未来Scala的未来 [英] ListenableFuture to scala Future

问题描述

我正在围绕Java库编写一个小的Scala包装器.

I am in the process of writing a small scala wrapper around a java library.

java库中有一个对象QueryExecutor，它公开了2种方法:

The java library has an object QueryExecutor exposing 2 methods:

• 执行(查询):结果
• asyncExecute(query):ListenableFuture [Result]

ListenableFuture在此上下文中是番石榴库中的那个.

ListenableFuture in this context is the one from the guava library.

我希望我的Scala包装器返回Future [Result]而不是java对象，但是我不确定实现该目标的最佳方法是什么.这是我想出的2种解决方案:

I want my scala wrapper to return a Future[Result] instead of the java object, but I am not sure what is the best way to implement that. Here are 2 solutions I came up with:

future {
  executor.execute(query)
}

和

val p = promise[Result]
val guavaFuture = executor.asyncExecute(query)

Futures.addCallback(guavaFuture, new FutureCallback[Result] {
  def onFailure(t: Throwable) {
    p.failure(t)
  }

  def onSuccess(result: Result) {
    p.success(result)
  }
})

p.future

我想知道哪种方法是最好的.我的直觉是，第一个在返回Future的同时仍然会阻塞线程，而执行调用等待响应，而第二个看起来确实应该是非阻塞的.对每种方法的利弊有何评论?

I am wondering which method is the best. My intuition is that the first one, while returning a Future, will still block a thread while the call to execute waits for a response, the second one looks like it should be really non blocking. Any comment on the pros/cons of each method ?

推荐答案

第二个选项是最好的，它可以使所有内容保持异步.但是...您可以做得更好，并将解决方案抽象为可重用的模式:

The second option is best, it keeps everything asynchronous. but... you can do one better and abstract the solution into a reusable pattern:

implicit class RichListenableFuture[T](lf: ListenableFuture[T]) {
  def asScala: Future[T] = {
    val p = Promise[T]()
    Futures.addCallback(lf, new FutureCallback[T] {
      def onFailure(t: Throwable): Unit = p failure t
      def onSuccess(result: T): Unit    = p success result
    })
    p.future
  }    
}

然后您可以简单地致电:

You can then simply call:

executor.asyncExecute(query).asScala

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