Outputstream start writing when inputstream starts reading

I want to send a big object (lets say 4G) over http.

We have a custom serializer that writes the object to an OutputStream. At the moment we write the object to disk and use that file for the inputstream which is used for the request.

Something like these lines:

private static Response sendObject(Object bigObject) throws IOException {
  File tempFile = File.createTempFile("x", "y");
  OutputStream out = new FileOutputStream(tempFile);
  CustomSerializer.serialize(bigObject, out);
  out.close();

  WebTarget resource = service.path("data");

  FormDataMultiPart multiPartEntity = new FormDataMultiPart();

  InputStream inputStream = new FileInputStream(tempFile);
  StreamDataBodyPart streamBodyPart = new StreamDataBodyPart(
        "data",
        inputStream,
        "data",
        MediaType.APPLICATION_OCTET_STREAM_TYPE);

  MultiPart multiPart = multiPartEntity.bodyPart(streamBodyPart);
  return resource.request(MediaType.APPLICATION_JSON_TYPE)
        .post(Entity.entity(multiPart, multiPart.getMediaType()));
 }

We save some memory because we don't serialize to a byte array in memory. Thats nice. But could I save the memory without writing to disk.

Could you write directly to the input stream without rewriting the CustomSerializer?

Could you write directly to the input stream while it reads into the request?

-

It is a little hard to explain, But I think I am after something like this pseudo code:

private static Response sendObject(Object bigObject) throws IOException {
  WebTarget resource = service.path("data");

  FormDataMultiPart multiPartEntity = new FormDataMultiPart();

  OutputStream outIn = new OutputInputStream() {
     public void openInputStream() {
        CustomSerializer.serialize(bigObject, this);
     }
  };
  StreamDataBodyPart streamBodyPart = new StreamDataBodyPart(
        "data",
        outIn.getInputStream(),
        "data",
        MediaType.APPLICATION_OCTET_STREAM_TYPE);

  MultiPart multiPart = multiPartEntity.bodyPart(streamBodyPart);
  return resource.request(MediaType.APPLICATION_JSON_TYPE)
        .post(Entity.entity(multiPart, multiPart.getMediaType()));
}