plugins/org.eclipse.sphinx.emf.workspace/src/org/eclipse/sphinx/emf/workspace/internal/saving/ModelSaveLifecycleListenerRegistry.java - sphinx/org.eclipse.sphinx - Git at Google

 /**
  * <copyright>
  *
  * Copyright (c) 2008-2012 See4sys, BMW Car IT and others.
  * All rights reserved. This program and the accompanying materials
  * are made available under the terms of the Eclipse Public License v2.0
  * which accompanies this distribution, and is available at
  * https://www.eclipse.org/org/documents/epl-2.0/EPL-2.0.html
  *
  * Contributors:
  *     See4sys - Initial API and implementation
  *     BMW Car IT - Lazy extension initialization
  *
  * </copyright>
  */
 package org.eclipse.sphinx.emf.workspace.internal.saving;

 import java.util.Collection;
 import java.util.HashMap;
 import java.util.HashSet;
 import java.util.Iterator;
 import java.util.Map;
 import java.util.Set;

 import org.eclipse.core.runtime.IConfigurationElement;
 import org.eclipse.core.runtime.Platform;
 import org.eclipse.sphinx.emf.Activator;
 import org.eclipse.sphinx.emf.metamodel.IMetaModelDescriptor;
 import org.eclipse.sphinx.emf.metamodel.MetaModelDescriptorRegistry;
 import org.eclipse.sphinx.emf.workspace.saving.IModelSaveLifecycleListener;
 import org.eclipse.sphinx.platform.util.PlatformLogUtil;
 import org.osgi.framework.Bundle;

 /**
  * The singleton instance that is responsible for managing {@linkplain IModelSaveLifecycleListener model save lifecycle
  * listener}s that have been contributed to the platform <em>via</em> extension point
  * <tt>org.eclipse.sphinx.emf.workspace.modelSaveLifecycleListeners</tt>.
  * <p>
  * This registry mainly provides one method allowing to retrieve {@linkplain IModelSaveLifecycleListener listener}s
  * corresponding to one specified {@linkplain IMetaModelDescriptor meta-model descriptor}.
  *
  * @since 0.8.0
  */
 public class ModelSaveLifecycleListenerRegistry {

 	/**
 	 * The singleton instance of this registry.
 	 */
 	public static final ModelSaveLifecycleListenerRegistry INSTANCE = new ModelSaveLifecycleListenerRegistry();

 	/**
 	 * Identifier of Model Save Lifecycle Listeners extension point.
 	 */
 	private static final String EXTP_MODEL_SAVLE_LIFECYCLE_LISTENERS = "org.eclipse.sphinx.emf.workspace.modelSaveLifecycleListeners"; //$NON-NLS-1$

 	private static final String NODE_LISTENER = "listener"; //$NON-NLS-1$
 	private static final String ATTR_ID = "id"; //$NON-NLS-1$
 	private static final String ATTR_CLASS = "class"; //$NON-NLS-1$
 	private static final String ATTR_OVERRIDE = "override"; //$NON-NLS-1$

 	private static final String NODE_APPLICABLE_FOR = "applicableFor"; //$NON-NLS-1$
 	private static final String ATTR_MMDESC_ID_PATTERN = "metaModelDescriptorIdPattern"; //$NON-NLS-1$

 	/**
 	 * Flag to track lazy initialization.
 	 */
 	private boolean isInitialized = false;

 	/**
 	 * The registered {@linkplain IModelSaveLifecycleListener model save lifecycle listener}s or
 	 * {@linkplain ListenerDescriptor listener descriptor}s
 	 */
 	private Map<IMetaModelDescriptor, Map<String, Object>> modelSaveLifecycleListeners = new HashMap<IMetaModelDescriptor, Map<String, Object>>();

 	/**
 	 * The {@linkplain IModelSaveLifecycleListener model save lifecycle listener}s which are overridden by other ones.
 	 */
 	private Map<String, Set<IMetaModelDescriptor>> fOutstandingOverrides = new HashMap<String, Set<IMetaModelDescriptor>>();

 	/**
 	 * The descriptor that is used to store the listener information prior to instantiation
 	 */
 	private class ListenerDescriptor {

 		private String className;
 		private String contributorPluginId;

 		/**
 		 * @param className
 		 * @param contributorPluginId
 		 */
 		private ListenerDescriptor(String className, String contributorPluginId) {
 			this.className = className;
 			this.contributorPluginId = contributorPluginId;
 		}

 		/**
 		 * Construct and return the listener. This method might trigger plugin loading.
 		 *
 		 * @return the listener
 		 * @throws ClassNotFoundException
 		 * @throws IllegalAccessException
 		 * @throws InstantiationException
 		 */
 		private IModelSaveLifecycleListener getListener() throws ClassNotFoundException, InstantiationException, IllegalAccessException {
 			Bundle bundle = Platform.getBundle(contributorPluginId);
 			Class<?> factoryClz = bundle.loadClass(className);
 			return (IModelSaveLifecycleListener) factoryClz.newInstance();
 		}
 	}

 	/**
 	 * Private constructor for singleton pattern.
 	 */
 	private ModelSaveLifecycleListenerRegistry() {

 	}

 	/**
 	 * Reads contributions to the <em>Model Save Lifecycle Listeners</em> extension point.
 	 */
 	private void readContributedModelSaveLifecycleListeners() {
 		for (IConfigurationElement cfgElement : Platform.getExtensionRegistry().getConfigurationElementsFor(EXTP_MODEL_SAVLE_LIFECYCLE_LISTENERS)) {
 			try {
 				if (NODE_LISTENER.equals(cfgElement.getName())) {
 					String listenerId = cfgElement.getAttribute(ATTR_ID);
 					String overriddenListenerId = cfgElement.getAttribute(ATTR_OVERRIDE);

 					// Create a descriptor for the listener
 					ListenerDescriptor descriptor = new ListenerDescriptor(cfgElement.getAttribute(ATTR_CLASS), cfgElement.getContributor().getName());

 					// Register it upon meta-model descriptor is must be available for
 					for (IConfigurationElement applicableFor : cfgElement.getChildren(NODE_APPLICABLE_FOR)) {
 						String mmDescIdPattern = applicableFor.getAttribute(ATTR_MMDESC_ID_PATTERN);
 						addListenerDescriptor(mmDescIdPattern, listenerId, descriptor, overriddenListenerId);
 					}
 				}
 			} catch (Exception ex) {
 				PlatformLogUtil.logAsError(Activator.getPlugin(), ex);
 			}
 		}

 		// Remove overridden model save lifecycle listeners that couldn't be removed earlier
 		for (String overriddenListenerId : fOutstandingOverrides.keySet()) {
 			for (IMetaModelDescriptor mmDescriptor : fOutstandingOverrides.get(overriddenListenerId)) {
 				Map<String, Object> listenersForMetaModel = modelSaveLifecycleListeners.get(mmDescriptor);
 				if (listenersForMetaModel != null) {
 					listenersForMetaModel.remove(overriddenListenerId);
 				}
 			}
 		}
 		fOutstandingOverrides.clear();
 	}

 	/**
 	 * Adds the specified {@linkplain ListenerDescriptor listener descriptor} to the map of registered listeners and
 	 * descriptors that have been contributed to the platform through
 	 * <tt>org.eclipse.sphinx.emf.workspace.modelSaveLifecycleListeners</tt> extension point.
 	 *
 	 * @param mmDescIdPattern
 	 *            The {@linkplain IMetaModelDescriptor meta-model descriptor} identifier pattern allowing to retrieve
 	 *            the meta-model descriptors the specified {@linkplain IModelSaveLifecycleListener model save lifecycle
 	 *            listener} must be associated to. Should not be <code>null</code>.
 	 * @param listenerId
 	 *            The identifier of the {@linkplain IModelSaveLifecycleListener model save lifecycle listener} to be
 	 *            registered. Should not be null.
 	 * @param descriptor
 	 *            The {@linkplain ListenerDescriptor listener descriptor} that must be registered on the
 	 *            {@linkplain ModelSaveLifecycleListenerRegistry model save lifecycle listener registry} for the
 	 *            {@linkplain IMetaModelDescriptor meta-model descriptor}s that match the specified
 	 *            <code>mmDescIdPattern</code>. Should not be <code>null</code>.
 	 * @param overriddenListenerId
 	 *            The identifier of some other {@linkplain IModelSaveLifecycleListener model save lifecycle listener} to
 	 *            be overridden or <code>null</code> when no overriding is required.
 	 */
 	private void addListenerDescriptor(String mmDescIdPattern, String listenerId, ListenerDescriptor descriptor, String overriddenListenerId) {
 		if (".*".equals(mmDescIdPattern) || ".+".equals(mmDescIdPattern)) { //$NON-NLS-1$ //$NON-NLS-2$
 			addListenerDescriptor(MetaModelDescriptorRegistry.ANY_MM, listenerId, descriptor, overriddenListenerId);
 			return;
 		}

 		for (IMetaModelDescriptor mmDescriptor : MetaModelDescriptorRegistry.INSTANCE.getDescriptors(mmDescIdPattern)) {
 			addListenerDescriptor(mmDescriptor, listenerId, descriptor, overriddenListenerId);
 		}
 	}

 	/**
 	 * Adds the specified {@linkplain ListenerDescriptor listener descriptor} to the map of registered listeners and
 	 * descriptors that have been contributed to the platform through
 	 * <tt>org.eclipse.sphinx.emf.workspace.modelSaveLifecycleListeners</tt> extension point.
 	 *
 	 * @param mmDescriptor
 	 *            The {@linkplain IMetaModelDescriptor meta-model descriptor} the specified
 	 *            {@linkplain IModelSaveLifecycleListener model save lifecycle listener} must be associated to. Should
 	 *            not be <code>null</code>.
 	 * @param listenerId
 	 *            The identifier of the {@linkplain IModelSaveLifecycleListener model save lifecycle listener} to be
 	 *            registered. Shall not be null.
 	 * @param descriptor
 	 *            The {@linkplain ListenerDescriptor listener descriptor} that must be registered on the
 	 *            {@linkplain ModelSaveLifecycleListenerRegistry model save lifecycle listener registry} for the
 	 *            {@linkplain IMetaModelDescriptor meta-model descriptor}s that match the specified
 	 *            <code>mmDescIdPattern</code>. Should not be <code>null</code>.
 	 * @param overriddenListenerId
 	 *            The identifier of some other {@linkplain IModelSaveLifecycleListener model save lifecycle listener} to
 	 *            be overridden or <code>null</code> when no overriding is required.
 	 */
 	private void addListenerDescriptor(IMetaModelDescriptor mmDescriptor, String listenerId, ListenerDescriptor descriptor,
 			String overriddenListenerId) {
 		if (mmDescriptor != null && descriptor != null) {
 			// Register model save lifecycle listener for given meta-model descriptor
 			Map<String, Object> listenersForMetaModel = modelSaveLifecycleListeners.get(mmDescriptor);
 			if (listenersForMetaModel == null) {
 				listenersForMetaModel = new HashMap<String, Object>();
 				modelSaveLifecycleListeners.put(mmDescriptor, listenersForMetaModel);
 			}
 			listenersForMetaModel.put(listenerId, descriptor);

 			// Manage overridden model save lifecycle listener, if any
 			if (overriddenListenerId != null) {
 				// Remove overridden model save lifecycle listener; remember it for being removed later if it is not
 				// present yet
 				if (listenersForMetaModel.remove(overriddenListenerId) == null) {
 					Set<IMetaModelDescriptor> overridesForListener = fOutstandingOverrides.get(overriddenListenerId);
 					if (overridesForListener == null) {
 						overridesForListener = new HashSet<IMetaModelDescriptor>();
 						fOutstandingOverrides.put(overriddenListenerId, overridesForListener);
 					}
 					overridesForListener.add(mmDescriptor);
 				}
 			}
 		}
 	}

 	/**
 	 * @param mmDescriptor
 	 *            The {@linkplain IMetaModelDescriptor meta-model descriptor} for which matching
 	 *            {@linkplain IModelSaveLifecycleListener model save lifecycle listener}s must be returned.
 	 * @return The {@linkplain IModelSaveLifecycleListener model save lifecycle listener}s that have been contributed to
 	 *         the platform <em>via</em> <tt>modelSaveLifecycleListeners</tt> extension point and that match the
 	 *         specified {@linkplain IMetaModelDescriptor meta-model descriptor}.
 	 */
 	public Collection<IModelSaveLifecycleListener> getListeners(IMetaModelDescriptor mmDescriptor) {
 		synchronized (this) {
 			if (isInitialized == false) {
 				readContributedModelSaveLifecycleListeners();
 				isInitialized = true;
 			}
 		}

 		// Retrieve model save lifecycle listeners registered upon specified meta-model descriptor or one
 		// of its super
 		// descriptors
 		Set<IModelSaveLifecycleListener> listeners = new HashSet<IModelSaveLifecycleListener>();
 		for (IMetaModelDescriptor registeredMMDescriptor : modelSaveLifecycleListeners.keySet()) {
 			if (registeredMMDescriptor.getClass().isInstance(mmDescriptor)) {
 				Map<String, Object> listenersForMetaModel = modelSaveLifecycleListeners.get(registeredMMDescriptor);
 				listeners.addAll(getListeners(listenersForMetaModel));
 			}
 		}

 		// Retrieve model save lifecycle listeners registered upon static any meta-model descriptor
 		Map<String, Object> listenersForAnyMetaModel = modelSaveLifecycleListeners.get(MetaModelDescriptorRegistry.ANY_MM);
 		if (listenersForAnyMetaModel != null) {
 			listeners.addAll(getListeners(listenersForAnyMetaModel));
 		}
 		return listeners;
 	}

 	/**
 	 * Returns a set of {@linkplain IModelSaveLifecycleListener model save lifecycle listeners} that are contained or
 	 * described by the entries in given <code>listenersOrDescriptors</code> map.
 	 * <p>
 	 * Depending on the type of the listener object contained by each map entry one of the following actions is taken:
 	 * <ul>
 	 * <li>Instances of {@linkplain IModelSaveLifecycleListener model save lifecycle listener}s are directly added to
 	 * the resulting listener set.</li>
 	 * <li>Instances of {@linkplain ListenerDescriptor model save lifecycle listener descriptor}s are used to create the
 	 * actual {@linkplain IModelSaveLifecycleListener model save lifecycle listener}s and add those to the resulting
 	 * listener set. In addition the formers are replaced by the latters in given <code>listenersOrDescriptors</code>
 	 * map.</li>
 	 * <li>Instances of anything else are logged as errors and removed from given <code>listenersOrDescriptors</code>
 	 * map.
 	 * </p>
 	 *
 	 * @param listenersOrDescriptors
 	 *            The map with {@linkplain IModelSaveLifecycleListener model save lifecycle listener}s or
 	 *            {@linkplain ListenerDescriptor model save lifecycle listener descriptor}s and their respective
 	 *            identifiers to be processed.
 	 * @return A set of {@linkplain IModelSaveLifecycleListener model save lifecycle listener}s that are contained or
 	 *         described by the entries in given <code>listenersOrDescriptors </code> map.
 	 */
 	private Set<IModelSaveLifecycleListener> getListeners(Map<String, Object> listenersOrDescriptors) {
 		Set<IModelSaveLifecycleListener> listeners = new HashSet<IModelSaveLifecycleListener>();
 		for (Iterator<String> iter = listenersOrDescriptors.keySet().iterator(); iter.hasNext();) {
 			String listenerId = iter.next();
 			Object listenerObject = listenersOrDescriptors.get(listenerId);
 			if (listenerObject instanceof IModelSaveLifecycleListener) {
 				// Add existing listener
 				listeners.add((IModelSaveLifecycleListener) listenerObject);
 			} else if (listenerObject instanceof ListenerDescriptor) {
 				// Create the listener
 				try {
 					IModelSaveLifecycleListener listener = ((ListenerDescriptor) listenerObject).getListener();
 					listenersOrDescriptors.put(listenerId, listener);
 					listeners.add(listener);
 				} catch (Exception ex) {
 					PlatformLogUtil.logAsError(Activator.getPlugin(), ex);

 					// Discard bad descriptor so as to avoid repeated runs into same problem
 					iter.remove();
 				}
 			} else {
 				// Should not happen...
 				PlatformLogUtil.logAsError(Activator.getPlugin(), "Invalid model save lifecycle listener object: " //$NON-NLS-1$
 						+ listenerObject.getClass().getName());

 				// Discard bad descriptor so as to avoid repeated runs into same problem
 				iter.remove();
 			}
 		}
 		return listeners;
 	}

 	/**
 	 * Adds the specified {@linkplain IModelSaveLifecycleListener model save lifecycle listener} to the map of
 	 * registered listeners that have been contributed to the platform through
 	 * <tt>org.eclipse.sphinx.emf.modelSaveLifecycleListeners</tt> extension point.
 	 *
 	 * @param mmDescIdPattern
 	 *            The {@linkplain IMetaModelDescriptor meta-model descriptor} identifier pattern allowing to retrieve
 	 *            the meta-model descriptors the specified {@linkplain IModelSaveLifecycleListener model save lifecycle
 	 *            listener} must be associated to. Should not be <code>null</code>.
 	 * @param listenerId
 	 *            The identifier of the {@linkplain IModelSaveLifecycleListener model save lifecycle listener} to be
 	 *            registered. If <code>null</code> the {@linkplain IModelSaveLifecycleListener model save lifecycle
 	 *            listener} 's identifier will be automatically computed based the result of
 	 *            {@linkplain IModelSaveLifecycleListener#toString() toString()}.
 	 * @param listener
 	 *            The {@linkplain IModelSaveLifecycleListener model save lifecycle listener} that must be registered on
 	 *            the {@linkplain ModelSaveLifecycleListenerRegistry model save lifecycle listener registry} for the
 	 *            {@linkplain IMetaModelDescriptor meta-model descriptor}s that match the specified
 	 *            <code>mmDescIdPattern</code>. Should not be <code>null</code>.
 	 * @param overriddenListenerId
 	 *            The identifier of some other {@linkplain IModelSaveLifecycleListener model save lifecycle listener} to
 	 *            be overridden or <code>null</code> when no overriding is required.
 	 */
 	public void addListener(String mmDescIdPattern, String listenerId, IModelSaveLifecycleListener listener, String overriddenListenerId) {
 		/*
 		 * !! Important Note !! If given meta-model descriptor id pattern matches anything register specified model save
 		 * lifecycle listener only with static any meta-model descriptor rather than with all meta-model matching
 		 * descriptors. This makes sure that the listener will not only be invoked for all static (contributed)
 		 * meta-model descriptors but also for all dynamic meta-model descriptors including those which are created
 		 * subsequently, i.e. AFTER the installation of specified listener.
 		 */
 		if (".*".equals(mmDescIdPattern) || ".+".equals(mmDescIdPattern)) { //$NON-NLS-1$ //$NON-NLS-2$
 			addListener(MetaModelDescriptorRegistry.ANY_MM, listenerId, listener, overriddenListenerId);
 			return;
 		}

 		for (IMetaModelDescriptor mmDescriptor : MetaModelDescriptorRegistry.INSTANCE.getDescriptors(mmDescIdPattern)) {
 			addListener(mmDescriptor, listenerId, listener, overriddenListenerId);
 		}
 	}

 	/**
 	 * Adds the specified {@linkplain IModelSaveLifecycleListener model save lifecycle listener} to the map of
 	 * registered listeners that have been contributed to the platform through
 	 * <tt>org.eclipse.sphinx.emf.modelSaveLifecycleListeners</tt> extension point.
 	 *
 	 * @param mmDescriptor
 	 *            The {@linkplain IMetaModelDescriptor meta-model descriptor} the specified
 	 *            {@linkplain IModelSaveLifecycleListener model save lifecycle listener} must be associated to. Should
 	 *            not be <code>null</code>.
 	 * @param listenerId
 	 *            The identifier of the {@linkplain IModelSaveLifecycleListener model save lifecycle listener} to be
 	 *            registered. If <code>null</code> the {@linkplain IModelSaveLifecycleListener model save lifecycle
 	 *            listener} 's identifier will be automatically computed based the result of
 	 *            {@linkplain IModelSaveLifecycleListener#toString() toString()}.
 	 * @param listener
 	 *            The {@linkplain IModelSaveLifecycleListener model save lifecycle listener} that must be registered on
 	 *            the {@linkplain ModelSaveLifecycleListenerRegistry model save lifecycle listener registry} for the
 	 *            {@linkplain IMetaModelDescriptor meta-model descriptor}s that match the specified
 	 *            <code>mmDescIdPattern</code>. Should not be <code>null</code>.
 	 * @param overriddenListenerId
 	 *            The identifier of some other {@linkplain IModelSaveLifecycleListener model save lifecycle listener} to
 	 *            be overridden or <code>null</code> when no overriding is required.
 	 */
 	public void addListener(IMetaModelDescriptor mmDescriptor, String listenerId, IModelSaveLifecycleListener listener, String overriddenListenerId) {
 		if (mmDescriptor != null && listener != null) {
 			// Register model save lifecycle listener for given meta-model descriptor
 			Map<String, Object> listenersForMetaModel = modelSaveLifecycleListeners.get(mmDescriptor);
 			if (listenersForMetaModel == null) {
 				listenersForMetaModel = new HashMap<String, Object>();
 				modelSaveLifecycleListeners.put(mmDescriptor, listenersForMetaModel);
 			}
 			listenersForMetaModel.put(listenerId != null ? listenerId : listener.toString(), listener);

 			// Manage overridden model save lifecycle listener, if any
 			if (overriddenListenerId != null) {
 				// Remove overridden model save lifecycle listener; remember it for being removed later
 				// if it is not
 				// present yet
 				if (listenersForMetaModel.remove(overriddenListenerId) == null) {
 					Set<IMetaModelDescriptor> overridesForListener = fOutstandingOverrides.get(overriddenListenerId);
 					if (overridesForListener == null) {
 						overridesForListener = new HashSet<IMetaModelDescriptor>();
 						fOutstandingOverrides.put(overriddenListenerId, overridesForListener);
 					}
 					overridesForListener.add(mmDescriptor);
 				}
 			}
 		}
 	}

 	/**
 	 * Removes the specified {@linkplain IModelSaveLifecycleListener model save lifecycle listener} from that registry.
 	 *
 	 * @param listener
 	 *            The {@linkplain IModelSaveLifecycleListener model save lifecycle listener} to remove from the list of
 	 *            registered ones.
 	 */
 	// FIXME Should we think about a solution allowing ONLY the removal of dynamically registered listeners?
 	public void removeListener(IModelSaveLifecycleListener listener) {
 		if (listener != null) {
 			Iterator<Map<String, Object>> iter1;
 			for (iter1 = modelSaveLifecycleListeners.values().iterator(); iter1.hasNext();) {
 				Map<String, Object> listenersForMetaModel = iter1.next();
 				Iterator<Object> iter2;
 				for (iter2 = listenersForMetaModel.values().iterator(); iter2.hasNext();) {
 					Object listenerForMetaModel = iter2.next();
 					if (listener.equals(listenerForMetaModel)) {
 						iter2.remove();
 					}
 				}
 				if (listenersForMetaModel.isEmpty()) {
 					iter1.remove();
 				}
 			}
 		}
 	}
 }
	/**
	* <copyright>
	*
	* Copyright (c) 2008-2012 See4sys, BMW Car IT and others.
	* All rights reserved. This program and the accompanying materials
	* are made available under the terms of the Eclipse Public License v2.0
	* which accompanies this distribution, and is available at
	* https://www.eclipse.org/org/documents/epl-2.0/EPL-2.0.html
	*
	* Contributors:
	* See4sys - Initial API and implementation
	* BMW Car IT - Lazy extension initialization
	*
	* </copyright>
	*/
	package org.eclipse.sphinx.emf.workspace.internal.saving;

	import java.util.Collection;
	import java.util.HashMap;
	import java.util.HashSet;
	import java.util.Iterator;
	import java.util.Map;
	import java.util.Set;

	import org.eclipse.core.runtime.IConfigurationElement;
	import org.eclipse.core.runtime.Platform;
	import org.eclipse.sphinx.emf.Activator;
	import org.eclipse.sphinx.emf.metamodel.IMetaModelDescriptor;
	import org.eclipse.sphinx.emf.metamodel.MetaModelDescriptorRegistry;
	import org.eclipse.sphinx.emf.workspace.saving.IModelSaveLifecycleListener;
	import org.eclipse.sphinx.platform.util.PlatformLogUtil;
	import org.osgi.framework.Bundle;

	/**
	* The singleton instance that is responsible for managing {@linkplain IModelSaveLifecycleListener model save lifecycle
	* listener}s that have been contributed to the platform <em>via</em> extension point
	* <tt>org.eclipse.sphinx.emf.workspace.modelSaveLifecycleListeners</tt>.
	* <p>
	* This registry mainly provides one method allowing to retrieve {@linkplain IModelSaveLifecycleListener listener}s
	* corresponding to one specified {@linkplain IMetaModelDescriptor meta-model descriptor}.
	*
	* @since 0.8.0
	*/
	public class ModelSaveLifecycleListenerRegistry {

	/**
	* The singleton instance of this registry.
	*/
	public static final ModelSaveLifecycleListenerRegistry INSTANCE = new ModelSaveLifecycleListenerRegistry();

	/**
	* Identifier of Model Save Lifecycle Listeners extension point.
	*/
	private static final String EXTP_MODEL_SAVLE_LIFECYCLE_LISTENERS = "org.eclipse.sphinx.emf.workspace.modelSaveLifecycleListeners"; //$NON-NLS-1$

	private static final String NODE_LISTENER = "listener"; //$NON-NLS-1$
	private static final String ATTR_ID = "id"; //$NON-NLS-1$
	private static final String ATTR_CLASS = "class"; //$NON-NLS-1$
	private static final String ATTR_OVERRIDE = "override"; //$NON-NLS-1$

	private static final String NODE_APPLICABLE_FOR = "applicableFor"; //$NON-NLS-1$
	private static final String ATTR_MMDESC_ID_PATTERN = "metaModelDescriptorIdPattern"; //$NON-NLS-1$

	/**
	* Flag to track lazy initialization.
	*/
	private boolean isInitialized = false;

	/**
	* The registered {@linkplain IModelSaveLifecycleListener model save lifecycle listener}s or
	* {@linkplain ListenerDescriptor listener descriptor}s
	*/
	private Map<IMetaModelDescriptor, Map<String, Object>> modelSaveLifecycleListeners = new HashMap<IMetaModelDescriptor, Map<String, Object>>();

	/**
	* The {@linkplain IModelSaveLifecycleListener model save lifecycle listener}s which are overridden by other ones.
	*/
	private Map<String, Set<IMetaModelDescriptor>> fOutstandingOverrides = new HashMap<String, Set<IMetaModelDescriptor>>();

	/**
	* The descriptor that is used to store the listener information prior to instantiation
	*/
	private class ListenerDescriptor {

	private String className;
	private String contributorPluginId;

	/**
	* @param className
	* @param contributorPluginId
	*/
	private ListenerDescriptor(String className, String contributorPluginId) {
	this.className = className;
	this.contributorPluginId = contributorPluginId;
	}

	/**
	* Construct and return the listener. This method might trigger plugin loading.
	*
	* @return the listener
	* @throws ClassNotFoundException
	* @throws IllegalAccessException
	* @throws InstantiationException
	*/
	private IModelSaveLifecycleListener getListener() throws ClassNotFoundException, InstantiationException, IllegalAccessException {
	Bundle bundle = Platform.getBundle(contributorPluginId);
	Class<?> factoryClz = bundle.loadClass(className);
	return (IModelSaveLifecycleListener) factoryClz.newInstance();
	}
	}

	/**
	* Private constructor for singleton pattern.
	*/
	private ModelSaveLifecycleListenerRegistry() {

	}

	/**
	* Reads contributions to the <em>Model Save Lifecycle Listeners</em> extension point.
	*/
	private void readContributedModelSaveLifecycleListeners() {
	for (IConfigurationElement cfgElement : Platform.getExtensionRegistry().getConfigurationElementsFor(EXTP_MODEL_SAVLE_LIFECYCLE_LISTENERS)) {
	try {
	if (NODE_LISTENER.equals(cfgElement.getName())) {
	String listenerId = cfgElement.getAttribute(ATTR_ID);
	String overriddenListenerId = cfgElement.getAttribute(ATTR_OVERRIDE);

	// Create a descriptor for the listener
	ListenerDescriptor descriptor = new ListenerDescriptor(cfgElement.getAttribute(ATTR_CLASS), cfgElement.getContributor().getName());

	// Register it upon meta-model descriptor is must be available for
	for (IConfigurationElement applicableFor : cfgElement.getChildren(NODE_APPLICABLE_FOR)) {
	String mmDescIdPattern = applicableFor.getAttribute(ATTR_MMDESC_ID_PATTERN);
	addListenerDescriptor(mmDescIdPattern, listenerId, descriptor, overriddenListenerId);
	}
	}
	} catch (Exception ex) {
	PlatformLogUtil.logAsError(Activator.getPlugin(), ex);
	}
	}

	// Remove overridden model save lifecycle listeners that couldn't be removed earlier
	for (String overriddenListenerId : fOutstandingOverrides.keySet()) {
	for (IMetaModelDescriptor mmDescriptor : fOutstandingOverrides.get(overriddenListenerId)) {
	Map<String, Object> listenersForMetaModel = modelSaveLifecycleListeners.get(mmDescriptor);
	if (listenersForMetaModel != null) {
	listenersForMetaModel.remove(overriddenListenerId);
	}
	}
	}
	fOutstandingOverrides.clear();
	}

	/**
	* Adds the specified {@linkplain ListenerDescriptor listener descriptor} to the map of registered listeners and
	* descriptors that have been contributed to the platform through
	* <tt>org.eclipse.sphinx.emf.workspace.modelSaveLifecycleListeners</tt> extension point.
	*
	* @param mmDescIdPattern
	* The {@linkplain IMetaModelDescriptor meta-model descriptor} identifier pattern allowing to retrieve
	* the meta-model descriptors the specified {@linkplain IModelSaveLifecycleListener model save lifecycle
	* listener} must be associated to. Should not be <code>null</code>.
	* @param listenerId
	* The identifier of the {@linkplain IModelSaveLifecycleListener model save lifecycle listener} to be
	* registered. Should not be null.
	* @param descriptor
	* The {@linkplain ListenerDescriptor listener descriptor} that must be registered on the
	* {@linkplain ModelSaveLifecycleListenerRegistry model save lifecycle listener registry} for the
	* {@linkplain IMetaModelDescriptor meta-model descriptor}s that match the specified
	* <code>mmDescIdPattern</code>. Should not be <code>null</code>.
	* @param overriddenListenerId
	* The identifier of some other {@linkplain IModelSaveLifecycleListener model save lifecycle listener} to
	* be overridden or <code>null</code> when no overriding is required.
	*/
	private void addListenerDescriptor(String mmDescIdPattern, String listenerId, ListenerDescriptor descriptor, String overriddenListenerId) {
	if (".*".equals(mmDescIdPattern) \|\| ".+".equals(mmDescIdPattern)) { //$NON-NLS-1$ //$NON-NLS-2$
	addListenerDescriptor(MetaModelDescriptorRegistry.ANY_MM, listenerId, descriptor, overriddenListenerId);
	return;
	}

	for (IMetaModelDescriptor mmDescriptor : MetaModelDescriptorRegistry.INSTANCE.getDescriptors(mmDescIdPattern)) {
	addListenerDescriptor(mmDescriptor, listenerId, descriptor, overriddenListenerId);
	}
	}

	/**
	* Adds the specified {@linkplain ListenerDescriptor listener descriptor} to the map of registered listeners and
	* descriptors that have been contributed to the platform through
	* <tt>org.eclipse.sphinx.emf.workspace.modelSaveLifecycleListeners</tt> extension point.
	*
	* @param mmDescriptor
	* The {@linkplain IMetaModelDescriptor meta-model descriptor} the specified
	* {@linkplain IModelSaveLifecycleListener model save lifecycle listener} must be associated to. Should
	* not be <code>null</code>.
	* @param listenerId
	* The identifier of the {@linkplain IModelSaveLifecycleListener model save lifecycle listener} to be
	* registered. Shall not be null.
	* @param descriptor
	* The {@linkplain ListenerDescriptor listener descriptor} that must be registered on the
	* {@linkplain ModelSaveLifecycleListenerRegistry model save lifecycle listener registry} for the
	* {@linkplain IMetaModelDescriptor meta-model descriptor}s that match the specified
	* <code>mmDescIdPattern</code>. Should not be <code>null</code>.
	* @param overriddenListenerId
	* The identifier of some other {@linkplain IModelSaveLifecycleListener model save lifecycle listener} to
	* be overridden or <code>null</code> when no overriding is required.
	*/
	private void addListenerDescriptor(IMetaModelDescriptor mmDescriptor, String listenerId, ListenerDescriptor descriptor,
	String overriddenListenerId) {
	if (mmDescriptor != null && descriptor != null) {
	// Register model save lifecycle listener for given meta-model descriptor
	Map<String, Object> listenersForMetaModel = modelSaveLifecycleListeners.get(mmDescriptor);
	if (listenersForMetaModel == null) {
	listenersForMetaModel = new HashMap<String, Object>();
	modelSaveLifecycleListeners.put(mmDescriptor, listenersForMetaModel);
	}
	listenersForMetaModel.put(listenerId, descriptor);

	// Manage overridden model save lifecycle listener, if any
	if (overriddenListenerId != null) {
	// Remove overridden model save lifecycle listener; remember it for being removed later if it is not
	// present yet
	if (listenersForMetaModel.remove(overriddenListenerId) == null) {
	Set<IMetaModelDescriptor> overridesForListener = fOutstandingOverrides.get(overriddenListenerId);
	if (overridesForListener == null) {
	overridesForListener = new HashSet<IMetaModelDescriptor>();
	fOutstandingOverrides.put(overriddenListenerId, overridesForListener);
	}
	overridesForListener.add(mmDescriptor);
	}
	}
	}
	}

	/**
	* @param mmDescriptor
	* The {@linkplain IMetaModelDescriptor meta-model descriptor} for which matching
	* {@linkplain IModelSaveLifecycleListener model save lifecycle listener}s must be returned.
	* @return The {@linkplain IModelSaveLifecycleListener model save lifecycle listener}s that have been contributed to
	* the platform <em>via</em> <tt>modelSaveLifecycleListeners</tt> extension point and that match the
	* specified {@linkplain IMetaModelDescriptor meta-model descriptor}.
	*/
	public Collection<IModelSaveLifecycleListener> getListeners(IMetaModelDescriptor mmDescriptor) {
	synchronized (this) {
	if (isInitialized == false) {
	readContributedModelSaveLifecycleListeners();
	isInitialized = true;
	}
	}

	// Retrieve model save lifecycle listeners registered upon specified meta-model descriptor or one
	// of its super
	// descriptors
	Set<IModelSaveLifecycleListener> listeners = new HashSet<IModelSaveLifecycleListener>();
	for (IMetaModelDescriptor registeredMMDescriptor : modelSaveLifecycleListeners.keySet()) {
	if (registeredMMDescriptor.getClass().isInstance(mmDescriptor)) {
	Map<String, Object> listenersForMetaModel = modelSaveLifecycleListeners.get(registeredMMDescriptor);
	listeners.addAll(getListeners(listenersForMetaModel));
	}
	}

	// Retrieve model save lifecycle listeners registered upon static any meta-model descriptor
	Map<String, Object> listenersForAnyMetaModel = modelSaveLifecycleListeners.get(MetaModelDescriptorRegistry.ANY_MM);
	if (listenersForAnyMetaModel != null) {
	listeners.addAll(getListeners(listenersForAnyMetaModel));
	}
	return listeners;
	}

	/**
	* Returns a set of {@linkplain IModelSaveLifecycleListener model save lifecycle listeners} that are contained or
	* described by the entries in given <code>listenersOrDescriptors</code> map.
	* <p>
	* Depending on the type of the listener object contained by each map entry one of the following actions is taken:
	* <ul>
	* <li>Instances of {@linkplain IModelSaveLifecycleListener model save lifecycle listener}s are directly added to
	* the resulting listener set.</li>
	* <li>Instances of {@linkplain ListenerDescriptor model save lifecycle listener descriptor}s are used to create the
	* actual {@linkplain IModelSaveLifecycleListener model save lifecycle listener}s and add those to the resulting
	* listener set. In addition the formers are replaced by the latters in given <code>listenersOrDescriptors</code>
	* map.</li>
	* <li>Instances of anything else are logged as errors and removed from given <code>listenersOrDescriptors</code>
	* map.
	* </p>
	*
	* @param listenersOrDescriptors
	* The map with {@linkplain IModelSaveLifecycleListener model save lifecycle listener}s or
	* {@linkplain ListenerDescriptor model save lifecycle listener descriptor}s and their respective
	* identifiers to be processed.
	* @return A set of {@linkplain IModelSaveLifecycleListener model save lifecycle listener}s that are contained or
	* described by the entries in given <code>listenersOrDescriptors </code> map.
	*/
	private Set<IModelSaveLifecycleListener> getListeners(Map<String, Object> listenersOrDescriptors) {
	Set<IModelSaveLifecycleListener> listeners = new HashSet<IModelSaveLifecycleListener>();
	for (Iterator<String> iter = listenersOrDescriptors.keySet().iterator(); iter.hasNext();) {
	String listenerId = iter.next();
	Object listenerObject = listenersOrDescriptors.get(listenerId);
	if (listenerObject instanceof IModelSaveLifecycleListener) {
	// Add existing listener
	listeners.add((IModelSaveLifecycleListener) listenerObject);
	} else if (listenerObject instanceof ListenerDescriptor) {
	// Create the listener
	try {
	IModelSaveLifecycleListener listener = ((ListenerDescriptor) listenerObject).getListener();
	listenersOrDescriptors.put(listenerId, listener);
	listeners.add(listener);
	} catch (Exception ex) {
	PlatformLogUtil.logAsError(Activator.getPlugin(), ex);

	// Discard bad descriptor so as to avoid repeated runs into same problem
	iter.remove();
	}
	} else {
	// Should not happen...
	PlatformLogUtil.logAsError(Activator.getPlugin(), "Invalid model save lifecycle listener object: " //$NON-NLS-1$
	+ listenerObject.getClass().getName());

	// Discard bad descriptor so as to avoid repeated runs into same problem
	iter.remove();
	}
	}
	return listeners;
	}

	/**
	* Adds the specified {@linkplain IModelSaveLifecycleListener model save lifecycle listener} to the map of
	* registered listeners that have been contributed to the platform through
	* <tt>org.eclipse.sphinx.emf.modelSaveLifecycleListeners</tt> extension point.
	*
	* @param mmDescIdPattern
	* The {@linkplain IMetaModelDescriptor meta-model descriptor} identifier pattern allowing to retrieve
	* the meta-model descriptors the specified {@linkplain IModelSaveLifecycleListener model save lifecycle
	* listener} must be associated to. Should not be <code>null</code>.
	* @param listenerId
	* The identifier of the {@linkplain IModelSaveLifecycleListener model save lifecycle listener} to be
	* registered. If <code>null</code> the {@linkplain IModelSaveLifecycleListener model save lifecycle
	* listener} 's identifier will be automatically computed based the result of
	* {@linkplain IModelSaveLifecycleListener#toString() toString()}.
	* @param listener
	* The {@linkplain IModelSaveLifecycleListener model save lifecycle listener} that must be registered on
	* the {@linkplain ModelSaveLifecycleListenerRegistry model save lifecycle listener registry} for the
	* {@linkplain IMetaModelDescriptor meta-model descriptor}s that match the specified
	* <code>mmDescIdPattern</code>. Should not be <code>null</code>.
	* @param overriddenListenerId
	* The identifier of some other {@linkplain IModelSaveLifecycleListener model save lifecycle listener} to
	* be overridden or <code>null</code> when no overriding is required.
	*/
	public void addListener(String mmDescIdPattern, String listenerId, IModelSaveLifecycleListener listener, String overriddenListenerId) {
	/*
	* !! Important Note !! If given meta-model descriptor id pattern matches anything register specified model save
	* lifecycle listener only with static any meta-model descriptor rather than with all meta-model matching
	* descriptors. This makes sure that the listener will not only be invoked for all static (contributed)
	* meta-model descriptors but also for all dynamic meta-model descriptors including those which are created
	* subsequently, i.e. AFTER the installation of specified listener.
	*/
	if (".*".equals(mmDescIdPattern) \|\| ".+".equals(mmDescIdPattern)) { //$NON-NLS-1$ //$NON-NLS-2$
	addListener(MetaModelDescriptorRegistry.ANY_MM, listenerId, listener, overriddenListenerId);
	return;
	}

	for (IMetaModelDescriptor mmDescriptor : MetaModelDescriptorRegistry.INSTANCE.getDescriptors(mmDescIdPattern)) {
	addListener(mmDescriptor, listenerId, listener, overriddenListenerId);
	}
	}

	/**
	* Adds the specified {@linkplain IModelSaveLifecycleListener model save lifecycle listener} to the map of
	* registered listeners that have been contributed to the platform through
	* <tt>org.eclipse.sphinx.emf.modelSaveLifecycleListeners</tt> extension point.
	*
	* @param mmDescriptor
	* The {@linkplain IMetaModelDescriptor meta-model descriptor} the specified
	* {@linkplain IModelSaveLifecycleListener model save lifecycle listener} must be associated to. Should
	* not be <code>null</code>.
	* @param listenerId
	* The identifier of the {@linkplain IModelSaveLifecycleListener model save lifecycle listener} to be
	* registered. If <code>null</code> the {@linkplain IModelSaveLifecycleListener model save lifecycle
	* listener} 's identifier will be automatically computed based the result of
	* {@linkplain IModelSaveLifecycleListener#toString() toString()}.
	* @param listener
	* The {@linkplain IModelSaveLifecycleListener model save lifecycle listener} that must be registered on
	* the {@linkplain ModelSaveLifecycleListenerRegistry model save lifecycle listener registry} for the
	* {@linkplain IMetaModelDescriptor meta-model descriptor}s that match the specified
	* <code>mmDescIdPattern</code>. Should not be <code>null</code>.
	* @param overriddenListenerId
	* The identifier of some other {@linkplain IModelSaveLifecycleListener model save lifecycle listener} to
	* be overridden or <code>null</code> when no overriding is required.
	*/
	public void addListener(IMetaModelDescriptor mmDescriptor, String listenerId, IModelSaveLifecycleListener listener, String overriddenListenerId) {
	if (mmDescriptor != null && listener != null) {
	// Register model save lifecycle listener for given meta-model descriptor
	Map<String, Object> listenersForMetaModel = modelSaveLifecycleListeners.get(mmDescriptor);
	if (listenersForMetaModel == null) {
	listenersForMetaModel = new HashMap<String, Object>();
	modelSaveLifecycleListeners.put(mmDescriptor, listenersForMetaModel);
	}
	listenersForMetaModel.put(listenerId != null ? listenerId : listener.toString(), listener);

	// Manage overridden model save lifecycle listener, if any
	if (overriddenListenerId != null) {
	// Remove overridden model save lifecycle listener; remember it for being removed later
	// if it is not
	// present yet
	if (listenersForMetaModel.remove(overriddenListenerId) == null) {
	Set<IMetaModelDescriptor> overridesForListener = fOutstandingOverrides.get(overriddenListenerId);
	if (overridesForListener == null) {
	overridesForListener = new HashSet<IMetaModelDescriptor>();
	fOutstandingOverrides.put(overriddenListenerId, overridesForListener);
	}
	overridesForListener.add(mmDescriptor);
	}
	}
	}
	}

	/**
	* Removes the specified {@linkplain IModelSaveLifecycleListener model save lifecycle listener} from that registry.
	*
	* @param listener
	* The {@linkplain IModelSaveLifecycleListener model save lifecycle listener} to remove from the list of
	* registered ones.
	*/
	// FIXME Should we think about a solution allowing ONLY the removal of dynamically registered listeners?
	public void removeListener(IModelSaveLifecycleListener listener) {
	if (listener != null) {
	Iterator<Map<String, Object>> iter1;
	for (iter1 = modelSaveLifecycleListeners.values().iterator(); iter1.hasNext();) {
	Map<String, Object> listenersForMetaModel = iter1.next();
	Iterator<Object> iter2;
	for (iter2 = listenersForMetaModel.values().iterator(); iter2.hasNext();) {
	Object listenerForMetaModel = iter2.next();
	if (listener.equals(listenerForMetaModel)) {
	iter2.remove();
	}
	}
	if (listenersForMetaModel.isEmpty()) {
	iter1.remove();
	}
	}
	}
	}
	}