Checking Whether an Object Exists (SDK for Go)
Function
You can use the HeadObject API to check whether a specified object exists in a specified bucket. This API returns only the object metadata but not the object content by sending an HTTP HEAD request to the object. Therefore, the performance is efficient.
Restrictions
- To check whether an object exists, you must be the object owner or have the required permission (obs:object:HeadObject in IAM or HeadObject in a bucket policy). For details, see Introduction to OBS Access Control, IAM Custom Policies, and Configuring an Object Policy.
- The mapping between OBS regions and endpoints must comply with what is listed in Regions and Endpoints.
- If the object does not exist, the status code 404 Not Found is returned.
Method
func (obsClient ObsClient) HeadObject(input *HeadObjectInput) (output *BaseModel, err error)
Request Parameters
| Parameter | Type | Mandatory (Yes/No) | Description |
|---|---|---|---|
| input | Yes | Explanation: Input parameters for checking whether an object exists. For details, see Table 2. |
| Parameter | Type | Mandatory (Yes/No) | Description |
|---|---|---|---|
| Bucket | string | Yes | Explanation: Bucket name Restrictions:
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 that does not contain the bucket name. For example, if the address for accessing the object is examplebucket.obs.ap-southeast-1.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, G001117FCE89978B0000401205D5DC9 Value range: The value must contain 32 characters. Default value: None. If this parameter is left blank, the latest version of the object is specified. |
Responses
| Parameter | Type | Description |
|---|---|---|
| output | Explanation: Returned results. For details, see Table 4. | |
| err | error | Explanation: Error messages returned by the API |
| Parameter | Type | Description |
|---|---|---|
| StatusCode | int | Explanation: HTTP status code Restrictions: None 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 Restrictions: None Value range: None Default value: None |
| ResponseHeaders | map[string][]string | Explanation: HTTP response headers Restrictions: None Value range: None Default value: None |
Code Examples
This example checks whether object example/objectname exists in bucket examplebucket.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 | 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/intl/en-us/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 not advised 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. // securityToken := os.Getenv("SecurityToken") // Enter the endpoint corresponding to the bucket. CN-Hong Kong is used here as an example. Replace it with the one currently in use. endPoint := "https://obs.ap-southeast-1.myhuaweicloud.com" // 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.HeadObjectInput{} // Specify a bucket name. input.Bucket = "examplebucket" // Specify an object name (example/objectname as an example). input.Key = "example/objectname" // Check whether the object exists. output, err := obsClient.HeadObject(input) if err == nil { fmt.Printf("Head object(%s) successful with bucket(%s)!\n", input.Key, input.Bucket) fmt.Printf("RequestId:%s\n", output.RequestId) return } fmt.Printf("Head object(%s) successful 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) } } |
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