CommandRegistry.java

/*******************************************************************************
 * Copyright (c) 2008, 2010 VMware Inc.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *   VMware Inc. - initial contribution
 *******************************************************************************/

package org.eclipse.virgo.shell.internal;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

import org.osgi.framework.BundleContext;
import org.osgi.framework.InvalidSyntaxException;
import org.osgi.framework.ServiceEvent;
import org.osgi.framework.ServiceListener;
import org.osgi.framework.ServiceReference;

/**
 * A <code>CommandRegistry</code> maintains a list of {@link CommandDescriptor CommandDescriptors} based on the contents
 * of the OSGi service registry. Descriptors are created using a {@link CommandResolver}.
 * <p />
 * 
 * <strong>Concurrent Semantics</strong><br />
 * 
 * Thread-safe.
 * 
 */
public final class CommandRegistry {

    private final CommandResolver commandResolver;

    private final BundleContext bundleContext;

    private final List<CommandDescriptor> commandDescriptors = new ArrayList<CommandDescriptor>();

    private final Map<ServiceReference<?>, List<CommandDescriptor>> commandDescriptorsByService = new HashMap<ServiceReference<?>, List<CommandDescriptor>>();

    private final Object monitor = new Object();

    private final CommandRegistryServiceListener commandRegistryServiceListener = new CommandRegistryServiceListener();

    /**
     * @param commandResolver
     * @param bundleContext 
     */
    public CommandRegistry(CommandResolver commandResolver, BundleContext bundleContext) {
        this.commandResolver = commandResolver;
        this.bundleContext = bundleContext;
    }

    void initialize() {
        // TODO Limit with a filter
        this.bundleContext.addServiceListener(this.commandRegistryServiceListener);
        try {
            // TODO Limit with a filter
            ServiceReference<?>[] serviceReferences = this.bundleContext.getServiceReferences((String)null, null);
            if (serviceReferences != null) {
                for (ServiceReference<?> serviceReference : serviceReferences) {
                    serviceRegistered(serviceReference);
                }
            }
        } catch (InvalidSyntaxException e) {
            throw new RuntimeException("Unexpected InvalidSyntaxException", e);
        }
    }
    
    public List<CommandDescriptor> getCommandDescriptors() {
        synchronized(this.monitor) { 
            return new ArrayList<CommandDescriptor>(this.commandDescriptors);
        }
    }
    

    private void serviceRegistered(ServiceReference<?> serviceReference) {
        Object service = bundleContext.getService(serviceReference);
        if (service != null) {
            List<CommandDescriptor> commands = commandResolver.resolveCommands(serviceReference, service);
            if (!commands.isEmpty()) {
                synchronized (this.monitor) {
                    this.commandDescriptors.addAll(commands);
                    this.commandDescriptorsByService.put(serviceReference, commands);
                }
            }
        }
    }

    private void serviceUnregistering(ServiceReference<?> serviceReference) {
        synchronized (this.monitor) {
            List<CommandDescriptor> commandDescriptorsForService = this.commandDescriptorsByService.remove(serviceReference);
            if (commandDescriptorsForService != null) {
                this.commandDescriptors.removeAll(commandDescriptorsForService);
            }
        }
    }

    private final class CommandRegistryServiceListener implements ServiceListener {

        /**
         * {@inheritDoc}
         */
        public void serviceChanged(ServiceEvent event) {
            if (ServiceEvent.REGISTERED == event.getType()) {
                serviceRegistered(event.getServiceReference());
            } else if (ServiceEvent.UNREGISTERING == event.getType()) {
                serviceUnregistering(event.getServiceReference());
            }
        }
    }
}