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Object Storage Service:Download objects

Last Updated:Oct 23, 2023

By default, when you call the GetObject operation on an object in a versioning-enabled bucket, only the current version of the object is returned.

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, access credentials are obtained from environment variables. For more information about how to configure access credentials, see Configure access credentials.

  • 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 Security Token Service (STS), see Create an OSSClient instance.

  • To download an object, you must have the oss:GetObject permission. For more information, see Attach a custom policy to a RAM user.

Background information

When you call the GetObject operation to download an object in a bucket, you may obtain one of the following results:

  • If the current version of the object is a delete marker, OSS returns 404 Not Found.

  • If the version ID of the object is specified in the request, OSS returns the specified version of the object. If the version ID is set to null in the request, OSS returns the version whose version ID is null.

  • If the version ID specified in the request is the version ID of a delete marker, OSS returns 405 Method Not Allowed.

Examples

The following sample code provides an example on how to download an object:

import com.aliyun.oss.OSS;
import com.aliyun.oss.common.auth.*;
import com.aliyun.oss.common.auth.*;
import com.aliyun.oss.common.auth.*;
import com.aliyun.oss.OSSClientBuilder;
import com.aliyun.oss.OSSException;
import com.aliyun.oss.model.*;
import java.io.BufferedReader;
import java.io.InputStreamReader;

public class Demo {
    public static void main(String[] args) {
        // In this example, the endpoint of the China (Hangzhou) region is used. Specify your actual endpoint. 
        String endpoint = "https://oss-cn-hangzhou.aliyuncs.com";
        // 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. 
        EnvironmentVariableCredentialsProvider credentialsProvider = CredentialsProviderFactory.newEnvironmentVariableCredentialsProvider();
        // Specify the name of the bucket. Example: examplebucket. 
        String bucketName = "examplebucket";
        // Specify the full path of the object. Example: exampledir/exampleobject.txt. Do not include the bucket name in the full path. 
        String objectName = "exampledir/exampleobject.txt";
        // Specify the version ID of the object. Example: CAEQARiBgID8rumR2hYiIGUyOTAyZGY2MzU5MjQ5ZjlhYzQzZjNlYTAyZDE3****. 
        String versionid = "CAEQARiBgID8rumR2hYiIGUyOTAyZGY2MzU5MjQ5ZjlhYzQzZjNlYTAyZDE3****";

        // Create an OSSClient instance. 
        OSS ossClient = new OSSClientBuilder().build(endpoint, credentialsProvider);
        try {
            // Encapsulate the GetObject request. 
            GetObjectRequest getObjectRequest = new GetObjectRequest(bucketName, objectName);            
            getObjectRequest.setVersionId(versionid);
            // ossObject specifies the bucket name, object name, object metadata, and an input stream. 
            OSSObject ossObject = ossClient.getObject(getObjectRequest);

            // View the version ID of the downloaded object. 
            System.out.println("Get Object versionid:" +  ossObject.getObjectMetadata().getVersionId());
            // View the content of the object that has the specified version ID. 
            System.out.println("Object content:");
            BufferedReader reader = new BufferedReader(new InputStreamReader(ossObject.getObjectContent()));
            while (true) {
                String line = reader.readLine();
                if (line == null) break;
                System.out.println("\n" + line);
            }

        } catch (OSSException oe) {
            System.out.println("Caught an OSSException, which means your request made it to OSS, "
                    + "but was rejected with an error response for some reason.");
            System.out.println("Error Message:" + oe.getErrorMessage());
            System.out.println("Error Code:" + oe.getErrorCode());
            System.out.println("Request ID:" + oe.getRequestId());
            System.out.println("Host ID:" + oe.getHostId());
        } catch (Throwable ce) {
            System.out.println("Caught an ClientException, which means the client encountered "
                    + "a serious internal problem while trying to communicate with OSS, "
                    + "such as not being able to access the network.");
            System.out.println("Error Message:" + ce.getMessage());
        } finally {
            // Shut down the OSSClient instance. 
            if (ossClient != null) {
                ossClient.shutdown();
            }
        }
    }
}            

For more information about the API operation that you can call to download an object, see GetObject.