failWith explicitly raises an exception that gets bubbled up through the route structure to be picked up by the nearest
handleExceptions directive. Using
failWith rather than simply throwing an exception enables the route structure’s Exception Handling mechanism to deal with the exception even if the current route is executed asynchronously on another thread (e.g. in a
Future or separate actor).
handleExceptions is present above the respective location in the route structure the top-level routing logic will handle the exception and translate it into a corresponding HttpResponseHttpResponse using the in-scope ExceptionHandlerExceptionHandler chapter).
There is one notable special case: If the given exception is a RejectionErrorRejectionError exception it is not bubbled up, but rather the wrapped exception is unpacked and “executed”. This allows the “tunneling” of a rejection via an exception.
import static akka.http.javadsl.server.Directives.failWith; import static akka.http.javadsl.server.Directives.path; final Route route = path("foo", () -> failWith(new RuntimeException("Oops.")) ); // tests: testRoute(route).run(HttpRequest.GET("/foo")) .assertStatusCode(StatusCodes.INTERNAL_SERVER_ERROR) .assertEntity("There was an internal server error.");