Coverage Report - org.apache.commons.configuration.tree.UnionCombiner
 
Classes in this File Line Coverage Branch Coverage Complexity
UnionCombiner
100%
22/22
100%
16/16
5,5
 
 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.configuration.tree;
 18  
 
 19  
 import java.util.LinkedList;
 20  
 import java.util.List;
 21  
 
 22  
 /**
 23  
  * <p>
 24  
  * A specialized implementation of the {@code NodeCombiner} interface
 25  
  * that constructs a union from two passed in node hierarchies.
 26  
  * </p>
 27  
  * <p>
 28  
  * The given source hierarchies are traversed and their nodes are added to the
 29  
  * resulting structure. Under some circumstances two nodes can be combined
 30  
  * rather than adding both. This is the case if both nodes are single children
 31  
  * (no lists) of their parents and do not have values. The corresponding check
 32  
  * is implemented in the {@code findCombineNode()} method.
 33  
  * </p>
 34  
  * <p>
 35  
  * Sometimes it is not possible for this combiner to detect whether two nodes
 36  
  * can be combined or not. Consider the following two node hierarchies:
 37  
  * </p>
 38  
  * <p>
 39  
  *
 40  
  * <pre>
 41  
  * Hierarchy 1:
 42  
  *
 43  
  * Database
 44  
  *   +--Tables
 45  
  *        +--Table
 46  
  *             +--name [users]
 47  
  *             +--fields
 48  
  *                   +--field
 49  
  *                   |    +--name [uid]
 50  
  *                   +--field
 51  
  *                   |    +--name [usrname]
 52  
  *                     ...
 53  
  * </pre>
 54  
  *
 55  
  * </p>
 56  
  * <p>
 57  
  *
 58  
  * <pre>
 59  
  * Hierarchy 2:
 60  
  *
 61  
  * Database
 62  
  *   +--Tables
 63  
  *        +--Table
 64  
  *             +--name [documents]
 65  
  *             +--fields
 66  
  *                   +--field
 67  
  *                   |    +--name [docid]
 68  
  *                   +--field
 69  
  *                   |    +--name [docname]
 70  
  *                     ...
 71  
  * </pre>
 72  
  *
 73  
  * </p>
 74  
  * <p>
 75  
  * Both hierarchies contain data about database tables. Each describes a single
 76  
  * table. If these hierarchies are to be combined, the result should probably
 77  
  * look like the following:
 78  
  * <p>
 79  
  *
 80  
  * <pre>
 81  
  * Database
 82  
  *   +--Tables
 83  
  *        +--Table
 84  
  *        |    +--name [users]
 85  
  *        |    +--fields
 86  
  *        |          +--field
 87  
  *        |          |    +--name [uid]
 88  
  *        |            ...
 89  
  *        +--Table
 90  
  *             +--name [documents]
 91  
  *             +--fields
 92  
  *                   +--field
 93  
  *                   |    +--name [docid]
 94  
  *                     ...
 95  
  * </pre>
 96  
  *
 97  
  * </p>
 98  
  * <p>
 99  
  * i.e. the {@code Tables} nodes should be combined, while the
 100  
  * {@code Table} nodes should both be added to the resulting tree. From
 101  
  * the combiner's point of view there is no difference between the
 102  
  * {@code Tables} and the {@code Table} nodes in the source trees,
 103  
  * so the developer has to help out and give a hint that the {@code Table}
 104  
  * nodes belong to a list structure. This can be done using the
 105  
  * {@code addListNode()} method; this method expects the name of a node,
 106  
  * which should be treated as a list node. So if
 107  
  * {@code addListNode("Table");} was called, the combiner knows that it
 108  
  * must not combine the {@code Table} nodes, but add it both to the
 109  
  * resulting tree.
 110  
  * </p>
 111  
  *
 112  
  * @author <a
 113  
  * href="http://commons.apache.org/configuration/team-list.html">Commons
 114  
  * Configuration team</a>
 115  
  * @version $Id: UnionCombiner.java 1206486 2011-11-26 16:41:12Z oheger $
 116  
  * @since 1.3
 117  
  */
 118  32
 public class UnionCombiner extends NodeCombiner
 119  
 {
 120  
     /**
 121  
      * Combines the given nodes to a new union node.
 122  
      *
 123  
      * @param node1 the first source node
 124  
      * @param node2 the second source node
 125  
      * @return the union node
 126  
      */
 127  
     @Override
 128  
     public ConfigurationNode combine(ConfigurationNode node1,
 129  
             ConfigurationNode node2)
 130  
     {
 131  145
         ViewNode result = createViewNode();
 132  145
         result.setName(node1.getName());
 133  145
         result.appendAttributes(node1);
 134  145
         result.appendAttributes(node2);
 135  
 
 136  
         // Check if nodes can be combined
 137  145
         List<ConfigurationNode> children2 = new LinkedList<ConfigurationNode>(node2.getChildren());
 138  145
         for (ConfigurationNode child1 : node1.getChildren())
 139  
         {
 140  671
             ConfigurationNode child2 = findCombineNode(node1, node2, child1,
 141  
                     children2);
 142  671
             if (child2 != null)
 143  
             {
 144  101
                 result.addChild(combine(child1, child2));
 145  101
                 children2.remove(child2);
 146  
             }
 147  
             else
 148  
             {
 149  570
                 result.addChild(child1);
 150  
             }
 151  671
         }
 152  
 
 153  
         // Add remaining children of node 2
 154  145
         for (ConfigurationNode c : children2)
 155  
         {
 156  194
             result.addChild(c);
 157  194
         }
 158  
 
 159  145
         return result;
 160  
     }
 161  
 
 162  
     /**
 163  
      * <p>
 164  
      * Tries to find a child node of the second source node, with which a child
 165  
      * of the first source node can be combined. During combining of the source
 166  
      * nodes an iteration over the first source node's children is performed.
 167  
      * For each child node it is checked whether a corresponding child node in
 168  
      * the second source node exists. If this is the case, these corresponding
 169  
      * child nodes are recursively combined and the result is added to the
 170  
      * combined node. This method implements the checks whether such a recursive
 171  
      * combination is possible. The actual implementation tests the following
 172  
      * conditions:
 173  
      * </p>
 174  
      * <p>
 175  
      * <ul>
 176  
      * <li>In both the first and the second source node there is only one child
 177  
      * node with the given name (no list structures).</li>
 178  
      * <li>The given name is not in the list of known list nodes, i.e. it was
 179  
      * not passed to the {@code addListNode()} method.</li>
 180  
      * <li>None of these matching child nodes has a value.</li>
 181  
      * </ul>
 182  
      * </p>
 183  
      * <p>
 184  
      * If all of these tests are successful, the matching child node of the
 185  
      * second source node is returned. Otherwise the result is <b>null</b>.
 186  
      * </p>
 187  
      *
 188  
      * @param node1 the first source node
 189  
      * @param node2 the second source node
 190  
      * @param child the child node of the first source node to be checked
 191  
      * @param children a list with all children of the second source node
 192  
      * @return the matching child node of the second source node or <b>null</b>
 193  
      * if there is none
 194  
      */
 195  
     protected ConfigurationNode findCombineNode(ConfigurationNode node1,
 196  
             ConfigurationNode node2, ConfigurationNode child, List<ConfigurationNode> children)
 197  
     {
 198  671
         if (child.getValue() == null && !isListNode(child)
 199  
                 && node1.getChildrenCount(child.getName()) == 1
 200  
                 && node2.getChildrenCount(child.getName()) == 1)
 201  
         {
 202  108
             ConfigurationNode child2 = node2.getChildren(
 203  
                     child.getName()).iterator().next();
 204  108
             if (child2.getValue() == null)
 205  
             {
 206  101
                 return child2;
 207  
             }
 208  
         }
 209  570
         return null;
 210  
     }
 211  
 }