Package 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:
Serializable, Cloneable, SourceLocator, DTMIterator, PathComponent, SubContextList, ExpressionNode, 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

  • Field Details

    • 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_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_execContext

      protected transient XPathContext m_execContext
      The XPathContext reference, needed for execution of many operations.

  • Constructor Details

    • 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 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:
      TransformerException

    • LocPathIterator

      protected LocPathIterator​(Compiler compiler, int opPos, int analysis, boolean shouldLoadWalkers) throws 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:
      TransformerException

  • Method Details

    • 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.

    • 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 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:
      TransformerException

    • executeCharsToContentHandler

      public void executeCharsToContentHandler​(XPathContext xctxt, ContentHandler handler) throws TransformerException, 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.
      Throws:
      TransformerException - if a runtime exception occurs.
      SAXException

    • asIterator

      public DTMIterator asIterator​(XPathContext xctxt, int contextNode) throws 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:
      TransformerException - thrown if the active ProblemListener decides the error condition is severe enough to halt processing.
      TransformerException

    • isNodesetExpr

      public boolean isNodesetExpr()
      Tell if the expression is a nodeset expression.
      Overrides:
      isNodesetExpr in class Expression
      Returns:
      true if the expression can be represented as a nodeset.

    • asNode

      public int asNode​(XPathContext xctxt) throws 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:
      TransformerException

    • bool

      public boolean bool​(XPathContext xctxt) throws 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:
      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 - The XPath runtime context for this transformation.
      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
      Parameters:
      owner - The owner of the visitor, where that path may be rewritten if needed.
      visitor - The visitor whose appropriate method will be called.
      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)