org.eclipse.jetty.util.BlockingCallback Maven / Gradle / Ivy
//
// ========================================================================
// Copyright (c) 1995-2018 Mort Bay Consulting Pty. Ltd.
// ------------------------------------------------------------------------
// All rights reserved. This program and the accompanying materials
// are made available under the terms of the Eclipse Public License v1.0
// and Apache License v2.0 which accompanies this distribution.
//
// The Eclipse Public License is available at
// http://www.eclipse.org/legal/epl-v10.html
//
// The Apache License v2.0 is available at
// http://www.opensource.org/licenses/apache2.0.php
//
// You may elect to redistribute this code under either of these licenses.
// ========================================================================
//
package org.eclipse.jetty.util;
import java.io.IOException;
import java.io.InterruptedIOException;
import java.util.concurrent.CancellationException;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.atomic.AtomicReference;
import org.eclipse.jetty.util.log.Log;
import org.eclipse.jetty.util.log.Logger;
import org.eclipse.jetty.util.thread.NonBlockingThread;
/* ------------------------------------------------------------ */
/**
* An implementation of Callback that blocks until success or failure.
*/
public class BlockingCallback implements Callback
{
private static final Logger LOG = Log.getLogger(BlockingCallback.class);
private static Throwable SUCCEEDED = new ConstantThrowable("SUCCEEDED");
private final CountDownLatch _latch = new CountDownLatch(1);
private final AtomicReference _state = new AtomicReference<>();
public BlockingCallback()
{}
@Override
public void succeeded()
{
if (_state.compareAndSet(null,SUCCEEDED))
_latch.countDown();
}
@Override
public void failed(Throwable cause)
{
if (_state.compareAndSet(null,cause))
_latch.countDown();
}
/** Block until the Callback has succeeded or failed and
* after the return leave in the state to allow reuse.
* This is useful for code that wants to repeatable use a FutureCallback to convert
* an asynchronous API to a blocking API.
* @throws IOException if exception was caught during blocking, or callback was cancelled
*/
public void block() throws IOException
{
if (NonBlockingThread.isNonBlockingThread())
LOG.warn("Blocking a NonBlockingThread: ",new Throwable());
try
{
_latch.await();
Throwable state=_state.get();
if (state==SUCCEEDED)
return;
if (state instanceof IOException)
throw (IOException) state;
if (state instanceof CancellationException)
throw (CancellationException) state;
throw new IOException(state);
}
catch (final InterruptedException e)
{
throw new InterruptedIOException(){{initCause(e);}};
}
finally
{
_state.set(null);
}
}
@Override
public String toString()
{
return String.format("%s@%x{%s}",BlockingCallback.class.getSimpleName(),hashCode(),_state.get());
}
}