org.apache.pivot.util.concurrent
Class Task<V>

java.lang.Object
  org.apache.pivot.util.concurrent.Task<V>

Type Parameters:

V - The type of the value returned by the operation. May be Void to indicate that the task does not return a value.

Direct Known Subclasses:

IOTask, TaskGroup, TaskSequence

public abstract class Task<V>
extends Object

Abstract base class for "tasks". A task is an asynchronous operation that may optionally return a value.

Field Summary

protected boolean	abort
static ExecutorService	DEFAULT_EXECUTOR_SERVICE
protected long	timeout

Constructor Summary

Task()

Task(ExecutorService executorService)

Method Summary

void	abort() Sets the abort flag for this task to true.
abstract V	execute() Synchronously executes the task.
void	execute(TaskListener<V> taskListenerArgument) Asynchronously executes the task.
void	execute(TaskListener<V> taskListenerArgument, ExecutorService executorServiceArgument) Asynchronously executes the task.
ExecutorService	getExecutorService() Returns the executor service used to execute this task.
Throwable	getFault() Returns the fault that occurred while executing the task.
V	getResult() Returns the result of executing the task.
long	getTimeout() Returns the timeout value for this task.
boolean	isPending() Returns the pending state of the task.
void	setTimeout(long timeout) Sets the timeout value for this task.

Methods inherited from class java.lang.Object

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

Field Detail

timeout

protected volatile long timeout

abort

protected volatile boolean abort

DEFAULT_EXECUTOR_SERVICE

public static final ExecutorService DEFAULT_EXECUTOR_SERVICE

Constructor Detail

Task

public Task()

Task

public Task(ExecutorService executorService)

Method Detail

execute

public abstract V execute()
                   throws TaskExecutionException

Synchronously executes the task.

Returns:

The result of the task's execution.

Throws:

TaskExecutionException - If an error occurs while executing the task.

execute

public void execute(TaskListener<V> taskListenerArgument)

Asynchronously executes the task. The caller is notified of the task's completion via the listener argument. Note that the listener will be notified on the task's worker thread, not on the thread that executed the task.

Parameters:

taskListenerArgument - The listener to be notified when the task completes.

execute

public void execute(TaskListener<V> taskListenerArgument,
                    ExecutorService executorServiceArgument)

Asynchronously executes the task. The caller is notified of the task's completion via the listener argument. Note that the listener will be notified on the task's worker thread, not on the thread that executed the task.

Parameters:

taskListenerArgument - The listener to be notified when the task completes.

executorServiceArgument - The service to submit the task to, overriding the Task's own ExecutorService.

getExecutorService

public ExecutorService getExecutorService()

Returns the executor service used to execute this task.

getResult

public V getResult()

Returns the result of executing the task.

Returns:

The task result, or null if the task is still executing or has failed. The result itself may also be null; callers should call isPending() and getFault() to distinguish between these cases.

getFault

public Throwable getFault()

Returns the fault that occurred while executing the task.

Returns:

The task fault, or null if the task is still executing or has succeeded. Callers should call isPending() to distinguish between these cases.

isPending

public boolean isPending()

Returns the pending state of the task.

Returns:

true if the task is awaiting execution or currently executing; false, otherwise.

getTimeout

public long getTimeout()

Returns the timeout value for this task.

See Also:

setTimeout(long)

setTimeout

public void setTimeout(long timeout)

Sets the timeout value for this task. It is the responsibility of the implementing class to respect this value.

Parameters:

timeout - The time by which the task must complete execution. If the timeout is exceeded, a TimeoutException will be thrown.

abort

public void abort()

Sets the abort flag for this task to true. It is the responsibility of the implementing class to respect this value and throw a AbortException.