1 package org.eclipse.aether.util.graph.visitor;
2
3 /*
4 * Licensed to the Apache Software Foundation (ASF) under one
5 * or more contributor license agreements. See the NOTICE file
6 * distributed with this work for additional information
7 * regarding copyright ownership. The ASF licenses this file
8 * to you under the Apache License, Version 2.0 (the
9 * "License"); you may not use this file except in compliance
10 * with the License. You may obtain a copy of the License at
11 *
12 * http://www.apache.org/licenses/LICENSE-2.0
13 *
14 * Unless required by applicable law or agreed to in writing,
15 * software distributed under the License is distributed on an
16 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
17 * KIND, either express or implied. See the License for the
18 * specific language governing permissions and limitations
19 * under the License.
20 */
21
22 import static java.util.Objects.requireNonNull;
23
24 import org.eclipse.aether.graph.DependencyFilter;
25 import org.eclipse.aether.graph.DependencyNode;
26 import org.eclipse.aether.graph.DependencyVisitor;
27
28 /**
29 * A dependency visitor that delegates to another visitor if nodes match a filter. Note that in case of a mismatching
30 * node, the children of that node are still visisted and presented to the filter.
31 */
32 public final class FilteringDependencyVisitor
33 implements DependencyVisitor
34 {
35
36 private final DependencyFilter filter;
37
38 private final DependencyVisitor visitor;
39
40 private final Stack<Boolean> accepts;
41
42 private final Stack<DependencyNode> parents;
43
44 /**
45 * Creates a new visitor that delegates traversal of nodes matching the given filter to the specified visitor.
46 *
47 * @param visitor The visitor to delegate to, must not be {@code null}.
48 * @param filter The filter to apply, may be {@code null} to not filter.
49 */
50 public FilteringDependencyVisitor( DependencyVisitor visitor, DependencyFilter filter )
51 {
52 this.visitor = requireNonNull( visitor, "dependency visitor delegate cannot be null" );
53 this.filter = filter;
54 this.accepts = new Stack<>();
55 this.parents = new Stack<>();
56 }
57
58 /**
59 * Gets the visitor to which this visitor delegates to.
60 *
61 * @return The visitor being delegated to, never {@code null}.
62 */
63 public DependencyVisitor getVisitor()
64 {
65 return visitor;
66 }
67
68 /**
69 * Gets the filter being applied before delegation.
70 *
71 * @return The filter being applied or {@code null} if none.
72 */
73 public DependencyFilter getFilter()
74 {
75 return filter;
76 }
77
78 public boolean visitEnter( DependencyNode node )
79 {
80 boolean accept = filter == null || filter.accept( node, parents );
81
82 accepts.push( accept );
83
84 parents.push( node );
85
86 if ( accept )
87 {
88 return visitor.visitEnter( node );
89 }
90 else
91 {
92 return true;
93 }
94 }
95
96 public boolean visitLeave( DependencyNode node )
97 {
98 parents.pop();
99
100 Boolean accept = accepts.pop();
101
102 if ( accept )
103 {
104 return visitor.visitLeave( node );
105 }
106 else
107 {
108 return true;
109 }
110 }
111
112 }