将数据从 Node.js 发送回客户端

Posted 2023-02-16

【中文标题】将数据从 Node.js 发送回客户端

【英文标题】：Send data from Node.js back to Client

【发布时间】：2022-01-09 04:19:22

【问题描述】：

我有一个 ios React Native 应用程序，它使用 Node.js 程序从 Google Cloud 存储桶下载照片。我可以从特定文件夹中获取照片，但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!!!')
)

以下是正常工作的上传节点：

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)
)

以下是从 GCP 存储桶获取数据后发送数据的下载节点：

下载helpers.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)
)

以下是我从下载节点程序得到的数据：

[
   "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" 
]

我需要像在上传节点程序中那样使用 resolve(data) 发送数据，但我无法做到这一点。谁能建议如何做到这一点？提前致谢。

我正在控制台中获取 const 数据中的数据，我想将其在 resolve() 中发送回 index.js 中的 /file_download。在 Postman 中，当我运行“http://localhost:9001/file_download”时，出现以下错误：

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

我希望输出为

  "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在 React Native App 中显示图像。希望这很清楚。

【问题讨论】：

请不要使用图片来传达代码或错误信息。 Here's why.

是的..我编辑了这个问题。

您能否描述一下与您的预期结果相比的实际结果？看起来你有一些代码试图做你想做的事。所以发生了什么事？什么地方出了错？为什么你“做不到”？

我在上面的问题中补充了几点，我打算做什么。谢谢

我建议您在有catch (error) 的地方添加代码以立即执行console.error(error)，这样您就可以看到异常是什么。

【参考方案1】：

我刚刚从 downloadhelpers.js 中删除了最后三行，它工作正常。

下面是正确的下载节点。

下载helpers.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)
   )
   )

下面是 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"
    
  ]