server sent events using servlets

Question

I am using a servlet as my server to send updates to my jsp client(Using HTML5 SSE). This is my jsp code

<script type="text/javascript">
 if(typeof(EventSource)!=="undefined")
 {
 var source=new EventSource("server");
 source.onmessage=function(event)
 {
 document.getElementById("news1").innerHTML+=event.data + "<br />";
 };
 }
 else
 {
 document.getElementById("news1").innerHTML="Sorry, your browser does not support server-sent events...";
 }
 </script>

This is my servlet doGet method.

response.setContentType("text/event-stream"); 
 PrintWriter out = response.getWriter(); 
 int messagesSent = 0; 
 out.print("data: {" + messagesSent++ + "}\n\n"); 
 out.flush(); 
 out.close();

This is working fine and server is sending updates approximately in every 3 seconds by default. I want to change this to every 10 minutes. Is it possible? If yes,How?

• JB Nizet: Have you tried not closing the stream at server-side, and sending a message to this stream every 10 minutes?

Answer 1

In your response you need to send retry: with the timeout in milliseconds

Therefore you doGet should look like this....

response.setContentType("text/event-stream"); 
PrintWriter out = response.getWriter(); 
int messagesSent = 0; 
out.print("retry: 600000\n"); //set the timeout to 10 mins in milliseconds
out.print("data: {" + messagesSent++ + "}\n\n"); 
out.flush(); 
out.close();

See HTML5Rocks.com for more info an the EventSource object.

Answer 2

The above solution does not work with Chrome because of the ContentType.

Chrome expects this:

response.setContentType("text/event-stream;charset=UTF-8");

Find a sample googling "milestonenext HTML5 Server-Sent Events Sample with Java Servlet as Event Server"