Handling exceptions in Play 2 Java asynchronous controllers. Thinking about ways of specifying Result types from within async blocks.

AsyncApplication.java

package controllers;

import play.libs.Akka;
import play.libs.F;
import play.mvc.Controller;
import play.mvc.Result;

import java.util.concurrent.Callable;

public class AsyncApplication extends Controller {

    public static Result synchronousCall() {
        String foo = intensiveOperationA();
        String bar = intensiveOperationB();
        return ok("Got result: " + foo + " " + bar);
    }

    public static Result asynchronousCall_asPerPlayDocs() {
        F.Promise<String> promise = Akka.future(new Callable<String>() {
            @Override
            public String call() throws Exception {
                String foo = intensiveOperationA();
                String bar = intensiveOperationB();
                return foo + " " + bar;
            }
        });
        return async(promise.map(new F.Function<String, Result>() {
            @Override
            public Result apply(String s) throws Throwable {
                // what if we want something other than 200?
                return ok("Got result: " + s);
            }
        }));
    }

    public static Result asynchronousCall_possibleAlternative() {
        F.Promise<Result> promise = Akka.future(new Callable<Result>() {
            @Override
            public Result call() throws Exception {
                Result result;
                String foo = intensiveOperationA();
                if (foo.equals("hurdy")) {
                    result = badRequest("Something went wrong");
                } else {
                    String bar = intensiveOperationB();
                    result = ok("Got result: " + foo + " " + bar);
                }

                return result;
            }
        });
        return async(promise);
    }

    private static String intensiveOperationA() {
        return "foo";
    }

    private static String intensiveOperationB() {
        return "bar";
    }
}