Top Description Fields Constructors Methods
com.sun.org.apache.xerces.internal.dom

public Class DeepNodeListImpl

extends Object
implements NodeList
Class Inheritance
All Implemented Interfaces
org.w3c.dom.NodeList
Imports
java.util.ArrayList, .List, org.w3c.dom.Node, .NodeList

This class implements the DOM's NodeList behavior for Element.getElementsByTagName()

The DOM describes NodeList as follows:

1) It may represent EITHER nodes scattered through a subtree (when returned by Element.getElementsByTagName), or just the immediate children (when returned by Node.getChildNodes). The latter is easy, but the former (which this class addresses) is more challenging.

2) Its behavior is "live" -- that is, it always reflects the current state of the document tree. To put it another way, the NodeLists obtained before and after a series of insertions and deletions are effectively identical (as far as the user is concerned, the former has been dynamically updated as the changes have been made).

3) Its API accesses individual nodes via an integer index, with the listed nodes numbered sequentially in the order that they were found during a preorder depth-first left-to-right search of the tree. (Of course in the case of getChildNodes, depth is not involved.) As nodes are inserted or deleted in the tree, and hence the NodeList, the numbering of nodes that follow them in the NodeList will change.

It is rather painful to support the latter two in the getElementsByTagName case. The current solution is for Nodes to maintain a change count (eventually that may be a Digest instead), which the NodeList tracks and uses to invalidate itself.

Unfortunately, this does _not_ respond efficiently in the case that the dynamic behavior was supposed to address: scanning a tree while it is being extended. That requires knowing which subtrees have changed, which can become an arbitrarily complex problem.

We save some work by filling the vector only as we access the item()s... but I suspect the same users who demanded index-based access will also start by doing a getLength() to control their loop, blowing this optimization out of the water.

Note

Level 2 of the DOM will probably _not_ use NodeList for its extended search mechanisms, partly for the reasons just discussed.

Since
PR-DOM-Level-1-19980818.

Field Summary

Modifier and TypeField and Description
protected int
protected boolean
protected List<Node>
protected String
protected NodeImpl
protected String

Constructor Summary

AccessConstructor and Description
public
DeepNodeListImpl(NodeImpl rootNode, String tagName)

Constructor.

public
DeepNodeListImpl(NodeImpl rootNode, String nsName, String tagName)

Constructor for Namespace support.

Method Summary

Modifier and TypeMethod and Description
public int
getLength()

Implements org.w3c.dom.NodeList.getLength.

Returns the length of the node list.

public Node
item(int
Index into the collection.
index
)

Implements org.w3c.dom.NodeList.item.

Returns the node at the specified index.

protected Node
nextMatchingElementAfter(Node current)

Iterative tree-walker.

Inherited from java.lang.Object:
cloneequalsfinalizegetClasshashCodenotifynotifyAlltoStringwaitwaitwait

Field Detail

changesback to summary
protected int changes
enableNSback to summary
protected boolean enableNS
nodesback to summary
protected List<Node> nodes
nsNameback to summary
protected String nsName
rootNodeback to summary
protected NodeImpl rootNode
tagNameback to summary
protected String tagName

Constructor Detail

DeepNodeListImplback to summary
public DeepNodeListImpl(NodeImpl rootNode, String tagName)

Constructor.

DeepNodeListImplback to summary
public DeepNodeListImpl(NodeImpl rootNode, String nsName, String tagName)

Constructor for Namespace support.

Method Detail

getLengthback to summary
public int getLength()

Implements org.w3c.dom.NodeList.getLength.

Returns the length of the node list.

itemback to summary
public Node item(int index)

Implements org.w3c.dom.NodeList.item.

Returns the node at the specified index.

Parameters
index:int

Doc from org.w3c.dom.NodeList.item.

Index into the collection.

Returns:Node

Doc from org.w3c.dom.NodeList.item.

The node at the indexth position in the NodeList, or null if that is not a valid index.

nextMatchingElementAfterback to summary
protected Node nextMatchingElementAfter(Node current)

Iterative tree-walker. When you have a Parent link, there's often no need to resort to recursion. NOTE THAT only Element nodes are matched since we're specifically supporting getElementsByTagName().