Now that the dependency has been added, we can implement the BundleActivator interface.

We will name our activator BookInventoryMockImplActivator and place it in a different package (say com.packtpub.felix.bookshelf.inventory.impl.mock.activator) and declared as a private package to avoid it being exported along with the other classes of the bundle.

package com.packtpub.felix.bookshelf.inventory.impl.mock.activator;
import org.osgi.framework.BundleActivator;
import org.osgi.framework.BundleContext;
import org.osgi.framework.ServiceRegistration;
import com.packtpub.felix.bookshelf.inventory.api.BookInventory;
public class BookInventoryMonkImplActivator
implements BundleActivator
{

The bundle activator start() method is invoked at the start of the service and given a BundleContext reference. This context allows us to register and unregister services (among other operations).

We will keep the service registration reference to be used when unregistering the service.

private ServiceRegistration reg = null;
public void start(BundleContext context) throws Exception {
System.out.println(
"
Starting Book Inventory Mock Impl");
this.reg = context.registerService(
BookInventory.class.getName(),
new BookInventoryMockImpl(), null);
}

The registerService method is used to make a service available for look-up by other bundles on the framework. Its parameters are as follows:

The second parameter in the registerService method can also be a ServiceFactory object that the framework would use to create an instance of the service.

When the bundle is stopping, the activator stop() method is invoked. We can use the stored service reference to unget the service.

public void stop(BundleContext context) throws Exception {
System.out.println("
Stoping Book Inventory Mock Impl");
if (this.reg!=null) {
context.ungetService(reg.getReference());
this.reg = null;
}
}
}

Note that this is not strictly necessary, as all services from a bundle are unregistered by the framework when the bundle is stopped. However, it's good to know how this is done.