Seam makes it very easy to perform work asynchronously from a web request. When most people think of asynchronicity in Java EE, they think of using JMS. This is certainly one way to approach the problem in Seam, and is the right way when you have strict and well-defined quality of service requirements. Seam makes it easy to send and receive JMS messages using Seam components.

But for many use cases, JMS is overkill. Seam layers a simple asynchronous method and event facility over your choice of dispatchers:

<async:timer-service-dispatcher/>

<async:quartz-dispatcher/>

@Local

public interface PaymentHandler

{

    @Asynchronous

    public void processPayment(Payment payment);

}

@Stateless

@Name("paymentHandler")

public class PaymentHandlerBean implements PaymentHandler

{

    public void processPayment(Payment payment)

    {

        //do some work!

    }

}

@Stateful

@Name("paymentAction")

public class CreatePaymentAction

{

    @In(create=true) PaymentHandler paymentHandler;

    @In Bill bill;

    

    public String pay()

    {

        paymentHandler.processPayment( new Payment(bill) );

        return "success";

    }

}

@Local

public interface PaymentHandler

{

    @Asynchronous

    public void processScheduledPayment(Payment payment, @Expiration Date date);


    @Asynchronous

    public void processRecurringPayment(Payment payment, 

                                        @Expiration Date date, 

                                        @IntervalDuration Long interval)'

}

@Stateful

@Name("paymentAction")

public class CreatePaymentAction

{

    @In(create=true) PaymentHandler paymentHandler;

    @In Bill bill;

    

    public String schedulePayment()

    {

        paymentHandler.processScheduledPayment( new Payment(bill), bill.getDueDate() );

        return "success";

    }


    public String scheduleRecurringPayment()

    {

        paymentHandler.processRecurringPayment( new Payment(bill), bill.getDueDate(), 

                                                ONE_MONTH );

        return "success";

    }

}

@Local

public interface PaymentHandler

{

    @Asynchronous

    public Timer processScheduledPayment(Payment payment, @Expiration Date date);

}

@Stateless

@Name("paymentHandler")

public class PaymentHandlerBean implements PaymentHandler

{

    @In Timer timer;

    

    public Timer processScheduledPayment(Payment payment, @Expiration Date date)

    {

        //do some work!

        

        return timer; //note that return value is completely ignored

    }


}

@Stateful

@Name("paymentAction")

public class CreatePaymentAction

{

    @In(create=true) PaymentHandler paymentHandler;

    @In Bill bill;

    

    public String schedulePayment()

    {

        Timer timer = paymentHandler.processScheduledPayment( new Payment(bill), 

                                                              bill.getDueDate() );

        return "success";

    }

}

        @In QuartzTriggerHandle timer;

        

    // Defines the method in the "processor" component

    @Asynchronous

    public QuartzTriggerHandle schedulePayment(@Expiration Date when, 

                                 @IntervalDuration Long interval,

                                 @FinalExpiration Date endDate, 

                                 Payment payment) 

    { 

        // do the repeating or long running task until endDate

    }

    

    ... ...

    

    // Schedule the task in the business logic processing code

    // Starts now, repeats every hour, and ends on May 10th, 2010

    Calendar cal = Calendar.getInstance ();

    cal.set (2010, Calendar.MAY, 10);

    processor.schedulePayment(new Date(), 60*60*1000, cal.getTime(), payment);

QuartzTriggerHandle handle =

         processor.schedulePayment(payment.getPaymentDate(), 

                                   payment.getPaymentCron(), 

                                   payment);

        payment.setQuartzTriggerHandle( handle );

        // Save payment to DB

        

        // later ...

        

        // Retrieve payment from DB

        // Cancel the remaining scheduled tasks

        payment.getQuartzTriggerHandle().cancel();

    // Define the method

    @Asynchronous

    public QuartzTriggerHandle schedulePayment(@Expiration Date when, 

                                 @IntervalCron String cron, 

                                 Payment payment) 

    { 

        // do the repeating or long running task

    }

    

    ... ...

    

    // Schedule the task in the business logic processing code

    QuartzTriggerHandle handle = 

      processor.schedulePayment(new Date(), "0 10,44 14 ? 3 WED", payment);

    // Define the method

    @Asynchronous

    public QuartzTriggerHandle schedulePayment(@Expiration Date when, 

                                 @IntervalBusinessDay NthBusinessDay nth, 

                                 Payment payment) 

    { 

        // do the repeating or long running task

    }

    

    ... ...

    

    // Schedule the task in the business logic processing code

    QuartzTriggerHandle handle = 

      processor.schedulePayment(new Date(), 

          new NthBusinessDay(2, "14:00", WEEKLY), payment);

public class NthBusinessDay implements Serializable

{

      int n;

      String fireAtTime;

      List <Date

> additionalHolidays;

      BusinessDayIntervalType interval;

      boolean excludeWeekends;

      boolean excludeUsFederalHolidays;


      public enum BusinessDayIntervalType { WEEKLY, MONTHLY, YEARLY }


      public NthBusinessDay ()

      {

        n = 1;

        fireAtTime = "12:00";

        additionalHolidays = new ArrayList <Date

> ();

        interval = BusinessDayIntervalType.WEEKLY;

        excludeWeekends = true;

        excludeUsFederalHolidays = true;

      }     

      ... ...

}

@Scope(ScopeType.STATELESS)

@Name("org.jboss.seam.async.asynchronousExceptionHandler")

public class MyAsynchronousExceptionHandler extends AsynchronousExceptionHandler { 


   @Logger Log log;

   

   @In Future timer;

   

   @Override

   public void handleException(Exception exception) {

      log.debug(exception);

      timer.cancel(false);

   }

   

}

   public void handleAsynchronousException(Exception exception) {

      log.fatal(exception);

   }

<jms:managed-topic-publisher name="stockTickerPublisher" 

                             auto-create="true" 

                             topic-jndi-name="topic/stockTickerTopic"/>



<jms:managed-queue-sender name="paymentQueueSender" 

                          auto-create="true" 

                          queue-jndi-name="queue/paymentQueue"/>

@In 

private TopicPublisher stockTickerPublisher;   

@In 

private TopicSession topicSession;


public void publish(StockPrice price) {

      try

      {

         stockTickerPublisher.publish( topicSession.createObjectMessage(price) );

      } 

      catch (Exception ex)

      {

         throw new RuntimeException(ex);

      } 

}

@In

private QueueSender paymentQueueSender;   

@In

private QueueSession queueSession;


public void publish(Payment payment) {

      try

      {

         paymentQueueSender.send( queueSession.createObjectMessage(payment) );

      } 

      catch (Exception ex)

      {

         throw new RuntimeException(ex);

      } 

}