Streaming Requests

MoreBodyPublishers provides publishers for asynchronously streaming the request body into an OutputStream or a WritableByteChannel.

Let's say your sever supports compressed requests. If you're sending a large file, you'd want to send it in gzip.

final Methanol client = Methanol.create();
final Executor executor = Executors.newVirtualThreadPerTaskExecutor();

HttpResponse<Void> postGzipped(Path file) {
  return client.send(
      MutableRequest.POST(
              "https://example.com",
              MoreBodyPublishers.ofOutputStream(
                  out -> Files.copy(file, out), executor))
          .header("Content-Encoding", "gzip"),
      BodyHandlers.discarding());
}

MoreBodyPublishers::ofOutputStream accepts a callback that takes the OutputStream to stream to. The callback is invoked on the given executor. The stream may buffer content temporarily in case the consumer can't keep up with the producer, or till an inner buffer becomes full. You can use OutputStream::flushto make any buffered content available for consumption. The stream is closed automatically after the callback. If the callback fails, the request is completed exceptionally.

As of 1.8.0, this is the recommended way for streaming requests rather than using WritableBodyPublisher directly.