Package net.sf.saxon.expr

Class CardinalityCheckingIterator<T extends Item<?>>

java.lang.Object
net.sf.saxon.expr.CardinalityCheckingIterator<T>
All Implemented Interfaces:
Closeable, AutoCloseable, SequenceIterator<T>
public final class CardinalityCheckingIterator<T extends Item<?>> extends Object implements SequenceIterator<T>
CardinalityCheckingIterator returns the items in an underlying sequence unchanged, but checks that the number of items conforms to the required cardinality. Because cardinality checks are required to take place even if the consumer of the sequence does not require all the items, we read the first two items at initialization time. This is sufficient to perform the checks; after that we can simply return the items from the base sequence.

  • Constructor Details

    • CardinalityCheckingIterator

      public CardinalityCheckingIterator(SequenceIterator<T> base, int requiredCardinality, RoleDiagnostic role, Location locator) throws XPathException
      Construct an CardinalityCheckingIterator that will return the same items as the base sequence, checking how many there are
      Parameters:
      base - the base iterator
      requiredCardinality - the required Cardinality
      Throws:
      XPathException

  • Method Details

    • next

      public T 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<T extends Item<?>>
      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

    • 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 AutoCloseable
      Specified by:
      close in interface Closeable
      Specified by:
      close in interface SequenceIterator<T extends Item<?>>

    • getProperties

      public int getProperties()
      Get properties of this iterator, as a bit-significant integer.
      Specified by:
      getProperties in interface SequenceIterator<T extends Item<?>>
      Returns:
      the properties of this iterator. This will be some combination of properties such as SequenceIterator.GROUNDED, SequenceIterator.LAST_POSITION_FINDER, and SequenceIterator.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.