onComplete

def onComplete[T](future: 

Description

Evaluates its parameter of type Future[T]CompletionStage<T>, and once it has been completed, extracts its result as a value of type Try[T]Try<T> and passes it to the inner route. A Try<T> can either be a Success containing the T value or a Failure containing the Throwable.

To handle the Failure case automatically and only work with the result value, use onSuccess.

To complete with a successful result automatically and just handle the failure result, use completeOrRecoverWith, instead.

Example

Scala

copysourcedef divide(a: Int, b: Int): Future[Int] = Future {
  a / b
}

val route =
  path("divide" / IntNumber / IntNumber) { (a, b) =>
    onComplete(divide(a, b)) {
      case Success(value) => complete(s"The result was $value")
      case Failure(ex)    => complete(InternalServerError, s"An error occurred: ${ex.getMessage}")
    }
  }

// tests:
Get("/divide/10/2") ~> route ~> check {
  responseAs[String] shouldEqual "The result was 5"
}

Get("/divide/10/0") ~> Route.seal(route) ~> check {
  status shouldEqual InternalServerError
  responseAs[String] shouldEqual "An error occurred: / by zero"
}

Java

copysourceimport static org.apache.pekko.http.javadsl.server.Directives.complete;
import static org.apache.pekko.http.javadsl.server.Directives.onComplete;
import static org.apache.pekko.http.javadsl.server.Directives.path;

// import static org.apache.pekko.http.javadsl.server.PathMatchers.*;

final Route route =
    path(
        segment("divide").slash(integerSegment()).slash(integerSegment()),
        (a, b) ->
            onComplete(
                () -> CompletableFuture.supplyAsync(() -> a / b),
                maybeResult ->
                    maybeResult
                        .map(result -> complete("The result was " + result))
                        .recover(
                            new PFBuilder<Throwable, Route>()
                                .matchAny(
                                    ex ->
                                        complete(
                                            StatusCodes.InternalServerError(),
                                            "An error occurred: " + ex.getMessage()))
                                .build())
                        .get()));

testRoute(route).run(HttpRequest.GET("/divide/10/2")).assertEntity("The result was 5");

testRoute(route)
    .run(HttpRequest.GET("/divide/10/0"))
    .assertStatusCode(StatusCodes.InternalServerError())
    .assertEntity("An error occurred: / by zero");