Coverage Report - org.apache.commons.configuration.tree.UnionCombiner
 
Classes in this File Line Coverage Branch Coverage Complexity
UnionCombiner
100%
21/21
100%
5/5
4
 
 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.Iterator;
 20  
 import java.util.LinkedList;
 21  
 import java.util.List;
 22  
 
 23  
 /**
 24  
  * <p>
 25  
  * A specialized implementation of the <code>NodeCombiner</code> interface
 26  
  * that constructs a union from two passed in node hierarchies.
 27  
  * </p>
 28  
  * <p>
 29  
  * The given source hierarchies are traversed and their nodes are added to the
 30  
  * resulting structure. Under some circumstances two nodes can be combined
 31  
  * rather than adding both. This is the case if both nodes are single children
 32  
  * (no lists) of their parents and do not have values. The corresponding check
 33  
  * is implemented in the <code>findCombineNode()</code> method.
 34  
  * </p>
 35  
  * <p>
 36  
  * Sometimes it is not possible for this combiner to detect whether two nodes
 37  
  * can be combined or not. Consider the following two node hierarchies:
 38  
  * </p>
 39  
  * <p>
 40  
  *
 41  
  * <pre>
 42  
  * Hierarchy 1:
 43  
  *
 44  
  * Database
 45  
  *   +--Tables
 46  
  *        +--Table
 47  
  *             +--name [users]
 48  
  *             +--fields
 49  
  *                   +--field
 50  
  *                   |    +--name [uid]
 51  
  *                   +--field
 52  
  *                   |    +--name [usrname]
 53  
  *                     ...
 54  
  * </pre>
 55  
  *
 56  
  * </p>
 57  
  * <p>
 58  
  *
 59  
  * <pre>
 60  
  * Hierarchy 2:
 61  
  *
 62  
  * Database
 63  
  *   +--Tables
 64  
  *        +--Table
 65  
  *             +--name [documents]
 66  
  *             +--fields
 67  
  *                   +--field
 68  
  *                   |    +--name [docid]
 69  
  *                   +--field
 70  
  *                   |    +--name [docname]
 71  
  *                     ...
 72  
  * </pre>
 73  
  *
 74  
  * </p>
 75  
  * <p>
 76  
  * Both hierarchies contain data about database tables. Each describes a single
 77  
  * table. If these hierarchies are to be combined, the result should probably
 78  
  * look like the following:
 79  
  * <p>
 80  
  *
 81  
  * <pre>
 82  
  * Database
 83  
  *   +--Tables
 84  
  *        +--Table
 85  
  *        |    +--name [users]
 86  
  *        |    +--fields
 87  
  *        |          +--field
 88  
  *        |          |    +--name [uid]
 89  
  *        |            ...
 90  
  *        +--Table
 91  
  *             +--name [documents]
 92  
  *             +--fields
 93  
  *                   +--field
 94  
  *                   |    +--name [docid]
 95  
  *                     ...
 96  
  * </pre>
 97  
  *
 98  
  * </p>
 99  
  * <p>
 100  
  * i.e. the <code>Tables</code> nodes should be combined, while the
 101  
  * <code>Table</code> nodes should both be added to the resulting tree. From
 102  
  * the combiner's point of view there is no difference between the
 103  
  * <code>Tables</code> and the <code>Table</code> nodes in the source trees,
 104  
  * so the developer has to help out and give a hint that the <code>Table</code>
 105  
  * nodes belong to a list structure. This can be done using the
 106  
  * <code>addListNode()</code> method; this method expects the name of a node,
 107  
  * which should be treated as a list node. So if
 108  
  * <code>addListNode("Table");</code> was called, the combiner knows that it
 109  
  * must not combine the <code>Table</code> nodes, but add it both to the
 110  
  * resulting tree.
 111  
  * </p>
 112  
  *
 113  
  * @author <a
 114  
  * href="http://jakarta.apache.org/commons/configuration/team-list.html">Commons
 115  
  * Configuration team</a>
 116  
  * @version $Id: UnionCombiner.java 439648 2006-09-02 20:42:10Z oheger $
 117  
  * @since 1.3
 118  
  */
 119  16
 public class UnionCombiner extends NodeCombiner
 120  
 {
 121  
     /**
 122  
      * Combines the given nodes to a new union node.
 123  
      *
 124  
      * @param node1 the first source node
 125  
      * @param node2 the second source node
 126  
      * @return the union node
 127  
      */
 128  
     public ConfigurationNode combine(ConfigurationNode node1,
 129  
             ConfigurationNode node2)
 130  
     {
 131  83
         ViewNode result = createViewNode();
 132  83
         result.setName(node1.getName());
 133  83
         result.appendAttributes(node1);
 134  83
         result.appendAttributes(node2);
 135  
 
 136  
         // Check if nodes can be combined
 137  83
         List children2 = new LinkedList(node2.getChildren());
 138  399
         for (Iterator it = node1.getChildren().iterator(); it.hasNext();)
 139  
         {
 140  233
             ConfigurationNode child1 = (ConfigurationNode) it.next();
 141  233
             ConfigurationNode child2 = findCombineNode(node1, node2, child1,
 142  
                     children2);
 143  233
             if (child2 != null)
 144  
             {
 145  65
                 result.addChild(combine(child1, child2));
 146  65
                 children2.remove(child2);
 147  
             }
 148  
             else
 149  
             {
 150  168
                 result.addChild(child1);
 151  
             }
 152  
         }
 153  
 
 154  
         // Add remaining children of node 2
 155  251
         for (Iterator it = children2.iterator(); it.hasNext();)
 156  
         {
 157  85
             result.addChild((ConfigurationNode) it.next());
 158  
         }
 159  
 
 160  83
         return result;
 161  
     }
 162  
 
 163  
     /**
 164  
      * <p>
 165  
      * Tries to find a child node of the second source node, with whitch a child
 166  
      * of the first source node can be combined. During combining of the source
 167  
      * nodes an iteration over the first source node's children is performed.
 168  
      * For each child node it is checked whether a corresponding child node in
 169  
      * the second source node exists. If this is the case, these corresponsing
 170  
      * child nodes are recursively combined and the result is added to the
 171  
      * combined node. This method implements the checks whether such a recursive
 172  
      * combination is possible. The actual implementation tests the following
 173  
      * conditions:
 174  
      * </p>
 175  
      * <p>
 176  
      * <ul>
 177  
      * <li>In both the first and the second source node there is only one child
 178  
      * node with the given name (no list structures).</li>
 179  
      * <li>The given name is not in the list of known list nodes, i.e. it was
 180  
      * not passed to the <code>addListNode()</code> method.</li>
 181  
      * <li>None of these matching child nodes has a value.</li>
 182  
      * </ul>
 183  
      * </p>
 184  
      * <p>
 185  
      * If all of these tests are successfull, the matching child node of the
 186  
      * second source node is returned. Otherwise the result is <b>null</b>.
 187  
      * </p>
 188  
      *
 189  
      * @param node1 the first source node
 190  
      * @param node2 the second source node
 191  
      * @param child the child node of the first source node to be checked
 192  
      * @param children a list with all children of the second source node
 193  
      * @return the matching child node of the second source node or <b>null</b>
 194  
      * if there is none
 195  
      */
 196  
     protected ConfigurationNode findCombineNode(ConfigurationNode node1,
 197  
             ConfigurationNode node2, ConfigurationNode child, List children)
 198  
     {
 199  233
         if (child.getValue() == null && !isListNode(child)
 200  
                 && node1.getChildrenCount(child.getName()) == 1
 201  
                 && node2.getChildrenCount(child.getName()) == 1)
 202  
         {
 203  71
             ConfigurationNode child2 = (ConfigurationNode) node2.getChildren(
 204  
                     child.getName()).iterator().next();
 205  71
             if (child2.getValue() == null)
 206  
             {
 207  65
                 return child2;
 208  
             }
 209  
         }
 210  168
         return null;
 211  
     }
 212  
 }