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Implementing timer components is similar to implementing Java-based components. References, properties, and resources may be injected and used when the timer is fired. However, since timer components are not invoked by clients, they do not implement a service interface. Rather, they implement java.lang.Runnable. When the timer is fired, its run() method will be invoked. The following is an example of a timer implementation that uses a JPA EntityManager to retrieve a list of records and invoke a notification service:

@Component
@Timer(type = TimerType.FIXED_RATE, fixedRate=10000)
public class TimedComponent implements Runnable {

   @PersistenceContext(name="notifyEM")
   protected EntityManager entityManager;

   @Reference
   @Target("NotificationService") 	
   protected NotificationService service;

   public void run() {
      // use the entityManager to retrieve records ...
      List<Record> records = (List<Record>) entityManager.createQuery("").getResultList();
      // iterate through the records and fire notifications
      for (Recordsrecord :records) {
         service.notify;
      }
   }
}

Timer components are can also configured in XML using the implementation.timer element:

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Fixed rate fires a timer at the specified rate in milliseconds. A best effort will be made to maintain the rate over time. For example, the following timer will fire on average every 10 seconds:

In Java:
 
@Timer(type = TimerType.FIXED_RATE, fixedRate=10000)
 
Or in XML:
 
<f3:implementation.timer class="org.foo.timer.TimedComponent" fixedRate="10000"/>

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Repeat interval fires a timer according to the specified interval in milliseconds. For example, the following configures a timer to be triggered in intervals of 10 seconds:

In Java:

@Timer(type = TimerType.INTERVAL, repeatInterval=10000)

Or in XML:


<f3:implementation.timer class="org.foo.timer.TimedComponent" repeatInterval="10000"/>

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To create a create a dynamic firing timer, implement the nextInterval() method according to the following:

@Timer(type = TimerType.RECURRING)
public class TransactionalTimedIntervalComponent implements Runnable {

    public void run() {
    }

    public long nextInterval() {
        return 100;
    }
}

The above component can be configured in XML as follows:

<component name="TrxTimerIntervalComponent">
   <f3:implementation.timer poolName="TestPool" class="org.fabric3.tests.timer.TransactionalTimedIntervalComponent"/>
</component>

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Fire once triggers the timer once at the specified time in milliseconds. This method of configuring a timer is likely to have limited use. The following shows how to configure a timer to fire once:

In Java:
 
@Timer(type = TimerType.ONCE, fireOnce=10000)
 
In XML:
 
<f3:implementation.timer class="org.foo.timer.TimedComponent" fireOnce="...."/>

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