Class DescribeIteration

java.lang.Object

org.eclipse.rdf4j.common.iteration.AbstractCloseableIteration<BindingSet>

org.eclipse.rdf4j.common.iteration.LookAheadIteration<BindingSet>

org.eclipse.rdf4j.query.algebra.evaluation.iterator.DescribeIteration

All Implemented Interfaces:

AutoCloseable, Iterator<BindingSet>, CloseableIteration<BindingSet>

Direct Known Subclasses:

FederatedDescribeIteration

public class DescribeIteration
extends LookAheadIteration<BindingSet>

Iteration that implements a simplified version of Symmetric Concise Bounded Description (omitting reified statements).

Author:

Jeen Broekstra

See Also:

• Concise Bounded Description - alternatives

Field Summary

Fields

Modifier and Type	Field	Description
protected BindingSet	parentBindings
protected static final String	VARNAME_OBJECT
protected static final String	VARNAME_PREDICATE
protected static final String	VARNAME_SUBJECT

Fields inherited from interface CloseableIteration

EMPTY_STATEMENT_ITERATION

Constructor Summary

Constructors

Constructor	Description
DescribeIteration(CloseableIteration<BindingSet> sourceIter, EvaluationStrategy strategy, Set<String> describeExprNames, BindingSet parentBindings)

Method Summary

Modifier and Type	Method	Description
protected CloseableIteration<BindingSet>	createNextIteration(Value subject, Value object)
protected BindingSet	getNextElement()	Gets the next element.
protected void	handleClose()	Called by AbstractCloseableIteration.close() when it is called for the first time.

Methods inherited from class LookAheadIteration

hasNext, next, remove

Methods inherited from class AbstractCloseableIteration

close, isClosed

Methods inherited from class Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Methods inherited from interface CloseableIteration

stream

Methods inherited from interface Iterator

forEachRemaining

Field Details

VARNAME_SUBJECT

protected static final String VARNAME_SUBJECT

See Also:

• Constant Field Values

VARNAME_PREDICATE

protected static final String VARNAME_PREDICATE

See Also:

• Constant Field Values

VARNAME_OBJECT

protected static final String VARNAME_OBJECT

See Also:

• Constant Field Values

parentBindings

protected BindingSet parentBindings

Constructor Details

DescribeIteration

public DescribeIteration(CloseableIteration<BindingSet> sourceIter,
 EvaluationStrategy strategy,
 Set<String> describeExprNames,
 BindingSet parentBindings)

Method Details

getNextElement

protected BindingSet getNextElement()
                             throws QueryEvaluationException

Description copied from class: LookAheadIteration

Gets the next element. Subclasses should implement this method so that it returns the next element.

Specified by:

getNextElement in class LookAheadIteration<BindingSet>

Returns:

The next element, or null if no more elements are available.

Throws:

QueryEvaluationException

createNextIteration

protected CloseableIteration<BindingSet> createNextIteration(Value subject,
 Value object)
                                                      throws QueryEvaluationException

Throws:

QueryEvaluationException

handleClose

protected void handleClose()
                    throws QueryEvaluationException

Description copied from class: AbstractCloseableIteration

Called by AbstractCloseableIteration.close() when it is called for the first time. This method is only called once on each iteration. By default, this method does nothing.

Specified by:

handleClose in class AbstractCloseableIteration<BindingSet>

Throws:

QueryEvaluationException