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Utility classes for Jetty
//
// ========================================================================
// Copyright (c) 1995 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.Objects;
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.
*/
Callback NOOP = new Callback()
{
@Override
public InvocationType getInvocationType()
{
return InvocationType.NON_BLOCKING;
}
@Override
public String toString()
{
return "Callback.NOOP";
}
};
/**
* Completes this callback with the given {@link CompletableFuture}.
* When the CompletableFuture completes normally, this callback is succeeded;
* when the CompletableFuture completes exceptionally, this callback is failed.
*
* @param completable the CompletableFuture that completes this callback
*/
default void completeWith(CompletableFuture completable)
{
completable.whenComplete((o, x) ->
{
if (x == null)
succeeded();
else
failed(x);
});
}
/**
* 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)
{
try
{
completable.completeExceptionally(x);
}
catch (Throwable t)
{
ExceptionUtil.addSuppressedIfNotAssociated(t, x);
throw t;
}
}
@Override
public InvocationType getInvocationType()
{
return invocation;
}
};
}
/**
* Creates a callback from the given success and failure lambdas.
*
* @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 from(InvocationType.BLOCKING, success, failure);
}
/**
* Creates a callback with the given InvocationType from the given success and failure lambdas.
*
* @param invocationType the Callback invocation type
* @param success Called when the callback succeeds
* @param failure Called when the callback fails
* @return a new Callback
*/
static Callback from(InvocationType invocationType, Runnable success, Consumer failure)
{
return new Callback()
{
@Override
public void succeeded()
{
success.run();
}
@Override
public void failed(Throwable x)
{
try
{
failure.accept(x);
}
catch (Throwable t)
{
ExceptionUtil.addSuppressedIfNotAssociated(t, x);
throw t;
}
}
@Override
public InvocationType getInvocationType()
{
return invocationType;
}
@Override
public String toString()
{
return "Callback@%x{%s, %s,%s}".formatted(hashCode(), invocationType, success, failure);
}
};
}
/**
* Creates 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 from(Invocable.getInvocationType(completed), completed);
}
/**
* Creates a Callback with the given {@code invocationType},
* that runs the given {@code Runnable} when it succeeds or fails.
*
* @param invocationType the invocation type of the returned Callback
* @param completed the Runnable to run when the callback either succeeds or fails
* @return a new Callback with the given invocation type
*/
static Callback from(InvocationType invocationType, Runnable completed)
{
return new Completing()
{
@Override
public void completed()
{
completed.run();
}
@Override
public InvocationType getInvocationType()
{
return invocationType;
}
@Override
public String toString()
{
return "Callback.Completing@%x{%s,%s}".formatted(hashCode(), invocationType, completed);
}
};
}
/**
* Creates 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();
}
};
}
/**
* Creates 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, Consumer completed)
{
return new Callback()
{
@Override
public void succeeded()
{
try
{
callback.succeeded();
}
finally
{
completed.accept(null);
}
}
@Override
public void failed(Throwable x)
{
Callback.failed(callback::failed, completed, x);
}
};
}
/**
* Creates 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(callback, t);
}
}
private void completed(Throwable ignored)
{
completed.run();
}
@Override
public void failed(Throwable x)
{
Callback.failed(this::completed, callback::failed, x);
}
};
}
/**
* Creates 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)
{
ExceptionUtil.addSuppressedIfNotAssociated(cause, x);
Callback.failed(callback, cause);
}
};
}
/**
* Creates 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 combine(callback1, callback2);
}
/**
* A Callback implementation that calls the {@link #completed()} method when it either succeeds or fails.
*/
interface Completing extends Callback
{
void completed();
@Override
default void succeeded()
{
completed();
}
@Override
default void failed(Throwable x)
{
try
{
completed();
}
catch (Throwable t)
{
ExceptionUtil.addSuppressedIfNotAssociated(t, x);
throw t;
}
}
}
/**
* Nested Completing Callback that completes after
* completing the nested callback
*/
class Nested implements Completing
{
private final Callback callback;
public Nested(Callback callback)
{
this.callback = Objects.requireNonNull(callback);
}
public Callback getCallback()
{
return callback;
}
@Override
public void completed()
{
}
private void completed(Throwable ignored)
{
completed();
}
@Override
public void succeeded()
{
try
{
callback.succeeded();
}
finally
{
completed();
}
}
@Override
public void failed(Throwable x)
{
Callback.failed(callback::failed, this::completed, x);
}
@Override
public InvocationType getInvocationType()
{
return callback.getInvocationType();
}
@Override
public String toString()
{
return "%s@%x:%s".formatted(getClass().getSimpleName(), hashCode(), callback);
}
}
static Callback combine(Callback cb1, Callback cb2)
{
if (cb1 == null || cb1 == cb2)
return cb2;
if (cb2 == null)
return cb1;
return new Callback()
{
@Override
public void succeeded()
{
try
{
cb1.succeeded();
}
finally
{
cb2.succeeded();
}
}
@Override
public void failed(Throwable x)
{
Callback.failed(cb1::failed, cb2::failed, x);
}
@Override
public InvocationType getInvocationType()
{
return Invocable.combine(Invocable.getInvocationType(cb1), Invocable.getInvocationType(cb2));
}
};
}
/**
* A {@link CompletableFuture} that is also a {@link Callback}.
*/
class Completable extends CompletableFuture implements Callback
{
/**
* Creates a new {@code Completable} to be consumed by the given
* {@code consumer}, then returns the newly created {@code Completable}.
*
* @param consumer the code that consumes the newly created {@code Completable}
* @return the newly created {@code Completable}
*/
public static Completable with(Consumer consumer)
{
Completable completable = new Completable();
consumer.accept(completable);
return completable;
}
/**
* Creates a completable future given a callback.
*
* @param callback The nested callback.
* @return a new Completable which will succeed this callback when completed.
*/
public static Completable from(Callback callback)
{
return new Completable(callback.getInvocationType())
{
@Override
public void succeeded()
{
callback.succeeded();
super.succeeded();
}
@Override
public void failed(Throwable x)
{
Callback.failed(callback::failed, super::failed, x);
}
};
}
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;
}
/**
* Returns a new {@link Completable} that, when this {@link Completable}
* succeeds, is passed to the given consumer and then returned.
* If this {@link Completable} fails, the new {@link Completable} is
* also failed, and the consumer is not invoked.
*
* @param consumer the consumer that receives the {@link Completable}
* @return a new {@link Completable} passed to the consumer
* @see #with(Consumer)
*/
public Completable compose(Consumer consumer)
{
Completable completable = new Completable();
whenComplete((r, x) ->
{
if (x == null)
consumer.accept(completable);
else
completable.failed(x);
});
return completable;
}
}
/**
* Invoke a callback failure, handling any {@link Throwable} thrown
* by adding the passed {@code failure} as a suppressed with
* {@link ExceptionUtil#addSuppressedIfNotAssociated(Throwable, Throwable)}.
* @param callback The callback to fail
* @param failure The failure
* @throws RuntimeException If thrown, will have the {@code failure} added as a suppressed.
*/
private static void failed(Callback callback, Throwable failure)
{
try
{
callback.failed(failure);
}
catch (Throwable t)
{
ExceptionUtil.addSuppressedIfNotAssociated(t, failure);
throw t;
}
}
/**
* Invoke two consumers of a failure, handling any {@link Throwable} thrown
* by adding the passed {@code failure} as a suppressed with
* {@link ExceptionUtil#addSuppressedIfNotAssociated(Throwable, Throwable)}.
* @param first The first consumer of a failure
* @param second The first consumer of a failure
* @param failure The failure
* @throws RuntimeException If thrown, will have the {@code failure} added as a suppressed.
*/
private static void failed(Consumer first, Consumer second, Throwable failure)
{
// This is an improved version of:
// try
// {
// first.accept(failure);
// }
// finally
// {
// second.accept(failure);
// }
try
{
first.accept(failure);
}
catch (Throwable t)
{
ExceptionUtil.addSuppressedIfNotAssociated(failure, t);
}
try
{
second.accept(failure);
}
catch (Throwable t)
{
ExceptionUtil.addSuppressedIfNotAssociated(t, failure);
throw t;
}
}
}