Sequelize介绍

• 为了快捷开发,社区出现了一系列的ORM(Object Relational Mapping)类库
• ORM的字面意思为对象关系映射,它提供了概念性的、易于理解的模型化数据的方法。通过ORM,可以降低操作数据库的成本。开发者不需要通过编写SQL脚本来操作数据库,直接通过访问对象的方式来查询、更新数据。这样做极大地提升了开发效率,降低了开发门槛。缺点也很明显,不够高效
• 在Node.js中,一般采用Sequelize这个ORM类库来操作数据库.

const Sequelize = require('sequelize');
const sequelize = new Sequelize('databaseName', 'userName', 'password', {host:'localhost',  // 数据库服务地址dialect: 'mysql'   // SQL语言类型
});
sequelize.authenticate().then(()=>{console.log('Connected');
}).catch(err=>{console.error('Connect failed');
})

• 使用docker创建一个数据库.
  使用docker-compose.yml写配置文件如下:

version: '3.1'
services:mysql:image: mysqlcommand: --default-authentication-plugin=mysql_native_passwordrestart: alwaysenvironment:MTSQL_ROOT_PASSWORD: exampleports:- 3306:3306adminer:image: adminerrestart: alwaysports:- 8080:8080

使用如下命令生成docker

docker-compose up

连接数据库

const Sequelize = require('sequelize');
const sequelize = new Sequelize('数据库名称','用户名(默认:root)','密码(docker-compose.yml中设置的)', {host:'localhost',dialect: 'mysql'
});
sequelize.authenticate().then(()=>{console.log('Connected');
})
.catch(err=>{console.error('Connect failed', err);
})

定义模型

• 常用

const Category = sequelize.define('category', {id: Sequelize.UUID,   // 定义id字段,类型为UUIDname: Sequelize.STRING    // 定义name字段,类型为String
})

• 给模型加约束条件

const Project = sequelize.define('project', {name: {type: Sequelize.STRING,   // 定位类型为StringallowNull: false,   //不能为空unique： true   // 必须唯一,不允许重复},date: {type: Sequelize.DATE,defaultValue: Sequelize.NOW     // 设置为当前时间}
})

• 给字段定义Getter和Setter方法:

const Custom = sequelize.define('custom', {name: {type: Sequelize.STRING,get(){const title = this.getDataValue('title');return `${this.getDataValue('name')} (${titile}) `}},title: {title: Sequelize.STRING,set (val) {this.setDataValue('title', val.toUpperCase())}}
})

查询数据

• 查询所有
  await Product.findAll()

• 查询name和data字段
  await Project.findAll({ attributes: ['name', 'date'] })

在使用一个库的时候,可以先把库的方法包装以下,变成自己的库

• 在下面的栗子中,首先把Sequelize库中的API抽离出来,根据实际的业务变成自己项目的函数.通过按需的方式引入到业务中.
• 这样做利于维护,(例如,Sequelize库变化了,不需要整个项目寻找使用到该接口的函数,或者具体改变了,重新改变接口)

栗子

• 项目结构如下:
  
• 设计Customer表的类型,如下:
• /mysql/model/custom.js

const Sequelize = require('sequelize');
const sequelize = new Sequelize('custom', 'root', 'example', {dialect:'mysql'
});
// 定义Customer模型
const Customer = sequelize.define('customer',{id:{type: Sequelize.UUID,unique: true,primaryKey: true,allowNull: false},name: {type: Sequelize.STRING,allowNull: false},sex: {type: Sequelize.ENUM(['男','女']),allowNull: false},address:{type: Sequelize.STRING},email: {type: Sequelize.STRING,allowNull: false},phone: {type: Sequelize.STRING},country:{type: Sequelize.STRING},city: {type:Sequelize.STRING}
});

• 在/mysql/db.js中,对表的功能进行加工

const { Customer } = require('./model/custom');const { Op } = require('sequelize');
async function getAllCustomers() {return Customer.findAndCountAll({attributes: ['id', 'name', 'sex', 'fulladdress'],order: [['updatedAt', 'DESC']]})
}
async function getCustomerById(id) {return Customer.findById(id);
}async function getCustomerByName(name) {return Customer.findAll({where: {name: {[Op.like]: `${name}`}}})
}async function updateCustomer(id, customer) {const item = await getCustomerById(id)if (item) {return item.update(customer);} else {throw new Error('the customer with id ${id} is not exist');}
}async function createCustomer(customer) {return Customer.create(customer);
}async function deleteCustomer(id) {const customer = await getCustomerById(id);if (customer) {return customer.destroy();}
}

• 在/mysql/app.js中对对应的路由设置数据库的操作方法(路由层还未抽离出来)

const {getAllCustomers,getCustomerById,getCustomerByName,createCustomer,updateCustomer,deleteCustomer
} = require('./db');
const koa = require('koa');
const app = new koa();
const router = new require('koa-router')();
const bodyParser = require('koa-bodyparser');app.use(async (ctx, next) => {try {await next();} catch (ex) {// ctx.type = jsonMIME;ctx.body = {status: -1,message: ex.message}}
})router.get('/customer', async ctx => {const customers = await getAllCustomers();// ctx.type = jsonMIME;ctx.body = {status: 0,data: customers};
});router.get('/customer/:id', async ctx => {const customer = await getCUstomerById(ctx.params.id);// ctx.type = jsonMIME;ctx.body = {status: 0,data: customer};
});router.get('/customer/name/:name', async ctx => {const customer = await getCUstomerByName(ctx.params.name);// ctx.type = jsonMIME;ctx.body = {status: 0,data: customer};
});router.post('/customer', async ctx => {const customer = ctx.body;await createCustomer(customer);// ctx.type = jsonMIME;ctx.body = {status: 0};
});router.put('/customer/:id', async ctx => {const id = ctx.params.id;const customer = ctx.body;await updateCustomer(id, customer);// ctx.type = jsonMIME;ctx.body = {status: 0};
});router.delete('/customer/:id', async ctx => {await deleteCustomer(ctx.params.id);// ctx.type = jsonMIME;ctx.body = {stauts: 0};
});app.use(bodyParser());
app.use(router.routes());app.listen(3000, async () => {console.log('Server is running at http://localhost:3000');
})