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

With recent stable Spring WebFlux (5.2.4.RELEASE as of writing):

final WebClient client = WebClient.create("https://example.com");
final Flux dataBufferFlux = client.get()
        .accept(MediaType.TEXT_HTML)
        .retrieve()
        .bodyToFlux(DataBuffer.class); // the magic happens here

final Path path = FileSystems.getDefault().getPath("target/example.html");
DataBufferUtils
        .write(dataBufferFlux, path, CREATE_NEW)
        .block(); // only block here if the rest of your code is synchronous

For me the non-obvious part was the bodyToFlux(DataBuffer.class), as it is currently mentioned within a generic section about streaming of Spring's documentation, there is no direct reference to it in the WebClient section.