@Data
@AllArgsConstructor
@NoArgsConstructor
@Entity
@Table(name = "files")
public class File {

    @Id
    @GeneratedValue(generator = "uuid")
    @GenericGenerator(name = "uuid", strategy = "uuid2")
    private String id;

    private String name;

    private String type;
    @Lob
    private byte[] data;

    File(String name, String type, byte[] data) {
        this.name = name;
        this.type = type;
        this.data = data;
    }

}

@Repository
public interface FileRepository extends JpaRepository<File, String> {

}

@Service
public class FileService {

    @Autowired
    private FileRepository fileRepository;

    public File store(MultipartFile file) throws IOException {
        String fileName = StringUtils.cleanPath(file.getOriginalFilename());
        File FileDB = new File(fileName, file.getContentType(), file.getBytes());

        return fileRepository.save(FileDB);
    }

    public File getFile(String id) {
        return fileRepository.findById(id).get();
    }

    public Stream<File> getAllFiles() {
        return fileRepository.findAll().stream();
    }
}

@RestController
public class FileController {

    @Autowired
    private FileService fileService;

    @PostMapping("/upload")
    public ResponseEntity<FileResponseMessage> uploadFile(@RequestParam("file") MultipartFile file) {
        String message = "";
        try {
            fileService.store(file);

            message = "Uploaded the file successfully: " + file.getOriginalFilename();
            return ResponseEntity.status(HttpStatus.OK).body(new FileResponseMessage(message));
        } catch (Exception e) {
            message = "Could not upload the file: " + file.getOriginalFilename() + "!";
            return ResponseEntity.status(HttpStatus.EXPECTATION_FAILED).body(new FileResponseMessage(message));
        }
    }

    @GetMapping("/files")
    public ResponseEntity<List<FileResponse>> getListFiles() {
        List<FileResponse> files = fileService.getAllFiles().map(dbFile -> {
            String fileDownloadUri = ServletUriComponentsBuilder
                    .fromCurrentContextPath()
                    .path("/files/")
                    .path(dbFile.getId())
                    .toUriString();

            return new FileResponse(
                    dbFile.getName(),
                    fileDownloadUri,
                    dbFile.getType(),
                    dbFile.getData().length);
        }).collect(Collectors.toList());

        return ResponseEntity.status(HttpStatus.OK).body(files);
    }

    @GetMapping("/files/{id}")
    public ResponseEntity<byte[]> getFile(@PathVariable String id) {
        File f = fileService.getFile(id);

        return ResponseEntity.ok()
                .header(HttpHeaders.CONTENT_DISPOSITION, "attachment; filename=\"" + f.getName() + "\"")
                .body(f.getData());
    }
}

@Data
@AllArgsConstructor
public class FileResponse {
    private String name;
    private String url;
    private String type;
    private long size;
}

@Data
@AllArgsConstructor
public class FileResponseMessage {
    private String message;
}

@RestControllerAdvice
public class FileControllerExceptionHandler extends ResponseEntityExceptionHandler {

    @ExceptionHandler(MaxUploadSizeExceededException.class)
    public ResponseEntity<FileResponseMessage> handleMaxSizeException(MaxUploadSizeExceededException exc) {
        return ResponseEntity.status(HttpStatus.EXPECTATION_FAILED).body(new FileResponseMessage("File too large!"));
    }
}