在 WebFlux WebClient 中测试状态码时如何获取响应正文？

Question

在尝试根据返回的状态码抛出异常时如何检索响应正文？例如，假设我想抛出异常并拒绝 HTTP 201。

client.post().exchange().doOnSuccess(response -> {
    if (response.statusCode().value() == 201) {
        throw new RuntimeException();
    }
}

如何使用响应的正文填充异常，以便我可以抛出详细的WebClientResponseException？

我应该使用不同的方法来测试响应状态代码吗？

编辑：我正在尝试复制以下功能，同时改用exchange()。

client.get()
    .retrieve()
    .onStatus(s -> !HttpStatus.CREATED.equals(s),
        MyClass::createResponseException);

//MyClass
public static Mono<WebClientResponseException> createResponseException(ClientResponse response) {
    return response.body(BodyExtractors.toDataBuffers())
            .reduce(DataBuffer::write)
            .map(dataBuffer -> {
                byte[] bytes = new byte[dataBuffer.readableByteCount()];
                dataBuffer.read(bytes);
                DataBufferUtils.release(dataBuffer);
                return bytes;
            })
            .defaultIfEmpty(new byte[0])
            .map(bodyBytes -> {
                String msg = String.format("ClientResponse has erroneous status code: %d %s", response.statusCode().value(),
                        response.statusCode().getReasonPhrase());
                Charset charset = response.headers().contentType()
                        .map(MimeType::getCharset)
                        .orElse(StandardCharsets.ISO_8859_1);
                return new WebClientResponseException(msg,
                        response.statusCode().value(),
                        response.statusCode().getReasonPhrase(),
                        response.headers().asHttpHeaders(),
                        bodyBytes,
                        charset
                        );
            });
}

Answer 1

您可以通过自定义 ExchangeFilterFunction 并在构建 WebClient 之前将其与 WebClient.Builder 挂钩来实现此目的。

public static ExchangeFilterFunction errorHandlingFilter() {
        return ExchangeFilterFunction.ofResponseProcessor(clientResponse -> {
            if(clientResponse.statusCode()!=null && (clientResponse.statusCode().is5xxServerError() || clientResponse.statusCode().is4xxClientError()) ) {
                 return clientResponse.bodyToMono(String.class)
                         .flatMap(errorBody -> {
                             return Mono.error(new CustomWebClientResponseException(errorBody,clientResponse.statusCode()));
                             });
            }else {
                return Mono.just(clientResponse);
            }
        });
    }

你可以像这样使用上面的：

WebClient.builder()
                .clientConnector(new ReactorClientHttpConnector(clientOptions))
                .defaultHeader(HttpHeaders.USER_AGENT, "Application")
                .filter(WebClientUtil.errorHandlingFilter())
                .baseUrl("https://httpbin.org/")
                .build()
                .post()
                .uri("/post")
                .body(BodyInserters.fromObject(customObjectReference) )
                .exchange()
                .flatMap(response -> response.toEntity(String.class) );

因此，任何 4XX 或 5XX HttpResponse 实际上都会抛出 CustomWebClientResponseException ，您可以配置一些全局异常处理程序并使用它做您喜欢的事情。至少使用 ExchangeFilterFunction，您可以拥有全局位置来处理此类事情或添加自定义标头和内容。

Answer 2

经过反复试验，我得到了以下似乎可以解决问题的方法。

Mono<ClientResponse> mono = client.get().exchange()
        .flatMap(response -> {
            if (HttpStatus.CREATED.equals(response.statusCode())) {
                return Mono.just(response);
            } else {
                return response.body(BodyExtractors.toDataBuffers())
                        .reduce(DataBuffer::write)
                        .map(dataBuffer -> {
                            byte[] bytes = new byte[dataBuffer.readableByteCount()];
                            dataBuffer.read(bytes);
                            DataBufferUtils.release(dataBuffer);
                            return bytes;
                        })
                        .defaultIfEmpty(new byte[0])
                        .flatMap(bodyBytes -> {
                            String msg = String.format("ClientResponse has erroneous status code: %d %s", response.statusCode().value(),
                                    response.statusCode().getReasonPhrase());
                            Charset charset = response.headers().contentType()
                                    .map(MimeType::getCharset)
                                    .orElse(StandardCharsets.ISO_8859_1);
                            return Mono.error(new WebClientResponseException(msg,
                                    response.statusCode().value(),
                                    response.statusCode().getReasonPhrase(),
                                    response.headers().asHttpHeaders(),
                                    bodyBytes,
                                    charset
                                    ));
                        });
            }
        })
        .retry(3);
final CompletableFuture<ClientResponse> future = mono.toFuture();

Answer 3

doOn** 操作符是副作用操作符，例如应该用于记录目的。

在这里，您希望在管道级别实现该行为，因此onStatus 更适合这里：

Mono<ClientHttpResponse> clientResponse = client.post().uri("/resource")
    .retrieve()
    .onStatus(httpStatus -> HttpStatus.CREATED.equals(httpStatus), 
        response -> response.bodyToMono(String.class).map(body -> new MyException(body)))
    bodyToXYZ(...);

或者

Mono<ResponseEntity<String>> result = client.post().uri("/resource")
    .exchange()
    .flatMap(response -> response.toEntity(String.class))
    .flatMap(entity -> {
        // return Mono.just(entity) or Mono.error() depending on the response 
    });

请注意，如果您期望大型响应主体，则获取整个响应主体可能不是一个好主意；在这种情况下，您将在内存中缓冲大量数据。