缠绕的一系列异步调用与返回值的同步方法 [英] Wrapping a series of asynchronous calls with a synchronous method with a return value

问题描述

我目前的code使用，在达到高潮的结果异步进程的系列。我需要包装每个这些在于，每个由与结果作为返回值的同步方法来访问这样的方式。我想使用执行程序的服务，这样做，以便允许许多这些在同一时间发生。我有一个未来的可能是相关的我的实现的感觉，但我不能想出一个好办法做到这一点。

My current code uses series of asynchronous processes that culminate in results. I need to wrap each of these in such a way that each is accessed by a synchronous method with the result as a return value. I want to use executor services to do this, so as to allow many of these to happen at the same time. I have the feeling that Future might be pertinent to my implementation, but I can't figure out a good way to make this happen.

我现在有什么：

public class DoAJob {
  ResultObject result;

  public void stepOne() {
    // Passes self in for a callback
    otherComponent.doStepOne(this);
  }

  // Called back by otherComponent once it has completed doStepOne
  public void stepTwo(IntermediateData d) {
    otherComponent.doStepTwo(this, d);
  }

  // Called back by otherComponent once it has completed doStepTwo
  public void stepThree(ResultObject resultFromOtherComponent) {
    result = resultFromOtherComponent;
  //Done with process
  }
}

这工作pretty以及内部，但现在我需要我的过程映射到一个同步方法像一个返回值：

This has worked pretty well internally, but now I need to map my process into a synchronous method with a return value like:

public ResultObject getResult(){
  // ??? What goes here ???
}

有没有人对如何实现这个好主意优雅？

Does anyone have a good idea about how to implement this elegantly?

推荐答案

如果您想打开一个异步操作（这在完成时执行的回调），进入一个同步/阻断一个，你可以使用一个阻塞队列。如果你愿意，你可以在将来的对象包装这个了。

If you want to turn an asynchronous operation (which executes a callback when finished), into a synchronous/blocking one, you can use a blocking queue. You can wrap this up in a Future object if you wish.

1. 定义它可以容纳一个阻塞队列，只有一个元素：

1. Define a blocking queue which can hold just one element:

的BlockingQueue＆LT;结果＆GT;的BlockingQueue =新ArrayBlockingQueue＆LT;结果＆GT;（1）;

启动异步进程（将在后台运行），并写回调，这样当它完成，它增加了它的结果，以阻塞队列。

Start your asynchronous process (will run in the background), and write the callback such that when it's done, it adds its result to the blocking queue.

在您的前景/应用程序线程，它已经采取（）从队列中，而阻塞，直到元素变得可用：

In your foreground/application thread, have it take() from the queue, which blocks until an element becomes available:

结果结果= blockingQueue.take（）;

我写的（前台线程需要阻止从远程计算机的异步响应）使用类似的Future以前类似的东西，你可以找到例如code <一个href=\"http://$c$c.google.com/p/mobility-rpc/source/browse/mobility-rpc/trunk/src/main/java/com/google$c$c/mobilityrpc/session/impl/MobilitySessionImpl.java#395\"相对=nofollow>这里。

I wrote something similar before (foreground thread needs to block for an asynchronous response from a remote machine) using something like a Future, you can find example code here.

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