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1   /*
2    * Licensed to the Apache Software Foundation (ASF) under one or more
3    * contributor license agreements.  See the NOTICE file distributed with
4    * this work for additional information regarding copyright ownership.
5    * The ASF licenses this file to You under the Apache License, Version 2.0
6    * (the "License"); you may not use this file except in compliance with
7    * the License.  You may obtain a copy of the License at
8    *
9    *     http://www.apache.org/licenses/LICENSE-2.0
10   *
11   * Unless required by applicable law or agreed to in writing, software
12   * distributed under the License is distributed on an "AS IS" BASIS,
13   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14   * See the License for the specific language governing permissions and
15   * limitations under the License.
16   */
17  package org.apache.commons.configuration.tree;
18  
19  /**
20   * <p>
21   * Definition of a <em>Visitor</em> interface for a configuration node
22   * structure.
23   * </p>
24   * <p>
25   * The {@code ConfigurationNode} interface defines a {@code visit()},
26   * which simplifies traversal of a complex node hierarchy. A configuration node
27   * implementation must provide a way of visiting all nodes in the current
28   * hierarchy. This is a typical application of the GoF <em>Visitor</em>
29   * pattern.
30   * </p>
31   *
32   * @since 1.3
33   * @see ConfigurationNode
34   * @author <a
35   * href="http://commons.apache.org/configuration/team-list.html">Commons
36   * Configuration team</a>
37   * @version $Id: ConfigurationNodeVisitor.java 1206463 2011-11-26 15:47:08Z oheger $
38   */
39  public interface ConfigurationNodeVisitor
40  {
41      /**
42       * Visits the specified node. This method is called before eventually
43       * existing children of this node are processed.
44       *
45       * @param node the node to be visited
46       */
47      void visitBeforeChildren(ConfigurationNode node);
48  
49      /**
50       * Visits the specified node. This method is called after eventually
51       * existing children of this node have been processed.
52       *
53       * @param node the node to be visited
54       */
55      void visitAfterChildren(ConfigurationNode node);
56  
57      /**
58       * Returns a flag whether the actual visit process should be aborted. This
59       * method allows a visitor implementation to state that it does not need any
60       * further data. It may be used e.g. by visitors that search for a certain
61       * node in the hierarchy. After that node was found, there is no need to
62       * process the remaining nodes, too.
63       *
64       * @return a flag if the visit process should be stopped
65       */
66      boolean terminate();
67  }