private HandlerResultHandler getResultHandler(HandlerResult handlerResult) {
   for (HandlerResultHandler resultHandler : resultHandlers) {
     if (resultHandler.supports(handlerResult)) {
       return resultHandler;
     }
   }
   throw new IllegalStateException(
       "No HandlerResultHandler for " + handlerResult.getReturnValue());
 }
  @Override
  public Mono<Void> handleResult(ServerWebExchange exchange, HandlerResult result) {

    ResolvableType returnType = result.getReturnType();
    MethodParameter bodyType;

    Mono<?> returnValueMono;
    Optional<Object> optionalValue = result.getReturnValue();

    Class<?> rawClass = returnType.getRawClass();
    ReactiveAdapter adapter = getAdapterRegistry().getAdapterFrom(rawClass, optionalValue);

    if (adapter != null) {
      returnValueMono = adapter.toMono(optionalValue);
      bodyType = new MethodParameter(result.getReturnTypeSource());
      bodyType.increaseNestingLevel();
      bodyType.increaseNestingLevel();
    } else {
      returnValueMono = Mono.justOrEmpty(optionalValue);
      bodyType = new MethodParameter(result.getReturnTypeSource());
      bodyType.increaseNestingLevel();
    }

    return returnValueMono.then(
        returnValue -> {
          Assert.isInstanceOf(HttpEntity.class, returnValue);
          HttpEntity<?> httpEntity = (HttpEntity<?>) returnValue;

          if (httpEntity instanceof ResponseEntity) {
            ResponseEntity<?> responseEntity = (ResponseEntity<?>) httpEntity;
            exchange.getResponse().setStatusCode(responseEntity.getStatusCode());
          }

          HttpHeaders entityHeaders = httpEntity.getHeaders();
          HttpHeaders responseHeaders = exchange.getResponse().getHeaders();

          if (!entityHeaders.isEmpty()) {
            entityHeaders
                .entrySet()
                .stream()
                .filter(entry -> !responseHeaders.containsKey(entry.getKey()))
                .forEach(entry -> responseHeaders.put(entry.getKey(), entry.getValue()));
          }

          return writeBody(httpEntity.getBody(), bodyType, exchange);
        });
  }
  @Override
  public boolean supports(HandlerResult result) {
    Class<?> returnType = result.getReturnType().getRawClass();
    if (isSupportedType(returnType)) {
      return true;
    } else {
      ReactiveAdapter adapter =
          getAdapterRegistry().getAdapterFrom(returnType, result.getReturnValue());
      if (adapter != null
          && !adapter.getDescriptor().isMultiValue()
          && !adapter.getDescriptor().isNoValue()) {

        ResolvableType genericType = result.getReturnType().getGeneric(0);
        return isSupportedType(genericType.getRawClass());
      }
    }
    return false;
  }