Scala - Play: how to nicely handle WS get exception - web-services

Question

I have this function which uses Play WS services:
def executeRequest(urls: List[Url]): List[Future[String]] =
urls.map(url => {
WS.url(url.url).get().map(x => url.url + ": " + x.statusText )
})
Where Url is a case class so defined:
case class Url(id: Long, url: String)
I want my application to be resilient and sometimes the url value triggers an IllegalArgumentException if the url is not well formed. What I tried was this:
def executeRequest2(urls: List[Url]): List[Future[String]] =
urls.map(url => {
WS.url(url.url).get().map(x => url.url + ": " + x.statusText )
.recover({
case e: IllegalArgumentException => url.url + " is invalid"
})
})
This doesn't work, most probably because the exception is thrown inside the .get() and not inside the future execution (it's just a guess anyway).
What I ended up doing is this:
def executeRequest(urls: List[Url]): List[Future[String]] =
urls.map(url => {
try {
WS.url(url.url).get().map(x => x.statusText)
}
catch {
case e: IllegalArgumentException => future {
url.url + " is illegal."
}
}
})
This works, but I would like some nicer and more idiomatic way to handle this exception. Note that here I haven't added the recover to handle eventual problems inside the future execution which will make this piece of code even more illegible.

Answer 1

Try is your friend here.
import scala.util.Try
urls.map(url =>
Try(WS.url(url.url).get().map(x => x.statusText))
.getOrElse(Future.successful(url.url + " is illegal."))
)
This will replace all exceptions with the error message in the getOrElse. We can be a little more fine grained than that though. Perhaps we could keep the invalid URLs as successful Future[String]s, but convert all others to failed Futures.
urls.map(url =>
Try(WS.url(url.url).get().map(x => x.statusText))
.recover{case e: IllegalArgumentException => Future.successful(url.url + " is illegal.")}
.recover{case t: Throwable => Future.failed(t)}
.get
)
Also note that the use of future{ .. } is deprecated.