/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.commons.configuration.tree;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.List;
import java.util.ArrayList;
/**
* <p>
* A specialized implementation of the <code>NodeCombiner</code> interface
* that performs a merge from two passed in node hierarchies.
* </p>
* <p>
* This combiner performs the merge using a few rules:
* <ol>
* <li>Nodes can be merged when attributes that appear in both have the same value.</li>
* <li>Only a single node in the second file is considered a match to the node in the first file.</li>
* <li>Attributes in nodes that match are merged.
* <li>Nodes in both files that do not match are added to the result.</li>
* </ol>
* </p>
*
* @author <a
* href="http://commons.apache.org/configuration/team-list.html">Commons
* Configuration team</a>
* @version $Id: MergeCombiner.java 764168 2009-04-11 06:23:13Z rgoers $
* @since 1.7
*/
public class MergeCombiner extends NodeCombiner
{
/**
* Combines the given nodes to a new union node.
*
* @param node1 the first source node
* @param node2 the second source node
* @return the union node
*/
public ConfigurationNode combine(ConfigurationNode node1, ConfigurationNode node2)
{
ViewNode result = createViewNode();
result.setName(node1.getName());
result.setValue(node1.getValue());
addAttributes(result, node1, node2);
// Check if nodes can be combined
List children2 = new LinkedList(node2.getChildren());
for (Iterator it = node1.getChildren().iterator(); it.hasNext();)
{
ConfigurationNode child1 = (ConfigurationNode) it.next();
ConfigurationNode child2 = canCombine(node1, node2, child1, children2);
if (child2 != null)
{
result.addChild(combine(child1, child2));
children2.remove(child2);
}
else
{
result.addChild(child1);
}
}
// Add remaining children of node 2
for (Iterator it = children2.iterator(); it.hasNext();)
{
result.addChild((ConfigurationNode) it.next());
}
return result;
}
/**
* Handles the attributes during a combination process. First all attributes
* of the first node will be added to the result. Then all attributes of the
* second node, which are not contained in the first node, will also be
* added.
*
* @param result the resulting node
* @param node1 the first node
* @param node2 the second node
*/
protected void addAttributes(ViewNode result, ConfigurationNode node1,
ConfigurationNode node2)
{
result.appendAttributes(node1);
for (Iterator it = node2.getAttributes().iterator(); it.hasNext();)
{
ConfigurationNode attr = (ConfigurationNode) it.next();
if (node1.getAttributeCount(attr.getName()) == 0)
{
result.addAttribute(attr);
}
}
}
/**
* Tests if the first node can be combined with the second node. A node can
* only be combined if its attributes are all present in the second node and
* they all have the same value.
*
* @param node1 the first node
* @param node2 the second node
* @param child the child node (of the first node)
* @return a child of the second node, with which a combination is possible
*/
protected ConfigurationNode canCombine(ConfigurationNode node1,
ConfigurationNode node2, ConfigurationNode child, List children2)
{
List attrs1 = child.getAttributes();
List nodes = new ArrayList();
List children = node2.getChildren(child.getName());
Iterator it = children.iterator();
while (it.hasNext())
{
ConfigurationNode node = (ConfigurationNode) it.next();
Iterator iter = attrs1.iterator();
while (iter.hasNext())
{
ConfigurationNode attr1 = (ConfigurationNode) iter.next();
List list2 = node.getAttributes(attr1.getName());
if (list2.size() == 1
&& !attr1.getValue().equals(((ConfigurationNode) list2.get(0)).getValue()))
{
node = null;
break;
}
}
if (node != null)
{
nodes.add(node);
}
}
if (nodes.size() == 1)
{
return (ConfigurationNode) nodes.get(0);
}
if (nodes.size() > 1 && !isListNode(child))
{
Iterator iter = nodes.iterator();
while (iter.hasNext())
{
children2.remove(iter.next());
}
}
return null;
}
}
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