Package net.sf.saxon.om

Interface SequenceIterator<T extends Item<?>>

All Superinterfaces:
AutoCloseable, Closeable
All Known Subinterfaces:
AtomicIterator, AtomizedValueIterator<T>, AxisIterator, FocusIterator<T>, GroundedIterator<T>, GroupIterator, LookaheadIterator<T>, RegexIterator, ReversibleIterator<T>, UnfailingIterator<T>
All Known Implementing Classes:
AdjacentTextNodeMergingIterator, AncestorEnumeration, AncestorIterator, ARegexIterator, ArrayIterator, ArrayIterator.OfNodes, ATokenIterator, AtomizingIterator, AttributeEnumeration, AttributeIterator, AxisAtomizingIterator, BigRangeIterator, BlockIterator, CardinalityCheckingIterator, ChildEnumeration, ConcatenatingAxisIterator, ContextMappingIterator, DescendantIterator, DescendantIteratorSansText, DifferenceEnumeration, DistinctValues.DistinctIterator, DocumentOrderIterator, EmptyIterator, EmptyIterator.OfAtomic, EmptyIterator.OfNodes, ErrorIterator, EveryItemMappingIterator, FilterIterator, FilterIterator.NonNumeric, FocusTrackingIterator, FollowingEnumeration, FollowingIterator, FollowingSiblingEnumeration, GraftingDescendantIterator, GroupAdjacentIterator, GroupByIterator, GroupEndingIterator, GroupMatchingIterator, GroupStartingIterator, HomogeneityCheckerIterator, InsertBefore.InsertIterator, IntersectionEnumeration, ItemMappingIterator, JRegexIterator, JTokenIterator, ListIterator, ListIterator.Atomic, ListIterator.OfNodes, LookaheadIteratorImpl, ManualIterator, MappingIterator, MemoSequence.ProgressiveIterator, MergeGroupingIterator, MergeIterator, NamedChildIterator, Navigator.AncestorEnumeration, Navigator.AxisFilter, Navigator.DescendantEnumeration, Navigator.EmptyTextFilter, Navigator.FollowingEnumeration, Navigator.PrecedingEnumeration, NodeWrappingAxisIterator, PrecedingEnumeration, PrecedingIterator, PrecedingOrAncestorEnumeration, PrecedingSiblingEnumeration, PrecedingSiblingIterator, PrependAxisIterator, PrependSequenceIterator, RangeIterator, Remove.RemoveIterator, ReturnClauseIterator, ReverseListIterator, ReverseRangeIterator, SiblingIterator, SingleAtomicIterator, SingleNodeIterator, SingletonIterator, SortedGroupIterator, SortedIterator, SteppingNavigator.DescendantAxisIterator, StringValue.CharacterIterator, StringValue.UnicodeCharacterIterator, SubsequenceIterator, TailIterator, TextLinesIterator, TreeEnumeration, UnionEnumeration, UnparsedTextIterator, UntypedAtomizingIterator, ValueTailIterator, VirtualCopy.VirtualCopier, Whitespace.Tokenizer, WrappingIterator
public interface SequenceIterator<T extends Item<?>> extends Closeable
A SequenceIterator is used to iterate over any XPath 2 sequence (of values or nodes). To get the next item in a sequence, call next(); if this returns null, you've reached the end of the sequence.

The objects returned by the SequenceIterator will generally be either nodes (class NodeInfo), singleton values (class AtomicValue), or function items: these are represented collectively by the interface Item.

The interface to SequenceIterator is changed in Saxon 9.6 to drop support for the current() and position() methods. Internal iterators no longer need to maintain the values of the current item or the current position. This information is needed (in general) only for an iterator that acts as the current focus; that is, an iterator stored as the current iterator in an XPathContext. SequenceIterators than maintain the value of position() and last() are represented by the interface FocusIterator.

Since:
8.4; significant changes in 9.6.
Author:
Michael H. Kay

  • Field Summary

    Fields
    Modifier and Type
    Field
    Description
    static final int
    ATOMIZING
    Property value: the iterator can deliver an atomized result.
    static final int
    GROUNDED
    Property value: the iterator is "grounded".
    static final int
    LAST_POSITION_FINDER
    Property value: the iterator knows the number of items that it will deliver.
    static final int
    LOOKAHEAD
    Property value: the iterator knows whether there are more items still to come.

  • Method Summary

    Modifier and Type
    Method
    Description
    default void
    close()
    Close the iterator.
    default void
    forEachOrFail(ItemConsumer<T> consumer)
    Process all the remaining items delivered by the SequenceIterator using a supplied consumer function.
    default int
    getProperties()
    Get properties of this iterator, as a bit-significant integer.
    default GroundedValue<T>
    materialize()
    Create a GroundedValue (a sequence materialized in memory) containing all the values delivered by this SequenceIterator.
    T
    next()
    Get the next item in the sequence.

  • Field Details

    • GROUNDED

      static final int GROUNDED
      Property value: the iterator is "grounded". This means that (a) the iterator must be an instance of GroundedIterator, and (b) the implementation of the materialize() method must be efficient (in particular, it should not involve the creation of new objects)
      See Also:

    • LAST_POSITION_FINDER

      static final int LAST_POSITION_FINDER
      Property value: the iterator knows the number of items that it will deliver. This means that (a) the iterator must be an instance of LastPositionFinder, and (b) the implementation of the getLastPosition() method must be efficient (in particular, it should take constant time, rather than time proportional to the length of the sequence)
      See Also:

    • LOOKAHEAD

      static final int LOOKAHEAD
      Property value: the iterator knows whether there are more items still to come. This means that (a) the iterator must be an instance of LookaheadIterator, and (b) the implementation of the hasNext() method must be efficient (more efficient than the client doing it)
      See Also:

    • ATOMIZING

      static final int ATOMIZING
      Property value: the iterator can deliver an atomized result. This means that the iterator must be an instance of AtomizingIterator.
      See Also:

  • Method Details

    • next

      T next() throws XPathException
      Get the next item in the sequence. This method changes the state of the iterator.
      Returns:
      the next item, or null if there are no more items. Once a call on next() has returned null, no further calls should be made. The preferred action for an iterator if subsequent calls on next() are made is to return null again, and all implementations within Saxon follow this rule.
      Throws:
      XPathException - if an error occurs retrieving the next item
      Since:
      8.4

    • close

      default void close()
      Close the iterator. This indicates to the supplier of the data that the client does not require any more items to be delivered by the iterator. This may enable the supplier to release resources. After calling close(), no further calls on the iterator should be made; if further calls are made, the effect of such calls is undefined.

      For example, the iterator returned by the unparsed-text-lines() function has a close() method that causes the underlying input stream to be closed, whether or not the file has been read to completion.

      Closing an iterator is important when the data is being "pushed" in another thread. Closing the iterator terminates that thread and means that it needs to do no additional work. Indeed, failing to close the iterator may cause the push thread to hang waiting for the buffer to be emptied.

      Specified by:
      close in interface AutoCloseable
      Specified by:
      close in interface Closeable
      Since:
      9.1. Default implementation added in 9.9.

    • getProperties

      default int getProperties()
      Get properties of this iterator, as a bit-significant integer.
      Returns:
      the properties of this iterator. This will be some combination of properties such as GROUNDED, LAST_POSITION_FINDER, and LOOKAHEAD. It is always acceptable to return the value zero, indicating that there are no known special properties. It is acceptable for the properties of the iterator to change depending on its state.
      Since:
      8.6. Default implementation added in 9.9.

    • forEachOrFail

      default void forEachOrFail(ItemConsumer<T> consumer) throws XPathException
      Process all the remaining items delivered by the SequenceIterator using a supplied consumer function.
      Parameters:
      consumer - the supplied consumer function
      Throws:
      XPathException - if either (a) an error occurs obtaining an item from the input sequence, or (b) the consumer throws an exception.

    • materialize

      default GroundedValue<T> materialize() throws XPathException
      Create a GroundedValue (a sequence materialized in memory) containing all the values delivered by this SequenceIterator. The method must only be used when the SequenceIterator is positioned at the start. If it is not positioned at the start, then it is implementation-dependant whether the returned sequence contains all the nodes delivered by the SequenceIterator from the beginning, or only those delivered starting at the current position.

      It is implementation-dependant whether this method consumes the SequenceIterator. (More specifically, in the current implementation: if the iterator is backed by a GroundedValue, then that value is returned and the iterator is not consumed; otherwise, the iterator is consumed and the method returns the remaining items after the current position only).

      Returns:
      a sequence containing all the items delivered by this SequenceIterator.
      Throws:
      XPathException - if reading the SequenceIterator throws an error