Package org.dellroad.stuff.vaadin24.util

Class SimpleTaskManager

java.lang.Object

org.dellroad.stuff.vaadin24.util.SimpleTaskManager

public class SimpleTaskManager
extends Object

A simplified asynchronous task manager.

This class wraps an underlying AsyncTaskManager and provides a simplified interface, where each task has its own result type, and success and error handlers.

All of the safety guarantees provided by AsyncTaskManager are provided by this class. As with AsyncTaskManager, only one task can be executing at a time, and starting a new task automatically cancels any previous task that is still outstanding.

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static interface	SimpleTaskManager.ThrowingRunnable

Field Summary

Fields

Modifier and Type	Field	Description
protected final AsyncTaskManager<Object>	taskManager

Constructor Summary

Constructors

Constructor	Description
SimpleTaskManager()	Default constructor.
SimpleTaskManager(Function<? super Runnable,? extends Future<?>> executor)	Constructor.

Method Summary

Modifier and Type	Method	Description
boolean	cancelTask()	Cancel current task, if any
VaadinSession	getVaadinSession()	Get the VaadinSession to which this instance is associated.
boolean	isBusy()	Determine whether there is an outstanding asynchronous task in progress.
void	setAsyncExecutor(Function<? super Runnable,? extends Future<?>> executor)	Configure the executor used for async tasks.
<T> void	startTask(Callable<? extends T> action, Consumer<? super T> onSuccess, Consumer<? super Throwable> onError)	Start a new task that returns some value.
void	startTask(SimpleTaskManager.ThrowingRunnable action, Runnable onSuccess, Consumer<? super Throwable> onError)	Start a new task that returns nothing.

Methods inherited from class java.lang.Object

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

Field Details

taskManager

protected final AsyncTaskManager<Object> taskManager

Constructor Details

SimpleTaskManager

public SimpleTaskManager()

Default constructor.

Caller must configure an async executor via setAsyncExecutor().

Throws:

IllegalStateException - if there is no VaadinSession associated with the current thread

SimpleTaskManager

public SimpleTaskManager(Function<? super Runnable,? extends Future<?>> executor)

Constructor.

Parameters:

executor - the executor used to execute async tasks, or null for none

Throws:

IllegalStateException - if there is no VaadinSession associated with the current thread

Method Details

getVaadinSession

public VaadinSession getVaadinSession()

Get the VaadinSession to which this instance is associated.

Returns:

this instance's VaadinSession, never null

setAsyncExecutor

public void setAsyncExecutor(Function<? super Runnable,? extends Future<?>> executor)

Configure the executor used for async tasks.

The executor must execute tasks with this instance's VaadinSession unlocked.

Note: when an in-progress task is canceled via cancelTask(), then Future.cancel() will be invoked on the Future returned by the executor.

Parameters:

executor - the thing that launches background tasks, or null for none

startTask

public <T> void startTask(Callable<? extends T> action,
 Consumer<? super T> onSuccess,
 Consumer<? super Throwable> onError)

Start a new task that returns some value.

Any previous task that is still executing will be cancelled.

Type Parameters:

T - task result type

Parameters:

action - the task to perform

onSuccess - callback when task is successful

onError - callback when task fails or is interrupted

Throws:

IllegalStateException - if the current thread is not associated with this instance's session

startTask

public void startTask(SimpleTaskManager.ThrowingRunnable action,
 Runnable onSuccess,
 Consumer<? super Throwable> onError)

Start a new task that returns nothing.

Any previous task that is still executing will be cancelled.

Parameters:

action - the task to perform

onSuccess - callback when task is successful

onError - callback when task fails or is interrupted

Throws:

IllegalStateException - if the current thread is not associated with this instance's session

isBusy

public boolean isBusy()

Determine whether there is an outstanding asynchronous task in progress.

Returns:

true if an asynchronous task is currently executing, otherwise false

Throws:

IllegalStateException - if the current thread is not associated with this instance's session

cancelTask

public boolean cancelTask()

Cancel current task, if any

Returns:

true if task was cancelled, otherwise false

Throws:

IllegalStateException - if the current thread is not associated with this instance's session