adam bien's blog

Simplest Possible EJB 3.1 Timer 📎


@Singleton
public class TimerService {
    @EJB
    HelloService helloService;
  
    @Schedule(second="*/1", minute="*",hour="*", persistent=false)
    public void doWork(){
        System.out.println("timer: " + helloService.sayHello());
    }
}

A timer doesn't have to be a singleton - it can be a @Stateless and even a @Stateful bean. The method doWork() will be invoked every second. There is no registration or configuration needed.

How to compile:

You will need the EJB 3.1 API in the classpath, or at least the @Singleton, @Schedule and @EJB annotation.

How to deploy:

Just JAR or WAR the interceptor with an EJB and put the archive into e.g: [glassfishv3]\glassfish\domains\domain1\autodeploy

Btw. the initial deployment of the entire WAR took on my machine:


INFO: Loading application SimpleTimer at /SimpleTimer
INFO: SimpleTimer was successfully deployed in 363 milliseconds.

How to use:

Another service can be easily injected to the timer and so invoked periodically:


@Stateless
public class HelloService {
    public String sayHello(){
        return "Hello from control: " + System.currentTimeMillis();
    }
}

And: there is no XML, strange configuration, libraries, additional dependencies needed...You will find the whole executable project (tested with Netbeans 6.8 and Glassfish v3) in: http://kenai.com/projects/javaee-patterns/ [project name: SimpleTimer].