How can I use the J2EE Timer Service API in the Servlet startup code?

Question

For a background job which I would like to run in a J2EE container, I found the suggestion to create a startup servlet and use the Timer Service API to create a managed Timer (in the answers for What tools are there for timed batch processes in J2EE?).

To create a timer, I need a context which implements the timer API. (Example)

In the Servlet class, I override the init method, but it has only access to a ServletContext, but not to a SessionContext. A ServletContext does not have methods to create timers, so I am stuck here.

How can I access the J2EE timer service in the startup code of a servlet?

Answer 1

Whenever I hear timer job, I can't help but think that this should be separated from a Java EE app server. You can use something like Quartz, or an operating system scheduled task, or a batch manager like AutoSys, but embedding it into a servlet seems like a misuse of servlets to me.

Java EE 5 containers have a TimerService that's an EJB. Perhaps this will help you sort it out.

Answer 2

Instead of using the Servlet startup code (which will be executed after every redeployment) I found it cleaner to start timers in the startup of the EJB. With EJB 3.1 and Singleton EJB this now is possible with much less code:

http://blogs.oracle.com/kensaks/entry/application_startup_shutdown_callbacks