Question

Hey guys. We’re using OSGi services in an Eclipse RCP application. To track them, we’re using the org.osgi.util.tracker.ServiceTracker class. A sample code from the application looks like

mailServiceTracker = new ServiceTracker(context, MailService.class.getName(), null);
mailServiceTracker.open();
MailService service = (MailService) mailServiceTracker.getService();

Now my problem is that the getService() method frequently returns null when I created a new service. The code works very well for services that are existing for a long time in the application, but each time I create a new service, I have to do many things until the service is finally found and tracked. I regularly try for example

• ‘Clean…’ in Eclipse
• ‘Refresh’ all projects in Eclipse
• Rebuild the project on the command line

Sometimes those things help, and sometimes they don’t. Does anyone have experiences with those trackers and can tell me how to avoid this behavior and how to get the services tracked immediately upon creation?

Thanks

Answer 1

The problem is that the services you want may not have been created yet (especially in an bundle activator, as some bundles may not yet have started). If you still want to use the service tracker, you will need to provide a ServiceTrackerCustomizer, and keep track (sorry, no pun intended) of the services as they come and go.

Or, you could just switch over to Declarative Services that handle this for you.