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javajavascriptglassfishserver-sideserver-sent-events

Glassfish SSE not sending events successfully to the browser EventSource (Chrome latest)

I have created the following class running on the server side on Glassfish:

@Path("events")
public class SseResource {
  @GET
@Produces(SseFeature.SERVER_SENT_EVENTS)
public EventOutput getServerSentEvents() {
    final EventOutput eventOutput = new EventOutput();
//        new Thread(new Runnable() {
//            @Override
//            public void run() {
            try {
                for (int i = 0; i < 10; i++) {
                    // ... code that waits 1 second
                    final OutboundEvent.Builder eventBuilder
                    = new OutboundEvent.Builder();
                    eventBuilder.name("message-to-client");
                    eventBuilder.data(String.class,
                        "Hello world ");
                    final OutboundEvent event = eventBuilder.build();
                    eventOutput.write(event);


                }
            } catch (IOException e) {
                throw new RuntimeException(
                    "Error when writing the event.", e);
            } finally {
                try {
                    eventOutput.close();
                } catch (IOException ioClose) {
                    throw new RuntimeException(
                        "Error when closing the event output.", ioClose);
                }
            }
       // }
//        }).start();
    return eventOutput;
    }

}

I initialized the class from the resource here:

resources.add(WebServicesPublic.SseResource.class);

And then I created an HTML page that calls the server like so:

<html>
<body>
Time: <span id="foo"></span>

<br><br>
<button onclick="start()">Start</button>

<script type="text/javascript">
function start() {
    var eventSource = new EventSource("webresources/events");

    eventSource.addEventListener("message-to-client", msgClient, false);
    eventSource.onmessage = function(event) {
        document.getElementById('foo').innerHTML = event.data;
    };
}

function msgClient(event)
{
    document.getElementById('foo').innerHTML = event.data;
}
</script>
</body>
</html>

However, no events ever show up in the browser. I am running Glassfish 4. Anybody have any idea why it doesn't work? If I set a breakpoint in the server code, it does get hit. However, similar breakpoints in Chrome reveal no events received.

Solution

  • Does it work if you comment out eventBuilder.name("message-to-client"); ? Without that line events will go to the default message handler, which is called "message". (Event names should work, but get the default case working first.)

    Also, I don't think onmessage syntax works, so replace that line with:

    eventSource.addEventListener('message',function(event){
  document.getElementById('foo').innerHTML = event.data;
  },false);

    Also, make sure you have the developer tools (network tab) open under Chrome. Your connection is lasting 10 seconds, then the server-side is closing it. Chrome will wait about 3 seconds, the reconnect. So under the network tab, after a while, you should see rows start to stack up, each 10 seconds long. (And, if not, there should be a clue under the console.log.)