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Apache Jena Fuseki server Kafka connector
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.kafka.common.internals;
import java.util.concurrent.atomic.AtomicBoolean;
import java.util.function.Supplier;
/**
* {@code IdempotentCloser} encapsulates some basic logic to ensure that a given resource is only closed once.
* The underlying mechanism for ensuring that the close only happens once and is thread safe
* is via the {@link AtomicBoolean#compareAndSet(boolean, boolean)}. Users can provide callbacks (via optional
* {@link Runnable}s) for either the initial close and/or any subsequent closes.
*
*
*
* Here's an example:
*
*
*
* public class MyDataFile implements Closeable {
*
* private final IdempotentCloser closer = new IdempotentCloser();
*
* private final File file;
*
* . . .
*
* public boolean write() {
* closer.assertOpen(() -> String.format("Data file %s already closed!", file));
* writeToFile();
* }
*
* public boolean isClosed() {
* return closer.isClosed();
* }
*
* @Override
* public void close() {
* Runnable onInitialClose = () -> {
* cleanUpFile(file);
* log.debug("Data file {} closed", file);
* };
* Runnable onSubsequentClose = () -> {
* log.warn("Data file {} already closed!", file);
* };
* closer.close(onInitialClose, onSubsequentClose);
* }
* }
*
*/
public class IdempotentCloser implements AutoCloseable {
private final AtomicBoolean isClosed;
/**
* Creates an {@code IdempotentCloser} that is not yet closed.
*/
public IdempotentCloser() {
this(false);
}
/**
* Creates an {@code IdempotentCloser} with the given initial state.
*
* @param isClosed Initial value for underlying state
*/
public IdempotentCloser(boolean isClosed) {
this.isClosed = new AtomicBoolean(isClosed);
}
/**
* This method serves as an assert that the {@link IdempotentCloser} is still open. If it is open, this method
* simply returns. If it is closed, a new {@link IllegalStateException} will be thrown using the supplied message.
*
* @param message {@link Supplier} that supplies the message for the exception
*/
public void assertOpen(Supplier message) {
if (isClosed.get())
throw new IllegalStateException(message.get());
}
/**
* This method serves as an assert that the {@link IdempotentCloser} is still open. If it is open, this method
* simply returns. If it is closed, a new {@link IllegalStateException} will be thrown using the given message.
*
* @param message Message to use for the exception
*/
public void assertOpen(String message) {
if (isClosed.get())
throw new IllegalStateException(message);
}
public boolean isClosed() {
return isClosed.get();
}
/**
* Closes the resource in a thread-safe manner.
*
*
*
* After the execution has completed, calls to {@link #isClosed()} will return {@code false} and calls to
* {@link #assertOpen(String)} and {@link #assertOpen(Supplier)}
* will throw an {@link IllegalStateException}.
*/
@Override
public void close() {
close(null, null);
}
/**
* Closes the resource in a thread-safe manner.
*
*
*
* After the execution has completed, calls to {@link #isClosed()} will return {@code false} and calls to
* {@link #assertOpen(String)} and {@link #assertOpen(Supplier)}
* will throw an {@link IllegalStateException}.
*
* @param onInitialClose Optional {@link Runnable} to execute when the resource is closed. Note that the
* object will still be considered closed even if an exception is thrown during the course
* of its execution; can be {@code null}
*/
public void close(final Runnable onInitialClose) {
close(onInitialClose, null);
}
/**
* Closes the resource in a thread-safe manner.
*
*
*
* After the execution has completed, calls to {@link #isClosed()} will return {@code false} and calls to
* {@link #assertOpen(String)} and {@link #assertOpen(Supplier)}
* will throw an {@link IllegalStateException}.
*
* @param onInitialClose Optional {@link Runnable} to execute when the resource is closed. Note that the
* object will still be considered closed even if an exception is thrown during the course
* of its execution; can be {@code null}
* @param onSubsequentClose Optional {@link Runnable} to execute if this resource was previously closed. Note that
* no state will be affected if an exception is thrown during its execution; can be
* {@code null}
*/
public void close(final Runnable onInitialClose, final Runnable onSubsequentClose) {
if (isClosed.compareAndSet(false, true)) {
if (onInitialClose != null)
onInitialClose.run();
} else {
if (onSubsequentClose != null)
onSubsequentClose.run();
}
}
@Override
public String toString() {
return "IdempotentCloser{" +
"isClosed=" + isClosed +
'}';
}
}