public class Activator implements BundleActivator {

	private ServiceTracker<IStateServiceClient, IStateServiceClient> stateServiceTracker;

	private static Activator instance;

	/**
	 * Returns the shared instance
	 * 
	 * @return the shared instance
	 */
	public static Activator getInstance() {
		return instance;
	}

	@Override
	public void start(BundleContext context) throws Exception {
		instance = this;

		stateServiceTracker = new ServiceTracker<IStateServiceClient, IStateServiceClient>(context,
						IStateServiceClient.class.getName(), null);
		stateServiceTracker.open();
	}

	@Override
	public void stop(BundleContext context) throws Exception {
		stateServiceTracker.close();

		instance = null;
	}

	public IStateServiceClient getStateService() {
		return stateServiceTracker.getService();
	}

}

Bundle-Activator: my.package.Activator

Activator.getInstance().getStateService();

BundleContext ctxt = (BundleContext)
servletContext.getAttribute("osgi-bundlecontext");