OSGiFrameworkLauncher.java

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package com.sun.enterprise.glassfish.bootstrap.osgi;

import org.osgi.framework.BundleContext;
import org.osgi.framework.BundleException;
import org.osgi.framework.BundleReference;
import org.osgi.framework.launch.Framework;
import org.osgi.framework.launch.FrameworkFactory;
import org.osgi.util.tracker.ServiceTracker;

import java.util.Properties;
import java.util.ServiceLoader;

/**
 * Utility class which takes care of launching OSGi framework.
 * It lauches the framework in a daemon thread, because typically framework spawned threads inherit
 * parent thread's daemon status.
 *
 * It also provides a utility method to get hold of OSGi services registered in the system.
 *
 * @author Sanjeeb.Sahoo@Sun.COM
 */
public class OSGiFrameworkLauncher {

    private Properties properties;
    private Framework framework;

    public OSGiFrameworkLauncher(Properties properties) {
        this.properties = properties;
    }

    public Framework launchOSGiFrameWork() throws Exception {
        if (!isOSGiEnv()) {
            // Locate an OSGi framework and initialize it
            ServiceLoader<FrameworkFactory> frameworkFactories =
                    ServiceLoader.load(FrameworkFactory.class, getClass().getClassLoader());
            for (FrameworkFactory ff : frameworkFactories) {
                framework = ff.newFramework(properties);
                break;
            }
            if (framework == null) {
                throw new RuntimeException("No OSGi framework in classpath");
            }
            // init framework in a daemon thread so that the framework spwaned internal threads will be daemons
            Thread t = new Thread() {
                @Override
                public void run() {
                    try {
                        framework.init();
                    } catch (BundleException e) {
                        throw new RuntimeException(e);
                    }
                }
            };
            t.setDaemon(true);
            t.start();
            t.join();
        } else {
            throw new IllegalStateException("An OSGi framework is already running...");
        }
        return framework;
    }

    public <T> T getService(Class<T> type) throws Exception {
        if (framework == null) {
            throw new IllegalStateException("OSGi framework has not yet been launched.");
        }
        final BundleContext context = framework.getBundleContext();
        ServiceTracker tracker = new ServiceTracker(context, type.getName(), null);
        try {
            tracker.open(true);
            return type.cast(tracker.waitForService(0));
        } finally {
            tracker.close(); // no need to track further
        }
    }


    /**
     * Determine if we we are operating in OSGi env. We do this by checking what class loader is used to
     * this class.
     *
     * @return false if we are already called in the context of OSGi framework, else true.
     */
    private boolean isOSGiEnv() {
        return (getClass().getClassLoader() instanceof BundleReference);
    }


}