Question

I have a jetty server running which responds to get requests. If I make the request using a browser:
localhost:8080/sp or 127.0.0.1:8080/sp
I get the correct data back.

public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    response.setContentType("application/json");
response.setStatus(HttpServletResponse.SC_OK);

PrintWriter out = response.getWriter();
out.println("{foobar: true"});
response.flushBuffer();
out.flush();
out.close();
}

but when I try to access the same url using JS the response body is empty.
I’ve tried serving the webpage using both the OS X webserver(port 80) and python SimpleHTTPServer (port 3000).

In both cases the response is empty.

<h1>Single Test Page</h1>

<script>

var httpReq = null;
var url = "http://127.0.0.1:8080/sp";

window.onload = function(){
    var myRequest = new XMLHttpRequest();
    myRequest.open('get', url);
    myRequest.onreadystatechange = function(){
        if ((myRequest.readyState == 4) || (myRequest.status == 200)){
            alert(myRequest.responseText);
        }
    }
    myRequest.send(null);
}

</script>

Could it be an issue with xss attack prevention?
How can I change my setup to use JS to talk to my servlet?
Is there any other way I can make the HTTP get request from JS?

I even added an entry into my /etc/hosts file:
127.0.0.1 foo.com
and changed the JS url to no avail.

Answer 1

Yes, the problem is that it’s a cross domain request.

2 possible solutions :

• use JSONP
• set CORS headers so that the browser knows it may embed your servlet answer

Both are easy but the second one has the advantage that you just have to set the headers in the servlet code. For example :

    response.setHeader("Access-Control-Allow-Origin", "*");
    response.setHeader("Access-Control-Request-Method", "GET");

Another thing : be careful to open your html file in http:// and not file://.