파일 업로드

# application.properties
spring.servlet.multipart.max-file-size=10MB
spring.servlet.multipart.max-request-size=10MB
file.upload.path=/uploads

// FileController.java
@RestController
@RequestMapping("/api/files")
@RequiredArgsConstructor
public class FileController {
    private final FileService fileService;

    @PostMapping("/upload")
    public ApiResponse<String> upload(
            @RequestParam("file") MultipartFile file) {
        String url = fileService.upload(file);
        return ApiResponse.ok(url);
    }
}

// FileService.java
@Service
public class FileService {
    private final List<String> ALLOWED_TYPES =
        List.of("image/jpeg", "image/png", "image/webp");

    public String upload(MultipartFile file) {
        // 검증
        if (file.isEmpty()) throw new BadRequestException("파일이 없습니다");
        if (!ALLOWED_TYPES.contains(file.getContentType()))
            throw new BadRequestException("허용되지 않는 파일 형식");
        if (file.getSize() > 10 * 1024 * 1024)
            throw new BadRequestException("10MB 초과");

        String filename = UUID.randomUUID() + "_" +
            StringUtils.cleanPath(file.getOriginalFilename());
        Path path = Paths.get(uploadPath, filename);
        Files.copy(file.getInputStream(), path,
            StandardCopyOption.REPLACE_EXISTING);
        return "/uploads/" + filename;
    }
}