Mention AWS CRT client in the README

* Use an explicit `S3AsyncClient.crtBuilder()` according to the warning in the logs for test
* Some code clean up in the `S3MessageHandler`

Author: artembilan

README.md

@@ -48,6 +48,7 @@ These dependencies are optional in the project:
 * `com.amazonaws:amazon-kinesis-producer` - for KPL-based `MessageHandler` 
 * `software.amazon.awssdk:dynamodb` - for `DynamoDbMetadataStore` and `DynamoDbLockRegistry`
 * `software.amazon.awssdk:s3-transfer-manager` - for `S3MessageHandler`
+* `software.amazon.awssdk:aws-crt-client` - for `S3MessageHandler`
 
 Consider to include an appropriate dependency into your project when you use particular component from this project. 
 
@@ -188,6 +189,8 @@ With this config you can send a message with the `java.io.File` as `payload` and
 
 See more information in the `S3MessageHandler` JavaDocs.
 
+NOTE: The AWS SDK recommends to use `S3CrtAsyncClient` for `S3TransferManager`, therefore an `S3AsyncClient.crtBuilder()` has to be used to achieve respective upload and download requirements.
+
 ### Outbound Gateway
 
 The S3 Outbound Gateway is represented by the same `S3MessageHandler` with the `produceReply = true` constructor argument for Java Configuration.

src/main/java/org/springframework/integration/aws/outbound/S3MessageHandler.java

@@ -36,7 +36,6 @@
 import software.amazon.awssdk.transfer.s3.model.UploadDirectoryRequest;
 import software.amazon.awssdk.transfer.s3.model.UploadRequest;
 import software.amazon.awssdk.transfer.s3.progress.TransferListener;
-import software.amazon.awssdk.utils.BinaryUtils;
 import software.amazon.awssdk.utils.IoUtils;
 import software.amazon.awssdk.utils.Md5Utils;
 
@@ -52,7 +51,6 @@
 import org.springframework.messaging.Message;
 import org.springframework.messaging.MessageHandlingException;
 import org.springframework.util.Assert;
-import org.springframework.util.DigestUtils;
 
 /**
  * The {@link AbstractReplyProducingMessageHandler} implementation for the Amazon S3
@@ -298,16 +296,14 @@ else if (payload instanceof File fileToUpload) {
 				if (payload instanceof InputStream inputStream) {
 					byte[] body = IoUtils.toByteArray(inputStream);
 					if (putObjectRequest.contentMD5() == null) {
-						byte[] md5Digest = DigestUtils.md5Digest(body);
-						putObjectRequestBuilder.contentMD5(BinaryUtils.toBase64(md5Digest));
+						putObjectRequestBuilder.contentMD5(Md5Utils.md5AsBase64(body));
 						inputStream.reset();
 					}
 					requestBody = AsyncRequestBody.fromBytes(body);
 				}
 				else if (payload instanceof File fileToUpload) {
 					if (putObjectRequest.contentMD5() == null) {
-						String contentMd5 = Md5Utils.md5AsBase64(fileToUpload);
-						putObjectRequestBuilder.contentMD5(contentMd5);
+						putObjectRequestBuilder.contentMD5(Md5Utils.md5AsBase64(fileToUpload));
 					}
 					if (putObjectRequest.contentLength() == null) {
 						putObjectRequestBuilder.contentLength(fileToUpload.length());
@@ -320,8 +316,7 @@ else if (payload instanceof File fileToUpload) {
 				}
 				else if (payload instanceof byte[] payloadBytes) {
 					if (putObjectRequest.contentMD5() == null) {
-						String contentMd5 = Md5Utils.md5AsBase64(payloadBytes);
-						putObjectRequestBuilder.contentMD5(contentMd5);
+						putObjectRequestBuilder.contentMD5(Md5Utils.md5AsBase64(payloadBytes));
 					}
 					if (putObjectRequest.contentLength() == null) {
 						putObjectRequestBuilder.contentLength((long) payloadBytes.length);

src/test/java/org/springframework/integration/aws/LocalstackContainerTest.java

@@ -78,7 +78,11 @@ static CloudWatchAsyncClient cloudWatchClient() {
 	}
 
 	static S3AsyncClient s3AsyncClient() {
-		return applyAwsClientOptions(S3AsyncClient.builder());
+		return S3AsyncClient.crtBuilder()
+				.region(Region.of(LOCAL_STACK_CONTAINER.getRegion()))
+				.credentialsProvider(credentialsProvider())
+				.endpointOverride(LOCAL_STACK_CONTAINER.getEndpoint())
+				.build();
 	}
 
 	static S3Client s3Client() {