Class NodeCombiner
- java.lang.Object
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- org.apache.commons.configuration.tree.NodeCombiner
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- Direct Known Subclasses:
MergeCombiner
,OverrideCombiner
,UnionCombiner
public abstract class NodeCombiner extends java.lang.Object
A base class for node combiner implementations.
A node combiner is an object that knows how two hierarchical node structures can be combined into a single one. Of course, there are many possible ways of implementing such a combination, e.g. constructing a union, an intersection, or an "override" structure (were nodes in the first hierarchy take precedence over nodes in the second hierarchy). This abstract base class only provides some helper methods and defines the common interface for node combiners. Concrete sub classes will implement the diverse combination algorithms.
For some concrete combiner implementations it is important to distinguish whether a node is a single node or whether it belongs to a list structure. Alone from the input structures, the combiner will not always be able to make this decision. So sometimes it may be necessary for the developer to configure the combiner and tell it, which nodes should be treated as list nodes. For this purpose the
addListNode()
method exists. It can be passed the name of a node, which should be considered a list node.- Since:
- 1.3
- Version:
- $Id: NodeCombiner.java 1206476 2011-11-26 16:19:53Z oheger $
- Author:
- Commons Configuration team
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Field Summary
Fields Modifier and Type Field Description protected java.util.Set<java.lang.String>
listNodes
Stores a list with node names that are known to be list nodes.
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Constructor Summary
Constructors Constructor Description NodeCombiner()
Creates a new instance ofNodeCombiner
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Method Summary
All Methods Instance Methods Abstract Methods Concrete Methods Modifier and Type Method Description void
addListNode(java.lang.String nodeName)
Adds the name of a node to the list of known list nodes.abstract ConfigurationNode
combine(ConfigurationNode node1, ConfigurationNode node2)
Combines the hierarchies represented by the given root nodes.protected ViewNode
createViewNode()
Creates a new view node.java.util.Set<java.lang.String>
getListNodes()
Returns a set with the names of nodes that are known to be list nodes.boolean
isListNode(ConfigurationNode node)
Checks if a node is a list node.
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Method Detail
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addListNode
public void addListNode(java.lang.String nodeName)
Adds the name of a node to the list of known list nodes. This means that nodes with this name will never be combined.- Parameters:
nodeName
- the name to be added
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getListNodes
public java.util.Set<java.lang.String> getListNodes()
Returns a set with the names of nodes that are known to be list nodes.- Returns:
- a set with the names of list nodes
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isListNode
public boolean isListNode(ConfigurationNode node)
Checks if a node is a list node. This implementation tests if the given node name is contained in the set of known list nodes. Derived classes which use different criteria may overload this method.- Parameters:
node
- the node to be tested- Returns:
- a flag whether this is a list node
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combine
public abstract ConfigurationNode combine(ConfigurationNode node1, ConfigurationNode node2)
Combines the hierarchies represented by the given root nodes. This method must be defined in concrete sub classes with the implementation of a specific combination algorithm.- Parameters:
node1
- the first root nodenode2
- the second root node- Returns:
- the resulting combined node structure
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