- All Implemented Interfaces:
public abstract class OneToOneMappingIterator extends java.lang.Object implements SequenceIterator, LookaheadIterator, LastPositionFinderAbstract iterator that performs a one-to-one mapping from the items in the input sequence to the items in the output sequence; the mapping operation is defined by the map() action implemented in the subclass.
Constructors Constructor Description
All Methods Instance Methods Abstract Methods Concrete Methods Modifier and Type Method Description
close()Close the iterator.
discharge()Calling this method instructs the iterator to release any resources it holds, while still remaining able to deliver the remaining items in the sequence.
getLength()Get the last position (that is, the number of items in the sequence).
hasNext()Determine whether there are more items to come.
protected abstract Item
map(Item baseItem)Abstract method to be supplied in subclasses to map an item from the input sequence to an item in the output sequence
next()Get the next item in the sequence.
setSequence(SequenceIterator base, XPathContext context)
supportsGetLength()Ask whether this iterator supports use of the
supportsHasNext()Ask whether the hasNext() method can be called.
protected XPathContext context
public boolean supportsHasNext()Description copied from interface:
LookaheadIteratorAsk whether the hasNext() method can be called. This method must be called before calling hasNext(), because some iterators implement this interface, but only support look-ahead under particular circumstances (this is usually because they delegate to another iterator)
public boolean hasNext()Description copied from interface:
LookaheadIteratorDetermine whether there are more items to come. Note that this operation is stateless and it is not necessary (or usual) to call it before calling next(). It is used only when there is an explicit need to tell if we are at the last element.
This method must not be called unless the result of
public Item next()Get the next item in the sequence. This method changes the state of the iterator.
- Specified by:
- 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.
protected abstract Item map(Item baseItem) throws XPathExceptionAbstract method to be supplied in subclasses to map an item from the input sequence to an item in the output sequence
baseItem- the item in the input (base) sequence
- the corresponding item in the output sequence. Must not be null
XPathException- if the mapping function fails
public 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.
Closing an iterator is not necessary if the iterator is read to completion: if a call on
SequenceIterator.next()returns null, the iterator will be closed automatically. An explicit call on
SequenceIterator.close()is needed only when iteration is abandoned prematurely.
public void discharge()Calling this method instructs the iterator to release any resources it holds, while still remaining able to deliver the remaining items in the sequence. This may require the iterator to calculate the rest of the sequence eagerly. The method is called by a client if it anticipates that it might not read the iterator to completion, but it cannot guarantee that
SequenceIterator.close()will be called when no more items are needed.
public boolean supportsGetLength()Description copied from interface:
LastPositionFinderAsk whether this iterator supports use of the
LastPositionFinder.getLength()method. This method should always be called before calling
LastPositionFinder.getLength(), because an iterator that implements this interface may support use of
LastPositionFinder.getLength()in some situations and not in others
public int getLength()Description copied from interface:
LastPositionFinderGet the last position (that is, the number of items in the sequence). This method is non-destructive: it does not change the state of the iterator. The result is undefined if the next() method of the iterator has already returned null. This method must not be called unless the
LastPositionFinder.supportsGetLength()has been called and has returned true.