Package org.eclipse.rdf4j.repository

Class RepositoryResult<T>

java.lang.Object

org.eclipse.rdf4j.common.iteration.AbstractCloseableIteration<T,RepositoryException>

org.eclipse.rdf4j.repository.RepositoryResult<T>

All Implemented Interfaces:

AutoCloseable, Iterable<T>, CloseableIteration<T,RepositoryException>, Iteration<T,RepositoryException>

public class RepositoryResult<T>
extends AbstractCloseableIteration<T,RepositoryException>
implements Iterable<T>

A RepositoryResult is a result collection of objects (for example Statement , Namespace, or Resource objects) that can be iterated over. It keeps an open connection to the backend for lazy retrieval of individual results. Additionally it has some utility methods to fetch all results and add them to a collection.

By default, a RepositoryResult is not necessarily a (mathematical) set: it may contain duplicate objects. Duplicate filtering can be switched on, but this should not be used lightly as the filtering mechanism is potentially memory-intensive.

A RepositoryResult needs to be closed after use to free up any resources (open connections, read locks, etc.) it has on the underlying repository.

Author:

Jeen Broekstra, Arjohn Kampman

See Also:

• RepositoryConnection.getStatements(org.eclipse.rdf4j.model.Resource, org.eclipse.rdf4j.model.URI, org.eclipse.rdf4j.model.Value, boolean, org.eclipse.rdf4j.model.Resource[])
• RepositoryConnection.getNamespaces()
• RepositoryConnection.getContextIDs()

Constructor Summary

Constructors

Constructor	Description
RepositoryResult(CloseableIteration<? extends T,RepositoryException> iter)

Method Summary

Modifier and Type	Method	Description
<C extends Collection<T>> C	addTo(C collection)	Deprecated. Use Iterations.addAll(Iteration, Collection) instead.
List<T>	asList()	Deprecated. Use Iterations.asList(Iteration) instead.
void	enableDuplicateFilter()	Switches on duplicate filtering while iterating over objects.
protected void	handleClose()	Called by AbstractCloseableIteration.close() when it is called for the first time.
boolean	hasNext()	Returns true if the iteration has more elements.
Iterator<T>	iterator()
T	next()	Returns the next element in the iteration.
void	remove()	Removes from the underlying collection the last element returned by the iteration (optional operation).

Methods inherited from class org.eclipse.rdf4j.common.iteration.AbstractCloseableIteration

close, isClosed

Methods inherited from class java.lang.Object

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

Methods inherited from interface java.lang.Iterable

forEach, spliterator

Methods inherited from interface org.eclipse.rdf4j.common.iteration.Iteration

stream

Constructor Details

RepositoryResult

public RepositoryResult(CloseableIteration<? extends T,RepositoryException> iter)

Method Details

hasNext

public boolean hasNext()
                throws RepositoryException

Description copied from interface: Iteration

Returns true if the iteration has more elements. (In other words, returns true if Iteration.next() would return an element rather than throwing a NoSuchElementException.)

Specified by:

hasNext in interface Iteration<T,RepositoryException>

Returns:

true if the iteration has more elements.

Throws:

RepositoryException

next

public T next()
       throws RepositoryException

Description copied from interface: Iteration

Returns the next element in the iteration.

Specified by:

next in interface Iteration<T,RepositoryException>

Returns:

the next element in the iteration.

Throws:

RepositoryException

remove

public void remove()
            throws RepositoryException

Description copied from interface: Iteration

Removes from the underlying collection the last element returned by the iteration (optional operation). This method can be called only once per call to next.

Specified by:

remove in interface Iteration<T,RepositoryException>

Throws:

RepositoryException

handleClose

protected void handleClose()
                    throws RepositoryException

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.

Overrides:

handleClose in class AbstractCloseableIteration<T,RepositoryException>

Throws:

RepositoryException

enableDuplicateFilter

public void enableDuplicateFilter()
                           throws RepositoryException

Switches on duplicate filtering while iterating over objects. The RepositoryResult will keep track of the previously returned objects in a Set and on calling next() or hasNext() will ignore any objects that already occur in this Set.

Caution: use of this filtering mechanism is potentially memory-intensive.

Throws:

RepositoryException - if a problem occurred during initialization of the filter.

asList

@Deprecated
public List<T> asList()
               throws RepositoryException

Deprecated.

Use Iterations.asList(Iteration) instead.

Returns a List containing all objects of this RepositoryResult in order of iteration. The RepositoryResult is fully consumed and automatically closed by this operation.

Note: use this method with caution! It pulls the entire RepositoryResult in memory and as such is potentially very memory-intensive.

Returns:

a List containing all objects of this RepositoryResult.

Throws:

RepositoryException - if a problem occurred during retrieval of the results.

See Also:

• addTo(Collection)

addTo

@Deprecated
public <C extends Collection<T>> C addTo(C collection)
                                  throws RepositoryException

Deprecated.

Use Iterations.addAll(Iteration, Collection) instead.

Adds all objects of this RepositoryResult to the supplied collection. The RepositoryResult is fully consumed and automatically closed by this operation.

Returns:

A reference to the collection that was supplied.

Throws:

RepositoryException - if a problem occurred during retrieval of the results.

iterator

public Iterator<T> iterator()

Specified by:

iterator in interface Iterable<T>