Introducing Java EE 7 – EJBs - Java EE 7 Development with WildFly - page 107

Using the EJB timer service
Applications that model business workflows often rely on timed notifications. The timer
service of the enterprise bean container enables you to schedule timed notifications for all
types of enterprise beans, except for stateful session beans. You can schedule a timed noti-
fication to occur according to a calendar schedule either at a specific time, after the dura-
tion of a time period, or at timed intervals.
There can be two main types of EJB timers: programmatic timers and automatic timers.
Programmatic timers are set by explicitly calling one of the timer creation methods of the
TimerService interface. Automatic timers are created upon the successful deployment
of an enterprise bean, which contains a method annotated with the
java.ejb.Schedule or java.ejb.Schedules annotations. Let's see both ap-
proaches in the following sections.
Programmatic timer creation
To create a timer, the bean invokes one of the create methods of the TimerService
interface. These methods allow for either single-action, interval, or calendar-based timers
to be created.
The simplest way to get a TimerService instance is to use resource injection. For ex-
ample, in the TheatreBox singleton EJB, we will use the @Resource annotation to in-
ject a TimerService object, as shown in the following code snippet:
@Resource
TimerService timerService;
private static final long DURATION =
TimeUnit.SECONDS.toMillis(6);
The duration specifies the time (in milliseconds) when the single timer is fired. The method
that will fire the timer will use the TimerService instance to invoke cre-
ateSingleActionTimer , passing the duration and an instance of the TimerConfig
class as an argument, which may optionally contain some basic information (such as the
description of the timer). This is shown in the following code snippet:
public void createTimer(){
timerService.createSingleActionTimer(DURATION, new