Scala actor与非actor的交互（或将消息从actor同步到servlet） [英] Scala actor to non-actor interaction (or synchronizing messages from an actor to a servlet)
问题描述
我有以下scala代码：
I have the following scala code:
package dummy
import javax.servlet.http.{HttpServlet,
HttpServletRequest => HSReq, HttpServletResponse => HSResp}
import scala.actors.Actor
class DummyServlet extends HttpServlet {
RNG.start
override def doGet(req: HSReq, resp: HSResp) = {
def message = <HTML><HEAD><TITLE>RandomNumber </TITLE></HEAD><BODY>
Random number = {getRandom}</BODY></HTML>
resp.getWriter().print(message)
def getRandom: String = {var d = new DummyActor;d.start;d.getRandom}
}
class DummyActor extends Actor {
var result = "0"
def act = { RNG ! GetRandom
react { case (r:Int) => result = r.toString }
}
def getRandom:String = {
Thread.sleep(300)
result
}
}
}
// below code is not modifiable. I am using it as a library
case object GetRandom
object RNG extends Actor {
def act{loop{react{case GetRandom=>sender!scala.util.Random.nextInt}}}
}
在上面的代码中，我必须使用 thread.sleep 以确保有足够的时间用于更新 ，否则 0 返回。在不使用 thread.sleep 的情况下，这样做更优雅的方法是什么？我认为我必须使用期货，但是我无法理解这个概念。我需要确保每个HTTP重新请求都获得一个唯一的随机数（当然，随机数只是为了解释问题）。某些提示或参考将不胜感激。
In the above code, I have to use thread.sleep to ensure that there is enough time for result to get updated, otherwise 0 is returned. What is a more elegant way of doing this without using thread.sleep? I think I have to use futures but I cannot get my head around the concept. I need to ensure that each HTTP reaquest gets a unique random number (of course, the random number is just to explain the problem). Some hints or references would be appreciated.
推荐答案
无论哪种使用：
!! <-返回一个可以等待的未来
!! <-- Returns a Future that you can wait for
或
！？ <-使用带有超时的命令，完全同步是危险的
!? <-- Use the one with a timeout, the totally synchronous is dangerous
鉴于您对RNG的定义，这里有一些REPL代码来验证：
Given your definition of RNG, heres some REPL code to verify:
scala> def foo = { println(RNG.!?(1000,GetRandom)) }
foo: Unit
scala> foo
Some(-1025916420)
scala> foo
Some(-1689041124)
scala> foo
Some(-1633665186)
文档在这里：> http://www.scala-lang.org/api/current/scala/actors/Actor .html
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