public interface SequenceIterator extends java.io.Closeable
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
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
|Modifier and Type||Interface and Description|
|Modifier and Type||Method and Description|
Close the iterator.
Process all the remaining items delivered by the SequenceIterator using a supplied consumer function.
Get properties of this iterator.
Create a GroundedValue (a sequence materialized in memory) containing all the values delivered by this SequenceIterator.
Get the next item in the sequence.
Item next() throws XPathException
XPathException- if an error occurs retrieving the next item
default void close()
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.
default java.util.EnumSet<SequenceIterator.Property> getProperties()
SequenceIterator.Property.LOOKAHEAD. It is always acceptable to return the default value
EnumSet.noneOf(Property.class), indicating that there are no known special properties. It is acceptable (though unusual) for the properties of the iterator to change depending on its state.
default void forEachOrFail(ItemConsumer<? super Item> consumer) throws XPathException
consumer- the supplied consumer function
XPathException- if either (a) an error occurs obtaining an item from the input sequence, or (b) the consumer throws an exception.
default GroundedValue materialize() throws XPathException
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).
XPathException- if reading the SequenceIterator throws an error
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