Processing a server response of content-type application/json using node.js

Question

I have a server returning the following for a CURL request curl --insecure -i -F files=@test.png https://xxx.xx.xx.xxx/powerai-vision/api/dlapis/b06564c9-7c1e-4642-a5a6-490310563d49.

HTTP/1.1 200 OK
Server: nginx/1.15.5
Date: Mon, 04 Nov 2019 06:23:14 GMT
Content-Type: application/json
Content-Length: 3556
Connection: keep-alive
Vary: Accept-Encoding
X-Powered-By: Servlet/3.1
Access-Control-Allow-Origin: *
Access-Control-Allow-Headers: X-Auth-Token, origin, content-type,accept, authorization
Access-Control-Allow-Credentials: true
Access-Control-Allow-Methods: GET, POST, PUT, DELETE, OPTIONS, HEAD
Content-Language: en
X-Frame-Options: SAMEORIGIN
X-Content-Type-Options: nosniff
X-XSS-Protection: 1; mode=block
Strict-Transport-Security: max-age=15724800; includeSubDomains
{"webAPIId":"b06564c9-7c1e-4642-a5a6-490310563d49","imageUrl":"http://powerai-vision-service:9080/powerai-vision-api/uploads/temp/b06564c9-7c1e-4642-a5a6-490310563d49/58c6eb6a-aaa4-4d6b-8c20-aadec4558107.png","imageMd5":"bd123739171d95d30d570b2cd0ed1aed","classified":[{"confidence":0.997600257396698,"ymax":997,"label":"white_box","xmax":1407,"xmin":1166,"ymin":760,"attr":[{}]},],"result":"success"}

I want to build a web app using node.js to process this and get the json string at the end. I am using the following code for this purpose.

'use strict';
/* eslint-env node */

const express = require('express');
const request = require('request');
const MISSING_ENV =
  'Missing required runtime environment variable POWERAI_VISION_WEB_API_URL';

require('dotenv').config({
  silent: true,
});

const app = express();
const port = process.env.PORT || process.env.VCAP_APP_PORT || 8081;
const poweraiVisionWebApiUrl = process.env.POWERAI_VISION_WEB_API_URL;

console.log('Web API URL: ' + poweraiVisionWebApiUrl);

if (!poweraiVisionWebApiUrl) {
  console.log(MISSING_ENV);
}

app.use(express.static(__dirname));
app.use(express.json());

app.post('/uploadpic', function (req, result) {
  if (!poweraiVisionWebApiUrl) {
    console.log(MISSING_ENV);
    result.send({ data: JSON.stringify({ error: MISSING_ENV }) });
  } else {
    req.pipe(request.post({
      url: poweraiVisionWebApiUrl,
      agentOptions: {
        rejectUnauthorized: false,
      }
    }, function (err, resp, body) {
      if (err) {
        console.log(err);
      }
      console.log('Check 22');
      console.log(body);
      // console.log(JSON.parse(body).webAPIId);
      result.send({ data: body });
    }));
  }
});

app.listen(port, () => {
  console.log(`Server starting on ${port}`);
});

The issue I have is I don't know how to access the elements in the body (the json strong). Right now console.log(body) prints garbage (https://github.com/IBM/powerai-vision-object-detection/issues/61). What is the correct way to process this string in node.js.

I am new to node.js programming.

When I print the header of the response I get the following output.

{
server: 'nginx/1.15.5',
date: 'Tue, 05 Nov 2019 02:47:37 GMT',
'content-type': 'application/json',
'transfer-encoding': 'chunked',
connection: 'keep-alive',
vary: 'Accept-Encoding',
'x-powered-by': 'Servlet/3.1',
'access-control-allow-origin': '*',
'access-control-allow-headers': 'X-Auth-Token, origin, content-type, accept, authorization',
'access-control-allow-credentials': 'true',
'access-control-allow-methods': 'GET, POST, PUT, DELETE, OPTIONS, HEAD',
'content-language': 'en',
'x-frame-options': 'SAMEORIGIN',
'x-content-type-options': 'nosniff',
'x-xss-protection': '1; mode=block',
'strict-transport-security': 'max-age=15724800; includeSubDomains',
'content-encoding': 'gzip'
}

It looks like the content encoding is gzip. Why is the curl out and the node.js response different? How should I process the gzip content? Any links?

Answer 1

It looks like you are parsing the JSON the right way.

But after looking at the screenshot you posted on github it seems you have a binary in the body instead of a JSON (an image maybe?). If I was you I would check if you are calling the API sending the correct parameters.

UPDATE:

After seeing the headers it looks that the response is still gzip-compressed, following this should solve your problem: https://gist.github.com/miguelmota/9946206

curl probably does it automatically for you, that's why you see the plain json, or maybe it's because the curl request has an header set that tells the server to not use gzip

UPDATE 2:

try making the request by adding gzip: true, it should do everything for you

 req.pipe(request.post({
   url: poweraiVisionWebApiUrl,
     gzip: true,
     agentOptions: {
       rejectUnauthorized: false,
     }
   }, function (err ...)