How can I resolve io.netty.channel.StacklessClosedChannelException when downloading a blob from an Azure SAS URL using Java?

generating the ByteStream from the SasUrl of Azure storage

You can use the below code with proper version and with sas url to generate the ByteStream using Azure Java SDK.

Code:

JAVACopied
import com.azure.core.http.netty.NettyAsyncHttpClientBuilder;
import com.azure.storage.blob.BlobClient;
import com.azure.storage.blob.BlobClientBuilder;

import com.azure.storage.common.policy.RequestRetryOptions;
import com.azure.storage.common.policy.RetryPolicyType;
import reactor.netty.resources.ConnectionProvider;

import java.io.ByteArrayOutputStream;
import java.time.Duration;
import java.util.Base64;  

public class App {
     public static void main(String[] args) {
        // Example SAS URL (replace with your actual SAS URL)
        String sasUrl = "https://<Account name>.blob.core.windows.net/<Conatiner name>/<blob name>?sp=r&st=2025-01-24T03:07:42Z&se=2025-01-24T11:07:42Z&spr=https&sv=2022-11-02&sr=b&sig=redacted";

        ConnectionProvider connectionProvider = ConnectionProvider.builder("custom-connection-provider")
                .maxConnections(200) // Adjust as per your concurrency needs
                .pendingAcquireMaxCount(5000)
                .build();

        BlobClient blobClient = new BlobClientBuilder()
                .endpoint(sasUrl.trim())
                .retryOptions(new RequestRetryOptions(
                        RetryPolicyType.EXPONENTIAL,
                        5,
                        2,
                        null,
                        null,
                        null
                ))
                .httpClient(new NettyAsyncHttpClientBuilder()
                .connectionProvider(connectionProvider)
                .readTimeout(Duration.ofMinutes(10))
                .writeTimeout(Duration.ofMinutes(10))
                .responseTimeout(Duration.ofMinutes(10))
                .build())
                .buildClient();

        System.out.println("BlobClient created successfully");

        // Read blob content as a Base64-encoded string
        try (ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream()) {

            // Download blob content into the output stream
                        blobClient.downloadStream(byteArrayOutputStream);

            // Convert the downloaded bytes to Base64
            byte[] imageBytes = byteArrayOutputStream.toByteArray();
            String base64Image = Base64.getEncoder().encodeToString(imageBytes);

            // Log the Base64 string (truncated for safety)
            System.out.println("Base64 Image (truncated): " +
                    base64Image.substring(0, Math.min(base64Image.length(), 100)) + "...");

        } catch (Exception e) {
            System.err.println("Error while processing blob content");
            e.printStackTrace();
        }
    }
}

My versions are azure-storage-blob is 12.29.0 and azure-core-http-netty is 1.15.7.

Output:

BASHCopied
BlobClient created successfully
Base64 Image (truncated): /9j/4AAQSkZJRgABAQEAYABgAAD/2wBDAAIBAQIBAQICAgICAxxxxxxxxxxxxxxHBwcGBwcICQsJCAgKCAcHCg0KCgsM...

Reference:
Download a blob with Java - Azure Storage | Microsoft Learn

As I have mentioned in the question that it might be an open issue from the dependency side

I have used the below dependency which works perfectly previously I was using the azure-storage-blob artifactId which was casing the above-mentioned issue.

XMLCopied
<dependency>
            <groupId>com.azure</groupId>
            <artifactId>azure-core-http-okhttp</artifactId>
            <version>1.12.0</version>
        </dependency>