koa项目基本架构

1.前期简单安装一些依赖（根据需要再添加）

npm init -y

npm install koa

npm install nodemon -D–开发依赖

npm install dotenv，可加载根目录下的.env文件，将里面的直接加载到环境变量里面process.env

npm install koa-router路由库

npm install koa-bodyparser：中间件，解析json数据

npm install mysql2连接数据库

2.文件目录拆分

src

app：主体部分 constants：放一些常量 controller：控制器，写一些逻辑操作，比如，获取我们输入的信息，再调用service中操作数据库的方法 middleware：中间件，比如验证授权、验证输入的账号密码是否正确/存在、验证token是否已过期等 router：路由层，在这个文件夹中写路由 service：service层，就是操作数据库的一些方法 utils：放一些可以用到的方法，比如读取文件的方法 main.js：程序的入口，这个入口，越简单越好 .env：一些不能写死的环境变量，比如，服务端口port，数据库的一些信息，抽离到这个文件中

3.写接口的步骤

习惯性依次的创建xxx.router.js、xxx.middleware.js、xxx.controller.js、xxx.service.js这几个文件，当然xxx.middleware.js这个可根据需求决定是否需要创建，或者引用已经创建好的中间件文件

事例如下：

（1）在router文件夹中创建文件，如：department.router.js

// 请求路径 中间件处理的 映射
const Router = require('koa-router');

// 中间件

// 具体的处理逻辑 增删改查
const {
  list,
  create,
  update,
  remove
} = require('../controller/department.controller');

// 前缀：
const deportmentRouter = new Router({
  prefix: '/api/department'
});

deportmentRouter.post('/', create);
deportmentRouter.get('/list', list);
deportmentRouter.patch('/:departmentId', update);
deportmentRouter.delete('/:departmentId', remove);

// 导出
module.exports = deportmentRouter;

（2）在middleware文件夹下创建auth.middleware.js文件
未进行鉴权
（3）在controller文件夹中创建文件，如：department.controller.js
const departmentService = require('../service/department.service')

class DepartmentController {

  async list(ctx, next) {
    // 1.获取数据(offset/size)
    const {
      offset,
      size
    } = ctx.query;

    // 2.查询列表
    const {
      result,
      count
    } = await departmentService.getDepartmentList(offset, size);
    
    ctx.body = {
      code: 200,
      data: result,
      totalCount: count[0].total
    };

  }

  async create(ctx, next) {
    // 获取用户请求传递的参数
    const department = ctx.request.body;

    // 查询数据库 -> 抽离到service
    const result = await departmentService.create(department);
    
    // 返回结果
    ctx.body = {
      code: 200,
      data: result
    };

  }

  async update(ctx, next) {
    const {
      departmentId
    } = ctx.params;
    const {
      departmentName,
      principal,
      adviser,
      departmentTotal
    } = ctx.request.body;

    const result = await departmentService.update(departmentName, principal, adviser, departmentTotal, departmentId);
    ctx.body = {
      code: 200,
      data: result
    };

  }

  async remove(ctx, next) {
    // 1.
    const {
      departmentId
    } = ctx.params;

    // 2.删除内容
    const result = await departmentService.remove(departmentId);
    
    ctx.body = {
      code: 200,
      data: result
    };

  }
}

module.exports = new DepartmentController();

（4）在service文件夹下创建department.service.js文件
const connection = require('../app/database');

class DeportmentService {
  async getDepartmentList(offset, size) {
    const statement = `
      SELECT 
        d.id id, d.department_name departmentName, d.principal principal, d.adviser adviser, d.department_total departmentTotal,  d.createAt createAt, d.updateAt updateAt
      FROM department d
      LIMIT ?, ?;
    `;

const state = `SELECT COUNT(*) total FROM department`;
const [result] = await connection.execute(statement, [offset, size]);

const [count] = await connection.execute(state);

return {
  result,
  count
};

  }

  async create(deportment) {
    const {
      departmentName,
      principal,
      adviser,
      departmentTotal
    } = deportment;

// 使用sql语句将user存储到数据库中
const statement = `INSERT INTO department (department_name, principal, adviser, department_total) VALUES (?, ?, ?, ?);`;
const result = await connection.execute(statement, [departmentName, principal, adviser, departmentTotal]);

return result[0];

  }

  async update(departmentName, principal, adviser, departmentTotal, deportmentId) {
    const statement = `UPDATE department SET department_name = ?, principal = ?, adviser = ?, department_total = ? WHERE id = ?;`;
    const [result] = await connection.execute(statement, [departmentName, principal, adviser, departmentTotal, deportmentId]);
    return result;
  }

  async remove(deportmentId) {
    const statement = `DELETE FROM department WHERE id = ?;`;
    const [result] = await connection.execute(statement, [deportmentId]);
    return result;
  }
}

module.exports = new DeportmentService();

4.app文件夹中的一些内容

（1）index.js
const Koa = require('koa');
// 导入bodyParser中间件，解析json
const bodyParser = require('koa-bodyparser')
// 导入错误信息处置方法
const errorHandler = require('./error-handle');
// 导入路由 升级版 动态加载路由
const useRoutes = require('../router');

const app = new Koa();

app.use(bodyParser());

useRoutes(app);

app.on('error', errorHandler);

module.exports = app;

（2）database.js
const mysql = require('mysql2');

const config = require('./config');

// 创建连接池，与数据库进行连接
const connections = mysql.createPool({
  host: config.MYSQL_HOST,
  port: config.MYSQL_PORT,
  database: config.MYSQL_DATABASE,
  user: config.MYSQL_USER,
  password: config.MYSQL_PASSWORD
});

// 测试
connections.getConnection((err, conn) => {
  // err为空即为成功
  conn.connect((err) => {
    if (err) {
      console.log("数据库连接失败", err)
    } else {
      console.log("数据库连接成功")
    }
  })
});

// 通过promise操作数据库 
module.exports = connections.promise();
（3）config.js
// 可加载根目录下的.env文件，将里面的直接加载到环境变量里面
const dotenv = require('dotenv');
const fs = require('fs');
const path = require('path');

dotenv.config();

module.exports = {
  APP_HOST,
  APP_PORT,
  MYSQL_HOST,
  MYSQL_PORT,
  MYSQL_DATABASE,
  MYSQL_USER,
  MYSQL_PASSWORD,
} = process.env;

（4）error-handle.js
const errorType = require('../constants/error-types');

const errorHandler = (error, ctx) => {
  let status, message;

  switch (error.message) {
    case errorType.NAME_OR_PASSWORD_IS_REQUIRED:
      status = 400; // Bad Request
      message = "用户名或者密码不能为空！";
      break;
    case errorType.USER_ALREADY_EXISTS:
      status = 409; //  Conflict 冲突
      message = "用户名已存在！";
      break;
    case errorType.USER_DOES_NOT_EXISTS:
      status = 400; // 参数错误
      message = "用户名不存在！";
      break;
    case errorType.PASSWORD_IS_INCORRENT:
      status = 400; // 参数错误
      message = "密码错误！";
      break;
    case errorType.UNAUTHORIZATION:
      status = 401; // 参数错误
      message = "无效的token！";
      break;
    case errorType.UNPERMISSION:
      status = 401; // 参数错误
      message = "你不具备操作权限！";
      break;
    default:
      status = 404;
      message = "NOT FOUND";
  }

  ctx.status = status;
  ctx.body = message;
}

module.exports = errorHandler;

5. .env文件中的内容

APP_HOST = http://localhost
APP_PORT = 9999

MYSQL_HOST = localhost
MYSQL_PORT = 3306 
MYSQL_DATABASE = kylinKoa 
MYSQL_USER = root 
MYSQL_PASSWORD = root

6.读取文件的方法

// 读取文件的工具方法
const fs = require('fs')
module.exports.getFileJsonData = (filePath) => {
  // 根据文件的路径, 读取文件的内容
  return new Promise((resolve, reject) => {
    fs.readFile(filePath, 'utf-8', (error, data) => {
      if(error) {
        // 读取文件失败
        reject(error)
      } else {
        // 读取文件成功
        resolve(data)
      }
    })
  })
}