org.eclipse.gmf.runtime.common.ui.services.dnd/src/org/eclipse/gmf/runtime/common/ui/services/dnd/core/DragDropListenerService.java - gmf-runtime/org.eclipse.gmf-runtime - Git at Google

 /******************************************************************************
  * Copyright (c) 2002, 2006 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.gmf.runtime.common.ui.services.dnd.core;

 import java.text.MessageFormat;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Enumeration;
 import java.util.Hashtable;
 import java.util.Iterator;
 import java.util.List;
 import java.util.Vector;

 import org.eclipse.core.runtime.IConfigurationElement;

 import org.eclipse.gmf.runtime.common.core.service.ExecutionStrategy;
 import org.eclipse.gmf.runtime.common.core.service.IOperation;
 import org.eclipse.gmf.runtime.common.core.service.Service;
 import org.eclipse.gmf.runtime.common.core.util.Log;
 import org.eclipse.gmf.runtime.common.core.util.StringStatics;
 import org.eclipse.gmf.runtime.common.core.util.Trace;
 import org.eclipse.gmf.runtime.common.ui.services.dnd.drag.IDragSourceListener;
 import org.eclipse.gmf.runtime.common.ui.services.dnd.drop.IDropTargetListener;
 import org.eclipse.gmf.runtime.common.ui.services.dnd.internal.CommonUIServicesDNDDebugOptions;
 import org.eclipse.gmf.runtime.common.ui.services.dnd.internal.CommonUIServicesDNDPlugin;
 import org.eclipse.gmf.runtime.common.ui.services.dnd.internal.CommonUIServicesDNDStatusCodes;
 import org.eclipse.gmf.runtime.common.ui.services.dnd.internal.core.GetDragListenerOperation;
 import org.eclipse.gmf.runtime.common.ui.services.dnd.internal.core.GetDropListenerOperation;
 import org.eclipse.gmf.runtime.common.ui.services.dnd.internal.core.ListenerOperation;

 /**
  * A service that provides the <code>IDragSourceListener</code> and
  * <code>IDropTargetListener</code>. This service gets the all the providers
  * that provide listeners for the specified context.
  *
  * @author Vishy Ramaswamy
  */
 public class DragDropListenerService
 	extends Service
 	implements IDragDropListenerProvider {

 	/**
 	 * A descriptor for <code>IDragDropListenerProvider</code> defined by a
 	 * configuration element.
 	 *
 	 * @author Vishy Ramaswamy
 	 */
 	protected static class ProviderDescriptor
 		extends Service.ProviderDescriptor {

 		/**
 		 * Attribute for maintaining the provider information
 		 */
 		private Hashtable partInfo = null;

 		/**
 		 * Constructs a <code>IDragDropListenerProvider</code> descriptor for
 		 * the specified configuration element.
 		 *
 		 * @param element
 		 *            The configuration element describing the provider.
 		 * @param aPartInfo
 		 *            A <code>Hashtable</code> with the provider information
 		 */
 		protected ProviderDescriptor(IConfigurationElement element,
 				Hashtable aPartInfo) {
 			super(element);

 			assert null != aPartInfo : "aPartInfo cannot be null"; //$NON-NLS-1$

 			this.partInfo = aPartInfo;
 		}

 		/*
 		 * (non-Javadoc)
 		 *
 		 * @see org.eclipse.gmf.runtime.common.core.service.IProvider#provides(org.eclipse.gmf.runtime.common.core.service.IOperation)
 		 */
 		public boolean provides(IOperation operation) {
 			/* Check the operations */
 			if (!(operation instanceof GetDragListenerOperation)
 				&& !(operation instanceof GetDropListenerOperation)) {
 				return false;
 			}

 			/* Get all the context information */
 			Class elementType = null;
 			String partId = null;
 			String operationType = null;
 			String transferId = null;
 			boolean isCompatible = false;

 			if (operation instanceof GetDragListenerOperation) {
 				elementType = ((IDragListenerContext) ((GetDragListenerOperation) operation)
 					.getContext()).getSelectedElementType();
 				partId = ((IDragListenerContext) ((GetDragListenerOperation) operation)
 					.getContext()).getActivePart().getSite().getId();
 				operationType = ((GetDragListenerOperation) operation)
 					.getContext().getOperationType();
 				transferId = ((IDragListenerContext) ((GetDragListenerOperation) operation)
 					.getContext()).getTransferId();
 				isCompatible = ((IDragListenerContext) ((GetDragListenerOperation) operation)
 					.getContext()).isCompatible();
 			}

 			if (operation instanceof GetDropListenerOperation) {
 				elementType = ((IDropListenerContext) ((GetDropListenerOperation) operation)
 					.getContext()).getTargetElementType();
 				partId = ((IDropListenerContext) ((GetDropListenerOperation) operation)
 					.getContext()).getActivePart().getSite().getId();
 				operationType = ((GetDropListenerOperation) operation)
 					.getContext().getOperationType();
 				transferId = ((IDropListenerContext) ((GetDropListenerOperation) operation)
 					.getContext()).getTransferId();
 				isCompatible = ((IDropListenerContext) ((GetDropListenerOperation) operation)
 					.getContext()).isCompatible();
 			}

 			if (Trace.shouldTrace(CommonUIServicesDNDPlugin.getDefault(),
 				CommonUIServicesDNDDebugOptions.DND)) {
 				Trace.trace(CommonUIServicesDNDPlugin.getDefault(),
 					CommonUIServicesDNDDebugOptions.DND,
 					"DNDS:provides::Element Type is " + elementType.getName()); //$NON-NLS-1$
 				Trace.trace(CommonUIServicesDNDPlugin.getDefault(),
 					CommonUIServicesDNDDebugOptions.DND,
 					"DNDS:provides::Part Id is " + partId); //$NON-NLS-1$
 				Trace.trace(CommonUIServicesDNDPlugin.getDefault(),
 					CommonUIServicesDNDDebugOptions.DND,
 					"DNDS:provides::Operation Type is " + operationType); //$NON-NLS-1$
 				Trace.trace(CommonUIServicesDNDPlugin.getDefault(),
 					CommonUIServicesDNDDebugOptions.DND,
 					"DNDS:provides::Transfer id is " + transferId); //$NON-NLS-1$
 				Trace.trace(CommonUIServicesDNDPlugin.getDefault(),
 					CommonUIServicesDNDDebugOptions.DND,
 					"DNDS:provides::Compatible is " + isCompatible); //$NON-NLS-1$
 			}

 			/* Check if the part is handled */
 			Hashtable elementTypeTable = (Hashtable) getPartInfo().get(partId);
 			if (elementTypeTable == null) {
 				return false;
 			}

 			/* Check if the operation type is handled */
 			Hashtable operationTypeTable = (Hashtable) elementTypeTable
 				.get(isCompatible ? getCompatibleType(elementTypeTable,
 					elementType).getName()
 					: elementType.getName());
 			if (operationTypeTable == null) {
 				return false;
 			}

 			/* Get the transfer id list */
 			List transferIdList = (List) operationTypeTable.get(operationType);
 			if (transferIdList == null) {
 				return false;
 			}

 			/* Check if the requested transfer is available */
 			return (transferId.equals(IListenerContext.ALL_TRANSFERS)) ? true
 				: transferIdList.contains(transferId);
 		}

 		/**
 		 * Returns the <code>Hashtable</code> containing the provider
 		 * information
 		 *
 		 * @return Return the <code>partInfo</code> instance variable
 		 */
 		private Hashtable getPartInfo() {
 			return partInfo;
 		}

 		/**
 		 * Returns the element type from the element type table that is
 		 * assignable from the specified element type
 		 *
 		 * @param elementTypeTable
 		 *            The table of element types
 		 * @param elementType
 		 *            The specified element type
 		 * @return Return the compatible type
 		 */
 		private Class getCompatibleType(Hashtable elementTypeTable,
 				Class elementType) {
 			/*
 			 * Enumerate through the element types and check if if the class or
 			 * interface is either the same as, or is a superclass or
 			 * superinterface of, the class or interface represented by the
 			 * specified element type
 			 */
 			Class newClass = null;
 			String className = null;
 			Enumeration enumeration = elementTypeTable.keys();
 			while (enumeration.hasMoreElements()) {
 				className = (String) enumeration.nextElement();

 				try {
 					newClass = Class.forName(className, false, elementType
 						.getClassLoader());
 				} catch (ClassNotFoundException e) {
 					// This is an expected exception. Do not log - only trace.
 					Trace.catching(CommonUIServicesDNDPlugin.getDefault(),
 						CommonUIServicesDNDDebugOptions.EXCEPTIONS_CATCHING,
 						getClass(), "getCompatibleType", e); //$NON-NLS-1$
 				}

 				if (newClass != null && newClass.isAssignableFrom(elementType)) {
 					return newClass;
 				}
 			}

 			return elementType;
 		}
 	}

 	/**
 	 * The DragDropListenerService constructor
 	 */
 	private final static DragDropListenerService instance = new DragDropListenerService();

 	static {
 		instance.configureProviders(CommonUIServicesDNDPlugin.getPluginId(), "dragDropListenerProviders"); //$NON-NLS-1$
 	}

 	/**
 	 * The DragDropListenerService constructor
 	 */
 	protected DragDropListenerService() {
 		super(false);
 	}

 	/**
 	 * Gets the instance of DragDropListenerService
 	 *
 	 * @return Returns the <code>instance</code> variable
 	 */
 	public static DragDropListenerService getInstance() {
 		return instance;
 	}

 	/**
 	 * Executes the <code>ListenerOperation</code> operation using the FORWARD
 	 * strategy
 	 *
 	 * @param operation
 	 *            The operation
 	 *
 	 * @return Returns a <code>Object</code>
 	 */
 	private Object execute(ListenerOperation operation) {
 		List results = execute(ExecutionStrategy.FORWARD, operation);

 		if (operation instanceof GetDragListenerOperation) {
 			return results.isEmpty() ? null
 				: combineArraysInList(results, new IDragSourceListener[0]);
 		} else if (operation instanceof GetDropListenerOperation) {
 			return results.isEmpty() ? null
 				: combineArraysInList(results, new IDropTargetListener[0]);
 		}

 		return null;
 	}

 	/*
 	 * (non-Javadoc)
 	 *
 	 * @see org.eclipse.gmf.runtime.common.core.internal.service.Service#newProviderDescriptor(org.eclipse.core.runtime.IConfigurationElement)
 	 */
 	protected Service.ProviderDescriptor newProviderDescriptor(
 			IConfigurationElement element) {
 		return new ProviderDescriptor(element,
 			getDragDropListenerProviderInfo(element));
 	}

 	/**
 	 * Captures all the <code>IDragDropListenerProvider</code> information.
 	 *
 	 * @param element
 	 *            The configuration element associated with the provider
 	 *
 	 * @return Returns a <code>Hashtable</code>
 	 */
 	private Hashtable getDragDropListenerProviderInfo(
 			IConfigurationElement element) {
 		/* Get the view id children */
 		Hashtable providerInfo = new Hashtable();
 		try {
 			IConfigurationElement[] viewChildren = element
 				.getChildren("ViewId"); //$NON-NLS-1$
 			for (int i = 0; i < viewChildren.length; i++) {
 				/* Get the view element */
 				IConfigurationElement viewConfig = viewChildren[i];

 				/* Get the view id attribute */
 				String id = viewConfig.getAttribute("id"); //$NON-NLS-1$
 				if (id == null) {
 					handleInvalidElement(viewConfig);
 					continue;
 				}

 				/* Add a placeholder in the table */
 				providerInfo.put(id, new Hashtable());

 				/* Get all the element types */
 				IConfigurationElement[] elementTypeChildren = viewConfig
 					.getChildren();
 				for (int j = 0; j < elementTypeChildren.length; j++) {
 					IConfigurationElement elementTypeConfig = elementTypeChildren[j];

 					/* Get the class attribute */
 					String elementTypeClass = elementTypeConfig
 						.getAttribute("class"); //$NON-NLS-1$
 					if (elementTypeClass == null) {
 						handleInvalidElement(elementTypeConfig);
 						continue;
 					}
 					/* Add a placeholder for the element type */
 					Hashtable table = (Hashtable) providerInfo.get(id);
 					table.put(elementTypeClass, new Hashtable());

 					/* Get the operation type children */
 					IConfigurationElement[] operationTypeChildren = elementTypeConfig
 						.getChildren();
 					for (int k = 0; k < operationTypeChildren.length; k++) {
 						IConfigurationElement operationTypeConfig = operationTypeChildren[k];

 						/* Get the operation type attributes */
 						String operationType = operationTypeConfig
 							.getAttribute("operation"); //$NON-NLS-1$
 						if (operationType == null) {
 							handleInvalidElement(operationTypeConfig);
 							continue;
 						}
 						/* Get the transfer type children */
 						Vector listOftransferId = new Vector();
 						IConfigurationElement[] transferTypeChildren = operationTypeConfig
 							.getChildren();
 						for (int l = 0; l < transferTypeChildren.length; l++) {
 							IConfigurationElement transferIdConfig = transferTypeChildren[l];

 							/* Get the transfer id attributes */
 							String transferId = transferIdConfig
 								.getAttribute("transferId"); //$NON-NLS-1$
 							if (transferId == null) {
 								handleInvalidElement(transferIdConfig);
 								continue;
 							}
 							/* Add to the list */
 							listOftransferId.addElement(transferId);

 						}

 						/* Add a placeholder for the operation type */
 						table = (Hashtable) ((Hashtable) providerInfo.get(id))
 							.get(elementTypeClass);
 						table.put(operationType, listOftransferId);
 					}
 				}
 			}
 		} catch (Exception e) {
 			Trace.catching(CommonUIServicesDNDPlugin.getDefault(),
 				CommonUIServicesDNDDebugOptions.EXCEPTIONS_CATCHING,
 				getClass(), "getDragDropListenerProviderInfo", e); //$NON-NLS-1$
 			Log.error(CommonUIServicesDNDPlugin.getDefault(),
 				CommonUIServicesDNDStatusCodes.SERVICE_FAILURE, MessageFormat
 					.format(INVALID_ELEMENT_MESSAGE_PATTERN,
 						new Object[] {element.getName()}), e);
 		}

 		return providerInfo;
 	}

 	/**
 	 * Traces and logs a message to indicate that the XML element is invalid.
 	 *
 	 * @param element
 	 *            the invalid XML element
 	 */
 	private void handleInvalidElement(IConfigurationElement element) {

 		String message = MessageFormat.format(INVALID_ELEMENT_MESSAGE_PATTERN,
 			new Object[] {element.getDeclaringExtension().toString()
 				+ StringStatics.COLON + element.getName()});

 		Trace.trace(CommonUIServicesDNDPlugin.getDefault(),
 			CommonUIServicesDNDDebugOptions.SERVICES_CONFIG, message);
 		Log.error(CommonUIServicesDNDPlugin.getDefault(),
 			CommonUIServicesDNDStatusCodes.SERVICE_FAILURE, message);
 	}

 	/**
 	 * Utility to get all the registered transfer ids against a part id for an
 	 * operation type
 	 *
 	 * @param partId
 	 *            the part id
 	 * @param operationType
 	 *            the type of operation (drag or drop)
 	 * @return array of transfer ids
 	 */
 	public String[] getAllTransferIds(String partId, String operationType) {
 		assert null != partId : "partId cannot be null"; //$NON-NLS-1$
 		assert null != operationType : "operationType cannot be null"; //$NON-NLS-1$

 		/* Get all the providers */
 		List list = getAllProviders();

 		/* Iterate through all the providers */
 		ArrayList transferIds = new ArrayList();
 		Iterator it = list.iterator();
 		while (it.hasNext()) {
 			/* Get the next descriptor */
 			ProviderDescriptor descriptor = (ProviderDescriptor) it.next();

 			/* Check if the part is handled */
 			Hashtable elementTypeTable = (Hashtable) descriptor.getPartInfo()
 				.get(partId);
 			if (elementTypeTable == null) {
 				continue;
 			}

 			/* Go through all the element types */
 			Enumeration e = elementTypeTable.elements();
 			while (e.hasMoreElements()) {
 				/* Get the operation type table */
 				Hashtable operationTypeTable = (Hashtable) e.nextElement();

 				/* Check if the operation is handled */
 				if (operationTypeTable.containsKey(operationType)) {
 					/* Get the transfer id list */
 					List transferIdList = (List) operationTypeTable
 						.get(operationType);

 					/* Get the transfer id */
 					Iterator transfer = transferIdList.iterator();
 					while (transfer.hasNext()) {
 						/*
 						 * Get the id and add it to the list if it does not
 						 * exist
 						 */
 						String transferId = (String) transfer.next();
 						if (!transferIds.contains(transferId)) {
 							transferIds.add(transferId);
 						}
 					}
 				}
 			}
 		}

 		/* Return the list of ids */
 		return !transferIds.isEmpty() ? (String[]) transferIds
 			.toArray(new String[transferIds.size()])
 			: null;
 	}

 	/*
 	 * (non-Javadoc)
 	 *
 	 * @see org.eclipse.gmf.runtime.common.ui.services.dnd.core.IDragDropListenerProvider#getDragSourceListeners(org.eclipse.gmf.runtime.common.ui.services.dnd.core.IDragListenerContext)
 	 */
 	public IDragSourceListener[] getDragSourceListeners(
 			IDragListenerContext context) {
 		assert null != context : "context cannot be null"; //$NON-NLS-1$

 		return (IDragSourceListener[]) execute(new GetDragListenerOperation(
 			context));
 	}

 	/*
 	 * (non-Javadoc)
 	 *
 	 * @see org.eclipse.gmf.runtime.common.ui.services.dnd.core.IDragDropListenerProvider#getDropTargetListeners(org.eclipse.gmf.runtime.common.ui.services.dnd.core.IDropListenerContext)
 	 */
 	public IDropTargetListener[] getDropTargetListeners(
 			IDropListenerContext context) {
 		assert null != context : "context cannot be null"; //$NON-NLS-1$

 		return (IDropTargetListener[]) execute(new GetDropListenerOperation(
 			context));
 	}

 	/**
 	 * Combines the arrays in the passed list into one array.
 	 *
 	 * @param list
 	 *            The List of arrays to combine together
 	 * @param resultingArrayType
 	 *            the Object[] used to define the type of the combined array
 	 *
 	 * @return Object[] the combined array of the proper type
 	 */
 	private final Object[] combineArraysInList(List list,
 			Object[] resultingArrayType) {
 		List listEntry = null;
 		Iterator it = list.iterator();
 		ArrayList results = new ArrayList();
 		while (it.hasNext()) {
 			Object[] array = (Object[]) it.next();
 			if (array != null && array.length > 0) {
 				listEntry = Arrays.asList(array);
 				results.addAll(listEntry);
 			}
 		}

 		return results.toArray(resultingArrayType);
 	}
 }
	/******************************************************************************
	* Copyright (c) 2002, 2006 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.gmf.runtime.common.ui.services.dnd.core;

	import java.text.MessageFormat;
	import java.util.ArrayList;
	import java.util.Arrays;
	import java.util.Enumeration;
	import java.util.Hashtable;
	import java.util.Iterator;
	import java.util.List;
	import java.util.Vector;

	import org.eclipse.core.runtime.IConfigurationElement;

	import org.eclipse.gmf.runtime.common.core.service.ExecutionStrategy;
	import org.eclipse.gmf.runtime.common.core.service.IOperation;
	import org.eclipse.gmf.runtime.common.core.service.Service;
	import org.eclipse.gmf.runtime.common.core.util.Log;
	import org.eclipse.gmf.runtime.common.core.util.StringStatics;
	import org.eclipse.gmf.runtime.common.core.util.Trace;
	import org.eclipse.gmf.runtime.common.ui.services.dnd.drag.IDragSourceListener;
	import org.eclipse.gmf.runtime.common.ui.services.dnd.drop.IDropTargetListener;
	import org.eclipse.gmf.runtime.common.ui.services.dnd.internal.CommonUIServicesDNDDebugOptions;
	import org.eclipse.gmf.runtime.common.ui.services.dnd.internal.CommonUIServicesDNDPlugin;
	import org.eclipse.gmf.runtime.common.ui.services.dnd.internal.CommonUIServicesDNDStatusCodes;
	import org.eclipse.gmf.runtime.common.ui.services.dnd.internal.core.GetDragListenerOperation;
	import org.eclipse.gmf.runtime.common.ui.services.dnd.internal.core.GetDropListenerOperation;
	import org.eclipse.gmf.runtime.common.ui.services.dnd.internal.core.ListenerOperation;

	/**
	* A service that provides the <code>IDragSourceListener</code> and
	* <code>IDropTargetListener</code>. This service gets the all the providers
	* that provide listeners for the specified context.
	*
	* @author Vishy Ramaswamy
	*/
	public class DragDropListenerService
	extends Service
	implements IDragDropListenerProvider {

	/**
	* A descriptor for <code>IDragDropListenerProvider</code> defined by a
	* configuration element.
	*
	* @author Vishy Ramaswamy
	*/
	protected static class ProviderDescriptor
	extends Service.ProviderDescriptor {

	/**
	* Attribute for maintaining the provider information
	*/
	private Hashtable partInfo = null;

	/**
	* Constructs a <code>IDragDropListenerProvider</code> descriptor for
	* the specified configuration element.
	*
	* @param element
	* The configuration element describing the provider.
	* @param aPartInfo
	* A <code>Hashtable</code> with the provider information
	*/
	protected ProviderDescriptor(IConfigurationElement element,
	Hashtable aPartInfo) {
	super(element);

	assert null != aPartInfo : "aPartInfo cannot be null"; //$NON-NLS-1$

	this.partInfo = aPartInfo;
	}

	/*
	* (non-Javadoc)
	*
	* @see org.eclipse.gmf.runtime.common.core.service.IProvider#provides(org.eclipse.gmf.runtime.common.core.service.IOperation)
	*/
	public boolean provides(IOperation operation) {
	/* Check the operations */
	if (!(operation instanceof GetDragListenerOperation)
	&& !(operation instanceof GetDropListenerOperation)) {
	return false;
	}

	/* Get all the context information */
	Class elementType = null;
	String partId = null;
	String operationType = null;
	String transferId = null;
	boolean isCompatible = false;

	if (operation instanceof GetDragListenerOperation) {
	elementType = ((IDragListenerContext) ((GetDragListenerOperation) operation)
	.getContext()).getSelectedElementType();
	partId = ((IDragListenerContext) ((GetDragListenerOperation) operation)
	.getContext()).getActivePart().getSite().getId();
	operationType = ((GetDragListenerOperation) operation)
	.getContext().getOperationType();
	transferId = ((IDragListenerContext) ((GetDragListenerOperation) operation)
	.getContext()).getTransferId();
	isCompatible = ((IDragListenerContext) ((GetDragListenerOperation) operation)
	.getContext()).isCompatible();
	}

	if (operation instanceof GetDropListenerOperation) {
	elementType = ((IDropListenerContext) ((GetDropListenerOperation) operation)
	.getContext()).getTargetElementType();
	partId = ((IDropListenerContext) ((GetDropListenerOperation) operation)
	.getContext()).getActivePart().getSite().getId();
	operationType = ((GetDropListenerOperation) operation)
	.getContext().getOperationType();
	transferId = ((IDropListenerContext) ((GetDropListenerOperation) operation)
	.getContext()).getTransferId();
	isCompatible = ((IDropListenerContext) ((GetDropListenerOperation) operation)
	.getContext()).isCompatible();
	}

	if (Trace.shouldTrace(CommonUIServicesDNDPlugin.getDefault(),
	CommonUIServicesDNDDebugOptions.DND)) {
	Trace.trace(CommonUIServicesDNDPlugin.getDefault(),
	CommonUIServicesDNDDebugOptions.DND,
	"DNDS:provides::Element Type is " + elementType.getName()); //$NON-NLS-1$
	Trace.trace(CommonUIServicesDNDPlugin.getDefault(),
	CommonUIServicesDNDDebugOptions.DND,
	"DNDS:provides::Part Id is " + partId); //$NON-NLS-1$
	Trace.trace(CommonUIServicesDNDPlugin.getDefault(),
	CommonUIServicesDNDDebugOptions.DND,
	"DNDS:provides::Operation Type is " + operationType); //$NON-NLS-1$
	Trace.trace(CommonUIServicesDNDPlugin.getDefault(),
	CommonUIServicesDNDDebugOptions.DND,
	"DNDS:provides::Transfer id is " + transferId); //$NON-NLS-1$
	Trace.trace(CommonUIServicesDNDPlugin.getDefault(),
	CommonUIServicesDNDDebugOptions.DND,
	"DNDS:provides::Compatible is " + isCompatible); //$NON-NLS-1$
	}

	/* Check if the part is handled */
	Hashtable elementTypeTable = (Hashtable) getPartInfo().get(partId);
	if (elementTypeTable == null) {
	return false;
	}

	/* Check if the operation type is handled */
	Hashtable operationTypeTable = (Hashtable) elementTypeTable
	.get(isCompatible ? getCompatibleType(elementTypeTable,
	elementType).getName()
	: elementType.getName());
	if (operationTypeTable == null) {
	return false;
	}

	/* Get the transfer id list */
	List transferIdList = (List) operationTypeTable.get(operationType);
	if (transferIdList == null) {
	return false;
	}

	/* Check if the requested transfer is available */
	return (transferId.equals(IListenerContext.ALL_TRANSFERS)) ? true
	: transferIdList.contains(transferId);
	}

	/**
	* Returns the <code>Hashtable</code> containing the provider
	* information
	*
	* @return Return the <code>partInfo</code> instance variable
	*/
	private Hashtable getPartInfo() {
	return partInfo;
	}

	/**
	* Returns the element type from the element type table that is
	* assignable from the specified element type
	*
	* @param elementTypeTable
	* The table of element types
	* @param elementType
	* The specified element type
	* @return Return the compatible type
	*/
	private Class getCompatibleType(Hashtable elementTypeTable,
	Class elementType) {
	/*
	* Enumerate through the element types and check if if the class or
	* interface is either the same as, or is a superclass or
	* superinterface of, the class or interface represented by the
	* specified element type
	*/
	Class newClass = null;
	String className = null;
	Enumeration enumeration = elementTypeTable.keys();
	while (enumeration.hasMoreElements()) {
	className = (String) enumeration.nextElement();

	try {
	newClass = Class.forName(className, false, elementType
	.getClassLoader());
	} catch (ClassNotFoundException e) {
	// This is an expected exception. Do not log - only trace.
	Trace.catching(CommonUIServicesDNDPlugin.getDefault(),
	CommonUIServicesDNDDebugOptions.EXCEPTIONS_CATCHING,
	getClass(), "getCompatibleType", e); //$NON-NLS-1$
	}

	if (newClass != null && newClass.isAssignableFrom(elementType)) {
	return newClass;
	}
	}

	return elementType;
	}
	}

	/**
	* The DragDropListenerService constructor
	*/
	private final static DragDropListenerService instance = new DragDropListenerService();

	static {
	instance.configureProviders(CommonUIServicesDNDPlugin.getPluginId(), "dragDropListenerProviders"); //$NON-NLS-1$
	}

	/**
	* The DragDropListenerService constructor
	*/
	protected DragDropListenerService() {
	super(false);
	}

	/**
	* Gets the instance of DragDropListenerService
	*
	* @return Returns the <code>instance</code> variable
	*/
	public static DragDropListenerService getInstance() {
	return instance;
	}

	/**
	* Executes the <code>ListenerOperation</code> operation using the FORWARD
	* strategy
	*
	* @param operation
	* The operation
	*
	* @return Returns a <code>Object</code>
	*/
	private Object execute(ListenerOperation operation) {
	List results = execute(ExecutionStrategy.FORWARD, operation);

	if (operation instanceof GetDragListenerOperation) {
	return results.isEmpty() ? null
	: combineArraysInList(results, new IDragSourceListener[0]);
	} else if (operation instanceof GetDropListenerOperation) {
	return results.isEmpty() ? null
	: combineArraysInList(results, new IDropTargetListener[0]);
	}

	return null;
	}

	/*
	* (non-Javadoc)
	*
	* @see org.eclipse.gmf.runtime.common.core.internal.service.Service#newProviderDescriptor(org.eclipse.core.runtime.IConfigurationElement)
	*/
	protected Service.ProviderDescriptor newProviderDescriptor(
	IConfigurationElement element) {
	return new ProviderDescriptor(element,
	getDragDropListenerProviderInfo(element));
	}

	/**
	* Captures all the <code>IDragDropListenerProvider</code> information.
	*
	* @param element
	* The configuration element associated with the provider
	*
	* @return Returns a <code>Hashtable</code>
	*/
	private Hashtable getDragDropListenerProviderInfo(
	IConfigurationElement element) {
	/* Get the view id children */
	Hashtable providerInfo = new Hashtable();
	try {
	IConfigurationElement[] viewChildren = element
	.getChildren("ViewId"); //$NON-NLS-1$
	for (int i = 0; i < viewChildren.length; i++) {
	/* Get the view element */
	IConfigurationElement viewConfig = viewChildren[i];

	/* Get the view id attribute */
	String id = viewConfig.getAttribute("id"); //$NON-NLS-1$
	if (id == null) {
	handleInvalidElement(viewConfig);
	continue;
	}

	/* Add a placeholder in the table */
	providerInfo.put(id, new Hashtable());

	/* Get all the element types */
	IConfigurationElement[] elementTypeChildren = viewConfig
	.getChildren();
	for (int j = 0; j < elementTypeChildren.length; j++) {
	IConfigurationElement elementTypeConfig = elementTypeChildren[j];

	/* Get the class attribute */
	String elementTypeClass = elementTypeConfig
	.getAttribute("class"); //$NON-NLS-1$
	if (elementTypeClass == null) {
	handleInvalidElement(elementTypeConfig);
	continue;
	}
	/* Add a placeholder for the element type */
	Hashtable table = (Hashtable) providerInfo.get(id);
	table.put(elementTypeClass, new Hashtable());

	/* Get the operation type children */
	IConfigurationElement[] operationTypeChildren = elementTypeConfig
	.getChildren();
	for (int k = 0; k < operationTypeChildren.length; k++) {
	IConfigurationElement operationTypeConfig = operationTypeChildren[k];

	/* Get the operation type attributes */
	String operationType = operationTypeConfig
	.getAttribute("operation"); //$NON-NLS-1$
	if (operationType == null) {
	handleInvalidElement(operationTypeConfig);
	continue;
	}
	/* Get the transfer type children */
	Vector listOftransferId = new Vector();
	IConfigurationElement[] transferTypeChildren = operationTypeConfig
	.getChildren();
	for (int l = 0; l < transferTypeChildren.length; l++) {
	IConfigurationElement transferIdConfig = transferTypeChildren[l];

	/* Get the transfer id attributes */
	String transferId = transferIdConfig
	.getAttribute("transferId"); //$NON-NLS-1$
	if (transferId == null) {
	handleInvalidElement(transferIdConfig);
	continue;
	}
	/* Add to the list */
	listOftransferId.addElement(transferId);

	}

	/* Add a placeholder for the operation type */
	table = (Hashtable) ((Hashtable) providerInfo.get(id))
	.get(elementTypeClass);
	table.put(operationType, listOftransferId);
	}
	}
	}
	} catch (Exception e) {
	Trace.catching(CommonUIServicesDNDPlugin.getDefault(),
	CommonUIServicesDNDDebugOptions.EXCEPTIONS_CATCHING,
	getClass(), "getDragDropListenerProviderInfo", e); //$NON-NLS-1$
	Log.error(CommonUIServicesDNDPlugin.getDefault(),
	CommonUIServicesDNDStatusCodes.SERVICE_FAILURE, MessageFormat
	.format(INVALID_ELEMENT_MESSAGE_PATTERN,
	new Object[] {element.getName()}), e);
	}

	return providerInfo;
	}

	/**
	* Traces and logs a message to indicate that the XML element is invalid.
	*
	* @param element
	* the invalid XML element
	*/
	private void handleInvalidElement(IConfigurationElement element) {

	String message = MessageFormat.format(INVALID_ELEMENT_MESSAGE_PATTERN,
	new Object[] {element.getDeclaringExtension().toString()
	+ StringStatics.COLON + element.getName()});

	Trace.trace(CommonUIServicesDNDPlugin.getDefault(),
	CommonUIServicesDNDDebugOptions.SERVICES_CONFIG, message);
	Log.error(CommonUIServicesDNDPlugin.getDefault(),
	CommonUIServicesDNDStatusCodes.SERVICE_FAILURE, message);
	}

	/**
	* Utility to get all the registered transfer ids against a part id for an
	* operation type
	*
	* @param partId
	* the part id
	* @param operationType
	* the type of operation (drag or drop)
	* @return array of transfer ids
	*/
	public String[] getAllTransferIds(String partId, String operationType) {
	assert null != partId : "partId cannot be null"; //$NON-NLS-1$
	assert null != operationType : "operationType cannot be null"; //$NON-NLS-1$

	/* Get all the providers */
	List list = getAllProviders();

	/* Iterate through all the providers */
	ArrayList transferIds = new ArrayList();
	Iterator it = list.iterator();
	while (it.hasNext()) {
	/* Get the next descriptor */
	ProviderDescriptor descriptor = (ProviderDescriptor) it.next();

	/* Check if the part is handled */
	Hashtable elementTypeTable = (Hashtable) descriptor.getPartInfo()
	.get(partId);
	if (elementTypeTable == null) {
	continue;
	}

	/* Go through all the element types */
	Enumeration e = elementTypeTable.elements();
	while (e.hasMoreElements()) {
	/* Get the operation type table */
	Hashtable operationTypeTable = (Hashtable) e.nextElement();

	/* Check if the operation is handled */
	if (operationTypeTable.containsKey(operationType)) {
	/* Get the transfer id list */
	List transferIdList = (List) operationTypeTable
	.get(operationType);

	/* Get the transfer id */
	Iterator transfer = transferIdList.iterator();
	while (transfer.hasNext()) {
	/*
	* Get the id and add it to the list if it does not
	* exist
	*/
	String transferId = (String) transfer.next();
	if (!transferIds.contains(transferId)) {
	transferIds.add(transferId);
	}
	}
	}
	}
	}

	/* Return the list of ids */
	return !transferIds.isEmpty() ? (String[]) transferIds
	.toArray(new String[transferIds.size()])
	: null;
	}

	/*
	* (non-Javadoc)
	*
	* @see org.eclipse.gmf.runtime.common.ui.services.dnd.core.IDragDropListenerProvider#getDragSourceListeners(org.eclipse.gmf.runtime.common.ui.services.dnd.core.IDragListenerContext)
	*/
	public IDragSourceListener[] getDragSourceListeners(
	IDragListenerContext context) {
	assert null != context : "context cannot be null"; //$NON-NLS-1$

	return (IDragSourceListener[]) execute(new GetDragListenerOperation(
	context));
	}

	/*
	* (non-Javadoc)
	*
	* @see org.eclipse.gmf.runtime.common.ui.services.dnd.core.IDragDropListenerProvider#getDropTargetListeners(org.eclipse.gmf.runtime.common.ui.services.dnd.core.IDropListenerContext)
	*/
	public IDropTargetListener[] getDropTargetListeners(
	IDropListenerContext context) {
	assert null != context : "context cannot be null"; //$NON-NLS-1$

	return (IDropTargetListener[]) execute(new GetDropListenerOperation(
	context));
	}

	/**
	* Combines the arrays in the passed list into one array.
	*
	* @param list
	* The List of arrays to combine together
	* @param resultingArrayType
	* the Object[] used to define the type of the combined array
	*
	* @return Object[] the combined array of the proper type
	*/
	private final Object[] combineArraysInList(List list,
	Object[] resultingArrayType) {
	List listEntry = null;
	Iterator it = list.iterator();
	ArrayList results = new ArrayList();
	while (it.hasNext()) {
	Object[] array = (Object[]) it.next();
	if (array != null && array.length > 0) {
	listEntry = Arrays.asList(array);
	results.addAll(listEntry);
	}
	}

	return results.toArray(resultingArrayType);
	}
	}