Object Storage Service:Append upload

Usage notes

• In this topic, the public endpoint of the China (Hangzhou) region is used. If you want to access OSS from other Alibaba Cloud services in the same region as OSS, use an internal endpoint. For more information about OSS regions and endpoints, see Regions and endpoints.

• In this topic, an OSSClient instance is created by using an OSS endpoint. If you want to create an OSSClient by using custom domain names or Security Token Service (STS), see Create an OSSClient instance.

• To use append upload, you must have the oss:PutObject permission. For more information, see Attach a custom policy to a RAM user.

• If the object to which you want to append content does not exist, an appendable object is created when you call the AppendObject operation.

• If the object to which you want to append content exists:

  • If the object is an appendable object and the specified position from which the append operation starts is equal to the current object size, the data is appended to the end of the object.

  • If the object is an appendable object and the specified position from which the append operation starts is not equal to the current object size, the PositionNotEqualToLength error is returned.

  • If the object is not an appendable object, the ObjectNotAppendable error is returned.

Sample code

The following code provides an example on how to perform append upload:

#include <alibabacloud/oss/OssClient.h>
using namespace AlibabaCloud::OSS;

int main(void)
{
    /* Initialize information about the account that is used to access OSS. */
            
    /* Specify the endpoint of the region in which the bucket is located. For example, if the bucket is located in the China (Hangzhou) region, set the endpoint to https://oss-cn-hangzhou.aliyuncs.com. */
    std::string Endpoint = "https://oss-cn-hangzhou.aliyuncs.com";
    /* Specify the name of the bucket. Example: examplebucket. */
    std::string BucketName = "examplebucket";
    /* Specify the full path of the object. Do not include the bucket name in the full path of the object. Example: exampledir/exampleobject.txt. */
    std::string ObjectName = "exampledir/exampleobject.txt";

    /* Initialize resources such as network resources. */
    InitializeSdk();

    ClientConfiguration conf;
    /* Obtain access credentials from environment variables. Before you run the sample code, make sure that the OSS_ACCESS_KEY_ID and OSS_ACCESS_KEY_SECRET environment variables are configured. */
    auto credentialsProvider = std::make_shared<EnvironmentVariableCredentialsProvider>();
    OssClient client(Endpoint, credentialsProvider, conf);

    auto meta = ObjectMetaData();
    meta.setContentType("text/plain");

    /* If the object is appended for the first time, set the position from which the append operation starts to 0. The position for the next append operation is included in the response. The position from which the next append upload starts is the current length of the object. */
    std::shared_ptr<std::iostream> content1 = std::make_shared<std::stringstream>();
    *content1 <<"Thank you for using Aliyun Object Storage Service!";
    AppendObjectRequest request(BucketName, ObjectName, content1, meta);
    request.setPosition(0L);

    /* Perform the first append operation. */
    auto result = client.AppendObject(request);

    if (!result.isSuccess()) {
        /* Handle exceptions. */
        std::cout << "AppendObject fail" <<
        ",code:" << result.error().Code() <<
        ",message:" << result.error().Message() <<
        ",requestId:" << result.error().RequestId() << std::endl;
        return -1;
    }

    std::shared_ptr<std::iostream> content2 = std::make_shared<std::stringstream>();
    *content2 <<"Thank you for using Aliyun Object Storage Service!";
    auto position = result.result().Length();
    AppendObjectRequest appendObjectRequest(BucketName, ObjectName, content2);
    appendObjectRequest.setPosition(position);

    /* Perform the second append operation. */
    auto outcome = client.AppendObject(appendObjectRequest);

    if (!outcome.isSuccess()) {
        /* Handle exceptions. */
        std::cout << "AppendObject fail" <<
        ",code:" << outcome.error().Code() <<
        ",message:" << outcome.error().Message() <<
        ",requestId:" << outcome.error().RequestId() << std::endl;
        return -1;
    }

    /* Release resources such as network resources. */
    ShutdownSdk();
    return 0;
}

References

• For the complete sample code that is used to perform append upload, visit GitHub.

• For more information about the API operation for append upload, see AppendObject.