隨著Node.js的日益火熱，各種框架開始層出不窮的涌現出來，Node.js也開始逐漸的被應用到處理服務端請求的場景中。搭建Web項目的框架也隨之開始出現――express、koa、koa2、egg等，當然要了解其好壞還是要自己去啃源碼的。本文將不會涉及到源碼，只是帶領初學者簡單了解下Koa2的基本使用，歡迎大家在評論中互相交流學習。
注意：koa2使用了ES7的語法，所以使用時請升級Node版本到最新。了解更詳細的源碼信息可以到git上的koajs/koa去了解
1. 項目目錄結構
2. 代碼邏輯解析
2.1. 包結構文件
[package.json]
{ "name": "weixin-node-koa", "version": "1.0.0", "description": "node.js with koa2", "private": true, "dependencies": { "koa": "^2.0.0", "koa-router": "^7.0.0", "mysql":"2.13.0" }, "scripts": { "start": "node app.js" }, "engines": { "node": ">=6.0.0" }, "author": "Fly", "license": "CENTERM"}2.2. 啟動入口文件
[app.js]
const Koa = require('koa');const app = new Koa();const router2controller = require('./app/router2controller.js');const config = require('./config/config.local.js');app.use(router2controller());app.listen(config.port);console.log("Server started and listen on port " + config.port);如果請求的報文體是XML格式，可以添加下面的代碼自動解析報文（注意引用koa-xxx的版本要與koa2對應）
const Koa = require('koa');const app = new Koa();const router2controller = require('./app/router2controller.js');const config = require('./config/config.local.js');//start接收到的xml數據請求單獨解析存儲const xmlParser = require('koa-xml-body');app.use(xmlParser()).use((ctx,next) => { ctx.data = ctx.request.body; return next();});//endapp.use(router2controller());app.listen(config.port);console.log("Server started and listen on port " + config.port);從代碼看到引入了一個router2controller.js的文件，這個文件是完成前端請求到具體處理方法的路由過程
2.3. 路由器文件
[router2controller.js]
該類將會自動掃描controller文件夾中的文件來加載請求映射，不需要挨個請求單獨配置
koa-router原生提供方法如下：
router .get('/', async (ctx,next) => { this.body = 'Hello World!'; }) .post('/users', async (ctx,next) => { //TODO }) .put('/users/:id', async (ctx,next) => { //TODO }) .del('/users/:id', async (ctx,next) => { //TODO });自動掃描controller包實現方法如下
const fs = require('fs');const router = require('koa-router')();function addMapping(router, mapping) { for (var url in mapping) { if (url.startsWith('GET ')) { var path = url.substring(4); router.get(path, mapping[url]); console.log(`register URL mapping: GET ${path}`); } else if (url.startsWith('POST ')) { var path = url.substring(5); router.post(path, mapping[url]); console.log(`register URL mapping: POST ${path}`); } else if (url.startsWith('PUT ')) { var path = url.substring(4); router.put(path, mapping[url]); console.log(`register URL mapping: PUT ${path}`); } else if (url.startsWith('DELETE ')) { var path = url.substring(7); router.del(path, mapping[url]); console.log(`register URL mapping: DELETE ${path}`); } else { console.log(`invalid URL: ${url}`); } }}function addControllers(router, dir) { fs.readdirSync(__dirname + '/' + dir).filter((f) => { return f.endsWith('.js'); }).forEach((f) => { console.log(`process controller: ${f}...`); let mapping = require(__dirname + '/' + dir + '/' + f); addMapping(router, mapping); });}module.exports = function (dir) { var controllersDir = dir || 'controller'; addControllers(router, controllersDir); return router.routes();};2.4. 控制器
[userController.js]
***Controller.js是用來處理具體請求信息以及返回數據的，userController.js中處理了GET請求獲取用戶信息，POST請求保存用戶信息
const userService = require('./../service/userService.js');var getUserinfo = (ctx, next) => { let query = ctx.query; let userId = query.id; let userInfo = userService.getUserById(userId); let html = '<html><body>' + '<div> userinfo: ' + userInfo + '</div>' + '</body></html>'; ctx.response.type ='text/html'; ctx.response.body = html;};var saveUserinfo = (ctx, next) => { const requestString = ctx.data; //TODO數據處理 Console.log(requestString);};module.exports = { 'GET /getUserinfo': getUserinfo, 'POST /saveUserinfo': saveUserinfo};2.5. 數據處理
[userService.js]
處理封裝從***Dao.js獲取到的數據返回給Controller
const userDao = require('./../dao/userDao.js');var getUserById = async (userId) => { var users = userDao.getUserById(userId); var responseContent = ''; for(let user of users) { reaponseContent += '姓名：' + user.name + ' |'; reaponseContent += '年齡：' + user.age + ' |'; reaponseContent += '身高：' + user.height + '<br />'; } return responseContent;}module.exports = { getUserById : getUserById};2.6. 數據獲取
[userDao.js]
通過請求傳入參數來獲取user數據
const mysql = require('./../utils/mysqlUtil.js');var getUserById = async (userId) => { let mysqlOptions = { sql : 'select * from table_user where user_id = ?', args : [userId] }; var users = await mysql.execQuery(mysqlOptions); if(users.length == 0) { return null; } else { return users; }};module.exports = { getUserById : getUserById};2.7. 數據庫操作
[mysqlUtil.js]
包含了數據庫連接池控制，連接建立、釋放管理，執行Dao發起的數據庫操作請求
const mysql = require('mysql');const config = require('./../../config/config.local.js');var connectionPool = mysql.createPool({ 'host' : config.database.host, 'port':config.database.port, 'user' : config.database.user, 'password' : config.database.password, 'database' : config.database.database, 'charset': config.database.charset, 'connectionLimit': config.database.connectionLimit, 'supportBigNumbers': true, 'bigNumberStrings': true});var release = connection => { connection.end(function(error) { if(error) { console.log('Connection closed failed.'); } else { console.log('Connection closed succeeded.'); } });};var execQuery = sqlOptions => { var results = new Promise((resolve, reject) => { connectionPool.getConnection((error,connection) => { if(error) { console.log("Get connection from mysql pool failed !"); throw error; } var sql = sqlOptions['sql']; var args = sqlOptions['args']; if(!args) { var query = connection.query(sql, (error, results) => { if(error) { console.log('Execute query error !'); throw error; } resolve(results); }); } else { var query = connection.query(sql, args, function(error, results) { if(error) { console.log('Execute query error !'); throw error; } resolve(results); }); } connection.release(function(error) { if(error) { console.log('Mysql connection close failed !'); throw error; } }); }); }).then(function (chunk) { return chunk; }); return results;};module.exports = { release : release, execQuery : execQuery}以上就是本文的全部內容，希望對大家的學習有所幫助，也希望大家多多支持武林網。
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