About Rajith Delantha

Rajith is an software engineer, open source contributor and love to develop application based on open source projects.

Sending Email with Java and Akka actors

Akka is a concurrent framework written by Scala.

Here I demonstrate sample application to send emails with Akka and implemented in Java.

Reasons I decided to use Akka framework other than concurrency.

  • Built-in configurable supervisor strategy to monitor child workers and decide what policy applies when there is an exception.
  • Can reschedule delivery when application throwing some specific exception.
  • Use of actor routers and allow them to use actor connection pool.

Here is how to create supervision strategy.

class EmailServiceActor extends UntypedActor {  
   private static SupervisorStrategy strategy =  
       new OneForOneStrategy(10, Duration.create("1 minute"),  
           new Function<Throwable, Directive>() {  
             @Override  
             public Directive apply(Throwable t) {  
               if (t instanceof MessagingException) {  
                 return resume();  
               } else if (t instanceof Exception) {  
                 return stop();  
               } else {  
                 return escalate();  
               }  
             }  
           });  
   @Override  
   public void onReceive(Object message) {  
     getContext().actorOf(new Props(EmailServiceWorker.class)).tell(message, self());  
   }  
   @Override  
   public SupervisorStrategy supervisorStrategy() {  
     return strategy;  
   }  
 }

Here is how child worker create

class EmailServiceWorker extends UntypedActor {  
   @Override  
   public void onReceive(Object message) {  
     try {  
       EmailService emailService = new EmailService();  
       emailService.sendEmail();  
     } catch (IOException e) {  
       e.printStackTrace(); //To change body of catch statement use File | Settings | File Templates.  
     } catch (MessagingException e) {  
       e.printStackTrace(); //To change body of catch statement use File | Settings | File Templates.  
     }  
   }  
   @Override  
   public void preStart() {  
 //    getContext().system().scheduler().scheduleOnce(Duration.create(5, TimeUnit.SECONDS), self(), "emailWorker", getContext().system().dispatcher(), null);  
   }  
   @Override  
   public void postStop() {  
   }  
 }

Sample application – https://github.com/rajithd/email-service-akka
 

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