问 thenApply和thenApplyAsync of Java CompletableFuture有什么区别？

在 thenApplyAsync 和 thenApply 中，传递给这些方法的 Consumer<? super T> action 将被异步调用，不会阻塞指定使用者的线程。

这种差异与哪个线程负责调用方法 Consumer#accept(T t) 有关。

AsyncHttpClient 考虑如下所示的调用： 注意下面打印的线程名。我希望它能让你弄清楚其中的区别：

// running in the main method
// public static void main(String[] args) ....
CompletableFuture<Response> future =
    asyncHttpClient.prepareGet(uri).execute().toCompletableFuture();
log.info("Current Thread " + Thread.currentThread().getName());
//Prints "Current Thread main"

thenApply 将使用与完成未来相同的线程。

//will use the dispatcher threads from the asyncHttpClient to call `consumer.apply`
//The thread that completed the future will be blocked by the execution of the method `Consumer#accept(T t)`.
future.thenApply(myResult -> {
    log.info("Applier Thread " + Thread.currentThread().getName());
    return myResult;
//Prints: "Applier Thread httpclient-dispatch-8"

thenApplyAsync 将使用执行器池中的线程.

//will use the threads from the CommonPool to call `consumer.accept`
//The thread that completed the future WON'T be blocked by the execution of the method `Consumer#accept(T t)`.
future.thenApplyAsync(myResult -> {