com.luciad.concurrent

Class CancellationToken

java.lang.Object

com.luciad.concurrent.CancellationToken

All Implemented Interfaces:

AutoCloseable

public final class CancellationToken
extends Object
implements AutoCloseable

This class contains information on whether an operation has been canceled.

It is typically passed as a parameter to methods that perform an operation that could potentially take a long time. The method can either manually check whether the ongoing operation is canceled and react accordingly, or it can run a ICancellableTask on that token by calling CancellationToken#runTask, in which case the task will be notified as soon as the CancellationToken gets canceled.

For example: when raster data is added to the Map, the map's rendering backend will request raster tile data. When at the same time, this raster data is removed from the map, the rendering backend will want to stop requesting data as quickly as possible. For that purpose:

• it sends out CancellationToken instances with each raster data request
• it cancels the token at some point (for example when the raster layer is removed from the map)
• code that performs the actual raster data request (for example using a http request) then has the opportunity to check if the request has been canceled or not by either: a. calling the CancellationToken#isCanceled method periodically and take appropriate action to stop executing once it noticed the token is canceled, or b. wrapping the Http request in an ICancellableTask and calling CancellationToken#runTask, so that the request can be aborted (by calling the appropriate method on the request class) as soon as the token gets canceled.

It is not mandatory to use the CancellationToken, but it is recommended. Not doing so may block operations for a longer time, such a removing a layer or closing the map.

Method Summary

Modifier and Type	Method and Description
void	close()
protected void	finalize()
boolean	isCanceled() Returns whether the cancellation token has the status canceled.
void	runTask(ICancellableTask task) Runs a cancellable task that will be notified when the CancellationToken is canceled.

Methods inherited from class java.lang.Object

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

Method Detail

finalize

protected void finalize()

Overrides:

finalize in class Object

close

public void close()

Specified by:

close in interface AutoCloseable

isCanceled

public boolean isCanceled()

Returns whether the cancellation token has the status canceled.

This method is typically used by time-consuming operations. These operations are supposed to regularly check the status of this method. When it returns 'true', the operation can decide to stop executing.

Returns:

the status of the cancellation token.

runTask

public void runTask(@NotNull
                    ICancellableTask task)

Runs a cancellable task that will be notified when the CancellationToken is canceled.

This method synchronously calls ICancellableTask#run() on the provided task. If the token is canceled by another thread while runTask is executing, ICancellableTask#cancel() will be called on that other thread.

Parameters:

task - the cancellable task to be executed