Help Center/ Object Storage Service/ SDK Reference/ Java/ Object Management (SDK for Java)/ Checking Whether an Object Exists (SDK for Java)
Updated on 2024-06-18 GMT+08:00

Checking Whether an Object Exists (SDK for Java)

Function

This API checks whether an object exists. If the returned HTTP status code is 200, the object exists. If the returned HTTP status code is 404, the object or bucket does not exist.

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

Restrictions

Method

doesObjectExist(final GetObjectMetadataRequest request)

Request Parameters

Table 1 List of request parameters

Parameter

Type

Mandatory (Yes/No)

Description

request

GetObjectMetadataRequest

Yes

Explanation:

Request parameters. For details, see Table 2.

Table 2 GetObjectMetadataRequest

Parameter

Type

Mandatory (Yes/No)

Description

bucketName

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 periods (.) and hyphens (-) 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.

Default value:

None

objectKey

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.

Value range:

The value must contain 32 characters.

Default value:

None

userHeaders

HashMap<String, String>

No

Explanation:

User header list. In HashMap, the String key and value indicate the name and value of the user header field respectively. The SDK does not process the userHeaders and instead transparently transmits it to the server for later use.

Value range:

The value must contain 32 characters.

Default value:

None

encodeHeaders

boolean

No

Explanation:

Whether to encode and decode HTTP headers.

Value range:

true: HTTP headers are encoded and decoded.

false: HTTP headers are not encoded or decoded.

Default value:

true

sseHeader

SseCHeader

No

Explanation:

Server-side decryption headers. For details, see Table 3.

Table 3 SseCHeader

Parameter

Type

Mandatory (Yes/No)

Description

algorithm

ServerAlgorithm

Yes

Explanation:

SSE-C is used for encrypting objects on the server side.

Value range:

AES256, indicating AES is used to encrypt the object in SSE-C. For details, see Table 4.

Default value:

None

sseAlgorithm

SSEAlgorithmEnum

No

Explanation:

Encryption algorithm.

Restrictions:

Only AES256 is supported.

Value range:

See Table 5.

Default value:

None

sseCKey

byte[]

Yes

Explanation:

Key used for encrypting the object when SSE-C is used, in byte[] format.

Default value:

None

sseCKeyBase64

String

No

Explanation:

Base64-encoded key used for encrypting the object when SSE-C is used.

Default value:

None

Table 4 ServerAlgorithm

Constant

Default Value

AES256

AES256

Table 5 SSEAlgorithmEnum

Constant

Default Value

KMS

kms

AES256

AES256

Responses

Table 6 Response headers

Method

Return Value Type

Description

doesObjectExist(final GetObjectMetadataRequest request)

boolean

Whether the object exists in the bucket.

Code Examples

This example checks whether object objectname exists in bucket examplebucket.

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import com.obs.services.ObsClient;
import com.obs.services.exception.ObsException;
public class DoesObjectExist001 {
    public static void main(String[] args) {
        // Obtain an AK/SK pair using environment variables or import the AK/SK pair in other ways. Using hard coding may result in leakage.
        // Obtain an AK/SK pair on the management console.
        String ak = System.getenv("ACCESS_KEY_ID");
        String sk = System.getenv("SECRET_ACCESS_KEY_ID");
        // (Optional) If you are using 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.
        // Obtain an AK/SK pair and a security token using environment variables or import them in other ways.
        // String securityToken = System.getenv("SECURITY_TOKEN");
        // Enter the endpoint corresponding to the bucket. CN-Hong Kong is used here as an example. Replace it with the one in your actual situation.
        String endPoint = "https://obs.ap-southeast-1.myhuaweicloud.com";
        // Obtain an endpoint using environment variables or import it in other ways.
        //String endPoint = System.getenv("ENDPOINT");
        
        // Create an ObsClient instance.
        // Use the permanent AK/SK pair to initialize the client.
        ObsClient obsClient = new ObsClient(ak, sk,endPoint);
        // Use the temporary AK/SK pair and security token to initialize the client.
        // ObsClient obsClient = new ObsClient(ak, sk, securityToken, endPoint);

        try {
            // Check whether the specified object exists.
            System.out.println(obsClient.doesObjectExist("examplebucket", "objectname") ? "exists!" : "does not exist!");
            System.out.println("doesObjectExist successfully");
        } catch (ObsException e) {
            System.out.println("doesObjectExist failed");
            // Request failed. Print the HTTP status code.
            System.out.println("HTTP Code:" + e.getResponseCode());
            // Request failed. Print the server-side error code.
            System.out.println("Error Code:" + e.getErrorCode());
            // Request failed. Print the error details.
            System.out.println("Error Message:" + e.getErrorMessage());
            // Request failed. Print the request ID.
            System.out.println("Request ID:" + e.getErrorRequestId());
            System.out.println("Host ID:" + e.getErrorHostId());
            e.printStackTrace();
        } catch (Exception e) {
            System.out.println("doesObjectExist failed");
            // Print other error information.
            e.printStackTrace();
        }
    }
}

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