bundles/org.eclipse.wst.sse.ui/src/org/eclipse/wst/sse/ui/internal/comment/CommentingStrategyRegistry.java - sourceediting/webtools.sourceediting - Git at Google

 /*******************************************************************************
  * Copyright (c) 2010 IBM Corporation and others.
  * 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:
  *     IBM Corporation - initial API and implementation
  *******************************************************************************/
 package org.eclipse.wst.sse.ui.internal.comment;

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

 import org.eclipse.core.runtime.CoreException;
 import org.eclipse.core.runtime.IConfigurationElement;
 import org.eclipse.core.runtime.IExtensionRegistry;
 import org.eclipse.core.runtime.IStatus;
 import org.eclipse.core.runtime.InvalidRegistryObjectException;
 import org.eclipse.core.runtime.Platform;
 import org.eclipse.core.runtime.Status;
 import org.eclipse.core.runtime.content.IContentType;
 import org.eclipse.jface.text.ITypedRegion;
 import org.eclipse.wst.sse.ui.internal.Logger;
 import org.eclipse.wst.sse.ui.internal.SSEUIPlugin;

 /**
  * <p>The registry of {@link CommentingStrategy}s defined by the <code>org.eclipse.wst.sse.ui.commentinStrategy</code>
  * extension point.</p>
  */
 public class CommentingStrategyRegistry {
 	/** The extension schema name of the extension point */
 	private static final String EXTENSION_POINT = "commentingStrategy"; //$NON-NLS-1$

 	/** The extension schema name of proposal block comment child elements. */
 	private static final String ELEM_PROPOSAL_BLOCK_COMMENTING_STRATEGY = "blockCommentingStrategy"; //$NON-NLS-1$

 	/** The extension schema name of proposal line comment child elements. */
 	private static final String ELEM_PROPOSAL_LINE_COMMENTING_STRATEGY = "lineCommentingStrategy"; //$NON-NLS-1$

 	/** The extension schema name of the content type child elements. */
 	private static final String ELEM_CONTENT_TYPE = "contentType"; //$NON-NLS-1$

 	/** The extension schema name of the required partition types child elements */
 	private static final String ELEM_REQUIRED_PARTITION_TYPES= "requiredPartitionTypes"; //$NON-NLS-1$

 	/** The extension schema name of the allowable partition types child elements */
 	private static final String ELEM_ALLOWABLE_PARTITION_TYPES= "allowablePartitionTypes"; //$NON-NLS-1$

 	/** The extension schema name of partition type child elements */
 	private static final String ELEM_PARTITION_TYPE= "partitionType"; //$NON-NLS-1$

 	/** The extension schema name of the prefix attribute */
 	private static final String ATTR_PREFIX = "prefix"; //$NON-NLS-1$

 	/** The extension schema name of the suffix attribute */
 	private static final String ATTR_SUFFIX = "suffix"; //$NON-NLS-1$

 	/** The extension schema name of the associatedCommentPartitionTypeID attribute */
 	private static final String ATTR_ASSOCIATED_COMMENT_PARTITION_TPYPE_ID = "associatedCommentPartitionTypeID"; //$NON-NLS-1$

 	/** The extension schema name of the anyPartitionType attribute */
 	private static final String ATTR_ANY_PARTITION_TYPE = "anyPartitionType";  //$NON-NLS-1$

 	/** The extension schema name for ID attribute */
 	private static final String ATTR_ID= "id"; //$NON-NLS-1$

 	/** the singleton instance of the registry */
 	private static CommentingStrategyRegistry fSingleton = null;

 	/** <code>true</code> if this registry has been loaded. */
 	private boolean fLoaded;

 	/**
 	 * <p>Registry of content type IDs to {@link BlockCommentingStrategy}s</p>
 	 *
 	 * <code>{@link Map}&lt{@link String}, {@link List}&lt{@link BlockContentType}&gt&gt</code>
 	 * <ul>
 	 * <li><b>key:</b> content type ID</li>
 	 * <li><b>value:</b> {@link List} of associated {@link BlockContentType}s</li>
 	 * <ul>
 	 */
 	private Map fBlockCommentTypes;

 	/**
 	 * <p>Registry of content type IDs to {@link LineCommentingStrategy}s</p>
 	 *
 	 * <code>{@link Map}&lt{@link String}, {@link List}&lt{@link LineContentType}&gt&gt</code>
 	 * <ul>
 	 * <li><b>key:</b> content type ID</li>
 	 * <li><b>value:</b> {@link List} of associated {@link LineContentType}s</li>
 	 * <ul>
 	 */
 	private Map fLineCommentTypes;

 	/**
 	 * @return the single instance of the {@link CommentingStrategyRegistry}
 	 */
 	public static synchronized CommentingStrategyRegistry getDefault() {
 		if(fSingleton == null) {
 			fSingleton = new CommentingStrategyRegistry();
 		}

 		return fSingleton;
 	}

 	/**
 	 * Singleton constructor for the registry
 	 */
 	private CommentingStrategyRegistry() {
 		this.fLoaded = false;
 		this.fBlockCommentTypes = new HashMap();
 		this.fLineCommentTypes = new HashMap();
 	}

 	/**
 	 * @param contentTypeID get only {@link BlockCommentingStrategy}s associated with this content type
 	 * @param regions get only {@link BlockCommentingStrategy}s associated with these types of regions
 	 * @return all the {@link BlockCommentingStrategy}s associated with the given content type and regions
 	 */
 	public CommentingStrategy getBlockCommentingStrategy(String contentTypeID, ITypedRegion[] regions) {
 		return getCommentingStrategy(contentTypeID, regions, this.fBlockCommentTypes);
 	}

 	/**
 	 * @param contentTypeID get only {@link LineCommentingStrategy}s associated with this content type
 	 * @param regions get only {@link LineCommentingStrategy}s associated with these types of regions
 	 * @return all the {@link LineCommentingStrategy}s associated with the given content type and regions
 	 */
 	public CommentingStrategy getLineCommentingStrategy(String contentTypeID, ITypedRegion[] regions) {
 		return getCommentingStrategy(contentTypeID, regions, this.fLineCommentTypes);
 	}

 	/**
 	 * <p>get all the {@link CommentingStrategy}s associated with the given content type and regions
 	 * from the given registry</p>
 	 *
 	 * @param contentTypeID  get only {@link CommentingStrategy}s associated with this content type
 	 * @param regions get only {@link CommentingStrategy}s associated with these types of regions
 	 * @param registry get the {@link CommentingStrategy}s from this registry
 	 * @return all the {@link CommentingStrategy}s associated with the given content type and regions
 	 * from the given registry
 	 */
 	private CommentingStrategy getCommentingStrategy(String contentTypeID, ITypedRegion[] regions, Map registry) {
 		ensureExtensionPointRead();

 		CommentingStrategy match = null;
 		IContentType contentType = Platform.getContentTypeManager().getContentType(contentTypeID);

 		/* get all the commenting strategies for the given content type id,
 		 * including those registered for parent content types
 		 */
 		List possibleCommentingStrategies = new ArrayList();
 		while(contentType != null) {
 			List contentTypeCommentingStrategies = (List)registry.get(contentType.getId());
 			if(contentTypeCommentingStrategies != null && contentTypeCommentingStrategies.size() > 0) {
 				possibleCommentingStrategies.addAll(contentTypeCommentingStrategies);
 			}
 			contentType = contentType.getBaseType();
 		}

 		/* find the commenting strategy applicable for the given regions,
 		 * because strategies were added starting from the most specific
 		 * content type first, the most specific strategy will always be chosen
 		 */
 		for(int i = 0; i < possibleCommentingStrategies.size() && match == null; ++i) {
 			CommentingStrategy commentType = (CommentingStrategy)possibleCommentingStrategies.get(i);
 			if(commentType.isApplicableFor(regions)) {
 				match = commentType;
 			}
 		}

 		return match;
 	}

 	/**
 	 * <p>Ensures that the extensions are read and this registry is built</p>
 	 */
 	private void ensureExtensionPointRead() {
 		if(!fLoaded) {
 			load();
 			fLoaded = true;
 		}
 	}

 	/**
 	 * <p>Load the extension points into the registry</p>
 	 */
 	private void load() {
 		IExtensionRegistry extensionRegistry = Platform.getExtensionRegistry();
 		List extensionElements = new ArrayList(Arrays.asList(extensionRegistry.getConfigurationElementsFor(SSEUIPlugin.ID, EXTENSION_POINT)));

 		//for each extension
 		for (Iterator iter= extensionElements.iterator(); iter.hasNext();) {
 			IConfigurationElement element = (IConfigurationElement) iter.next();
 			try {
 				CommentingStrategy newCommentingStrategy = null;
 				Map commentingStrategyRegistry = null;
 				//either a block or line commenting strategy
 				if(element.getName().equals(ELEM_PROPOSAL_BLOCK_COMMENTING_STRATEGY)) {
 					String prefix = element.getAttribute(ATTR_PREFIX);
 					checkExtensionAttributeNotNull(prefix, ATTR_PREFIX, element);

 					String suffix = element.getAttribute(ATTR_SUFFIX);
 					checkExtensionAttributeNotNull(suffix, ATTR_SUFFIX, element);

 					if(prefix != null && suffix != null) {
 						newCommentingStrategy = new BlockCommentingStrategy(prefix, suffix);
 						commentingStrategyRegistry = this.fBlockCommentTypes;
 					}
 				} else if(element.getName().equals(ELEM_PROPOSAL_LINE_COMMENTING_STRATEGY)) {
 					String prefix = element.getAttribute(ATTR_PREFIX);
 					checkExtensionAttributeNotNull(prefix, ATTR_PREFIX, element);

 					if(prefix != null) {
 						newCommentingStrategy = new LineCommentingStrategy(prefix);
 						commentingStrategyRegistry = this.fLineCommentTypes;
 					}
 				}

 				//add the new strategy to the registry
 				if(commentingStrategyRegistry != null && newCommentingStrategy != null) {
 					addCommentingStrategyToRegistry(element, commentingStrategyRegistry, newCommentingStrategy);
 				} else {
 					Logger.log(Logger.WARNING, "Invalid CommentingStrategy extension: " + element); //$NON-NLS-1$
 				}
 			} catch (CoreException e) {
 				Logger.logException(e);
 			} catch (InvalidRegistryObjectException x) {
 				/* Element is not valid any longer as the contributing plug-in was unloaded or for
 				 * some other reason. Do not include the extension in the list and log it
 				 */
 				String message = "The extension ''" + element.toString() + "'' is invalid."; //$NON-NLS-1$ //$NON-NLS-2$
 				IStatus status= new Status(IStatus.WARNING, SSEUIPlugin.ID, IStatus.WARNING, message, x);
 				Logger.log(status);
 			}
 		}
 	}

 	/**
 	 * <p>Checks that the given attribute value is not <code>null</code>.</p>
 	 *
 	 * @param value the object to check if not null
 	 * @param attribute the attribute
 	 *
 	 * @throws InvalidRegistryObjectException if the registry element is no longer valid
 	 * @throws CoreException if <code>value</code> is <code>null</code>
 	 */
 	private static void checkExtensionAttributeNotNull(Object value, String attribute,
 			IConfigurationElement element) throws InvalidRegistryObjectException, CoreException {

 		if (value == null) {
 			String message = "The extension \"" + element.getDeclaringExtension().getUniqueIdentifier() + //$NON-NLS-1$
 				"\" from plug-in \"" + element.getContributor().getName() + //$NON-NLS-1$
 				"\" did not specify a value for the required \"" + attribute + //$NON-NLS-1$
 				"\" attribute for the element \"" + element.getName() + "\". Disabling the extension."; //$NON-NLS-1$ //$NON-NLS-2$
 			IStatus status= new Status(IStatus.WARNING, SSEUIPlugin.ID, IStatus.OK, message, null);
 			throw new CoreException(status);
 		}
 	}

 	/**
 	 * <p>Using the content type element children of the given element add a copy of the given
 	 * base commenting strategy to the given registry</p>
 	 *
 	 * @param element a {@link IConfigurationElement} with contentType element children
 	 * @param commentingStrategyRegistry {@link Map} of content type ids to {@link CommentingStrategy}s to register
 	 * the given {@link CommentingStrategy} with based on the <code>element</code>
 	 * @param baseCommentingStrategy {@link CommentingStrategy} that will be cloned and configured for each
 	 * content type in the given <code>element</code>
 	 */
 	private static void addCommentingStrategyToRegistry(IConfigurationElement element,
 			Map commentingStrategyRegistry, CommentingStrategy baseCommentingStrategy) {

 		//get all the content type elements
 		IConfigurationElement[] contentTypeElements = element.getChildren(ELEM_CONTENT_TYPE);
 		if(contentTypeElements.length > 0) {
 			for(int contentTypeIndex = 0; contentTypeIndex < contentTypeElements.length; ++contentTypeIndex) {
 				try {
 					String contentTypeID = contentTypeElements[contentTypeIndex].getAttribute(ATTR_ID);
 					checkExtensionAttributeNotNull(contentTypeID, ATTR_ID, contentTypeElements[contentTypeIndex]);

 					List commentTypes = (List)commentingStrategyRegistry.get(contentTypeID);
 					if(commentTypes == null) {
 						commentTypes = new ArrayList();
 						commentingStrategyRegistry.put(contentTypeID, commentTypes);
 					}

 					//this element is required
 					List allowablePartitionTypeIDs = new ArrayList();
 					IConfigurationElement[] allowablePartitionTypes =
 						contentTypeElements[contentTypeIndex].getChildren(ELEM_ALLOWABLE_PARTITION_TYPES);
 					boolean anyPartitionType = false;
 					//determine anyPartitionType attribute value
 					String anyPartitionTypeValue = allowablePartitionTypes[0].getAttribute(ATTR_ANY_PARTITION_TYPE);
 					if(anyPartitionTypeValue != null) {
 						anyPartitionType = Boolean.valueOf(anyPartitionTypeValue).booleanValue();
 					}

 					//get the optional partition types
 					allowablePartitionTypes = allowablePartitionTypes[0].getChildren(ELEM_PARTITION_TYPE);
 					if(allowablePartitionTypes.length > 0) {
 						for (int partitionTypeIndex = 0; partitionTypeIndex < allowablePartitionTypes.length; ++partitionTypeIndex) {
 							String partitionTypeID = allowablePartitionTypes[partitionTypeIndex].getAttribute(ATTR_ID);
 							checkExtensionAttributeNotNull(partitionTypeID, ATTR_ID, allowablePartitionTypes[partitionTypeIndex]);

 							allowablePartitionTypeIDs.add(partitionTypeID);
 						}
 					}

 					//this element is optional
 					List requiredPartitionTypeIDs = new ArrayList();
 					IConfigurationElement[] requiredPartitionTypes =
 						contentTypeElements[contentTypeIndex].getChildren(ELEM_REQUIRED_PARTITION_TYPES);
 					if(requiredPartitionTypes.length > 0) {
 						//get the required partition types
 						requiredPartitionTypes = requiredPartitionTypes[0].getChildren(ELEM_PARTITION_TYPE);
 						if(requiredPartitionTypes.length > 0) {
 							for (int partitionTypeIndex = 0; partitionTypeIndex < requiredPartitionTypes.length; ++partitionTypeIndex) {
 								String partitionTypeID = requiredPartitionTypes[partitionTypeIndex].getAttribute(ATTR_ID);
 								checkExtensionAttributeNotNull(partitionTypeID, ATTR_ID, requiredPartitionTypes[partitionTypeIndex]);

 								requiredPartitionTypeIDs.add(partitionTypeID);
 							}
 						}
 					}

 					//get the optional associated comment partition type ID
 					String associatedCommentPartitionTypeID =
 						contentTypeElements[contentTypeIndex].getAttribute(ATTR_ASSOCIATED_COMMENT_PARTITION_TPYPE_ID);

 					//register the strategy
 					CommentingStrategy newCommentingStrategy = (CommentingStrategy)baseCommentingStrategy.clone();
 					newCommentingStrategy.setPartitionInformation(allowablePartitionTypeIDs, anyPartitionType,
 							requiredPartitionTypeIDs, associatedCommentPartitionTypeID);
 					commentTypes.add(newCommentingStrategy);
 				} catch(CoreException e) {
 					Logger.logException(e);
 				}
 			}
 		} else {
 			Logger.log(Logger.WARNING, "The commmenting strategy element: " + element +//$NON-NLS-1$
 					" does not contain any required " + ELEM_CONTENT_TYPE + "s"); //$NON-NLS-1$ //$NON-NLS-2$
 		}
 	}
 }
	/*******************************************************************************
	* Copyright (c) 2010 IBM Corporation and others.
	* 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:
	* IBM Corporation - initial API and implementation
	*******************************************************************************/
	package org.eclipse.wst.sse.ui.internal.comment;

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

	import org.eclipse.core.runtime.CoreException;
	import org.eclipse.core.runtime.IConfigurationElement;
	import org.eclipse.core.runtime.IExtensionRegistry;
	import org.eclipse.core.runtime.IStatus;
	import org.eclipse.core.runtime.InvalidRegistryObjectException;
	import org.eclipse.core.runtime.Platform;
	import org.eclipse.core.runtime.Status;
	import org.eclipse.core.runtime.content.IContentType;
	import org.eclipse.jface.text.ITypedRegion;
	import org.eclipse.wst.sse.ui.internal.Logger;
	import org.eclipse.wst.sse.ui.internal.SSEUIPlugin;

	/**
	* <p>The registry of {@link CommentingStrategy}s defined by the <code>org.eclipse.wst.sse.ui.commentinStrategy</code>
	* extension point.</p>
	*/
	public class CommentingStrategyRegistry {
	/** The extension schema name of the extension point */
	private static final String EXTENSION_POINT = "commentingStrategy"; //$NON-NLS-1$

	/** The extension schema name of proposal block comment child elements. */
	private static final String ELEM_PROPOSAL_BLOCK_COMMENTING_STRATEGY = "blockCommentingStrategy"; //$NON-NLS-1$

	/** The extension schema name of proposal line comment child elements. */
	private static final String ELEM_PROPOSAL_LINE_COMMENTING_STRATEGY = "lineCommentingStrategy"; //$NON-NLS-1$

	/** The extension schema name of the content type child elements. */
	private static final String ELEM_CONTENT_TYPE = "contentType"; //$NON-NLS-1$

	/** The extension schema name of the required partition types child elements */
	private static final String ELEM_REQUIRED_PARTITION_TYPES= "requiredPartitionTypes"; //$NON-NLS-1$

	/** The extension schema name of the allowable partition types child elements */
	private static final String ELEM_ALLOWABLE_PARTITION_TYPES= "allowablePartitionTypes"; //$NON-NLS-1$

	/** The extension schema name of partition type child elements */
	private static final String ELEM_PARTITION_TYPE= "partitionType"; //$NON-NLS-1$

	/** The extension schema name of the prefix attribute */
	private static final String ATTR_PREFIX = "prefix"; //$NON-NLS-1$

	/** The extension schema name of the suffix attribute */
	private static final String ATTR_SUFFIX = "suffix"; //$NON-NLS-1$

	/** The extension schema name of the associatedCommentPartitionTypeID attribute */
	private static final String ATTR_ASSOCIATED_COMMENT_PARTITION_TPYPE_ID = "associatedCommentPartitionTypeID"; //$NON-NLS-1$

	/** The extension schema name of the anyPartitionType attribute */
	private static final String ATTR_ANY_PARTITION_TYPE = "anyPartitionType"; //$NON-NLS-1$

	/** The extension schema name for ID attribute */
	private static final String ATTR_ID= "id"; //$NON-NLS-1$

	/** the singleton instance of the registry */
	private static CommentingStrategyRegistry fSingleton = null;

	/** <code>true</code> if this registry has been loaded. */
	private boolean fLoaded;

	/**
	* <p>Registry of content type IDs to {@link BlockCommentingStrategy}s</p>
	*
	* <code>{@link Map}&lt{@link String}, {@link List}&lt{@link BlockContentType}&gt&gt</code>
	* <ul>
	* <li><b>key:</b> content type ID</li>
	* <li><b>value:</b> {@link List} of associated {@link BlockContentType}s</li>
	* <ul>
	*/
	private Map fBlockCommentTypes;

	/**
	* <p>Registry of content type IDs to {@link LineCommentingStrategy}s</p>
	*
	* <code>{@link Map}&lt{@link String}, {@link List}&lt{@link LineContentType}&gt&gt</code>
	* <ul>
	* <li><b>key:</b> content type ID</li>
	* <li><b>value:</b> {@link List} of associated {@link LineContentType}s</li>
	* <ul>
	*/
	private Map fLineCommentTypes;

	/**
	* @return the single instance of the {@link CommentingStrategyRegistry}
	*/
	public static synchronized CommentingStrategyRegistry getDefault() {
	if(fSingleton == null) {
	fSingleton = new CommentingStrategyRegistry();
	}

	return fSingleton;
	}

	/**
	* Singleton constructor for the registry
	*/
	private CommentingStrategyRegistry() {
	this.fLoaded = false;
	this.fBlockCommentTypes = new HashMap();
	this.fLineCommentTypes = new HashMap();
	}

	/**
	* @param contentTypeID get only {@link BlockCommentingStrategy}s associated with this content type
	* @param regions get only {@link BlockCommentingStrategy}s associated with these types of regions
	* @return all the {@link BlockCommentingStrategy}s associated with the given content type and regions
	*/
	public CommentingStrategy getBlockCommentingStrategy(String contentTypeID, ITypedRegion[] regions) {
	return getCommentingStrategy(contentTypeID, regions, this.fBlockCommentTypes);
	}

	/**
	* @param contentTypeID get only {@link LineCommentingStrategy}s associated with this content type
	* @param regions get only {@link LineCommentingStrategy}s associated with these types of regions
	* @return all the {@link LineCommentingStrategy}s associated with the given content type and regions
	*/
	public CommentingStrategy getLineCommentingStrategy(String contentTypeID, ITypedRegion[] regions) {
	return getCommentingStrategy(contentTypeID, regions, this.fLineCommentTypes);
	}

	/**
	* <p>get all the {@link CommentingStrategy}s associated with the given content type and regions
	* from the given registry</p>
	*
	* @param contentTypeID get only {@link CommentingStrategy}s associated with this content type
	* @param regions get only {@link CommentingStrategy}s associated with these types of regions
	* @param registry get the {@link CommentingStrategy}s from this registry
	* @return all the {@link CommentingStrategy}s associated with the given content type and regions
	* from the given registry
	*/
	private CommentingStrategy getCommentingStrategy(String contentTypeID, ITypedRegion[] regions, Map registry) {
	ensureExtensionPointRead();

	CommentingStrategy match = null;
	IContentType contentType = Platform.getContentTypeManager().getContentType(contentTypeID);

	/* get all the commenting strategies for the given content type id,
	* including those registered for parent content types
	*/
	List possibleCommentingStrategies = new ArrayList();
	while(contentType != null) {
	List contentTypeCommentingStrategies = (List)registry.get(contentType.getId());
	if(contentTypeCommentingStrategies != null && contentTypeCommentingStrategies.size() > 0) {
	possibleCommentingStrategies.addAll(contentTypeCommentingStrategies);
	}
	contentType = contentType.getBaseType();
	}

	/* find the commenting strategy applicable for the given regions,
	* because strategies were added starting from the most specific
	* content type first, the most specific strategy will always be chosen
	*/
	for(int i = 0; i < possibleCommentingStrategies.size() && match == null; ++i) {
	CommentingStrategy commentType = (CommentingStrategy)possibleCommentingStrategies.get(i);
	if(commentType.isApplicableFor(regions)) {
	match = commentType;
	}
	}

	return match;
	}

	/**
	* <p>Ensures that the extensions are read and this registry is built</p>
	*/
	private void ensureExtensionPointRead() {
	if(!fLoaded) {
	load();
	fLoaded = true;
	}
	}

	/**
	* <p>Load the extension points into the registry</p>
	*/
	private void load() {
	IExtensionRegistry extensionRegistry = Platform.getExtensionRegistry();
	List extensionElements = new ArrayList(Arrays.asList(extensionRegistry.getConfigurationElementsFor(SSEUIPlugin.ID, EXTENSION_POINT)));

	//for each extension
	for (Iterator iter= extensionElements.iterator(); iter.hasNext();) {
	IConfigurationElement element = (IConfigurationElement) iter.next();
	try {
	CommentingStrategy newCommentingStrategy = null;
	Map commentingStrategyRegistry = null;
	//either a block or line commenting strategy
	if(element.getName().equals(ELEM_PROPOSAL_BLOCK_COMMENTING_STRATEGY)) {
	String prefix = element.getAttribute(ATTR_PREFIX);
	checkExtensionAttributeNotNull(prefix, ATTR_PREFIX, element);

	String suffix = element.getAttribute(ATTR_SUFFIX);
	checkExtensionAttributeNotNull(suffix, ATTR_SUFFIX, element);

	if(prefix != null && suffix != null) {
	newCommentingStrategy = new BlockCommentingStrategy(prefix, suffix);
	commentingStrategyRegistry = this.fBlockCommentTypes;
	}
	} else if(element.getName().equals(ELEM_PROPOSAL_LINE_COMMENTING_STRATEGY)) {
	String prefix = element.getAttribute(ATTR_PREFIX);
	checkExtensionAttributeNotNull(prefix, ATTR_PREFIX, element);

	if(prefix != null) {
	newCommentingStrategy = new LineCommentingStrategy(prefix);
	commentingStrategyRegistry = this.fLineCommentTypes;
	}
	}

	//add the new strategy to the registry
	if(commentingStrategyRegistry != null && newCommentingStrategy != null) {
	addCommentingStrategyToRegistry(element, commentingStrategyRegistry, newCommentingStrategy);
	} else {
	Logger.log(Logger.WARNING, "Invalid CommentingStrategy extension: " + element); //$NON-NLS-1$
	}
	} catch (CoreException e) {
	Logger.logException(e);
	} catch (InvalidRegistryObjectException x) {
	/* Element is not valid any longer as the contributing plug-in was unloaded or for
	* some other reason. Do not include the extension in the list and log it
	*/
	String message = "The extension ''" + element.toString() + "'' is invalid."; //$NON-NLS-1$ //$NON-NLS-2$
	IStatus status= new Status(IStatus.WARNING, SSEUIPlugin.ID, IStatus.WARNING, message, x);
	Logger.log(status);
	}
	}
	}

	/**
	* <p>Checks that the given attribute value is not <code>null</code>.</p>
	*
	* @param value the object to check if not null
	* @param attribute the attribute
	*
	* @throws InvalidRegistryObjectException if the registry element is no longer valid
	* @throws CoreException if <code>value</code> is <code>null</code>
	*/
	private static void checkExtensionAttributeNotNull(Object value, String attribute,
	IConfigurationElement element) throws InvalidRegistryObjectException, CoreException {

	if (value == null) {
	String message = "The extension \"" + element.getDeclaringExtension().getUniqueIdentifier() + //$NON-NLS-1$
	"\" from plug-in \"" + element.getContributor().getName() + //$NON-NLS-1$
	"\" did not specify a value for the required \"" + attribute + //$NON-NLS-1$
	"\" attribute for the element \"" + element.getName() + "\". Disabling the extension."; //$NON-NLS-1$ //$NON-NLS-2$
	IStatus status= new Status(IStatus.WARNING, SSEUIPlugin.ID, IStatus.OK, message, null);
	throw new CoreException(status);
	}
	}

	/**
	* <p>Using the content type element children of the given element add a copy of the given
	* base commenting strategy to the given registry</p>
	*
	* @param element a {@link IConfigurationElement} with contentType element children
	* @param commentingStrategyRegistry {@link Map} of content type ids to {@link CommentingStrategy}s to register
	* the given {@link CommentingStrategy} with based on the <code>element</code>
	* @param baseCommentingStrategy {@link CommentingStrategy} that will be cloned and configured for each
	* content type in the given <code>element</code>
	*/
	private static void addCommentingStrategyToRegistry(IConfigurationElement element,
	Map commentingStrategyRegistry, CommentingStrategy baseCommentingStrategy) {

	//get all the content type elements
	IConfigurationElement[] contentTypeElements = element.getChildren(ELEM_CONTENT_TYPE);
	if(contentTypeElements.length > 0) {
	for(int contentTypeIndex = 0; contentTypeIndex < contentTypeElements.length; ++contentTypeIndex) {
	try {
	String contentTypeID = contentTypeElements[contentTypeIndex].getAttribute(ATTR_ID);
	checkExtensionAttributeNotNull(contentTypeID, ATTR_ID, contentTypeElements[contentTypeIndex]);

	List commentTypes = (List)commentingStrategyRegistry.get(contentTypeID);
	if(commentTypes == null) {
	commentTypes = new ArrayList();
	commentingStrategyRegistry.put(contentTypeID, commentTypes);
	}

	//this element is required
	List allowablePartitionTypeIDs = new ArrayList();
	IConfigurationElement[] allowablePartitionTypes =
	contentTypeElements[contentTypeIndex].getChildren(ELEM_ALLOWABLE_PARTITION_TYPES);
	boolean anyPartitionType = false;
	//determine anyPartitionType attribute value
	String anyPartitionTypeValue = allowablePartitionTypes[0].getAttribute(ATTR_ANY_PARTITION_TYPE);
	if(anyPartitionTypeValue != null) {
	anyPartitionType = Boolean.valueOf(anyPartitionTypeValue).booleanValue();
	}

	//get the optional partition types
	allowablePartitionTypes = allowablePartitionTypes[0].getChildren(ELEM_PARTITION_TYPE);
	if(allowablePartitionTypes.length > 0) {
	for (int partitionTypeIndex = 0; partitionTypeIndex < allowablePartitionTypes.length; ++partitionTypeIndex) {
	String partitionTypeID = allowablePartitionTypes[partitionTypeIndex].getAttribute(ATTR_ID);
	checkExtensionAttributeNotNull(partitionTypeID, ATTR_ID, allowablePartitionTypes[partitionTypeIndex]);

	allowablePartitionTypeIDs.add(partitionTypeID);
	}
	}

	//this element is optional
	List requiredPartitionTypeIDs = new ArrayList();
	IConfigurationElement[] requiredPartitionTypes =
	contentTypeElements[contentTypeIndex].getChildren(ELEM_REQUIRED_PARTITION_TYPES);
	if(requiredPartitionTypes.length > 0) {
	//get the required partition types
	requiredPartitionTypes = requiredPartitionTypes[0].getChildren(ELEM_PARTITION_TYPE);
	if(requiredPartitionTypes.length > 0) {
	for (int partitionTypeIndex = 0; partitionTypeIndex < requiredPartitionTypes.length; ++partitionTypeIndex) {
	String partitionTypeID = requiredPartitionTypes[partitionTypeIndex].getAttribute(ATTR_ID);
	checkExtensionAttributeNotNull(partitionTypeID, ATTR_ID, requiredPartitionTypes[partitionTypeIndex]);

	requiredPartitionTypeIDs.add(partitionTypeID);
	}
	}
	}

	//get the optional associated comment partition type ID
	String associatedCommentPartitionTypeID =
	contentTypeElements[contentTypeIndex].getAttribute(ATTR_ASSOCIATED_COMMENT_PARTITION_TPYPE_ID);

	//register the strategy
	CommentingStrategy newCommentingStrategy = (CommentingStrategy)baseCommentingStrategy.clone();
	newCommentingStrategy.setPartitionInformation(allowablePartitionTypeIDs, anyPartitionType,
	requiredPartitionTypeIDs, associatedCommentPartitionTypeID);
	commentTypes.add(newCommentingStrategy);
	} catch(CoreException e) {
	Logger.logException(e);
	}
	}
	} else {
	Logger.log(Logger.WARNING, "The commmenting strategy element: " + element +//$NON-NLS-1$
	" does not contain any required " + ELEM_CONTENT_TYPE + "s"); //$NON-NLS-1$ //$NON-NLS-2$
	}
	}
	}