bundles/org.eclipse.ui.navigator/src/org/eclipse/ui/navigator/internal/extensions/NavigatorContentDescriptor.java - platform/eclipse.platform.ui - Git at Google

 /*******************************************************************************
  * Copyright (c) 2003, 2005 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.ui.navigator.internal.extensions;

 import java.util.ArrayList;
 import java.util.Comparator;
 import java.util.Iterator;
 import java.util.List;

 import org.eclipse.core.expressions.ElementHandler;
 import org.eclipse.core.expressions.EvaluationContext;
 import org.eclipse.core.expressions.EvaluationResult;
 import org.eclipse.core.expressions.Expression;
 import org.eclipse.core.expressions.ExpressionConverter;
 import org.eclipse.core.expressions.IEvaluationContext;
 import org.eclipse.core.runtime.CoreException;
 import org.eclipse.core.runtime.IConfigurationElement;
 import org.eclipse.core.runtime.IStatus;
 import org.eclipse.jface.viewers.ILabelProvider;
 import org.eclipse.jface.viewers.IStructuredSelection;
 import org.eclipse.jface.viewers.ITreeContentProvider;
 import org.eclipse.osgi.util.NLS;
 import org.eclipse.ui.IPluginContribution;
 import org.eclipse.ui.WorkbenchException;
 import org.eclipse.ui.navigator.ICommonContentProvider;
 import org.eclipse.ui.navigator.ICommonLabelProvider;
 import org.eclipse.ui.navigator.INavigatorContentDescriptor;
 import org.eclipse.ui.navigator.INavigatorExtensionFilter;
 import org.eclipse.ui.navigator.Priority;
 import org.eclipse.ui.navigator.internal.CommonNavigatorMessages;
 import org.eclipse.ui.navigator.internal.CustomAndExpression;
 import org.eclipse.ui.navigator.internal.NavigatorPlugin;

 /**
  * Encapsulates the <code>org.eclipse.ui.navigator.navigatorContent</code>
  * extension point.
  * <p>
  * <strong>EXPERIMENTAL</strong>. This class or interface has been added as
  * part of a work in progress. There is a guarantee neither that this API will
  * work nor that it will remain the same. Please do not use this API without
  * consulting with the Platform/UI team.
  * </p>
  *
  * @since 3.2
  */
 public final class NavigatorContentDescriptor implements
 		INavigatorContentDescriptor, INavigatorContentExtPtConstants {

 	private static final INavigatorExtensionFilter[] NO_VIEWER_FILTERS = new INavigatorExtensionFilter[0];

 	private static final IConfigurationElement[] NO_DUPLICATE_CONTENT_FILTERS = new IConfigurationElement[0];

 	private String id;

 	private String name;

 	private IConfigurationElement configElement;

 	private String rootLabel;

 	private int priority = Integer.MAX_VALUE;

 	private Expression enablement;

 	private Expression possibleChildren;

 	private boolean root;

 	private String icon;

 	private String declaringPluginId;

 	private boolean enabledByDefault;

 	private IPluginContribution contribution;

 	private boolean hasLoadingFailed;

 	private IConfigurationElement[] duplicateContentFilterElements;

 	/**
 	 * Creates a new content descriptor from a configuration element.
 	 *
 	 * @param configElement
 	 *            configuration element to create a descriptor from
 	 *
 	 * @throws WorkbenchException
 	 *             if the configuration element could not be parsed. Reasons
 	 *             include:
 	 *             <ul>
 	 *             <li>A required attribute is missing.</li>
 	 *             <li>More elements are define than is allowed.</li>
 	 *             </ul>
 	 */
 	public NavigatorContentDescriptor(IConfigurationElement configElement)
 			throws WorkbenchException {
 		super();
 		this.configElement = configElement;
 		readConfigElement();
 	}

 	/**
 	 * Determine if this content extension is enabled for the given selection.
 	 * The content extension is enabled for the selection if and only if it is
 	 * enabled for each element in the selection.
 	 *
 	 * @param aStructuredSelection
 	 *            The selection from the viewer
 	 * @return True if and only if the extension is enabled for each element in
 	 *         the selection.
 	 */
 	public boolean isEnabledFor(IStructuredSelection aStructuredSelection) {
 		if (enablement == null)
 			return false;

 		IEvaluationContext context = null;

 		Iterator elements = aStructuredSelection.iterator();
 		while (elements.hasNext()) {
 			context = new EvaluationContext(null, elements.next());
 			try {
 				if (enablement.evaluate(context) == EvaluationResult.FALSE)
 					return false;
 			} catch (CoreException e) {
 				NavigatorPlugin.log(IStatus.ERROR, 0, e.getMessage(), e);
 				return false;
 			}
 		}
 		return true;
 	}

 	/**
 	 * Determine if this content extension is enabled for the given element.
 	 *
 	 * @param anElement
 	 *            The element that should be used for the evaluation.
 	 * @return True if and only if the extension is enabled for the element.
 	 */
 	public boolean isEnabledFor(Object anElement) {

 		if (enablement == null || anElement == null)
 			return false;

 		try {
 			return (enablement.evaluate(new EvaluationContext(null, anElement)) == EvaluationResult.TRUE);
 		} catch (CoreException e) {
 			NavigatorPlugin.log(IStatus.ERROR, 0, e.getMessage(), e);
 		}
 		return false;
 	}

 	/**
 	 * Determine if this content extension could provide the given element as a
 	 * child.
 	 *
 	 * <p>
 	 * This method is used to determine what the parent of an element could be
 	 * for Link with Editor support.
 	 * </p>
 	 *
 	 * @param anElement
 	 *            The element that should be used for the evaluation.
 	 * @return True if and only if the extension might provide an object of this
 	 *         type as a child.
 	 */
 	public boolean isPossibleChild(Object anElement) {

 		if ((enablement == null && possibleChildren == null)
 				|| anElement == null)
 			return false;

 		try {
 			if (possibleChildren != null)
 				return (possibleChildren.evaluate(new EvaluationContext(null,
 						anElement)) == EvaluationResult.TRUE);
 			else if (enablement != null)
 				return (enablement.evaluate(new EvaluationContext(null,
 						anElement)) == EvaluationResult.TRUE);
 		} catch (CoreException e) {
 			NavigatorPlugin.log(IStatus.ERROR, 0, e.getMessage(), e);
 		}
 		return false;
 	}

 	/*
 	 * (non-Javadoc)
 	 *
 	 * @see org.eclipse.ui.navigator.internal.extensions.INavigatorContentDescriptor#getId()
 	 */
 	public String getId() {
 		return id;
 	}

 	/*
 	 * (non-Javadoc)
 	 *
 	 * @see org.eclipse.ui.navigator.internal.extensions.INavigatorContentDescriptor#getName()
 	 */
 	public String getName() {
 		return name;
 	}

 	/*
 	 * (non-Javadoc)
 	 *
 	 * @see org.eclipse.ui.navigator.internal.extensions.INavigatorContentDescriptor#getPriority()
 	 */
 	public int getPriority() {
 		return priority;
 	}

 	/*
 	 * (non-Javadoc)
 	 *
 	 * @see org.eclipse.ui.navigator.internal.extensions.INavigatorContentDescriptor#isRoot()
 	 */
 	public boolean isRoot() {
 		return root;
 	}

 	/**
 	 * @return a label to be used to delay the loading -- used for a content
 	 *         extension that contributes a single root element
 	 *
 	 */
 	protected String getRootLabel() {
 		return rootLabel;
 	}

 	/**
 	 * Parses the configuration element.
 	 *
 	 * @throws WorkbenchException
 	 *             if the configuration element could not be parsed. Reasons
 	 *             include:
 	 *             <ul>
 	 *             <li>A required attribute is missing.</li>
 	 *             <li>More elements are define than is allowed.</li>
 	 *             </ul>
 	 */
 	void readConfigElement() throws WorkbenchException {
 		id = configElement.getAttribute(ATT_ID);
 		name = configElement.getAttribute(ATT_NAME);
 		String priorityString = configElement.getAttribute(ATT_PRIORITY);
 		icon = configElement.getAttribute(ATT_ICON);
 		rootLabel = configElement.getAttribute(ATT_ROOT_LABEL);

 		declaringPluginId = configElement.getDeclaringExtension()
 				.getNamespace();
 		String enabledByDefaultString = configElement
 				.getAttribute(ATT_ACTIVE_BY_DEFAULT);
 		enabledByDefault = (enabledByDefaultString != null && enabledByDefaultString
 				.length() > 0) ? Boolean.valueOf(
 				configElement.getAttribute(ATT_ACTIVE_BY_DEFAULT))
 				.booleanValue() : true;

 		if (priorityString != null) {
 			try {
 				Priority p = Priority.get(priorityString);
 				priority = p != null ? p.getValue() : -1;
 			} catch (NumberFormatException exception) {
 			}
 		}
 		if (id == null) {
 			throw new WorkbenchException(NLS.bind(
 					CommonNavigatorMessages.Attribute_Missing_Warning,
 					new Object[] {
 							ATT_ID,
 							configElement.getDeclaringExtension()
 									.getUniqueIdentifier(),
 							configElement.getDeclaringExtension()
 									.getNamespace() }));
 		}

 		IConfigurationElement[] children = configElement
 				.getChildren(TAG_ENABLEMENT);
 		if (children.length == 0) {

 			children = configElement.getChildren(TAG_TRIGGER_POINTS);
 			if (children.length == 1) {
 				enablement = new CustomAndExpression(children[0]);
 			} else if (children.length > 1) {
 				throw new WorkbenchException(NLS.bind(
 						CommonNavigatorMessages.Attribute_Missing_Warning,
 						new Object[] {
 								TAG_TRIGGER_POINTS,
 								configElement.getDeclaringExtension()
 										.getUniqueIdentifier(),
 								configElement.getDeclaringExtension()
 										.getNamespace() }));
 			}

 			children = configElement.getChildren(TAG_POSSIBLE_CHILDREN);
 			if (children.length == 1) {
 				possibleChildren = new CustomAndExpression(children[0]);
 			} else if (children.length > 1) {
 				throw new WorkbenchException(NLS.bind(
 						CommonNavigatorMessages.Attribute_Missing_Warning,
 						new Object[] {
 								TAG_POSSIBLE_CHILDREN,
 								configElement.getDeclaringExtension()
 										.getUniqueIdentifier(),
 								configElement.getDeclaringExtension()
 										.getNamespace() }));
 			}
 		} else if (children.length == 1) {
 			try {
 				enablement = ElementHandler.getDefault().create(
 						ExpressionConverter.getDefault(), children[0]);
 			} catch (CoreException e) {
 				NavigatorPlugin.log(IStatus.ERROR, 0, e.getMessage(), e);
 			}
 		} else if (children.length > 1) {
 			throw new WorkbenchException(NLS.bind(
 					CommonNavigatorMessages.Attribute_Missing_Warning,
 					new Object[] {
 							TAG_ENABLEMENT,
 							configElement.getDeclaringExtension()
 									.getUniqueIdentifier(),
 							configElement.getDeclaringExtension()
 									.getNamespace() }));
 		}

 		contribution = new IPluginContribution() {

 			public String getLocalId() {
 				return configElement.getDeclaringExtension()
 						.getSimpleIdentifier();
 			}

 			public String getPluginId() {
 				return configElement.getDeclaringExtension()
 						.getUniqueIdentifier();
 			}

 		};

 		children = configElement.getChildren(TAG_DUPLICATE_CONTENT_FILTER);
 		duplicateContentFilterElements = children != null ? children
 				: NO_DUPLICATE_CONTENT_FILTERS;
 	}

 	/**
 	 * Set whether or not the receiver is a root navigator extension
 	 *
 	 * @param root
 	 *            true if the receiver is a root navigator extension. false if
 	 *            the receiver is not a root navigator extension.
 	 */
 	void setRoot(boolean root) {
 		this.root = root;
 	}

 	/**
 	 * @return Returns the icon.
 	 */
 	public String getIcon() {
 		return icon;
 	}

 	/**
 	 * @return Returns the declaringPluginId.
 	 */
 	public String getDeclaringPluginId() {
 		return declaringPluginId;
 	}

 	/*
 	 * (non-Javadoc)
 	 *
 	 * @see org.eclipse.ui.navigator.internal.extensions.INavigatorContentDescriptor#isEnabledByDefault()
 	 */
 	public boolean isEnabledByDefault() {
 		return enabledByDefault;
 	}

 	/**
 	 * @return Returns the contribution.
 	 */
 	public IPluginContribution getContribution() {
 		return contribution;
 	}

 	/*
 	 * (non-Javadoc)
 	 *
 	 * @see org.eclipse.ui.navigator.internal.extensions.INavigatorContentDescriptor#hasLoadingFailed()
 	 */
 	public boolean hasLoadingFailed() {
 		return hasLoadingFailed;
 	}

 	protected IConfigurationElement[] getDuplicateContentFilterElements() {
 		return duplicateContentFilterElements;
 	}

 	/**
 	 *
 	 * @return The duplicate content filters associated with this descriptor.
 	 */
 	public INavigatorExtensionFilter[] createDuplicateContentFilters() {

 		List viewerFiltersList = new ArrayList();
 		IConfigurationElement[] dupeFilters = getDuplicateContentFilterElements();
 		INavigatorExtensionFilter vFilter = null;
 		for (int i = 0; i < dupeFilters.length; i++) {
 			try {

 				vFilter = (INavigatorExtensionFilter) dupeFilters[i]
 						.createExecutableExtension(ATT_VIEWER_FILTER);
 				viewerFiltersList.add(vFilter);
 			} catch (CoreException e) {
 				e.printStackTrace();
 			} catch (RuntimeException e) {
 				e.printStackTrace();
 			}

 		}
 		return (INavigatorExtensionFilter[]) (viewerFiltersList.size() > 0 ? viewerFiltersList
 				.toArray(new INavigatorExtensionFilter[viewerFiltersList.size()])
 				: NO_VIEWER_FILTERS);
 	}

 	/**
 	 * The content provider could be an instance of
 	 * {@link ICommonContentProvider}, but only {@link ITreeContentProvider} is
 	 * required.
 	 *
 	 *
 	 * @return An instance of the Content provider defined for this extension.
 	 * @throws CoreException
 	 *             if an instance of the executable extension could not be
 	 *             created for any reason
 	 *
 	 */
 	public ITreeContentProvider createContentProvider() throws CoreException {
 		return (ITreeContentProvider) configElement
 				.createExecutableExtension(ATT_CONTENT_PROVIDER);
 	}

 	/**
 	 *
 	 * The content provider could be an instance of {@link ICommonLabelProvider},
 	 * but only {@link ILabelProvider} is required.
 	 *
 	 * @return An instance of the Label provider defined for this extension
 	 * @throws CoreException
 	 *             if an instance of the executable extension could not be
 	 *             created for any reason
 	 */
 	public ILabelProvider createLabelProvider() throws CoreException {
 		return (ILabelProvider) configElement
 				.createExecutableExtension(ATT_LABEL_PROVIDER);
 	}

 	/**
 	 * Extensions may or may not define a comparator. Without a comparator,
 	 * items are sorted in the same order they are returned from the content
 	 * provider.
 	 *
 	 * @return An instance of the Comparator defined for this extension
 	 * @throws CoreException
 	 *             if an instance of the executable extension could not be
 	 *             created for any reason
 	 */
 	public Comparator createComparator() throws CoreException {
 		if (configElement.getAttribute(ATT_SORTER) != null)
 			return (Comparator) configElement
 					.createExecutableExtension(ATT_SORTER);
 		return null;
 	}
 }
	/*******************************************************************************
	* Copyright (c) 2003, 2005 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.ui.navigator.internal.extensions;

	import java.util.ArrayList;
	import java.util.Comparator;
	import java.util.Iterator;
	import java.util.List;

	import org.eclipse.core.expressions.ElementHandler;
	import org.eclipse.core.expressions.EvaluationContext;
	import org.eclipse.core.expressions.EvaluationResult;
	import org.eclipse.core.expressions.Expression;
	import org.eclipse.core.expressions.ExpressionConverter;
	import org.eclipse.core.expressions.IEvaluationContext;
	import org.eclipse.core.runtime.CoreException;
	import org.eclipse.core.runtime.IConfigurationElement;
	import org.eclipse.core.runtime.IStatus;
	import org.eclipse.jface.viewers.ILabelProvider;
	import org.eclipse.jface.viewers.IStructuredSelection;
	import org.eclipse.jface.viewers.ITreeContentProvider;
	import org.eclipse.osgi.util.NLS;
	import org.eclipse.ui.IPluginContribution;
	import org.eclipse.ui.WorkbenchException;
	import org.eclipse.ui.navigator.ICommonContentProvider;
	import org.eclipse.ui.navigator.ICommonLabelProvider;
	import org.eclipse.ui.navigator.INavigatorContentDescriptor;
	import org.eclipse.ui.navigator.INavigatorExtensionFilter;
	import org.eclipse.ui.navigator.Priority;
	import org.eclipse.ui.navigator.internal.CommonNavigatorMessages;
	import org.eclipse.ui.navigator.internal.CustomAndExpression;
	import org.eclipse.ui.navigator.internal.NavigatorPlugin;

	/**
	* Encapsulates the <code>org.eclipse.ui.navigator.navigatorContent</code>
	* extension point.
	* <p>
	* <strong>EXPERIMENTAL</strong>. This class or interface has been added as
	* part of a work in progress. There is a guarantee neither that this API will
	* work nor that it will remain the same. Please do not use this API without
	* consulting with the Platform/UI team.
	* </p>
	*
	* @since 3.2
	*/
	public final class NavigatorContentDescriptor implements
	INavigatorContentDescriptor, INavigatorContentExtPtConstants {

	private static final INavigatorExtensionFilter[] NO_VIEWER_FILTERS = new INavigatorExtensionFilter[0];

	private static final IConfigurationElement[] NO_DUPLICATE_CONTENT_FILTERS = new IConfigurationElement[0];

	private String id;

	private String name;

	private IConfigurationElement configElement;

	private String rootLabel;

	private int priority = Integer.MAX_VALUE;

	private Expression enablement;

	private Expression possibleChildren;

	private boolean root;

	private String icon;

	private String declaringPluginId;

	private boolean enabledByDefault;

	private IPluginContribution contribution;

	private boolean hasLoadingFailed;

	private IConfigurationElement[] duplicateContentFilterElements;

	/**
	* Creates a new content descriptor from a configuration element.
	*
	* @param configElement
	* configuration element to create a descriptor from
	*
	* @throws WorkbenchException
	* if the configuration element could not be parsed. Reasons
	* include:
	* <ul>
	* <li>A required attribute is missing.</li>
	* <li>More elements are define than is allowed.</li>
	* </ul>
	*/
	public NavigatorContentDescriptor(IConfigurationElement configElement)
	throws WorkbenchException {
	super();
	this.configElement = configElement;
	readConfigElement();
	}

	/**
	* Determine if this content extension is enabled for the given selection.
	* The content extension is enabled for the selection if and only if it is
	* enabled for each element in the selection.
	*
	* @param aStructuredSelection
	* The selection from the viewer
	* @return True if and only if the extension is enabled for each element in
	* the selection.
	*/
	public boolean isEnabledFor(IStructuredSelection aStructuredSelection) {
	if (enablement == null)
	return false;

	IEvaluationContext context = null;

	Iterator elements = aStructuredSelection.iterator();
	while (elements.hasNext()) {
	context = new EvaluationContext(null, elements.next());
	try {
	if (enablement.evaluate(context) == EvaluationResult.FALSE)
	return false;
	} catch (CoreException e) {
	NavigatorPlugin.log(IStatus.ERROR, 0, e.getMessage(), e);
	return false;
	}
	}
	return true;
	}

	/**
	* Determine if this content extension is enabled for the given element.
	*
	* @param anElement
	* The element that should be used for the evaluation.
	* @return True if and only if the extension is enabled for the element.
	*/
	public boolean isEnabledFor(Object anElement) {

	if (enablement == null \|\| anElement == null)
	return false;

	try {
	return (enablement.evaluate(new EvaluationContext(null, anElement)) == EvaluationResult.TRUE);
	} catch (CoreException e) {
	NavigatorPlugin.log(IStatus.ERROR, 0, e.getMessage(), e);
	}
	return false;
	}

	/**
	* Determine if this content extension could provide the given element as a
	* child.
	*
	* <p>
	* This method is used to determine what the parent of an element could be
	* for Link with Editor support.
	* </p>
	*
	* @param anElement
	* The element that should be used for the evaluation.
	* @return True if and only if the extension might provide an object of this
	* type as a child.
	*/
	public boolean isPossibleChild(Object anElement) {

	if ((enablement == null && possibleChildren == null)
	\|\| anElement == null)
	return false;

	try {
	if (possibleChildren != null)
	return (possibleChildren.evaluate(new EvaluationContext(null,
	anElement)) == EvaluationResult.TRUE);
	else if (enablement != null)
	return (enablement.evaluate(new EvaluationContext(null,
	anElement)) == EvaluationResult.TRUE);
	} catch (CoreException e) {
	NavigatorPlugin.log(IStatus.ERROR, 0, e.getMessage(), e);
	}
	return false;
	}

	/*
	* (non-Javadoc)
	*
	* @see org.eclipse.ui.navigator.internal.extensions.INavigatorContentDescriptor#getId()
	*/
	public String getId() {
	return id;
	}

	/*
	* (non-Javadoc)
	*
	* @see org.eclipse.ui.navigator.internal.extensions.INavigatorContentDescriptor#getName()
	*/
	public String getName() {
	return name;
	}

	/*
	* (non-Javadoc)
	*
	* @see org.eclipse.ui.navigator.internal.extensions.INavigatorContentDescriptor#getPriority()
	*/
	public int getPriority() {
	return priority;
	}

	/*
	* (non-Javadoc)
	*
	* @see org.eclipse.ui.navigator.internal.extensions.INavigatorContentDescriptor#isRoot()
	*/
	public boolean isRoot() {
	return root;
	}

	/**
	* @return a label to be used to delay the loading -- used for a content
	* extension that contributes a single root element
	*
	*/
	protected String getRootLabel() {
	return rootLabel;
	}

	/**
	* Parses the configuration element.
	*
	* @throws WorkbenchException
	* if the configuration element could not be parsed. Reasons
	* include:
	* <ul>
	* <li>A required attribute is missing.</li>
	* <li>More elements are define than is allowed.</li>
	* </ul>
	*/
	void readConfigElement() throws WorkbenchException {
	id = configElement.getAttribute(ATT_ID);
	name = configElement.getAttribute(ATT_NAME);
	String priorityString = configElement.getAttribute(ATT_PRIORITY);
	icon = configElement.getAttribute(ATT_ICON);
	rootLabel = configElement.getAttribute(ATT_ROOT_LABEL);

	declaringPluginId = configElement.getDeclaringExtension()
	.getNamespace();
	String enabledByDefaultString = configElement
	.getAttribute(ATT_ACTIVE_BY_DEFAULT);
	enabledByDefault = (enabledByDefaultString != null && enabledByDefaultString
	.length() > 0) ? Boolean.valueOf(
	configElement.getAttribute(ATT_ACTIVE_BY_DEFAULT))
	.booleanValue() : true;

	if (priorityString != null) {
	try {
	Priority p = Priority.get(priorityString);
	priority = p != null ? p.getValue() : -1;
	} catch (NumberFormatException exception) {
	}
	}
	if (id == null) {
	throw new WorkbenchException(NLS.bind(
	CommonNavigatorMessages.Attribute_Missing_Warning,
	new Object[] {
	ATT_ID,
	configElement.getDeclaringExtension()
	.getUniqueIdentifier(),
	configElement.getDeclaringExtension()
	.getNamespace() }));
	}

	IConfigurationElement[] children = configElement
	.getChildren(TAG_ENABLEMENT);
	if (children.length == 0) {

	children = configElement.getChildren(TAG_TRIGGER_POINTS);
	if (children.length == 1) {
	enablement = new CustomAndExpression(children[0]);
	} else if (children.length > 1) {
	throw new WorkbenchException(NLS.bind(
	CommonNavigatorMessages.Attribute_Missing_Warning,
	new Object[] {
	TAG_TRIGGER_POINTS,
	configElement.getDeclaringExtension()
	.getUniqueIdentifier(),
	configElement.getDeclaringExtension()
	.getNamespace() }));
	}

	children = configElement.getChildren(TAG_POSSIBLE_CHILDREN);
	if (children.length == 1) {
	possibleChildren = new CustomAndExpression(children[0]);
	} else if (children.length > 1) {
	throw new WorkbenchException(NLS.bind(
	CommonNavigatorMessages.Attribute_Missing_Warning,
	new Object[] {
	TAG_POSSIBLE_CHILDREN,
	configElement.getDeclaringExtension()
	.getUniqueIdentifier(),
	configElement.getDeclaringExtension()
	.getNamespace() }));
	}
	} else if (children.length == 1) {
	try {
	enablement = ElementHandler.getDefault().create(
	ExpressionConverter.getDefault(), children[0]);
	} catch (CoreException e) {
	NavigatorPlugin.log(IStatus.ERROR, 0, e.getMessage(), e);
	}
	} else if (children.length > 1) {
	throw new WorkbenchException(NLS.bind(
	CommonNavigatorMessages.Attribute_Missing_Warning,
	new Object[] {
	TAG_ENABLEMENT,
	configElement.getDeclaringExtension()
	.getUniqueIdentifier(),
	configElement.getDeclaringExtension()
	.getNamespace() }));
	}

	contribution = new IPluginContribution() {

	public String getLocalId() {
	return configElement.getDeclaringExtension()
	.getSimpleIdentifier();
	}

	public String getPluginId() {
	return configElement.getDeclaringExtension()
	.getUniqueIdentifier();
	}

	};

	children = configElement.getChildren(TAG_DUPLICATE_CONTENT_FILTER);
	duplicateContentFilterElements = children != null ? children
	: NO_DUPLICATE_CONTENT_FILTERS;
	}

	/**
	* Set whether or not the receiver is a root navigator extension
	*
	* @param root
	* true if the receiver is a root navigator extension. false if
	* the receiver is not a root navigator extension.
	*/
	void setRoot(boolean root) {
	this.root = root;
	}

	/**
	* @return Returns the icon.
	*/
	public String getIcon() {
	return icon;
	}

	/**
	* @return Returns the declaringPluginId.
	*/
	public String getDeclaringPluginId() {
	return declaringPluginId;
	}

	/*
	* (non-Javadoc)
	*
	* @see org.eclipse.ui.navigator.internal.extensions.INavigatorContentDescriptor#isEnabledByDefault()
	*/
	public boolean isEnabledByDefault() {
	return enabledByDefault;
	}

	/**
	* @return Returns the contribution.
	*/
	public IPluginContribution getContribution() {
	return contribution;
	}

	/*
	* (non-Javadoc)
	*
	* @see org.eclipse.ui.navigator.internal.extensions.INavigatorContentDescriptor#hasLoadingFailed()
	*/
	public boolean hasLoadingFailed() {
	return hasLoadingFailed;
	}

	protected IConfigurationElement[] getDuplicateContentFilterElements() {
	return duplicateContentFilterElements;
	}

	/**
	*
	* @return The duplicate content filters associated with this descriptor.
	*/
	public INavigatorExtensionFilter[] createDuplicateContentFilters() {

	List viewerFiltersList = new ArrayList();
	IConfigurationElement[] dupeFilters = getDuplicateContentFilterElements();
	INavigatorExtensionFilter vFilter = null;
	for (int i = 0; i < dupeFilters.length; i++) {
	try {

	vFilter = (INavigatorExtensionFilter) dupeFilters[i]
	.createExecutableExtension(ATT_VIEWER_FILTER);
	viewerFiltersList.add(vFilter);
	} catch (CoreException e) {
	e.printStackTrace();
	} catch (RuntimeException e) {
	e.printStackTrace();
	}

	}
	return (INavigatorExtensionFilter[]) (viewerFiltersList.size() > 0 ? viewerFiltersList
	.toArray(new INavigatorExtensionFilter[viewerFiltersList.size()])
	: NO_VIEWER_FILTERS);
	}

	/**
	* The content provider could be an instance of
	* {@link ICommonContentProvider}, but only {@link ITreeContentProvider} is
	* required.
	*
	*
	* @return An instance of the Content provider defined for this extension.
	* @throws CoreException
	* if an instance of the executable extension could not be
	* created for any reason
	*
	*/
	public ITreeContentProvider createContentProvider() throws CoreException {
	return (ITreeContentProvider) configElement
	.createExecutableExtension(ATT_CONTENT_PROVIDER);
	}

	/**
	*
	* The content provider could be an instance of {@link ICommonLabelProvider},
	* but only {@link ILabelProvider} is required.
	*
	* @return An instance of the Label provider defined for this extension
	* @throws CoreException
	* if an instance of the executable extension could not be
	* created for any reason
	*/
	public ILabelProvider createLabelProvider() throws CoreException {
	return (ILabelProvider) configElement
	.createExecutableExtension(ATT_LABEL_PROVIDER);
	}

	/**
	* Extensions may or may not define a comparator. Without a comparator,
	* items are sorted in the same order they are returned from the content
	* provider.
	*
	* @return An instance of the Comparator defined for this extension
	* @throws CoreException
	* if an instance of the executable extension could not be
	* created for any reason
	*/
	public Comparator createComparator() throws CoreException {
	if (configElement.getAttribute(ATT_SORTER) != null)
	return (Comparator) configElement
	.createExecutableExtension(ATT_SORTER);
	return null;
	}
	}