org.apache.xpath.axes
Class AxesWalker

java.lang.Object
  |
  +--org.apache.xpath.Expression
        |
        +--org.apache.xpath.patterns.NodeTest
              |
              +--org.apache.xpath.axes.PredicatedNodeTest
                    |
                    +--org.apache.xpath.axes.AxesWalker
Direct Known Subclasses:
FilterExprWalker, ReverseAxesWalker

public class AxesWalker
extends PredicatedNodeTest
implements java.lang.Cloneable, PathComponent, ExpressionOwner

Serves as common interface for axes Walkers, and stores common state variables.

See Also:
Serialized Form

Fields inherited from class org.apache.xpath.patterns.NodeTest
SCORE_NODETEST, SCORE_NONE, SCORE_NSWILD, SCORE_OTHER, SCORE_QNAME, SHOW_BYFUNCTION, SUPPORTS_PRE_STRIPPING, WILD
 
Constructor Summary
AxesWalker(LocPathIterator locPathIterator, int axis)
          Construct an AxesWalker using a LocPathIterator.
 
Method Summary
 void callVisitors(ExpressionOwner owner, XPathVisitor visitor)
          This will traverse the heararchy, calling the visitor for each member.
 java.lang.Object clone()
          Get a cloned AxesWalker.
 boolean deepEquals(Expression expr)
           
 void detach()
          Detaches the walker from the set which it iterated over, releasing any computational resources and placing the iterator in the INVALID state.
 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 getCurrentNode()
          The node at which the TreeWalker is currently positioned.
 DTM getDTM(int node)
          Get the DTM for this walker.
 Expression getExpression()
           
 int getLastPos(XPathContext xctxt)
          Get the index of the last node that can be itterated to.
 AxesWalker getNextWalker()
          Get the next walker in the location step chain.
 AxesWalker getPrevWalker()
          Get the previous walker reference in the location step chain.
 int getRoot()
          The root node of the TreeWalker, as specified in setRoot(int root).
 void init(Compiler compiler, int opPos, int stepType)
          Initialize an AxesWalker during the parse of the XPath expression.
 boolean isDocOrdered()
          Returns true if all the nodes in the iteration well be returned in document order.
 int nextNode()
          Moves the TreeWalker to the next visible node in document order relative to the current node, and returns the new node.
 void setDefaultDTM(DTM dtm)
          Set the DTM for this walker.
 void setExpression(Expression exp)
           
 void setNextWalker(AxesWalker walker)
          Set the next walker in the location step chain.
 void setPrevWalker(AxesWalker walker)
          Set or clear the previous walker reference in the location step chain.
 void setRoot(int root)
          Set the root node of the TreeWalker.
 WalkingIterator wi()
           
 
Methods inherited from class org.apache.xpath.axes.PredicatedNodeTest
acceptNode, callPredicateVisitors, canTraverseOutsideSubtree, fixupVariables, getLocPathIterator, getPredicate, getPredicateCount, getPredicateIndex, getProximityPosition, getProximityPosition, initProximityPosition, isReverseAxes, resetProximityPositions, setLocPathIterator, setPredicateCount
 
Methods inherited from class org.apache.xpath.patterns.NodeTest
debugWhatToShow, execute, execute, execute, getDefaultScore, getLocalName, getNamespace, getNodeTypeTest, getStaticScore, getWhatToShow, initNodeTest, initNodeTest, setLocalName, setNamespace, setStaticScore, setWhatToShow
 
Methods inherited from class org.apache.xpath.Expression
asIterator, asIteratorRaw, asNode, assertion, bool, error, execute, executeCharsToContentHandler, exprAddChild, exprGetChild, exprGetNumChildren, exprGetParent, exprSetParent, getColumnNumber, getExpressionOwner, getLineNumber, getPublicId, getSystemId, isNodesetExpr, isStableNumber, num, warn, xstr
 
Methods inherited from class java.lang.Object
equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Constructor Detail

AxesWalker

public AxesWalker(LocPathIterator locPathIterator,
                  int axis)
Construct an AxesWalker using a LocPathIterator.
Parameters:
locPathIterator - non-null reference to the parent iterator.
Method Detail

wi

public final WalkingIterator wi()

init

public void init(Compiler compiler,
                 int opPos,
                 int stepType)
          throws TransformerException
Initialize an AxesWalker during the parse of the XPath expression.
Parameters:
compiler - The Compiler object that has information about this walker in the op map.
opPos - The op code position of this location step.
stepType - The type of location step.
Throws:
TransformerException -  

clone

public java.lang.Object clone()
                       throws java.lang.CloneNotSupportedException
Get a cloned AxesWalker.
Returns:
A new AxesWalker that can be used without mutating this one.
Throws:
java.lang.CloneNotSupportedException -  
Overrides:
clone in class PredicatedNodeTest

detach

public void detach()
Detaches the walker from the set which it iterated over, releasing any computational resources and placing the iterator in the INVALID state.

getRoot

public int getRoot()
The root node of the TreeWalker, as specified in setRoot(int root). Note that this may actually be below the current node.
Returns:
The context node of the step.

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.

setRoot

public void setRoot(int root)
Set the root node of the TreeWalker. (Not part of the DOM2 TreeWalker interface).
Parameters:
root - The context node of this step.

getCurrentNode

public final int getCurrentNode()
The node at which the TreeWalker is currently positioned.
The value must not be null. Alterations to the DOM tree may cause the current node to no longer be accepted by the TreeWalker's associated filter. currentNode may also be explicitly set to any node, whether or not it is within the subtree specified by the root node or would be accepted by the filter and whatToShow flags. Further traversal occurs relative to currentNode even if it is not part of the current view by applying the filters in the requested direction (not changing currentNode where no traversal is possible).
Returns:
The node at which the TreeWalker is currently positioned, only null if setRoot has not yet been called.

setNextWalker

public void setNextWalker(AxesWalker walker)
Set the next walker in the location step chain.
Parameters:
walker - Reference to AxesWalker derivative, or may be null.

getNextWalker

public AxesWalker getNextWalker()
Get the next walker in the location step chain.
Returns:
Reference to AxesWalker derivative, or null.

setPrevWalker

public void setPrevWalker(AxesWalker walker)
Set or clear the previous walker reference in the location step chain.
Parameters:
walker - Reference to previous walker reference in the location step chain, or null.

getPrevWalker

public AxesWalker getPrevWalker()
Get the previous walker reference in the location step chain.
Returns:
Reference to previous walker reference in the location step chain, or null.

nextNode

public int nextNode()
Moves the TreeWalker to the next visible node in document order relative to the current node, and returns the new node. If the current node has no next node, or if the search for nextNode attempts to step upward from the TreeWalker's root node, returns null , and retains the current node.
Returns:
The new node, or null if the current node has no next node in the TreeWalker's logical view.

getLastPos

public int getLastPos(XPathContext xctxt)
Get the index of the last node that can be itterated to.
Parameters:
xctxt - XPath runtime context.
Returns:
the index of the last node that can be itterated to.
Overrides:
getLastPos in class PredicatedNodeTest

setDefaultDTM

public void setDefaultDTM(DTM dtm)
Set the DTM for this walker.
Parameters:
dtm - Non-null reference to a DTM.

getDTM

public DTM getDTM(int node)
Get the DTM for this walker.
Returns:
Non-null reference to a DTM.

isDocOrdered

public boolean isDocOrdered()
Returns true if all the nodes in the iteration well be returned in document order. Warning: This can only be called after setRoot has been called!
Returns:
true as a default.

getAxis

public int getAxis()
Returns the axis being iterated, if it is known.
Returns:
Axis.CHILD, etc., or -1 if the axis is not known or is of multiple types.

callVisitors

public void callVisitors(ExpressionOwner owner,
                         XPathVisitor visitor)
This will traverse the heararchy, calling the visitor for each member. If the called visitor method returns false, the subtree should not be called.
Parameters:
owner - The owner of the visitor, where that path may be rewritten if needed.
visitor - The visitor whose appropriate method will be called.
Overrides:
callVisitors in class NodeTest

getExpression

public Expression getExpression()
Specified by:
getExpression in interface ExpressionOwner
See Also:
ExpressionOwner.getExpression()

setExpression

public void setExpression(Expression exp)
Specified by:
setExpression in interface ExpressionOwner
See Also:
ExpressionOwner.setExpression(Expression)

deepEquals

public boolean deepEquals(Expression expr)
Overrides:
deepEquals in class PredicatedNodeTest
See Also:
Expression.deepEquals(Expression)


Copyright 2006 Apache XML Project. All Rights Reserved.