Class OverrideCombiner
- java.lang.Object
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- org.apache.commons.configuration.tree.NodeCombiner
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- org.apache.commons.configuration.tree.OverrideCombiner
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public class OverrideCombiner extends NodeCombiner
A concrete combiner implementation that is able to construct an override combination.
An override combination means that nodes in the first node structure take precedence over nodes in the second, or - in other words - nodes of the second structure are only added to the resulting structure if they do not occur in the first one. This is especially suitable for dealing with the properties of configurations that are defined in an
override
section of a configuration definition file (hence the name).This combiner will iterate over the second node hierarchy and find all nodes that are not contained in the first hierarchy; these are added to the result. If a node can be found in both structures, it is checked whether a combination (in a recursive way) can be constructed for the two, which will then be added. Per default, nodes are combined, which occur only once in both structures. This test is implemented in the
canCombine()
method.As is true for the
UnionCombiner
, for this combiner list nodes are important. TheaddListNode()
can be called to declare certain nodes as list nodes. This has the effect that these nodes will never be combined.- Since:
- 1.3
- Version:
- $Id: OverrideCombiner.java 1301991 2012-03-17 20:18:02Z sebb $
- Author:
- Commons Configuration team
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Field Summary
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Fields inherited from class org.apache.commons.configuration.tree.NodeCombiner
listNodes
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Constructor Summary
Constructors Constructor Description OverrideCombiner()
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Method Summary
All Methods Instance Methods Concrete Methods Modifier and Type Method Description protected void
addAttributes(ViewNode result, ConfigurationNode node1, ConfigurationNode node2)
Handles the attributes during a combination process.protected ConfigurationNode
canCombine(ConfigurationNode node1, ConfigurationNode node2, ConfigurationNode child)
Tests if a child node of the second node can be combined with the given child node of the first node.ConfigurationNode
combine(ConfigurationNode node1, ConfigurationNode node2)
Constructs an override combination for the passed in node structures.-
Methods inherited from class org.apache.commons.configuration.tree.NodeCombiner
addListNode, createViewNode, getListNodes, isListNode
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Constructor Detail
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OverrideCombiner
public OverrideCombiner()
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Method Detail
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combine
public ConfigurationNode combine(ConfigurationNode node1, ConfigurationNode node2)
Constructs an override combination for the passed in node structures.- Specified by:
combine
in classNodeCombiner
- Parameters:
node1
- the first nodenode2
- the second node- Returns:
- the resulting combined node structure
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addAttributes
protected void addAttributes(ViewNode result, ConfigurationNode node1, ConfigurationNode node2)
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.- Parameters:
result
- the resulting nodenode1
- the first nodenode2
- the second node
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canCombine
protected ConfigurationNode canCombine(ConfigurationNode node1, ConfigurationNode node2, ConfigurationNode child)
Tests if a child node of the second node can be combined with the given child node of the first node. If this is the case, the corresponding node will be returned, otherwise null. This implementation checks whether the child node occurs only once in both hierarchies and is no known list node.- Parameters:
node1
- the first nodenode2
- the second nodechild
- the child node (of the first node)- Returns:
- a child of the second node, with which a combination is possible
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