我有下面的代码，我想知道，为什么当我执行它时，它会立即停止：

import akka.actor.ActorSystem
    import akka.http.scaladsl.Http
    import akka.http.scaladsl.model._
    import akka.http.scaladsl.server.Directives._
    import akka.stream.ActorMaterializer
    import scala.io.StdIn
    object WebServer {
      def main(args: Array[String]) {
    
        implicit val system = ActorSystem("my-system")
        implicit val materializer = ActorMaterializer()
        // needed for the future flatMap/onComplete in the end
        implicit val executionContext = system.dispatcher
    
        val route =
          path("hello") {
            get {
              complete(HttpEntity(ContentTypes.`text/html(UTF-8)`, "<h1>Say hello to akka-http</h1>"))
            }
          }
    
        val bindingFuture = Http().bindAndHandle(route, "localhost", 8080)
        bindingFuture
          .flatMap(_.unbind()) // trigger unbinding from the port
          .onComplete(_ => system.terminate()) // and shutdown when done
      }
    }

字符串
正如你所看到的，它是一个简单的Web应用程序，它不应该停止运行。
但是当我删除以下代码时：

bindingFuture
  .flatMap(_.unbind()) // trigger unbinding from the port
  .onComplete(_ => system.terminate()) // and shutdown when done

型
它会一直运行直到我终止它。
问题是，为什么没有

bindingFuture
  .flatMap(_.unbind()) // trigger unbinding from the port
  .onComplete(_ => system.terminate()) // and shutdown when done

型
申请不会终止吗

val bindingFuture = Http().bindAndHandle(route, "localhost", 8080)
println(s"Server online at http://localhost:8080/\nPress RETURN to stop...")
StdIn.readLine() // let it run until user presses return
bindingFuture
.flatMap(_.unbind()) // trigger unbinding from the port
.onComplete(_ => system.terminate()) // and shutdown when done

// Just build a Future that will get completed when you want to shutdown
// This can be done manually using a `Promise[Unit]`, but you might also be using
// a library that will give you a Future to wait on.
val myFuture: Future[Unit] = ???
myFuture.flatMap(_ => bindingFuture)
.flatMap(_.unbind())
.onComplete(_ => system.terminate())

1条答案

按热度按时间

o4hqfura1#

你的bindingFuture在这两种情况下都完成了。

字符串
然后，unbind和terminate会在服务器侦听时立即运行，这会导致程序立即完成。
如果你忽略了这段代码，那么你的程序会一直运行，直到所有的线程都运行完。因为参与者系统是在后台运行线程的，你从来不会终止它，所以这种情况永远不会发生，你必须杀死你的程序来停止它。
一种在任何按键时都能正常关机的方法是使用这个（取自official documentation）

val bindingFuture = Http().bindAndHandle(route, "localhost", 8080)
println(s"Server online at http://localhost:8080/\nPress RETURN to stop...")
StdIn.readLine() // let it run until user presses return
bindingFuture
  .flatMap(_.unbind()) // trigger unbinding from the port
  .onComplete(_ => system.terminate()) // and shutdown when done

型
在这种情况下，StdIn.readLine()将阻塞主线程，直到按下某个键，此时执行元系统和http服务器将关闭。
如果你想等待一个自定义的“事件”而不是一个按键，你可以简单地等待一个自定义的Future，如下所示：

// Just build a Future that will get completed when you want to shutdown
// This can be done manually using a `Promise[Unit]`, but you might also be using 
// a library that will give you a Future to wait on.
val myFuture: Future[Unit] = ??? 
myFuture.flatMap(_ => bindingFuture)
    .flatMap(_.unbind())
    .onComplete(_ => system.terminate())

型

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赞(0）回复(0）举报 2023-11-18

akka 为什么会立即终止？

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