io.spine.web.future

Class FutureObserver<T>

java.lang.Object

io.spine.web.future.FutureObserver<T>

All Implemented Interfaces:

io.grpc.stub.StreamObserver<T>

public final class FutureObserver<T>
extends java.lang.Object
implements io.grpc.stub.StreamObserver<T>

A stream observer which can provide a CompletableFuture view on the stream.

This implementation works only with the unary gRPC calls, i.e. FutureObserver.onNext(Object) cannot be called more then once.

Method Summary

Modifier and Type	Method and Description
static <T> FutureObserver<T>	create() Creates a new instance of FutureObserver.
void	onCompleted()
void	onError(java.lang.Throwable t)
void	onNext(T value)
java.util.concurrent.CompletableFuture<T>	toFuture() Retrieves the future view on this observer result.
static <T> FutureObserver<T>	withDefault(T defaultValue) Creates a new instance of FutureObserver with the given defaultValue.

Methods inherited from class java.lang.Object

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

Method Detail

withDefault

public static <T> FutureObserver<T> withDefault(T defaultValue)

Creates a new instance of FutureObserver with the given defaultValue.

The default value is used only if the FutureObserver.onNext(Object) method is never invoked and the stream is completed. In such case, the future view is completed with the given value.

Type Parameters:

T - the type of the observed stream

Parameters:

defaultValue - the default value to complete the future with

Returns:

new FutureObserver

create

public static <T> FutureObserver<T> create()

Creates a new instance of FutureObserver.

In case if the stream is completed with no value, the future view completed with null.

Type Parameters:

T - the type of the observed stream

Returns:

new FutureObserver

See Also:

FutureObserver.withDefault(Object)

onNext

public void onNext(T value)

Specified by:

onNext in interface io.grpc.stub.StreamObserver<T>

onError

public void onError(java.lang.Throwable t)

Specified by:

onError in interface io.grpc.stub.StreamObserver<T>

onCompleted

public void onCompleted()

Specified by:

onCompleted in interface io.grpc.stub.StreamObserver<T>

toFuture

public java.util.concurrent.CompletableFuture<T> toFuture()

Retrieves the future view on this observer result.

The future is completed when:

1. the element of the unary stream arrives via FutureObserver.onNext(Object);
2. the stream is completed with no data;
3. the stream is completed with an error; in this case, the future is obtruded with the error from the stream.

Returns:

the future view on this observer