Vertx：executeBlocking() 与 Future。有什么不同？

Question

Vertx 文档建议executeBlocking()在需要调用阻塞 API 时使用方法。另一方面，Vertx 还提供了一个 Future 的概念，它基本上做同样的事情。但该executeBlocking()方法不是静态的。它也不是 Future 的简单包装器，如果您查看它的实现，您会发现它非常复杂。这两者有什么区别？假设我想以异步方式执行一些长时间运行的任务。这两种方法有什么区别吗？方法一：doTheJob() {    Future<Void> future = Future.future();    executeLongRunningBlockingOperation();    future.complete();    return future;}doTheJob().setHandler(asyncResult -> {    // ... handle result});方法二：vertx.executeBlocking(future -> {    executeLongRunningBlockingOperation();    future.complete();}, res -> {    // ... handle result});

Answer 1

您的第一个示例不是Future. 调用executeLongRunningBlockingOperation()将阻塞主线程，直到该方法完成——也就是说，在阻塞操作完成之前不会发生任何其他事情。在您的第二个示例中，阻塞调用被分拆到后台线程中，并且其他事情在它执行时继续发生。

为了用更完整的示例说明这一点，此代码：

public void executeLongRunningBlockingOperation() {

    Thread.sleep(5000);

}

public Future<Void> doTheJob() { 

    System.out.println("Doing the job...");

    Future<Void> future = Future.future();

    executeLongRunningBlockingOperation();

    // this line will not be called until executeLongRunningBlockingOperation returns!

    future.complete();

    // nor will this method! This means that the method won't return until the long operation is done!

    return future;

}

public static void main(String[] args) {

    doTheJob().setHandler(asyncResult -> {

        System.out.println("Finished the job");

    });

    System.out.println("Doing other stuff in the mean time...");

}

将产生以下输出：

Doing the job...

Finished the job

Doing other stuff in the mean time...

而这段代码（使用executeBlocking）：

...

public Future<Void> doTheJob() { 

    System.out.println("Doing the job...");

    Future<Void> future = Future.future();

    Vertx vertx = Vertx.vertx();

    vertx.executeBlocking(call -> {

        executeLongRunningBlockingOperation();

        call.complete;

    }, result -> {

        // this will only be called once the blocking operation is done

        future.complete();

    });

    // this method returns immediately since we are not blocking the main thread

    return future;

}

...

将产生：

Doing the job...

Doing other stuff in the mean time...

Finished the job