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.IdentityHashMap;
22 import java.util.Map;
23
24 import org.eclipse.aether.graph.DefaultDependencyNode;
25 import org.eclipse.aether.graph.DependencyNode;
26 import org.eclipse.aether.graph.DependencyVisitor;
27
28 /**
29 * A dependency visitor that constructs a clone of the visited dependency graph. If such a visitor is passed into a
30 * {@link FilteringDependencyVisitor}, a sub graph can be created. This class creates shallow clones of the visited
31 * dependency nodes (via {@link DefaultDependencyNode#DefaultDependencyNode(DependencyNode)}) but clients can create a
32 * subclass and override {@link #clone(DependencyNode)} to alter the clone process.
33 */
34 public class CloningDependencyVisitor implements DependencyVisitor {
35
36 private final Map<DependencyNode, DependencyNode> clones;
37
38 private final Stack<DependencyNode> parents;
39
40 private DependencyNode root;
41
42 /**
43 * Creates a new visitor that clones the visited nodes.
44 */
45 public CloningDependencyVisitor() {
46 parents = new Stack<>();
47 clones = new IdentityHashMap<>(256);
48 }
49
50 /**
51 * Gets the root node of the cloned dependency graph.
52 *
53 * @return The root node of the cloned dependency graph or {@code null}.
54 */
55 public final DependencyNode getRootNode() {
56 return root;
57 }
58
59 /**
60 * Creates a clone of the specified node.
61 *
62 * @param node The node to clone, must not be {@code null}.
63 * @return The cloned node, never {@code null}.
64 */
65 protected DependencyNode clone(DependencyNode node) {
66 return new DefaultDependencyNode(node);
67 }
68
69 @Override
70 public final boolean visitEnter(DependencyNode node) {
71 boolean recurse = true;
72
73 DependencyNode clone = clones.get(node);
74 if (clone == null) {
75 clone = clone(node);
76 clones.put(node, clone);
77 } else {
78 recurse = false;
79 }
80
81 DependencyNode parent = parents.peek();
82
83 if (parent == null) {
84 root = clone;
85 } else {
86 parent.getChildren().add(clone);
87 }
88
89 parents.push(clone);
90
91 return recurse;
92 }
93
94 @Override
95 public final boolean visitLeave(DependencyNode node) {
96 parents.pop();
97
98 return true;
99 }
100 }