Object Storage Service:Manage object metadata

Usage notes

• In this topic, the public endpoint of the China (Hangzhou) region is used. If you want to access OSS by using other Alibaba Cloud services in the same region as OSS, use an internal endpoint For more information about the regions and endpoints supported by OSS, see Regions and endpoints.
• In this topic, an OSSClient instance is created by using an OSS endpoint. If you want to create an OSSClient instance by using custom domain names or STS, see Create an OSSClient instance.
• To configure object metadata, you must have the oss:PutObject permission. To query object metadata, you must have the oss:GetObject permission. For more information, see Attach a custom policy to a RAM user.

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 OSS. */
    /* The AccessKey pair of an Alibaba Cloud account has permissions on all API operations. Using these credentials to perform operations in OSS is a high-risk operation. 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";
    /* 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 = "yourEndpoint";
    /* 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. Example: exampledir/exampleobject.txt. */
    std::string ObjectName = "exampledir/exampleobject.txt";

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

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


    /* Configure HTTP headers. */
    auto meta = ObjectMetaData();
    meta.setContentType("text/plain");
    meta.setCacheControl("max-ag e=3");
    /* Configure 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;
        return -1;
    }

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

Query object metadata

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

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. */
    /* The AccessKey pair of an Alibaba Cloud account has permissions on all API operations. Using these credentials to perform operations in OSS is a high-risk operation. 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";
    /* 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 = "yourEndpoint";
    /* 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. Example: exampledir/exampleobject.txt. */
    std::string ObjectName = "exampledir/exampleobject.txt";

    /* Initialize resources, such as network resources. */
    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;
        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;
        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 network resources. */
    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 a simple upload task, see PutObject.
• For more information about the API operations that you can call to query the metadata of an object, see GetObjectMeta and HeadObject.