IAmazonS3.GetObjectAsync (GetObjectRequest, CancellationToken)

Method

Retrieves an object from Amazon S3.

In the GetObject request, specify the full key name for the object.

General purpose buckets - Both the virtual-hosted-style requests and the path-style requests are supported. For a virtual hosted-style request example, if you have the object photos/2006/February/sample.jpg, specify the object key name as /photos/2006/February/sample.jpg. For a path-style request example, if you have the object photos/2006/February/sample.jpg in the bucket named examplebucket, specify the object key name as /examplebucket/photos/2006/February/sample.jpg. For more information about request types, see HTTP Host Header Bucket Specification in the Amazon S3 User Guide.

Directory buckets - Only virtual-hosted-style requests are supported. For a virtual hosted-style request example, if you have the object photos/2006/February/sample.jpg in the bucket named examplebucket--use1-az5--x-s3, specify the object key name as /photos/2006/February/sample.jpg. Also, when you make requests to this API operation, your requests are sent to the Zonal endpoint. These endpoints support virtual-hosted-style requests in the format https://bucket_name.s3express-az_id.region.amazonaws.com/key-name. Path-style requests are not supported. For more information, see Regional and Zonal endpoints in the Amazon S3 User Guide.

Permissions

• General purpose bucket permissions - You must have the required permissions in a policy. To use GetObject, you must have the READ access to the object (or version). If you grant READ access to the anonymous user, the GetObject operation returns the object without using an authorization header. For more information, see Specifying permissions in a policy in the Amazon S3 User Guide.

  If you include a versionId in your request header, you must have the s3:GetObjectVersion permission to access a specific version of an object. The s3:GetObject permission is not required in this scenario.

  If you request the current version of an object without a specific versionId in the request header, only the s3:GetObject permission is required. The s3:GetObjectVersion permission is not required in this scenario.

  If the object that you request doesn’t exist, the error that Amazon S3 returns depends on whether you also have the s3:ListBucket permission.

  • If you have the s3:ListBucket permission on the bucket, Amazon S3 returns an HTTP status code 404 Not Found error.

  • If you don’t have the s3:ListBucket permission, Amazon S3 returns an HTTP status code 403 Access Denied error.

• Directory bucket permissions - To grant access to this API operation on a directory bucket, we recommend that you use the CreateSession API operation for session-based authorization. Specifically, you grant the s3express:CreateSession permission to the directory bucket in a bucket policy or an IAM identity-based policy. Then, you make the CreateSession API call on the bucket to obtain a session token. With the session token in your request header, you can make API requests to this operation. After the session token expires, you make another CreateSession API call to generate a new session token for use. Amazon Web Services CLI or SDKs create session and refresh the session token automatically to avoid service interruptions when a session expires. For more information about authorization, see CreateSession.

Storage classes

If the object you are retrieving is stored in the S3 Glacier Flexible Retrieval storage class, the S3 Glacier Deep Archive storage class, the S3 Intelligent-Tiering Archive Access tier, or the S3 Intelligent-Tiering Deep Archive Access tier, before you can retrieve the object you must first restore a copy using RestoreObject. Otherwise, this operation returns an InvalidObjectState error. For information about restoring archived objects, see Restoring Archived Objects in the Amazon S3 User Guide.

Directory buckets - For directory buckets, only the S3 Express One Zone storage class is supported to store newly created objects. Unsupported storage class values won't write a destination object and will respond with the HTTP status code 400 Bad Request.

Encryption

Encryption request headers, like x-amz-server-side-encryption, should not be sent for the GetObject requests, if your object uses server-side encryption with Amazon S3 managed encryption keys (SSE-S3), server-side encryption with Key Management Service (KMS) keys (SSE-KMS), or dual-layer server-side encryption with Amazon Web Services KMS keys (DSSE-KMS). If you include the header in your GetObject requests for the object that uses these types of keys, you’ll get an HTTP 400 Bad Request error.

Overriding response header values through the request

There are times when you want to override certain response header values of a GetObject response. For example, you might override the Content-Disposition response header value through your GetObject request.

You can override values for a set of response headers. These modified response header values are included only in a successful response, that is, when the HTTP status code 200 OK is returned. The headers you can override using the following query parameters in the request are a subset of the headers that Amazon S3 accepts when you create an object.

The response headers that you can override for the GetObject response are Cache-Control, Content-Disposition, Content-Encoding, Content-Language, Content-Type, and Expires.

To override values for a set of response headers in the GetObject response, you can use the following query parameters in the request.

• response-cache-control

• response-content-disposition

• response-content-encoding

• response-content-language

• response-content-type

• response-expires

When you use these parameters, you must sign the request by using either an Authorization header or a presigned URL. These parameters cannot be used with an unsigned (anonymous) request.

HTTP Host header syntax

Directory buckets - The HTTP Host header syntax is Bucket_name.s3express-az_id.region.amazonaws.com.

The following operations are related to GetObject:

• ListBuckets

• GetObjectAcl

Namespace: Amazon.S3
Assembly: AWSSDK.S3.dll
Version: 3.x.y.z