Package com.google.common.util.concurrent

Class ForwardingListenableFuture<V extends @Nullable Object>

java.lang.Object

com.google.common.collect.ForwardingObject

com.google.common.util.concurrent.ForwardingFuture<V>

com.google.common.util.concurrent.ForwardingListenableFuture<V>

All Implemented Interfaces:

ListenableFuture<V>, Future<V>

Direct Known Subclasses:

ForwardingListenableFuture.SimpleForwardingListenableFuture

@CanIgnoreReturnValue
@GwtCompatible
public abstract class ForwardingListenableFuture<V extends @Nullable Object>
extends ForwardingFuture<V>
implements ListenableFuture<V>

A ListenableFuture which forwards all its method calls to another future. Subclasses should override one or more methods to modify the behavior of the backing future as desired per the decorator pattern.

Most subclasses can just use ForwardingListenableFuture.SimpleForwardingListenableFuture.

Since:

4.0

Author:

Shardul Deo

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static class	ForwardingListenableFuture.SimpleForwardingListenableFuture<V extends @Nullable Object>	A simplified version of ForwardingListenableFuture where subclasses can pass in an already constructed ListenableFuture as the delegate.

Nested classes/interfaces inherited from class com.google.common.util.concurrent.ForwardingFuture

ForwardingFuture.SimpleForwardingFuture<V extends @Nullable Object>

Constructor Summary

Constructors

Modifier	Constructor	Description
protected	ForwardingListenableFuture()	Constructor for use by subclasses.

Method Summary

Modifier and Type	Method	Description
void	addListener(Runnable listener, Executor exec)	Registers a listener to be run on the given executor.
protected abstract ListenableFuture<? extends V>	delegate()	Returns the backing delegate instance that methods are forwarded to.

Methods inherited from class com.google.common.util.concurrent.ForwardingFuture

cancel, get, get, isCancelled, isDone

Methods inherited from class com.google.common.collect.ForwardingObject

toString

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Methods inherited from interface java.util.concurrent.Future

cancel, get, get, isCancelled, isDone

Constructor Detail

ForwardingListenableFuture

protected ForwardingListenableFuture()

Constructor for use by subclasses.

Method Detail

delegate

protected abstract ListenableFuture<? extends V> delegate()

Description copied from class: ForwardingObject

Returns the backing delegate instance that methods are forwarded to. Abstract subclasses generally override this method with an abstract method that has a more specific return type, such as ForwardingSet.delegate(). Concrete subclasses override this method to supply the instance being decorated.

Specified by:

delegate in class ForwardingFuture<V extends @Nullable Object>

addListener

public void addListener(Runnable listener,
                        Executor exec)

Description copied from interface: ListenableFuture

Registers a listener to be run on the given executor. The listener will run when the Future's computation is complete or, if the computation is already complete, immediately.

There is no guaranteed ordering of execution of listeners, but any listener added through this method is guaranteed to be called once the computation is complete.

Exceptions thrown by a listener will be propagated up to the executor. Any exception thrown during Executor.execute (e.g., a RejectedExecutionException or an exception thrown by direct execution) will be caught and logged.

Note: If your listener is lightweight -- and will not cause stack overflow by completing more futures or adding more directExecutor() listeners inline -- consider MoreExecutors.directExecutor(). Otherwise, avoid it: See the warnings on the docs for directExecutor.

This is the most general listener interface. For common operations performed using listeners, see Futures. For a simplified but general listener interface, see addCallback().

Memory consistency effects: Actions in a thread prior to adding a listener happen-before its execution begins, perhaps in another thread.

Guava implementations of ListenableFuture promptly release references to listeners after executing them.

Specified by:

addListener in interface ListenableFuture<V extends @Nullable Object>

Parameters:

listener - the listener to run when the computation is complete

exec - the executor to run the listener in