Class NodeCombiner

  • 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
    • 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.
    • Constructor Summary

      Constructors 
      Constructor Description
      NodeCombiner()
      Creates a new instance of NodeCombiner.
    • Field Detail

      • listNodes

        protected java.util.Set<java.lang.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​(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
      • 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
      • 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