助焊剂（或类似物），如果空的助焊剂

Question

如果通量为空，如何调用方法（消费者），例如，如果通量为空，我想记录消息

Answer 1

这个为您服务：

/**
 * Add behavior (side-effect) triggered when the {@link Flux} completes successfully.
 * <p>
 * <img class="marble" src="doc-files/marbles/doOnComplete.svg" alt="">
 *
 * @param onComplete the callback to call on {@link Subscriber#onComplete}
 *
 * @return an observed  {@link Flux}
 */
public final Flux<T> doOnComplete(Runnable onComplete) {

请参阅此JavaDocs：

/**
 * Represents an empty publisher which only calls onSubscribe and onComplete.
 * <p>
 * This Publisher is effectively stateless and only a single instance exists.
 * Use the {@link #instance()} method to obtain a properly type-parametrized view of it.
 * @see <a href="https://github.com/reactor/reactive-streams-commons">Reactive-Streams-Commons</a>
 */
final class FluxEmpty extends Flux<Object>

Answer 2

我看到两种实现方法：

1. 用途switchIfEmpty()

然后您的代码段将具有以下表示形式：

.switchIfEmpty(Flux.empty().doOnComplete(() -> log.info("there were no elements")))

2. 另一个选项是hasElements()，您可以将其放置在链的末尾。

   .hasElements()
   .doOnNext(hasElements -> {
       if (!hasElements) {
           log.info("there were no elements");
       }
   })