Jersey itself supports SSE for years, now it is standardized as a part of JAXRS 2.1.
A simple SSE example.
@Path("events")
@RequestScoped
public class SseResource {
@GET
@Produces(MediaType.SERVER_SENT_EVENTS)
public void eventStream(@Context Sse sse, @Context SseEventSink eventSink) {
// Resource method is invoked when a client subscribes to an event stream.
// That implies that sending events will most likely happen from different
// context - thread / event handler / etc, so common implementation of the
// resource method will store the eventSink instance and the application
// logic will retrieve it when an event should be emitted to the client.
// sending events:
eventSink.send(sse.newEvent("event1"));
}
}
Notice, you should declare @Produces value as text/event-stream( via MediaType.SERVER_SENT_EVENTS). SseEventSink should be request aware, Sse is helpful to build event payloads etc.
An example of SSE client.
WebTarget target = ClientBuilder.newClient().target("http://localhost:8080/jaxrs-sse/rest/events");
try (SseEventSource eventSource = SseEventSource.target(target).build()) {
// EventSource#register(Consumer<InboundSseEvent>)
// Registered event handler will print the received message.
eventSource.register(System.out::println);
// Subscribe to the event stream.
eventSource.open();
// Consume events for just 500 ms
Thread.sleep(500);
} catch (InterruptedException e) {
e.printStackTrace();
}
The following is an example demonstrates the usage of SseBroadcaster, which allow you send messages to all registered clients.
@Path("broadcastEvents")
@Singleton
public class BroadcastResource {
@Context
private Sse sse;
private volatile SseBroadcaster sseBroadcaster;
@PostConstruct
public void init() {
this.sseBroadcaster = sse.newBroadcaster();
}
@GET
//@Path("register")
@Produces(MediaType.SERVER_SENT_EVENTS)
public void register(@Context SseEventSink eventSink) {
eventSink.send(sse.newEvent("welcome!"));
sseBroadcaster.register(eventSink);
}
@POST
//@Path("broadcast")
@Consumes(MediaType.APPLICATION_FORM_URLENCODED)
public void broadcast(@FormParam("event") String event) {
sseBroadcaster.broadcast(sse.newEvent(event));
}
public void eventStreamCdi(@Observes Message msg) {
sseBroadcaster.broadcast(
sse.newEventBuilder()
.mediaType(MediaType.APPLICATION_JSON_TYPE)
.id(UUID.randomUUID().toString())
.name("message from cdi")
.data(msg)
.build()
);
}
}