org.elasticsearch.common.util.concurrent

Class BaseFuture<V>

java.lang.Object

org.elasticsearch.common.util.concurrent.BaseFuture<V>

All Implemented Interfaces:

Future<V>

Direct Known Subclasses:

AdapterActionFuture, PlainTransportFuture

public abstract class BaseFuture<V>
extends Object
implements Future<V>

An abstract implementation of the ListenableFuture interface. This class is preferable to FutureTask for two reasons: It implements ListenableFuture, and it does not implement Runnable. (If you want a Runnable implementation of ListenableFuture, create a ListenableFutureTask, or submit your tasks to a ListeningExecutorService.)

This class implements all methods in ListenableFuture. Subclasses should provide a way to set the result of the computation through the protected methods set(Object) and setException(Throwable). Subclasses may also override interruptTask(), which will be invoked automatically if a call to cancel(true) succeeds in canceling the future.

AbstractFuture uses an AbstractQueuedSynchronizer to deal with concurrency issues and guarantee thread safety.

The state changing methods all return a boolean indicating success or failure in changing the future's state. Valid states are running, completed, failed, or cancelled.

This class uses an ExecutionList to guarantee that all registered listeners will be executed, either when the future finishes or, for listeners that are added after the future completes, immediately. Runnable-Executor pairs are stored in the execution list but are not necessarily executed in the order in which they were added. (If a listener is added after the Future is complete, it will be executed immediately, even if earlier listeners have not been executed. Additionally, executors need not guarantee FIFO execution, or different listeners may run in different executors.)

Since:

1.0

Author:

Sven Mawson

Constructor Summary

Constructors

Constructor and Description
BaseFuture()

Method Summary

Methods

Modifier and Type	Method and Description
boolean	cancel(boolean mayInterruptIfRunning)
protected void	done()
V	get()
V	get(long timeout, TimeUnit unit)
protected void	interruptTask() Subclasses can override this method to implement interruption of the future's computation.
boolean	isCancelled()
boolean	isDone()
protected boolean	set(V value) Subclasses should invoke this method to set the result of the computation to value.
protected boolean	setException(Throwable throwable) Subclasses should invoke this method to set the result of the computation to an error, throwable.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

BaseFuture

public BaseFuture()

Method Detail

get

public V get(long timeout,
    TimeUnit unit)
      throws InterruptedException,
             TimeoutException,
             ExecutionException

The default BaseFuture implementation throws InterruptedException if the current thread is interrupted before or during the call, even if the value is already available.

Specified by:

get in interface Future<V>

Throws:

InterruptedException - if the current thread was interrupted before or during the call (optional but recommended).

CancellationException

TimeoutException

ExecutionException

get

public V get()
      throws InterruptedException,
             ExecutionException

The default BaseFuture implementation throws InterruptedException if the current thread is interrupted before or during the call, even if the value is already available.

Specified by:

get in interface Future<V>

Throws:

InterruptedException - if the current thread was interrupted before or during the call (optional but recommended).

CancellationException

ExecutionException

isDone

public boolean isDone()

Specified by:

isDone in interface Future<V>

isCancelled

public boolean isCancelled()

Specified by:

isCancelled in interface Future<V>

cancel

public boolean cancel(boolean mayInterruptIfRunning)

Specified by:

cancel in interface Future<V>

interruptTask

protected void interruptTask()

Subclasses can override this method to implement interruption of the future's computation. The method is invoked automatically by a successful call to cancel(true).

The default implementation does nothing.

Since:

10.0

set

protected boolean set(@Nullable
          V value)

Subclasses should invoke this method to set the result of the computation to value. This will set the state of the future to BaseFuture.Sync.COMPLETED and call done() if the state was successfully changed.

Parameters:

value - the value that was the result of the task.

Returns:

true if the state was successfully changed.

setException

protected boolean setException(Throwable throwable)

Subclasses should invoke this method to set the result of the computation to an error, throwable. This will set the state of the future to BaseFuture.Sync.COMPLETED and call done() if the state was successfully changed.

Parameters:

throwable - the exception that the task failed with.

Returns:

true if the state was successfully changed.

Throws:

Error - if the throwable was an Error.

done

protected void done()