Spring MVC: guide with File Uploading and Concurrent Requests Leading to 500 Internal Server scenarios
I'm optimizing some code but I'm trying to debug I'm sure I'm missing something obvious here, but I'm running into a question with file uploads in my Spring MVC application that's causing a `500 Internal Server behavior` when multiple users try to upload files concurrently... I am using Spring 5.3.10 and Spring Boot 2.5.4. The form is set up to upload files to a specific endpoint, and here's a snippet of the controller method: ```java @PostMapping("/upload") public ResponseEntity<String> uploadFile(@RequestParam("file") MultipartFile file) { if (file.isEmpty()) { return ResponseEntity.badRequest().body("File is empty"); } try { // Process the file (e.g., save to disk) Path path = Paths.get(uploadDir, file.getOriginalFilename()); Files.write(path, file.getBytes()); return ResponseEntity.ok("File uploaded successfully: " + file.getOriginalFilename()); } catch (IOException e) { return ResponseEntity.status(HttpStatus.INTERNAL_SERVER_ERROR).body("Could not upload file: " + e.getMessage()); } } ``` I have ensured that the `uploadDir` is set correctly and has the right permissions. However, when I test the upload with multiple files from different users, I occasionally see the following behavior in my logs: ``` 2023-10-03 14:22:11 behavior 12345 --- [nio-8080-exec-1] o.s.web.servlet.DispatcherServlet : Failed to handle request org.springframework.web.multipart.MaxUploadSizeExceededException: Maximum upload size exceeded ``` This exception leads to the `500 Internal Server behavior`, but I am not hitting the upload limit defined in my application properties: ```properties spring.servlet.multipart.max-file-size=10MB spring.servlet.multipart.max-request-size=10MB ``` I've also tried adding `@Transactional` to the controller method to manage the transaction scope and ensure thread safety, but that doesn't seem to help either. Is there something specific I should be doing to handle concurrent uploads correctly, or is there an overlooked setting that could be causing this scenario? Any insights or suggestions would be greatly appreciated! My development environment is Ubuntu. This is part of a larger CLI tool I'm building. This issue appeared after updating to Java 3.10. Any feedback is welcome!