getObject method

Future<GetObjectOutput> getObject({ required String bucket, required String key, String? expectedBucketOwner, String? ifMatch, DateTime? ifModifiedSince, String? ifNoneMatch, DateTime? ifUnmodifiedSince, int? partNumber, String? range, RequestPayer? requestPayer, String? responseCacheControl, String? responseContentDisposition, String? responseContentEncoding, String? responseContentLanguage, String? responseContentType, DateTime? responseExpires, String? sSECustomerAlgorithm, Uint8List? sSECustomerKey, String? sSECustomerKeyMD5, String? versionId, })

Retrieves objects from Amazon S3. To use GET, you must have READ access to the object. If you grant READ access to the anonymous user, you can return the object without using an authorization header.

An Amazon S3 bucket has no directory hierarchy such as you would find in a typical computer file system. You can, however, create a logical hierarchy by using object key names that imply a folder structure. For example, instead of naming an object sample.jpg, you can name it photos/2006/February/sample.jpg.

To get an object from such a logical hierarchy, specify the full key name for the object in the GET operation. For a virtual hosted-style request example, if you have the object photos/2006/February/sample.jpg, specify the resource 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 resource as /examplebucket/photos/2006/February/sample.jpg. For more information about request types, see HTTP Host Header Bucket Specification.

To distribute large files to many people, you can save bandwidth costs by using BitTorrent. For more information, see Amazon S3 Torrent. For more information about returning the ACL of an object, see GetObjectAcl.

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

Encryption request headers, like x-amz-server-side-encryption, should not be sent for GET requests if your object uses server-side encryption with CMKs stored in AWS KMS (SSE-KMS) or server-side encryption with Amazon S3–managed encryption keys (SSE-S3). If your object does use these types of keys, you’ll get an HTTP 400 BadRequest error.

If you encrypt an object by using server-side encryption with customer-provided encryption keys (SSE-C) when you store the object in Amazon S3, then when you GET the object, you must use the following headers:

• x-amz-server-side-encryption-customer-algorithm
• x-amz-server-side-encryption-customer-key
• x-amz-server-side-encryption-customer-key-MD5

For more information about SSE-C, see Server-Side Encryption (Using Customer-Provided Encryption Keys).

Assuming you have permission to read object tags (permission for the s3:GetObjectVersionTagging action), the response also returns the x-amz-tagging-count header that provides the count of number of tags associated with the object. You can use GetObjectTagging to retrieve the tag set associated with an object.

Permissions

You need the s3:GetObject permission for this operation. For more information, see Specifying Permissions in a Policy. If the object you request does not exist, the error 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 will return an HTTP status code 404 ("no such key") error.
• If you don’t have the s3:ListBucket permission, Amazon S3 will return an HTTP status code 403 ("access denied") error.

Versioning

By default, the GET operation returns the current version of an object. To return a different version, use the versionId subresource. For more information about versioning, see PutBucketVersioning.

Overriding Response Header Values

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

You can override values for a set of response headers using the following query parameters. These response header values are sent only on a successful request, that is, when status code 200 OK is returned. The set of headers you can override using these parameters is a subset of the headers that Amazon S3 accepts when you create an object. The response headers that you can override for the GET response are Content-Type, Content-Language, Expires, Cache-Control, Content-Disposition, and Content-Encoding. To override these header values in the GET response, you use the following request parameters.

• response-content-type
• response-content-language
• response-expires
• response-cache-control
• response-content-disposition
• response-content-encoding

Additional Considerations about Request Headers

If both of the If-Match and If-Unmodified-Since headers are present in the request as follows: If-Match condition evaluates to true, and; If-Unmodified-Since condition evaluates to false; then, S3 returns 200 OK and the data requested.

If both of the If-None-Match and If-Modified-Since headers are present in the request as follows: If-None-Match condition evaluates to false, and; If-Modified-Since condition evaluates to true; then, S3 returns 304 Not Modified response code.

For more information about conditional requests, see RFC 7232.

The following operations are related to GetObject:

• ListBuckets
• GetObjectAcl

May throw NoSuchKey. May throw InvalidObjectState.

Parameter bucket : The bucket name containing the object.

When using this API with an access point, you must direct requests to the access point hostname. The access point hostname takes the form AccessPointName-AccountId.s3-accesspoint.Region.amazonaws.com. When using this operation with an access point through the AWS SDKs, you provide the access point ARN in place of the bucket name. For more information about access point ARNs, see Using Access Points in the Amazon Simple Storage Service Developer Guide.

When using this API with Amazon S3 on Outposts, you must direct requests to the S3 on Outposts hostname. The S3 on Outposts hostname takes the form AccessPointName-AccountId.outpostID.s3-outposts.Region.amazonaws.com. When using this operation using S3 on Outposts through the AWS SDKs, you provide the Outposts bucket ARN in place of the bucket name. For more information about S3 on Outposts ARNs, see Using S3 on Outposts in the Amazon Simple Storage Service Developer Guide.

Parameter key : Key of the object to get.

Parameter expectedBucketOwner : The account id of the expected bucket owner. If the bucket is owned by a different account, the request will fail with an HTTP 403 (Access Denied) error.

Parameter ifMatch : Return the object only if its entity tag (ETag) is the same as the one specified, otherwise return a 412 (precondition failed).

Parameter ifModifiedSince : Return the object only if it has been modified since the specified time, otherwise return a 304 (not modified).

Parameter ifNoneMatch : Return the object only if its entity tag (ETag) is different from the one specified, otherwise return a 304 (not modified).

Parameter ifUnmodifiedSince : Return the object only if it has not been modified since the specified time, otherwise return a 412 (precondition failed).

Parameter partNumber : Part number of the object being read. This is a positive integer between 1 and 10,000. Effectively performs a 'ranged' GET request for the part specified. Useful for downloading just a part of an object.

Parameter range : Downloads the specified range bytes of an object. For more information about the HTTP Range header, see https://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html#sec14.35.

Parameter responseCacheControl : Sets the Cache-Control header of the response.

Parameter responseContentDisposition : Sets the Content-Disposition header of the response

Parameter responseContentEncoding : Sets the Content-Encoding header of the response.

Parameter responseContentLanguage : Sets the Content-Language header of the response.

Parameter responseContentType : Sets the Content-Type header of the response.

Parameter responseExpires : Sets the Expires header of the response.

Parameter sSECustomerAlgorithm : Specifies the algorithm to use to when encrypting the object (for example, AES256).

Parameter sSECustomerKey : Specifies the customer-provided encryption key for Amazon S3 to use in encrypting data. This value is used to store the object and then it is discarded; Amazon S3 does not store the encryption key. The key must be appropriate for use with the algorithm specified in the x-amz-server-side-encryption-customer-algorithm header.

Parameter sSECustomerKeyMD5 : Specifies the 128-bit MD5 digest of the encryption key according to RFC 1321. Amazon S3 uses this header for a message integrity check to ensure that the encryption key was transmitted without error.

Parameter versionId : VersionId used to reference a specific version of the object.

Implementation

Future<GetObjectOutput> getObject({
  required String bucket,
  required String key,
  String? expectedBucketOwner,
  String? ifMatch,
  DateTime? ifModifiedSince,
  String? ifNoneMatch,
  DateTime? ifUnmodifiedSince,
  int? partNumber,
  String? range,
  RequestPayer? requestPayer,
  String? responseCacheControl,
  String? responseContentDisposition,
  String? responseContentEncoding,
  String? responseContentLanguage,
  String? responseContentType,
  DateTime? responseExpires,
  String? sSECustomerAlgorithm,
  Uint8List? sSECustomerKey,
  String? sSECustomerKeyMD5,
  String? versionId,
}) async {
  ArgumentError.checkNotNull(bucket, 'bucket');
  ArgumentError.checkNotNull(key, 'key');
  _s.validateStringLength(
    'key',
    key,
    1,
    1152921504606846976,
    isRequired: true,
  );
  final headers = <String, String>{
    if (expectedBucketOwner != null)
      'x-amz-expected-bucket-owner': expectedBucketOwner.toString(),
    if (ifMatch != null) 'If-Match': ifMatch.toString(),
    if (ifModifiedSince != null)
      'If-Modified-Since': _s.rfc822ToJson(ifModifiedSince),
    if (ifNoneMatch != null) 'If-None-Match': ifNoneMatch.toString(),
    if (ifUnmodifiedSince != null)
      'If-Unmodified-Since': _s.rfc822ToJson(ifUnmodifiedSince),
    if (range != null) 'Range': range.toString(),
    if (requestPayer != null) 'x-amz-request-payer': requestPayer.toValue(),
    if (sSECustomerAlgorithm != null)
      'x-amz-server-side-encryption-customer-algorithm':
          sSECustomerAlgorithm.toString(),
    if (sSECustomerKey != null)
      'x-amz-server-side-encryption-customer-key': sSECustomerKey.toString(),
    if (sSECustomerKeyMD5 != null)
      'x-amz-server-side-encryption-customer-key-MD5':
          sSECustomerKeyMD5.toString(),
  };
  final $query = <String, List<String>>{
    if (partNumber != null) 'partNumber': [partNumber.toString()],
    if (responseCacheControl != null)
      'response-cache-control': [responseCacheControl],
    if (responseContentDisposition != null)
      'response-content-disposition': [responseContentDisposition],
    if (responseContentEncoding != null)
      'response-content-encoding': [responseContentEncoding],
    if (responseContentLanguage != null)
      'response-content-language': [responseContentLanguage],
    if (responseContentType != null)
      'response-content-type': [responseContentType],
    if (responseExpires != null)
      'response-expires': [_s.rfc822ToJson(responseExpires).toString()],
    if (versionId != null) 'versionId': [versionId],
  };
  final $result = await _protocol.sendRaw(
    method: 'GET',
    requestUri:
        '/${Uri.encodeComponent(bucket)}/${key.split('/').map(Uri.encodeComponent).join('/')}',
    queryParams: $query,
    headers: headers,
    exceptionFnMap: _exceptionFns,
  );
  return GetObjectOutput(
    body: await $result.stream.toBytes(),
    acceptRanges:
        _s.extractHeaderStringValue($result.headers, 'accept-ranges'),
    bucketKeyEnabled: _s.extractHeaderBoolValue(
        $result.headers, 'x-amz-server-side-encryption-bucket-key-enabled'),
    cacheControl:
        _s.extractHeaderStringValue($result.headers, 'Cache-Control'),
    contentDisposition:
        _s.extractHeaderStringValue($result.headers, 'Content-Disposition'),
    contentEncoding:
        _s.extractHeaderStringValue($result.headers, 'Content-Encoding'),
    contentLanguage:
        _s.extractHeaderStringValue($result.headers, 'Content-Language'),
    contentLength:
        _s.extractHeaderIntValue($result.headers, 'Content-Length'),
    contentRange:
        _s.extractHeaderStringValue($result.headers, 'Content-Range'),
    contentType: _s.extractHeaderStringValue($result.headers, 'Content-Type'),
    deleteMarker:
        _s.extractHeaderBoolValue($result.headers, 'x-amz-delete-marker'),
    eTag: _s.extractHeaderStringValue($result.headers, 'ETag'),
    expiration:
        _s.extractHeaderStringValue($result.headers, 'x-amz-expiration'),
    expires: _s.extractHeaderDateTimeValue($result.headers, 'Expires'),
    lastModified:
        _s.extractHeaderDateTimeValue($result.headers, 'Last-Modified'),
    metadata: _s.extractHeaderMapValues($result.headers, 'x-amz-meta-'),
    missingMeta:
        _s.extractHeaderIntValue($result.headers, 'x-amz-missing-meta'),
    objectLockLegalHoldStatus: _s
        .extractHeaderStringValue(
            $result.headers, 'x-amz-object-lock-legal-hold')
        ?.toObjectLockLegalHoldStatus(),
    objectLockMode: _s
        .extractHeaderStringValue($result.headers, 'x-amz-object-lock-mode')
        ?.toObjectLockMode(),
    objectLockRetainUntilDate: _s.extractHeaderDateTimeValue(
        $result.headers, 'x-amz-object-lock-retain-until-date',
        parser: _s.timeStampFromJson),
    partsCount:
        _s.extractHeaderIntValue($result.headers, 'x-amz-mp-parts-count'),
    replicationStatus: _s
        .extractHeaderStringValue($result.headers, 'x-amz-replication-status')
        ?.toReplicationStatus(),
    requestCharged: _s
        .extractHeaderStringValue($result.headers, 'x-amz-request-charged')
        ?.toRequestCharged(),
    restore: _s.extractHeaderStringValue($result.headers, 'x-amz-restore'),
    sSECustomerAlgorithm: _s.extractHeaderStringValue(
        $result.headers, 'x-amz-server-side-encryption-customer-algorithm'),
    sSECustomerKeyMD5: _s.extractHeaderStringValue(
        $result.headers, 'x-amz-server-side-encryption-customer-key-MD5'),
    sSEKMSKeyId: _s.extractHeaderStringValue(
        $result.headers, 'x-amz-server-side-encryption-aws-kms-key-id'),
    serverSideEncryption: _s
        .extractHeaderStringValue(
            $result.headers, 'x-amz-server-side-encryption')
        ?.toServerSideEncryption(),
    storageClass: _s
        .extractHeaderStringValue($result.headers, 'x-amz-storage-class')
        ?.toStorageClass(),
    tagCount:
        _s.extractHeaderIntValue($result.headers, 'x-amz-tagging-count'),
    versionId:
        _s.extractHeaderStringValue($result.headers, 'x-amz-version-id'),
    websiteRedirectLocation: _s.extractHeaderStringValue(
        $result.headers, 'x-amz-website-redirect-location'),
  );
}