Configuring Object Metadata (SDK for Go)

Function

Object metadata is a set of name-value pairs that describe the object and is used for object management.

Currently, only the metadata defined by the system is supported.

There are two kinds of metadata: system-controlled metadata and user-controlled metadata. For example, metadata such as Last-Modified is controlled by the system and cannot be modified. You can modify the metadata such as ContentLanguage through the API.

This API sends a HEAD request to configure the metadata of an object in a specified bucket.

Restrictions

To configure object metadata, you must be the bucket owner or have the required permission (obs:object:ModifyObjectMetaData in IAM or ModifyObjectMetaData in a bucket policy). For details, see Introduction to OBS Access Control, IAM Custom Policies, and Configuring an Object Policy.
When versioning is enabled for a bucket, you can set metadata for objects of the latest version, but cannot set metadata for objects of historical versions.
You cannot set metadata for Archive objects.

Method

func (obsClient ObsClient) SetObjectMetadata(input *SetObjectMetadataInput) (output *SetObjectMetadataOutput, err error)

Request Parameters

**Table 1** List of request parameters
Parameter	Type	Mandatory (Yes/No)	Description
input	*SetObjectMetadataInput	Yes	Explanation: Input parameters for configuring object metadata. For details, see Table 2.

**Table 2** SetObjectMetadataInput
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 of 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 must 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 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. Value range: The value must contain 1 to 1,024 characters. Default value: None
VersionId	string	No	Explanation: Object version ID, for example, G001117FCE89978B0000401205D5DC9A Value range: The value must contain 32 characters. Default value: None
CacheControl	string	No	Explanation: Cache-Control header in the response. It specifies cache behaviors of the web page when an object is downloaded. Default value: None
ContentDisposition	string	No	Explanation: Content-Disposition header in the response. It specifies the name of the object when it is downloaded. Default value: None
ContentEncoding	string	No	Explanation: Content-Encoding header in the response. It specifies the content encoding format when an object is downloaded. Default value: None
ContentLanguage	string	No	Explanation: Content-Language header in the response. It specifies the content language format when an object is downloaded. Default value: None
ContentType	string	No	Explanation: Content-Type header in the response. It specifies the object file type. 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. 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 http://www.example.com/: 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 for objects in the root directory of a bucket. Default value: None
StorageClass	StorageClassType	No	Explanation: Storage class of an object. Value range: See Table 3. Default value: None
Metadata	map[string]string	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. To measure the custom metadata, sum the number of bytes in the UTF-8 encoding of each key and value. 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 or decoded in URL or Base64 on the client, because the server does not perform such operations. Default value: None

**Table 3** StorageClassType
Constant	Default Value	Description
StorageClassStandard	STANDARD	OBS Standard 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.
StorageClassWarm	WARM	OBS Infrequent Access Used for storing data that is semi-frequently accessed (fewer than 12 times a year) but is instantly available when needed.
StorageClassCold	COLD	OBS Archive Used for storing rarely accessed (once a year) data.

Responses

**Table 4** List of returned results
Parameter	Type	Description
output	*SetObjectMetadataOutput	Explanation: Returned results. For details, see Table 5.
err	error	Explanation: Error messages returned by the API

**Table 5** SetObjectMetadataOutput
Parameter	Type	Description
StatusCode	int	Explanation: HTTP status code Value range: A status code is a group of digits that can be 2xx (indicating successes) or 4xx or 5xx (indicating errors). It indicates the status of a response. For more information, see Status Code. Default value: None
RequestId	string	Explanation: Request ID returned by the OBS server Default value: None
ResponseHeaders	map[string][]string	Explanation: HTTP response headers Default value: None
MetadataDirective	MetadataDirectiveType	Explanation: Policy for copying the source object's properties Value range: See Table 6. Default value: None
CacheControl	string	Explanation: Cache-Control header in the response. It specifies cache behaviors of the web page when an object is downloaded. Default value: None
ContentDisposition	string	Explanation: Content-Disposition header in the response. It specifies the name of the object when it is downloaded. Default value: None
ContentEncoding	string	Explanation: Content-Encoding header in the response. It specifies the content encoding format when an object is downloaded. Default value: None
ContentLanguage	string	Explanation: Content-Language header in the response. It specifies the content language format when an object is downloaded. Default value: None
ContentType	string	Explanation: Content-Type header in the response. It specifies the object file type. Default value: None
Expires	string	Explanation: Expires header in the response. It specifies the cache expiration time of the web page when the object is downloaded. Default value: None
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 http://www.example.com/: 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 for objects in the root directory of a bucket. Default value: None
StorageClass	StorageClassType	Explanation: Object storage class. If you do not specify this header, the object inherits the storage class of the bucket. Value range: See Table 7. Default value: None
Metadata	map[string]string	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. To measure the custom metadata, sum the number of bytes in the UTF-8 encoding of each key and value. 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 or decoded in URL or Base64 on the client, because the server does not perform such operations. Default value: None

**Table 6** MetadataDirectiveType
Constant	Default Value	Description
CopyMetadata	COPY	When copying an object, the object's properties are also copied.
ReplaceMetadata	REPLACE	When copying an object, the object's properties are replaced.

**Table 7** StorageClassType
Constant	Default Value	Description
StorageClassStandard	STANDARD	OBS Standard 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.
StorageClassWarm	WARM	OBS Infrequent Access Used for storing data that is semi-frequently accessed (fewer than 12 times a year) but is instantly available when needed.
StorageClassCold	COLD	OBS Archive 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.

    
     
       
       
         package main
import (
    "fmt"
    "os"
    obs "github.com/huaweicloud/huaweicloud-sdk-go-obs/obs"
)
func main() {
    //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.
    ak := os.Getenv("AccessKeyID")
    sk := os.Getenv("SecretAccessKey")
    // (Optional) If you use a temporary AK/SK pair and a security token to access OBS, you are advised not to use hard coding to reduce leakage risks. You can obtain an AK/SK pair using environment variables or import an AK/SK pair in other ways.
    // securityToken := os.Getenv("SecurityToken")
    // Enter the endpoint corresponding to the bucket. EU-Dublin is used here as an example. Replace it with the one currently in use.
    endPoint := "https://obs.eu-west-101.myhuaweicloud.eu" 
    // Create an obsClient instance.
    // If you use a temporary AK/SK pair and a security token to access OBS, use the obs.WithSecurityToken method to specify a security token when creating an instance.
    obsClient, err := obs.New(ak, sk, endPoint /*, obs.WithSecurityToken(securityToken)*/)
    if err != nil {
        fmt.Printf("Create obsClient error, errMsg: %s", err.Error())
    }
    input := &obs.SetObjectMetadataInput{}
    // Specify a bucket name.
    input.Bucket = "examplebucket"
    // Specify an object (example/objectname as an example).
    input.Key = "example/objectname"
    // Specify a MIME type (image/jpeg as an example) for the object.
    input.ContentType = "image/jpeg"
    // Specify a storage class (obs.StorageClassCold as an example) for the object.
    input.StorageClass = obs.StorageClassCold
    // Specify custom metadata.
    input.Metadata = map[string]string{"property1": "property-value1", "property2": "property-value2"}
    // Configure metadata for the object.
    output, err := obsClient.SetObjectMetadata(input)
    if err == nil {
        fmt.Printf("Set Object(%s)'s metadata successful with bucket(%s)!\n", input.Key, input.Bucket)
        fmt.Printf("RequestId:%s\n", output.RequestId)
        return
    }
    fmt.Printf("Set Object(%s)'s metadata fail with bucket(%s)!\n", input.Key, input.Bucket)
    if obsError, ok := err.(obs.ObsError); ok {
        fmt.Println("An ObsError was found, which means your request sent to OBS was rejected with an error response.")
        fmt.Println(obsError.Error())
    } else {
        fmt.Println("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.")
        fmt.Println(err)
    }
}

        

      

    
   