Server sent events + Java with Spring MVC

Question

I am currently having a problem related to SSE and Windows XP. The source code below is currently working in every Chrome I tried except for Chrome in Windows XP (?) Not sure why. This is intended to be used for a control panel, where users must use Chrome. In other words, I don't care about IE, Firefox, etc.

The problem: Server side events works everywhere (Chrome) but not in Windows XP (Chrome). When I say it works, I mean that the message handler is called.

The code

• Javascript code

  if (!!window.EventSource) {
     console.log("Event source available");
     var source = new EventSource('/admin/systemalert');
  
     source.addEventListener('message', function(e) {
          console.log(e.data);
     });
  
     source.addEventListener('open', function(e) {
          console.log("Connection was opened.");
     }, false);
  
     source.addEventListener('error', function(e) {
          if (e.readyState == EventSource.CLOSED) {
              console.log("Connection was closed.");
          } else {
              console.log(e.readyState);    <-- in windows XP it prints Error here
          }
     }, false);
  } else {
          console.log("No SSE available");
  }
  

• Server side code

  @Controller
  @RequestMapping("/admin/**")
  public class AdminController {
  
          @RequestMapping("systemalert")
          public @ResponseBody String sendMessage(HttpServletResponse response) {
                  Random r = new Random();
                  response.setContentType("text/event-stream");
                  try {
                          Thread.sleep(10000);
                  } catch (InterruptedException e) {
                          e.printStackTrace();
                  }   
                  return "data:Testing 1,2,3" + r.nextInt() +"\n";
          }
  
  }
  

As stated in the code, the line console.log(e.readyState); prints "Error" when using Chrome in Windows XP. Any ideas? Anyone see anything wrong with the source code?

Thanks in advance. Agustin

Answer 1

Instead of implementing manually SSE, be aware that Spring Framework 4.2+ supports natively SSE. See this sample SSE enabled controller returning an SseEmitter.

Answer 2

For anyone with this problem, the problem was related to the new lines needed after the data. Basically, you need two lines and not one as I was using. That way it works everywhere.

Changing this:

return "data:Testing 1,2,3" + r.nextInt() +"\n";

To this:

return "data:Testing 1,2,3" + r.nextInt() +"\n\n";

Fixes the problem..