koa 基礎（二十三）封裝 DB 庫 --- 應用

1.根目錄/module/config.js

/**
 * 配置文件
 */
var app = {
  dbUrl: 'mongodb://127.0.0.1:27017/?gssapiServiceName=mongodb',
  dbName: 'koa'
}

module.exports = app;

2.根目錄/module/db.js

/**
 * DB庫
 */
var MongoClient = require('mongodb').MongoClient;
var Config = require('./config.js');

class Db {
  /**
   * 單例
   * 解決屢次實例化,實例不共享的問題
   */
  static getInstance() {
    if (!Db.instance) {
      Db.instance = new Db();
    }
    return Db.instance;
  }

  constructor() {
    this.dbClient = ''; /*屬性 存放db對象*/
    this.connect(); /*實例化的時候就鏈接數據庫*/
  }

  connect() { /*鏈接數據庫*/
    let _that = this;
    return new Promise((resolve, reject) => {
      if (!_that.dbClient) { /*解決數據庫屢次鏈接的問題*/
        MongoClient.connect(Config.dbUrl, (err, client) => {
          if (err) {
            reject(err);
          } else {
            _that.dbClient = client.db(Config.dbName);
            resolve(_that.dbClient);
          }
        })
      } else {
        resolve(_that.dbClient);
      }
    })
  }

  find(collectionName, json) {
    return new Promise((resolve, reject) => {
      this.connect().then((db) => {
        var result = db.collection(collectionName).find(json);
        result.toArray((err, docs) => {
          if (err) {
            reject(err);
            return;
          }
          resolve(docs);
        })
      })
    })
  }

  insert() {
    //
  }
}

module.exports = Db.getInstance();

3.根目錄/app.js

// 引入模塊
const Koa = require('koa');
const router = require('koa-router')(); /*引入是實例化路由 推薦*/
const render = require('koa-art-template');
const path = require('path');
const DB = require('./module/db.js');

// 實例化
let app = new Koa();

// 配置 koa-art-template 模板引擎
render(app, {
  root: path.join(__dirname, 'views'), // 視圖的位置
  extname: '.html', // 後綴名
  debug: process.env.NODE_ENV !== 'production' // 是否開啓調試模式
})

router.get('/', async (ctx) => {
  console.time('start1');
  let result = await DB.find('user', {});
  console.log(result);
  console.timeEnd('start1');

  await ctx.render('index', {
    list: {
      name: '張三'
    }
  });
})

router.get('/news', async (ctx) => {
  console.time('start2');
  let result = await DB.find('user', {});
  console.log(result);
  console.timeEnd('start2');

  ctx.body = '新聞頁面';
})

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

app.listen(3000);

.