Object Storage Service:Download objects

Background information

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 OSS 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 Security Token Service (STS), see Initialization.

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

Sample code

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

using System;
using System.IO;
using Aliyun.OSS;

namespace Samples
{
    public class Program
    {
        public static void Main(string[] args)
        {
            // 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. 
            var 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. 
            var accessKeyId = Environment.GetEnvironmentVariable("OSS_ACCESS_KEY_ID");
            var accessKeySecret = Environment.GetEnvironmentVariable("OSS_ACCESS_KEY_SECRET");
            // Specify the name of the bucket. Example: examplebucket. 
            var bucketName = "examplebucket";
            // Specify the full path of the object. Do not include the bucket name in the full path. Example: exampledir/exampleobject.txt. 
            var objectName = "exampledir/exampleobject.txt";
            // Specify the full path of the local file that you want to upload. Example: D:\\localpath\\examplefile.txt. 
            var downloadFilename = "D:\\localpath\\examplefile.txt";
            var versionid = "yourArchiveObjectVersionid";
            // Specify the region in which the bucket is located. For example, if the bucket is located in the China (Hangzhou) region, set the region to cn-hangzhou.
            const string region = "cn-hangzhou";
            
            // Create a ClientConfiguration instance and modify parameters as required.
            var conf = new ClientConfiguration();
            
            // Use the signature algorithm V4.
            conf.SignatureVersion = SignatureVersion.V4;
            
            // Create an OSSClient instance.
            var client = new OssClient(endpoint, accessKeyId, accessKeySecret, conf);
            c.SetRegion(region);
            try
            {
                // Download the object to a stream. OssObject includes object information, such as the bucket in which the object is stored, the object name, object metadata, and an input stream. 
                var request = new GetObjectRequest(bucketName, objectName)
                {
                    // Specify the version ID of the object. 
                    VersionId = versionid
                };
                var obj = client.GetObject(request);
                using (var requestStream = obj.Content)
                {
                    byte[] buf = new byte[1024];
                    var fs = File.Open(downloadFilename, FileMode.OpenOrCreate);
                    var len = 0;
                    // The input stream can be used to read and download the object content to a local file or to the memory. 
                    while ((len = requestStream.Read(buf, 0, 1024)) != 0)
                    {
                        fs.Write(buf, 0, len);
                    }
                    fs.Close();
                }
                Console.WriteLine("Get object succeeded, vesionid:{0}", versionid);
            }
            catch (Exception ex)
            {
                Console.WriteLine("Get object failed. {0}", ex.Message);
            }
        }
    }
}

References

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