Package org.loboevolution.apache.xml.dtm

Interface DTMIterator

All Known Implementing Classes:
AttributeIterator, BasicTestIterator, ChildIterator, ChildTestIterator, DescendantIterator, LocPathIterator, NodeSequence, NodeSetDTM, OneStepIterator, OneStepIteratorForward, SelfIteratorNoPredicate, UnionChildIterator, UnionPathIterator, WalkingIterator, WalkingIteratorSorted, XNodeSet
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 LocationPath or a 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

    Fields
    Modifier and Type
    Field
    Description
    static final short
    FILTER_ACCEPT
    Accept the node.
    static final short
    FILTER_SKIP
    Skip this single node.

  • Method Summary

    Modifier and Type
    Method
    Description
    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.
    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
    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.

  • Field Details

  • Method Details

    • getDTM

      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.
      Parameters:
      nodeHandle - the nodeHandle.
      Returns:
      a non-null DTM reference.

    • getDTMManager

      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.
      Returns:
      a non-null DTMManager reference.

    • getRoot

      int getRoot()
      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.
      Returns:
      nodeHandle int Handle of the context node.

    • setRoot

      void setRoot(int nodeHandle, 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.
      Parameters:
      nodeHandle - 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.

    • reset

      void reset()
      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.

    • getWhatToShow

      int getWhatToShow()
      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.
      Returns:
      one of the SHOW_XXX constants, or several ORed together.

    • getExpandEntityReferences

      boolean getExpandEntityReferences()
      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.

    • nextNode

      int nextNode()
      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.
      Returns:
      The next node handle in the set being iterated over, or DTM.NULL if there are no more members in that set.

    • previousNode

      int previousNode()
      Returns the previous node in the set and moves the position of the 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.

    • detach

      void detach()
      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.

    • allowDetachToRelease

      void allowDetachToRelease(boolean allowRelease)
      Specify if it's OK for detach to release the iterator for reuse.
      Parameters:
      allowRelease - true if it is OK for detach to release this iterator for pooling.

    • getCurrentNode

      int getCurrentNode()
      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).
      Returns:
      The current node handle, or -1.

    • isFresh

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

    • setShouldCacheNodes

      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. 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?

      Parameters:
      b - true if the nodes should be cached.

    • getCurrentPos

      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.
      Returns:
      The position of the iteration.

    • runTo

      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 and completely fill the cache.
      Parameters:
      index - The index to run to, or -1 if the iterator should be run to the end.

    • setCurrentPos

      void setCurrentPos(int i)
      Set the current position in the node set.
      Parameters:
      i - Must be a valid index.

    • item

      int item(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.
      Parameters:
      index - of the item.
      Returns:
      The node handle at the indexth position in the DTMIterator, or -1 if that is not a valid index.

    • getLength

      int getLength()
      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.
      Returns:
      The number of nodes in the list.

    • cloneWithReset

      DTMIterator cloneWithReset() throws CloneNotSupportedException
      Get a cloned Iterator that is reset to the start of the iteration.
      Returns:
      A clone of this iteration that has been reset.
      Throws:
      CloneNotSupportedException - if any

    • clone

      Object clone() throws CloneNotSupportedException
      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.
      Returns:
      A clone of this object.
      Throws:
      CloneNotSupportedException - if any

    • isDocOrdered

      boolean isDocOrdered()
      Returns true if all the nodes in the iteration well be returned in document order.
      Returns:
      true if all the nodes in the iteration well be returned in document order.

    • getAxis

      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.