将数据从Node.js发送回客户端

Question

我有一个IOS反应原生应用程序，使用Node.js程序下载照片从谷歌云桶。我可以从特定的文件夹中获取照片，但我无法将它们发送回客户。下面是客户端Node.js程序：

index.js

const express = require('express')
const bodyParser = require('body-parser')
const multer = require('multer')
const uploadImage = require('./helpers/helpers')
const downloadImage = require('./helpers/downloadhelpers');

const app = express()

const multerMid = multer({
  storage: multer.memoryStorage(),
  limits: {
    // no larger than 5mb.
    fileSize: 25 * 1024 * 1024,
    //fileSize: maxSize
  },
})

app.disable('x-powered-by')
app.use(multerMid.single('file'))
app.use(bodyParser.json())
app.use(bodyParser.urlencoded({
  extended: false
}))

app.post('/uploads', async (req, res, next) => {
  try {
    const myFile = req.file
    const destination = req.body.folder_name;

    const imageUrl = await uploadImage(myFile, destination)
    res
      .status(200)
      .json({
        message: "Upload was successful",
        data: imageUrl
      })
  } catch (error) {
    next(error)
  }
})

app.get('/file_download', async (req, res, next) => {
  const folder_name = req.body.folder_name;
  try {
    const ImageDownload = await downloadImage(folder_name)
    console.log(ImageDownload);
    res
      .status(200)
      .json({
        message: "Download Successful",
        data: ImageDownload
      })
  } catch (error) {
    next(error)
  }
})

app.use((err, req, res, next) => {
  res.status(500).json({
    error: err,
    message: 'Internal server error!',
  })
  next()
})

app.listen(9001, () => {
  console.log('app now listening for requests!!!')
})

下面是upload节点，它可以很好地工作：

helpers.js

const util = require('util');
const gc = require('./../config')
const bucket = gc.bucket('jtg_app_bucket') // should be your bucket name

module.exports = uploadImage = (File, destination) => new Promise((resolve, reject) => {
  const {
    originalname,
    buffer
  } = File
  const folder_name = destination;
  console.log(folder_name);
  const blob = bucket.file(destination + '/' + originalname.replace(/ /g, "_"))
  const blobStream = blob.createWriteStream({
    resumable: false
  })
  blobStream.on('finish', () => {
      const publicUrl = util.format(
        `https://storage.googleapis.com/${bucket.name}/${folder_name.name}/${blob.name}`
      )
      resolve(publicUrl)
    })
    .on('error', () => {
      reject(`Unable to upload image, something went wrong`)
    })
    .end(buffer)
})

下图是从GCP bucket拉取后发送数据的下载节点：

downloadhelpers.js

module.exports = downloadImage = (FolderToDisplay) => new Promise((resolve, reject) => {
  const folder_name = FolderToDisplay;
  const {
    Storage
  } = require('@google-cloud/storage');
  var projectId = '*****************' // Your Google Cloud Platform project ID
  var keyFilename = './../UploadPhotosNode/config/keys.json'
  const storage = new Storage({
    keyFilename,
    projectId
  });
  var bucket = storage.bucket("gs://jtg_app_bucket");
  const bucketName = 'jtg_app_bucket';

  // The directory prefix to search for
  const prefix = folder_name + '/';

  // The delimiter to use
  const delimiter = '/';
  const options = {
    prefix: prefix,
  };

  bucket.getFiles(options).then(results => {
      const files = results[0];
      var resData = {
        success: true,
        images: {
          results: []
        }
      };
      files.forEach(file => {
        resData.images.results.push({
          uri: 'https://storage.googleapis.com/' + bucketName + '/' +
            file.name
        });
      })
      var stringified = JSON.stringify(resData);
      var only_images = JSON.parse(stringified);

      const data = only_images.images.results;
      console.log(data);
      resolve(data)

    })
    .on('error', () => {
      reject(`Unable to download images, something went wrong`)
    })
    .end(buffer)
})

下面是我从下载节点程序中获得的数据：

[
  { "uri": "https://storage.googleapis.com/jtg_app_bucket/device_6/image.jpg" },
  { "uri": "https://storage.googleapis.com/jtg_app_bucket/device_6/loved_it.jpg" }
]

我需要像在upload node程序中那样使用resolve(数据)发送数据，但我无法做到这一点。有谁能建议如何做到这一点吗？提前谢谢。

我正在控制台中获取const数据中的数据，我想在resolve()中将其发送回index.js中的/file_download。在Postman中，当我运行"http://localhost:9001/file_download"，我得到的错误是：

{
  "error": {},
  "message": "Internal server error!"
}

我希望输出结果为

{
  "message": "Download Successful",
  "data": [
    { "uri": "https://storage.googleapis.com/jtg_app_bucket/device_6/image.jpg" },
    { "uri": "https://storage.googleapis.com/jtg_app_bucket/device_6/loved_it.jpg" }
  ]
}

这样我就可以使用它来显示React Native App中的图像。希望这一点是清楚的。

Answer 1

我刚刚从downloadhelpers.js中删除了最后三行，它工作得很好。

下面是正确的下载节点。

downloadhelpers.js

module.exports = downloadImage = (FolderToDisplay) => new 
 Promise((resolve, reject) => {
const folder_name = FolderToDisplay;
const {Storage} = require('@google-cloud/storage');
var projectId = 'vast-service-281617' // Your Google Cloud Platform 
project ID
var keyFilename = './../UploadPhotosNode/config/keys.json' 
const storage = new Storage({keyFilename,projectId});
var bucket = storage.bucket("gs://jtg_app_bucket");
const bucketName = 'jtg_app_bucket';
// The directory prefix to search for
const prefix = folder_name+'/';
// The delimiter to use
const delimiter = '/';
const options = {
prefix: prefix,
};  

bucket.getFiles(options).then(results => {  
const files = results[0];
var resData = {
          success: true,
          images: {
             /*  id:[], */
              results: []
          }  
      }; 
  files.forEach(file => {
      
  resData.images.results.push({
   uri:'https://storage.googleapis.com/'+bucketName+'/' +file.name});
      
    }) 
   var stringified = JSON.stringify(resData);
   var only_images = JSON.parse(stringified);

   const data  = only_images.images.results; 

   console.log(data);
   resolve(data)
   })
   })

以下是Postman的结果：

{
"message": "Download Successful",
"data": [
    {
        "uri": 
     "https://storage.googleapis.com/jtg_app_bucket/device_6/image.jpg"
    },
    {
        "uri": 
   "https://storage.googleapis.com/jtg_app_bucket/device_6/loved_it.png"
    }
  ]
 }