| /* |
| * Licensed to the Apache Software Foundation (ASF) under one |
| * or more contributor license agreements. See the NOTICE file |
| * distributed with this work for additional information |
| * regarding copyright ownership. The ASF licenses this file |
| * to you under the Apache License, Version 2.0 (the |
| * "License"); you may not use this file except in compliance |
| * with the License. You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, |
| * software distributed under the License is distributed on an |
| * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY |
| * KIND, either express or implied. See the License for the |
| * specific language governing permissions and limitations |
| * under the License. |
| */ |
| package org.eclipse.aether.util.graph.visitor; |
| |
| import java.util.IdentityHashMap; |
| import java.util.Map; |
| |
| import org.eclipse.aether.graph.DependencyNode; |
| import org.eclipse.aether.graph.DependencyVisitor; |
| |
| import static java.util.Objects.requireNonNull; |
| |
| /** |
| * A dependency visitor that delegates to another visitor if a node hasn't been visited before. In other words, this |
| * visitor provides a tree-view of a dependency graph which generally can have multiple paths to the same node or even |
| * cycles. |
| */ |
| public final class TreeDependencyVisitor implements DependencyVisitor { |
| |
| private final Map<DependencyNode, Object> visitedNodes; |
| |
| private final DependencyVisitor visitor; |
| |
| private final Stack<Boolean> visits; |
| |
| /** |
| * Creates a new visitor that delegates to the specified visitor. |
| * |
| * @param visitor The visitor to delegate to, must not be {@code null}. |
| */ |
| public TreeDependencyVisitor(DependencyVisitor visitor) { |
| this.visitor = requireNonNull(visitor, "dependency visitor delegate cannot be null"); |
| visitedNodes = new IdentityHashMap<>(512); |
| visits = new Stack<>(); |
| } |
| |
| @Override |
| public boolean visitEnter(DependencyNode node) { |
| boolean visited = visitedNodes.put(node, Boolean.TRUE) != null; |
| |
| visits.push(visited); |
| |
| if (visited) { |
| return false; |
| } |
| |
| return visitor.visitEnter(node); |
| } |
| |
| @Override |
| public boolean visitLeave(DependencyNode node) { |
| Boolean visited = visits.pop(); |
| |
| if (visited) { |
| return true; |
| } |
| |
| return visitor.visitLeave(node); |
| } |
| } |