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 java.util.function.Consumer;
22
23 import org.eclipse.aether.ConfigurationProperties;
24 import org.eclipse.aether.graph.DependencyFilter;
25 import org.eclipse.aether.graph.DependencyNode;
26
27 /**
28 * Processes dependency graph by traversing the graph in postorder. This visitor visits each node exactly once
29 * regardless how many paths within the dependency graph lead to the node such that the resulting node sequence is
30 * free of duplicates.
31 * <p>
32 * <strong>Instances of this class cannot be embedded into {@link FilteringDependencyVisitor}</strong>, pass in the
33 * filter {@link DependencyFilter} into constructor instead.
34 *
35 * @see NodeListGenerator
36 * @since 2.0.0
37 */
38 public final class PostorderDependencyNodeConsumerVisitor extends AbstractDependencyNodeConsumerVisitor {
39
40 public static final String NAME = ConfigurationProperties.REPOSITORY_SYSTEM_DEPENDENCY_VISITOR_POSTORDER;
41
42 private final Stack<Boolean> visits;
43
44 /**
45 * Creates a new postorder list generator.
46 */
47 public PostorderDependencyNodeConsumerVisitor(Consumer<DependencyNode> nodeConsumer) {
48 this(nodeConsumer, null);
49 }
50
51 /**
52 * Creates a new postorder list generator.
53 *
54 * @since 2.0.12
55 */
56 public PostorderDependencyNodeConsumerVisitor(Consumer<DependencyNode> nodeConsumer, DependencyFilter filter) {
57 super(nodeConsumer, filter);
58 visits = new Stack<>();
59 }
60
61 @Override
62 protected boolean doVisitEnter(DependencyNode node) {
63 boolean visited = !setVisited(node);
64 visits.push(visited);
65 return !visited;
66 }
67
68 @Override
69 protected boolean doVisitLeave(DependencyNode node) {
70 Boolean visited = visits.pop();
71 if (visited) {
72 return true;
73 }
74 if (acceptNode(node)) {
75 consumeNode(node);
76 }
77 return true;
78 }
79 }