EventSource onmessage() is not working where onopen() and onerror() works properly?

check my code below, Here I have added three alert messages to each event type, but in this code source.onopen()[alert: readyState: 1] and source.onerror()[alert: readyState: 0] works properly but in case of onmessage() it is not executed.`

       if(typeof(EventSource) !== "undefined") {
           var source = new EventSource('clinic/get');
           source.onopen = function(){
             alert('connection is opened.'+source.readyState);  
           };

           source.onerror = function(){
               alert('error: '+source.readyState);
           };

           source.onmessage = function(datalist){

               alert("message: "+datalist.data);
           };

        } else {
            document.getElementById("clinic-dtls").innerHTML = "Sorry, your browser does not support server-sent events...";
        }`

check the code below for the server side

Random random = new Random();
        response.setContentType("text/event-stream");
        response.setCharacterEncoding("UTF-8");
        System.out.println("clinic/get got hit");

        try {
            Writer out = response.getWriter();
            out.write("data: welcome data"+random);
            out.flush();
            out.close();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

I am using STS(Spring tool Suits), I am wondering, when I am using ctrl+space on EventSource (source) object, in the options it only shows onopen() and onerror(), where is the onmessage().

I will be highly appreciate, if I’d get any response. –Thanks

Answer

Solved it !!!

There is no issue with code, the actual issue is when I am writing response to client my response message should look like as below.

PrintWriter out = response.write("data: message"+value+"nn");
out.flush(); //don't forget to flush

In my code I was missing the last part “nn” in response object so source.onmessage(datalist) in javascript didn’t get hit.

Crazy coding..