reactor.core.publisher.Mono.switchIfEmpty()方法的使用及代码示例

x33g5p2x  于2022-01-24 转载在 其他  
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本文整理了Java中reactor.core.publisher.Mono.switchIfEmpty()方法的一些代码示例，展示了Mono.switchIfEmpty()的具体用法。这些代码示例主要来源于Github/Stackoverflow/Maven等平台，是从一些精选项目中提取出来的代码，具有较强的参考意义，能在一定程度帮忙到你。Mono.switchIfEmpty()方法的具体详情如下：
包路径：reactor.core.publisher.Mono
类名称：Mono
方法名：switchIfEmpty

Mono.switchIfEmpty介绍

[英]Fallback to an alternative Mono if this mono is completed without data
[中]如果此单声道在没有数据的情况下完成，则返回到备用单声道

代码示例

代码示例来源：origin: codecentric/spring-boot-admin

@Override
  public Mono<Endpoints> detectEndpoints(Instance instance) {
    Mono<Endpoints> result = Mono.empty();
    for (EndpointDetectionStrategy delegate : delegates) {
      result = result.switchIfEmpty(delegate.detectEndpoints(instance));
    }
    return result.switchIfEmpty(Mono.just(Endpoints.empty()));
  }
}

代码示例来源：origin: spring-projects/spring-framework

@Override
public Mono<HandlerFunction<ServerResponse>> route(ServerRequest request) {
  return this.first.route(request)
      .map(RouterFunctions::cast)
      .switchIfEmpty(Mono.defer(() -> this.second.route(request).map(RouterFunctions::cast)));
}

代码示例来源：origin: spring-projects/spring-framework

@Override
protected Mono<Resource> resolveResourceInternal(@Nullable ServerWebExchange exchange,
    String requestPath, List<? extends Resource> locations, ResourceResolverChain chain) {
  return chain.resolveResource(exchange, requestPath, locations)
      .switchIfEmpty(Mono.defer(() ->
          resolveVersionedResource(exchange, requestPath, locations, chain)));
}

代码示例来源：origin: codecentric/spring-boot-admin

@Override
public Mono<Instance> compute(InstanceId id, BiFunction<InstanceId, Instance, Mono<Instance>> remappingFunction) {
  return this.find(id)
        .flatMap(application -> remappingFunction.apply(id, application))
        .switchIfEmpty(Mono.defer(() -> remappingFunction.apply(id, null)))
        .flatMap(this::save)
        .retryWhen(retryOnOptimisticLockException);
}

代码示例来源：origin: spring-projects/spring-framework

@Override
protected Mono<Resource> resolveResourceInternal(@Nullable ServerWebExchange exchange,
    String requestPath, List<? extends Resource> locations, ResourceResolverChain chain) {
  return chain.resolveResource(exchange, requestPath, locations)
      .switchIfEmpty(Mono.defer(() -> {
        String webJarsResourcePath = findWebJarResourcePath(requestPath);
        if (webJarsResourcePath != null) {
          return chain.resolveResource(exchange, webJarsResourcePath, locations);
        }
        else {
          return Mono.empty();
        }
      }));
}

代码示例来源：origin: spring-projects/spring-framework

@Override
public Mono<HandlerFunction<T>> route(ServerRequest request) {
  return this.first.route(request)
      .switchIfEmpty(Mono.defer(() -> this.second.route(request)));
}

代码示例来源：origin: spring-projects/spring-framework

@Override
protected Mono<String> resolveUrlPathInternal(String resourceUrlPath,
    List<? extends Resource> locations, ResourceResolverChain chain) {
  return chain.resolveUrlPath(resourceUrlPath, locations)
      .switchIfEmpty(Mono.defer(() -> {
        String webJarResourcePath = findWebJarResourcePath(resourceUrlPath);
        if (webJarResourcePath != null) {
          return chain.resolveUrlPath(webJarResourcePath, locations);
        }
        else {
          return Mono.empty();
        }
      }));
}

代码示例来源：origin: spring-projects/spring-framework

private <T> Mono<ResponseEntity<T>> toEntityInternal(Mono<T> bodyMono) {
  HttpHeaders headers = headers().asHttpHeaders();
  int status = rawStatusCode();
  return bodyMono
      .map(body -> createEntity(body, headers, status))
      .switchIfEmpty(Mono.defer(
          () -> Mono.just(createEntity(headers, status))));
}

代码示例来源：origin: spring-projects/spring-framework

@SuppressWarnings("unchecked")
private static Mono<MultiValueMap<String, String>> initFormData(ServerHttpRequest request,
    List<HttpMessageReader<?>> readers) {
  try {
    MediaType contentType = request.getHeaders().getContentType();
    if (MediaType.APPLICATION_FORM_URLENCODED.isCompatibleWith(contentType)) {
      return ((HttpMessageReader<MultiValueMap<String, String>>) readers.stream()
          .filter(reader -> reader.canRead(FORM_DATA_TYPE, MediaType.APPLICATION_FORM_URLENCODED))
          .findFirst()
          .orElseThrow(() -> new IllegalStateException("No form data HttpMessageReader.")))
          .readMono(FORM_DATA_TYPE, request, Hints.none())
          .switchIfEmpty(EMPTY_FORM_DATA)
          .cache();
    }
  }
  catch (InvalidMediaTypeException ex) {
    // Ignore
  }
  return EMPTY_FORM_DATA;
}

代码示例来源：origin: spring-projects/spring-framework

@SuppressWarnings("unchecked")
private static Mono<MultiValueMap<String, Part>> initMultipartData(ServerHttpRequest request,
    List<HttpMessageReader<?>> readers) {
  try {
    MediaType contentType = request.getHeaders().getContentType();
    if (MediaType.MULTIPART_FORM_DATA.isCompatibleWith(contentType)) {
      return ((HttpMessageReader<MultiValueMap<String, Part>>) readers.stream()
          .filter(reader -> reader.canRead(MULTIPART_DATA_TYPE, MediaType.MULTIPART_FORM_DATA))
          .findFirst()
          .orElseThrow(() -> new IllegalStateException("No multipart HttpMessageReader.")))
          .readMono(MULTIPART_DATA_TYPE, request, Hints.none())
          .switchIfEmpty(EMPTY_MULTIPART_DATA)
          .cache();
    }
  }
  catch (InvalidMediaTypeException ex) {
    // Ignore
  }
  return EMPTY_MULTIPART_DATA;
}
@Override

代码示例来源：origin: codecentric/spring-boot-admin

public static ExchangeFilterFunction setInstance(Mono<Instance> instance) {
  return (request, next) -> instance.map(i -> ClientRequest.from(request)
                               .attribute(ATTRIBUTE_INSTANCE, i)
                               .build())
                   .switchIfEmpty(request.url().isAbsolute() ? Mono.just(request) : Mono.error(
                     new ResolveInstanceException("Could not resolve Instance")))
                   .flatMap(next::exchange);
}

代码示例来源：origin: spring-projects/spring-framework

@SuppressWarnings("unchecked")
private static Mono<MultiValueMap<String, String>> initFormData(ServerHttpRequest request,
    ServerCodecConfigurer configurer, String logPrefix) {
  try {
    MediaType contentType = request.getHeaders().getContentType();
    if (MediaType.APPLICATION_FORM_URLENCODED.isCompatibleWith(contentType)) {
      return ((HttpMessageReader<MultiValueMap<String, String>>) configurer.getReaders().stream()
          .filter(reader -> reader.canRead(FORM_DATA_TYPE, MediaType.APPLICATION_FORM_URLENCODED))
          .findFirst()
          .orElseThrow(() -> new IllegalStateException("No form data HttpMessageReader.")))
          .readMono(FORM_DATA_TYPE, request, Hints.from(Hints.LOG_PREFIX_HINT, logPrefix))
          .switchIfEmpty(EMPTY_FORM_DATA)
          .cache();
    }
  }
  catch (InvalidMediaTypeException ex) {
    // Ignore
  }
  return EMPTY_FORM_DATA;
}

代码示例来源：origin: spring-projects/spring-framework

@SuppressWarnings("unchecked")
private static Mono<MultiValueMap<String, Part>> initMultipartData(ServerHttpRequest request,
    ServerCodecConfigurer configurer, String logPrefix) {
  try {
    MediaType contentType = request.getHeaders().getContentType();
    if (MediaType.MULTIPART_FORM_DATA.isCompatibleWith(contentType)) {
      return ((HttpMessageReader<MultiValueMap<String, Part>>) configurer.getReaders().stream()
          .filter(reader -> reader.canRead(MULTIPART_DATA_TYPE, MediaType.MULTIPART_FORM_DATA))
          .findFirst()
          .orElseThrow(() -> new IllegalStateException("No multipart HttpMessageReader.")))
          .readMono(MULTIPART_DATA_TYPE, request, Hints.from(Hints.LOG_PREFIX_HINT, logPrefix))
          .switchIfEmpty(EMPTY_MULTIPART_DATA)
          .cache();
    }
  }
  catch (InvalidMediaTypeException ex) {
    // Ignore
  }
  return EMPTY_MULTIPART_DATA;
}

代码示例来源：origin: spring-projects/spring-framework

@Override
public Mono<Void> handle(ServerWebExchange exchange) {
  if (this.handlerMappings == null) {
    return createNotFoundError();
  }
  return Flux.fromIterable(this.handlerMappings)
      .concatMap(mapping -> mapping.getHandler(exchange))
      .next()
      .switchIfEmpty(createNotFoundError())
      .flatMap(handler -> invokeHandler(exchange, handler))
      .flatMap(result -> handleResult(exchange, result));
}

代码示例来源：origin: codecentric/spring-boot-admin

protected Mono<ClientResponse> forward(String instanceId,
                    URI uri,
                    HttpMethod method,
                    HttpHeaders headers,
                    Supplier<BodyInserter<?, ? super ClientHttpRequest>> bodyInserter) {
  log.trace("Proxy-Request for instance {} with URL '{}'", instanceId, uri);
  return registry.getInstance(InstanceId.of(instanceId))
          .flatMap(instance -> forward(instance, uri, method, headers, bodyInserter))
          .switchIfEmpty(Mono.fromSupplier(() -> ClientResponse.create(HttpStatus.SERVICE_UNAVAILABLE, strategies).build()));
}

代码示例来源：origin: spring-projects/spring-framework

@Override
protected Mono<Void> writeToInternal(ServerWebExchange exchange, Context context) {
  MediaType contentType = exchange.getResponse().getHeaders().getContentType();
  Locale locale = LocaleContextHolder.getLocale(exchange.getLocaleContext());
  Stream<ViewResolver> viewResolverStream = context.viewResolvers().stream();
  return Flux.fromStream(viewResolverStream)
      .concatMap(viewResolver -> viewResolver.resolveViewName(name(), locale))
      .next()
      .switchIfEmpty(Mono.error(() ->
          new IllegalArgumentException("Could not resolve view with name '" + name() + "'")))
      .flatMap(view -> {
        List<MediaType> mediaTypes = view.getSupportedMediaTypes();
        return view.render(model(),
            contentType == null && !mediaTypes.isEmpty() ? mediaTypes.get(0) : contentType,
            exchange);
      });
}

代码示例来源：origin: spring-projects/spring-framework

@Override
public Mono<ClientResponse> exchange() {
  ClientRequest request = (this.inserter != null ?
      initRequestBuilder().body(this.inserter).build() :
      initRequestBuilder().build());
  return exchangeFunction.exchange(request).switchIfEmpty(NO_HTTP_CLIENT_RESPONSE_ERROR);
}

代码示例来源：origin: spring-projects/spring-framework

@Override
public Mono<Object> resolveArgument(
    MethodParameter parameter, BindingContext bindingContext, ServerWebExchange exchange) {
  NamedValueInfo namedValueInfo = getNamedValueInfo(parameter);
  MethodParameter nestedParameter = parameter.nestedIfOptional();
  Object resolvedName = resolveStringValue(namedValueInfo.name);
  if (resolvedName == null) {
    return Mono.error(new IllegalArgumentException(
        "Specified name must not resolve to null: [" + namedValueInfo.name + "]"));
  }
  Model model = bindingContext.getModel();
  return resolveName(resolvedName.toString(), nestedParameter, exchange)
      .flatMap(arg -> {
        if ("".equals(arg) && namedValueInfo.defaultValue != null) {
          arg = resolveStringValue(namedValueInfo.defaultValue);
        }
        arg = applyConversion(arg, namedValueInfo, parameter, bindingContext, exchange);
        handleResolvedValue(arg, namedValueInfo.name, parameter, model, exchange);
        return Mono.justOrEmpty(arg);
      })
      .switchIfEmpty(getDefaultValue(
          namedValueInfo, parameter, bindingContext, model, exchange));
}

代码示例来源：origin: spring-projects/spring-framework

@SuppressWarnings("unchecked")
@Override
public Mono<Void> write(Publisher<? extends T> inputStream, ResolvableType elementType,
    @Nullable MediaType mediaType, ReactiveHttpOutputMessage message, Map<String, Object> hints) {
  MediaType contentType = updateContentType(message, mediaType);
  Flux<DataBuffer> body = this.encoder.encode(
      inputStream, message.bufferFactory(), elementType, contentType, hints);
  if (inputStream instanceof Mono) {
    HttpHeaders headers = message.getHeaders();
    return Mono.from(body)
        .switchIfEmpty(Mono.defer(() -> {
          headers.setContentLength(0);
          return message.setComplete().then(Mono.empty());
        }))
        .flatMap(buffer -> {
          headers.setContentLength(buffer.readableByteCount());
          return message.writeWith(Mono.just(buffer));
        });
  }
  return (isStreamingMediaType(contentType) ?
      message.writeAndFlushWith(body.map(Flux::just)) : message.writeWith(body));
}

代码示例来源：origin: spring-projects/spring-framework

@Override
public Mono<WebSession> getSession(ServerWebExchange exchange) {
  return Mono.defer(() -> retrieveSession(exchange)
      .switchIfEmpty(this.sessionStore.createWebSession())
      .doOnNext(session -> exchange.getResponse().beforeCommit(() -> save(exchange, session))));
}

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