Class JdkFutureAdapters.ListenableFutureAdapter<V>

  • All Implemented Interfaces:
    ListenableFuture<V>, java.util.concurrent.Future<V>
    Enclosing class:
    JdkFutureAdapters

    private static class JdkFutureAdapters.ListenableFutureAdapter<V>
    extends ForwardingFuture<V>
    implements ListenableFuture<V>
    An adapter to turn a Future into a ListenableFuture. This will wait on the future to finish, and when it completes, run the listeners. This implementation will wait on the source future indefinitely, so if the source future never completes, the adapter will never complete either.

    If the delegate future is interrupted or throws an unexpected unchecked exception, the listeners will not be invoked.

    • Field Detail

      • threadFactory

        private static final java.util.concurrent.ThreadFactory threadFactory
      • defaultAdapterExecutor

        private static final java.util.concurrent.Executor defaultAdapterExecutor
      • adapterExecutor

        private final java.util.concurrent.Executor adapterExecutor
      • hasListeners

        private final java.util.concurrent.atomic.AtomicBoolean hasListeners
      • delegate

        private final java.util.concurrent.Future<V> delegate
    • Constructor Detail

      • ListenableFutureAdapter

        ListenableFutureAdapter​(java.util.concurrent.Future<V> delegate)
      • ListenableFutureAdapter

        ListenableFutureAdapter​(java.util.concurrent.Future<V> delegate,
                                java.util.concurrent.Executor adapterExecutor)
    • Method Detail

      • delegate

        protected java.util.concurrent.Future<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>
      • 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 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: 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:

        • 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, 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>
        Parameters:
        listener - the listener to run when the computation is complete
        exec - the executor to run the listener in