After an object is uploaded, Object Storage Service (OSS) can start a callback process for the application server. To configure upload callbacks, you need to only add the required callback parameters to the upload request that is sent to OSS.
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 Security Token Service (STS), see Initialization.
Examples
The following sample code provides an example on how to configure an upload callback:
using System;
using System.IO;
using System.Text;
using Aliyun.OSS;
using Aliyun.OSS.Common;
using Aliyun.OSS.Util;
namespace Callback
{
class Program
{
static void Main(string[] args)
{
Program.PutObjectCallback();
Console.ReadKey();
}
public static void PutObjectCallback()
{
// 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. By default, if you do not specify the path of the local file, the file is uploaded from the local path of the project to which the sample program belongs.
var localFilename = "D:\\localpath\\examplefile.txt";
// Specify the URL of the callback server. Example: https://example.com:23450.
const string callbackUrl = "yourCallbackServerUrl";
// Specify the callbackBody field included in the callback request.
const string callbackBody = "bucket=${bucket}&object=${object}&etag=${etag}&size=${size}&mimeType=${mimeType}&" +
"my_var1=${x:var1}&my_var2=${x:var2}";
// Create an OSSClient instance.
var client = new OssClient(endpoint, accessKeyId, accessKeySecret);
try
{
string responseContent = "";
var metadata = BuildCallbackMetadata(callbackUrl, callbackBody);
using (var fs = File.Open(localFilename, FileMode.Open))
{
var putObjectRequest = new PutObjectRequest(bucketName, objectName, fs, metadata);
var result = client.PutObject(putObjectRequest);
responseContent = GetCallbackResponse(result);
}
Console.WriteLine("Put object:{0} succeeded, callback response content:{1}", objectName, responseContent);
}
catch (OssException ex)
{
Console.WriteLine("Failed with error code: {0}; Error info: {1}. \nRequestID: {2}\tHostID: {3}",
ex.ErrorCode, ex.Message, ex.RequestId, ex.HostId);
}
catch (Exception ex)
{
Console.WriteLine("Failed with error info: {0}", ex.Message);
}
}
// Configure an upload callback.
private static ObjectMetadata BuildCallbackMetadata(string callbackUrl, string callbackBody)
{
string callbackHeaderBuilder = new CallbackHeaderBuilder(callbackUrl, callbackBody).Build();
string CallbackVariableHeaderBuilder = new CallbackVariableHeaderBuilder().
AddCallbackVariable("x:var1", "x:value1").AddCallbackVariable("x:var2", "x:value2").Build();
var metadata = new ObjectMetadata();
metadata.AddHeader(HttpHeaders.Callback, callbackHeaderBuilder);
metadata.AddHeader(HttpHeaders.CallbackVar, CallbackVariableHeaderBuilder);
return metadata;
}
// Read the response to the upload callback request.
private static string GetCallbackResponse(PutObjectResult putObjectResult)
{
string callbackResponse = null;
using (var stream = putObjectResult.ResponseStream)
{
var buffer = new byte[4 * 1024];
var bytesRead = stream.Read(buffer, 0, buffer.Length);
callbackResponse = Encoding.Default.GetString(buffer, 0, bytesRead);
}
return callbackResponse;
}
}
}