Help Center/ Object Storage Service/ SDK Reference/ Node.js/ Object Download (SDK for Node.js)/ Downloading an Object - Streaming (SDK for Node.js)
Updated on 2024-11-13 GMT+08:00
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Downloading an Object - Streaming (SDK for Node.js)

If you have any questions during development, post them on the Issues page of GitHub.

Function

This API downloads an object as a stream from OBS to your local computer.

Restrictions

Method

ObsClient.getObject(params)

Request Parameters

Table 1 List of request parameters

Parameter

Type

Mandatory (Yes/No)

Description

Bucket

string

Yes

Explanation:

Bucket name

Restrictions:

  • A bucket name must be unique across all accounts and regions.
  • A bucket name:
    • Must be 3 to 63 characters long and start with a digit or letter. Lowercase letters, digits, hyphens (-), and periods (.) are allowed.
    • Cannot be formatted as an IP address.
    • Cannot start or end with a hyphen (-) or period (.).
    • Cannot contain two consecutive periods (..), for example, my..bucket.
    • Cannot contain a period (.) and a hyphen (-) adjacent to each other, for example, my-.bucket or my.-bucket.
  • If you repeatedly create buckets with the same name in the same region, no error will be reported, and the bucket attributes comply with those set in the first creation request.

Value range:

The value can contain 3 to 63 characters.

Default value:

None

Key

string

Yes

Explanation:

Object name. An object is uniquely identified by an object name in a bucket. An object name is a complete path of the object that does not contain the bucket name.

For example, if the address for accessing the object is examplebucket.obs.eu-west-101.myhuaweicloud.com/folder/test.txt, the object name is folder/test.txt.

Restrictions:

None

Value range:

The value can contain 1 to 1,024 characters.

Default value:

None

VersionId

string

No

Explanation:

Object version ID, for example, G001117FCE89978B0000401205D5DC9A

Restrictions:

None

Value range:

The value must contain 32 characters.

Default value:

None

SaveAsFile

string

No

Explanation:

The download path with the file name contained

Restrictions:

A file name must be included in the path, for example, aa/bb.txt.

Value range:

None

Default value:

None

SaveAsStream

boolean

No

Explanation:

Whether the object is returned as a readable stream

Value range:

  • true: The object is returned as a readable stream.
  • false: The object is not returned as a readable stream.

Default value:

false

ProgressCallback

function

No

Explanation:

Callback function for obtaining the download progress

NOTE:

This callback function contains the following parameters in sequence: number of downloaded bytes, total bytes, and used time (unit: second).

Restrictions:

None

Value range:

None

Default value:

None

IfMatch

string

No

Explanation:

Preset ETag. If the ETag of the object to be downloaded is the same as the preset ETag, the object is returned. Otherwise, an error is returned.

Restrictions:

None

Value range:

The value must contain 32 characters.

Default value:

None

IfModifiedSince

string

No

Explanation:

If the object was modified after the time specified by this parameter, its content is returned. Otherwise, an error code is returned.

Restrictions:

The value must conform with the HTTP time format specified in http://www.ietf.org/rfc/rfc2616.txt.

Value range:

None

Default value:

None

IfNoneMatch

string

No

Explanation:

Preset ETag. If the ETag of the object to be downloaded is different from the preset ETag, the object is returned. Otherwise, an error is returned.

Restrictions:

None

Value range:

The value must contain 32 characters.

Default value:

None

IfUnmodifiedSince

string

No

Explanation:

If the object was modified before the time specified by this parameter, its content is returned. Otherwise, an error code is returned.

Restrictions:

The value must conform with the HTTP time format specified in http://www.ietf.org/rfc/rfc2616.txt.

Value range:

None

Default value:

None

Range

string

No

Explanation:

Download range. For example, 0-999 indicates the range is from byte 1 to byte 1000.

Restrictions:

The maximum length of Range is the length of the object minus 1. If the specified value exceeds this limit, the length of the object minus 1 is used.

Value range:

0 to the object length minus 1. Format: bytes=x-y

Default value:

None

Origin

string

No

Explanation:

Origin of the cross-domain request specified in the preflight request. It is usually a domain name.

Restrictions:

Each origin can contain at most one wildcard character (*).

Value range:

None

Default value:

None

RequestHeader

string

No

Explanation:

HTTP headers that can be used in cross-origin requests. Only CORS requests matching the allowed headers are valid.

Restrictions:

Each header can contain only one wildcard character (*). Spaces, ampersands (&), colons (:), less-than signs (<), and full-width characters are not allowed.

Value range:

None

Default value:

None

ResponseCacheControl

string

No

Explanation:

This parameter is used to rewrite the Cache-Control header in the response.

Restrictions:

None

Value range:

See the Cache-Control values defined in HTTP.

Default value:

None

ResponseContentDisposition

string

No

Explanation:

This parameter is used to rewrite the Content-Disposition header in the response.

Restrictions:

None

Value range:

See the Content-Disposition values defined in HTTP.

Default value:

None

ResponseContentEncoding

string

No

Explanation:

This parameter is used to rewrite the Content-Encoding header in the response.

Restrictions:

None

Value range:

See the Content-Encoding values defined in HTTP.

Default value:

None

ResponseContentLanguage

string

No

Explanation:

This parameter is used to rewrite the Content-Language header in the response.

Restrictions:

None

Value range:

See the Content-Language values defined in HTTP.

Default value:

None

ResponseContentType

string

No

Explanation:

This parameter is used to rewrite the Content-Type header in the response.

Restrictions:

None

Value range:

See What Is Content-Type (MIME)? (SDK for Node.js)

Default value:

None

ResponseExpires

string

No

Explanation:

This parameter is used to rewrite the Expires header in the response.

Restrictions:

None

Value range:

See the Expires values defined in HTTP.

Default value:

None

SseC

string

Yes when SSE-C is used

Explanation:

SSE-C is used for decrypting objects.

Restrictions:

Only AES256 is supported.

Value range:

AES256

Default value:

None

SseCKey

string

Yes when SSE-C is used

Explanation:

Key used for decrypting objects when SSE-C is used

Restrictions:

A Base64-encoded, 256-bit value, for example, K7QkYpBkM5+hca27fsNkUnNVaobncnLht/rCB2o/9Cw=

Value range:

None

Default value:

None
  • If a download request includes IfUnmodifiedSince or IfMatch but does not meet the conditions specified by these parameters, an exception is thrown with HTTP status code 412 Precondition Failed.
  • If a download request includes IfModifiedSince or IfNoneMatch but does not meet the conditions specified by these parameters, an exception is thrown with HTTP status code 304 Not Modified.

Responses

Table 2 Responses

Type

Description

Table 3

NOTE:

This API returns a Promise response, which requires the Promise or async/await syntax.

Explanation:

Returned results. For details, see Table 3.
Table 3 Response

Parameter

Type

Description

CommonMsg

ICommonMsg

Explanation:

Common information generated after an API call is complete, including the HTTP status code and error code. For details, see Table 4.

InterfaceResult

Table 5

Explanation:

Results outputted for a successful call. For details, see Table 5.

Restrictions:

This parameter is not included if the value of Status is greater than 300.
Table 4 ICommonMsg

Parameter

Type

Description

Status

number

Explanation:

HTTP status code returned by the OBS server.

Value range:

A status code is a group of digits indicating the status of a response. It ranges from 2xx (indicating successes) to 4xx or 5xx (indicating errors). For details, see Status Codes.

Code

string

Explanation:

Error code returned by the OBS server.

Message

string

Explanation:

Error description returned by the OBS server.

HostId

string

Explanation:

Request server ID returned by the OBS server.

RequestId

string

Explanation:

Request ID returned by the OBS server.

Id2

string

Explanation:

Request ID2 returned by the OBS server.

Indicator

string

Explanation:

Error code details returned by the OBS server.
Table 5 GetObjectOutput

Parameter

Type

Description

RequestId

string

Explanation:

Request ID returned by the OBS server

DeleteMarker

string

Explanation:

Whether the deleted object is a delete marker.

LastModified

string

Explanation:

Time when the object was last modified.

ContentLength

string

Explanation:

Object size

CacheControl

string

Explanation:

Cache-Control header in the response.

ContentDisposition

string

Explanation:

Content-Disposition header in the response

ContentEncoding

string

Explanation:

Content-Encoding header in the response

ContentLanguage

string

Explanation:

Content-Language header in the response

ContentType

string

Explanation:

MIME type of the object.

Expires

string

Explanation:

Expires header in the response

ETag

string

Explanation:

ETag of the object.

VersionId

string

Explanation:

Object version ID

WebsiteRedirectLocation

string

Explanation:

Location where an object is redirected. It is available when website hosting is configured for a bucket.

StorageClass

string

Explanation:

Object storage class. If the storage class is Standard, this parameter is left blank.

Restore

string

Explanation:

Restoration status of the object in the Archive storage class

Expiration

string

Explanation:

Expiration details

Content

string |

stream.Readable

Explanation:

Content of the object. The content is left blank if SaveAsFile was specified. The content is a stream.Readable object if SaveAsStream was set to true. The content is a Buffer object if neither SaveAsFile nor SaveAsStream was specified.

Metadata

object

Explanation:

Custom metadata of the object. You need to add in the CORS configurations the additional headers allowed to be carried in the response. For example, you can add the x-amz-meta-property1 header to allow custom metadata property1 to be returned.

Code Examples

This example downloads object examplebucket/objectname using the stream.

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// Import the OBS library.
// Use npm to install the client.
const ObsClient = require("esdk-obs-nodejs");
// Use the source code to install the client.
// var ObsClient = require('./lib/obs');

// Create an instance of ObsClient.
const obsClient = new ObsClient({
  // Obtain an AK/SK pair using environment variables or import an AK/SK pair in other ways. Using hard coding may result in leakage.
  // Obtain an AK/SK pair on the management console. For details, see https://support.huaweicloud.com/eu/usermanual-ca/ca_01_0003.html.
  access_key_id: process.env.ACCESS_KEY_ID,
  secret_access_key: process.env.SECRET_ACCESS_KEY,
  // (Optional) If you use a temporary AK/SK pair and a security token to access OBS, you are advised not to use hard coding, which may result in information leakage. You can obtain an AK/SK pair using environment variables or import an AK/SK pair in other ways.
  // security_token: process.env.SECURITY_TOKEN,
  // Enter the endpoint corresponding to the region where the bucket is located. EU-Dublin is used here in this example. Replace it with the one currently in use.
  server: "https://obs.eu-west-101.myhuaweicloud.eu"
});

async function getObject() {
  try {
    const params = {
      // Specify the bucket name.
      Bucket: "examplebucket",
      // Specify the object to download (example/objectname in this example).
      Key: 'example/objectname',
      // Specify that the object is returned as a stream (stream.Readable).
      SaveAsStream: true
    };
    
    // Download the object using the stream.
    const result = await obsClient.getObject(params);
    if (result.CommonMsg.Status <= 300) {
      console.log("Get object(%s) under the bucket(%s) successful!", params.Key, params.Bucket);
      console.log("RequestId: %s", result.CommonMsg.RequestId);
      console.log('Object Content:');
      result.InterfaceResult.Content.on('data', (data) => {
        console.log(data.toString());
      });
      return;
    };
    console.log("An ObsError was found, which means your request sent to OBS was rejected with an error response.");
    console.log("Status: %d", result.CommonMsg.Status);
    console.log("Code: %s", result.CommonMsg.Code);
    console.log("Message: %s", result.CommonMsg.Message);
    console.log("RequestId: %s", result.CommonMsg.RequestId);
  } catch (error) {
    console.log("An Exception was found, which means the client encountered an internal problem when attempting to communicate with OBS, for example, the client was unable to access the network.");
    console.log(error);
  };
};

getObject();