/
FuturePromise.java
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/
FuturePromise.java
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//
// ========================================================================
// Copyright (c) 1995-2021 Mort Bay Consulting Pty Ltd and others.
//
// This program and the accompanying materials are made available under the
// terms of the Eclipse Public License v. 2.0 which is available at
// https://www.eclipse.org/legal/epl-2.0, or the Apache License, Version 2.0
// which is available at https://www.apache.org/licenses/LICENSE-2.0.
//
// SPDX-License-Identifier: EPL-2.0 OR Apache-2.0
// ========================================================================
//
package org.eclipse.jetty.util;
import java.io.IOException;
import java.util.concurrent.CancellationException;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.Future;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.TimeoutException;
import java.util.concurrent.atomic.AtomicBoolean;
public class FuturePromise<C> implements Future<C>, Promise<C>
{
private static Throwable COMPLETED = new ConstantThrowable();
private final AtomicBoolean _done = new AtomicBoolean(false);
private final CountDownLatch _latch = new CountDownLatch(1);
private Throwable _cause;
private C _result;
public FuturePromise()
{
}
public FuturePromise(C result)
{
_cause = COMPLETED;
_result = result;
_done.set(true);
_latch.countDown();
}
public FuturePromise(C ctx, Throwable failed)
{
_result = ctx;
_cause = failed;
_done.set(true);
_latch.countDown();
}
@Override
public void succeeded(C result)
{
if (_done.compareAndSet(false, true))
{
_result = result;
_cause = COMPLETED;
_latch.countDown();
}
}
@Override
public void failed(Throwable cause)
{
if (_done.compareAndSet(false, true))
{
_cause = cause;
_latch.countDown();
}
}
@Override
public boolean cancel(boolean mayInterruptIfRunning)
{
if (_done.compareAndSet(false, true))
{
_result = null;
_cause = new CancellationException();
_latch.countDown();
return true;
}
return false;
}
@Override
public boolean isCancelled()
{
if (_done.get())
{
try
{
_latch.await();
}
catch (InterruptedException e)
{
throw new RuntimeException(e);
}
return _cause instanceof CancellationException;
}
return false;
}
@Override
public boolean isDone()
{
return _done.get() && _latch.getCount() == 0;
}
@Override
public C get() throws InterruptedException, ExecutionException
{
_latch.await();
if (_cause == COMPLETED)
return _result;
if (_cause instanceof CancellationException)
throw (CancellationException)new CancellationException().initCause(_cause);
throw new ExecutionException(_cause);
}
/**
* Return the result if completed successfully
* or in the case of failure, throw the
* Exception/Error, or an ExecutionException wrapping
* the cause if it is neither an Exception or Error.
*
* @return the computed result
* @throws Exception if the cause is an Exception or Error,
* otherwise an ExecutionException wrapping the cause
*/
public C getOrThrow() throws Exception
{
_latch.await();
if (_cause == COMPLETED)
return _result;
if (_cause instanceof Exception)
throw (Exception)_cause;
if (_cause instanceof Error)
throw (Error)_cause;
throw new ExecutionException(_cause);
}
@Override
public C get(long timeout, TimeUnit unit) throws InterruptedException, ExecutionException, TimeoutException
{
if (!_latch.await(timeout, unit))
throw new TimeoutException();
if (_cause == COMPLETED)
return _result;
if (_cause instanceof TimeoutException)
throw (TimeoutException)_cause;
if (_cause instanceof CancellationException)
throw (CancellationException)new CancellationException().initCause(_cause);
throw new ExecutionException(_cause);
}
public static void rethrow(ExecutionException e) throws IOException
{
Throwable cause = e.getCause();
if (cause instanceof IOException)
throw (IOException)cause;
if (cause instanceof Error)
throw (Error)cause;
if (cause instanceof RuntimeException)
throw (RuntimeException)cause;
throw new RuntimeException(cause);
}
@Override
public String toString()
{
return String.format("FutureCallback@%x{%b,%b,%s}", hashCode(), _done.get(), _cause == COMPLETED, _result);
}
}