Package org.apache.commons.configuration2.tree

Class TrackedNodeModel

java.lang.Object
org.apache.commons.configuration2.tree.TrackedNodeModel
All Implemented Interfaces:
NodeModel<ImmutableNode>
public class TrackedNodeModel extends Object implements NodeModel<ImmutableNode>

A specialized NodeModel implementation that uses a tracked node managed by an InMemoryNodeModel object as root node.

Models of this type are useful when working on specific sub trees of a nodes structure. This is the case for instance for a SubnodeConfiguration.

An instance of this class is constructed with an InMemoryNodeModelSupport object providing a reference to the underlying InMemoryNodeModel and the NodeSelector pointing to the tracked node acting as this model's root node. The NodeModel operations are implemented by delegating to the wrapped InMemoryNodeModel object specifying the selector to the tracked node as target root node for the update transaction. Note that the tracked node can become detached at any time. This situation is handled transparently by the implementation of InMemoryNodeModel. The reason for using an InMemoryNodeModelSupport object rather than an InMemoryNodeModel directly is that this additional layer of indirection can be used for performing special initializations on the model before it is returned to the TrackedNodeModel object. This is needed by some dynamic configuration implementations, e.g. by CombinedConfiguration.

If the tracked node acting as root node is exclusively used by this model, it should be released when this model is no longer needed. This can be done manually by calling the close() method. It is also possible to pass a value of true to the untrackOnFinalize argument of the constructor. This causes close() to be called automatically if this object gets claimed by the garbage collector.

As InMemoryNodeModel, this class is thread-safe.

Since:
2.0

  • Constructor Details

    • TrackedNodeModel

      public TrackedNodeModel(InMemoryNodeModelSupport modelSupport, NodeSelector sel, boolean untrackOnFinalize)
      Creates a new instance of TrackedNodeModel and initializes it with the given underlying model and the selector to the root node. The boolean argument controls whether the associated tracked node should be released when this object gets finalized. This allows the underlying model to free some resources. If used as model within a SubnodeConfiguration, there is typically no way to discard the model explicitly. Therefore, it makes sense to do this automatically on finalization.
      Parameters:
      modelSupport - the underlying InMemoryNodeModelSupport (must not be null)
      sel - the selector to the root node of this model (must not be null)
      untrackOnFinalize - a flag whether the tracked node should be released on finalization
      Throws:
      IllegalArgumentException - if a required parameter is missing

  • Method Details

    • addNodes

      public void addNodes(String key, Collection<? extends ImmutableNode> nodes, NodeKeyResolver<ImmutableNode> resolver)
      Description copied from interface: NodeModel
      Adds a collection of new nodes to this model. This operation corresponds to the addNodes() method of the HierarchicalConfiguration interface. The new nodes are either added to an existing node (if the passed in key selects exactly one node) or to a newly created node. The passed in NodeKeyResolver is used to interpret the given key.
      Specified by:
      addNodes in interface NodeModel<ImmutableNode>
      Parameters:
      key - the key
      nodes - the collection of nodes to be added (may be null)
      resolver - the NodeKeyResolver

    • addProperty

      public void addProperty(String key, Iterable<?> values, NodeKeyResolver<ImmutableNode> resolver)
      Description copied from interface: NodeModel
      Adds a new property to this node model consisting of an arbitrary number of values. The key for the add operation is provided. For each value a new node has to be added. The passed in resolver is queried for a NodeAddData object defining the add operation to be performed.
      Specified by:
      addProperty in interface NodeModel<ImmutableNode>
      Parameters:
      key - the key
      values - the values to be added at the position defined by the key
      resolver - the NodeKeyResolver

    • clear

      public void clear(NodeKeyResolver<ImmutableNode> resolver)
      Removes all data from this model. This implementation clears the sub tree spanned by the associate tracked node. This has the side effect that this in any case becomes detached.
      Specified by:
      clear in interface NodeModel<ImmutableNode>
      Parameters:
      resolver - the NodeKeyResolver.

    • clearProperty

      public void clearProperty(String key, NodeKeyResolver<ImmutableNode> resolver)
      Description copied from interface: NodeModel
      Clears the value of a property. This method is similar to NodeModel.clearTree(String, NodeKeyResolver): However, the nodes referenced by the passed in key are not removed completely, but only their value is set to null.
      Specified by:
      clearProperty in interface NodeModel<ImmutableNode>
      Parameters:
      key - the key selecting the properties to be cleared
      resolver - the NodeKeyResolver

    • clearTree

      public List<QueryResult<ImmutableNode>> clearTree(String key, NodeKeyResolver<ImmutableNode> resolver)
      Description copied from interface: NodeModel
      Removes the sub trees defined by the given key from this model. All nodes selected by this key are retrieved from the specified NodeKeyResolver and removed from the model.
      Specified by:
      clearTree in interface NodeModel<ImmutableNode>
      Parameters:
      key - the key selecting the properties to be removed
      resolver - the NodeKeyResolver
      Returns:
      an object with information about the data removed

    • close

      public void close()
      Closes this model. This causes the tracked node this model is based upon to be released (i.e. InMemoryNodeModel.untrackNode(NodeSelector) is called). This method should be called when this model is no longer needed. This implementation is idempotent; it is safe to call close() multiple times - only the first invocation has an effect. After this method has been called this model can no longer be used because there is no guarantee that the node can still be accessed from the parent model.

    • finalize

      protected void finalize() throws Throwable
      This implementation calls close() if the untrackOnFinalize flag was set when this instance was constructed. While this is not 100 percent reliable, it is better than keeping the tracked node hanging around. Note that it is not a problem if close() already had been invoked manually because this method is idempotent.
      Overrides:
      finalize in class Object
      Throws:
      Throwable
      See Also:

    • getInMemoryRepresentation

      public ImmutableNode getInMemoryRepresentation()
      Gets a representation of the data stored in this model in form of a nodes hierarchy of ImmutableNode objects. A concrete model implementation can use an arbitrary means to store its data. When a model's data is to be used together with other functionality of the Configuration library (e.g. when combining multiple configuration sources) it has to be transformed into a common format. This is done by this method. ImmutableNode is a generic representation of a hierarchical structure. Thus, it should be possible to generate a corresponding structure from arbitrary model data. This implementation returns the tracked node instance acting as root node of this model.
      Specified by:
      getInMemoryRepresentation in interface NodeModel<ImmutableNode>
      Returns:
      the root node of an in-memory hierarchy representing the data stored in this model

    • getNodeHandler

      public NodeHandler<ImmutableNode> getNodeHandler()
      Description copied from interface: NodeModel
      Gets a NodeHandler for dealing with the nodes managed by this model.
      Specified by:
      getNodeHandler in interface NodeModel<ImmutableNode>
      Returns:
      the NodeHandler

    • getParentModel

      public InMemoryNodeModel getParentModel()
      Gets the parent model. Operations on this model are delegated to this parent model specifying the selector to the tracked node.
      Returns:
      the parent model

    • getParentModelSupport

      public InMemoryNodeModelSupport getParentModelSupport()
      Gets the InMemoryNodeModelSupport object which is used to gain access to the underlying node model.
      Returns:
      the associated InMemoryNodeModelSupport object

    • getSelector

      public NodeSelector getSelector()
      Gets the NodeSelector pointing to the tracked node managed by this model.
      Returns:
      the tracked node selector

    • isReleaseTrackedNodeOnFinalize

      public boolean isReleaseTrackedNodeOnFinalize()
      Returns the flag whether the managed tracked node is to be released when this object gets finalized. This method returns the value of the corresponding flag passed to the constructor. If result is true, the underlying model is asked to untrack the managed node when this object is claimed by the GC.
      Returns:
      a flag whether the managed tracked node should be released when this object dies
      See Also:

    • setProperty

      public void setProperty(String key, Object value, NodeKeyResolver<ImmutableNode> resolver)
      Description copied from interface: NodeModel
      Changes the value of a property. This is a more complex operation as it might involve adding, updating, or deleting nodes and attributes from the model. The object representing the new value is passed to the NodeKeyResolver which will produce a corresponding NodeUpdateData object. Based on the content of this object, update operations are performed.
      Specified by:
      setProperty in interface NodeModel<ImmutableNode>
      Parameters:
      key - the key
      value - the new value for this property (to be evaluated by the NodeKeyResolver)
      resolver - the NodeKeyResolver

    • setRootNode

      public void setRootNode(ImmutableNode newRoot)
      Description copied from interface: NodeModel
      Sets a new root node for this model. The whole structure is replaced by the new node and its children.
      Specified by:
      setRootNode in interface NodeModel<ImmutableNode>
      Parameters:
      newRoot - the new root node to be set (can be null, then an empty root node is set)