Added EventSource example

app/controllers/ExamplesController.scala

@@ -3,7 +3,8 @@ package controllers
 import javax.inject._
 
 import akka.stream.{Materializer, OverflowStrategy, ThrottleMode}
-import akka.stream.scaladsl.{Flow, Sink, Source, SourceQueueWithComplete}
+import akka.stream.scaladsl.{Flow, Keep, Sink, Source, SourceQueueWithComplete}
+import play.api.libs.EventSource
 
 import scala.concurrent.duration._
 import scala.util.Random
@@ -150,6 +151,24 @@ class ExamplesController @Inject()(cc: ControllerComponents)(implicit ec: Execut
 
   }
 
+  /**
+    * An example using EventSource (server sent events).
+    * @return
+    */
+  def eventSource() = Action { request =>
+    // The source "will be" a queue we can push to. But this doesn't create the queue yet
+    val s = Source.queue[String](50, OverflowStrategy.backpressure)
+
+    // Connect the source via the EventSource's flow.
+    val stream = s.viaMat(EventSource.flow[String]) {
+      // It calls us back when the queue has been created!
+      case (queue, m) =>
+        listeners.add(queue)
+        m
+    }
+
+    Ok.chunked(stream).as("text/event-stream")
+  }
 
 
 }

conf/routes

@@ -14,6 +14,8 @@ GET     /example/game               controllers.ExamplesController.game(id:Optio
 GET     /example/socket             controllers.ExamplesController.websocket()
 GET     /example/time               controllers.ExamplesController.websocketWithHelper()
 
+GET     /example/eventsource        controllers.ExamplesController.eventSource()
+
 
 # Map static resources from the /public folder to the /assets URL path
 GET     /assets/*file               controllers.Assets.versioned(path="/public", file: Asset)