23

似乎SpringRestTemplate无法将响应直接流式传输到文件而不将其全部缓冲在内存中。使用较新的 Spring 5 实现这一目标的正确方法是什么WebClient？

WebClient client = WebClient.create("https://example.com");
client.get().uri(".../{name}", name).accept(MediaType.APPLICATION_OCTET_STREAM)
                    ....?

我看到人们已经找到了一些解决这个问题的方法/技巧RestTemplate，但我更感兴趣的是使用WebClient.

有许多RestTemplate用于下载二进制数据的示例，但几乎所有示例都将其加载byte[]到内存中。

4

4 回答 4

13

使用最近稳定的 Spring WebFlux（撰写时为 5.2.4.RELEASE）：

final WebClient client = WebClient.create("https://example.com");
final Flux<DataBuffer> 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

对我来说，不明显的部分是bodyToFlux(DataBuffer.class)，因为它目前在关于 Spring 文档流的通用部分中提到，在 WebClient 部分中没有直接引用它。

于 2020-03-17T15:15:53.367 回答
3

我无法测试以下代码是否有效地没有缓冲webClient内存中有效负载的内容。不过，我认为你应该从那里开始：

public Mono<Void> testWebClientStreaming() throws IOException {
    Flux<DataBuffer> 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();
}
于 2019-05-23T14:45:02.937 回答
1

将正文存储到临时文件并使用

static <R> Mono<R> writeBodyToTempFileAndApply(
        final WebClient.ResponseSpec spec,
        final Function<? super Path, ? extends R> function) {
    return using(
            () -> createTempFile(null, null),
            t -> write(spec.bodyToFlux(DataBuffer.class), t)
                    .thenReturn(function.apply(t)),
            t -> {
                try {
                    deleteIfExists(t);
                } catch (final IOException ioe) {
                    throw new RuntimeException(ioe);
                }
            }
    );
}

管身体和消耗

static <R> Mono<R> pipeBodyAndApply(
        final WebClient.ResponseSpec spec, final ExecutorService executor,
        final Function<? super ReadableByteChannel, ? extends R> function) {
    return using(
            Pipe::open,
            p -> {
                final Future<Disposable> future = executor.submit(
                        () -> write(spec.bodyToFlux(DataBuffer.class), p.sink())
                                .log()
                                .doFinally(s -> {
                                    try {
                                        p.sink().close();
                                        log.debug("p.sink closed");
                                    } catch (final IOException ioe) {
                                        throw new RuntimeException(ioe);
                                    }
                                })
                                .subscribe(DataBufferUtils.releaseConsumer())
                );
                return just(function.apply(p.source()))
                        .log()
                        .doFinally(s -> {
                            try {
                                final Disposable disposable = future.get();
                                assert disposable.isDisposed();
                            } catch (InterruptedException | ExecutionException e) {
                                e.printStackTrace();
                            }
                        });
            },
            p -> {
                try {
                    p.source().close();
                    log.debug("p.source closed");
                } catch (final IOException ioe) {
                    throw new RuntimeException(ioe);
                }
            }
    );
}
于 2019-10-05T05:36:44.667 回答
-1

我不确定您是否可以使用RestTemplate当前使用的 spring，但是这个对我有用。


RestTemplate restTemplate // = ...;

RequestCallback requestCallback = request -> request.getHeaders()
        .setAccept(Arrays.asList(MediaType.APPLICATION_OCTET_STREAM, MediaType.ALL));

// Streams the response
ResponseExtractor<Void> responseExtractor = response -> {
    // Here I write the response to a file but do what you like
    Path path = Paths.get("http://some/path");
    Files.copy(response.getBody(), path);
    return null;
};
restTemplate.execute(URI.create("www.something.com"), HttpMethod.GET, requestCallback, responseExtractor);
于 2019-05-26T12:44:07.423 回答