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Object Storage Service:Upload callbacks

Last Updated:Oct 23, 2023

After an object is uploaded, Object Storage Service (OSS) can send a callback request to the application server. To implement a callback, you need to only send a request that contains relevant callback parameters 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, 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.


The following sample code provides an example on how to configure an upload callback:

import com.aliyun.oss.OSS;
import com.aliyun.oss.common.auth.*;
import com.aliyun.oss.OSSClientBuilder;
import com.aliyun.oss.OSSException;
import com.aliyun.oss.model.*;

public class Demo {
    public static void main(String[] args) throws Exception{
        // In this example, the endpoint of the China (Hangzhou) region is used. Specify your actual endpoint. 
        String endpoint = "";
        // 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 address of the server to which the callback request is sent. Example: 
        String callbackUrl = "yourCallbackServerUrl";

        // Create an OSSClient instance. 
        OSS ossClient = new OSSClientBuilder().build(endpoint, credentialsProvider);
        try {
            String content = "Hello OSS";
            PutObjectRequest putObjectRequest = new PutObjectRequest(bucketName, objectName,new ByteArrayInputStream(content.getBytes()));

            // Specify upload callback parameters. 
            Callback callback = new Callback();
            // (Optional) Specify the CallbackHost field in the callback request header. 
            // callback.setCallbackHost("yourCallbackHost");
            // Specify the callbackBody field in the callback request. 
            // Specify the Content-Type field in the callback request. 
            // Specify custom parameters for the callback request. Each custom parameter consists of a key and a value. The key must start with x:. 
            callback.addCallbackVar("x:var1", "value1");
            callback.addCallbackVar("x:var2", "value2");

            PutObjectResult putObjectResult = ossClient.putObject(putObjectRequest);

            // Read the response to the upload callback request. 
            byte[] buffer = new byte[1024];
            // You must close the obtained stream after the data is read. Otherwise, connection leaks may occur. Consequently, no connections are available and an exception occurs. 
        } 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 {
            if (ossClient != null) {


  • For the complete sample code that is used to configure upload callbacks, visit GitHub.

  • For more information about the API operation that you can call to configure upload callbacks, see Callback.