热身如弦从春反应ClientRequest？

Question

在测试方法中，接收到org.springframework.web.reactive.function.client.ClientRequest的实例。

我想验证它的HttpMethod、URI和body。

很明显，除了身体之外，如何获得所有东西都是显而易见的。

ClientRequest request = makeInstance(...);

assertEquals(HttpMethod.POST, request.method());
assertEquals("somewhere/else", request.url().toString());

// ? unclear how to extract body using the BodyInserter

BodyInserter<?, ? super ClientHttpRequest> inserter = request.body();

inserter.insert(%outputMessage%, %context%);

我在Spring 如何测试BodyInserters的源代码中找到了。如何创建BodyInserter.Context (第二个参数)比较清楚，但我无法理解如何构造第一个参数，因此可以通过它提取请求体。

请展示一种从ClientRequest实例获取请求体的传统(或至少可用的)方法。

Answer 1

对于这样一个简单的例子来说有点复杂，但我需要实现5个类，才能从ClientRequest中提取一个身体。

这似乎太多了，我仍然很好奇这个问题是否有一个简短的解决方案。欢迎你对这个问题提出另一个答案，这样我就可以接受了。

不幸的是，必须指出的是，ClientRequest、BodyInserters和大多数来自org.springframework.web.reactive.***的其他东西的设计还有很大的改进空间。目前，它只是一堆接口，每个方法都有大量的方法，根据这些类的不同，测试代码通常需要付出很大的努力。

实现此方法的主要目标是：

static <T> T extractBody(ClientRequest request, Class<T> clazz) {

  InsertionReceiver<T> receiver = InsertionReceiver.forClass(clazz);
  return receiver.receiveValue(request.body());
}

下面是InsertionReceiver的实现

1. ​

import org.springframework.http.ReactiveHttpOutputMessage;
import org.springframework.web.reactive.function.BodyInserter;

public interface InsertionReceiver<T> {

  T receiveValue(BodyInserter<?, ? extends ReactiveHttpOutputMessage> bodyInserter);

  static <T> InsertionReceiver<T> forClass(Class<T> clazz) {
    return new SimpleValueReceiver<>(clazz);
  }
}

1. ​

import java.util.concurrent.atomic.AtomicReference;
import org.springframework.http.ReactiveHttpOutputMessage;
import org.springframework.web.reactive.function.BodyInserter;
    
class SimpleValueReceiver<T> implements InsertionReceiver<T> {

  private static final Object DUMMY = new Object();

  private final Class<T> clazz;
  private final AtomicReference<Object> reference;

  SimpleValueReceiver(Class<T> clazz) {
    this.clazz = clazz;
    this.reference = new AtomicReference<>(DUMMY);
  }

  @Override
  public T receiveValue(BodyInserter<?, ? extends ReactiveHttpOutputMessage> bodyInserter) {
    demandValueFrom(bodyInserter);

    return receivedValue();
  }

  private void demandValueFrom(BodyInserter<?, ? extends ReactiveHttpOutputMessage> bodyInserter) {    
    var inserter = (BodyInserter<?, ReactiveHttpOutputMessage>) bodyInserter;

    inserter.insert(
        MinimalHttpOutputMessage.INSTANCE,
        new SingleWriterContext(new WriteToConsumer<>(reference::set))
    );
  }

  private T receivedValue() {
    Object value = reference.get();
    reference.set(DUMMY);

    T validatedValue;

    if (value == DUMMY) {
      throw new RuntimeException("Value was not received, Check your inserter worked properly");
    } else if (!clazz.isAssignableFrom(value.getClass())) {
      throw new RuntimeException(
          "Value has unexpected type ("
              + value.getClass().getTypeName()
              + ") instead of (" + clazz.getTypeName() + ")");
    } else {
      validatedValue = clazz.cast(value);
    }

    return validatedValue;
  }
}

1. ​

class WriteToConsumer<T> implements HttpMessageWriter<T> {

  private final Consumer<T> consumer;
  private final List<MediaType> mediaTypes;

  WriteToConsumer(Consumer<T> consumer) {
    this.consumer = consumer;
    this.mediaTypes = Collections.singletonList(MediaType.ALL);
  }

  @Override
  public List<MediaType> getWritableMediaTypes() {
    return mediaTypes;
  }

  @Override
  public boolean canWrite(ResolvableType elementType, MediaType mediaType) {
    return true;
  }

  @Override
  public Mono<Void> write(
      Publisher<? extends T> inputStream,
      ResolvableType elementType,
      MediaType mediaType,
      ReactiveHttpOutputMessage message,
      Map<String, Object> hints
  ) {
    inputStream.subscribe(new OneValueConsumption<>(consumer));
    return Mono.empty();
  }
}

1. ​

class MinimalHttpOutputMessage implements ReactiveHttpOutputMessage {

  public static MinimalHttpOutputMessage INSTANCE = new MinimalHttpOutputMessage();

  private MinimalHttpOutputMessage() {
  }

  @Override
  public HttpHeaders getHeaders() {
    return HttpHeaders.EMPTY;
  }

  // other overridden methods are omitted as they do nothing,
  // i.e. return null, false, or have empty bodies
}

1. ​

class OneValueConsumption<T> implements Subscriber<T> {

  private final Consumer<T> consumer;
  private int remainedAccepts;

  public OneValueConsumption(Consumer<T> consumer) {
    this.consumer = Objects.requireNonNull(consumer);
    this.remainedAccepts = 1;
  }

  @Override
  public void onSubscribe(Subscription s) {
    s.request(1);
  }

  @Override
  public void onNext(T o) {
    if (remainedAccepts > 0) {
      consumer.accept(o);
      remainedAccepts -= 1;
    } else {
      throw new RuntimeException("No more values can be consumed");
    }
  }

  @Override
  public void onError(Throwable t) {
    throw new RuntimeException("Single value was not consumed", t);
  }

  @Override
  public void onComplete() {
    // nothing
  }
}

1. ​

class SingleWriterContext implements BodyInserter.Context {

  private final List<HttpMessageWriter<?>> singleWriterList;

  SingleWriterContext(HttpMessageWriter<?> writer) {
    this.singleWriterList = List.of(writer);
  }

  @Override
  public List<HttpMessageWriter<?>> messageWriters() {
    return singleWriterList;
  }

  @Override
  public Optional<ServerHttpRequest> serverRequest() {
    return Optional.empty();
  }

  @Override
  public Map<String, Object> hints() {
    return null;
  }
}

Answer 2

我找到了一个相对简单的方法来实现这一点，那就是模仿BodyInserters.fromValue()来实现您自己的BodyInserter。

public static class CustomerInserter<T> implements BodyInserter<T, ReactiveHttpOutputMessage> {

    private T body;

    private CustomerInserter(T body) {
        this.body = body;
    }

    public static <T> CustomerInserter<T> fromValue(T body) {
        return new CustomerInserter<T>(body);
    }

    public T getBody() {
        return this.body;
    }

    @Override
    public Mono<Void> insert(ReactiveHttpOutputMessage outputMessage, Context context) {
        Mono<T> publisher = Mono.just(this.body);
        MediaType mediaType = outputMessage.getHeaders().getContentType();
        ResolvableType bodyType = ResolvableType.forInstance(this.body);
        return context.messageWriters().stream()
                .filter(messageWriter -> messageWriter.canWrite(bodyType, mediaType))
                .findFirst()
                .map(item -> (HttpMessageWriter<T>) item)
                .map(writer -> this.write(publisher, bodyType, mediaType, outputMessage, context, writer))
                .orElseGet(() -> Mono.error(unsupportedError(bodyType, context, mediaType)));
    }

    private Mono<Void> write(Publisher<? extends T> input, ResolvableType type,
                                        @Nullable MediaType mediaType, ReactiveHttpOutputMessage message,
                                        BodyInserter.Context context, HttpMessageWriter<T> writer) {

        return context.serverRequest()
                .map(request -> {
                    ServerHttpResponse response = (ServerHttpResponse) message;
                    return writer.write(input, type, type, mediaType, request, response, context.hints());
                })
                .orElseGet(() -> writer.write(input, type, mediaType, message, context.hints()));
    }

    private UnsupportedMediaTypeException unsupportedError(ResolvableType bodyType,
                                                   BodyInserter.Context context, @Nullable MediaType mediaType) {

        List<MediaType> supportedMediaTypes = context.messageWriters().stream()
                .flatMap(reader -> reader.getWritableMediaTypes(bodyType).stream())
                .collect(Collectors.toList());

        return new UnsupportedMediaTypeException(mediaType, supportedMediaTypes, bodyType);
    }
}

简单的单元测试。

Response response = webClient.post()
            .uri("/xxx")
            .body(CustomerInserter.fromValue(body)) //
            .retrieve()
            .bodyToMono(Response.class)
            .block();

WebClient webClient = WebClient.builder()
            .baseUrl("http://127.0.0.1:8080")
            .filter((request, next) -> {
                CustomerInserter<?> inserter = (CustomerInserter<?>) request.body();
                // Some things can be done here
                Object body = inserter.getBody();
                return next.exchange(request);
            }).build();