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     */
017    package 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     */
039    public 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    }