| /* |
| * The Apache Software License, Version 1.1 |
| * |
| * Copyright (c) 2002 The Apache Software Foundation. All rights |
| * reserved. |
| * |
| * Redistribution and use in source and binary forms, with or without |
| * modification, are permitted provided that the following conditions |
| * are met: |
| * |
| * 1. Redistributions of source code must retain the above copyright |
| * notice, this list of conditions and the following disclaimer. |
| * |
| * 2. Redistributions in binary form must reproduce the above copyright |
| * notice, this list of conditions and the following disclaimer in |
| * the documentation and/or other materials provided with the |
| * distribution. |
| * |
| * 3. The end-user documentation included with the redistribution, if |
| * any, must include the following acknowlegement: |
| * "This product includes software developed by the |
| * Apache Software Foundation (http://www.apache.org/)." |
| * Alternately, this acknowlegement may appear in the software itself, |
| * if and wherever such third-party acknowlegements normally appear. |
| * |
| * 4. The names "The Jakarta Project", "Ant", and "Apache Software |
| * Foundation" must not be used to endorse or promote products derived |
| * from this software without prior written permission. For written |
| * permission, please contact apache@apache.org. |
| * |
| * 5. Products derived from this software may not be called "Apache" |
| * nor may "Apache" appear in their names without prior written |
| * permission of the Apache Group. |
| * |
| * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED |
| * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES |
| * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE |
| * DISCLAIMED. IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR |
| * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, |
| * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT |
| * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF |
| * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND |
| * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, |
| * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT |
| * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF |
| * SUCH DAMAGE. |
| * ==================================================================== |
| * |
| * This software consists of voluntary contributions made by many |
| * individuals on behalf of the Apache Software Foundation. For more |
| * information on the Apache Software Foundation, please see |
| * <http://www.apache.org/>. |
| */ |
| package org.apache.ant.common.util; |
| import java.util.Stack; |
| |
| /** |
| * Checks for circular dependencies when visiting nodes of an object |
| * hierarchy |
| * |
| * @author <a href="mailto:conor@apache.org">Conor MacNeill</a> |
| * @created 14 January 2002 |
| */ |
| public class CircularDependencyChecker { |
| /** |
| * The activity being undertaken which checking for circular |
| * redundancies. This is used for reporting exceptions |
| */ |
| private String activity; |
| |
| /** The nodes which we are currently visiting */ |
| private Stack nodes = new Stack(); |
| |
| /** |
| * Constructor for the CircularDependencyChecker object |
| * |
| * @param activity the activity being undertaken |
| */ |
| public CircularDependencyChecker(String activity) { |
| this.activity = activity; |
| } |
| |
| /** |
| * Visit a Node to check its relationships to other nodes |
| * |
| * @param node an object which is being visited and analyzed |
| * @exception CircularDependencyException if this node is alreay being |
| * visited. |
| */ |
| public void visitNode(Object node) throws CircularDependencyException { |
| if (nodes.contains(node)) { |
| throw new CircularDependencyException(getDescription(node)); |
| } |
| nodes.push(node); |
| } |
| |
| /** |
| * Complete the examination of the node and leave. |
| * |
| * @param node an object for which the examination of relationships has |
| * been completed |
| * @exception CircularDependencyException if the given node was not |
| * expected. |
| */ |
| public void leaveNode(Object node) throws CircularDependencyException { |
| if (!nodes.pop().equals(node)) { |
| throw new CircularDependencyException("Internal error: popped " + |
| "element was unexpected"); |
| } |
| } |
| |
| /** |
| * Gets the description of the circular dependency |
| * |
| * @param endNode the node which was revisited and where the circular |
| * dependency was detected |
| * @return the description of the circular dependency |
| */ |
| private String getDescription(Object endNode) { |
| StringBuffer sb = new StringBuffer("Circular dependency while " |
| + activity + ": "); |
| sb.append(endNode); |
| Object o = null; |
| do { |
| o = nodes.pop(); |
| sb.append(" <- "); |
| sb.append(o.toString()); |
| } while (!(o.equals(endNode))); |
| |
| return new String(sb); |
| } |
| } |
| |