    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</code> interface defines a <code>visit()</code>,
    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 Oliver Heger
    035     */
    036    public interface ConfigurationNodeVisitor
    037    {
    038        /**
    039         * Visits the specified node. This method is called before eventually
    040         * existing children of this node are processed.
    041         *
    042         * @param node the node to be visited
    043         */
    044        void visitBeforeChildren(ConfigurationNode node);
    045
    046        /**
    047         * Visits the specified node. This method is called after eventually
    048         * existing children of this node have been processed.
    049         *
    050         * @param node the node to be visited
    051         */
    052        void visitAfterChildren(ConfigurationNode node);
    053
    054        /**
    055         * Returns a flag whether the actual visit process should be aborted. This
    056         * method allows a visitor implementation to state that it does not need any
    057         * further data. It may be used e.g. by visitors that search for a certain
    058         * node in the hierarchy. After that node was found, there is no need to
    059         * process the remaining nodes, too.
    060         *
    061         * @return a flag if the visit process should be stopped
    062         */
    063        boolean terminate();
    064    }