Package org.scijava.task

Class DefaultTask

java.lang.Object

org.scijava.task.DefaultTask

All Implemented Interfaces:

Cancelable, Named, Task

public class DefaultTask
extends Object
implements Task

Default implementation of Task. Throughout the task (or job), Task.setProgressValue(long) can be called to inform how the job is progressing.

Asynchronous case: A job (runnable) is sent for execution to the linked ThreadService. It reports status updates via the linked EventService. A TaskEvent is sent before the job is started and when finished. In the asynchronous case, upon task cancellation (Cancelable.cancel(String) call), the runnable associated to the ThreadService is attempted to be stopped by calling Future.cancel(boolean). This default behaviour can be supplemented by an additional custom callback which can be set in Task.setCancelCallBack(Runnable).

Synchronous case: A job that reports its status in between calls of Task.start(), and Task.finish(). It also reports its status via the linked EventService. Start and finish calls allow publishing proper TaskEvent to subscribers (with the EventService). Upon cancellation of a synchronous task, it is the responsibility of the synchronous task to handle its own cancellation through a custom callback which can be set via Task.setCancelCallBack(Runnable).

Author:

Curtis Rueden, Nicolas Chiaruttini

Constructor Summary

Constructors

Constructor	Description
DefaultTask(ThreadService threadService, EventService eventService)	Creates a new task.

Method Summary

Modifier and Type	Method	Description
void	cancel(String reason)	Cancels the operation execution, with the given reason for doing so.
void	finish()	reports that the task is finished - synchronous job
Runnable	getCancelCallBack()	Returns the current cancel callback runnable, This can be used to concatenate callbacks in order, for instance, to ask for a user confirmation before cancelling the task
String	getCancelReason()	Gets a message describing why the operation was canceled.
String	getName()	Gets the name of the object.
long	getProgressMaximum()	Gets the number of steps the task performs in total.
long	getProgressValue()	Gets the step the task is currently performing.
String	getStatusMessage()	Gets a status message describing what the task is currently doing.
boolean	isCanceled()	Gets whether the operation has been canceled.
boolean	isDone()	Checks whether the task has completed.
void	run(Runnable r)	Starts running the task - asynchronous job
void	setCancelCallBack(Runnable r)	If the task is cancelled (external call to Cancelable.cancel(String)), the input runnable argument should be executed by task implementors.
void	setName(String name)	Sets the name of the object.
void	setProgressMaximum(long max)	Sets the total number of steps.
void	setProgressValue(long step)	Sets the current step.
void	setStatusMessage(String status)	Sets the status message.
void	start()	reports that the task is started - synchronous job
void	waitFor()	Waits for the task to complete - asynchronous job

Methods inherited from class java.lang.Object

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

Constructor Detail

DefaultTask

public DefaultTask(ThreadService threadService,
                   EventService eventService)

Creates a new task.

Parameters:

threadService - Service to use for launching the task in its own thread. Required.

eventService - Service to use for reporting status updates as TaskEvents. May be null, in which case no events are reported.

Method Detail

run

public void run(Runnable r)

Description copied from interface: Task

Starts running the task - asynchronous job

Specified by:

run in interface Task

waitFor

public void waitFor()
             throws InterruptedException,
                    ExecutionException

Description copied from interface: Task

Waits for the task to complete - asynchronous job

Specified by:

waitFor in interface Task

Throws:

InterruptedException - if the task is interrupted.

ExecutionException - if the task throws an exception while running.

start

public void start()

Description copied from interface: Task

reports that the task is started - synchronous job

Specified by:

start in interface Task

finish

public void finish()

Description copied from interface: Task

reports that the task is finished - synchronous job

Specified by:

finish in interface Task

isDone

public boolean isDone()

Description copied from interface: Task

Checks whether the task has completed.

Specified by:

isDone in interface Task

getStatusMessage

public String getStatusMessage()

Description copied from interface: Task

Gets a status message describing what the task is currently doing.

Specified by:

getStatusMessage in interface Task

getProgressValue

public long getProgressValue()

Description copied from interface: Task

Gets the step the task is currently performing.

Specified by:

getProgressValue in interface Task

Returns:

A value between 0 and Task.getProgressMaximum() inclusive.

See Also:

Task.getProgressMaximum()

getProgressMaximum

public long getProgressMaximum()

Description copied from interface: Task

Gets the number of steps the task performs in total.

Specified by:

getProgressMaximum in interface Task

Returns:

Total number of steps the task will perform, or 0 if unknown.

See Also:

Task.getProgressValue()

setStatusMessage

public void setStatusMessage(String status)

Description copied from interface: Task

Sets the status message. Called by task implementors.

Specified by:

setStatusMessage in interface Task

Parameters:

status - The message to set.

See Also:

Task.getStatusMessage()

setProgressValue

public void setProgressValue(long step)

Description copied from interface: Task

Sets the current step. Called by task implementors.

Specified by:

setProgressValue in interface Task

Parameters:

step - The step vaule to set.

See Also:

Task.getProgressValue()

setProgressMaximum

public void setProgressMaximum(long max)

Description copied from interface: Task

Sets the total number of steps. Called by task implementors.

Specified by:

setProgressMaximum in interface Task

Parameters:

max - The step count to set.

See Also:

Task.getProgressMaximum()

isCanceled

public boolean isCanceled()

Description copied from interface: Cancelable

Gets whether the operation has been canceled.

Specified by:

isCanceled in interface Cancelable

cancel

public void cancel(String reason)

Description copied from interface: Cancelable

Cancels the operation execution, with the given reason for doing so.

This method merely sets the operation status to canceled; it cannot necessarily stop the operation itself. That is, it is the responsibility of each individual operation to check Cancelable.isCanceled() in a timely manner during execution, and stop doing whatever it is doing if the flag has been tripped.

Specified by:

cancel in interface Cancelable

Parameters:

reason - A message describing why the operation is being canceled.

setCancelCallBack

public void setCancelCallBack(Runnable r)

Description copied from interface: Task

If the task is cancelled (external call to Cancelable.cancel(String)), the input runnable argument should be executed by task implementors.

Specified by:

setCancelCallBack in interface Task

Parameters:

r - : should be executed if this task is cancelled through Cancelable.cancel(String)

getCancelCallBack

public Runnable getCancelCallBack()

Description copied from interface: Task

Returns the current cancel callback runnable, This can be used to concatenate callbacks in order, for instance, to ask for a user confirmation before cancelling the task

Specified by:

getCancelCallBack in interface Task

getCancelReason

public String getCancelReason()

Description copied from interface: Cancelable

Gets a message describing why the operation was canceled.

Specified by:

getCancelReason in interface Cancelable

Returns:

The reason for cancelation, which may be null if no reason was given, or if the operation was not in fact canceled.

getName

public String getName()

Description copied from interface: Named

Gets the name of the object.

Specified by:

getName in interface Named

setName

public void setName(String name)

Description copied from interface: Named

Sets the name of the object.

Specified by:

setName in interface Named