org.apache.xpath.axes
Class LocPathIterator

java.lang.Object
  org.apache.xpath.Expression
      org.apache.xpath.patterns.NodeTest
          org.apache.xpath.axes.PredicatedNodeTest
              org.apache.xpath.axes.LocPathIterator

All Implemented Interfaces:

Cloneable, DTMIterator, ExpressionNode, PathComponent, Serializable, javax.xml.transform.SourceLocator, SubContextList, XPathVisitable

Direct Known Subclasses:

BasicTestIterator, ChildIterator, DescendantIterator, FilterExprIteratorSimple, MatchPatternIterator, SelfIteratorNoPredicate, UnionPathIterator, WalkingIterator

public abstract class LocPathIterator

extends PredicatedNodeTest

implements Cloneable, DTMIterator, Serializable, PathComponent

This class extends NodeSetDTM, which implements NodeIterator, and fetches nodes one at a time in document order based on a XPath

See Also:

Serialized Form

Nested Class Summary

Nested classes inherited from class org.apache.xpath.axes.PredicatedNodeTest

PredicatedNodeTest.PredOwner

Field Summary

protected boolean	m_allowDetach Control over whether it is OK for detach to reset the iterator.
protected DTM	m_cdtm The dtm of the context node.
protected IteratorPool	m_clones The pool for cloned iterators.
protected int	m_context The context node for this iterator, which doesn't change through the course of the iteration.
protected int	m_currentContextNode The node context from where the expression is being executed from (i.e. for current() support).
protected XPathContext	m_execContext The XPathContext reference, needed for execution of many operations.
private boolean	m_isTopLevel Value determined at compile time, indicates that this is an iterator at the top level of the expression, rather than inside a predicate.
int	m_lastFetched The last node that was fetched, usually by nextNode.
protected int	m_length
protected int	m_pos The current position of the context node.
private PrefixResolver	m_prefixResolver Fast access to the current prefix resolver.
(package private) int	m_stackFrame The stack frame index for this iterator.

Fields inherited from class org.apache.xpath.axes.PredicatedNodeTest

DEBUG_PREDICATECOUNTING, m_foundLast, m_lpi, m_predCount, m_predicateIndex, m_proximityPositions

Fields inherited from class org.apache.xpath.patterns.NodeTest

m_name, m_whatToShow, SCORE_NODETEST, SCORE_NONE, SCORE_NSWILD, SCORE_OTHER, SCORE_QNAME, SHOW_BYFUNCTION, SUPPORTS_PRE_STRIPPING, WILD

Fields inherited from class org.apache.xpath.Expression

Fields inherited from interface org.apache.xml.dtm.DTMIterator

FILTER_ACCEPT, FILTER_REJECT, FILTER_SKIP

Constructor Summary

protected	LocPathIterator() Create a LocPathIterator object.
protected	LocPathIterator(Compiler compiler, int opPos, int analysis) Create a LocPathIterator object, including creation of step walkers from the opcode list, and call back into the Compiler to create predicate expressions.
protected	LocPathIterator(Compiler compiler, int opPos, int analysis, boolean shouldLoadWalkers) Create a LocPathIterator object, including creation of step walkers from the opcode list, and call back into the Compiler to create predicate expressions.
protected	LocPathIterator(PrefixResolver nscontext) Create a LocPathIterator object.

Method Summary

void	allowDetachToRelease(boolean allowRelease) Specify if it's OK for detach to release the iterator for reuse.
DTMIterator	asIterator(XPathContext xctxt, int contextNode) Given an select expression and a context, evaluate the XPath and return the resulting iterator.
int	asNode(XPathContext xctxt) Return the first node out of the nodeset, if this expression is a nodeset expression.
boolean	bool(XPathContext xctxt) Evaluate this operation directly to a boolean.
void	callVisitors(ExpressionOwner owner, XPathVisitor visitor) This will traverse the heararchy, calling the visitor for each member.
DTMIterator	cloneWithReset() Get a cloned Iterator that is reset to the beginning of the query.
void	detach() Detaches the iterator from the set which it iterated over, releasing any computational resources and placing the iterator in the INVALID state.
XObject	execute(XPathContext xctxt) Execute this iterator, meaning create a clone that can store state, and initialize it for fast execution from the current runtime state.
void	executeCharsToContentHandler(XPathContext xctxt, org.xml.sax.ContentHandler handler) Execute an expression in the XPath runtime context, and return the result of the expression.
int	getAnalysisBits() Get the analysis bits for this walker, as defined in the WalkerFactory.
int	getAxis() Returns the axis being iterated, if it is known.
int	getContext() The node context for the iterator.
int	getCurrentContextNode() The node context from where the expression is being executed from (i.e. for current() support).
int	getCurrentNode() Return the last fetched node.
int	getCurrentPos() Get the current position, which is one less than the next nextNode() call will retrieve.
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.
DTMFilter	getFilter() The filter used to screen nodes.
boolean	getFoundLast() Tells if we've found the last node yet.
boolean	getIsTopLevel() Get if this is an iterator at the upper level of the XPath.
int	getLastPos(XPathContext xctxt) Get the index of the last node that can be itterated to.
int	getLength() The number of nodes in the list.
PrefixResolver	getPrefixResolver() Return the saved reference to the prefix resolver that was in effect when this iterator was created.
int	getRoot() The root node of the Iterator, as specified when it was created.
int	getWhatToShow() This attribute determines which node types are presented via the iterator.
XPathContext	getXPathContext() The XPath execution context we are operating on.
void	incrementCurrentPos() Increment the current position in the node set.
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.
boolean	isNodesetExpr() Tell if the expression is a nodeset expression.
int	item(int index) Returns the index th item in the collection.
abstract 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 iterator backwards in the set.
private void	readObject(ObjectInputStream stream) Read the object from a serialization stream.
void	reset() Reset the iterator.
protected int	returnNextNode(int nextNode) Bottleneck the return of a next node, to make returns easier from nextNode().
void	runTo(int index) If an index is requested, NodeSetDTM will call this method to run the iterator to the index.
void	setCurrentContextNode(int n) Set the current context node for this iterator.
void	setCurrentPos(int i) Set the current position in the node set.
void	setEnvironment(Object environment) Set 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.
void	setIsTopLevel(boolean b) Set if this is an iterator at the upper level of the XPath.
void	setItem(int node, int index) Sets the node at the specified index of this vector to be the specified node.
protected void	setNextPosition(int next) Set the next position index of this iterator.
void	setRoot(int context, Object environment) Initialize the context values for this expression after it is cloned.
void	setShouldCacheNodes(boolean b) If setShouldCacheNodes(true) is called, then nodes will be cached.
int	size() Get the length of the cached nodes.

Methods inherited from class org.apache.xpath.axes.PredicatedNodeTest

acceptNode, callPredicateVisitors, canTraverseOutsideSubtree, clone, countProximityPosition, deepEquals, executePredicates, fixupVariables, getLocPathIterator, getPredicate, getPredicateCount, getPredicateIndex, getProximityPosition, getProximityPosition, getProximityPosition, initPredicateInfo, initProximityPosition, isReverseAxes, nodeToString, resetProximityPositions, setLocPathIterator, setPredicateCount

Methods inherited from class org.apache.xpath.patterns.NodeTest

calcScore, debugWhatToShow, execute, execute, getDefaultScore, getLocalName, getNamespace, getNodeTypeTest, getStaticScore, initNodeTest, initNodeTest, setLocalName, setNamespace, setStaticScore, setWhatToShow

Methods inherited from class org.apache.xpath.Expression

asIteratorRaw, assertion, error, execute, exprAddChild, exprGetChild, exprGetNumChildren, exprGetParent, exprSetParent, getColumnNumber, getExpressionOwner, getLineNumber, getPublicId, getSystemId, isSameClass, isStableNumber, num, warn, xstr

Methods inherited from class java.lang.Object

equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Methods inherited from interface org.apache.xml.dtm.DTMIterator

clone

Field Detail

m_allowDetach

protected boolean m_allowDetach

Control over whether it is OK for detach to reset the iterator.

m_clones

protected transient IteratorPool m_clones

The pool for cloned iterators. Iterators need to be cloned because the hold running state, and thus the original iterator expression from the stylesheet pool can not be used.

m_cdtm

protected transient DTM m_cdtm

The dtm of the context node. Careful about using this... it may not be the dtm of the current node.

m_stackFrame

transient int m_stackFrame

The stack frame index for this iterator.

m_isTopLevel

private boolean m_isTopLevel

Value determined at compile time, indicates that this is an iterator at the top level of the expression, rather than inside a predicate.

m_lastFetched

public transient int m_lastFetched

The last node that was fetched, usually by nextNode.

m_context

protected transient int m_context

The context node for this iterator, which doesn't change through the course of the iteration.

m_currentContextNode

protected transient int m_currentContextNode

The node context from where the expression is being executed from (i.e. for current() support). Different from m_context in that this is the context for the entire expression, rather than the context for the subexpression.

m_pos

protected transient int m_pos

The current position of the context node.

m_length

protected transient int m_length

m_prefixResolver

private PrefixResolver m_prefixResolver

Fast access to the current prefix resolver. It isn't really clear that this is needed.

m_execContext

protected transient XPathContext m_execContext

The XPathContext reference, needed for execution of many operations.

Constructor Detail

LocPathIterator

protected LocPathIterator()

Create a LocPathIterator object.

LocPathIterator

protected LocPathIterator(PrefixResolver nscontext)

Create a LocPathIterator object.

Parameters:

nscontext - The namespace context for this iterator, should be OK if null.

LocPathIterator

protected LocPathIterator(Compiler compiler,
                          int opPos,
                          int analysis)
                   throws javax.xml.transform.TransformerException

Create a LocPathIterator object, including creation of step walkers from the opcode list, and call back into the Compiler to create predicate expressions.

Parameters:

compiler - The Compiler which is creating this expression.

opPos - The position of this iterator in the opcode list from the compiler.

Throws:

javax.xml.transform.TransformerException

LocPathIterator

protected LocPathIterator(Compiler compiler,
                          int opPos,
                          int analysis,
                          boolean shouldLoadWalkers)
                   throws javax.xml.transform.TransformerException

Create a LocPathIterator object, including creation of step walkers from the opcode list, and call back into the Compiler to create predicate expressions.

Parameters:

compiler - The Compiler which is creating this expression.

opPos - The position of this iterator in the opcode list from the compiler.

shouldLoadWalkers - True if walkers should be loaded, or false if this is a derived iterator and it doesn't wish to load child walkers.

Throws:

javax.xml.transform.TransformerException

Method Detail

getAnalysisBits

public int getAnalysisBits()

Get the analysis bits for this walker, as defined in the WalkerFactory.

Specified by:

getAnalysisBits in interface PathComponent

Returns:

One of WalkerFactory#BIT_DESCENDANT, etc.

readObject

private void readObject(ObjectInputStream stream)
                 throws IOException,
                        javax.xml.transform.TransformerException

Read the object from a serialization stream.

Parameters:

stream - Input stream to read from

Throws:

IOException

javax.xml.transform.TransformerException

setEnvironment

public void setEnvironment(Object environment)

Set 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.

Parameters:

environment - The environment object.

getDTM

public DTM getDTM(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.

Specified by:

getDTM in interface DTMIterator

Parameters:

nodeHandle - the nodeHandle.

Returns:

a non-null DTM reference.

getDTMManager

public DTMManager getDTMManager()

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.

Specified by:

getDTMManager in interface DTMIterator

Returns:

a non-null DTMManager reference.

execute

public XObject execute(XPathContext xctxt)
                throws javax.xml.transform.TransformerException

Execute this iterator, meaning create a clone that can store state, and initialize it for fast execution from the current runtime state. When this is called, no actual query from the current context node is performed.

Overrides:

execute in class NodeTest

Parameters:

xctxt - The XPath execution context.

Returns:

An XNodeSet reference that holds this iterator.

Throws:

javax.xml.transform.TransformerException

executeCharsToContentHandler

public void executeCharsToContentHandler(XPathContext xctxt,
                                         org.xml.sax.ContentHandler handler)
                                  throws javax.xml.transform.TransformerException,
                                         org.xml.sax.SAXException

Execute an expression in the XPath runtime context, and return the result of the expression.

Overrides:

executeCharsToContentHandler in class Expression

Parameters:

xctxt - The XPath runtime context.

handler - The target content handler.

Returns:

The result of the expression in the form of a XObject.

Throws:

javax.xml.transform.TransformerException - if a runtime exception occurs.

org.xml.sax.SAXException

asIterator

public DTMIterator asIterator(XPathContext xctxt,
                              int contextNode)
                       throws javax.xml.transform.TransformerException

Given an select expression and a context, evaluate the XPath and return the resulting iterator.

Overrides:

asIterator in class Expression

Parameters:

xctxt - The execution context.

contextNode - The node that "." expresses.

Returns:

A valid DTMIterator.

Throws:

javax.xml.transform.TransformerException - thrown if the active ProblemListener decides the error condition is severe enough to halt processing.

javax.xml.transform.TransformerException

isNodesetExpr

public boolean isNodesetExpr()

Tell if the expression is a nodeset expression. In other words, tell if you can execute asNode without an exception.

Overrides:

isNodesetExpr in class Expression

Returns:

true if the expression can be represented as a nodeset.

asNode

public int asNode(XPathContext xctxt)
           throws javax.xml.transform.TransformerException

Return the first node out of the nodeset, if this expression is a nodeset expression. This is the default implementation for nodesets. Derived classes should try and override this and return a value without having to do a clone operation.

Overrides:

asNode in class Expression

Parameters:

xctxt - The XPath runtime context.

Returns:

the first node out of the nodeset, or DTM.NULL.

Throws:

javax.xml.transform.TransformerException

bool

public boolean bool(XPathContext xctxt)
             throws javax.xml.transform.TransformerException

Evaluate this operation directly to a boolean.

Overrides:

bool in class Expression

Parameters:

xctxt - The runtime execution context.

Returns:

The result of the operation as a boolean.

Throws:

javax.xml.transform.TransformerException

setIsTopLevel

public void setIsTopLevel(boolean b)

Set if this is an iterator at the upper level of the XPath.

Parameters:

b - true if this location path is at the top level of the expression.

getIsTopLevel

public boolean getIsTopLevel()

Get if this is an iterator at the upper level of the XPath.

Returns:

true if this location path is at the top level of the expression.

setRoot

public void setRoot(int context,
                    Object environment)

Initialize the context values for this expression after it is cloned.

Specified by:

setRoot in interface DTMIterator

Parameters:

context - int Handle of the context node.

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.

setNextPosition

protected void setNextPosition(int next)

Set the next position index of this iterator.

Parameters:

next - A value greater than or equal to zero that indicates the next node position to fetch.

getCurrentPos

public final int getCurrentPos()

Get the current position, 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.

Specified by:

getCurrentPos in interface DTMIterator

Returns:

A value greater than or equal to zero that indicates the next node position to fetch.

setShouldCacheNodes

public void setShouldCacheNodes(boolean b)

If setShouldCacheNodes(true) is called, then nodes will be cached. They are not cached by default.

Specified by:

setShouldCacheNodes in interface DTMIterator

Parameters:

b - True if this iterator should cache nodes.

isMutable

public boolean isMutable()

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

Specified by:

isMutable in interface DTMIterator

Returns:

True if the nodelist can be mutated.

setCurrentPos

public void setCurrentPos(int i)

Set the current position in the node set.

Specified by:

setCurrentPos in interface DTMIterator

Parameters:

i - Must be a valid index greater than or equal to zero and less than m_cachedNodes.size().

incrementCurrentPos

public void incrementCurrentPos()

Increment the current position in the node set.

size

public int size()

Get the length of the cached nodes.

Note: for the moment at least, this only returns the size of the nodes that have been fetched to date, it doesn't attempt to run to the end to make sure we have found everything. This should be reviewed.

Returns:

The size of the current cache list.

item

public int item(int index)

Returns the index th item in the collection. If index is greater than or equal to the number of nodes in the list, this returns null .

Specified by:

item in interface DTMIterator

Parameters:

index - Index into the collection.

Returns:

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

setItem

public void setItem(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.

Specified by:

setItem in interface DTMIterator

Parameters:

node - Node to set

index - Index of where to set the node

getLength

public int getLength()

The number of nodes in the list. The range of valid child node indices is 0 to length-1 inclusive.

Specified by:

getLength in interface DTMIterator

Returns:

The number of nodes in the list, always greater or equal to zero.

isFresh

public 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.

Specified by:

isFresh in interface DTMIterator

Returns:

true of nextNode has not been called.

previousNode

public int previousNode()

Returns the previous node in the set and moves the position of the iterator backwards in the set.

Specified by:

previousNode in interface DTMIterator

Returns:

The previous Node in the set being iterated over, ornull if there are no more members in that set.

getWhatToShow

public int getWhatToShow()

This attribute determines which node types are presented via the iterator. The available set of constants is defined in the NodeFilter interface.

This is somewhat useless at this time, since it doesn't really return information that tells what this iterator will show. It is here only to fullfill the DOM NodeIterator interface.

Specified by:

getWhatToShow in interface DTMIterator

Overrides:

getWhatToShow in class NodeTest

Returns:

For now, always NodeFilter.SHOW_ALL & ~NodeFilter.SHOW_ENTITY_REFERENCE.

See Also:

NodeIterator

getFilter

public DTMFilter getFilter()

The filter used to screen nodes. Not used at this time, this is here only to fullfill the DOM NodeIterator interface.

Returns:

Always null.

See Also:

NodeIterator

getRoot

public int getRoot()

The root node of the Iterator, as specified when it was created.

Specified by:

getRoot in interface DTMIterator

Returns:

The "root" of this iterator, which, in XPath terms, is the node context for this iterator.

getExpandEntityReferences

public boolean getExpandEntityReferences()

The value of this flag determines whether the children of entity reference nodes are visible to the iterator. If false, they will be skipped over.
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.

Specified by:

getExpandEntityReferences in interface DTMIterator

Returns:

Always true, since entity reference nodes are not visible in the XPath model.

allowDetachToRelease

public void allowDetachToRelease(boolean allowRelease)

Specify if it's OK for detach to release the iterator for reuse.

Specified by:

allowDetachToRelease in interface DTMIterator

Parameters:

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

detach

public void detach()

Detaches the iterator from the set which it iterated over, releasing any computational resources and placing the iterator in the INVALID state. Afterdetach has been invoked, calls to nextNode orpreviousNode will raise the exception INVALID_STATE_ERR.

Specified by:

detach in interface DTMIterator

reset

public void reset()

Reset the iterator.

Specified by:

reset in interface DTMIterator

cloneWithReset

public DTMIterator cloneWithReset()
                           throws CloneNotSupportedException

Get a cloned Iterator that is reset to the beginning of the query.

Specified by:

cloneWithReset in interface DTMIterator

Returns:

A cloned NodeIterator set of the start of the query.

Throws:

CloneNotSupportedException

nextNode

public abstract int nextNode()

Returns the next node in the set and advances the position of the iterator in the set. After a NodeIterator is created, the first call to nextNode() returns the first node in the set.

Specified by:

nextNode in interface DTMIterator

Returns:

The next Node in the set being iterated over, or null if there are no more members in that set.

returnNextNode

protected int returnNextNode(int nextNode)

Bottleneck the return of a next node, to make returns easier from nextNode().

Parameters:

nextNode - The next node found, may be null.

Returns:

The same node that was passed as an argument.

getCurrentNode

public int getCurrentNode()

Return the last fetched node. Needed to support the UnionPathIterator.

Specified by:

getCurrentNode in interface DTMIterator

Returns:

The last fetched node, or null if the last fetch was null.

runTo

public void runTo(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.

Specified by:

runTo in interface DTMIterator

Parameters:

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

getFoundLast

public final boolean getFoundLast()

Tells if we've found the last node yet.

Returns:

true if the last nextNode returned null.

getXPathContext

public final XPathContext getXPathContext()

The XPath execution context we are operating on.

Returns:

XPath execution context this iterator is operating on, or null if setRoot has not been called.

getContext

public final int getContext()

The node context for the iterator.

Returns:

The node context, same as getRoot().

getCurrentContextNode

public final int getCurrentContextNode()

The node context from where the expression is being executed from (i.e. for current() support).

Returns:

The top-level node context of the entire expression.

setCurrentContextNode

public final void setCurrentContextNode(int n)

Set the current context node for this iterator.

Parameters:

n - Must be a non-null reference to the node context.

getPrefixResolver

public final PrefixResolver getPrefixResolver()

Return the saved reference to the prefix resolver that was in effect when this iterator was created.

Returns:

The prefix resolver or this iterator, which may be null.

callVisitors

public void callVisitors(ExpressionOwner owner,
                         XPathVisitor visitor)

Description copied from interface: XPathVisitable

This will traverse the heararchy, calling the visitor for each member. If the called visitor method returns false, the subtree should not be called.

Specified by:

callVisitors in interface XPathVisitable

Overrides:

callVisitors in class NodeTest

See Also:

XPathVisitable#callVisitors(ExpressionOwner, XPathVisitor)

isDocOrdered

public boolean isDocOrdered()

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

Specified by:

isDocOrdered in interface DTMIterator

Returns:

true as a default.

getAxis

public int getAxis()

Returns the axis being iterated, if it is known.

Specified by:

getAxis in interface DTMIterator

Returns:

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

getLastPos

public int getLastPos(XPathContext xctxt)

Description copied from class: PredicatedNodeTest

Get the index of the last node that can be itterated to.

Specified by:

getLastPos in interface SubContextList

Specified by:

getLastPos in class PredicatedNodeTest

Parameters:

xctxt - XPath runtime context.

Returns:

the index of the last node that can be itterated to.

See Also:

PredicatedNodeTest.getLastPos(XPathContext)