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 * @version $Id: ConfigurationNodeVisitor.java 1624601 2014-09-12 18:04:36Z oheger $ 038 * @param <T> the type of the nodes processed by this visitor 039 */ 040public interface ConfigurationNodeVisitor<T> 041{ 042 /** 043 * Visits the specified node before the children of this node - if existing 044 * - are processed. 045 * 046 * @param node the node to be visited 047 * @param handler the {@code NodeHandler} 048 */ 049 void visitBeforeChildren(T node, NodeHandler<T> handler); 050 051 /** 052 * Visits the specified node after after its children - if existing - have 053 * been processed. 054 * 055 * @param node the node to be visited 056 * @param handler the {@code NodeHandler} 057 */ 058 void visitAfterChildren(T node, NodeHandler<T> handler); 059 060 /** 061 * Returns a flag whether the current visit process should be aborted. This 062 * method allows a visitor implementation to state that it does not need any 063 * further data. It may be used e.g. by visitors that search for a certain 064 * node in the hierarchy. After that node was found, there is no need to 065 * process the remaining nodes, too. This method is called after each 066 * visited node. A result of <strong>true</strong> indicates that the 067 * current iteration is to be aborted. 068 * 069 * @return a flag if the visit process should be stopped 070 */ 071 boolean terminate(); 072}