--- title: aws-sdk-java description: Configure the AWS SDK for Java v2 to work with Cloudflare R2 object storage. image: https://developers.cloudflare.com/dev-products-preview.png --- > Documentation Index > Fetch the complete documentation index at: https://developers.cloudflare.com/r2/llms.txt > Use this file to discover all available pages before exploring further. [Skip to content](#%5Ftop) # aws-sdk-java You must [generate an Access Key](https://developers.cloudflare.com/r2/api/tokens/) before getting started. All examples will utilize `access_key_id` and `access_key_secret` variables which represent the **Access Key ID** and **Secret Access Key** values you generated. This example uses version 2 of the [aws-sdk-java ↗](https://github.com/aws/aws-sdk-java-v2/#using-the-sdk) package. You must pass in the R2 configuration credentials when instantiating your `S3` service client. Note You must set `chunkedEncodingEnabled(false)` in the `S3Configuration` when building your client. The AWS SDK for Java v2 uses chunked transfer encoding by default for `putObject` requests, which causes a signature mismatch error (HTTP 403) with R2\. Disabling chunked encoding ensures the request signature is calculated correctly. ``` import software.amazon.awssdk.auth.credentials.AwsBasicCredentials;import software.amazon.awssdk.auth.credentials.StaticCredentialsProvider;import software.amazon.awssdk.regions.Region;import software.amazon.awssdk.services.s3.S3Client;import software.amazon.awssdk.services.s3.model.*;import software.amazon.awssdk.services.s3.S3Configuration;import software.amazon.awssdk.core.sync.RequestBody;import java.net.URI;import java.util.List; /** * Client for interacting with Cloudflare R2 Storage using AWS SDK S3 compatibility */public class CloudflareR2Client { private final S3Client s3Client; /** * Creates a new CloudflareR2Client with the provided configuration */ public CloudflareR2Client(S3Config config) { this.s3Client = buildS3Client(config); } /** * Configuration class for R2 credentials and endpoint * - accountId: Your Cloudflare account ID * - accessKey: Your R2 Access Key ID (see: https://developers.cloudflare.com/r2/api/tokens) * - secretKey: Your R2 Secret Access Key (see: https://developers.cloudflare.com/r2/api/tokens) */ public static class S3Config { private final String accountId; private final String accessKey; private final String secretKey; private final String endpoint; public S3Config(String accountId, String accessKey, String secretKey) { this.accountId = accountId; this.accessKey = accessKey; this.secretKey = secretKey; this.endpoint = String.format("https://%s.r2.cloudflarestorage.com", accountId); } public String getAccessKey() { return accessKey; } public String getSecretKey() { return secretKey; } public String getEndpoint() { return endpoint; } } /** * Builds and configures the S3 client with R2-specific settings */ private static S3Client buildS3Client(S3Config config) { AwsBasicCredentials credentials = AwsBasicCredentials.create( config.getAccessKey(), config.getSecretKey() ); S3Configuration serviceConfiguration = S3Configuration.builder() .pathStyleAccessEnabled(true) .chunkedEncodingEnabled(false) .build(); return S3Client.builder() .endpointOverride(URI.create(config.getEndpoint())) .credentialsProvider(StaticCredentialsProvider.create(credentials)) .region(Region.of("auto")) // Required by SDK but not used by R2 .serviceConfiguration(serviceConfiguration) .build(); } /** * Lists all buckets in the R2 storage */ public List listBuckets() { try { return s3Client.listBuckets().buckets(); } catch (S3Exception e) { throw new RuntimeException("Failed to list buckets: " + e.getMessage(), e); } } /** * Lists all objects in the specified bucket */ public List listObjects(String bucketName) { try { ListObjectsV2Request request = ListObjectsV2Request.builder() .bucket(bucketName) .build(); return s3Client.listObjectsV2(request).contents(); } catch (S3Exception e) { throw new RuntimeException("Failed to list objects in bucket " + bucketName + ": " + e.getMessage(), e); } } /** * Uploads an object to the specified bucket */ public void putObject(String bucketName, String key, String content) { try { PutObjectRequest request = PutObjectRequest.builder() .bucket(bucketName) .key(key) .build(); s3Client.putObject(request, RequestBody.fromString(content)); } catch (S3Exception e) { throw new RuntimeException("Failed to put object " + key + " in bucket " + bucketName + ": " + e.getMessage(), e); } } public static void main(String[] args) { S3Config config = new S3Config( "", "", "" ); CloudflareR2Client r2Client = new CloudflareR2Client(config); // List buckets System.out.println("Available buckets:"); r2Client.listBuckets().forEach(bucket -> System.out.println("* " + bucket.name()) ); // Upload an object to a bucket String bucketName = "demos"; r2Client.putObject(bucketName, "example.txt", "Hello, R2!"); System.out.println("Uploaded example.txt to bucket '" + bucketName + "'"); // List objects in a specific bucket System.out.println("\nObjects in bucket '" + bucketName + "':"); r2Client.listObjects(bucketName).forEach(object -> System.out.printf("* %s (size: %d bytes, modified: %s)%n", object.key(), object.size(), object.lastModified()) ); }} ``` ## Generate presigned URLs You can also generate presigned links that can be used to temporarily share public write access to a bucket. ``` // import required packages for presigning// Rest of the packages are same as aboveimport software.amazon.awssdk.services.s3.presigner.S3Presigner;import software.amazon.awssdk.services.s3.presigner.model.PutObjectPresignRequest;import software.amazon.awssdk.services.s3.presigner.model.PresignedPutObjectRequest;import java.time.Duration; public class CloudflareR2Client { private final S3Client s3Client; private final S3Presigner presigner; /** * Creates a new CloudflareR2Client with the provided configuration */ public CloudflareR2Client(S3Config config) { this.s3Client = buildS3Client(config); this.presigner = buildS3Presigner(config); } /** * Builds and configures the S3 presigner with R2-specific settings */ private static S3Presigner buildS3Presigner(S3Config config) { AwsBasicCredentials credentials = AwsBasicCredentials.create( config.getAccessKey(), config.getSecretKey() ); return S3Presigner.builder() .endpointOverride(URI.create(config.getEndpoint())) .credentialsProvider(StaticCredentialsProvider.create(credentials)) .region(Region.of("auto")) // Required by SDK but not used by R2 .serviceConfiguration(S3Configuration.builder() .pathStyleAccessEnabled(true) .build()) .build(); } public String generatePresignedUploadUrl(String bucketName, String objectKey, Duration expiration) { PutObjectPresignRequest presignRequest = PutObjectPresignRequest.builder() .signatureDuration(expiration) .putObjectRequest(builder -> builder .bucket(bucketName) .key(objectKey) .build()) .build(); PresignedPutObjectRequest presignedRequest = presigner.presignPutObject(presignRequest); return presignedRequest.url().toString(); } // Rest of the methods remains the same public static void main(String[] args) { // config the client as before // Generate a pre-signed upload URL valid for 15 minutes String uploadUrl = r2Client.generatePresignedUploadUrl( "demos", "README.md", Duration.ofMinutes(15) ); System.out.println("Pre-signed Upload URL (valid for 15 minutes):"); System.out.println(uploadUrl); } } ``` ```json {"@context":"https://schema.org","@type":"TechArticle","@id":"https://developers.cloudflare.com/r2/examples/aws/aws-sdk-java/#page","headline":"aws-sdk-java · Cloudflare R2 docs","description":"Configure the AWS SDK for Java v2 to work with Cloudflare R2 object storage.","url":"https://developers.cloudflare.com/r2/examples/aws/aws-sdk-java/","inLanguage":"en","image":"https://developers.cloudflare.com/dev-products-preview.png","dateModified":"2026-04-21","publisher":{"@type":"Organization","name":"Cloudflare","url":"https://www.cloudflare.com/"},"isPartOf":{"@type":"WebSite","@id":"https://developers.cloudflare.com/#website","name":"Cloudflare Docs","url":"https://developers.cloudflare.com/"}} {"@context":"https://schema.org","@type":"BreadcrumbList","itemListElement":[{"@type":"ListItem","position":1,"item":{"@id":"/directory/","name":"Directory"}},{"@type":"ListItem","position":2,"item":{"@id":"/r2/","name":"R2"}},{"@type":"ListItem","position":3,"item":{"@id":"/r2/examples/","name":"Examples"}},{"@type":"ListItem","position":4,"item":{"@id":"/r2/examples/aws/","name":"S3 SDKs"}},{"@type":"ListItem","position":5,"item":{"@id":"/r2/examples/aws/aws-sdk-java/","name":"aws-sdk-java"}}]} ```