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DTMIterator.javaAPI DocJava SE 5 API12171Fri Aug 26 14:56:00 BST 2005com.sun.org.apache.xml.internal.dtm

DTMIterator

public interface DTMIterator
DTMIterators are used to step through a (possibly filtered) set of nodes. Their API is modeled largely after the DOM NodeIterator.

A DTMIterator is a somewhat unusual type of iterator, in that it can serve both single node iteration and random access.

The DTMIterator's traversal semantics, i.e. how it walks the tree, are specified when it is created, possibly and probably by an XPath UnionExpr.

A DTMIterator is meant to be created once as a master static object, and then cloned many times for runtime use. Or the master object itself may be used for simpler use cases.

At this time, we do not expect DTMIterator to emulate NodeIterator's "maintain relative position" semantics under document mutation. It's likely to respond more like the TreeWalker's "current node" semantics. However, since the base DTM is immutable, this issue currently makes no practical difference.

State: In progress!!

Fields Summary
public static final short
FILTER_ACCEPT
Accept the node.
public static final short
FILTER_REJECT
Reject the node. Same behavior as FILTER_SKIP. (In the DOM these differ when applied to a TreeWalker but have the same result when applied to a NodeIterator).
public static final short
FILTER_SKIP
Skip this single node.
Constructors Summary
Methods Summary
public voidallowDetachToRelease(boolean allowRelease)
Specify if it's OK for detach to release the iterator for reuse.

param
allowRelease true if it is OK for detach to release this iterator for pooling.

public java.lang.Objectclone()
Get a clone of this iterator, but don't reset the iteration in the process, so that it may be used from the current position.

return
A clone of this object.
throws
CloneNotSupportedException

public com.sun.org.apache.xml.internal.dtm.DTMIteratorcloneWithReset()
Get a cloned Iterator that is reset to the start of the iteration.

return
A clone of this iteration that has been reset.
throws
CloneNotSupportedException

public voiddetach()
Detaches the DTMIterator from the set which it iterated over, releasing any computational resources and placing the iterator in the INVALID state. After detach has been invoked, calls to nextNode or previousNode will raise a runtime exception.

public intgetAxis()
Returns the axis being iterated, if it is known.

return
Axis.CHILD, etc., or -1 if the axis is not known or is of multiple types.

public intgetCurrentNode()
Get the current node in the iterator. Note that this differs from the DOM's NodeIterator, where the current position lies between two nodes (as part of the maintain-relative-position semantic).

return
The current node handle, or -1.

public intgetCurrentPos()
Get the current position within the cached list, which is one less than the next nextNode() call will retrieve. i.e. if you call getCurrentPos() and the return is 0, the next fetch will take place at index 1.

return
The position of the iteration.

public com.sun.org.apache.xml.internal.dtm.DTMgetDTM(int nodeHandle)
Get an instance of a DTM that "owns" a node handle. Since a node iterator may be passed without a DTMManager, this allows the caller to easily get the DTM using just the iterator.

param
nodeHandle the nodeHandle.
return
a non-null DTM reference.

public com.sun.org.apache.xml.internal.dtm.DTMManagergetDTMManager()
Get an instance of the DTMManager. Since a node iterator may be passed without a DTMManager, this allows the caller to easily get the DTMManager using just the iterator.

return
a non-null DTMManager reference.

public booleangetExpandEntityReferences()

The value of this flag determines whether the children of entity reference nodes are visible to the iterator. If false, they and their descendants will be rejected. Note that this rejection takes precedence over whatToShow and the filter.

To produce a view of the document that has entity references expanded and does not expose the entity reference node itself, use the whatToShow flags to hide the entity reference node and set expandEntityReferences to true when creating the iterator. To produce a view of the document that has entity reference nodes but no entity expansion, use the whatToShow flags to show the entity reference node and set expandEntityReferences to false.

NOTE: In Xalan's use of DTM we will generally have fully expanded entity references when the document tree was built, and thus this flag will have no effect.

return
true if entity references will be expanded.

public intgetLength()
The number of nodes in the list. The range of valid child node indices is 0 to length-1 inclusive. Note that this requires running the iterator to completion, and presumably filling the cache.

return
The number of nodes in the list.

public intgetRoot()
The root node of the DTMIterator, as specified when it was created. Note the root node is not the root node of the document tree, but the context node from where the iteration begins and ends.

return
nodeHandle int Handle of the context node.

public intgetWhatToShow()
This attribute determines which node types are presented via the iterator. The available set of constants is defined above. Nodes not accepted by whatToShow will be skipped, but their children may still be considered.

return
one of the SHOW_XXX constants, or several ORed together.

public booleanisDocOrdered()
Returns true if all the nodes in the iteration well be returned in document order.

return
true if all the nodes in the iteration well be returned in document order.

public booleanisFresh()
Tells if this NodeSetDTM is "fresh", in other words, if the first nextNode() that is called will return the first node in the set.

return
true if the iteration of this list has not yet begun.

public booleanisMutable()
Tells if this iterator can have nodes added to it or set via the setItem(int node, int index) method.

return
True if the nodelist can be mutated.

public intitem(int index)
Returns the node handle of an item in the collection. If index is greater than or equal to the number of nodes in the list, this returns null.

param
index of the item.
return
The node handle at the indexth position in the DTMIterator, or -1 if that is not a valid index.

public intnextNode()
Returns the next node in the set and advances the position of the iterator in the set. After a DTMIterator has setRoot called, the first call to nextNode() returns that root or (if it is rejected by the filters) the first node within its subtree which is not filtered out.

return
The next node handle in the set being iterated over, or DTM.NULL if there are no more members in that set.

public intpreviousNode()
Returns the previous node in the set and moves the position of the DTMIterator backwards in the set.

return
The previous node handle in the set being iterated over, or DTM.NULL if there are no more members in that set.

public voidreset()
Reset the iterator to the start. After resetting, the next node returned will be the root node -- or, if that's filtered out, the first node within the root's subtree which is _not_ skipped by the filters.

public voidrunTo(int index)
If an index is requested, NodeSetDTM will call this method to run the iterator to the index. By default this sets m_next to the index. If the index argument is -1, this signals that the iterator should be run to the end and completely fill the cache.

param
index The index to run to, or -1 if the iterator should be run to the end.

public voidsetCurrentPos(int i)
Set the current position in the node set.

param
i Must be a valid index.

public voidsetItem(int node, int index)
Sets the node at the specified index of this vector to be the specified node. The previous component at that position is discarded.

The index must be a value greater than or equal to 0 and less than the current size of the vector. The iterator must be in cached mode.

Meant to be used for sorted iterators.

param
node Node to set
param
index Index of where to set the node

public voidsetRoot(int nodeHandle, java.lang.Object environment)
Reset the root node of the DTMIterator, overriding the value specified when it was created. Note the root node is not the root node of the document tree, but the context node from where the iteration begins.

param
nodeHandle int Handle of the context node.
param
environment The environment object. The environment in which this iterator operates, which should provide:
  • a node (the context node... same value as "root" defined below)
  • a pair of non-zero positive integers (the context position and the context size)
  • a set of variable bindings
  • a function library
  • the set of namespace declarations in scope for the expression.
    • At this time the exact implementation of this environment is application dependent. Probably a proper interface will be created fairly soon.

public voidsetShouldCacheNodes(boolean b)
If setShouldCacheNodes(true) is called, then nodes will be cached, enabling random access, and giving the ability to do sorts and the like. They are not cached by default. %REVIEW% Shouldn't the other random-access methods throw an exception if they're called on a DTMIterator with this flag set false?

param
b true if the nodes should be cached.