随着node.js的日益火热，各种框架开始层出不穷的涌现出来，node.js也开始逐渐的被应用到处理服务端请求的场景中。搭建web项目的框架也随之开始出现——express、koa、koa2、egg等，当然要了解其好坏还是要自己去啃源码的。本文将不会涉及到源码，只是带领初学者简单了解下koa2的基本使用，欢迎大家在评论中互相交流学习。
注意：koa2使用了es7的语法，所以使用时请升级node版本到最新。了解更详细的源码信息可以到去了解
1. 项目目录结构
2. 代码逻辑解析
2.1. 包结构文件
[package.json]
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{
"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. 启动入口文件
[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);
如果请求的报文体是xml格式，可以添加下面的代码自动解析报文（注意引用koa-xxx的版本要与koa2对应）
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数据请求单独解析存储
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);
从代码看到引入了一个router2controller.js的文件，这个文件是完成前端请求到具体处理方法的路由过程
2.3. 路由器文件
[router2controller.js]
该类将会自动扫描controller文件夹中的文件来加载请求映射，不需要挨个请求单独配置
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
});
自动扫描controller包实现方法如下
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是用来处理具体请求信息以及返回数据的，usercontroller.js中处理了get请求获取用户信息，post请求保存用户信息
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数据处理
console.log(requeststring);
};
module.exports = {
'get /getuserinfo': getuserinfo,
'post /saveuserinfo': saveuserinfo
};
2.5. 数据处理
[userservice.js]
处理封装从***dao.js获取到的数据返回给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 += '年龄：' + user.age + ' |';
reaponsecontent += '身高：' + user.height + '<br />';
}
return responsecontent;
}
module.exports = {
getuserbyid : getuserbyid
};
2.6. 数据获取
[userdao.js]
通过请求传入参数来获取user数据
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. 数据库操作
[mysqlutil.js]
包含了数据库连接池控制，连接建立、释放管理，执行dao发起的数据库操作请求
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内容，希望对大家的学习有所帮助，也希望大家多多支持移动技术网。
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