1 /* 2 * Licensed to the Apache Software Foundation (ASF) under one 3 * or more contributor license agreements. See the NOTICE file 4 * distributed with this work for additional information 5 * regarding copyright ownership. The ASF licenses this file 6 * to you under the Apache License, Version 2.0 (the 7 * "License"); you may not use this file except in compliance 8 * with the License. You may obtain a copy of the License at 9 * 10 * http://www.apache.org/licenses/LICENSE-2.0 11 * 12 * Unless required by applicable law or agreed to in writing, 13 * software distributed under the License is distributed on an 14 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY 15 * KIND, either express or implied. See the License for the 16 * specific language governing permissions and limitations 17 * under the License. 18 */ 19 package org.eclipse.aether.util.graph.visitor; 20 21 import org.eclipse.aether.graph.DependencyNode; 22 23 /** 24 * Generates a sequence of dependency nodes from a dependency graph by traversing the graph in preorder. This visitor 25 * visits each node exactly once regardless how many paths within the dependency graph lead to the node such that the 26 * resulting node sequence is free of duplicates. 27 * <p> 28 * The newer classes {@link AbstractDependencyNodeConsumerVisitor} and {@link NodeListGenerator} offer 29 * similar capabilities but are pluggable. Use of this class, while not deprecated, is discouraged. This class 30 * is not used in Resolver and is kept only for backward compatibility reasons. 31 * 32 * @see PreorderDependencyNodeConsumerVisitor 33 * @see NodeListGenerator 34 */ 35 public final class PreorderNodeListGenerator extends AbstractDepthFirstNodeListGenerator { 36 37 /** 38 * Creates a new preorder list generator. 39 */ 40 public PreorderNodeListGenerator() {} 41 42 @Override 43 public boolean visitEnter(DependencyNode node) { 44 if (!setVisited(node)) { 45 return false; 46 } 47 48 if (node.getDependency() != null) { 49 nodes.add(node); 50 } 51 52 return true; 53 } 54 55 @Override 56 public boolean visitLeave(DependencyNode node) { 57 return true; 58 } 59 }