spring-boot-demo/file-transfer

file-transfer

Companion code for File Upload and Download in Spring Boot 4: Multipart, Streaming and S3 Presigned URLs.

Spring Boot 4.1.1, Spring Framework 7.0.9, Tomcat 11.0.24, JDK 25, AWS SDK for Java 2.56.0. No Docker needed.

Area	Code	What the run shows
Multipart limits	UploadController, UploadErrors, MultipartLimitsTest	the 1 MB / 2 MB limits are enforced by Tomcat, so MockMvc accepts a file the real server rejects; the rejected-upload race (cap/01-limits.txt)
Filenames	FileStore, FilenameAndDownloadTest	getOriginalFilename() is whatever the client sent, including ../../; the file is stored under a UUID (cap/02-filename.txt)
Download	DownloadController	Resource gives Range/206/416 for free; Content-Disposition encoding (cap/03-download.txt)
Presigned URLs	S3PresignService, PresignController, FakeS3, PresignedUrlTest	what is and is not covered by the signature; expiry; reuse (cap/04-presign.txt)
Streaming	StreamController, scripts/run-all.sh	200 MB download and a 150 MB upload under -Xmx64m (cap/05-streaming.txt, cap/06-big-upload.txt)

./scripts/run-all.sh      # tests, then the -Xmx64m experiments; rewrites cap/*.txt

What was and was not run

• The presigned URLs are produced by the real AWS SDK presigner and checked by FakeS3, a small in-process server that recomputes the AWS Signature V4 query signature from the published algorithm. That proves the URLs are consistent with the algorithm as documented. It does not prove a real S3 or MinIO server accepts them: this environment has no Docker and no S3-compatible server, so nothing here was run against one.
• app.s3.access-key and app.s3.secret-key are the example keys from the AWS documentation. They are not credentials.