Configure object metadata

The following code provides an example on how to configure object metadata:
#include <alibabacloud/oss/OssClient.h>
using namespace AlibabaCloud::OSS;

int main(void)
{

    /* Initialize the information about the account that is used to access Object Storage Service (OSS). */
    /* Security risks may arise if you use the AccessKey pair of an Alibaba Cloud account to access OSS because the account has permissions on all API operations. We recommend that you use a RAM user to call API operations or perform routine O&M. To create a RAM user, log on to the RAM console. */
    std::string AccessKeyId = "yourAccessKeyId";
    std::string AccessKeySecret = "yourAccessKeySecret";
    /* Set yourEndpoint to 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 = "yourEndpoint";
    /* Specify the bucket name. Example: examplebucket. */
    std::string BucketName = "examplebucket";
    /* Specify the full path of the object. The full path cannot contain the bucket name. Example: exampledir/exampleobject.txt. */
    std::string ObjectName = "exampledir/exampleobject.txt";

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

    ClientConfiguration conf;
    OssClient client(Endpoint, AccessKeyId, AccessKeySecret , conf);


    /* Specify the HTTP headers. */
    auto meta = ObjectMetaData();
    meta.setContentType("text/plain");
    meta.setCacheControl("max-ag e=3");
    /* Specify user metadata. */
    meta.UserMetaData()["meta"] = "meta-value";

    std::shared_ptr<std::iostream> content = std::make_shared<std::stringstream>();
    *content << "Thank you for using Aliyun Object Storage Service!";
    client.PutObject(BucketName, ObjectName, content, meta);

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

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

Query object metadata

The following table describes the methods that you can use to query object metadata.

Method Description Advantage
GetObjectMeta Queries parts of object metadata such as the ETag, Size, and LastModified (the last modified time) values of the object. More lightweight and faster
HeadObject Queries all object metadata. None

The following code provides an example on how to query object metadata:

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

int main(void)
{
    /* Initialize the information about the account that is used to access OSS. */
    /* Security risks may arise if you use the AccessKey pair of an Alibaba Cloud account to access OSS because the account has permissions on all API operations. We recommend that you use a RAM user to call API operations or perform routine O&M. To create a RAM user, log on to the RAM console. */
    std::string AccessKeyId = "yourAccessKeyId";
    std::string AccessKeySecret = "yourAccessKeySecret";
    /* Set Endpoint to 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 = "yourEndpoint";
    /* Specify the bucket name. Example: examplebucket. */
    std::string BucketName = "examplebucket";
    /* Specify the full path of the object. The full path cannot contain the bucket name. Example: exampledir/exampleobject.txt. */
    std::string ObjectName = "exampledir/exampleobject.txt";

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

    ClientConfiguration conf;
    OssClient client(Endpoint, AccessKeyId, AccessKeySecret, conf);

    /* Query parts of the object metadata. */
    auto outcome = client.GetObjectMeta(BucketName, ObjectName);

    if (!outcome.isSuccess()) {
        /* Handle exceptions. */
        std::cout << "GetObjectMeta fail" <<
        ",code:" << outcome.error().Code() <<
        ",message:" << outcome.error().Message() <<
        ",requestId:" << outcome.error().RequestId() << std::endl;
        ShutdownSdk();
        return -1;
    }
    else { 
        auto metadata = outcome.result();
        std::cout << " get metadata success, ETag:" << metadata.ETag() << "; LastModified:" 
        << metadata.LastModified() << "; Size:" << metadata.ContentLength() << std::endl;
    }

    /* Query all object metadata. */
    outcome = client.HeadObject(BucketName, ObjectName);

    if (!outcome.isSuccess()) {
        /* Handle exceptions. */
        std::cout << "HeadObject fail" <<
        ",code:" << outcome.error().Code() <<
        ",message:" << outcome.error().Message() <<
        ",requestId:" << outcome.error().RequestId() << std::endl;
        ShutdownSdk();
        return -1;
    }
    else { 
        auto headMeta = outcome.result();
        std::cout <<"headMeta success, ContentType:" 
        << headMeta.ContentType() << "; ContentLength:" << headMeta.ContentLength() 
        << "; CacheControl:" << headMeta.CacheControl() << std::endl;
    }

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

References

  • For the complete sample code that is used to configure and query object metadata, visit GitHub.
  • For more information about the API operation that you can call to configure object metadata in simple upload, see PutObject.
  • For more information about the API operation that you can call to query object metadata, see GetObjectMeta.