Class ForwardingListenableFuture<V>
- 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>
,java.util.concurrent.Future<V>
- Direct Known Subclasses:
ForwardingCheckedFuture
,ForwardingListenableFuture.SimpleForwardingListenableFuture
@GwtIncompatible public abstract class ForwardingListenableFuture<V> extends ForwardingFuture<V> implements ListenableFuture<V>
AListenableFuture
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
-
-
Nested Class Summary
Nested Classes Modifier and Type Class Description static class
ForwardingListenableFuture.SimpleForwardingListenableFuture<V>
A simplified version ofForwardingListenableFuture
where subclasses can pass in an already constructedListenableFuture
as the delegate.-
Nested classes/interfaces inherited from class com.google.common.util.concurrent.ForwardingFuture
ForwardingFuture.SimpleForwardingFuture<V>
-
-
Constructor Summary
Constructors Modifier Constructor Description protected
ForwardingListenableFuture()
Constructor for use by subclasses.
-
Method Summary
All Methods Instance Methods Abstract Methods Concrete Methods Modifier and Type Method Description void
addListener(java.lang.Runnable listener, java.util.concurrent.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
-
-
-
-
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 asForwardingSet.delegate()
. Concrete subclasses override this method to supply the instance being decorated.- Specified by:
delegate
in classForwardingFuture<V>
-
addListener
public void addListener(java.lang.Runnable listener, java.util.concurrent.Executor exec)
Description copied from interface:ListenableFuture
Registers a listener to be run on the given executor. The listener will run when theFuture
'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., aRejectedExecutionException
or an exception thrown by direct execution) will be caught and logged.Note: For fast, lightweight listeners that would be safe to execute in any thread, consider
MoreExecutors.directExecutor()
. Otherwise, avoid it. HeavyweightdirectExecutor
listeners can cause problems, and these problems can be difficult to reproduce because they depend on timing. For example:- The listener may be executed by the caller of
addListener
. That caller may be a UI thread or other latency-sensitive thread. This can harm UI responsiveness. - The listener may be executed by the thread that completes this
Future
. That thread may be an internal system thread such as an RPC network thread. Blocking that thread may stall progress of the whole system. It may even cause a deadlock. - The listener may delay other listeners, even listeners that are not themselves
directExecutor
listeners.
This is the most general listener interface. For common operations performed using listeners, see
Futures
. For a simplified but general listener interface, seeaddCallback()
.Memory consistency effects: Actions in a thread prior to adding a listener happen-before its execution begins, perhaps in another thread.
- Specified by:
addListener
in interfaceListenableFuture<V>
- Parameters:
listener
- the listener to run when the computation is completeexec
- the executor to run the listener in
- The listener may be executed by the caller of
-
-