Render scala template outside of controller? (Play 2)

Question

I'm trying to decouple the sending of notification emails from the events that cause them. So far I'm passing a mail object (DocumentIssuedMail) from a controller to an Akka actor(EmailDispatcher), which is then sending the mail via the play-easymail wrapper of the Play mailer plugin. The email body is generated by the mail object after being passed to the actor, and the HTML is generated from a Scala template.

This template contains link with absolute URLs, obtained by calling

@routes.SomeController.someAction().absoluteURL()

However, I'm getting a RuntimeException when trying to render the template.

The stack trace is as follows:

java.lang.RuntimeException: There is no HTTP Context available from here.
    at play.mvc.Http$Context.current(Http.java:30)
    at play.mvc.Http$Context$Implicit.ctx(Http.java:196)
    at play.core.j.PlayMagicForJava$.requestHeader(TemplateMagicForJava.scala:56)
    at views.html.email._learner_main$.apply(_learner_main.template.scala:41)
    at views.html.documents.email.new_doc_unregistered$.apply(new_doc_unregistered.template.scala:47)
    at views.html.documents.email.new_doc_unregistered$.render(new_doc_unregistered.template.scala:67)
    at views.html.documents.email.new_doc_unregistered.render(new_doc_unregistered.template.scala)
    at email.DocumentIssuedMail.getUnregisteredMail(DocumentIssuedMail.java:71)
    at email.DocumentIssuedMail.getMail(DocumentIssuedMail.java:67)
    at actors.email.EmailDispatcher.onReceive(EmailDispatcher.java:32)
    at akka.actor.UntypedActor$$anonfun$receive$1.applyOrElse(UntypedActor.scala:167)
    at akka.actor.ActorCell.receiveMessage(ActorCell.scala:498)
    at akka.actor.ActorCell.invoke(ActorCell.scala:456)
    at akka.dispatch.Mailbox.processMailbox(Mailbox.scala:237)
    at akka.dispatch.Mailbox.run(Mailbox.scala:219)
    at akka.dispatch.ForkJoinExecutorConfigurator$AkkaForkJoinTask.exec(AbstractDispatcher.scala:386)
    at scala.concurrent.forkjoin.ForkJoinTask.doExec(ForkJoinTask.java:260)
    at scala.concurrent.forkjoin.ForkJoinPool$WorkQueue.runTask(ForkJoinPool.java:1339)
    at scala.concurrent.forkjoin.ForkJoinPool.runWorker(ForkJoinPool.java:1979)
    at scala.concurrent.forkjoin.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:107)

Is it possible to render the template in that location, or do I need to do it on the original thread?

Answer 1

One possible solution for this problem is to pass a http request explicitly to your actor and then to a mail template.

In a template you pass this request to a absoluteURL() method:

@(requestHeader: play.api.mvc.RequestHeader)

@main("") {
    @routes.Application.someAction().absoluteURL()(requestHeader)
}

Along with DocumentIssuedMail you need to pass a request to an actor. Here is a simple DTO.

import play.api.mvc.RequestHeader;

public class DocumentIssuedMailWrapper {
    private DocumentIssuedMail documentIssuedMail;
    private RequestHeader requestHeader;

    public DocumentIssuedMailWrapper(DocumentIssuedMail documentIssuedMail, RequestHeader requestHeader) {
        this.documentIssuedMail = documentIssuedMail;
        this.requestHeader = requestHeader;
    }

    public DocumentIssuedMail getDocumentIssuedMail() {
        return documentIssuedMail;
    }

    public RequestHeader getRequestHeader() {
        return requestHeader;
    }
}

The actor passes a request from the DTO to the mail template as an ordinary parameter.

import akka.actor.UntypedActor;
import play.api.templates.Html;
import views.html.mail;

public class EmailDispatcher extends UntypedActor {

    @Override
    public void onReceive(Object message) throws Exception {
        if (message instanceof DocumentIssuedMailWrapper) {
            DocumentIssuedMailWrapper wrapper = (DocumentIssuedMailWrapper) message;
            Html mailTemplate = mail.render(wrapper.getRequestHeader());
            //sending mail
        }
    }

}

In a controller you are able to get a request by calling ctx()._requestHeader() method. Now you just need to schedule a job with the actor and pass the request with the DTO.

import akka.actor.ActorRef;
import akka.actor.Props;
import play.libs.Akka;
import play.mvc.*;

import scala.concurrent.duration.Duration;

import java.util.concurrent.TimeUnit;

public class Application extends Controller {

    public static Result sendMail() {
        DocumentIssuedMailWrapper wrapper = new DocumentIssuedMailWrapper(new DocumentIssuedMail(), ctx()._requestHeader());

        ActorRef emailDispatcher = Akka.system().actorOf(Props.create(EmailDispatcher.class));
        Akka.system().scheduler().scheduleOnce(Duration.create(0, TimeUnit.MILLISECONDS), emailDispatcher, wrapper, Akka.system().dispatcher(), null);
        return ok("Mail sent");
    }

    public static Result someAction() {
        return ok("Some other action");
    }

}