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Utility classes for Jetty
//
// ========================================================================
// 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.util.concurrent.CompletableFuture;
import java.util.function.Consumer;
import org.eclipse.jetty.util.thread.Invocable;
/**
* A callback abstraction that handles completed/failed events of asynchronous operations.
*
* Semantically this is equivalent to an optimise Promise<Void>, but callback is a more meaningful
* name than EmptyPromise
*/
public interface Callback extends Invocable
{
/**
* Instance of Adapter that can be used when the callback methods need an empty
* implementation without incurring in the cost of allocating a new Adapter object.
*/
static Callback NOOP = new Callback()
{
@Override
public InvocationType getInvocationType()
{
return InvocationType.NON_BLOCKING;
}
};
/**
* Callback invoked when the operation completes.
*
* @see #failed(Throwable)
*/
default void succeeded()
{
}
/**
* Callback invoked when the operation fails.
*
* @param x the reason for the operation failure
*/
default void failed(Throwable x)
{
}
/**
* Creates a non-blocking callback from the given incomplete CompletableFuture.
* When the callback completes, either succeeding or failing, the
* CompletableFuture is also completed, respectively via
* {@link CompletableFuture#complete(Object)} or
* {@link CompletableFuture#completeExceptionally(Throwable)}.
*
* @param completable the CompletableFuture to convert into a callback
* @return a callback that when completed, completes the given CompletableFuture
*/
static Callback from(CompletableFuture completable)
{
return from(completable, InvocationType.NON_BLOCKING);
}
/**
* Creates a callback from the given incomplete CompletableFuture,
* with the given {@code blocking} characteristic.
*
* @param completable the CompletableFuture to convert into a callback
* @param invocation whether the callback is blocking
* @return a callback that when completed, completes the given CompletableFuture
*/
static Callback from(CompletableFuture completable, InvocationType invocation)
{
if (completable instanceof Callback)
return (Callback)completable;
return new Callback()
{
@Override
public void succeeded()
{
completable.complete(null);
}
@Override
public void failed(Throwable x)
{
completable.completeExceptionally(x);
}
@Override
public InvocationType getInvocationType()
{
return invocation;
}
};
}
/**
* Create a callback from the passed success and failure
*
* @param success Called when the callback succeeds
* @param failure Called when the callback fails
* @return a new Callback
*/
static Callback from(Runnable success, Consumer failure)
{
return new Callback()
{
@Override
public void succeeded()
{
success.run();
}
@Override
public void failed(Throwable x)
{
failure.accept(x);
}
};
}
/**
* Creaste a callback that runs completed when it succeeds or fails
*
* @param completed The completion to run on success or failure
* @return a new callback
*/
static Callback from(Runnable completed)
{
return new Completing()
{
public void completed()
{
completed.run();
}
};
}
/**
* Create a nested callback that runs completed after
* completing the nested callback.
*
* @param callback The nested callback
* @param completed The completion to run after the nested callback is completed
* @return a new callback.
*/
static Callback from(Callback callback, Runnable completed)
{
return new Nested(callback)
{
public void completed()
{
completed.run();
}
};
}
/**
* Create a nested callback that runs completed before
* completing the nested callback.
*
* @param callback The nested callback
* @param completed The completion to run before the nested callback is completed. Any exceptions thrown
* from completed will result in a callback failure.
* @return a new callback.
*/
static Callback from(Runnable completed, Callback callback)
{
return new Callback()
{
@Override
public void succeeded()
{
try
{
completed.run();
callback.succeeded();
}
catch (Throwable t)
{
callback.failed(t);
}
}
@Override
public void failed(Throwable x)
{
try
{
completed.run();
}
catch (Throwable t)
{
x.addSuppressed(t);
}
callback.failed(x);
}
};
}
/**
* Create a nested callback which always fails the nested callback on completion.
*
* @param callback The nested callback
* @param cause The cause to fail the nested callback, if the new callback is failed the reason
* will be added to this cause as a suppressed exception.
* @return a new callback.
*/
static Callback from(Callback callback, Throwable cause)
{
return new Callback()
{
@Override
public void succeeded()
{
callback.failed(cause);
}
@Override
public void failed(Throwable x)
{
cause.addSuppressed(x);
callback.failed(cause);
}
};
}
/**
* Create a callback which combines two other callbacks and will succeed or fail them both.
* @param callback1 The first callback
* @param callback2 The second callback
* @return a new callback.
*/
static Callback from(Callback callback1, Callback callback2)
{
return new Callback()
{
@Override
public void succeeded()
{
callback1.succeeded();
callback2.succeeded();
}
@Override
public void failed(Throwable x)
{
callback1.failed(x);
callback2.failed(x);
}
};
}
class Completing implements Callback
{
@Override
public void succeeded()
{
completed();
}
@Override
public void failed(Throwable x)
{
completed();
}
public void completed()
{
}
}
/**
* Nested Completing Callback that completes after
* completing the nested callback
*/
class Nested extends Completing
{
private final Callback callback;
public Nested(Callback callback)
{
this.callback = callback;
}
public Nested(Nested nested)
{
this.callback = nested.callback;
}
public Callback getCallback()
{
return callback;
}
@Override
public void succeeded()
{
try
{
callback.succeeded();
}
finally
{
completed();
}
}
@Override
public void failed(Throwable x)
{
try
{
callback.failed(x);
}
finally
{
completed();
}
}
@Override
public InvocationType getInvocationType()
{
return callback.getInvocationType();
}
}
interface InvocableCallback extends Invocable, Callback
{
}
static Callback combine(Callback cb1, Callback cb2)
{
if (cb1 == null || cb1 == cb2)
return cb2;
if (cb2 == null)
return cb1;
return new InvocableCallback()
{
@Override
public void succeeded()
{
try
{
cb1.succeeded();
}
finally
{
cb2.succeeded();
}
}
@Override
public void failed(Throwable x)
{
try
{
cb1.failed(x);
}
catch (Throwable t)
{
if (x != t)
x.addSuppressed(t);
}
finally
{
cb2.failed(x);
}
}
@Override
public InvocationType getInvocationType()
{
return Invocable.combine(Invocable.getInvocationType(cb1), Invocable.getInvocationType(cb2));
}
};
}
/**
* A CompletableFuture that is also a Callback.
*/
class Completable extends CompletableFuture implements Callback
{
private final InvocationType invocation;
public Completable()
{
this(Invocable.InvocationType.NON_BLOCKING);
}
public Completable(InvocationType invocation)
{
this.invocation = invocation;
}
@Override
public void succeeded()
{
complete(null);
}
@Override
public void failed(Throwable x)
{
completeExceptionally(x);
}
@Override
public InvocationType getInvocationType()
{
return invocation;
}
}
}