RxJava2中的onErrorReturn仅捕获了第一个错误

Question

I threw two exceptions in a flowable, and I used onErrorReturn to catch those exceptions. But I found that only the first exception was caught. How to catch all the exceptions?

Flowable.create(emitter -> {
    emitter.onError(new Exception("error1"));
    emitter.onError(new Exception("error2"));
    }, BackpressureStrategy.MISSING)
        .onErrorReturn(e -> {
            System.out.println("Got error " + e.getMessage());
            return "error";
        })
        .subscribe();

Output:

Got error error1
io.reactivex.exceptions.UndeliverableException: java.lang.Exception: error2
    at io.reactivex.plugins.RxJavaPlugins.onError(RxJavaPlugins.java:349)
    at io.reactivex.internal.operators.flowable.FlowableCreate$BaseEmitter.onError(FlowableCreate.java:271)
    at com.example.springboottest.SimpleApplication.lambda$main$0(SimpleApplication.java:48)
    at io.reactivex.internal.operators.flowable.FlowableCreate.subscribeActual(FlowableCreate.java:72)
    at io.reactivex.Flowable.subscribe(Flowable.java:13094)
    at io.reactivex.internal.operators.flowable.FlowableOnErrorReturn.subscribeActual(FlowableOnErrorReturn.java:33)
    at io.reactivex.Flowable.subscribe(Flowable.java:13094)
    at io.reactivex.Flowable.subscribe(Flowable.java:13030)
    at io.reactivex.Flowable.subscribe(Flowable.java:12890)
    at com.example.springboottest.SimpleApplication.main(SimpleApplication.java:54)
Caused by: java.lang.Exception: error2
    ... 8 more
Exception in thread "main" io.reactivex.exceptions.UndeliverableException: java.lang.Exception: error2
    at io.reactivex.plugins.RxJavaPlugins.onError(RxJavaPlugins.java:349)
    at io.reactivex.internal.operators.flowable.FlowableCreate$BaseEmitter.onError(FlowableCreate.java:271)
    at com.example.springboottest.SimpleApplication.lambda$main$0(SimpleApplication.java:48)
    at io.reactivex.internal.operators.flowable.FlowableCreate.subscribeActual(FlowableCreate.java:72)
    at io.reactivex.Flowable.subscribe(Flowable.java:13094)
    at io.reactivex.internal.operators.flowable.FlowableOnErrorReturn.subscribeActual(FlowableOnErrorReturn.java:33)
    at io.reactivex.Flowable.subscribe(Flowable.java:13094)
    at io.reactivex.Flowable.subscribe(Flowable.java:13030)
    at io.reactivex.Flowable.subscribe(Flowable.java:12890)
    at com.example.springboottest.SimpleApplication.main(SimpleApplication.java:54)
Caused by: java.lang.Exception: error2
    ... 8 more

Answer 1

An Observable ends after it completes or encounters an error. This is a part of the contract and there is no way around that property.

The only way you could handle 'multiple' exceptions in an observable is if it is handled like a value, not an exception. This would end up looking like Scala's Either construct in practice.