V
- The result type returned by this Future's get
methodpublic abstract class ForwardingListenableFuture<V> extends ForwardingFuture<V> implements ListenableFuture<V>
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
.
Modifier and Type | Class and Description |
---|---|
static class |
ForwardingListenableFuture.SimpleForwardingListenableFuture<V>
A simplified version of
ForwardingListenableFuture where subclasses
can pass in an already constructed ListenableFuture
as the delegate. |
ForwardingFuture.SimpleForwardingFuture<V>
Modifier | Constructor and Description |
---|---|
protected |
ForwardingListenableFuture()
Constructor for use by subclasses.
|
Modifier and Type | Method and 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<V> |
delegate()
Returns the backing delegate instance that methods are forwarded to.
|
cancel, get, get, isCancelled, isDone
toString
protected ForwardingListenableFuture()
protected abstract ListenableFuture<V> delegate()
ForwardingObject
ForwardingSet.delegate()
. Concrete subclasses override this method to supply
the instance being decorated.delegate
in class ForwardingFuture<V>
public void addListener(java.lang.Runnable listener, java.util.concurrent.Executor exec)
ListenableFuture
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 inline execution) will be caught and
logged.
Note: For fast, lightweight listeners that would be safe to execute in
any thread, consider MoreExecutors.sameThreadExecutor()
. For heavier
listeners, sameThreadExecutor()
carries some caveats: First, the
thread that the listener runs in depends on whether the Future
is
done at the time it is added and on whether it is ever canclled. In
particular, listeners may run in the thread that calls addListener
or the thread that calls cancel
. Second, listeners may run in an
internal thread of the system responsible for the input Future
,
such as an RPC network thread. Finally, during the execution of a sameThreadExecutor()
listener, all other registered but unexecuted
listeners are prevented from running, even if those listeners are to run
in other executors.
This is the most general listener interface.
For common operations performed using listeners,
see Futures
addListener
in interface ListenableFuture<V>
listener
- the listener to run when the computation is completeexec
- the executor to run the listener in