Package org.eclipse.rdf4j.query.impl

Class QueueCursor<E>

java.lang.Object

org.eclipse.rdf4j.common.iteration.AbstractCloseableIteration<E,X>

org.eclipse.rdf4j.common.iteration.LookAheadIteration<E,T>

org.eclipse.rdf4j.common.iteration.QueueIteration<E,QueryEvaluationException>

org.eclipse.rdf4j.query.impl.QueueCursor<E>

All Implemented Interfaces:

AutoCloseable, CloseableIteration<E,QueryEvaluationException>, Iteration<E,QueryEvaluationException>

Direct Known Subclasses:

FedXQueueCursor

public class QueueCursor<E>
extends QueueIteration<E,QueryEvaluationException>

Makes working with a queue easier by adding the methods QueueIteration.done() and QueueIteration.toss(Exception) and automatically converting the exception into a QueryEvaluationException with an appropriate stack trace.

Author:

James Leigh

Constructor Summary

Constructors

Constructor	Description
QueueCursor(int capacity, boolean fair, WeakReference<?> callerReference)	Creates an QueueCursor with the given (fixed) capacity and the specified access policy.
QueueCursor(int capacity, WeakReference<?> callerReference)	Creates an QueueCursor with the given (fixed) capacity and default access policy.
QueueCursor(BlockingQueue<E> queue, WeakReference<?> callerReference)	Creates an QueueCursor with the given BlockingQueue as its backing queue. It may not be threadsafe to modify or access the given BlockingQueue from other locations.

Method Summary

Modifier and Type	Method	Description
protected QueryEvaluationException	convert(Exception e)	Converts an exception from the underlying iteration to an exception of type X.

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

checkException, done, getNextElement, handleClose, put, toss

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

hasNext, next, remove

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 org.eclipse.rdf4j.common.iteration.CloseableIteration

stream

Constructor Details

QueueCursor

public QueueCursor(int capacity,
 WeakReference<?> callerReference)

Creates an QueueCursor with the given (fixed) capacity and default access policy.

Parameters:

capacity - the capacity of this queue

callerReference - the thing that needs this cursor. Used to detect unexpected code failures and clean up in those case

QueueCursor

public QueueCursor(int capacity,
 boolean fair,
 WeakReference<?> callerReference)

Creates an QueueCursor with the given (fixed) capacity and the specified access policy.

Parameters:

capacity - the capacity of this queue

fair - if true then queue accesses for threads blocked on insertion or removal, are processed in FIFO order; if false the access order is unspecified.

callerReference - the thing that needs this cursor. Used to detect unexpected code failures and clean up in those case

QueueCursor

public QueueCursor(BlockingQueue<E> queue,
 WeakReference<?> callerReference)

Creates an QueueCursor with the given BlockingQueue as its backing queue.
It may not be threadsafe to modify or access the given BlockingQueue from other locations. This method only enables the default ArrayBlockingQueue to be overridden.

Parameters:

queue - A BlockingQueue that is not used in other locations, but will be used as the backing Queue implementation for this cursor.

callerReference - the thing that needs this cursor. Used to detect unexpected code failures and clean up in those case

Method Details

convert

protected QueryEvaluationException convert(Exception e)

Description copied from class: QueueIteration

Converts an exception from the underlying iteration to an exception of type X.

Specified by:

convert in class QueueIteration<E,QueryEvaluationException>