { title, content, author } = blogData;
  const createTime = Date.now();
  const sql = `
    insert into blogs (title, content, createtime, author)
    values ('${title}', '${content}', '${createTime}', '${author}')
  `
  const data = await exec(sql);
  return {
    id: data.insertId
  }
}
const updateBlog = async (id, blogData = {}) => {
  const {title, content} = blogData;
  const sql = `
    update blogs set title='${title}', content='${content}' where id='${id}'
  `
  const updateData = await exec(sql);
  if (updateData.affectedRows > 0) {
    return true
  }
  return false
}

const deleteBlog = async (id, author) => {
  const sql = `delete from blogs where id = '${id}' and author='${author}'`
  const delData = await exec(sql);
  if (delData.affectedRows > 0) {
    return true
  }
  return false
}


module.exports = {
  getList,
  getDetail,
  newBlog,
  updateBlog,
  deleteBlog
}

      • router

        js
        const router = require('koa-router')()
const { getList, getDetail, newBlog, updateBlog, deleteBlog } = require('../controller/blog');
const { SuccessModel, ErrorModel } = require('../model/resModel');
const loginCheck = require('../middleware/loginCheck')
router.prefix('/api/blog')

router.get('/list', async function (ctx, next) {
  const author = ctx.query.author || '';
  const keyword = ctx.query.keyword || '';
  const result = await getList(author, keyword);
  ctx.body = new SuccessModel(result)
})

router.get('/detail', async function (ctx, next) {
  const result = await getDetail(ctx.query.id);
  ctx.body = new SuccessModel(result);
})

router.post('/new', loginCheck, async function (ctx, next) {
  const body = ctx.request.body
  body.author = ctx.session.username; // 假数据
  const result = await  newBlog(body);
  ctx.body = new SuccessModel(result);
})
router.post('/update', loginCheck, async function (ctx, next) {
  const result = await  updateBlog(ctx.query.id, ctx.request.body);
  ctx.body = result? new SuccessModel(): new ErrorModel('更新博客失败');
})
router.post('/del', loginCheck, async function (ctx, next) {
  const author = ctx.session.username;
  const result = deleteBlog(ctx.query.id, author);
  ctx.body = result? new SuccessModel(): new ErrorModel('删除博客失败');
})


module.exports = router

      • app.js

        js
        const Koa = require('koa')
const app = new Koa()
const views = require('koa-views')
const json = require('koa-json')
const onerror = require('koa-onerror')
const bodyparser = require('koa-bodyparser')
const logger = require('koa-logger')

const index = require('./routes/index')
const users = require('./routes/users')

// error handler
onerror(app)

// middlewares
app.use(bodyparser({
  enableTypes:['json', 'form', 'text']
}))
app.use(json())
app.use(logger())
app.use(require('koa-static')(__dirname + '/public'))

app.use(views(__dirname + '/views', {
  extension: 'pug'
}))

// logger
app.use(async (ctx, next) => {
  const start = new Date()
  await next()
  const ms = new Date() - start
  console.log(`${ctx.method} ${ctx.url} - ${ms}ms`)
})

// routes
app.use(index.routes(), index.allowedMethods())
app.use(users.routes(), users.allowedMethods())

// error-handling
app.on('error', (err, ctx) => {
  console.error('server error', err, ctx)
});

module.exports = app

  • 日志

  • access log 记录，使用 morgan
  • 自定义日志使用 console.log 和 console.error
  • 日志文件拆分、日志文件分析
  • 插件安装
    shell
    npm i koa-morgan -S
  • 配置app.js
    javascript
    const path = require('path');
const fs = require('fs');
const morgan = require('koa-morgan');

const ENV = process.env.NODE_ENV;
if (ENV !== 'production') {
  app.use(morgan('dev') );
} else {
  const logFileName = path.resolve(__dirname, 'logs', 'access.log')
  const writeStream = fs.createWriteStream(logFileName, {
    flags: 'a'
  })
  app.use(morgan('combined', {
    stream: writeStream
  }) );
}
3. 分析koa2中间件原理 ​
js
const Koa = require('koa');
const app = new Koa();

// 非常典型的洋葱圈模型
// logger
app.use(async (ctx, next) => {
  await next();
  const rt = ctx.response.get('X-Response-Time');
  console.log(`${ctx.method} ${ctx.url} - ${rt}`);
});

// x-response-time
app.use(async (ctx, next) => {
  const start = Date.now();
  await next();
  const ms = Date.now() - start;
  ctx.set('X-Response-Time', `${ms}ms`);
});

// response
app.use(async ctx => {
  ctx.body = 'Hello World';
});

app.listen(3000);

// 执行顺序 5 6 12 14 20 15 7

  • 分析

    • app.use 用来注册中间件，先收集起来
    • 实现 next 机制，即上一个通过 next 触发下一个
    • 不涉及 method 和 path 的判断

  • 模拟实现

    js
    const http = require('http');

// 组合中间件
function compose(middlewareList) {
  return function (ctx) {
    function dispatch(i) {
      const fn = middlewareList[i];
      try {
        return Promise.resolve(fn(ctx, dispatch.bind(null, i + 1)));
      } catch (err) {
        return Promise.reject(err);
      }
    }
    return dispatch(0)
  }
}

class LikeKoa2 {
  constructor() {
    this.middlewareList = [];
  }

  use(fn) {
    this.middlewareList.push(fn);
    return this;
  }

  createContext(req, res) {
    const ctx = {
      req,
      res
    }
    return ctx
  }

  handlerRequest(ctx, fn) {
    return fn(ctx)
  }

  callBack() {
    const fn = compose(this.middlewareList);
    return (req, res) => {
      const ctx = this.createContext(req, res);
      return this.handlerRequest(ctx, fn);
    }
  }

  listen(...args) {
    const server = http.createServer(this.callBack());
    server.listen(...args);
  }
}

module.exports = LikeKoa2
    js
    const Koa = require('./like-koa2');
const app = new Koa();

// 非常典型的洋葱圈模型
// logger
app.use(async (ctx, next) => {
  console.log('第一层洋葱 - 开始')
  await next();
  const rt = ctx['X-Response-Time'];
  console.log(`${ctx.req.method} ${ctx.req.url} - ${rt}`);
  console.log('第一层洋葱 - 结束')
});

// x-response-time
app.use(async (ctx, next) => {
  console.log('第二层洋葱 - 开始')
  const start = Date.now();
  await next();
  const ms = Date.now() - start;
  ctx['X-Response-Time'] = `${ms}ms`;
  console.log('第二层洋葱 - 结束')
});

// response
app.use(async ctx => {
  console.log('第三层洋葱 - 开始')
  ctx.res.end('This is like koa2')
  console.log('第三层洋葱 - 结束')
});

app.listen(8004);

Released under the MIT License.

Copyright © 2021-present eastern