为什么使用koa2搭建微信第三方公众平台的原因

======tool.js=====//截获微信返回的xml流文件const Promise = require('bluebird');//普通post流转化为promisevar Tool = {  convertPost: function(req) {    let post_data = "";    return new Promise(function(resolve, reject){      req.on('data', function(chunk) {        post_data += chunk;      });      req.on('end', function() {        resolve(post_data);      });    });  },};module.exports = Tool;=====weichat.js======//微信响应主体文件const router = require('koa-router')();const parseMessage = require('../common/parseMessage');const config = require('../config');const WXBizMsgCrypt = require('wechat-crypto');const middleware = require('../model/middleware');const validator = require('validator');const Aes = require('../common/aes');const Tool = require('../common/tool');const cryptor = new WXBizMsgCrypt(config.component_config.token, config.component_config.key, config.component_config.component_appid);//第三方授权路径 /:appid/callback  /wechat/100234/callbackrouter.post('/:appid/callback', async function(ctx, next) {  let post_data = "";  let req = ctx.req;  post_data = await Tool.convertPost(req);  let xml = parseMessage(post_data);  let signature = cryptor.getSignature(ctx.query.timestamp, ctx.query.nonce, xml.encrypt);  if (ctx.query.msg_signature != signature) {    ctx.body = 'Auth failed!'; // 指纹码不匹配时返回错误信息，禁止后面的消息接受及发送  }  let message = middleware.decryptXml(xml);  let appid = ctx.params.appid;  message.appId = appid;  //发送消息队列  switch (message.msgType) {    case 'text':      //测试      if (message.toUserName == "gh_3c884a361561") {        if (message.content == "TESTCOMPONENT_MSG_TYPE_TEXT") {          let text = middleware.text(message, message.content + "_callback");          let reply = middleware.encryptXml(text);          return ctx.body = reply;        }        let content = message.content;        if (content.indexOf("QUERY_AUTH_CODE") != -1) {          ctx.body = "";          let code_li = content.split(":");          await middleware.customSend(message.fromUserName, code_li[1]);          return;        }      }      let keywords = validator.trim(message.content).toLowerCase();      let member_config = await middleware.getMemberConfig(message.toUserName, keywords);      if (!member_config) {        await middleware.sendMnsQuene(message);        return ctx.body = "success";      }else{         //匹配成功        message.packetsId = parseInt(member_config.hongbaoId);        message.keywords = keywords;        await middleware.sendMnsQuene(message);        let data = {          title: member_config.news_title || '点我领红包',          description: member_config.description || '第一轮红包雨开始了,手快有,手慢无！',          picurl: member_config.picurl || 'http://7xqomp.com2.z0.glb.qiniucdn.com/17269743.png'        };        let key = {          fromUserName: message.fromUserName,          toUserName: message.toUserName,          keywords: keywords,          appId: appid        };        key = JSON.stringify(key);        key = Aes.encypt(key);        key = Aes.base64_encode(key);        //获取授权域名        let auth_url = await middleware.packetDomain();        data.url = "http://" + appid + "." + auth_url + "/redPackets/koulin?key=" + key;        let news = middleware.news(message, [data]);        let reply = middleware.encryptXml(news);        ctx.body = reply;         return;             }      break;    case 'event':      await middleware.sendMnsQuene(message);      //测试专用      if (message.toUserName == "gh_3c884a361561") {        let text = middleware.text(message, message.event + "from_callback");        let reply = middleware.encryptXml(text);        ctx.body = reply;        return;      }      break;    default:      await middleware.sendMnsQuene(message);      ctx.body = "success";      return;  };});module.exports = router;