public final class MultithreadedContextMappingIterator extends java.lang.Object implements SequenceIterator
It merges a sequence of sequences into a single flat sequence. It takes as inputs an iteration, and an "action" expression to be applied to each Item returned by that iteration, with that item as the context item. The action expression itself returns another iterator. The result is an iteration of the concatenation of all the iterations returned by the action expression.
|Constructor and Description|
Construct an Iterator that will apply a specified action expression to each Item returned by the current iterator of the supplied dynamic context.
|Modifier and Type||Method and Description|
Close the iterator.
Get the next item in the sequence.
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
public MultithreadedContextMappingIterator(Expression action, XPathContextMinor context, int threads) throws XPathException
action- the mapping expression to be applied
context- the processing context. The action expression is applied to each item returned by context.getCurrentIterator() in turn.
threads- the number of threads to be used (in addition to the base evaluation thread) These threads are used to evaluate the action expression. The current thread is used to evaluate the base iterator and to gather the results of invoking the action expressions in the right order.
public Item next() throws XPathException
XPathException- if an error occurs retrieving the next item
public 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.
Copyright (c) 2004-2021 Saxonica Limited. All rights reserved.