使用Node.js中的Promise从s3存储桶下载图像 [英] Download images from s3 bucket using Promise in node.js

问题描述

我想使用node.js中的Promises从本地系统的s3存储桶中下载一些图像文件.

I want to download some image files from s3 bucket on my local system using Promises in node.js.

var params = {
    Bucket: bucket_name',
    Key: 'key'
};

var fileStream = fs.createWriteStream('path/to/file.jpg');

我尝试了这个可行的方法

I tried this which is working

s3.getObject(params).createReadStream.pipe(fileStream);

但是我希望我的代码看起来像这样

But I want my code look like this

return s3.getObject(params).promise()
    .then(function(data) {
        //console.log(data.Body);
        // No idea about this section
    })
    .catch(function(err) {
        throw err;
    });

我必须使用Promise来确保应该下载所有图像.

I have to use Promise to ensure all images should be downloaded.

推荐答案

一种可能的解决方案是使用bluebird并创建一个在流的末尾返回promise的函数:

One possible solution is to use bluebird and create a function that returns a promise on the end of the stream:

const B = require('bluebird');

function downloadFromS3 (object) {
    var p = B.Promise.defer();

    var stream = s3.getObject(params).createReadStream()

    stream.pipe(fileStream);

    stream.on('error', (e) => p.reject(e))

    stream.on('end', () => p.resolve())

    return p.promise;
}

downloadFromS3(params)
    .then(() => console.log('finished'))
    .catch(() => console.log('failed'))

不确定此代码是否特别有用，但可能会为您提供指导.

Not sure if this code specifically would work, but it may give you a direction to look into.

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