ecommons/org.eclipse.statet.ecommons.net.core/src/org/eclipse/statet/ecommons/net/resourcemapping/core/ResourceMappingUtils.java

/*=============================================================================#
 # Copyright (c) 2011, 2020 Stephan Wahlbrink and others.
 # 
 # This program and the accompanying materials are made available under the
 # terms of the Eclipse Public License 2.0 which is available at
 # https://www.eclipse.org/legal/epl-2.0, or the Apache License, Version 2.0
 # which is available at https://www.apache.org/licenses/LICENSE-2.0.
 # 
 # SPDX-License-Identifier: EPL-2.0 OR Apache-2.0
 # 
 # Contributors:
 #     Stephan Wahlbrink <sw@wahlbrink.eu> - initial API and implementation
 #=============================================================================*/

package org.eclipse.statet.ecommons.net.resourcemapping.core;

import org.osgi.framework.Bundle;
import org.osgi.framework.BundleContext;
import org.osgi.framework.BundleEvent;
import org.osgi.framework.BundleListener;
import org.osgi.util.tracker.ServiceTracker;

import org.eclipse.core.runtime.Platform;


public class ResourceMappingUtils {
	
	
	private static final String BUNDLE_ID= "org.eclipse.statet.ecommons.net.core"; //$NON-NLS-1$
	
	private static class ManagerBundleListener implements BundleListener {
		
		private final long bundleId;
		
		public ManagerBundleListener(final Bundle bundle) {
			this.bundleId= bundle.getBundleId();
		}
		
		@Override
		public void bundleChanged(final BundleEvent event) {
			if (event.getBundle().getBundleId() == this.bundleId
					&& event.getType() == BundleEvent.STOPPED) {
				final BundleContext context= event.getBundle().getBundleContext();
				if (context != null) {
					context.removeBundleListener(this);
				}
				synchronized (managerLock) {
					if (managerTracker != null) {
						managerTracker.close();
						managerTracker= null;
					}
				}
			}
		}
	}
	
	private static final Object managerLock= new Object();
	
	private static ServiceTracker<IResourceMappingManager, ?> managerTracker;
	
	
	/**
	 * Returns the resource mapping manager service, if available
	 * 
	 * @return the manager if available, otherwise <code>null</code>
	 */
	public static IResourceMappingManager getManager() {
		synchronized (managerLock) {
			if (managerTracker == null) {
				final Bundle bundle= Platform.getBundle(BUNDLE_ID);
				if (bundle.getState() != Bundle.ACTIVE) {
					return null;
				}
				final BundleContext context= bundle.getBundleContext();
				context.addBundleListener(new ManagerBundleListener(bundle));
				managerTracker= new ServiceTracker<>(context,
						IResourceMappingManager.class.getName(), null );
				managerTracker.open();
			}
			return (IResourceMappingManager) managerTracker.getService();
		}
	}
	
	
	private ResourceMappingUtils() {
	}
	
}