Just to clarify something...
Each CompositeFuture.any/all do some async operations that return
futures, lets say myList1, myList2, myList3, but I must wait for
CompositeFuture.any(myList1) to complete and return success before
doing CompositeFuture.any(myList2), and the same from myList2 to
myList3.
You've offered CompositeFuture.any() and CompositeFuture.all() as points of reference, but the behavior you describe is consistent with all(), which is to say the resulting composite will yield success only if all its constituents do.
For the purpose of my answer, I'm assuming all() is the behavior you expect.
In RxJava, an unexpected error triggered by an exception will result in termination of the stream with the underlying exception being delivered to the observer via the onError() callback.
As a small demo, assume the following setup:
final Single<String> a1 = Single.just("Batch-A-Operation-1");
final Single<String> a2 = Single.just("Batch-A-Operation-2");
final Single<String> a3 = Single.just("Batch-A-Operation-3");
final Single<String> b1 = Single.just("Batch-B-Operation-1");
final Single<String> b2 = Single.just("Batch-B-Operation-2");
final Single<String> b3 = Single.just("Batch-B-Operation-3");
final Single<String> c1 = Single.just("Batch-C-Operation-1");
final Single<String> c2 = Single.just("Batch-C-Operation-2");
final Single<String> c3 = Single.just("Batch-C-Operation-3");
Each Single represents a discrete operation to be performed, and they are logically named according to some logical grouping (ie they are meant to be executed together). For example, "Batch-A" corresponds to your "myList1", "Batch-B" to your "myList2", ...
Assume the following stream:
Single
.zip(a1, a2, a3, (s, s2, s3) -> {
return "A's completed successfully";
})
.flatMap((Function<String, SingleSource<String>>) s -> {
throw new RuntimeException("B's failed");
})
.flatMap((Function<String, SingleSource<String>>) s -> {
return Single.zip(c1, c2, c3, (one, two, three) -> "C's completed successfully");
})
.subscribe(
s -> System.out.println("## onSuccess(" + s + ")"),
t -> System.out.println("## onError(" + t.getMessage() + ")")
);
(If you're not familiar, the zip() operator can be used to combine the results of all the sources supplied as input to emit another/new source).
In this stream, because the processing of the B's ends up throwing an exception:
- the stream is terminated during the execution of the B's
- the exception is reported to the observer (ie the
onError() handler is triggered)
- the C's are never processed
If what you want, however, is to decide for yourself whether or not to execute each branch, one approach you could take is to pass the results from previous operations down the stream using some sort of state holder, like so:
class State {
final String value;
final Throwable error;
State(String value, Throwable error) {
this.value = value;
this.error = error;
}
}
The stream could then be modified to conditionally execute different batches, for example:
Single
.zip(a1, a2, a3, (s, s2, s3) -> {
try {
// Execute the A's here...
return new State("A's completed successfully", null);
} catch(Throwable t) {
return new State(null, t);
}
})
.flatMap((Function<State, SingleSource<State>>) s -> {
if(s.error != null) {
// If an error occurred upstream, skip this batch...
return Single.just(s);
} else {
try {
// ...otherwise, execute the B's
return Single.just(new State("B's completed successfully", null));
} catch(Throwable t) {
return Single.just(new State(null, t));
}
}
})
.flatMap((Function<State, SingleSource<State>>) s -> {
if(s.error != null) {
// If an error occurred upstream, skip this batch...
return Single.just(s);
} else {
try {
// ...otherwise, execute the C's
return Single.just(new State("C's completed successfully", null));
} catch(Throwable t) {
return Single.just(new State(null, t));
}
}
})
.subscribe(
s -> {
if(s.error != null) {
System.out.println("## onSuccess with error: " + s.error.getMessage());
} else {
System.out.println("## onSuccess without error: " + s.value);
}
},
t -> System.out.println("## onError(" + t.getMessage() + ")")
);
