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 019import java.util.ArrayList; 020import java.util.HashMap; 021import java.util.LinkedList; 022import java.util.List; 023import java.util.Map; 024 025import org.apache.commons.lang3.ObjectUtils; 026 027/** 028 * <p> 029 * A specialized implementation of the {@code NodeCombiner} interface 030 * that performs a merge from two passed in node hierarchies. 031 * </p> 032 * <p> 033 * This combiner performs the merge using a few rules: 034 * </p> 035 * <ol> 036 * <li>Nodes can be merged when attributes that appear in both have the same value.</li> 037 * <li>Only a single node in the second file is considered a match to the node in the first file.</li> 038 * <li>Attributes in nodes that match are merged. 039 * <li>Nodes in both files that do not match are added to the result.</li> 040 * </ol> 041 * 042 * @version $Id: MergeCombiner.java 1790899 2017-04-10 21:56:46Z ggregory $ 043 * @since 1.7 044 */ 045public class MergeCombiner extends NodeCombiner 046{ 047 /** 048 * Combines the given nodes to a new union node. 049 * 050 * @param node1 the first source node 051 * @param node2 the second source node 052 * @return the union node 053 */ 054 055 @Override 056 public ImmutableNode combine(ImmutableNode node1, ImmutableNode node2) 057 { 058 ImmutableNode.Builder result = new ImmutableNode.Builder(); 059 result.name(node1.getNodeName()); 060 result.value(node1.getValue()); 061 addAttributes(result, node1, node2); 062 063 // Check if nodes can be combined 064 List<ImmutableNode> children2 = new LinkedList<>(node2.getChildren()); 065 for (ImmutableNode child1 : node1.getChildren()) 066 { 067 ImmutableNode child2 = canCombine(node2, child1, children2); 068 if (child2 != null) 069 { 070 result.addChild(combine(child1, child2)); 071 children2.remove(child2); 072 } 073 else 074 { 075 result.addChild(child1); 076 } 077 } 078 079 // Add remaining children of node 2 080 for (ImmutableNode c : children2) 081 { 082 result.addChild(c); 083 } 084 return result.create(); 085 } 086 087 /** 088 * Handles the attributes during a combination process. First all attributes 089 * of the first node will be added to the result. Then all attributes of the 090 * second node, which are not contained in the first node, will also be 091 * added. 092 * 093 * @param result the builder for the resulting node 094 * @param node1 the first node 095 * @param node2 the second node 096 */ 097 protected void addAttributes(ImmutableNode.Builder result, ImmutableNode node1, 098 ImmutableNode node2) 099 { 100 Map<String, Object> attributes = new HashMap<>(); 101 attributes.putAll(node1.getAttributes()); 102 for (Map.Entry<String, Object> e : node2.getAttributes().entrySet()) 103 { 104 if (!attributes.containsKey(e.getKey())) 105 { 106 attributes.put(e.getKey(), e.getValue()); 107 } 108 } 109 result.addAttributes(attributes); 110 } 111 112 /** 113 * Tests if the first node can be combined with the second node. A node can 114 * only be combined if its attributes are all present in the second node and 115 * they all have the same value. 116 * 117 * @param node2 the second node 118 * @param child the child node (of the first node) 119 * @param children2 the children of the 2nd node 120 * @return a child of the second node, with which a combination is possible 121 */ 122 protected ImmutableNode canCombine(ImmutableNode node2, 123 ImmutableNode child, List<ImmutableNode> children2) 124 { 125 Map<String, Object> attrs1 = child.getAttributes(); 126 List<ImmutableNode> nodes = new ArrayList<>(); 127 128 List<ImmutableNode> children = 129 HANDLER.getChildren(node2, child.getNodeName()); 130 for (ImmutableNode node : children) 131 { 132 if (matchAttributes(attrs1, node)) 133 { 134 nodes.add(node); 135 } 136 } 137 138 if (nodes.size() == 1) 139 { 140 return nodes.get(0); 141 } 142 if (nodes.size() > 1 && !isListNode(child)) 143 { 144 for (ImmutableNode node : nodes) 145 { 146 children2.remove(node); 147 } 148 } 149 150 return null; 151 } 152 153 /** 154 * Checks whether the attributes of the passed in node are compatible. 155 * 156 * @param attrs1 the attributes of the first node 157 * @param node the 2nd node 158 * @return a flag whether these nodes can be combined regarding their 159 * attributes 160 */ 161 private static boolean matchAttributes(Map<String, Object> attrs1, 162 ImmutableNode node) 163 { 164 Map<String, Object> attrs2 = node.getAttributes(); 165 for (Map.Entry<String, Object> e : attrs1.entrySet()) 166 { 167 if (attrs2.containsKey(e.getKey()) 168 && !ObjectUtils 169 .equals(e.getValue(), attrs2.get(e.getKey()))) 170 { 171 return false; 172 } 173 } 174 return true; 175 } 176}