| /******************************************************************************* |
| * Copyright (c) 2000, 2004 IBM Corporation and others. |
| * All rights reserved. This program and the accompanying materials |
| * are made available under the terms of the Common Public License v1.0 |
| * which accompanies this distribution, and is available at |
| * http://www.eclipse.org/legal/cpl-v10.html |
| * |
| * Contributors: |
| * IBM Corporation - initial API and implementation |
| *******************************************************************************/ |
| package org.eclipse.core.expressions; |
| |
| import org.eclipse.core.runtime.CoreException; |
| import org.eclipse.core.runtime.IConfigurationElement; |
| import org.eclipse.core.runtime.IStatus; |
| import org.eclipse.core.runtime.Status; |
| |
| import org.eclipse.core.internal.expressions.Assert; |
| import org.eclipse.core.internal.expressions.CompositeExpression; |
| import org.eclipse.core.internal.expressions.ExpressionMessages; |
| import org.eclipse.core.internal.expressions.ExpressionPlugin; |
| |
| /** |
| * An expression converter converts an XML expression represented by an |
| * {@link IConfigurationElement} tree into a corresponding expression tree. |
| * |
| * <p> |
| * An expression converter manages a list of {@link ElementHandler}s. Element |
| * handlers are responsible to do the actual conversion. The element handlers |
| * build a chain of responsibility. |
| * </p> |
| * |
| * @since 3.0 |
| */ |
| public final class ExpressionConverter { |
| |
| private ElementHandler[] fHandlers; |
| private static final ExpressionConverter INSTANCE= new ExpressionConverter( |
| new ElementHandler[] { ElementHandler.getDefault() } ); |
| |
| /** |
| * Returns the default expression converter. The default expression converter |
| * can cope with all expression elements defined by the common expression |
| * language. |
| * |
| * @return the default expression converter |
| */ |
| public static ExpressionConverter getDefault() { |
| return INSTANCE; |
| } |
| |
| /** |
| * Creates a new expression converter with the given list of element |
| * handlers. The element handlers build a chain of responsibility |
| * meaning that the first handler in the list is first used to |
| * convert the configuration element. If this handler isn't able |
| * to convert the configuration element the next handler in the |
| * array is used. |
| * |
| * @param handlers the array of element handlers |
| */ |
| public ExpressionConverter(ElementHandler[] handlers) { |
| Assert.isNotNull(handlers); |
| fHandlers= handlers; |
| } |
| |
| /** |
| * Converts the tree of configuration elements represented by the given |
| * root element and returns a corresponding expression tree. |
| * |
| * @param root the configuration element to be converted |
| * |
| * @return the corresponding expression tree or <code>null</code> |
| * if the configuration element cannot be converted |
| * |
| * @throws CoreException if the configuration element can't be |
| * converted. Reasons include: (a) no handler is available to |
| * cope with a certain configuration element or (b) the XML |
| * expression tree is malformed. |
| */ |
| public Expression perform(IConfigurationElement root) throws CoreException { |
| for (int i= 0; i < fHandlers.length; i++) { |
| ElementHandler handler= fHandlers[i]; |
| Expression result= handler.create(this, root); |
| if (result != null) |
| return result; |
| } |
| return null; |
| } |
| |
| /* package */ void processChildren(IConfigurationElement element, CompositeExpression result) throws CoreException { |
| IConfigurationElement[] children= element.getChildren(); |
| if (children != null) { |
| for (int i= 0; i < children.length; i++) { |
| Expression child= perform(children[i]); |
| if (child == null) |
| throw new CoreException(new Status(IStatus.ERROR, ExpressionPlugin.getPluginId(), |
| IStatus.ERROR, |
| ExpressionMessages.getFormattedString( |
| "Expression.unknown_element", //$NON-NLS-1$ |
| children[i].getName()), |
| null)); |
| result.add(child); |
| } |
| } |
| } |
| } |