bodyPublisher.contentLength() Always returns -1

[ghost]

    public List<TorrentContent> addTorrent(Path torrentPath) {
        try (HttpClient httpClient = HttpClient
                .newBuilder()
                .version(HttpClient.Version.HTTP_1_1)
                .build()) {
            MultipartFormDataBodyPublisher bodyPublisher = new MultipartFormDataBodyPublisher();
            bodyPublisher.addFile("torrents",torrentPath);
//            bodyPublisher.addStream("torrents", "a.torrent", () -> stream, "application/octet-stream");
            String uri = "http://127.0.0.1/1.php";//qbBaseUrl + "/api/v2/torrents/add";
            System.out.println("length: " + bodyPublisher.contentLength()  + " uri : " + uri + " type:" + bodyPublisher.contentType());
            HttpRequest httpRequest = HttpRequest.newBuilder()
                    .uri(URI.create(uri))
                    .expectContinue(true)
                    .version(HttpClient.Version.HTTP_1_1)
                    .method("POST",bodyPublisher)
                    .build();
            HttpResponse<String> response = httpClient.send(httpRequest, HttpResponse.BodyHandlers.ofString());
            System.out.println("body: " + response.body());
        } catch (IOException | InterruptedException e) {
            throw new RuntimeException(e);
        }

        return null;
    }