java - 带有 Mono.empty() 参数的响应式(Reactive) Java Mono.zip

Question

使用 Spring 和 Reactor 项目将多个 api 调用压缩为聚合结果。 带 Mono.empty() 参数的 Mono.zip() 可以返回 null 结果吗？

Mono<Dog> dogMono = dogApiClient.getDog(); // can return Mono.empty()
Mono<Cat> catMono = catMono = catApiClient.getCat(); // can returnMono.empty()
Mono<Horse> horseMono = horseApiClient.getHorse(); // can return Mono.empty()

Mono.zip(dogMono, dogMobo, horseMono)
  .map(this::mapToAnimals);

预期结果:

{
  dog: null, // if dog is null
  cat: null, // if cat is null
  horse: null, // if horse is null
}

实际结果:

{
  dog: {
    name: null,
    surname: null
  }, 
  cat: {
    name: null,
    surname: null
  }, 
  horse: {
    name: null,
    surname: null
  }
}

或

"" // empty

Answer 1

嗯，这当然不是一个优雅的解决方案，但您可以选择将您的值包装在可选中:

Mono<Optional<Dog>> dogMono = Mono.just(Optional.empty());
if(condition1) {
    dogMono = dogApiClient.getDog().map(Optional::of);
}

Mono<Optional<Cat>> catMono = Mono.just(Optional.empty());
if(condition2) {
    catMono = catApiClient.getCat().map(Optional::of);
}

Mono<Optional<Horse>> horseMono = Mono.just(Optional.empty());
if(condition3) {
    horseMono = horseApiClient.getHorse().map(Optional::of);
}

Mono.zip(dogMono, catMono, horseMono)
    .map(this::mapToAnimals);

private Output mapToAnimals(Tuple3<Optional<Dog>, Optional<Cat>, Optional<Horse>> tuple3)
{
    Dog dog = tuple3.getT1().orElse(null);
    Cat cat = tuple3.getT2().orElse(null);
    Horse horse = tuple3.getT3().orElse(null);

    return new Output(dog, cat, horse);
}