Summary

Basics of Koa2

Quick Start with Running a Http Service

const Koa = require('koa');
const app = new Koa();

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

app.listen(3000); 

App instance

app.keys

app.keys = ['im a newer secret', 'i like turtle'];
app.keys = new KeyGrip(['im a newer secret', 'i like turtle'], 'sha256');

app.context

app.context.db = db();

app.use(async ctx => {
  console.log(ctx.db);
});

app.use(function) sets a middleware

app.use(someMiddleware)
app.use(someOtherMiddleware)
app.listen(3000)
// app.use() 返回 this, 因此可以链式表达.

app.use(someMiddleware).use(someOtherMiddleware).listen(3000)

App Error Handling

app.on('error', (err, ctx) => {
  log.error('server error', err, ctx)
});

App throws error

// ctx.throw([status], [msg], [properties]) 用来抛出一个包含 status 属性错误的帮助方法，其默认值为 500
ctx.throw(400);
ctx.throw(400, 'name required');
ctx.throw(400, 'name required', { user: user });

// ctx.throw(400, 'name required') 等效于
const err = new Error('name required');
err.status = 400;
err.expose = true;
throw err;

Koa Router

Basic Usage

var Koa = require('koa');
var Router = require('koa-router');

var app = new Koa();
var router = new Router();

router.get('/', (ctx, next) => {
  // ctx.router available
});

app.use(router.routes(), router.allowedMethods())

Get dynamic parameters from URL

router.get('/:category/:title', (ctx, next) => {
  console.log(ctx.params);
  // => { category: 'programming', title: 'how-to-node' }
});

Middleware Processing

router.get(
  '/users/:id',
  (ctx, next) => {
    return User.findOne(ctx.params.id).then(function(user) {
      ctx.user = user;
      next();
    });
  },
  ctx => {
    console.log(ctx.user);
    // => { id: 17, name: "Alex" }
  }
)

prefix

router.prefix('/things/:thing_id')

Registration Order

// routes
app.use(blogHomeAPIRouter.routes(), blogHomeAPIRouter.allowedMethods());
app.use(blogViewRouter.routes(), blogViewRouter.allowedMethods());
app.use(utilsAPIRouter.routes(), utilsAPIRouter.allowedMethods());
app.use(userAPIRouter.routes(), userAPIRouter.allowedMethods());
app.use(userViewRouter.routes(), userViewRouter.allowedMethods());
app.use(errorViewRouter.routes(), errorViewRouter.allowedMethods()); // 错误 404 路由注册到最后面

Start mysql and connect to the database using sequelize

1. Simplify SQL queries: Sequelize provides a powerful query API that allows simple JavaScript objects to represent SQL queries without the need to manually write SQL statements. This makes the code more readable and maintainable.
2. Support multiple databases: Sequelize not only supports MySQL, but also other mainstream databases such as PostgreSQL, SQLite, MariaDB, etc., which allows developers to use the same ORM library in different projects.
3. Increase development efficiency: Sequelize can help developers generate database models automatically, and provides automatic migration functionality, making database migration and upgrade easy.
4. Avoid SQL injection attacks: Using Sequelize can avoid SQL injection attacks caused by hand-written SQL statements, as Sequelize has built-in parameter binding functionality that can safely pass parameters to SQL queries.

Connection and synchronization

//config
//conf/db
let MYSQL_CONF = {
  host: "localhost",
  user: "root",
  password: "",
  port: "3306",
  database: "koa2_db",
};

// terminal 启动 mysql
mysql.server start

Connecting to Database with Sequelize

const Sequelize = require("sequelize");
const { MYSQL_CONF } = require("../conf/db");
const { host, user, password, database } = MYSQL_CONF;

const conf = {
  host,
  dialect: "mysql",
  // 连接池
	pool: {
	  max: 5, // 连接池中的最大的连接数量
	  min: 0, // 最小
	  idle: 10000, // 如果一个连接池10s之类没有被使用, 则释放
	};
};

const seq = new Sequelize(database, user, password, conf);
module.exports = seq;

Test connection

// 测试连接
seq.authenticate().then(() => {
    console.log('auth ok')
}).catch(() => {
    console.log('auth err')
})

Sync Database

// 执行同步
seq.sync({ force: true }).then(() => {
    console.log('sync ok')
    process.exit()
})

Operation of database using Sequelize

Creating a table

// 创建 user 模型。注意此处数据表的名字是 users (会默认加上s)
const User = seq.define("user", {
  // id 主键会自动创建 并设为主键 自增
  userName: {
    type: STRING,
    allowNull: false,
    unique: true,
    comment: "用户名，唯一",
  },
  password: {
    type: STRING,
    allowNull: false,
    comment: "密码",
  },
  nickName: {
    type: STRING,
    allowNull: false,
    comment: "昵称",
  },
  ...
});

foreighKey

const User = require("./User");
const Blog = require("./Blog");

// 外键关联
Blog.belongsTo(User, {
  foreighKey: "userId",
});

create / destroy / update

// 增 create
const result = await User.create({
    userName,
    password,
    nickName: nickName ? nickName : userName,
    gender,
  });
const data = result.dataValues;

// 删 destroy
const result = await User.destroy({
    where: {
      userName: 'tangyuan'
    },
  });
  // result 删除的行数
 return result > 0;

// 改 update
const result = await User.update({
  // 修改后的值
  userName: 'tangyuan1'
}, {
  where: {
    userName: 'tangyuan'
  },
});
return result[0] > 0; // 修改的行数

Search

// findOne
const result = await User.findOne({
    // 需要得到的列的属性
    attributes: ["id", "userName", "nickName", "picture", "city"],
    where: {
      userName: 'tangyuan'
    },
  });

// findAndCountAll (分页/查询总数/连表查询)
const result = await Blog.findAndCountAll({
    limit: pageSize, // 每页多少条
    offset: pageSize * pageIndex, // 跳过多少条
    order: [["id", "desc"]],
    include: [
      {
        model: User,
        attributes: ["userName", "nickName", "picture"],
        where: {
          userName: 'tangyuan'
        },
      },
    ],
  });

// findAll
const result = await Blog.findAll({
  limit: 2,
  offset: 0,
  order:[ 
    ['id', 'desc']
  ]
})

Using Redis to store session

Configuration

// conf/db
let REDIS_CONF = {
  port: 6379,
  host: '127.0.0.1'
}

Use Redis to store session

const redisStore = require("koa-redis");
const session = require("koa-generic-session");

// session 配置
app.keys = ['ujdsghuvygf$87987'];
app.use(
  session({
    key: "weibo.sid",
    prefix: "weibo:sess:",
    cookie: {
      path: "/",
      httpOnly: true,
      maxAge: 24 * 60 * 60 * 1000,
    },
    ttl: 24 * 60 * 60 * 1000, // 可以不写，默认和maxAge保持一致
    // 存储到redis中
    store: redisStore({
      all: `${REDIS_CONF.host}:${REDIS_CONF.port}`,
    }),
  })
);

Using session

// controller
async function login(ctx, userName, password) {
  // 获取用户信息
  const userInfo = await getUserInfo(userName, doCrypto(password));
  if (!userInfo) {
    // 登录失败
    return new ErrorModel(loginFailInfo);
  }

  // 登录成功
  if (ctx.session.userInfo == null) {
    ctx.session.userInfo = userInfo;
  }
  return new SuccessModel();
}

async function logout(ctx) {
  delete ctx.session.userInfo;
  return new SuccessModel();
}

async function loginCheck(ctx, next) {
  if (ctx.session && ctx.session.userInfo) {
    // 已登录
    await next();
    return;
  }
  // 未登录
  ctx.body = new ErrorModel(loginCheckFailInfo);
}