Spring WebClient: How to stream large byte[] to file?

Question

It seems like it the Spring RestTemplate isn\'t able to stream a response directly to file without buffering it all in memory. What is the proper to achieve this us

Answer 1

I cannot test whether or not the following code effectively does not buffer the contents of webClient payload in memory. Nevertheless, i think you should start from there:

public Mono testWebClientStreaming() throws IOException {
    Flux stream = 
            webClient
                    .get().accept(MediaType.APPLICATION_OCTET_STREAM)
                    .retrieve()
            .bodyToFlux(DataBuffer.class);
    Path filePath = Paths.get("filename");
    AsynchronousFileChannel asynchronousFileChannel = AsynchronousFileChannel.open(filePath, WRITE);
    return DataBufferUtils.write(stream, asynchronousFileChannel)
            .doOnNext(DataBufferUtils.releaseConsumer())
            .doAfterTerminate(() -> {
                try {
                    asynchronousFileChannel.close();
                } catch (IOException ignored) { }
            }).then();
}