@GwtCompatible public 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<? extends V> |
delegate()
Returns the backing delegate instance that methods are forwarded to.
|
cancel, get, get, isCancelled, isDonetoStringprotected ForwardingListenableFuture()
protected abstract ListenableFuture<? extends V> delegate()
ForwardingObjectForwardingSet.delegate(). Concrete subclasses override this method to supply
the instance being decorated.delegate in class ForwardingFuture<V>public void addListener(Runnable listener, Executor exec)
ListenableFutureFuture'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 © 2010–2017. All rights reserved.