[jax-rs-spec users] Re: Server-Sent Events API proposal

From: Markus KARG <>
Date: Mon, 30 Jan 2017 23:12:40 +0100

I was sick last weekend, so I will take a look into this API later this week. Sorry for the delay.



From: Pavel Bucek []
Sent: Freitag, 27. Januar 2017 08:56
Subject: Re: Server-Sent Events API proposal


No commends/feedback?

I understand that the change is not a small one - feel free to ask if you need to have something explained in more detail.

Please let me know if someone is planning to look into this topic. Ideally by the end of this week (start of the day Monday, CET). If there are no comments, we might need to move it forward even without any other input, but I don't really want to do that..

Thanks and regards,

On 24/01/2017 20:54, Pavel Bucek wrote:

Dear experts,

please allow me to bring up another addition planned to be included in JAX-RS 2.1: Support for Server Sent Events.

The API was introduced a while back [1], but we did incorporate some changes, mostly alignments with Java SE 8 and another one, slightly more controversial - alignment with Java SE 9 Flow API.

Why we should use Flow API? We want to make the transition to Java 9 as smooth as possible. Please note that today, the JAX-RS sources do contain Flow class (1:1 copy from Java SE 9), but that is NOT a final state. We want to work with it as much as possible, but we will minimize and clean up the code before final release. How? Consider following example:

public interface SseBroadcaster extends AutoCloseable, Flow.Publisher<OutboundSseEvent> {

could be modified to

public interface SseBroadcaster extends AutoCloseable {
    void subscribe(SseSubscriber<? super OutboundSseEvent> subscriber);

I hope you will like the attempt to be "forward-compatible", but I assume that this proposal alone will bring some opinions - please share them! Last note: currently, the Flow API is used only in SSE. We plan to use it heavily in Non-blocking I/O. If you think there are other areas where we can take advantage of Subscriber/Publisher methods, please let us know.

Let me get back to the SSE API.

Very brief description of the API is on the wiki [2], I will expand that once we'll have some feedback.

The proposal contains support for server and client side. All classes are in the package [3]. There is no added class from the last proposal, but there are some changes:

- [server] SseBroadcaster extends Publisher<OutboundSseEvent>
- [server] replaced SseBroadcaster.Listener by SseBroadcaster#onException and SseBroadcaster#onClose
- [server] SseEventOutput extends Subscriber<OutboundSseEvent>
- [client] SseEventSource extends Publisher<InboundSseEvent>

Corresponding commit [4] looks like a bigger one, but most of it is renaming based on introduced interfaces, the core of the change is relatively small.

I look forward to your comments and suggestions.

I don't want to prolong this already too long email - please let me know if there are some areas which I should describe in more detail.

Thanks and regards,
Pavel & Santiago