text/event-stream render in grails from scratch(without plugin) - servlets

Question

To use push method , we use the famous JS object EventSource :
This is the client part which is easy to develop it :
var eventSource = new EventSource("controller/action");
eventSource.onmessage = function(event) {
document.getElementById('foo').innerHTML = event.data;
};
However , i get difficulty to configure push method in server part(Grails) .
When , i peek in JEE app developped by Servlets , i can see that the server part is as following :
http://viralpatel.net/blogs/html5-server-sent-events-java-servlets-example/
public class TestServlet extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
//content type must be set to text/event-stream
response.setContentType("text/event-stream");
//encoding must be set to UTF-8
response.setCharacterEncoding("UTF-8");
PrintWriter writer = response.getWriter();
for(int i=0; i<10; i++) {
writer.write("data: "+ System.currentTimeMillis() +"\n\n");
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
writer.close();
}
}
To convert this servlet to action controller :
def push(){
render(contentType:'text/event-stream',characterEncoding:'UTF-8'){
[dt:"data: "+ System.currentTimeMillis() +"\n\n"]
}
}
and in client part :
var eventSource = new EventSource(baseURL+"external/push");
eventSource.onmessage=function(e){
console.log(e.data.dt);
}
Unfortunately, i don't get any result at console .

Answer 1

I'm not sure if the render method will handle 'text/event-stream' correctly, but you have direct access to the response object in the action:
def push() {
//content type must be set to text/event-stream
response.setContentType("text/event-stream");
//encoding must be set to UTF-8
response.setCharacterEncoding("UTF-8");
for(int i=0; i<10; i++) {
response.outputStream.write("data: "+ System.currentTimeMillis() +"\n\n");
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
response.outputStream.flush()
}

Answer 2

def push = {
response.setContentType("text/event-stream");
for(def i=0;i<10;i++) {
render("data $i: ${System.currentTimeMillis()}\n");
sleep(1000)
}
}