org.apache.commons.configuration2.tree.MergeCombiner Maven / Gradle / Ivy
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Tools to assist in the reading of configuration/preferences files in
various formats
/*
* 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.configuration2.tree;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.LinkedList;
import java.util.List;
import java.util.Map;
import org.apache.commons.lang3.ObjectUtils;
/**
*
* A specialized implementation of the {@code NodeCombiner} interface
* that performs a merge from two passed in node hierarchies.
*
*
* This combiner performs the merge using a few rules:
*
*
* - Nodes can be merged when attributes that appear in both have the same value.
* - Only a single node in the second file is considered a match to the node in the first file.
* - Attributes in nodes that match are merged.
*
- Nodes in both files that do not match are added to the result.
*
*
* @version $Id: MergeCombiner.java 1679789 2015-05-16 17:48:19Z oheger $
* @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
*/
@Override
public ImmutableNode combine(ImmutableNode node1, ImmutableNode node2)
{
ImmutableNode.Builder result = new ImmutableNode.Builder();
result.name(node1.getNodeName());
result.value(node1.getValue());
addAttributes(result, node1, node2);
// Check if nodes can be combined
List children2 = new LinkedList(node2.getChildren());
for (ImmutableNode child1 : node1.getChildren())
{
ImmutableNode child2 = canCombine(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 (ImmutableNode c : children2)
{
result.addChild(c);
}
return result.create();
}
/**
* 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 builder for the resulting node
* @param node1 the first node
* @param node2 the second node
*/
protected void addAttributes(ImmutableNode.Builder result, ImmutableNode node1,
ImmutableNode node2)
{
Map attributes = new HashMap();
attributes.putAll(node1.getAttributes());
for (Map.Entry e : node2.getAttributes().entrySet())
{
if (!attributes.containsKey(e.getKey()))
{
attributes.put(e.getKey(), e.getValue());
}
}
result.addAttributes(attributes);
}
/**
* 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 node2 the second node
* @param child the child node (of the first node)
* @param children2 the children of the 2nd node
* @return a child of the second node, with which a combination is possible
*/
protected ImmutableNode canCombine(ImmutableNode node2,
ImmutableNode child, List children2)
{
Map attrs1 = child.getAttributes();
List nodes = new ArrayList();
List children =
HANDLER.getChildren(node2, child.getNodeName());
for (ImmutableNode node : children)
{
if (matchAttributes(attrs1, node))
{
nodes.add(node);
}
}
if (nodes.size() == 1)
{
return nodes.get(0);
}
if (nodes.size() > 1 && !isListNode(child))
{
for (ImmutableNode node : nodes)
{
children2.remove(node);
}
}
return null;
}
/**
* Checks whether the attributes of the passed in node are compatible.
*
* @param attrs1 the attributes of the first node
* @param node the 2nd node
* @return a flag whether these nodes can be combined regarding their
* attributes
*/
private static boolean matchAttributes(Map attrs1,
ImmutableNode node)
{
Map attrs2 = node.getAttributes();
for (Map.Entry e : attrs1.entrySet())
{
if (attrs2.containsKey(e.getKey())
&& !ObjectUtils
.equals(e.getValue(), attrs2.get(e.getKey())))
{
return false;
}
}
return true;
}
}