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.configuration2.tree; 018 019/** 020 * <p> 021 * Definition of a <em>Visitor</em> interface for a configuration node 022 * structure. 023 * </p> 024 * <p> 025 * This is a typical application of the GoF <em>Visitor</em> pattern. An object 026 * implementing this interface can be used to traverse a hierarchical structure 027 * of nodes in various ways. The type of the nodes in the structure is generic; 028 * a corresponding {@link NodeHandler} implementation must be available for 029 * navigating through the structure. 030 * </p> 031 * <p> 032 * Note that the exact way the methods of a {@code ConfigurationNodeVisitor} are 033 * invoked is dependent on a specific traversal process. 034 * </p> 035 * 036 * @since 1.3 037 * @param <T> the type of the nodes processed by this visitor 038 */ 039public interface ConfigurationNodeVisitor<T> 040{ 041 /** 042 * Visits the specified node before the children of this node - if existing 043 * - are processed. 044 * 045 * @param node the node to be visited 046 * @param handler the {@code NodeHandler} 047 */ 048 void visitBeforeChildren(T node, NodeHandler<T> handler); 049 050 /** 051 * Visits the specified node after after its children - if existing - have 052 * been processed. 053 * 054 * @param node the node to be visited 055 * @param handler the {@code NodeHandler} 056 */ 057 void visitAfterChildren(T node, NodeHandler<T> handler); 058 059 /** 060 * Returns a flag whether the current visit process should be aborted. This 061 * method allows a visitor implementation to state that it does not need any 062 * further data. It may be used e.g. by visitors that search for a certain 063 * node in the hierarchy. After that node was found, there is no need to 064 * process the remaining nodes, too. This method is called after each 065 * visited node. A result of <strong>true</strong> indicates that the 066 * current iteration is to be aborted. 067 * 068 * @return a flag if the visit process should be stopped 069 */ 070 boolean terminate(); 071}