如何正确读取 Flux 并将其转换为单个 inputStream

我在用着WebClient和定制BodyExtractor我的 spring-boot 应用程序的类

WebClient webLCient = WebClient.create();
webClient.get()
   .uri(url, params)
   .accept(MediaType.APPLICATION.XML)
   .exchange()
   .flatMap(response -> {
     return response.body(new BodyExtractor());
   })

BodyExtractor.java

@Override
public Mono<T> extract(ClientHttpResponse response, BodyExtractor.Context context) {
  Flux<DataBuffer> body = response.getBody();
  body.map(dataBuffer -> {
    try {
      JaxBContext jc = JaxBContext.newInstance(SomeClass.class);
      Unmarshaller unmarshaller = jc.createUnmarshaller();

      return (T) unmarshaller.unmarshal(dataBuffer.asInputStream())
    } catch(Exception e){
       return null;
    }
  }).next();
}

上面的代码适用于小有效负载，但不适用于大有效负载，我认为这是因为我只读取单个通量值next我不知道如何组合并阅读所有内容dataBuffer.

我是reactor的新手，所以我不知道很多flux/mono的技巧。

这实际上并不像其他答案所暗示的那么复杂。

流式传输数据而不将其全部缓冲在内存中的唯一方法是使用管道，如 @jin-kwon 建议的那样。然而，使用 Spring 可以非常简单地完成身体提取器 https://docs.spring.io/spring-framework/docs/current/javadoc-api/org/springframework/web/reactive/function/BodyExtractors.html and 数据缓冲区工具 https://docs.spring.io/spring-framework/docs/current/javadoc-api/org/springframework/core/io/buffer/DataBufferUtils.html实用程序类。

Example:

private InputStream readAsInputStream(String url) throws IOException {
    PipedOutputStream osPipe = new PipedOutputStream();
    PipedInputStream isPipe = new PipedInputStream(osPipe);

    ClientResponse response = webClient.get().uri(url)
        .accept(MediaType.APPLICATION.XML)
        .exchange()
        .block();
    final int statusCode = response.rawStatusCode();
    // check HTTP status code, can throw exception if needed
    // ....

    Flux<DataBuffer> body = response.body(BodyExtractors.toDataBuffers())
        .doOnError(t -> {
            log.error("Error reading body.", t);
            // close pipe to force InputStream to error,
            // otherwise the returned InputStream will hang forever if an error occurs
            try(isPipe) {
              //no-op
            } catch (IOException ioe) {
                log.error("Error closing streams", ioe);
            }
        })
        .doFinally(s -> {
            try(osPipe) {
              //no-op
            } catch (IOException ioe) {
                log.error("Error closing streams", ioe);
            }
        });

    DataBufferUtils.write(body, osPipe)
        .subscribe(DataBufferUtils.releaseConsumer());

    return isPipe;
}

如果您不关心检查响应代码或引发失败状态代码的异常，则可以跳过block()调用和中间ClientResponse变量通过使用

flatMap(r -> r.body(BodyExtractors.toDataBuffers()))

instead.