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/*
* 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.eclipse.aether.util.concurrency;
import java.util.concurrent.atomic.AtomicInteger;
import java.util.concurrent.atomic.AtomicReference;
import java.util.concurrent.locks.LockSupport;
import static java.util.Objects.requireNonNull;
/**
* A utility class to forward any uncaught {@link Error} or {@link RuntimeException} from a {@link Runnable} executed in
* a worker thread back to the parent thread. The simplified usage pattern looks like this:
*
*
* RunnableErrorForwarder errorForwarder = new RunnableErrorForwarder();
* for ( Runnable task : tasks )
* {
* executor.execute( errorForwarder.wrap( task ) );
* }
* errorForwarder.await();
*
*/
public final class RunnableErrorForwarder {
private final Thread thread = Thread.currentThread();
private final AtomicInteger counter = new AtomicInteger();
private final AtomicReference error = new AtomicReference<>();
/**
* Creates a new error forwarder for worker threads spawned by the current thread.
*/
public RunnableErrorForwarder() {}
/**
* Wraps the specified runnable into an equivalent runnable that will allow forwarding of uncaught errors.
*
* @param runnable The runnable from which to forward errors, must not be {@code null}.
* @return The error-forwarding runnable to eventually execute, never {@code null}.
*/
public Runnable wrap(final Runnable runnable) {
requireNonNull(runnable, "runnable cannot be null");
counter.incrementAndGet();
return () -> {
try {
runnable.run();
} catch (RuntimeException | Error e) {
error.compareAndSet(null, e);
throw e;
} finally {
counter.decrementAndGet();
LockSupport.unpark(thread);
}
};
}
/**
* Causes the current thread to wait until all previously {@link #wrap(Runnable) wrapped} runnables have terminated
* and potentially re-throws an uncaught {@link RuntimeException} or {@link Error} from any of the runnables. In
* case multiple runnables encountered uncaught errors, one error is arbitrarily selected. Note: This
* method must be called from the same thread that created this error forwarder instance.
*/
public void await() {
awaitTerminationOfAllRunnables();
Throwable error = this.error.get();
if (error != null) {
if (error instanceof RuntimeException) {
throw (RuntimeException) error;
} else if (error instanceof ThreadDeath) {
throw new IllegalStateException(error);
} else if (error instanceof Error) {
throw (Error) error;
}
throw new IllegalStateException(error);
}
}
private void awaitTerminationOfAllRunnables() {
if (!thread.equals(Thread.currentThread())) {
throw new IllegalStateException(
"wrong caller thread, expected " + thread + " and not " + Thread.currentThread());
}
boolean interrupted = false;
while (counter.get() > 0) {
LockSupport.park();
if (Thread.interrupted()) {
interrupted = true;
}
}
if (interrupted) {
Thread.currentThread().interrupt();
}
}
}