基于标准的三层架构创建node端Api服务

基于标准的三层架构（Controller, Service, Model）可以创建一个简单的功能：用户注册。这将涉及到用户模型（User Model），用户服务（User Service），以及用户控制器（User Controller）。

总述传送门

1. Model: 用户模型（User Model）

文件路径: app/models/user.js

const Sequelize = require('sequelize');
const sequelize = require('../../config/database');

const User = sequelize.define('User', {
  username: {
    type: Sequelize.STRING,
    unique: true,
    allowNull: false
  },
  password: {
    type: Sequelize.STRING,
    allowNull: false
  }
});

module.exports = User;

2. Service: 用户服务（User Service）

文件路径: app/services/userService.js

const User = require('../models/user');

const createUser = async (username, password) => {
  try {
    const user = await User.create({ username, password });
    return user;
  } catch (error) {
    // 错误处理逻辑
    throw error;
  }
};

module.exports = {
  createUser
};

3. Controller: 用户控制器（User Controller）

文件路径: app/controllers/userController.js

const userService = require('../services/userService');

const register = async (ctx) => {
  const { username, password } = ctx.request.body;
  try {
    const user = await userService.createUser(username, password);
    ctx.body = { message: 'User created successfully', user };
  } catch (error) {
    ctx.status = 400;
    ctx.body = { message: error.message };
  }
};

module.exports = {
  register
};

4. 路由和应用程序入口

首先，创建一个简单的路由处理器。

文件路径: app/routes.js

const Router = require('koa-router');
const userController = require('./controllers/userController');

const router = new Router();

router.post('/register', userController.register);

module.exports = router;

然后，在应用程序入口文件中配置Koa应用。

文件路径: app.js

const Koa = require('koa');
const bodyParser = require('koa-bodyparser');
const router = require('./app/routes');
const sequelize = require('./config/database');

const app = new Koa();

// 中间件
app.use(bodyParser());
app.use(router.routes()).use(router.allowedMethods());

// 数据库连接
sequelize.sync()
  .then(() => {
    console.log('Database connected.');
  })
  .catch((err) => {
    console.error('Unable to connect to the database:', err);
  });

// 服务器启动
const port = 3000;
app.listen(port, () => {
  console.log(`Server is running on http://localhost:${port}`);
});

module.exports = app;

在这个示例中，创建了一个简单的用户注册功能，包括用户模型（User），用户服务（userService），和用户控制器（userController）。用户通过发送POST请求到/register路由来注册，其中包含他们的用户名和密码。服务层（userService）处理创建用户的逻辑，而模型层（User）定义了用户数据的结构。

本文所示的例子是一个基本的三层架构应用，展示了如何将不同的关注点（路由处理、业务逻辑、数据访问）分离。

English version

# Creating a Simple User Registration Feature Using the Standard Three-Tier Architecture (Controller, Service, Model)

This implementation involves a user model (User Model), user service (User Service), and user controller (User Controller).

[Overview Portal](https://juejin.cn/post/7324296963137830946)

### 1. Model: User Model

File Path: `app/models/user.js`

```javascript
const Sequelize = require('sequelize');
const sequelize = require('../../config/database');

const User = sequelize.define('User', {
  username: {
    type: Sequelize.STRING,
    unique: true,
    allowNull: false
  },
  password: {
    type: Sequelize.STRING,
    allowNull: false
  }
});

module.exports = User;

2. Service: User Service

File Path: app/services/userService.js

const User = require('../models/user');

const createUser = async (username, password) => {
  try {
    const user = await User.create({ username, password });
    return user;
  } catch (error) {
    // Error handling logic
    throw error;
  }
};

module.exports = {
  createUser
};

3. Controller: User Controller

File Path: app/controllers/userController.js

const userService = require('../services/userService');

const register = async (ctx) => {
  const { username, password } = ctx.request.body;
  try {
    const user = await userService.createUser

(username, password);
    ctx.body = { message: 'User created successfully', user };
  } catch (error) {
    ctx.status = 400;
    ctx.body = { message: error.message };
  }
};

module.exports = {
  register
};

4. Routing and Application Entry

First, create a simple route handler.

File Path: app/routes.js

const Router = require('koa-router');
const userController = require('./controllers/userController');

const router = new Router();

router.post('/register', userController.register);

module.exports = router;

Then, configure the Koa application in the application entry file.

File Path: app.js

const Koa = require('koa');
const bodyParser = require('koa-bodyparser');
const router = require('./app/routes');
const sequelize = require('./config/database');

const app = new Koa();

// Middleware
app.use(bodyParser());
app.use(router.routes()).use(router.allowedMethods());

// Database connection
sequelize.sync()
  .then(() => {
    console.log('Database connected.');
  })
  .catch((err) => {
    console.error('Unable to connect to the database:', err);
  });

// Server startup
const port = 3000;
app.listen(port, () => {
  console.log(`Server is running on http://localhost:${port}`);
});

module.exports = app;

In this example, a simple user registration functionality is

created, including a user model (User), user service (userService), and user controller (userController). Users register by sending a POST request to the /register route, which includes their username and password. The service layer (userService) handles the logic for creating the user, while the model layer (User) defines the structure of user data.

The example shown in this article is a basic three-tier architecture application that demonstrates how to separate different concerns (route handling, business logic, data access).