如何从Node.js中的S3 getObject获得响应？

在一个Node.js项目中，我试图从S3取回数据。

当我使用时getSignedURL，一切正常：

aws.getSignedUrl('getObject', params, function(err, url){
    console.log(url); 
}); 

我的参数是：

var params = {
              Bucket: "test-aws-imagery", 
              Key: "TILES/Level4/A3_B3_C2/A5_B67_C59_Tiles.par"

如果将URL输出带到控制台并将其粘贴到Web浏览器中，它将下载所需的文件。

但是，如果我尝试使用，则会出现getObject各种奇怪的行为。我相信我只是使用不正确。这是我尝试过的：

aws.getObject(params, function(err, data){
    console.log(data); 
    console.log(err); 
}); 

输出：

{ 
  AcceptRanges: 'bytes',
  LastModified: 'Wed, 06 Apr 2016 20:04:02 GMT',
  ContentLength: '1602862',
  ETag: '9826l1e5725fbd52l88ge3f5v0c123a4"',
  ContentType: 'application/octet-stream',
  Metadata: {},
  Body: <Buffer 01 00 00 00  ... > }

  null

因此看来这工作正常。但是，当我在console.logs之一上设置断点时，我的IDE（NetBeans）会引发错误并拒绝显示数据值。尽管这可能只是IDE，但我还是决定尝试其他使用方式getObject。

aws.getObject(params).on('httpData', function(chunk){
    console.log(chunk); 
}).on('httpDone', function(data){
    console.log(data); 
});

这不会输出任何内容。放置一个断点表明代码永远不会到达console.logs中的任何一个。我也尝试过：

aws.getObject(params).on('success', function(data){
    console.log(data); 
});

但是，这也不会输出任何内容，并且放置断点表明console.log永远不会到达。

我究竟做错了什么？

当执行getObject()从S3 API，按照文档文件的内容都位于Body属性，您可以从您的样品输出看到。您应该具有类似于以下内容的代码

const aws = require('aws-sdk');
const s3 = new aws.S3(); // Pass in opts to S3 if necessary

var getParams = {
    Bucket: 'abc', // your bucket name,
    Key: 'abc.txt' // path to the object you're looking for
}

s3.getObject(getParams, function(err, data) {
    // Handle any error and exit
    if (err)
        return err;

  // No error happened
  // Convert Body from a Buffer to a String

  let objectData = data.Body.toString('utf-8'); // Use the encoding necessary
});

您可能不需要从data.Body对象创建新的缓冲区，但是如果需要，可以使用上面的示例来实现。

基于@peteb的答案，但使用Promises和Async/Await：

const AWS = require('aws-sdk');

const s3 = new AWS.S3();

async function getObject (bucket, objectKey) {
  try {
    const params = {
      Bucket: bucket,
      Key: objectKey 
    }

    const data = await s3.getObject(params).promise();

    return data.Body.toString('utf-8');
  } catch (e) {
    throw new Error(`Could not retrieve file from S3: ${e.message}`)
  }
}

// To retrieve you need to use `await getObject()` or `getObject().then()`
getObject('my-bucket', 'path/to/the/object.txt').then(...);

对于寻找NEST JS TYPESCRIPT上述版本的人：

    /**
     * to fetch a signed URL of a file
     * @param key key of the file to be fetched
     * @param bucket name of the bucket containing the file
     */
    public getFileUrl(key: string, bucket?: string): Promise<string> {
        var scopeBucket: string = bucket ? bucket : this.defaultBucket;
        var params: any = {
            Bucket: scopeBucket,
            Key: key,
            Expires: signatureTimeout  // const value: 30
        };
        return this.account.getSignedUrlPromise(getSignedUrlObject, params);
    }

    /**
     * to get the downloadable file buffer of the file
     * @param key key of the file to be fetched
     * @param bucket name of the bucket containing the file
     */
    public async getFileBuffer(key: string, bucket?: string): Promise<Buffer> {
        var scopeBucket: string = bucket ? bucket : this.defaultBucket;
        var params: GetObjectRequest = {
            Bucket: scopeBucket,
            Key: key
        };
        var fileObject: GetObjectOutput = await this.account.getObject(params).promise();
        return Buffer.from(fileObject.Body.toString());
    }

    /**
     * to upload a file stream onto AWS S3
     * @param stream file buffer to be uploaded
     * @param key key of the file to be uploaded
     * @param bucket name of the bucket 
     */
    public async saveFile(file: Buffer, key: string, bucket?: string): Promise<any> {
        var scopeBucket: string = bucket ? bucket : this.defaultBucket;
        var params: any = {
            Body: file,
            Bucket: scopeBucket,
            Key: key,
            ACL: 'private'
        };
        var uploaded: any = await this.account.upload(params).promise();
        if (uploaded && uploaded.Location && uploaded.Bucket === scopeBucket && uploaded.Key === key)
            return uploaded;
        else {
            throw new HttpException("Error occurred while uploading a file stream", HttpStatus.BAD_REQUEST);
        }
    }

或者，您可以使用minio-js客户端库 get-object.js

var Minio = require('minio')

var s3Client = new Minio({
  endPoint: 's3.amazonaws.com',
  accessKey: 'YOUR-ACCESSKEYID',
  secretKey: 'YOUR-SECRETACCESSKEY'
})

var size = 0
// Get a full object.
s3Client.getObject('my-bucketname', 'my-objectname', function(e, dataStream) {
  if (e) {
    return console.log(e)
  }
  dataStream.on('data', function(chunk) {
    size += chunk.length
  })
  dataStream.on('end', function() {
    console.log("End. Total size = " + size)
  })
  dataStream.on('error', function(e) {
    console.log(e)
  })
})

免责声明：我为Minio工作，它是开源的，与golang编写的S3兼容对象存储，并带有Java，Python，Js和golang中可用的客户端库。

乍一看，您似乎并没有做错任何事情，但是您并未显示所有代码。当我第一次检出S3和Node时，以下内容对我有用：

var AWS = require('aws-sdk');

if (typeof process.env.API_KEY == 'undefined') {
    var config = require('./config.json');
    for (var key in config) {
        if (config.hasOwnProperty(key)) process.env[key] = config[key];
    }
}

var s3 = new AWS.S3({accessKeyId: process.env.AWS_ID, secretAccessKey:process.env.AWS_KEY});
var objectPath = process.env.AWS_S3_FOLDER +'/test.xml';
s3.putObject({
    Bucket: process.env.AWS_S3_BUCKET, 
    Key: objectPath,
    Body: "<rss><data>hello Fred</data></rss>",
    ACL:'public-read'
}, function(err, data){
    if (err) console.log(err, err.stack); // an error occurred
    else {
        console.log(data);           // successful response
        s3.getObject({
            Bucket: process.env.AWS_S3_BUCKET, 
            Key: objectPath
        }, function(err, data){
            console.log(data.Body.toString());
        });
    }
});