Package org.apache.commons.configuration2.tree

Class NodeSelector

java.lang.Object
org.apache.commons.configuration2.tree.NodeSelector
public class NodeSelector extends Object

A class for selecting a specific node based on a key or a set of keys.

An instance of this class is initialized with the key of a node. It is also possible to concatenate multiple keys - e.g. if a sub key is to be constructed from another sub key. NodeSelector provides the select() method which evaluates the wrapped keys on a specified root node and returns the resulting unique target node. The class expects that the key(s) stored in an instance select exactly one target node. If this is not the case, result is null indicating that the selection criteria are not sufficient.

Implementation node: Instances of this class are immutable. They can be shared between arbitrary components.

Since:
2.0

  • Field Details

    • nodeKeys

      private final List<String> nodeKeys
      Stores the wrapped keys.

  • Constructor Details

    • NodeSelector

      private NodeSelector(List<String> keys)
      Creates a new instance of NodeSelector and initializes it with the list of keys to be used as selection criteria.
      Parameters:
      keys - the keys for selecting nodes

    • NodeSelector

      public NodeSelector(String key)
      Creates a new instance of NodeSelector and initializes it with the key to the target node.
      Parameters:
      key - the key

  • Method Details

    • equals

      public boolean equals(Object obj)
      Compares this object with another one. Two instances of NodeSelector are considered equal if they have the same keys as selection criteria.
      Overrides:
      equals in class Object
      Parameters:
      obj - the object to be compared
      Returns:
      a flag whether these objects are equal

    • getFilteredResults

      private void getFilteredResults(ImmutableNode root, NodeKeyResolver<ImmutableNode> resolver, NodeHandler<ImmutableNode> handler, String key, List<ImmutableNode> nodes)
      Executes a query for a given key and filters the results for nodes only.
      Parameters:
      root - the root node for the query
      resolver - the NodeKeyResolver
      handler - the NodeHandler
      key - the key
      nodes - here the results are stored

    • hashCode

      public int hashCode()
      Returns a hash code for this object.
      Overrides:
      hashCode in class Object
      Returns:
      a hash code

    • select

      public ImmutableNode select(ImmutableNode root, NodeKeyResolver<ImmutableNode> resolver, NodeHandler<ImmutableNode> handler)
      Applies this NodeSelector on the specified root node. This method applies the selection criteria stored in this object and tries to determine a single target node. If this is successful, the target node is returned. Otherwise, result is null.
      Parameters:
      root - the root node on which to apply this selector
      resolver - the NodeKeyResolver
      handler - the NodeHandler
      Returns:
      the selected target node or null

    • subSelector

      public NodeSelector subSelector(String subKey)
      Creates a sub NodeSelector object which uses the key(s) of this selector plus the specified key as selection criteria. This is useful when another selection is to be performed on the results of a first selector.
      Parameters:
      subKey - the additional key for the sub selector
      Returns:
      the sub NodeSelector instance

    • toString

      public String toString()
      Returns a string representation for this object. This string contains the keys to be used as selection criteria.
      Overrides:
      toString in class Object
      Returns:
      a string for this object