从Scala Future处理Await.result的异常

Question

I have a for comprehension in Scala and I want to handle an Exception of the Await.result. The problem is that my catch shows None.get , but not my exception that I defined.

The exception is caught at case e: Exception => BadRequest(s"Exception found: ${e.getMessage}") but it is a Future. I would like to show the getMessage.

try {
  val futureResult = for {
    futureRackRow <- rackRepository.getById(rack.id) recoverWith {
      case e: Exception => throw RackException(s"Error on select Rack: ${e.getMessage}")
    }
    futureSeqGpuRow <- gpuRepository.getByRack(futureRackRow.get.id) recoverWith {
      case e: Exception => throw GpuException(s"Error on select Gpu's from Rack: ${e.getMessage}")
    }
  } yield (futureRackRow, futureSeqGpuRow)
  println(2)
  val result = Await.result(futureResult, 20 seconds) // The exception comes here ....

  result._1 match {
    case Some(rackRow) => ???
    case None => ???
  }
  Ok
} catch {
  case re: RackException => BadRequest(s"Rack Exception: ${re.getMessage}")
  case ge: GpuException => BadRequest(s"Gpu Exception: ${ge.getMessage}")
  case e: Exception => BadRequest(s"Exception found: ${e.getMessage}")
}

Answer 1

I'd assume you get the exception with None.get is that the futureRackRow is None here. Then before even calling getByRack it will throw an Exception for calling .id on it. Thus it has nothing to do with the Futures :)

Best catch it before the block, like

if (futureRackRow.nonEmpty) {
  ...
}

or if you have some default value you could use this instead of the .get.id

 futureRackRow.map(_.id).getOrElse(0)