org.apache.xml.dtm
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!!
Field Summary | |
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static short | FILTER_ACCEPT
Accept the node. |
static short | FILTER_REJECT
Reject the node. |
static short | FILTER_SKIP
Skip this single node. |
Method Summary | |
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void | allowDetachToRelease(boolean allowRelease)
Specify if it's OK for detach to release the iterator for reuse.
|
Object | clone()
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.
|
DTMIterator | cloneWithReset()
Get a cloned Iterator that is reset to the start of the iteration.
|
void | detach()
Detaches the DTMIterator from the set which it iterated
over, releasing any computational resources and placing the iterator
in the INVALID state. |
int | getAxis()
Returns the axis being iterated, if it is known.
|
int | getCurrentNode()
Get the current node in the iterator. |
int | getCurrentPos() 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.
|
DTM | getDTM(int nodeHandle)
Get an instance of a DTM that "owns" a node handle. |
DTMManager | getDTMManager()
Get an instance of the DTMManager. |
boolean | getExpandEntityReferences() The value of this flag determines whether the children of entity reference nodes are visible to the iterator. |
int | getLength()
The number of nodes in the list. |
int | getRoot()
The root node of the DTMIterator , as specified when it
was created. |
int | getWhatToShow()
This attribute determines which node types are presented via the
iterator. |
boolean | isDocOrdered()
Returns true if all the nodes in the iteration well be returned in document
order.
|
boolean | isFresh()
Tells if this NodeSetDTM is "fresh", in other words, if
the first nextNode() that is called will return the
first node in the set.
|
boolean | isMutable()
Tells if this iterator can have nodes added to it or set via
the setItem(int node, int index) method.
|
int | item(int index)
Returns the node handle of an item in the collection. |
int | nextNode()
Returns the next node in the set and advances the position of the
iterator in the set. |
int | previousNode()
Returns the previous node in the set and moves the position of the
DTMIterator backwards in the set. |
void | reset()
Reset the iterator to the start. |
void | runTo(int index)
If an index is requested, NodeSetDTM will call this method
to run the iterator to the index. |
void | setCurrentPos(int i)
Set the current position in the node set.
|
void | setItem(int node, int index)
Sets the node at the specified index of this vector to be the
specified node. |
void | setRoot(int nodeHandle, Object environment)
Reset the root node of the DTMIterator , overriding
the value specified when it was created. |
void | setShouldCacheNodes(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. |
Parameters: allowRelease true if it is OK for detach to release this iterator for pooling.
Returns: A clone of this object.
Throws: CloneNotSupportedException
Returns: A clone of this iteration that has been reset.
Throws: CloneNotSupportedException
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.Returns: Axis.CHILD, etc., or -1 if the axis is not known or is of multiple types.
Returns: The current node handle, or -1.
Returns: The position of the iteration.
Parameters: nodeHandle the nodeHandle.
Returns: a non-null DTM reference.
Returns: a non-null DTMManager reference.
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.
Returns: true if entity references will be expanded.
length-1
inclusive. Note that this requires running
the iterator to completion, and presumably filling the cache.
Returns: The number of nodes in the list.
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.
Returns: nodeHandle int Handle of the context node.
whatToShow
will be skipped, but their children may still
be considered.
Returns: one of the SHOW_XXX constants, or several ORed together.
Returns: true if all the nodes in the iteration well be returned in document order.
Returns: true if the iteration of this list has not yet begun.
setItem(int node, int index)
method.
Returns: True if the nodelist can be mutated.
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
.
Parameters: index of the item.
Returns: The node handle at the index
th position in the
DTMIterator
, or -1
if that is not a valid
index.
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.Returns: The next node handle in the set being iterated over, or
DTM.NULL
if there are no more members in that set.
DTMIterator
backwards in the set.Returns: The previous node handle in the set being iterated over,
or DTM.NULL
if there are no more members in that set.
Parameters: index The index to run to, or -1 if the iterator should be run to the end.
Parameters: i Must be a valid index.
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.
Parameters: node Node to set index Index of where to set the node
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.
Parameters: nodeHandle int Handle of the context node. environment The environment object.
The environment in which this iterator operates, which should provide:
At this time the exact implementation of this environment is application
dependent. Probably a proper interface will be created fairly soon.
Parameters: b true if the nodes should be cached.