GET request using ajax v java -

i'm writing simple web application completes 1 request custom headers. when tried making request using ajax, gave me cross domain error so:

 no 'access-control-allow-origin' header present on requested resource.   origin 'http://localhost:8080' therefore not allowed access. 

when make same request in java using custom headers, works fine.

    public static string executeget() {     string response = "";     try {         url url = new url("http://....");         httpurlconnection con = (httpurlconnection) url.openconnection();         con.setrequestmethod("get");           //set custom headers           con.setrequestproperty("header1", "2.0");         con.setrequestproperty("header2", "sellingv2");         con.connect();          inputstreamreader reader = new inputstreamreader(con.getinputstream());         scanner scanner = new scanner(reader);         while (scanner.hasnext()) {             response += scanner.next();         }         scanner.close();         con.disconnect();     }     catch (exception ex) {         ex.printstacktrace();     }     return response; } 

why work in java , not ajax?

this request works in java , not ajax because ajax called within web browser. web browsers enforce "same-origin policy" prevents front-end scripts performing possibly malicious ajax requests. java application not subject limitation can make request fine. access-control-allow-origin header can used override functionality, server not configured use it. case protocol, host, or port, in url string not match hosting front-end files. if change url relative path should work.