Koa代理Http请求的示例代码

Koa 代理http请求，解决跨域问题

1、为什么用Koa做跨域代理？

"最初为了解决跨域问题，我把站点部署到了nginx上就解决了问题。一次偶然的面试机会，面试官提出了一个假设我需要对提交api和api返回的数据进行适配，那么nginx是不是就无法满足了。当然这个问题的提出，让我考虑到其实如果自己搭一个站点，通过这个站点进行转发，适配第三方api的请求和应答不就好了。那么要搭一个站点的语言其实有很多，例如.net,java,nodejs,php...，那为什么最后选择nodejs呢？对于我来说最重要的原因，应该就是nodejs的轻量级和javascript语言亲和性。

2、搭建nodejs应用

由于Koa2刚出，毕竟学技术，那么就学最新的。

既然搭建程序那么就从程序的入口开始做，首先写程序的路由

const fs = require('fs')
const Router = require('koa-router');
const {httpHandle} = require('../Infrastructure/httpHandle');
const koaBody = require('koa-body')({
  multipart :true
});

const render = (page) => {
  return new Promise((resolve, reject) => {
    let viewUrl = `./view/${page}`
    fs.readFile(viewUrl, "binary", (err, data) => {
      if (err) {
        reject(err)
      } else {
        resolve(data)
      }
    })
  })
}

let api = new Router();

api.get('*', httpHandle)
  .post('*', koaBody, httpHandle)
  .put('*', koaBody, httpHandle).del('*', koaBody, httpHandle);

let common = new Router();
common.get('*', async (ctx) => {
  ctx.body = await render('index.html');
})

let router = new Router();
router.use('/api', api.routes(), api.allowedMethods());
router.use('/', common.routes(), common.allowedMethods());
module.exports = router;

其次就是处理代理的请求

const httpRequest = (ctx) => {
  return new Promise((resolve) => {
    delete ctx.request.header.host;
    const options = {
      host,
      port,
      path: ctx.request.url.substr(4, ctx.request.url.length),
      method: ctx.request.method,
      headers: ctx.request.header
    }
    let requestBody='',
      body,
      head,
      chunks = [],
      fileFields,
      files,
      boundaryKey,
      boundary,
      endData,
      filesLength,
      totallength = 0;

    if (ctx.request.body) {
      console.log(ctx.request.header['content-type'])
      if (ctx.request.header['content-type'].indexOf('application/x-www-form-urlencoded') > -1) {
        requestBody = query.stringify(ctx.request.body);
        options.headers['Content-Length'] = Buffer.byteLength(requestBody)
      } else if (ctx.request.header['content-type'].indexOf('application/json') > -1) {
        requestBody = JSON.stringify(ctx.request.body);
        options.headers['Content-Length'] = Buffer.byteLength(requestBody)
      } else if (ctx.request.header['content-type'].indexOf('multipart/form-data') > -1) {
        fileFields = ctx.request.body.fields;
        files = ctx.request.body.files;
        boundaryKey = Math.random().toString(16);
        boundary = `\r\n----${boundaryKey}\r\n`;
        endData = `\r\n----${boundaryKey}--`;
        filesLength = 0;

        Object.keys(fileFields).forEach((key) => {
          requestBody += `${boundary}Content-Disposition:form-data;name="${key}"\r\n\r\n${fileFields[key]}`;
        })

        Object.keys(files).forEach((key) => {
          requestBody += `${boundary}Content-Type: application/octet-stream\r\nContent-Disposition: form-data; name="${key}";filename="${files[key].name}"\r\nContent-Transfer-Encoding: binary\r\n\r\n`;
          filesLength += Buffer.byteLength(requestBody,'utf-8') + files[key].size;
        })

        options.headers['Content-Type'] = `multipart/form-data; boundary=--${boundaryKey}`;
        options.headers[`Content-Length`] = filesLength + Buffer.byteLength(endData);
      } else {
        requestBody = JSON.stringify(ctx.request.body)
        options.headers['Content-Length'] = Buffer.byteLength(requestBody)
      }
    }

    const req = http.request(options, (res) => {
      res.on('data', (chunk) => {
        chunks.push(chunk);
        totallength += chunk.length;
      })

      res.on('end', () => {
        body = Buffer.concat(chunks, totallength);
        head = res.headers;
        resolve({head, body});
      })
    })

    ctx.request.body && req.write(requestBody);

    if (fileFields) {
      let filesArr = Object.keys(files);
      let uploadConnt = 0;
      filesArr.forEach((key) => {
        let fileStream = fs.createReadStream(files[key].path);
        fileStream.on('end', () => {
          fs.unlink(files[key].path);
          uploadConnt++;
          if (uploadConnt == filesArr.length) {
            req.end(endData)
          }
        })
        fileStream.pipe(req, {end: false})
      })
    } else {
      req.end();
    }

  })
}

由此简单的几行代码就实现了通过nodejs实现跨域的请求代理。 github链接

nginx代理config配置 如下

server {
   listen     1024; 
   server_name   tigrex:1024;
   root      home/TuoTuo.v2.UI;
   index      index.html;
   access_log   logs/tigrex.access.log;
   error_log    logs/tigrex.error.log;

   charset     utf-8;
   
   location /api {
     proxy_pass  http://127.0.0.1:1023/;
     proxy_set_header Host $host;
     proxy_redirect off;
     proxy_set_header X-Real-IP $remote_addr;
     proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
   }  
   
   location / {
     try_files $uri $uri/ /index.html;     
    }
  }

本文Koa代理Http请求的示例代码到此结束。上游，是勇士劈风破浪的终点；下游，是懦夫一帆风顺的归宿。小编再次感谢大家对我们的支持！