public interface ResponseObserver<V>
Receives notifications from server-streaming calls.
The application is responsible for implementing the ResponseObserver
and passing it to
GAX, which then calls the observer with the messages for the application to receive them. The
methods might be called by different threads, but are guaranteed to happen sequentially. The
order of callbacks is guaranteed to be:
- exactly 1 onStart
- 0 or more on Response
- exactly 1 onError or onComplete
By default, the stream uses automatic flow control, where the next response will be delivered
as soon as the current one is processed by onResponse. A consumer can disable automatic flow
control by calling disableAutoInboundFlowControl()
in onStart
. After this, the
consumer must request responses by calling request()
.
Type Parameter
Name | Description |
V |
Methods
onComplete()
public abstract void onComplete()
Receives a notification of successful stream completion.
May only be called once, and if called, it must be the last method called. In particular, if
an exception is thrown by an implementation of onComplete
, no further calls to any
method are allowed.
onError(Throwable t)
public abstract void onError(Throwable t)
Receives a terminating error from the stream.
May only be called once, and if called, it must be the last method called. In particular, if
an exception is thrown by an implementation of onError
, no further calls to any method
are allowed.
Name | Description |
t | Throwable the error occurred on the stream |
onResponse(V response)
public abstract void onResponse(V response)
Receives a value from the stream.
Can be called many times but is never called after #onError(Throwable) or #onComplete() are called.
Clients may may receive 0 or more onResponse callbacks.
If an exception is thrown by an implementation the caller will terminate the stream by calling #onError(Throwable) with the caught exception as the cause.
Name | Description |
response | V the value passed to the stream |
onStart(StreamController controller)
public abstract void onStart(StreamController controller)
Called before the stream is started. This must be invoked synchronously on the same thread that called ServerStreamingCallable#call(Object, ResponseObserver, ApiCallContext)
Allows for disabling flow control and early stream termination via StreamController
.
Name | Description |
controller | StreamController The controller for the stream. |