1 /* 2 * Licensed to the Apache Software Foundation (ASF) under one or more 3 * contributor license agreements. See the NOTICE file distributed with 4 * this work for additional information regarding copyright ownership. 5 * The ASF licenses this file to You under the Apache License, Version 2.0 6 * (the "License"); you may not use this file except in compliance with 7 * the License. You may obtain a copy of the License at 8 * 9 * http://www.apache.org/licenses/LICENSE-2.0 10 * 11 * Unless required by applicable law or agreed to in writing, software 12 * distributed under the License is distributed on an "AS IS" BASIS, 13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 14 * See the License for the specific language governing permissions and 15 * limitations under the License. 16 */ 17 package org.apache.commons.configuration2.tree; 18 19 /** 20 * <p> 21 * Definition of a <em>Visitor</em> interface for a configuration node structure. 22 * </p> 23 * <p> 24 * This is a typical application of the GoF <em>Visitor</em> pattern. An object implementing this interface can be used 25 * to traverse a hierarchical structure of nodes in various ways. The type of the nodes in the structure is generic; a 26 * corresponding {@link NodeHandler} implementation must be available for navigating through the structure. 27 * </p> 28 * <p> 29 * Note that the exact way the methods of a {@code ConfigurationNodeVisitor} are invoked is dependent on a specific 30 * traversal process. 31 * </p> 32 * 33 * @since 1.3 34 * @param <T> the type of the nodes processed by this visitor 35 */ 36 public interface ConfigurationNodeVisitor<T> { 37 /** 38 * Returns a flag whether the current visit process should be aborted. This method allows a visitor implementation to 39 * state that it does not need any further data. It may be used e.g. by visitors that search for a certain node in the 40 * hierarchy. After that node was found, there is no need to process the remaining nodes, too. This method is called 41 * after each visited node. A result of <strong>true</strong> indicates that the current iteration is to be aborted. 42 * 43 * @return a flag if the visit process should be stopped 44 */ 45 boolean terminate(); 46 47 /** 48 * Visits the specified node after after its children - if existing - have been processed. 49 * 50 * @param node the node to be visited 51 * @param handler the {@code NodeHandler} 52 */ 53 void visitAfterChildren(T node, NodeHandler<T> handler); 54 55 /** 56 * Visits the specified node before the children of this node - if existing - are processed. 57 * 58 * @param node the node to be visited 59 * @param handler the {@code NodeHandler} 60 */ 61 void visitBeforeChildren(T node, NodeHandler<T> handler); 62 }