将 Try 转换为 Future 并将 recoverWith 转换为 Future

Question

我有一个 Try 抛出异常。我希望 Try 变成 Future 这样我就可以 recoverWith.

如何在不处理 Try 中的任何异常的情况下将 Try 转换为 Future（仅在将来恢复）？

注意需要Await来测试你未来的结果

代码示例展示了我的想法，但一旦达到它也会抛出（new RuntimeException("-------failed-------") 是我得到的）

val t = Try(throw new RuntimeException("my"))

val resF : Future[String] = if (t.isSuccess)
  Future.successful(t.get)
else
  Future.failed(new RuntimeException("-------failed-------"))

val resFWithRecover = resF.recoverWith{
  case NonFatal(e) =>
    Future.successful("recoveredWith")
}
Await.result(resFWithRecover, Duration("5s"))

Answer 1

您也可以 recoverWith 在 Try 上

在Try上使用map和recover方法分别生成Future.successful和Future.failed，然后在[=13=上使用get ]

val future = 
 Try {
   throw new Exception("explosion")
 }.map { result =>
   Future.successful(result)
 }.recover { case th =>
   Future.failed(th)
 }.get

使用模式匹配

val future =  
 Try {
  throw new Exception("something")
 } match {
  case Success(value) => Future.successful(value)
  case Failure(th) => Future.failed(th)
 }

Answer 2

... how do convert Try to Future without handling any exception in the Try?

使用Future.fromTry.

scala> val t = Try(throw new RuntimeException("my"))
t: scala.util.Try[Nothing] = Failure(java.lang.RuntimeException: my)

scala> val resF = Future.fromTry(t)
resF: scala.concurrent.Future[Nothing] = scala.concurrent.impl.Promise$KeptPromise@57cf54e1

scala> resF.recoverWith{
     |   case NonFatal(e) =>
     |     Future.successful("recoveredWith")
     | }
res5: scala.concurrent.Future[String] = scala.concurrent.impl.Promise$DefaultPromise@1b75c2e3

Answer 3

没有必要介绍 Future 如果你只想使用 recoverWith（有点像 flatMap) 在你的 Try 对象上。

你可以这样：

val t = Try[String](throw new RuntimeException("my"))
val u = t.recoverWith{
  case e => Success(s"ignoring exception ${e.getLocalizedMessage}")
}
u.foreach(println(_))

这会导致向控制台输出以下内容：

ignoring exception my

Answer 4

 // you need to provide your try with type information in lhs
 // as the rhs is not providing any type info
 val t: Try[String] = Try(throw new RuntimeException("my"))

 // Now you can easily get a Future[String] from this Try[String]
 val f = Future.fromTry(t)

 // or you can use pattern matching
 val f2 = t match {
   case Success(str) => Future.succesful(str)
   case Failure(ex) => Future.failed(ex)
 }

将 Try 转换为 Future 并将 recoverWith 转换为 Future

Convert Try to Future and recoverWith as Future

scala

concurrency

future