Send received spring FilePart without saving

Question

I need to send FilePart received in RestController to API using WebClient, how can I do this?

Found an example, which saves image to disk.

private static String UPLOAD_ROOT = "C:\\pics\\";

public Mono<Void> checkInTest(@RequestPart("photo") Flux<FilePart> photoParts,
                              @RequestPart("data") CheckInParams params, Principal principal) {
    return saveFileToDisk(photoParts);
}

private Mono<Void> saveFileToDisk(Flux<FilePart> parts) {
    return parts
            .log("createImage-files")
            .flatMap(file -> {
                Mono<Void> copyFile = Mono.just(Paths.get(UPLOAD_ROOT, file.filename()).toFile())
                        .log("createImage-picktarget")
                        .map(destFile -> {
                            try {
                                destFile.createNewFile();
                                return destFile;
                            } catch (IOException e) {
                                throw new RuntimeException(e);
                            }
                        })
                        .log("createImage-newfile")
                        .flatMap(file::transferTo)
                        .log("createImage-copy");

                return Mono.when(copyFile)
                        .log("createImage-when");
            })
            .log("createImage-flatMap")
            .then()
            .log("createImage-done");
}

Then read it again and send to anoter server

.map(destFile -> {
        MultiValueMap<String, Object> map = new LinkedMultiValueMap<>();
        try {
            map.set("multipartFile", new ByteArrayResource(FileUtils.readFileToByteArray(destFile)));
        } catch (IOException ignored) {
        }
        map.set("fileName", "test.txt");
        WebClient client = WebClient.builder().baseUrl("http://localhost:8080").build();

        return client.post()
                .uri("/upload")
                .contentType(MediaType.MULTIPART_FORM_DATA)
                .syncBody(map)
                .exchange(); //todo handle errors???
    }).then()

Is there way to avoid saving file?

Answer 1

I will mention solution by @Abhinaba Chakraborty
provided in https://stackoverflow.com/a/62745370/4551411

Probably something like this:

  @PostMapping(value = "/images/upload", consumes = MediaType.MULTIPART_FORM_DATA_VALUE)
  public Mono<ResponseEntity<Void>> uploadImages(@RequestPart("files") Flux<FilePart> fileParts) {
    return fileParts
        .flatMap(filePart -> {
          return webClient.post()
              .uri("/someOtherService")
              .body(BodyInserters.fromPublisher(filePart.content(), DataBuffer.class))
              .exchange()
              .flatMap(clientResponse -> {
                //some logging
                return Mono.empty();
              });
        })
        .collectList()
        .flatMap(response -> Mono.just(ResponseEntity.accepted().build()));
  }

This accepts MULTIPART FORM DATA where you can attach multiple image files and upload them to another service.