Package ratpack.core.sse

Class ServerSentEvents

  • All Implemented Interfaces:
    Renderable
    public class ServerSentEvents
extends Object
implements Renderable
    A renderable object for streaming server side events.

    A renderer for this type is implicitly provided by Ratpack core.

    Example usage: 

    
 import org.reactivestreams.Publisher;
 import ratpack.core.http.client.ReceivedResponse;
 import ratpack.core.sse.ServerSentEvent;
 import ratpack.core.sse.ServerSentEvents;
 import ratpack.test.embed.EmbeddedApp;

 import java.time.Duration;
 import java.util.Arrays;
 import java.util.Objects;

 import static ratpack.exec.stream.Streams.periodically;

 import static java.util.stream.Collectors.joining;

 import static org.junit.jupiter.api.Assertions.assertEquals;

 public class Example {
   public static void main(String[] args) throws Exception {
     EmbeddedApp.fromHandler(context -> {
       Publisher<ServerSentEvent> stream = periodically(context, Duration.ofMillis(5), i ->
         i < 5 ? ServerSentEvent.builder().id(i.toString()).event("counter").data("event " + i).build() : null
       );

       context.render(ServerSentEvents.builder().build(stream));
     }).test(httpClient -> {
       ReceivedResponse response = httpClient.get();
       assertEquals("text/event-stream;charset=UTF-8", response.getHeaders().get("Content-Type"));

       String expectedOutput = Arrays.asList(0, 1, 2, 3, 4)
         .stream()
         .map(i -> "id: " + i + "\nevent: counter\ndata: event " + i + "\n")
         .collect(joining("\n"))
         + "\n";

       assertEquals(expectedOutput, response.getBody().getText());
     });
   }
 }
    See Also:
    Wikipedia - Using server-sent events, MDN - Using server-sent events, builder()

    • Method Detail

      • builder

        public static ServerSentEventsBuilder builder()
        Creates a builder for an event stream.
        Returns:
        a builder for an event stream

      • render

        public void render​(Context context)
            throws Exception
        Render this object to the response.
        Specified by:
        render in interface Renderable
        Parameters:
        context - the request handling context
        Throws:
        Exception - any