com.aldebaran.qi

Class Promise<T>

java.lang.Object

com.aldebaran.qi.Promise<T>

Type Parameters:

T - The type of the result

public class Promise<T>
extends Object

Promise is a writable, single assignment container which sets the value of the Future.

Promise and Future are two complementary concepts. They are designed to synchronize data between multiples threads. The Future holds the result of an asynchronous computation, from which you can retrieve the value of the result; the Promise sets the value of this computation, which resolves the associated Future.

For promises that don't need a value and are just used to ensure correct ordering of asynchronous operations, the common pattern to use is Void as a generic type.

Warning: After a call of setValue(Object), setError(String) or setCancelled(), it is illegal to call any of them

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static interface	Promise.CancelRequestCallback<T> An implementation of this interface can be connected to a Promise in order to be called when the Promise receives a cancel request.

Constructor Summary

Constructors

Constructor and Description
Promise()
Promise(FutureCallbackType type) Create a new promise

Method Summary

Methods

Modifier and Type	Method and Description
void	connectFromFuture(Future<T> future)
protected void	finalize() Called by garbage collector when object destroy. Override to free the reference in JNI.
Future<T>	getFuture()
void	setCancelled() Set the promise on cancel state and transfer the information to linked future. Warning after call this method, call setValue(Object), setError(String) or setCancelled() will cause an IllegalStateException
void	setError(String errorMessage) Set the promise on error state and transfer the information to linked future. Warning after call this method, call setValue(Object), setError(String) or setCancelled() will cause an IllegalStateException
void	setOnCancel(Promise.CancelRequestCallback<T> callback) Sets a cancel callback.
void	setValue(T value) Set the promise value and transfer the information to linked future. Warning after call this method, call setValue(Object), setError(String) or setCancelled() will cause an IllegalStateException

Methods inherited from class java.lang.Object

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

Constructor Detail

Promise

public Promise(FutureCallbackType type)

Create a new promise

Parameters:

type - Callback type

Promise

public Promise()

Method Detail

getFuture

public Future<T> getFuture()

setValue

public void setValue(T value)

Set the promise value and transfer the information to linked future.
Warning after call this method, call setValue(Object), setError(String) or setCancelled() will cause an IllegalStateException

Parameters:

value - Promise value

Throws:

IllegalStateException - If setValue(Object), setError(String) or setCancelled() was previously called

setError

public void setError(String errorMessage)

Set the promise on error state and transfer the information to linked future.
Warning after call this method, call setValue(Object), setError(String) or setCancelled() will cause an IllegalStateException

Parameters:

errorMessage - Error message

Throws:

IllegalStateException - If setValue(Object), setError(String) or setCancelled() was previously called

setCancelled

public void setCancelled()

Set the promise on cancel state and transfer the information to linked future.
Warning after call this method, call setValue(Object), setError(String) or setCancelled() will cause an IllegalStateException

Throws:

IllegalStateException - If setValue(Object), setError(String) or setCancelled() was previously called

setOnCancel

public void setOnCancel(Promise.CancelRequestCallback<T> callback)

Sets a cancel callback. When cancellation is requested, the set callback is immediately called.

Parameters:

callback - The callback to call

connectFromFuture

public void connectFromFuture(Future<T> future)

finalize

protected void finalize()
                 throws Throwable

Called by garbage collector when object destroy.
Override to free the reference in JNI.

Overrides:

finalize in class Object

Throws:

Throwable - On destruction issue.