001/*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements.  See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License.  You may obtain a copy of the License at
008 *
009 *     http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017package org.apache.commons.configuration.tree;
018
019/**
020 * <p>
021 * Definition of a <em>Visitor</em> interface for a configuration node
022 * structure.
023 * </p>
024 * <p>
025 * The {@code ConfigurationNode} interface defines a {@code visit()},
026 * which simplifies traversal of a complex node hierarchy. A configuration node
027 * implementation must provide a way of visiting all nodes in the current
028 * hierarchy. This is a typical application of the GoF <em>Visitor</em>
029 * pattern.
030 * </p>
031 *
032 * @since 1.3
033 * @see ConfigurationNode
034 * @author <a
035 * href="http://commons.apache.org/configuration/team-list.html">Commons
036 * Configuration team</a>
037 * @version $Id: ConfigurationNodeVisitor.java 1206463 2011-11-26 15:47:08Z oheger $
038 */
039public interface ConfigurationNodeVisitor
040{
041    /**
042     * Visits the specified node. This method is called before eventually
043     * existing children of this node are processed.
044     *
045     * @param node the node to be visited
046     */
047    void visitBeforeChildren(ConfigurationNode node);
048
049    /**
050     * Visits the specified node. This method is called after eventually
051     * existing children of this node have been processed.
052     *
053     * @param node the node to be visited
054     */
055    void visitAfterChildren(ConfigurationNode node);
056
057    /**
058     * Returns a flag whether the actual visit process should be aborted. This
059     * method allows a visitor implementation to state that it does not need any
060     * further data. It may be used e.g. by visitors that search for a certain
061     * node in the hierarchy. After that node was found, there is no need to
062     * process the remaining nodes, too.
063     *
064     * @return a flag if the visit process should be stopped
065     */
066    boolean terminate();
067}