[jax-rs-spec users] High Level API for SSE support

From: Markus KARG <>
Date: Fri, 3 Feb 2017 00:22:11 +0100



Oracle's current SSE API proposal clearly is a good API for SSE. The
question is, whether it really fulfils what application developers expert
from JAX-RS in particular.


There might be programmers that don't like to explicitly learn a new (and
rather complex) set of classes and methods just to get the additional
benefit of update notifications, and that the style of the SSE API does not
very well fit into the style of JAX-RS. SSE API is completely algorithmic,
while server-side JAX-RS is mostly declarative. I could imagine that some
programmers would love to get a high-level SSE support in JAX-RS that more
looks like "SSE inside JAX-RS" and less like a standalone SSE API.


To illustrate, let me give an example. Think of a simple CRUD application
that works pretty well in JAX-RS 2.0 already (@POST / @GET / @PUT /
@DELETE). Now the developers decide that once data is updated (PUT) or
deleted (DELETE), the client shall be notified about that immediately using
SSE technology with minimal additional code. But the amount of additional
code lines with the new SSE API is really heavy and clutters the previously
clean application with lots of SSE special code.


So I wonder whether it might be beneficial to provide some high-level API
that simplifies this use case?


For example, it could look like this (simplified for illustration purposes):


@SSE public class MyResource {


  @GET @SseInit public void notifications() {};


  @POST public void create() {.};


  @GET @Path("{id}") public MyObject read() {.};


  @PUT @SseNotify public void update() {.};


  @DELETE @SseNotify public void delete() {.};




The idea would be the SSE API as outlined by Oracle is used under the hood
by the JAX-RS container. Once a requests to get SSE notifications by calling
the @SseInit-annotated GETter, the JAX-RS container sets up an implied SSE
subscription for that client with this resource. Whenever the JAX-RS
container leaves the body of @SseNotify-annotated methods, it pushes
notifications to that subscriptions (the messages as synthetically built
from the HTTP method and the URL, so the client knows what the message


This is not as far as flexible as Oracle's full-blown SSE API, but it is
only intended as sugar ontop for simple but frequent use cases.