NodeCombiner (Apache Commons Configuration 1.10 API)

java.lang.Object
- org.apache.commons.configuration.tree.NodeCombiner

Direct Known Subclasses:

MergeCombiner, OverrideCombiner, UnionCombiner
```
public abstract class NodeCombiner
extends 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

Field Summary

Fields
Modifier and Type Field and Description

protected Set<String> listNodes
Stores a list with node names that are known to be list nodes.

Fields
Modifier and Type	Field and Description
`protected Set<String>`	`listNodes` Stores a list with node names that are known to be list nodes.

Constructor Summary

Constructors
Constructor and Description

NodeCombiner()
Creates a new instance of NodeCombiner.

Constructors
Constructor and Description
`NodeCombiner()` Creates a new instance of `NodeCombiner`.

Method Summary

Methods
Modifier and Type	Method and Description
`void`	`addListNode(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.
`Set<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.

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Field Detail
  - listNodes
```
protected Set<String> listNodes
```
    Stores a list with node names that are known to be list nodes.
- Constructor Detail
  - NodeCombiner
```
public NodeCombiner()
```
    Creates a new instance of NodeCombiner.
- Method Detail
  - addListNode
```
public void addListNode(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
  - getListNodes
```
public Set<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
  - 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
  - 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 node
    node2 - the second root node
    
    Returns:
    the resulting combined node structure
  - createViewNode
```
protected ViewNode createViewNode()
```
    Creates a new view node. This method will be called whenever a new view node is to be created. It can be overridden to create special view nodes. This base implementation returns a new instance of ViewNode.
    
    Returns:
    the new view node

Class NodeCombiner

Field Summary

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Field Detail

listNodes

Constructor Detail

NodeCombiner

Method Detail

addListNode

getListNodes

isListNode

combine

createViewNode