io.spine.grpc

Class StreamObservers

java.lang.Object

io.spine.grpc.StreamObservers

public class StreamObservers
extends java.lang.Object

A utility class for the routines related to gRPC StreamObserver instances.

Method Summary

Modifier and Type	Method and Description
static void	ack(io.grpc.stub.StreamObserver<io.spine.core.Response> responseObserver) A utility method which sends acknowledgement to the client via the responseObserver provided and completes the response.
static java.util.Optional<io.spine.base.Error>	fromStreamError(java.lang.Throwable throwable) Extracts a system error from the Throwable received on a client-side as a result of a failed gRPC call to server-side routines.
static <T> io.grpc.stub.StreamObserver<T>	noOpObserver() Creates a observer which does nothing upon the invocation of its callback methods.

Methods inherited from class java.lang.Object

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

Method Detail

noOpObserver

public static <T> io.grpc.stub.StreamObserver<T> noOpObserver()

Creates a observer which does nothing upon the invocation of its callback methods.

The callees which do not want to follow the responses should use this utility method to eliminate boilerplate code.

Returns:

an instance of StreamObserver which does nothing

ack

public static void ack(io.grpc.stub.StreamObserver<io.spine.core.Response> responseObserver)

A utility method which sends acknowledgement to the client via the responseObserver provided and completes the response.

fromStreamError

public static java.util.Optional<io.spine.base.Error> fromStreamError(java.lang.Throwable throwable)

Extracts a system error from the Throwable received on a client-side as a result of a failed gRPC call to server-side routines.

The Error is extracted from the trailer metadata of either StatusRuntimeException or StatusException only.

If any other type of Throwable is passed, Optional.empty() is returned.

Parameters:

throwable - the Throwable to extract an Error

Returns:

the extracted error or Optional.empty() if the extraction failed