001/* 002 * Licensed to the Apache Software Foundation (ASF) under one 003 * or more contributor license agreements. See the NOTICE file 004 * distributed with this work for additional information 005 * regarding copyright ownership. The ASF licenses this file 006 * to you under the Apache License, Version 2.0 (the 007 * "License"); you may not use this file except in compliance 008 * with the License. You may obtain a copy of the License at 009 * 010 * http://www.apache.org/licenses/LICENSE-2.0 011 * 012 * Unless required by applicable law or agreed to in writing, 013 * software distributed under the License is distributed on an 014 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY 015 * KIND, either express or implied. See the License for the 016 * specific language governing permissions and limitations 017 * under the License. 018 */ 019package org.eclipse.aether.util.graph.visitor; 020 021import org.eclipse.aether.graph.DependencyNode; 022 023/** 024 * Generates a sequence of dependency nodes from a dependency graph by traversing the graph in postorder. This visitor 025 * visits each node exactly once regardless how many paths within the dependency graph lead to the node such that the 026 * resulting node sequence is free of duplicates. 027 * <p> 028 * The newer classes {@link AbstractDependencyNodeConsumerVisitor} and {@link NodeListGenerator} offer 029 * similar capabilities but are pluggable. Use of this class, while not deprecated, is discouraged. This class 030 * is not used in Resolver and is kept only for backward compatibility reasons. 031 * 032 * @see PostorderDependencyNodeConsumerVisitor 033 * @see NodeListGenerator 034 */ 035public final class PostorderNodeListGenerator extends AbstractDepthFirstNodeListGenerator { 036 037 private final Stack<Boolean> visits; 038 039 /** 040 * Creates a new postorder list generator. 041 */ 042 public PostorderNodeListGenerator() { 043 visits = new Stack<>(); 044 } 045 046 @Override 047 public boolean visitEnter(DependencyNode node) { 048 boolean visited = !setVisited(node); 049 050 visits.push(visited); 051 052 return !visited; 053 } 054 055 @Override 056 public boolean visitLeave(DependencyNode node) { 057 Boolean visited = visits.pop(); 058 059 if (visited) { 060 return true; 061 } 062 063 if (node.getDependency() != null) { 064 nodes.add(node); 065 } 066 067 return true; 068 } 069}