如何从另一个 Flux 中排除 Flux 中的所有元素

Question

I have two Flux s one for successful elements another one holding the erroneous elements

Flux<String> success= Flux.just("Orange", "Apple", "Banana","Grape", "Strawberry");
Flux<String> erroneous = Flux.just("Banana","Grape",);

How can i filter the first Flux to execlude all the elements from the second one?

Answer 1

You may wish to consider collecting the Flux into a set, caching that set, and then using filterWhen as follows:

Mono<Set<String>> erroneousSet = erroneous.collect(Collectors.toSet()).cache();
Flux<String> filtered = success.filterWhen(v -> erroneousSet.map(s -> !s.contains(v)));

Gives:

Orange
Apple
Strawberry

This isn't the most concise solution (see below), but it enables the contents of erroneous to be cached. In this specific example that's a moot point, but if it's a real-world situation (not using Flux.just() ) then erroneous could be recomputed on every subscription, and that could end up being incredibly (and unnecessarily) expensive in performance terms.

Alternatively, if the above really doesn't matter in your use case, filterWhen() and hasElement() can be used much more concisely as follows:

success.filterWhen(s -> erroneous.hasElement(s).map(x->!x))

Or with reactor-extra:

success.filterWhen(s -> BooleanUtils.not(erroneous.hasElement(s)))