Configuring Object Metadata (SDK for Node.js)

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Function

Object metadata contains a set of name-value pairs that are used for describing and managing objects.

Currently, only the system-defined metadata is supported. System-defined metadata consists of system-controlled metadata and user-controlled metadata.

This API sends a HEAD request for obtaining object metadata.

Restrictions

To obtain object metadata, you must be the bucket owner or have the required permission (obs:object:GetObject in IAM or GetObject in a bucket policy). For details, see Introduction to OBS Access Control, IAM Custom Policies, and Configuring an Object Policy.
Users with the READ permission for objects can send HEAD requests to retrieve object metadata, which is included in the response.

Method

ObsClient.setObjectMetadata(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.
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
MetadataDirective	MetadataDirectiveType	Yes	Explanation: Policy for copying the source object's attributes Restrictions: None Value range: See Table 7. Default value: None
VersionId	string	No	Explanation: Object version. Example: G001117FCE89978B0000401205D5DC9A Restrictions: None Value range: The value must contain 32 characters. Default value: None
CacheControl	string	No	Explanation: Cache-Control header in the response. It specifies the cache behavior of the web page when an object is downloaded. Restrictions: None Value range: See the Cache-Control values defined in HTTP. Default value: None
ContentDisposition	string	No	Explanation: Content-Disposition header in the response. It specifies the name of an object when it is downloaded. Restrictions: None Value range: See the Content-Disposition values defined in HTTP. Default value: None
ContentEncoding	string	No	Explanation: Content-Encoding header in the response. It specifies the content encoding format when an object is downloaded. Restrictions: None Value range: See the Content-Encoding values defined in HTTP. Default value: None
ContentLanguage	string	No	Explanation: Content-Language header in the response. It specifies what language the object content is in when being downloaded. Restrictions: None Value range: See the Content-Language values defined in HTTP. Default value: None
ContentType	string	No	Explanation: Content-Type header in the response. It specifies the file type of an object when it is downloaded. Restrictions: None Value range: See What Is Content-Type (MIME)? (SDK for Node.js) Default value: None
Expires	string	No	Explanation: Expires header in the response. It specifies the cache expiration time of the web page when the object is downloaded. Restrictions: None Value range: See the Expires values defined in HTTP. Default value: None
WebsiteRedirectLocation	string	No	Explanation: If the bucket is configured with website hosting, the request for obtaining the object can be redirected to another object in the bucket or an external URL. The request is redirected to object anotherPage.html in the same bucket: WebsiteRedirectLocation:/anotherPage.html The request is redirected to an external URL: WebsiteRedirectLocation:http://www.example.com/ OBS obtains the specified value from the header and stores it in the object metadata WebsiteRedirectLocation. Restrictions: The value must start with a slash (/), http://, or https:// and cannot exceed 2 KB. OBS only supports redirection of objects that are in the root directory. Value range: None Default value: None
StorageClass	StorageClassType	No	Explanation: Storage class of the object. Restrictions: None Value range: See Table 2. Default value: None
Metadata	object	No	Explanation: Custom metadata of the object. You can add a header starting with x-obs-meta- in the request to define metadata. The custom metadata will be returned in the response when you retrieve the object or query the object metadata. Restrictions: The custom metadata cannot exceed 8 KB in total. To measure the size, calculate the sum of bytes of all UTF-8 encoded keys and values. The custom metadata keys are case insensitive, but are stored in lowercase in OBS. The key values are case sensitive. Both custom metadata keys and their values must conform to US-ASCII standards. If non-ASCII or unrecognizable characters are required, they must be encoded and decoded in URL or Base64 on the client, because the server does not perform such operations. Value range: None Default value: None

**Table 2** StorageClassType
Constant	Default Value	Description
ObsClient.enums.StorageClassStandard	STANDARD	Standard storage class. Features low access latency and high throughput and is used for storing massive, frequently accessed (multiple times a month) or small objects (< 1 MB) requiring quick response.
ObsClient.enums.StorageClassWarm	WARM	Infrequent Access storage class. Used for storing data that is semi-frequently accessed (fewer than 12 times a year) but becomes instantly available when needed.
ObsClient.enums.StorageClassCold	COLD	Archive storage class. Used for storing rarely accessed (once a year) data.

Responses

**Table 3** Responses
Type	Description
Table 4 NOTE: This API returns a Promise response, which requires the Promise or async/await syntax.	Explanation: Returned results. For details, see Table 4.

**Table 4** 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 5.
InterfaceResult	Table 6	Explanation: Results outputted for a successful call. For details, see Table 6. Restrictions: This parameter is not included if the value of Status is greater than 300.

**Table 5** 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 6** SetObjectMetadataOutput
Parameter	Type	Description
RequestId	string	Explanation: Request ID returned by the OBS server
MetadataDirective	MetadataDirectiveType	Explanation: Policy for copying the source object's attributes Value range: See Table 7.
CacheControl	string	Explanation: Cache-Control header in the response. It specifies the cache behavior of the web page when an object is downloaded.
ContentDisposition	string	Explanation: Content-Disposition header in the response. It specifies the name of an object when it is downloaded.
ContentEncoding	string	Explanation: Content-Encoding header in the response. It specifies how the object is encoded when being downloaded.
ContentLanguage	string	Explanation: Content-Language header in the response. It specifies what language the object content is in when being downloaded.
ContentType	string	Explanation: Content-Type header in the response. It specifies the file type of an object when it is downloaded.
Expires	string	Explanation: Expires header in the response. It specifies the cache expiration time of the web page when the object is downloaded.
WebsiteRedirectLocation	string	Explanation: If the bucket is configured with website hosting, the request for obtaining the object can be redirected to another object in the bucket or an external URL. The request is redirected to object anotherPage.html in the same bucket: WebsiteRedirectLocation:/anotherPage.html The request is redirected to an external URL: WebsiteRedirectLocation:http://www.example.com/ OBS obtains the specified value from the header and stores it in the object metadata WebsiteRedirectLocation. Restrictions: The value must start with a slash (/), http://, or https:// and cannot exceed 2 KB. OBS only supports redirection of objects that are in the root directory.
StorageClass	StorageClassType	Explanation: Storage class configured when copying the object. If this parameter is not specified, the object inherits the storage class of the bucket. Value range: See Table 8.
Metadata	object	Explanation: Custom metadata of the object. You can add a header starting with x-obs-meta- in the request to define metadata. The custom metadata will be returned in the response when you retrieve the object or query the object metadata. Restrictions: The custom metadata cannot exceed 8 KB in total. To measure the size, calculate the sum of bytes of all UTF-8 encoded keys and values. The custom metadata keys are case insensitive, but are stored in lowercase in OBS. The key values are case sensitive. Both custom metadata keys and their values must conform to US-ASCII standards. If non-ASCII or unrecognizable characters are required, they must be encoded and decoded in URL or Base64 on the client, because the server does not perform such operations.

**Table 7** MetadataDirectiveType
Constant	Default Value	Description
ObsClient.enums.CopyMetadata	COPY	When copying an object, the object's attributes are also copied. NOTICE: This value is used only in the API for Copying an Object (SDK for Node.js).
ObsClient.enums.ReplaceMetadata	REPLACE	REPLACE uses the complete header carried in the current request to replace the original one and deletes the metadata that is not specified.
ObsClient.enums.ReplaceNewMetadata	REPLACE_NEW	REPLACE_NEW replaces the metadata that already has a value, assigns a value to the metadata that does not have a value, and retains the metadata that is not specified. NOTICE: This value is used only in the API for Configuring Object Metadata (SDK for Node.js).

**Table 8** StorageClassType
Constant	Default Value	Description
ObsClient.enums.StorageClassStandard	STANDARD	Standard storage class. Features low access latency and high throughput and is used for storing massive, frequently accessed (multiple times a month) or small objects (< 1 MB) requiring quick response.
ObsClient.enums.StorageClassWarm	WARM	Infrequent Access storage class. Used for storing data that is semi-frequently accessed (fewer than 12 times a year) but becomes instantly available when needed.
ObsClient.enums.StorageClassCold	COLD	Archive storage class. Used for storing rarely accessed (once a year) data.

Code Examples

This example configures metadata for object example/objectname in bucket examplebucket. The MIME type of the object is set to image/jpeg, the storage class is set to Archive, and custom metadata is also configured for the object.

    
     
       
       
         // 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 setObjectMetadata() {
  try {
    const params = {
      // Specify the bucket name.
      Bucket: "examplebucket",
      // Specify an object. example/objectname is used in this example.
      Key: "example/objectname",
      // Specify a MIME type (image/jpeg in this example) for the object.
      ContentType: "image/jpeg",
      // Specify a storage class (obsClient.enums.StorageClassCold in this example) for the object.
      StorageClass: obsClient.enums.StorageClassCold,
      // Specify custom metadata.
      Metadata: { "property1": "property-value1", "property2": "property-value2" }
    };
    // Configure the metadata for the object.
    const result = await obsClient.setObjectMetadata(params);
    if (result.CommonMsg.Status <= 300) {
      console.log("Set Object(%s)'s metadata successful with bucket(%s)!", params.Key, params.Bucket);
      console.log("RequestId: %s", result.CommonMsg.RequestId);
      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);
  };
};

setObjectMetadata();

        

      

    
   