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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</code> interface defines a <code>visit()</code>,
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 Oliver Heger
35   */
36  public interface ConfigurationNodeVisitor
37  {
38      /***
39       * Visits the specified node. This method is called before eventually
40       * existing children of this node are processed.
41       *
42       * @param node the node to be visited
43       */
44      void visitBeforeChildren(ConfigurationNode node);
45  
46      /***
47       * Visits the specified node. This method is called after eventually
48       * existing children of this node have been processed.
49       *
50       * @param node the node to be visited
51       */
52      void visitAfterChildren(ConfigurationNode node);
53  
54      /***
55       * Returns a flag whether the actual visit process should be aborted. This
56       * method allows a visitor implementation to state that it does not need any
57       * further data. It may be used e.g. by visitors that search for a certain
58       * node in the hierarchy. After that node was found, there is no need to
59       * process the remaining nodes, too.
60       *
61       * @return a flag if the visit process should be stopped
62       */
63      boolean terminate();
64  }