Glassfish example source code file (ExtenderManager.java)

This example Glassfish source code file (ExtenderManager.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Java - Glassfish tags/keywords

eventlistener, exception, extender, extendermanager, extendermanager, extendertracker, extendertracker, glassfishservertracker, glassfishservertracker, habitat, log, logging, object, object, override, servicetracker

The Glassfish ExtenderManager.java source code

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 * and Distribution License("CDDL") (collectively, the "License").  You
 * may not use this file except in compliance with the License.  You can
 * obtain a copy of the License at
 * https://glassfish.dev.java.net/public/CDDL+GPL_1_1.html
 * or packager/legal/LICENSE.txt.  See the License for the specific
 * language governing permissions and limitations under the License.
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 * file and include the License file at packager/legal/LICENSE.txt.
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 * exception as provided by Oracle in the GPL Version 2 section of the License
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package org.glassfish.osgijavaeebase;

import org.glassfish.api.admin.ServerEnvironment;
import org.glassfish.api.event.EventListener;
import org.glassfish.api.event.EventTypes;
import org.glassfish.api.event.Events;
import org.osgi.framework.BundleContext;
import org.osgi.framework.InvalidSyntaxException;
import org.osgi.framework.ServiceReference;
import org.osgi.util.tracker.ServiceTracker;
import org.jvnet.hk2.component.Habitat;

import java.util.logging.Level;
import java.util.logging.Logger;

/**
 * It is responsible for starting any registered {@link Extender} service
 * after GlassFish server is started and stopping them when server is shutdown.
 * We use GlassFish STARTED event to be notified of server startup and shutdown.
 * Because the order in which bundles are started is undefined, we can't just assume existence
 * of Habitat to ask for the {@link }Events} service. Fortunately, HK2 OSGi bundle registers
 * Habitat in service registry. So we track that service and from there we listen to GF events.
 *
 * @author Sanjeeb.Sahoo@Sun.COM
 */
class ExtenderManager
{
    private static final Logger logger =
            Logger.getLogger(ExtenderManager.class.getPackage().getName());
    private BundleContext context;
    private Events events;
    private EventListener listener;
    private ServiceTracker extenderTracker;
    private GlassFishServerTracker glassFishServerTracker; // used to track starting of GlassFish

    public ExtenderManager(BundleContext context)
    {
        this.context = context;
    }

    public synchronized void start() throws Exception
    {
        logger.logp(Level.FINE, "ExtenderManager", "start", "ExtenderManager starting");
        glassFishServerTracker = new GlassFishServerTracker(context);
        glassFishServerTracker.open();
    }

    public synchronized void stop() throws Exception
    {
        logger.logp(Level.FINE, "ExtenderManager", "start", "ExtenderManager stopping");
        unregisterGlassFishShutdownHook();
        if (glassFishServerTracker != null) {
            glassFishServerTracker.close();
            glassFishServerTracker = null;
        }
        stopExtenders();
    }

    private synchronized void startExtenders() {
        logger.entering("ExtenderManager", "startExtenders");

        // Because of a race condition, we can be started multiple times, so check if already started
        if (extenderTracker != null) return;

        // open will call addingService for each existing extender
        // and there by we will start each extender.
        extenderTracker = new ExtenderTracker(context);
        extenderTracker.open();
    }

    private synchronized void stopExtenders()
    {
        logger.entering("ExtenderManager", "stopExtenders");

        // Because of a race condition, we can be stopped multiple times, so check if already started
        // more over, extenderTracker will be null until server is started, so to avoid NPE, null check is needed.
        if (extenderTracker == null) return;

        // close will call removedService for each tracked extender
        // and there by we will stop each extender.
        extenderTracker.close();
        extenderTracker = null;
    }

    private void unregisterGlassFishShutdownHook() {
        if (listener != null) {
            events.unregister(listener);
        }
    }

    private class ExtenderTracker extends ServiceTracker {
        ExtenderTracker(BundleContext context)
        {
            super(context, Extender.class.getName(), null);
        }

        @Override
        public Object addingService(ServiceReference reference)
        {
            Extender e = Extender.class.cast(context.getService(reference));
            logger.logp(Level.FINE, "ExtenderManager$ExtenderTracker", "addingService", "Starting extender called {0}", new Object[]{e});
            e.start();
            return e;
        }

        @Override
        public void removedService(ServiceReference reference, Object service) {
            Extender e = Extender.class.cast(context.getService(reference));
            logger.logp(Level.FINE, "ExtenderManager$ExtenderTracker", "removedService", "Stopping extender called {0}", new Object[]{e});
            e.stop();
        }
    }

    /**
     * Tracks Habitat and obtains EVents service from it and registers a listener
     * that takes care of actually starting and stopping other extenders.
     */
    private class GlassFishServerTracker extends ServiceTracker {
        public GlassFishServerTracker(BundleContext context)
        {
            super(context, Habitat.class.getName(), null);
        }

        @Override
        public Object addingService(ServiceReference reference)
        {
            try {
                logger.logp(Level.FINE, "ExtenderManager$GlassFishServerTracker", "addingService", "Habitat has been created");
                ServiceReference habitatServiceRef = context.getServiceReference(Habitat.class.getName());
                Habitat habitat = Habitat.class.cast(context.getService(habitatServiceRef));
                events = habitat.getComponent(Events.class);
                listener = new EventListener() {
                    public void event(Event event)
                    {
                        if (EventTypes.SERVER_READY.equals(event.type())) {
                            startExtenders();
                        } else if (EventTypes.PREPARE_SHUTDOWN.equals(event.type())) {
                            stopExtenders();
                        }
                    }
                };
                events.register(listener);
                // We can get into infinite waiting loop if server is already started. So check the status once.
                if (habitat.getComponent(ServerEnvironment.class).getStatus() == ServerEnvironment.Status.started) {
                    startExtenders();
                }
                return super.addingService(reference);
            } finally {
                close(); // no need to track any more
            }
        }
    }
}