com.google.common.util.concurrent
Class AbstractCheckedFuture<V,X extends Exception>

java.lang.Object
  com.google.common.util.concurrent.AbstractCheckedFuture<V,X>

All Implemented Interfaces:

CheckedFuture<V,X>, ListenableFuture<V>, Future<V>

@Beta
public abstract class AbstractCheckedFuture<V,X extends Exception>
extends Object
implements CheckedFuture<V,X>

A delegating wrapper around a ListenableFuture that adds support for the checkedGet() and checkedGet(long, TimeUnit) methods.

Since:

1

Author:

Sven Mawson

delegate

protected final ListenableFuture<V> delegate

The delegate, used to pass along all our methods.

AbstractCheckedFuture

protected AbstractCheckedFuture(ListenableFuture<V> delegate)

Constructs an AbstractCheckedFuture that wraps a delegate.

mapException

protected abstract X mapException(Exception e)

Translates from an InterruptedException, CancellationException or ExecutionException thrown by get to an exception of type X to be thrown by checkedGet. Subclasses must implement this method.

If e is an InterruptedException, the calling checkedGet method has already restored the interrupt after catching the exception. If an implementation of mapException(Exception) wishes to swallow the interrupt, it can do so by calling Thread.interrupted().

checkedGet

public V checkedGet()
             throws X extends Exception

Exception checking version of Future.get() that will translate InterruptedException, CancellationException and ExecutionException into application-specific exceptions.

This implementation calls get() and maps that method's standard exceptions to instances of type X using mapException(java.lang.Exception).

In addition, if get throws an InterruptedException, this implementation will set the current thread's interrupt status before calling mapException.

Specified by:

checkedGet in interface CheckedFuture<V,X extends Exception>

Returns:

the result of executing the future.

Throws:

X - if get() throws an InterruptedException, CancellationException, or ExecutionException

X extends Exception

checkedGet

public V checkedGet(long timeout,
                    TimeUnit unit)
             throws TimeoutException,
                    X extends Exception

Exception checking version of Future.get(long, TimeUnit) that will translate InterruptedException, CancellationException and ExecutionException into application-specific exceptions. On timeout this method throws a normal TimeoutException.

This implementation calls get(long, TimeUnit) and maps that method's standard exceptions (excluding TimeoutException, which is propagated) to instances of type X using mapException(java.lang.Exception).

In addition, if get throws an InterruptedException, this implementation will set the current thread's interrupt status before calling mapException.

Specified by:

checkedGet in interface CheckedFuture<V,X extends Exception>

Returns:

the result of executing the future.

Throws:

X - if get() throws an InterruptedException, CancellationException, or ExecutionException

TimeoutException - if retrieving the result timed out.

X extends Exception

cancel

public boolean cancel(boolean mayInterruptIfRunning)

Description copied from interface: java.util.concurrent.Future

Attempts to cancel execution of this task. This attempt will fail if the task has already completed, has already been cancelled, or could not be cancelled for some other reason. If successful, and this task has not started when cancel is called, this task should never run. If the task has already started, then the mayInterruptIfRunning parameter determines whether the thread executing this task should be interrupted in an attempt to stop the task.

After this method returns, subsequent calls to Future.isDone() will always return true. Subsequent calls to Future.isCancelled() will always return true if this method returned true.

Specified by:

cancel in interface Future<V>

Parameters:

mayInterruptIfRunning - true if the thread executing this task should be interrupted; otherwise, in-progress tasks are allowed to complete

Returns:

false if the task could not be cancelled, typically because it has already completed normally; true otherwise

isCancelled

public boolean isCancelled()

Description copied from interface: java.util.concurrent.Future

Returns true if this task was cancelled before it completed normally.

Specified by:

isCancelled in interface Future<V>

Returns:

true if this task was cancelled before it completed

isDone

public boolean isDone()

Description copied from interface: java.util.concurrent.Future

Returns true if this task completed. Completion may be due to normal termination, an exception, or cancellation -- in all of these cases, this method will return true.

Specified by:

isDone in interface Future<V>

Returns:

true if this task completed

get

public V get()
      throws InterruptedException,
             ExecutionException

Description copied from interface: java.util.concurrent.Future

Waits if necessary for the computation to complete, and then retrieves its result.

Specified by:

get in interface Future<V>

Returns:

the computed result

Throws:

InterruptedException - if the current thread was interrupted while waiting

ExecutionException - if the computation threw an exception

get

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

Description copied from interface: java.util.concurrent.Future

Waits if necessary for at most the given time for the computation to complete, and then retrieves its result, if available.

Specified by:

get in interface Future<V>

Parameters:

timeout - the maximum time to wait

unit - the time unit of the timeout argument

Returns:

the computed result

Throws:

InterruptedException - if the current thread was interrupted while waiting

ExecutionException - if the computation threw an exception

TimeoutException - if the wait timed out

addListener

public void addListener(Runnable listener,
                        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.

Listeners cannot throw checked exceptions and should not throw RuntimeException unless their executors are prepared to handle it. Listeners that will execute in MoreExecutors.sameThreadExecutor() should take special care, since they may run during the call to addListener or during the call that sets the future's value.

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