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RDF Storage And Inference Layer ("Sail") API.
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/*******************************************************************************
* Copyright (c) 2015 Eclipse RDF4J contributors, Aduna, and others.
*
* All rights reserved. This program and the accompanying materials
* are made available under the terms of the Eclipse Distribution License v1.0
* which accompanies this distribution, and is available at
* http://www.eclipse.org/org/documents/edl-v10.php.
*
* SPDX-License-Identifier: BSD-3-Clause
*******************************************************************************/
package org.eclipse.rdf4j.sail.helpers;
import java.lang.invoke.MethodHandles;
import java.lang.invoke.VarHandle;
import java.time.Duration;
import java.util.Collection;
import java.util.Collections;
import java.util.IdentityHashMap;
import java.util.LinkedList;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.atomic.AtomicReference;
import java.util.concurrent.atomic.LongAdder;
import java.util.concurrent.locks.LockSupport;
import java.util.concurrent.locks.ReentrantLock;
import org.eclipse.rdf4j.common.annotation.InternalUseOnly;
import org.eclipse.rdf4j.common.concurrent.locks.Lock;
import org.eclipse.rdf4j.common.concurrent.locks.diagnostics.ConcurrentCleaner;
import org.eclipse.rdf4j.common.iteration.CloseableIteration;
import org.eclipse.rdf4j.common.iteration.EmptyIteration;
import org.eclipse.rdf4j.common.order.StatementOrder;
import org.eclipse.rdf4j.common.transaction.IsolationLevel;
import org.eclipse.rdf4j.common.transaction.IsolationLevels;
import org.eclipse.rdf4j.model.BNode;
import org.eclipse.rdf4j.model.IRI;
import org.eclipse.rdf4j.model.Namespace;
import org.eclipse.rdf4j.model.Resource;
import org.eclipse.rdf4j.model.Statement;
import org.eclipse.rdf4j.model.Value;
import org.eclipse.rdf4j.model.impl.SimpleValueFactory;
import org.eclipse.rdf4j.query.BindingSet;
import org.eclipse.rdf4j.query.Dataset;
import org.eclipse.rdf4j.query.algebra.TupleExpr;
import org.eclipse.rdf4j.sail.SailConnection;
import org.eclipse.rdf4j.sail.SailException;
import org.eclipse.rdf4j.sail.UnknownSailTransactionStateException;
import org.eclipse.rdf4j.sail.UpdateContext;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
/**
* Abstract Class offering base functionality for SailConnection implementations.
*
* @author Arjohn Kampman
* @author Jeen Broekstra
*/
public abstract class AbstractSailConnection implements SailConnection {
private static boolean assertsEnabled = false;
static {
// noinspection AssertWithSideEffects
assert assertsEnabled = true;
}
private static final ConcurrentCleaner cleaner = new ConcurrentCleaner();
/**
* Size of write queue before auto flushing changes within write operation
*/
private static final int BLOCK_SIZE = 1000;
private static final Logger logger = LoggerFactory.getLogger(AbstractSailConnection.class);
/*-----------*
* Variables *
*-----------*/
// System.getProperty maybe too expensive to call every time
private final boolean debugEnabled = AbstractSail.debugEnabled();
private final AbstractSail sailBase;
private volatile boolean txnActive;
private volatile boolean txnPrepared;
/**
* Lock used to give the {@link #close()} method exclusive access to a connection.
*
* - write lock: close()
*
- read lock: all other (public) methods
*
*/
private final LongAdder blockClose = new LongAdder();
private final LongAdder unblockClose = new LongAdder();
private final AtomicReference activeThread = new AtomicReference<>();
@SuppressWarnings("FieldMayBeFinal")
private boolean isOpen = true;
private static final VarHandle IS_OPEN;
private Thread owner;
/**
* Lock used to prevent concurrent calls to update methods like addStatement, clear, commit, etc. within a
* transaction.
*
*/
private final ReentrantLock updateLock = new ReentrantLock();
private final LongAdder iterationsOpened = new LongAdder();
private final LongAdder iterationsClosed = new LongAdder();
private final Map, Throwable> activeIterationsDebug;
/**
* Statements that are currently being removed, but not yet realized, by an active operation.
*/
private final Map> removed = new IdentityHashMap<>(0);
/**
* Statements that are currently being added, but not yet realized, by an active operation.
*/
private final Map> added = new IdentityHashMap<>(0);
/**
* Used to indicate a removed statement from all contexts.
*/
private static final BNode wildContext = SimpleValueFactory.getInstance().createBNode();
private IsolationLevel transactionIsolationLevel;
// used to decide if we need to call flush()
private volatile boolean statementsAdded;
private volatile boolean statementsRemoved;
/*--------------*
* Constructors *
*--------------*/
public AbstractSailConnection(AbstractSail sailBase) {
this.sailBase = sailBase;
txnActive = false;
if (debugEnabled) {
activeIterationsDebug = new ConcurrentHashMap<>();
} else {
activeIterationsDebug = Collections.emptyMap();
}
owner = Thread.currentThread();
}
/*---------*
* Methods *
*---------*/
@Override
public final boolean isOpen() throws SailException {
return ((boolean) IS_OPEN.getAcquire(this));
}
protected void verifyIsOpen() throws SailException {
if (!((boolean) IS_OPEN.getAcquire(this))) {
throw new IllegalStateException("Connection has been closed");
}
}
/**
* Verifies if a transaction is currently active. Throws a {@link SailException} if no transaction is active.
*
* @throws SailException if no transaction is active.
*/
protected void verifyIsActive() throws SailException {
if (!isActive()) {
throw new SailException("No active transaction");
}
}
@Override
public void begin() throws SailException {
begin(sailBase.getDefaultIsolationLevel());
}
@Override
public void begin(IsolationLevel isolationLevel) throws SailException {
if (isolationLevel == null) {
isolationLevel = sailBase.getDefaultIsolationLevel();
}
IsolationLevel compatibleLevel = IsolationLevels.getCompatibleIsolationLevel(isolationLevel,
sailBase.getSupportedIsolationLevels());
if (compatibleLevel == null) {
throw new UnknownSailTransactionStateException(
"Isolation level " + isolationLevel + " not compatible with this Sail");
}
this.transactionIsolationLevel = compatibleLevel;
blockClose.increment();
try {
activeThread.setRelease(Thread.currentThread());
verifyIsOpen();
updateLock.lock();
try {
if (isActive()) {
throw new SailException("a transaction is already active on this connection.");
}
startTransactionInternal();
txnActive = true;
} finally {
updateLock.unlock();
}
} finally {
try {
activeThread.setRelease(null);
} finally {
unblockClose.increment();
}
}
startUpdate(null);
}
/**
* Retrieve the currently set {@link IsolationLevel}.
*
* @return the current {@link IsolationLevel}. If no transaction is active, this may be null.
*/
protected IsolationLevel getTransactionIsolation() {
return this.transactionIsolationLevel;
}
@Override
public boolean isActive() throws UnknownSailTransactionStateException {
return transactionActive();
}
@Override
public final void close() throws SailException {
// obtain an exclusive lock so that any further operations on this
// connection (including those from any concurrent threads) are blocked.
if (!IS_OPEN.compareAndSet(this, true, false)) {
return;
}
try {
waitForOtherOperations(true);
try {
try {
forceCloseActiveOperations();
} finally {
if (txnActive) {
logger.warn("Rolling back transaction due to connection close",
debugEnabled ? new Throwable() : null);
try {
// Use internal method to avoid deadlock: the public
// rollback method will try to obtain a connection lock
rollbackInternal();
} finally {
txnActive = false;
txnPrepared = false;
}
}
closeInternal();
if (isActiveOperation()) {
throw new SailException("Connection closed before all iterations were closed.");
}
}
} finally {
sailBase.connectionClosed(this);
}
} finally {
}
}
@InternalUseOnly
public void waitForOtherOperations(boolean interrupt) {
int i = 0;
boolean interrupted = false;
while (true) {
long sumDone = unblockClose.sum();
long sumBlocking = blockClose.sum();
if (sumDone == sumBlocking) {
if (interrupted) {
logger.warn(
"Connection is no longer blocked by concurrent operation after interrupting the active thread");
}
break;
} else {
if (Thread.currentThread().isInterrupted()) {
throw new SailException(
"Connection was interrupted while waiting on concurrent operations before it could be closed.");
} else {
LockSupport.parkNanos(Duration.ofMillis(10).toNanos());
if (++i % 500 == 0) { // wait for 5 seconds before logging and interrupting
Thread acquire = activeThread.getAcquire();
if (acquire != null) {
logger.warn("Connection is blocked by concurrent operation in thread: {}", acquire);
if (interrupt) {
acquire.interrupt();
interrupted = true;
logger.error(
"Connection is blocked by concurrent operation in thread {} which was interrupted to attempt to forcefully abort the concurrent operation.",
acquire);
}
}
}
}
}
}
}
@Override
public final CloseableIteration evaluate(TupleExpr tupleExpr,
Dataset dataset, BindingSet bindings, boolean includeInferred) throws SailException {
flushPendingUpdates();
blockClose.increment();
try {
activeThread.setRelease(Thread.currentThread());
verifyIsOpen();
CloseableIteration iteration = null;
try {
iteration = evaluateInternal(tupleExpr, dataset, bindings, includeInferred);
if (assertsEnabled) {
iteration = new TupleExprWrapperIteration<>(iteration, tupleExpr);
}
return registerIteration(iteration);
} catch (Throwable t) {
if (iteration != null) {
iteration.close();
}
throw t;
}
} finally {
try {
activeThread.setRelease(null);
} finally {
unblockClose.increment();
}
}
}
@Override
public final CloseableIteration getContextIDs() throws SailException {
flushPendingUpdates();
blockClose.increment();
try {
activeThread.setRelease(Thread.currentThread());
verifyIsOpen();
return registerIteration(getContextIDsInternal());
} finally {
try {
activeThread.setRelease(null);
} finally {
unblockClose.increment();
}
}
}
@Override
public final CloseableIteration getStatements(Resource subj, IRI pred,
Value obj, boolean includeInferred, Resource... contexts) throws SailException {
flushPendingUpdates();
blockClose.increment();
try {
activeThread.setRelease(Thread.currentThread());
verifyIsOpen();
CloseableIteration iteration = null;
try {
iteration = getStatementsInternal(subj, pred, obj, includeInferred, contexts);
return registerIteration(iteration);
} catch (Throwable t) {
if (iteration != null) {
iteration.close();
}
throw t;
}
} finally {
try {
activeThread.setRelease(null);
} finally {
unblockClose.increment();
}
}
}
@Override
public final CloseableIteration getStatements(StatementOrder order, Resource subj, IRI pred,
Value obj, boolean includeInferred, Resource... contexts) throws SailException {
flushPendingUpdates();
blockClose.increment();
try {
verifyIsOpen();
CloseableIteration iteration = null;
try {
iteration = getStatementsInternal(order, subj, pred, obj, includeInferred, contexts);
return registerIteration(iteration);
} catch (Throwable t) {
if (iteration != null) {
iteration.close();
}
throw t;
}
} finally {
unblockClose.increment();
}
}
@Override
public final boolean hasStatement(Resource subj, IRI pred, Value obj, boolean includeInferred, Resource... contexts)
throws SailException {
flushPendingUpdates();
blockClose.increment();
try {
activeThread.setRelease(Thread.currentThread());
verifyIsOpen();
return hasStatementInternal(subj, pred, obj, includeInferred, contexts);
} finally {
try {
activeThread.setRelease(null);
} finally {
unblockClose.increment();
}
}
}
protected boolean hasStatementInternal(Resource subj, IRI pred, Value obj, boolean includeInferred,
Resource[] contexts) {
try (var iteration = getStatementsInternal(subj, pred, obj, includeInferred, contexts)) {
return iteration.hasNext();
}
}
@Override
public final long size(Resource... contexts) throws SailException {
flushPendingUpdates();
blockClose.increment();
try {
activeThread.setRelease(Thread.currentThread());
verifyIsOpen();
return sizeInternal(contexts);
} finally {
try {
activeThread.setRelease(null);
} finally {
unblockClose.increment();
}
}
}
protected final boolean transactionActive() {
return txnActive;
}
/**
* IMPORTANT Since Sesame 2.7.0. this method no longer automatically starts a transaction, but instead
* verifies if a transaction is active and if not throws an exception. The method is left in for transitional
* purposes only. Sail implementors are advised that by contract, any update operation on the Sail should check if a
* transaction has been started via {@link SailConnection#isActive} and throw a SailException if not. Implementors
* can use {@link AbstractSailConnection#verifyIsActive()} as a convenience method for this check.
*
* @throws SailException if no transaction is active.
* @deprecated Use {@link #verifyIsActive()} instead. We should not automatically start a transaction at the sail
* level. Instead, an exception should be thrown when an update is executed without first starting a
* transaction.
*/
@Deprecated(since = "2.7.0")
protected void autoStartTransaction() throws SailException {
verifyIsActive();
}
@Override
public void flush() throws SailException {
if (isActive()) {
endUpdate(null);
startUpdate(null);
}
}
@Override
public final void prepare() throws SailException {
if (isActive()) {
endUpdate(null);
}
blockClose.increment();
try {
activeThread.setRelease(Thread.currentThread());
verifyIsOpen();
updateLock.lock();
try {
if (txnActive) {
prepareInternal();
txnPrepared = true;
}
} finally {
updateLock.unlock();
}
} finally {
try {
activeThread.setRelease(null);
} finally {
unblockClose.increment();
}
}
}
@Override
public final void commit() throws SailException {
if (isActive()) {
endUpdate(null);
}
blockClose.increment();
try {
activeThread.setRelease(Thread.currentThread());
verifyIsOpen();
updateLock.lock();
try {
if (txnActive) {
if (!txnPrepared) {
prepareInternal();
}
commitInternal();
txnActive = false;
txnPrepared = false;
}
} finally {
updateLock.unlock();
}
} finally {
try {
activeThread.setRelease(null);
} finally {
unblockClose.increment();
}
}
}
@Override
public final void rollback() throws SailException {
synchronized (added) {
added.clear();
}
synchronized (removed) {
removed.clear();
}
blockClose.increment();
try {
activeThread.setRelease(Thread.currentThread());
verifyIsOpen();
updateLock.lock();
try {
if (txnActive) {
try {
rollbackInternal();
} finally {
txnActive = false;
txnPrepared = false;
}
} else {
logger.warn("Cannot rollback transaction on connection because transaction is not active",
debugEnabled ? new Throwable() : null);
}
} finally {
updateLock.unlock();
}
} finally {
try {
activeThread.setRelease(null);
} finally {
unblockClose.increment();
}
}
}
@Override
public final void addStatement(Resource subj, IRI pred, Value obj, Resource... contexts) throws SailException {
if (statementsRemoved) {
flushPendingUpdates();
}
addStatement(null, subj, pred, obj, contexts);
statementsAdded = true;
}
@Override
public final void removeStatements(Resource subj, IRI pred, Value obj, Resource... contexts) throws SailException {
if (pendingAdds()) {
flushPendingUpdates();
}
removeStatement(null, subj, pred, obj, contexts);
statementsRemoved = true;
}
@Override
public void startUpdate(UpdateContext op) throws SailException {
if (op != null) {
flushPendingUpdates();
}
synchronized (removed) {
assert !removed.containsKey(op);
removed.put(op, new LinkedList<>());
}
synchronized (added) {
assert !added.containsKey(op);
added.put(op, new LinkedList<>());
}
}
/**
* The default implementation buffers added statements until the update operation is complete.
*/
@Override
public void addStatement(UpdateContext op, Resource subj, IRI pred, Value obj, Resource... contexts)
throws SailException {
verifyIsOpen();
verifyIsActive();
synchronized (added) {
assert added.containsKey(op);
Collection pending = added.get(op);
if (contexts == null || contexts.length == 0) {
pending.add(sailBase.getValueFactory().createStatement(subj, pred, obj));
} else {
for (Resource ctx : contexts) {
pending.add(sailBase.getValueFactory().createStatement(subj, pred, obj, ctx));
}
}
if (pending.size() % BLOCK_SIZE == 0 && !isActiveOperation()) {
endUpdate(op);
startUpdate(op);
}
}
statementsAdded = true;
}
/**
* The default implementation buffers removed statements until the update operation is complete.
*/
@Override
public void removeStatement(UpdateContext op, Resource subj, IRI pred, Value obj, Resource... contexts)
throws SailException {
verifyIsOpen();
verifyIsActive();
synchronized (removed) {
assert removed.containsKey(op);
Collection pending = removed.get(op);
if (contexts == null) {
pending.add(new WildStatement(subj, pred, obj));
} else if (contexts.length == 0) {
pending.add(new WildStatement(subj, pred, obj, wildContext));
} else {
for (Resource ctx : contexts) {
pending.add(new WildStatement(subj, pred, obj, ctx));
}
}
if (pending.size() % BLOCK_SIZE == 0 && !isActiveOperation()) {
endUpdate(op);
startUpdate(op);
}
}
statementsRemoved = true;
}
@Override
public final void endUpdate(UpdateContext op) throws SailException {
blockClose.increment();
try {
activeThread.setRelease(Thread.currentThread());
verifyIsOpen();
updateLock.lock();
try {
verifyIsActive();
endUpdateInternal(op);
} finally {
updateLock.unlock();
}
} finally {
try {
activeThread.setRelease(null);
} finally {
unblockClose.increment();
}
if (op != null) {
flush();
}
}
}
protected void endUpdateInternal(UpdateContext op) throws SailException {
Collection model;
// realize DELETE
synchronized (removed) {
model = removed.remove(op);
}
if (model != null) {
for (Statement st : model) {
Resource ctx = st.getContext();
if (wildContext.equals(ctx)) {
removeStatementsInternal(st.getSubject(), st.getPredicate(), st.getObject());
} else {
removeStatementsInternal(st.getSubject(), st.getPredicate(), st.getObject(), ctx);
}
}
}
// realize INSERT
synchronized (added) {
model = added.remove(op);
}
if (model != null) {
for (Statement st : model) {
addStatementInternal(st.getSubject(), st.getPredicate(), st.getObject(), st.getContext());
}
}
}
@Override
public final void clear(Resource... contexts) throws SailException {
flushPendingUpdates();
blockClose.increment();
try {
activeThread.setRelease(Thread.currentThread());
verifyIsOpen();
updateLock.lock();
try {
verifyIsActive();
clearInternal(contexts);
statementsRemoved = true;
} finally {
updateLock.unlock();
}
} finally {
try {
activeThread.setRelease(null);
} finally {
unblockClose.increment();
}
}
}
@Override
public final CloseableIteration getNamespaces() throws SailException {
blockClose.increment();
try {
activeThread.setRelease(Thread.currentThread());
verifyIsOpen();
return registerIteration(getNamespacesInternal());
} finally {
try {
activeThread.setRelease(null);
} finally {
unblockClose.increment();
}
}
}
@Override
public final String getNamespace(String prefix) throws SailException {
if (prefix == null) {
throw new NullPointerException("prefix must not be null");
}
blockClose.increment();
try {
activeThread.setRelease(Thread.currentThread());
verifyIsOpen();
return getNamespaceInternal(prefix);
} finally {
try {
activeThread.setRelease(null);
} finally {
unblockClose.increment();
}
}
}
@Override
public final void setNamespace(String prefix, String name) throws SailException {
if (prefix == null) {
throw new NullPointerException("prefix must not be null");
}
if (name == null) {
throw new NullPointerException("name must not be null");
}
blockClose.increment();
try {
activeThread.setRelease(Thread.currentThread());
verifyIsOpen();
updateLock.lock();
try {
verifyIsActive();
setNamespaceInternal(prefix, name);
} finally {
updateLock.unlock();
}
} finally {
try {
activeThread.setRelease(null);
} finally {
unblockClose.increment();
}
}
}
@Override
public final void removeNamespace(String prefix) throws SailException {
if (prefix == null) {
throw new NullPointerException("prefix must not be null");
}
blockClose.increment();
try {
activeThread.setRelease(Thread.currentThread());
verifyIsOpen();
updateLock.lock();
try {
verifyIsActive();
removeNamespaceInternal(prefix);
} finally {
updateLock.unlock();
}
} finally {
try {
activeThread.setRelease(null);
} finally {
unblockClose.increment();
}
}
}
@Override
public final void clearNamespaces() throws SailException {
blockClose.increment();
try {
activeThread.setRelease(Thread.currentThread());
verifyIsOpen();
updateLock.lock();
try {
verifyIsActive();
clearNamespacesInternal();
} finally {
updateLock.unlock();
}
} finally {
try {
activeThread.setRelease(null);
} finally {
unblockClose.increment();
}
}
}
protected boolean pendingAdds() {
return statementsAdded;
}
protected void setStatementsAdded() {
statementsAdded = true;
}
protected void setStatementsRemoved() {
statementsRemoved = true;
}
/**
* This is for internal use only. It returns the thread that opened this connection.
*
* @return the thread that opened this connection.
*/
@InternalUseOnly
public Thread getOwner() {
return owner;
}
/**
* Registers an iteration as active by wrapping it in a {@link SailBaseIteration} object and adding it to the list
* of active iterations.
*/
protected CloseableIteration registerIteration(CloseableIteration iter) {
if (iter instanceof EmptyIteration) {
return iter;
}
iterationsOpened.increment();
if (debugEnabled) {
var result = new SailBaseIteration<>(iter, this);
activeIterationsDebug.put(result, new Throwable("Unclosed iteration"));
return result;
} else {
return new CleanerIteration<>(new SailBaseIteration<>(iter, this), cleaner);
}
}
/**
* Called by {@link SailBaseIteration} to indicate that it has been closed.
*/
protected void iterationClosed(SailBaseIteration iter) {
if (debugEnabled) {
activeIterationsDebug.remove(iter);
}
iterationsClosed.increment();
}
protected abstract void closeInternal() throws SailException;
protected abstract CloseableIteration evaluateInternal(
TupleExpr tupleExpr, Dataset dataset, BindingSet bindings, boolean includeInferred) throws SailException;
protected abstract CloseableIteration getContextIDsInternal()
throws SailException;
protected abstract CloseableIteration getStatementsInternal(Resource subj,
IRI pred, Value obj, boolean includeInferred, Resource... contexts) throws SailException;
protected CloseableIteration getStatementsInternal(StatementOrder order, Resource subj,
IRI pred, Value obj, boolean includeInferred, Resource... contexts) throws SailException {
throw new SailException("StatementOrder not supported");
}
protected abstract long sizeInternal(Resource... contexts) throws SailException;
protected abstract void startTransactionInternal() throws SailException;
protected void prepareInternal() throws SailException {
// do nothing
}
protected abstract void commitInternal() throws SailException;
protected abstract void rollbackInternal() throws SailException;
protected abstract void addStatementInternal(Resource subj, IRI pred, Value obj, Resource... contexts)
throws SailException;
protected abstract void removeStatementsInternal(Resource subj, IRI pred, Value obj, Resource... contexts)
throws SailException;
protected abstract void clearInternal(Resource... contexts) throws SailException;
protected abstract CloseableIteration getNamespacesInternal()
throws SailException;
protected abstract String getNamespaceInternal(String prefix) throws SailException;
protected abstract void setNamespaceInternal(String prefix, String name) throws SailException;
protected abstract void removeNamespaceInternal(String prefix) throws SailException;
protected abstract void clearNamespacesInternal() throws SailException;
protected boolean isActiveOperation() {
long closed = iterationsClosed.sum();
long opened = iterationsOpened.sum();
return closed != opened;
}
protected AbstractSail getSailBase() {
return sailBase;
}
private void forceCloseActiveOperations() throws SailException {
for (int i = 0; i < 10 && isActiveOperation() && !debugEnabled; i++) {
System.gc();
try {
Thread.sleep(1);
} catch (InterruptedException e) {
Thread.currentThread().interrupt();
throw new SailException(e);
}
}
if (debugEnabled) {
var activeIterationsCopy = new IdentityHashMap<>(activeIterationsDebug);
activeIterationsDebug.clear();
if (!activeIterationsCopy.isEmpty()) {
for (var entry : activeIterationsCopy.entrySet()) {
try {
logger.warn("Unclosed iteration", entry.getValue());
entry.getKey().close();
} catch (Exception e) {
if (e instanceof InterruptedException) {
Thread.currentThread().interrupt();
throw new SailException(e);
}
logger.warn("Exception occurred while closing unclosed iterations.", e);
}
}
var entry = activeIterationsCopy.entrySet().stream().findAny().orElseThrow();
throw new SailException(
"Connection closed before all iterations were closed: " + entry.getKey().toString(),
entry.getValue());
}
}
}
/**
* If there are no open operations.
*
* @throws SailException
*/
private void flushPendingUpdates() throws SailException {
if ((statementsAdded || statementsRemoved) && isActive()) {
if (isActive()) {
synchronized (this) {
if ((statementsAdded || statementsRemoved) && isActive()) {
flush();
statementsAdded = false;
statementsRemoved = false;
}
}
}
}
}
/**
* Statement pattern that uses null values as wild cards.
*
* @author James Leigh
*/
private static class WildStatement implements Statement {
private static final long serialVersionUID = 3363010521961228565L;
/**
* The statement's subject.
*/
private final Resource subject;
/**
* The statement's predicate.
*/
private final IRI predicate;
/**
* The statement's object.
*/
private final Value object;
/**
* The statement's context, if applicable.
*/
private final Resource context;
/*--------------*
* Constructors *
*--------------*/
/**
* Creates a new Statement with the supplied subject, predicate and object.
*
* @param subject The statement's subject, may be null.
* @param predicate The statement's predicate, may be null.
* @param object The statement's object, may be null.
*/
public WildStatement(Resource subject, IRI predicate, Value object) {
this(subject, predicate, object, null);
}
/**
* Creates a new Statement with the supplied subject, predicate and object for the specified associated context.
*
* @param subject The statement's subject, may be null.
* @param predicate The statement's predicate, may be null.
* @param object The statement's object, may be null.
* @param context The statement's context, null to indicate no context is associated.
*/
public WildStatement(Resource subject, IRI predicate, Value object, Resource context) {
this.subject = subject;
this.predicate = predicate;
this.object = object;
this.context = context;
}
/*---------*
* Methods *
*---------*/
// Implements Statement.getSubject()
@Override
public Resource getSubject() {
return subject;
}
// Implements Statement.getPredicate()
@Override
public IRI getPredicate() {
return predicate;
}
// Implements Statement.getObject()
@Override
public Value getObject() {
return object;
}
@Override
public Resource getContext() {
return context;
}
@Override
public String toString() {
return "(" +
getSubject() +
", " +
getPredicate() +
", " +
getObject() +
")" +
" [" + getContext() + "]";
}
}
private static class JavaLock implements Lock {
private final java.util.concurrent.locks.Lock javaLock;
private boolean isActive = true;
public JavaLock(java.util.concurrent.locks.Lock javaLock) {
this.javaLock = javaLock;
javaLock.lock();
}
@Override
public synchronized boolean isActive() {
return isActive;
}
@Override
public synchronized void release() {
if (isActive) {
javaLock.unlock();
isActive = false;
}
}
}
static {
try {
IS_OPEN = MethodHandles.lookup()
.in(AbstractSailConnection.class)
.findVarHandle(AbstractSailConnection.class, "isOpen", boolean.class);
} catch (ReflectiveOperationException e) {
throw new Error(e);
}
}
}
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