java - 带有 Mono.empty() 参数的反应式 Java Mono.zip
问题描述
使用 Spring 和 Reactor Project 将多个 api 调用压缩为聚合结果。带有 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
}
}
或者
"" // empty
解决方案
好吧,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 Optional 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);
}