io.vertx.core

Interface Promise<T>

All Superinterfaces:

Handler<AsyncResult<T>>

All Known Subinterfaces:

ApolloWSConnectionInitEvent, BaseBridgeEvent, BridgeEvent, BridgeEvent, ConnectionInitEvent

public interface Promise<T>
extends Handler<AsyncResult<T>>

Represents the writable side of an action that may, or may not, have occurred yet.

The future() method returns the Future associated with a promise, the future can be used for getting notified of the promise completion and retrieve its value.

A promise extends Handler<AsyncResult<T>> so it can be used as a callback.

Author:

Julien Viet

Method Summary

Modifier and Type	Method and Description
default void	complete() Calls complete(null)
default void	complete(T result) Set the result.
default void	fail(String message) Calls fail(Throwable) with the message.
default void	fail(Throwable cause) Set the failure.
Future<T>	future()
default void	handle(AsyncResult<T> asyncResult) Succeed or fail this promise with the AsyncResult event.
static <T> Promise<T>	promise() Create a promise that hasn't completed yet
default boolean	tryComplete() Calls tryComplete(null).
boolean	tryComplete(T result) Like complete(Object) but returns false when the promise is already completed instead of throwing an IllegalStateException, it returns true otherwise.
default boolean	tryFail(String message) Calls fail(Throwable) with the message.
boolean	tryFail(Throwable cause) Like fail(Throwable) but returns false when the promise is already completed instead of throwing an IllegalStateException, it returns true otherwise.

Method Detail

promise

static <T> Promise<T> promise()

Create a promise that hasn't completed yet

Type Parameters:

T - the result type

Returns:

the promise

handle

default void handle(AsyncResult<T> asyncResult)

Succeed or fail this promise with the AsyncResult event.

Specified by:

handle in interface Handler<AsyncResult<T>>

Parameters:

asyncResult - the async result to handle

complete

default void complete(T result)

Set the result. Any handler will be called, if there is one, and the promise will be marked as completed.

Any handler set on the associated promise will be called.

Parameters:

result - the result

Throws:

IllegalStateException - when the promise is already completed

complete

default void complete()

Calls complete(null)

Throws:

IllegalStateException - when the promise is already completed

fail

default void fail(Throwable cause)

Set the failure. Any handler will be called, if there is one, and the future will be marked as completed.

Parameters:

cause - the failure cause

Throws:

IllegalStateException - when the promise is already completed

fail

default void fail(String message)

Calls fail(Throwable) with the message.

Parameters:

message - the failure message

Throws:

IllegalStateException - when the promise is already completed

tryComplete

boolean tryComplete(T result)

Like complete(Object) but returns false when the promise is already completed instead of throwing an IllegalStateException, it returns true otherwise.

Parameters:

result - the result

Returns:

false when the future is already completed

tryComplete

default boolean tryComplete()

Calls tryComplete(null).

Returns:

false when the future is already completed

tryFail

boolean tryFail(Throwable cause)

Like fail(Throwable) but returns false when the promise is already completed instead of throwing an IllegalStateException, it returns true otherwise.

Parameters:

cause - the failure cause

Returns:

false when the future is already completed

tryFail

default boolean tryFail(String message)

Calls fail(Throwable) with the message.

Parameters:

message - the failure message

Returns:

false when the future is already completed

future

Future<T> future()

Returns:

the Future associated with this promise, it can be used to be aware of the promise completion