src/main/java/org/apache/felix/scr/impl/BundleComponentActivator.java - felix-dev - Git at Google

 /*
  * 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.apache.felix.scr.impl;


 import java.io.BufferedReader;
 import java.io.IOException;
 import java.io.InputStream;
 import java.io.InputStreamReader;
 import java.net.URL;
 import java.util.ArrayList;
 import java.util.Iterator;
 import java.util.List;
 import java.util.StringTokenizer;

 import org.apache.felix.scr.impl.parser.KXml2SAXParser;
 import org.osgi.framework.BundleContext;
 import org.osgi.service.cm.ConfigurationAdmin;
 import org.osgi.service.component.ComponentException;
 import org.osgi.service.log.LogService;
 import org.osgi.util.tracker.ServiceTracker;


 /**
  * The BundleComponentActivator is helper class to load and unload Components of
  * a single bundle. It will read information from the metadata.xml file
  * descriptors and create the corresponding managers.
  */
 class BundleComponentActivator
 {
     // global component registration
     private ComponentRegistry m_componentRegistry;

     // The bundle context owning the registered component
     private BundleContext m_context = null;

     // This is a list of component instance managers that belong to a particular bundle
     private List m_managers = new ArrayList();

     // The Configuration Admin tracker providing configuration for components
     private ServiceTracker m_configurationAdmin;

     // The Configuration Admin tracker providing configuration for components
     private ServiceTracker m_logService;

     // thread acting upon configurations
     private ComponentActorThread m_componentActor;

     // true as long as the dispose method is not called
     private boolean m_active;

     // the logging level
     private int m_logLevel;


     /**
      * Called upon starting of the bundle. This method invokes initialize() which
      * parses the metadata and creates the instance managers
      *
      * @param componentRegistry The <code>ComponentRegistry</code> used to
      *      register components with to ensure uniqueness of component names
      *      and to ensure configuration updates.
      * @param   context  The bundle context owning the components
      *
      * @throws ComponentException if any error occurrs initializing this class
      */
     BundleComponentActivator( ComponentRegistry componentRegistry, ComponentActorThread componentActor,
         BundleContext context, int logLevel ) throws ComponentException
     {
         // keep the parameters for later
         m_componentRegistry = componentRegistry;
         m_componentActor = componentActor;
         m_context = context;

         // mark this instance active
         m_active = true;

         // have the Configuration Admin Service handy (if available)
         m_configurationAdmin = new ServiceTracker( context, ConfigurationAdmin.class.getName(), null );
         m_configurationAdmin.open();

         // have the LogService handy (if available)
         m_logService = new ServiceTracker( context, Activator.LOGSERVICE_CLASS, null );
         m_logService.open();
         m_logLevel = logLevel;

         // Get the Metadata-Location value from the manifest
         String descriptorLocations = ( String ) m_context.getBundle().getHeaders().get( "Service-Component" );
         if ( descriptorLocations == null )
         {
             throw new ComponentException( "Service-Component entry not found in the manifest" );
         }

         initialize( descriptorLocations );
     }


     /**
      * Gets the MetaData location, parses the meta data and requests the processing
      * of binder instances
      *
      * @param descriptorLocations A comma separated list of locations of
      *      component descriptors. This must not be <code>null</code>.
      *
      * @throws IllegalStateException If the bundle has already been uninstalled.
      */
     private void initialize( String descriptorLocations )
     {

         // 112.4.1: The value of the the header is a comma separated list of XML entries within the Bundle
         StringTokenizer st = new StringTokenizer( descriptorLocations, ", " );

         while ( st.hasMoreTokens() )
         {
             String descriptorLocation = st.nextToken();

             URL descriptorURL = m_context.getBundle().getResource( descriptorLocation );
             if ( descriptorURL == null )
             {
                 // 112.4.1 If an XML document specified by the header cannot be located in the bundle and its attached
                 // fragments, SCR must log an error message with the Log Service, if present, and continue.
                 log( LogService.LOG_ERROR, "Component descriptor entry '" + descriptorLocation + "' not found", null,
                     null );
                 continue;
             }

             InputStream stream = null;
             try
             {
                 stream = descriptorURL.openStream();

                 BufferedReader in = new BufferedReader( new InputStreamReader( stream ) );
                 XmlHandler handler = new XmlHandler( m_context.getBundle() );
                 KXml2SAXParser parser;

                 parser = new KXml2SAXParser( in );

                 parser.parseXML( handler );

                 // 112.4.2 Component descriptors may contain a single, root component element
                 // or one or more component elements embedded in a larger document
                 Iterator i = handler.getComponentMetadataList().iterator();
                 while ( i.hasNext() )
                 {
                     ComponentMetadata metadata = ( ComponentMetadata ) i.next();
                     try
                     {
                         // check and reserve the component name
                         m_componentRegistry.checkComponentName( metadata.getName() );

                         // validate the component metadata
                         metadata.validate();

                         // Request creation of the component manager
                         ComponentManager manager;
                         if ( metadata.isFactory() )
                         {
                             // 112.2.4 SCR must register a Component Factory
                             // service on behalf ot the component
                             // as soon as the component factory is satisfied
                             manager = new ComponentFactoryImpl( this, metadata, m_componentRegistry );
                         }
                         else
                         {
                             manager = ManagerFactory.createManager( this, metadata, m_componentRegistry
                                 .createComponentId() );
                         }

                         // register the component after validation
                         m_componentRegistry.registerComponent( metadata.getName(), manager );
                         m_managers.add( manager );

                         // enable the component
                         if ( metadata.isEnabled() )
                         {
                             manager.enable();
                         }
                     }
                     catch ( Throwable t )
                     {
                         // There is a problem with this particular component, we'll log the error
                         // and proceed to the next one
                         log( LogService.LOG_ERROR, "Cannot register Component", metadata, t );

                         // make sure the name is not reserved any more
                         m_componentRegistry.unregisterComponent( metadata.getName() );
                     }
                 }
             }
             catch ( IOException ex )
             {
                 // 112.4.1 If an XML document specified by the header cannot be located in the bundle and its attached
                 // fragments, SCR must log an error message with the Log Service, if present, and continue.

                 log( LogService.LOG_ERROR, "Problem reading descriptor entry '" + descriptorLocation + "'", null, ex );
             }
             catch ( Exception ex )
             {
                 log( LogService.LOG_ERROR, "General problem with descriptor entry '" + descriptorLocation + "'", null,
                     ex );
             }
             finally
             {
                 if ( stream != null )
                 {
                     try
                     {
                         stream.close();
                     }
                     catch ( IOException ignore )
                     {
                     }
                 }
             }
         }
     }


     /**
     * Dispose of this component activator instance and all the component
     * managers.
     */
     void dispose()
     {
         if ( m_context == null )
         {
             return;
         }

         // mark instance inactive (no more component activations)
         m_active = false;

         log( LogService.LOG_DEBUG, "BundleComponentActivator : Bundle [" + m_context.getBundle().getBundleId()
             + "] will destroy " + m_managers.size() + " instances", null, null );

         while ( m_managers.size() != 0 )
         {
             ComponentManager manager = ( ComponentManager ) m_managers.get( 0 );
             try
             {
                 m_managers.remove( manager );
                 manager.dispose();
             }
             catch ( Exception e )
             {
                 log( LogService.LOG_ERROR, "BundleComponentActivator : Exception invalidating", manager
                     .getComponentMetadata(), e );
             }
             finally
             {
                 m_componentRegistry.unregisterComponent( manager.getComponentMetadata().getName() );
             }

         }

         // close the Configuration Admin tracker
         if ( m_configurationAdmin != null )
         {
             m_configurationAdmin.close();
         }

         log( LogService.LOG_DEBUG, "BundleComponentActivator : Bundle [" + m_context.getBundle().getBundleId()
             + "] STOPPED", null, null );

         m_context = null;
     }


     /**
      * Returns <true> if this instance is active, that is if components may be
      * activated for this component. As soon as the {@link #dispose()} is called
      * which means this instance is being shutdown. After the call to <code>dispose</code>
      * this method always returns <code>false</code>.
      */
     boolean isActive()
     {
         return m_active;
     }


     /**
      * Returns the list of instance references currently associated to this activator
      *
      * @return the list of instance references
      */
     protected List getInstanceReferences()
     {
         return m_managers;
     }


     /**
     * Returns the BundleContext
     *
     * @return the BundleContext
     */
     protected BundleContext getBundleContext()
     {
         return m_context;
     }


     /**
      * Returns the <code>ConfigurationAdmin</code> service used to retrieve
      * configuration data for components managed by this activator or
      * <code>null</code> if no Configuration Admin Service is available in the
      * framework.
      */
     protected ConfigurationAdmin getConfigurationAdmin()
     {
         return ( ConfigurationAdmin ) m_configurationAdmin.getService();
     }


     /**
      * Implements the <code>ComponentContext.enableComponent(String)</code>
      * method by first finding the component(s) for the <code>name</code> and
      * then starting a thread to actually enable all components found.
      * <p>
      * If no component matching the given name is found the thread is not
      * started and the method does nothing.
      *
      * @param name The name of the component to enable or <code>null</code> to
      *      enable all components.
      */
     void enableComponent( String name )
     {
         final ComponentManager[] cm = getSelectedComponents( name );
         if ( cm == null )
         {
             return;
         }

         for ( int i = 0; i < cm.length; i++ )
         {
             try
             {
                 cm[i].enable();
             }
             catch ( Throwable t )
             {
                 log( LogService.LOG_ERROR, "Cannot enable component", cm[i].getComponentMetadata(), t );
             }
         }
     }


     /**
      * Implements the <code>ComponentContext.disableComponent(String)</code>
      * method by first finding the component(s) for the <code>name</code> and
      * then starting a thread to actually disable all components found.
      * <p>
      * If no component matching the given name is found the thread is not
      * started and the method does nothing.
      *
      * @param name The name of the component to disable or <code>null</code> to
      *      disable all components.
      */
     void disableComponent( String name )
     {
         final ComponentManager[] cm = getSelectedComponents( name );
         if ( cm == null )
         {
             return;
         }

         for ( int i = 0; i < cm.length; i++ )
         {
             try
             {
                 log( LogService.LOG_DEBUG, "Disabling Component", cm[i].getComponentMetadata(), null );
                 cm[i].disable();
             }
             catch ( Throwable t )
             {
                 log( LogService.LOG_ERROR, "Cannot disable component", cm[i].getComponentMetadata(), t );
             }
         }
     }


     /**
      * Returns an array of {@link ComponentManager} instances which match the
      * <code>name</code>. If the <code>name</code> is <code>null</code> an
      * array of all currently known component managers is returned. Otherwise
      * an array containing a single component manager matching the name is
      * returned if one is registered. Finally, if no component manager with the
      * given name is registered, <code>null</code> is returned.
      *
      * @param name The name of the component manager to return or
      *      <code>null</code> to return an array of all component managers.
      *
      * @return An array containing one or more component managers according
      *      to the <code>name</code> parameter or <code>null</code> if no
      *      component manager with the given name is currently registered.
      */
     private ComponentManager[] getSelectedComponents( String name )
     {
         // if all components are selected
         if ( name == null )
         {
             return (org.apache.felix.scr.impl.ComponentManager[] ) m_managers.toArray( new ComponentManager[m_managers.size()] );
         }

         if ( m_componentRegistry.getComponent( name ) != null )
         {
             // otherwise just find it
             Iterator it = m_managers.iterator();
             while ( it.hasNext() )
             {
                 ComponentManager cm = ( ComponentManager ) it.next();
                 if ( name.equals( cm.getComponentMetadata().getName() ) )
                 {
                     return new ComponentManager[]
                         { cm };
                 }
             }
         }

         // if the component is not known
         return null;
     }


     //---------- Asynchronous Component Handling ------------------------------

     /**
      * Schedules the given <code>task</code> for asynchrounous execution or
      * synchronously runs the task if the thread is not running. If this instance
      * is {@link #isActive() not active}, the task is not executed.
      *
      * @param task The component task to execute
      */
     void schedule( Runnable task )
     {
         if ( isActive() )
         {
             ComponentActorThread cat = m_componentActor;
             if ( cat != null )
             {
                 cat.schedule( task );
             }
             else
             {
                 log( LogService.LOG_INFO, "Component Actor Thread not running, calling synchronously", null, null );
                 try
                 {
                     synchronized ( this )
                     {
                         task.run();
                     }
                 }
                 catch ( Throwable t )
                 {
                     log( LogService.LOG_INFO, "Unexpected problem executing task", null, t );
                 }
             }
         }
         else
         {
             log( LogService.LOG_INFO, "BundleComponentActivator is not active; not scheduling " + task, null, null );
         }
     }


     /**
      * Method to actually emit the log message. If the LogService is available,
      * the message will be logged through the LogService. Otherwise the message
      * is logged to stdout (or stderr in case of LOG_ERROR level messages),
      *
      * @param level The log level to log the message at
      * @param message The message to log
      * @param ex An optional <code>Throwable</code> whose stack trace is written,
      *      or <code>null</code> to not log a stack trace.
      */
     void log( int level, String message, ComponentMetadata metadata, Throwable ex )
     {

         if ( m_logLevel >= level )
         {
             // prepend the metadata name to the message
             if ( metadata != null )
             {
                 message = "[" + metadata.getName() + "] " + message;
             }

             Object logger = m_logService.getService();
             if ( logger == null )
             {
                 Activator.log( level, getBundleContext().getBundle(), message, ex );
             }
             else
             {
                 ( ( LogService ) logger ).log( level, message, ex );
             }
         }
     }

 }
	/*
	* 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.apache.felix.scr.impl;


	import java.io.BufferedReader;
	import java.io.IOException;
	import java.io.InputStream;
	import java.io.InputStreamReader;
	import java.net.URL;
	import java.util.ArrayList;
	import java.util.Iterator;
	import java.util.List;
	import java.util.StringTokenizer;

	import org.apache.felix.scr.impl.parser.KXml2SAXParser;
	import org.osgi.framework.BundleContext;
	import org.osgi.service.cm.ConfigurationAdmin;
	import org.osgi.service.component.ComponentException;
	import org.osgi.service.log.LogService;
	import org.osgi.util.tracker.ServiceTracker;


	/**
	* The BundleComponentActivator is helper class to load and unload Components of
	* a single bundle. It will read information from the metadata.xml file
	* descriptors and create the corresponding managers.
	*/
	class BundleComponentActivator
	{
	// global component registration
	private ComponentRegistry m_componentRegistry;

	// The bundle context owning the registered component
	private BundleContext m_context = null;

	// This is a list of component instance managers that belong to a particular bundle
	private List m_managers = new ArrayList();

	// The Configuration Admin tracker providing configuration for components
	private ServiceTracker m_configurationAdmin;

	// The Configuration Admin tracker providing configuration for components
	private ServiceTracker m_logService;

	// thread acting upon configurations
	private ComponentActorThread m_componentActor;

	// true as long as the dispose method is not called
	private boolean m_active;

	// the logging level
	private int m_logLevel;


	/**
	* Called upon starting of the bundle. This method invokes initialize() which
	* parses the metadata and creates the instance managers
	*
	* @param componentRegistry The <code>ComponentRegistry</code> used to
	* register components with to ensure uniqueness of component names
	* and to ensure configuration updates.
	* @param context The bundle context owning the components
	*
	* @throws ComponentException if any error occurrs initializing this class
	*/
	BundleComponentActivator( ComponentRegistry componentRegistry, ComponentActorThread componentActor,
	BundleContext context, int logLevel ) throws ComponentException
	{
	// keep the parameters for later
	m_componentRegistry = componentRegistry;
	m_componentActor = componentActor;
	m_context = context;

	// mark this instance active
	m_active = true;

	// have the Configuration Admin Service handy (if available)
	m_configurationAdmin = new ServiceTracker( context, ConfigurationAdmin.class.getName(), null );
	m_configurationAdmin.open();

	// have the LogService handy (if available)
	m_logService = new ServiceTracker( context, Activator.LOGSERVICE_CLASS, null );
	m_logService.open();
	m_logLevel = logLevel;

	// Get the Metadata-Location value from the manifest
	String descriptorLocations = ( String ) m_context.getBundle().getHeaders().get( "Service-Component" );
	if ( descriptorLocations == null )
	{
	throw new ComponentException( "Service-Component entry not found in the manifest" );
	}

	initialize( descriptorLocations );
	}


	/**
	* Gets the MetaData location, parses the meta data and requests the processing
	* of binder instances
	*
	* @param descriptorLocations A comma separated list of locations of
	* component descriptors. This must not be <code>null</code>.
	*
	* @throws IllegalStateException If the bundle has already been uninstalled.
	*/
	private void initialize( String descriptorLocations )
	{

	// 112.4.1: The value of the the header is a comma separated list of XML entries within the Bundle
	StringTokenizer st = new StringTokenizer( descriptorLocations, ", " );

	while ( st.hasMoreTokens() )
	{
	String descriptorLocation = st.nextToken();

	URL descriptorURL = m_context.getBundle().getResource( descriptorLocation );
	if ( descriptorURL == null )
	{
	// 112.4.1 If an XML document specified by the header cannot be located in the bundle and its attached
	// fragments, SCR must log an error message with the Log Service, if present, and continue.
	log( LogService.LOG_ERROR, "Component descriptor entry '" + descriptorLocation + "' not found", null,
	null );
	continue;
	}

	InputStream stream = null;
	try
	{
	stream = descriptorURL.openStream();

	BufferedReader in = new BufferedReader( new InputStreamReader( stream ) );
	XmlHandler handler = new XmlHandler( m_context.getBundle() );
	KXml2SAXParser parser;

	parser = new KXml2SAXParser( in );

	parser.parseXML( handler );

	// 112.4.2 Component descriptors may contain a single, root component element
	// or one or more component elements embedded in a larger document
	Iterator i = handler.getComponentMetadataList().iterator();
	while ( i.hasNext() )
	{
	ComponentMetadata metadata = ( ComponentMetadata ) i.next();
	try
	{
	// check and reserve the component name
	m_componentRegistry.checkComponentName( metadata.getName() );

	// validate the component metadata
	metadata.validate();

	// Request creation of the component manager
	ComponentManager manager;
	if ( metadata.isFactory() )
	{
	// 112.2.4 SCR must register a Component Factory
	// service on behalf ot the component
	// as soon as the component factory is satisfied
	manager = new ComponentFactoryImpl( this, metadata, m_componentRegistry );
	}
	else
	{
	manager = ManagerFactory.createManager( this, metadata, m_componentRegistry
	.createComponentId() );
	}

	// register the component after validation
	m_componentRegistry.registerComponent( metadata.getName(), manager );
	m_managers.add( manager );

	// enable the component
	if ( metadata.isEnabled() )
	{
	manager.enable();
	}
	}
	catch ( Throwable t )
	{
	// There is a problem with this particular component, we'll log the error
	// and proceed to the next one
	log( LogService.LOG_ERROR, "Cannot register Component", metadata, t );

	// make sure the name is not reserved any more
	m_componentRegistry.unregisterComponent( metadata.getName() );
	}
	}
	}
	catch ( IOException ex )
	{
	// 112.4.1 If an XML document specified by the header cannot be located in the bundle and its attached
	// fragments, SCR must log an error message with the Log Service, if present, and continue.

	log( LogService.LOG_ERROR, "Problem reading descriptor entry '" + descriptorLocation + "'", null, ex );
	}
	catch ( Exception ex )
	{
	log( LogService.LOG_ERROR, "General problem with descriptor entry '" + descriptorLocation + "'", null,
	ex );
	}
	finally
	{
	if ( stream != null )
	{
	try
	{
	stream.close();
	}
	catch ( IOException ignore )
	{
	}
	}
	}
	}
	}


	/**
	* Dispose of this component activator instance and all the component
	* managers.
	*/
	void dispose()
	{
	if ( m_context == null )
	{
	return;
	}

	// mark instance inactive (no more component activations)
	m_active = false;

	log( LogService.LOG_DEBUG, "BundleComponentActivator : Bundle [" + m_context.getBundle().getBundleId()
	+ "] will destroy " + m_managers.size() + " instances", null, null );

	while ( m_managers.size() != 0 )
	{
	ComponentManager manager = ( ComponentManager ) m_managers.get( 0 );
	try
	{
	m_managers.remove( manager );
	manager.dispose();
	}
	catch ( Exception e )
	{
	log( LogService.LOG_ERROR, "BundleComponentActivator : Exception invalidating", manager
	.getComponentMetadata(), e );
	}
	finally
	{
	m_componentRegistry.unregisterComponent( manager.getComponentMetadata().getName() );
	}

	}

	// close the Configuration Admin tracker
	if ( m_configurationAdmin != null )
	{
	m_configurationAdmin.close();
	}

	log( LogService.LOG_DEBUG, "BundleComponentActivator : Bundle [" + m_context.getBundle().getBundleId()
	+ "] STOPPED", null, null );

	m_context = null;
	}


	/**
	* Returns <true> if this instance is active, that is if components may be
	* activated for this component. As soon as the {@link #dispose()} is called
	* which means this instance is being shutdown. After the call to <code>dispose</code>
	* this method always returns <code>false</code>.
	*/
	boolean isActive()
	{
	return m_active;
	}


	/**
	* Returns the list of instance references currently associated to this activator
	*
	* @return the list of instance references
	*/
	protected List getInstanceReferences()
	{
	return m_managers;
	}


	/**
	* Returns the BundleContext
	*
	* @return the BundleContext
	*/
	protected BundleContext getBundleContext()
	{
	return m_context;
	}


	/**
	* Returns the <code>ConfigurationAdmin</code> service used to retrieve
	* configuration data for components managed by this activator or
	* <code>null</code> if no Configuration Admin Service is available in the
	* framework.
	*/
	protected ConfigurationAdmin getConfigurationAdmin()
	{
	return ( ConfigurationAdmin ) m_configurationAdmin.getService();
	}


	/**
	* Implements the <code>ComponentContext.enableComponent(String)</code>
	* method by first finding the component(s) for the <code>name</code> and
	* then starting a thread to actually enable all components found.
	* <p>
	* If no component matching the given name is found the thread is not
	* started and the method does nothing.
	*
	* @param name The name of the component to enable or <code>null</code> to
	* enable all components.
	*/
	void enableComponent( String name )
	{
	final ComponentManager[] cm = getSelectedComponents( name );
	if ( cm == null )
	{
	return;
	}

	for ( int i = 0; i < cm.length; i++ )
	{
	try
	{
	cm[i].enable();
	}
	catch ( Throwable t )
	{
	log( LogService.LOG_ERROR, "Cannot enable component", cm[i].getComponentMetadata(), t );
	}
	}
	}


	/**
	* Implements the <code>ComponentContext.disableComponent(String)</code>
	* method by first finding the component(s) for the <code>name</code> and
	* then starting a thread to actually disable all components found.
	* <p>
	* If no component matching the given name is found the thread is not
	* started and the method does nothing.
	*
	* @param name The name of the component to disable or <code>null</code> to
	* disable all components.
	*/
	void disableComponent( String name )
	{
	final ComponentManager[] cm = getSelectedComponents( name );
	if ( cm == null )
	{
	return;
	}

	for ( int i = 0; i < cm.length; i++ )
	{
	try
	{
	log( LogService.LOG_DEBUG, "Disabling Component", cm[i].getComponentMetadata(), null );
	cm[i].disable();
	}
	catch ( Throwable t )
	{
	log( LogService.LOG_ERROR, "Cannot disable component", cm[i].getComponentMetadata(), t );
	}
	}
	}


	/**
	* Returns an array of {@link ComponentManager} instances which match the
	* <code>name</code>. If the <code>name</code> is <code>null</code> an
	* array of all currently known component managers is returned. Otherwise
	* an array containing a single component manager matching the name is
	* returned if one is registered. Finally, if no component manager with the
	* given name is registered, <code>null</code> is returned.
	*
	* @param name The name of the component manager to return or
	* <code>null</code> to return an array of all component managers.
	*
	* @return An array containing one or more component managers according
	* to the <code>name</code> parameter or <code>null</code> if no
	* component manager with the given name is currently registered.
	*/
	private ComponentManager[] getSelectedComponents( String name )
	{
	// if all components are selected
	if ( name == null )
	{
	return (org.apache.felix.scr.impl.ComponentManager[] ) m_managers.toArray( new ComponentManager[m_managers.size()] );
	}

	if ( m_componentRegistry.getComponent( name ) != null )
	{
	// otherwise just find it
	Iterator it = m_managers.iterator();
	while ( it.hasNext() )
	{
	ComponentManager cm = ( ComponentManager ) it.next();
	if ( name.equals( cm.getComponentMetadata().getName() ) )
	{
	return new ComponentManager[]
	{ cm };
	}
	}
	}

	// if the component is not known
	return null;
	}


	//---------- Asynchronous Component Handling ------------------------------

	/**
	* Schedules the given <code>task</code> for asynchrounous execution or
	* synchronously runs the task if the thread is not running. If this instance
	* is {@link #isActive() not active}, the task is not executed.
	*
	* @param task The component task to execute
	*/
	void schedule( Runnable task )
	{
	if ( isActive() )
	{
	ComponentActorThread cat = m_componentActor;
	if ( cat != null )
	{
	cat.schedule( task );
	}
	else
	{
	log( LogService.LOG_INFO, "Component Actor Thread not running, calling synchronously", null, null );
	try
	{
	synchronized ( this )
	{
	task.run();
	}
	}
	catch ( Throwable t )
	{
	log( LogService.LOG_INFO, "Unexpected problem executing task", null, t );
	}
	}
	}
	else
	{
	log( LogService.LOG_INFO, "BundleComponentActivator is not active; not scheduling " + task, null, null );
	}
	}


	/**
	* Method to actually emit the log message. If the LogService is available,
	* the message will be logged through the LogService. Otherwise the message
	* is logged to stdout (or stderr in case of LOG_ERROR level messages),
	*
	* @param level The log level to log the message at
	* @param message The message to log
	* @param ex An optional <code>Throwable</code> whose stack trace is written,
	* or <code>null</code> to not log a stack trace.
	*/
	void log( int level, String message, ComponentMetadata metadata, Throwable ex )
	{

	if ( m_logLevel >= level )
	{
	// prepend the metadata name to the message
	if ( metadata != null )
	{
	message = "[" + metadata.getName() + "] " + message;
	}

	Object logger = m_logService.getService();
	if ( logger == null )
	{
	Activator.log( level, getBundleContext().getBundle(), message, ex );
	}
	else
	{
	( ( LogService ) logger ).log( level, message, ex );
	}
	}
	}

	}