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(Runnable listener,
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(Runnable listener, 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 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. Heavyweight directExecutor
listeners can cause problems, and
these problems can be difficult to reproduce because they depend on timing.
For example:
addListener
. That
caller may be a UI thread or other latency-sensitive thread. This can harm
UI responsiveness.
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.
directExecutor
listeners.
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.
addListener
in interface ListenableFuture<V>
listener
- the listener to run when the computation is completeexec
- the executor to run the listener inCopyright © 2010-2015. All Rights Reserved.