core/src/main/java/org/jclouds/osgi/Activator.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.jclouds.osgi;

import org.osgi.framework.BundleActivator;
import org.osgi.framework.BundleContext;
import org.osgi.framework.ServiceReference;
import org.osgi.util.tracker.ServiceTracker;

public class Activator implements BundleActivator {

   private ServiceTracker providerListenerTracker = null;
   private ServiceTracker apiListenerTracker = null;
   private MetadataBundleListener bundleListener = new MetadataBundleListener();

   /**
    * Called when this bundle is started so the Framework can perform the bundle-specific activities necessary to start
    * this bundle. This method can be used to register services or to allocate any resources that this bundle needs.
    * <p/>
    * <p/>
    * This method must complete and return to its caller in a timely manner.
    * 
    * @param context
    *           The execution context of the bundle being started.
    * @throws Exception
    *            If this method throws an exception, this bundle is marked as stopped and the Framework will remove this
    *            bundle's listeners, unregister all services registered by this bundle, and release all services used by
    *            this bundle.
    */
   @Override
   public void start(BundleContext context) throws Exception {
      bundleListener.start(context);
      providerListenerTracker = new ServiceTracker(context, ProviderListener.class.getName(), null) {
         @Override
         public Object addingService(ServiceReference reference) {
            Object obj = super.addingService(reference);
            if (ProviderListener.class.isAssignableFrom(obj.getClass())) {
               bundleListener.addProviderListener((ProviderListener) obj);
            }
            return obj;
         }

         @Override
         public void removedService(ServiceReference reference, Object service) {
            if (ProviderListener.class.isAssignableFrom(service.getClass())) {
               bundleListener.removeProviderListener((ProviderListener) service);
            }
            super.removedService(reference, service);
         }
      };

      apiListenerTracker = new ServiceTracker(context, ApiListener.class.getName(), null) {
         @Override
         public Object addingService(ServiceReference reference) {
            Object obj = super.addingService(reference);
            if (ApiListener.class.isAssignableFrom(obj.getClass())) {
               bundleListener.addApiListenerListener((ApiListener) obj);
            }
            return obj;
         }

         @Override
         public void removedService(ServiceReference reference, Object service) {
            if (ApiListener.class.isAssignableFrom(service.getClass())) {
               bundleListener.removeApiListenerListener((ApiListener) service);
            }
            super.removedService(reference, service);
         }
      };

      providerListenerTracker.open();
      apiListenerTracker.open();
   }

   /**
    * Called when this bundle is stopped so the Framework can perform the bundle-specific activities necessary to stop
    * the bundle. In general, this method should undo the work that the <code>BundleActivator.start</code> method
    * started. There should be no active threads that were started by this bundle when this bundle returns. A stopped
    * bundle must not call any Framework objects.
    * <p/>
    * <p/>
    * This method must complete and return to its caller in a timely manner.
    * 
    * @param context
    *           The execution context of the bundle being stopped.
    * @throws Exception
    *            If this method throws an exception, the bundle is still marked as stopped, and the Framework will
    *            remove the bundle's listeners, unregister all services registered by the bundle, and release all
    *            services used by the bundle.
    */
   @Override
   public void stop(BundleContext context) throws Exception {
      bundleListener.stop(context);
      ProviderRegistry.clear();
      ApiRegistry.clear();
      if (apiListenerTracker != null) {
         apiListenerTracker.close();
      }
      if (providerListenerTracker != null) {
         providerListenerTracker.close();
      }
   }
}