AWS S3 Presigned URL file upload - Retain file name in bucket

I am trying to upload files into S3 bucket using presigned PUT URL like below

String tempFileKey = UUID.randomUUID().toString();
    GeneratePresignedUrlRequest generatePresignedUrlRequest =
                    new GeneratePresignedUrlRequest(tempBucketName, tempFileKey)
                            .withMethod(HttpMethod.PUT)
                            .withExpiration(expiration);
    URL fileUrl = s3Client.generatePresignedUrl(generatePresignedUrlRequest);

The problem with above approach is if the user uploads a file named 'xyz.jpg', I am not able to retain the file name (or extension) in the s3 bucket. The file gets saved with the tempFileKey as name. I won't be knowing the file name or extension while creating the presigned url.

I tried using ${filename} as tempFilekey as suggested in https://stackoverflow.com/questions/26386520/sending-file-direct-from-browser-to-s3-but-changing-file-name but it is just getting saved under the name ${filename} (literally)

S3 can use the user-provided filename if you put ${filename} in the signed key.

Docs are at https://docs.aws.amazon.com/AmazonS3/latest/API/RESTObjectPOST.html

Perhaps your problem is PUT vs POST?

There is a worked example here that uses this in an HTML form with ${filename} in the key: https://docs.aws.amazon.com/AmazonS3/latest/API/sigv4-post-example.html

Object key is integral part of the pre-signed url and is required by the algorithm which generates the url:

• Authenticating Requests: Using Query Parameters (AWS Signature Version 4)

Thus, you can't change the key.