public class FilterIterator extends java.lang.Object implements SequenceIterator
Modifier and Type | Class and Description |
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static class |
FilterIterator.NonNumeric
Subclass to handle the common special case where it is statically known
that the filter cannot return a numeric value
|
Modifier and Type | Field and Description |
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protected FocusIterator |
base |
protected Expression |
filter |
protected XPathContext |
filterContext |
Constructor and Description |
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FilterIterator(SequenceIterator base,
Expression filter,
XPathContext context)
Constructor
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Modifier and Type | Method and Description |
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void |
close()
Close the iterator.
|
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.
|
protected Item |
getNextMatchingItem()
Get the next item in the base sequence that matches the filter predicate
if there is such an item, or null if not.
|
protected boolean |
matches()
Determine whether the context item matches the filter predicate
|
Item |
next()
Get the next item if there is one
|
void |
setSequence(SequenceIterator base,
XPathContext context)
Set the base iterator
|
static boolean |
testPredicateValue(SequenceIterator iterator,
long position,
Expression filter) |
protected FocusIterator base
protected Expression filter
protected XPathContext filterContext
public FilterIterator(SequenceIterator base, Expression filter, XPathContext context)
base
- An iteration of the items to be filteredfilter
- The expression defining the filter predicatecontext
- The context in which the expression is being evaluatedpublic void setSequence(SequenceIterator base, XPathContext context)
base
- the iterator over the sequence to be filteredcontext
- the context in which the (outer) filter expression is evaluatedpublic Item next()
next
in interface SequenceIterator
protected Item getNextMatchingItem() throws XPathException
XPathException
- if a dynamic error occursprotected boolean matches() throws XPathException
XPathException
- if an error occurs evaluating the matchpublic static boolean testPredicateValue(SequenceIterator iterator, long position, Expression filter) throws XPathException
XPathException
public void close()
SequenceIterator
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.
close
in interface java.io.Closeable
close
in interface java.lang.AutoCloseable
close
in interface SequenceIterator
public void discharge()
SequenceIterator
SequenceIterator.close()
will be called when no more items are needed.discharge
in interface SequenceIterator
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