使用Koa2搭建web項目
隨着Node.js的日益火熱，各種框架開始層出不窮的湧現出來，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瞭解下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。瞭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. 啓動入口文件
[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();
});
//end
app.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
}