Reactor3 源码解析十七: FluxBuffer源码剖析（1）

buffer操作主要将源生产的元素进行打包，然后交由后续的中间操作或消费者处理，有点类似于批处理。

		Flux.range(1, 100).buffer(20).subscribe(System.out::println);
		//一直收集元素,直到Predicate返回true,开启下一次收集
		Flux.range(1, 10).bufferUntil(i -> i%3 == 0).subscribe(System.out::println);
		//只收集Predicate为true为数据,当为false时下启下一次收集
		Flux.range(1, 10).bufferWhile(i -> i%3 == 0).subscribe(System.out::println);
		//每隔1s生产一个元素 ,每隔10s收集一次,共收集2次,底层为异步操作
		Flux.interval(Duration.ofSeconds(1)).buffer(Duration.ofSeconds(10)).take(2).subscribe(System.out::println);
		//.toStream().forEach(System.out::println); 转化为jdk操作
		Thread.sleep(30*1000l);

执行结果:

[1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20]
[21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40]
[41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60]
[61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80]
[81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100]
[1, 2, 3]
[4, 5, 6]
[7, 8, 9]
[10]
[3]
[6]
[9]
[0, 1, 2, 3, 4, 5, 6, 7, 8]
[9, 10, 11, 12, 13, 14, 15, 16, 17, 18]

FluxBuffer是一个中间操作，处理逻辑相对简单，重点关注下FluxBuffer#subscribeOrReturn和BufferExactSubscriber#onNext操作

FluxBuffer#subscribeOrReturn

	public CoreSubscriber<? super T> subscribeOrReturn(CoreSubscriber<? super C> actual) {
		if (size == skip) {
            //BufferExactSubscriber同时扮演Subscriber和Subscription双重角色
			return new BufferExactSubscriber<>(actual, size, bufferSupplier);
		}
		else if (skip > size) {
			return new BufferSkipSubscriber<>(actual, size, skip, bufferSupplier);
		}
		else {
			return new BufferOverlappingSubscriber<>(actual, size, skip, bufferSupplier);
		}
	}

BufferExactSubscriber#onNext

public void onNext(T t) {
			if (done) {
				Operators.onNextDropped(t, actual.currentContext());
				return;
			}
            //C是一个容器，用来存放元素
			C b = buffer;
			if (b == null) {
				try {
					b = Objects.requireNonNull(bufferSupplier.get(),
							"The bufferSupplier returned a null buffer");
				}
				catch (Throwable e) {
					Context ctx = actual.currentContext();
					onError(Operators.onOperatorError(s, e, t, ctx));
					Operators.onDiscard(t, ctx); //this is in no buffer
					return;
				}
				buffer = b;
			}

			b.add(t);
            //并不直接调用下游的actual.onNext(b)，而是在元素堆积到size时再向下游传递
            //如果最后一次收集达不到size数，则由下面的onComplete处理最后一次发送 
			if (b.size() == size) {
				buffer = null;
				actual.onNext(b);
			}
		}


        public void onComplete() {
			if (done) {
				return;
			}
			done = true;

			C b = buffer;

			if (b != null && !b.isEmpty()) {
				actual.onNext(b);
			}
			actual.onComplete();
		}