如何使用 Reactor 3.x 将 List 转换为 Flux

我有一个异步调用节俭接口：

public CompletableFuture<List<Long>> getFavourites(Long userId){
    CompletableFuture<List<Long>> future = new CompletableFuture();
    OctoThriftCallback callback = new OctoThriftCallback(thriftExecutor);
    callback.addObserver(new OctoObserver() {
        @Override
        public void onSuccess(Object o) {
            future.complete((List<Long>) o);
        }

        @Override
        public void onFailure(Throwable throwable) {
            future.completeExceptionally(throwable);
        }
    });
    try {
        recommendAsyncService.getFavorites(userId, callback);
    } catch (TException e) {
        log.error("OctoCall RecommendAsyncService.getFavorites", e);
    }
    return future;
}

现在它返回一个 CompletableFuture。然后我用 Flux 调用它来做一些处理器。

public Flux<Product> getRecommend(Long userId) throws InterruptedException, ExecutionException, TimeoutException {
    // do not like it
    List<Long> recommendList = wrapper.getRecommend(userId).get(2, TimeUnit.SECONDS);

    System.out.println(recommendList);
    return Flux.fromIterable(recommendList)
            .flatMap(id -> Mono.defer(() -> Mono.just(Product.builder()
                    .userId(userId)
                    .productId(id)
                    .productType((int) (Math.random()*100))
                    .build())))
            .take(5)
            .publishOn(mdpScheduler);
}

但是，我想从getFavourites方法，我可以用它getRecommend method.
或者，您可以推荐一个Flux API，我可以转换List<Long> recommendList to Flux<Long> recommendFlux.

要转换一个CompletableFuture<List<T>> into a Flux<T>您可以使用Mono#fromFuture https://projectreactor.io/docs/core/release/api/reactor/core/publisher/Mono.html#fromFuture-java.util.concurrent.CompletableFuture- with Mono#flatMapMany https://projectreactor.io/docs/core/release/api/reactor/core/publisher/Mono.html#flatMapMany-java.util.function.Function-:

var future = new CompletableFuture<List<Long>>();
future.completeAsync(() -> List.of(1L, 2L, 3L, 4L, 5L),
    CompletableFuture.delayedExecutor(3, TimeUnit.SECONDS));

Flux<Long> flux = Mono.fromFuture(future).flatMapMany(Flux::fromIterable);

flux.subscribe(System.out::println);

List<T>在回调中异步接收也可以转换为Flux<T>不使用CompletableFuture。 您可以直接使用Mono#create https://projectreactor.io/docs/core/release/api/reactor/core/publisher/Mono.html#create-java.util.function.Consumer- with Mono#flatMapMany https://projectreactor.io/docs/core/release/api/reactor/core/publisher/Mono.html#flatMapMany-java.util.function.Function-:

Flux<Long> flux = Mono.<List<Long>>create(sink -> {
  Callback<List<Long>> callback = new Callback<List<Long>>() {
    @Override
    public void onResult(List<Long> list) {
      sink.success(list);
    }

    @Override
    public void onError(Exception e) {
      sink.error(e);
    }
  };
  client.call("query", callback);
}).flatMapMany(Flux::fromIterable);

flux.subscribe(System.out::println);

或者简单地使用Flux#create https://projectreactor.io/docs/core/release/api/reactor/core/publisher/Flux.html#create-java.util.function.Consumer-一次通过多次发射：

Flux<Long> flux = Flux.create(sink -> {
  Callback<List<Long>> callback = new Callback<List<Long>>() {
    @Override
    public void onResult(List<Long> list) {
      list.forEach(sink::next);
    }

    @Override
    public void onError(Exception e) {
      sink.error(e);
    }
  };
  client.call("query", callback);
});

flux.subscribe(System.out::println);