users@jax-rs-spec.java.net

[jax-rs-spec users] Re: Minor SSE API changes

From: Pavel Bucek <pavel.bucek_at_oracle.com>
Date: Wed, 29 Mar 2017 14:07:52 +0200

Ah, I did not mean it like anything is going away - Sse#newBroadcaster
will stay, only two method could be added to ease "storing" and
retrieving the broadcasters.

It's meant as an addition, existing Sse methods will stay as they are
for now.

Regards,
Pavel


On 29/03/2017 13:28, Sergey Beryozkin wrote:
> Hi Pavel
>
> In your original example you had a non static SseBroadcaster created
> from Sse.newBroadcaster. Yes, I recall it was also a singleton in your
> example, but as I said, I don't understand what difference does it
> make, @Context also works well for per-request resources.
>
> Is the actual problem is that SseBroadcasters are rather be 'static'
> in nature ?
> May be we can have sse.newBroadcaster() but add
> sse.getBroadcaster(Class) ?
>
> Cheers, Sergey
>
>
> On 29/03/17 12:14, Pavel Bucek wrote:
>>
>> Hi Sergey,
>>
>> that is still true, but with these new methods on Sse "context", we'd
>> remove the need for having JAX-RS Resources as singleton, since the
>> "store" on the Sse would be application-scoped.
>>
>> (let me add a code example to be extra sure we are on the same page)
>>
>> current state:
>>
>> (the synchronization could be done in a better way, please take it
>> only as an example)
>>
>> @Path("server-sent-events")
>> public class ServerSentEventsResource {
>>
>> private final Ssesse;
>>
>> private static SseBroadcasterbroadcaster;// ... per-class broadcaster storage public ServerSentEventsResource(@Context Sse sse) {
>> this.sse = sse;
>> }
>>
>> private static synchronized SseBroadcaster getBroadcaster(Sse sse) {
>> if (broadcaster ==null) {
>> broadcaster = sse.newBroadcaster();
>> }
>>
>> return broadcaster;
>> }
>>
>> @POST public void sendMessage(final String message)throws IOException {
>> getBroadcaster(sse).broadcast(sse.newEvent(message));
>> }
>>
>> // ... }
>>
>> future?:
>>
>> @Path("server-sent-events")
>> public class ServerSentEventsResource {
>>
>> private final Ssesse;
>>
>> public ServerSentEventsResource(@Context Sse sse) {
>> this.sse = sse;
>> }
>>
>> @POST public void sendMessage(final String message)throws IOException {
>> sse.getBroadcaster(this.getClass()).broadcast(sse.newEvent(message));
>> }
>>
>> // ... }
>>
>> Thanks,
>> Pavel
>>
>>
>> On 29/03/2017 12:34, Sergey Beryozkin wrote:
>>> HI Pavel
>>>
>>> That works for us. Recall that you said that 'Sse' object can be
>>> injected with a JAX-RS @Context and
>>> assuming the service resource is called DemoResource this works for
>>> either per-request or singleton,
>>> public class DemoResource {
>>> public DemoResource(@Context Sse sse) {}
>>> }
>>>
>>> For ex, if DemoService is per-request then the following works right
>>> now:
>>>
>>> public DemoResource(@Context Application app) {}
>>>
>>> Both 'contexts' are very much similar in that both are effectively
>>> the non-request specific factories
>>>
>>> Thanks, Sergey
>>>
>>> On 29/03/17 11:10, Pavel Bucek wrote:
>>>> Dear experts,
>>>>
>>>> we did a couple of changes in SSE API:
>>>>
>>>> - removed SseEventSource.Builder#named(...)
>>>>
>>>> the intention was to name threads used by the event source, but in
>>>> the light of future change, which should introduce "common"
>>>> per-client thread pool(s) for async operation, this won't be
>>>> feasible to have there (since it would require creating another
>>>> threadpool per SseEventSource instance)
>>>>
>>>> - SseEventSource now implements Flow.Source<InboundSseEvent>
>>>>
>>>> seems like we'd need to have some form of Publisher and Subscriber,
>>>> currently named as Source and Sink in the API. The main reason
>>>> would be integration with other frameworks - without it, it would
>>>> be harder to do without a good reason.
>>>>
>>>>
>>>> Also, during the implementation and rewriting "old" Jersey
>>>> examples, one difficulty was discovered. It used to be possible to
>>>> create a broadcaster statically, which simulates "per resource
>>>> class" scope. The problem is that currently the only way how to
>>>> create a new SseBroadcaster is injecting Sse object. But that is
>>>> not available during static initialization and since JAX-RS
>>>> resources are by default request-scoped, storing the SseBroadcaster
>>>> instances might be a challenge for some users.
>>>>
>>>> Does anyone see the same issue as we do?
>>>>
>>>> Would someone object if we add methods like
>>>>
>>>> Sse#getBroadcaster(String)
>>>> Sse#getBroadcaster(Class<?>)
>>>>
>>>> which would serve as a storage for broadcasters? (semantically it
>>>> could be "get-or-create", passed String or Class would serve as a
>>>> key).
>>>>
>>>> Thanks and regards,
>>>> Pavel
>>>
>>>
>>
>