Class ContextMappingIterator

  • All Implemented Interfaces:, java.lang.AutoCloseable, SequenceIterator

    public final class ContextMappingIterator
    extends java.lang.Object
    implements SequenceIterator
    ContextMappingIterator merges a sequence of sequences into a single flat sequence. It takes as inputs an iteration, and a mapping function to be applied to each Item returned by that iteration. The mapping function itself returns another iteration. The result is an iteration of the concatenation of all the iterations returned by the mapping function: often referred to as a flat-map operation.

    This is related to the MappingIterator class: it differs in that it sets each item being processed as the context item

    • Constructor Detail

      • ContextMappingIterator

        public ContextMappingIterator​(ContextMappingFunction action,
                                      XPathContext context)
        Construct a ContextMappingIterator that will apply a specified ContextMappingFunction to each Item returned by the base iterator.
        action - the mapping function to be applied
        context - the processing context. The mapping function is applied to each item returned by context.getCurrentIterator() in turn.
    • Method Detail

      • next

        public Item next()
                  throws XPathException
        Description copied from interface: SequenceIterator
        Get the next item in the sequence. This method changes the state of the iterator.
        Specified by:
        next in interface SequenceIterator
        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.
        XPathException - if an error occurs retrieving the next item
      • close

        public void close()
        Description copied from interface: SequenceIterator
        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 java.lang.AutoCloseable
        Specified by:
        close in interface
        Specified by:
        close in interface SequenceIterator