如何处理单声道转换为单声道时的错误

我必须提供api，它执行多个api调用，然后组合它们并返回单个

class MyDto {
  private ItemA itemA;
  private ItemB itemB;
  private List<ItemC> itemCList;
 //constructor
}

首先我得到mono，然后我将user传递给api调用，然后使用mono.zip组合响应，最后使用rxjava2adapter.monotosingle将响应转换为single

return RxJava2Adapter.monoToSingle(
               userService.getUserById(id)
                    .flatMap(user -> Mono.zip(
                        getMonoItemA(user),
                        getMonoItemB(user),
                        getFluxItemC(user).collectList(),
                        .map(data -> new MyDto(data.getT3(), data.getT2(), data.getT1()))));

当我请求时，我的服务器就冻结了，我得到了一个错误：

io.reactivex.exceptions.CompositeException: 2 exceptions occurred. 
    at io.reactivex.internal.operators.single.SingleDoOnError$DoOnError.onError(SingleDoOnError.java:61)
    at io.reactivex.internal.operators.single.SingleDoOnSuccess$DoOnSuccess.onSuccess(SingleDoOnSuccess.java:56)
    at io.reactivex.internal.operators.single.SingleFromPublisher$ToSingleObserver.onComplete(SingleFromPublisher.java:101)
    at reactor.core.publisher.StrictSubscriber.onComplete(StrictSubscriber.java:123)
    at reactor.core.publisher.Operators$MonoSubscriber.complete(Operators.java:1624)
Caused by: io.reactivex.exceptions.CompositeException$CompositeExceptionCausalChain: Chain of Causes for CompositeException In Order Received =>
    at io.reactivex.exceptions.CompositeException.getCause(CompositeException.java:110)
    at com.eisgroup.genesis.facade.FacadeErrorResponseFactory.lambda$resolveErrorStrategy$3(FacadeErrorResponseFactory.java:59)
    at java.base/java.util.Optional.or(Optional.java:318)
    at com.eisgroup.genesis.facade.FacadeErrorResponseFactory.resolveErrorStrategy(FacadeErrorResponseFactory.java:59)
    at com.eisgroup.genesis.facade.FacadeErrorResponseFactory.createErrorResponse(FacadeErrorResponseFactory.java:48)
Caused by: java.lang.NullPointerException: null
    at com.eisgroup.genesis.trace.config.RxAwareScope.close(RxAwareScope.java:34)
    at com.eisgroup.genesis.facade.servlet.request.RequestDispatcher.invokeAfterInvocation(RequestDispatcher.java:314)
    at com.eisgroup.genesis.facade.servlet.request.RequestDispatcher.lambda$invokeAfterInvocation$21(RequestDispatcher.java:301)
    at io.reactivex.internal.operators.single.SingleDoOnSuccess$DoOnSuccess.onSuccess(SingleDoOnSuccess.java:53)
    at io.reactivex.internal.operators.single.SingleFromPublisher$ToSingleObserver.onComplete(SingleFromPublisher.java:101)
Caused by: java.lang.NullPointerException: null
    at com.eisgroup.genesis.trace.config.RxAwareScope.close(RxAwareScope.java:34)
    at com.eisgroup.genesis.facade.servlet.request.RequestDispatcher.lambda$invokeAfterInvocation$23(RequestDispatcher.java:305)
    at io.reactivex.internal.operators.single.SingleDoOnError$DoOnError.onError(SingleDoOnError.java:58)
    at io.reactivex.internal.operators.single.SingleDoOnSuccess$DoOnSuccess.onSuccess(SingleDoOnSuccess.java:56)
    at io.reactivex.internal.operators.single.SingleFromPublisher$ToSingleObserver.onComplete(SingleFromPublisher.java:101)

我尝试在出现错误或空响应的情况下添加默认返回（每个方法），但没有帮助

getFluxItemC(user).collectList()
    .switchIfEmpty(Mono.defer(() -> Mono.just(new ArrayList<>())
    .onErrorReturn(new ArrayList<>())

getItemA(user)
    .switchIfEmpty(Mono.defer(() -> Mono.just(new ItemA)
    .onErrorReturn(new ItemA)

rxjava新手，不知道如何处理此错误

在查看stacktrace时，很明显在#doonsuccess lambda中抛出了一个错误

Publisher
  .toSingle()
  .doOnSuccess(value -> ....)

io.reactivex.internal.operators.single.singledoonsuccess.doonsuccess

@Override
    public void onSuccess(T value) {
        try {
            onSuccess.accept(value);
        } catch (Throwable ex) {
            Exceptions.throwIfFatal(ex);
            downstream.onError(ex);
            return;
        }
        downstream.onSuccess(value);
    }

似乎调用了lamdba，抛出了一个异常，并将异常作为onerror传播到订阅服务器。
问题很可能发生在这里：
在com.eisgroup.genesis.trace.config.rxawarescope.close（rxawarescope。java:34)
你可以修复这个npe或者删除doonsuccess日志来运行它。

关于，为什么onerrorreturn不起作用。

事实上，如果没有适当的语境，很难说出来。我只能提供一些指导。#onerrorreturn运算符必须在抛出错误的运算符（doonsuccess）下面，以便正确处理错误。如果onerrorreturn在doonsucces运算符的上方，则onerror将传播到订阅服务器。
为了进一步帮助你，我需要更多的代码在里面，特别是facaderrorresponsefactory。

假设

return RxJava2Adapter.monoToSingle(
               userService.getUserById(id)
                    .flatMap(user -> Mono.zip(
                        getMonoItemA(user),
                        getMonoItemB(user),
                        getFluxItemC(user).collectList(),
                        .map(data -> new MyDto(data.getT3(), data.getT2(), data.getT1()))));

monotosingle在onerrorreturn后添加#tosingle（）#doonsuccess。因此，错误处理程序位于错误的位置，因此将异常转换为备份值。你能告诉我们monotosingle是如何实现的吗？

如何处理单声道转换为单声道时的错误

1条答案

关于，为什么onerrorreturn不起作用。

假设

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