Not able to send restful server using post method in javascript in PHONEGAP android

Question

i m using the same code and not able to send restful request in phonegap getting error Access-control-allow-origin is null.

`//JSON OBJECT

var obj = {
        "userId": UserId,
        "userName1": UserName1,
        "userName2": UserName2,
        "recipientType":RecipientType,
        "RecipientValue":RecipientValue,
        }

        var jsonString = JSON.stringify(obj);
            alert(jsonString);

//THIS IS HOW I SEND JSON OBJECT

            var url = "http://someurl";
            var xmlHttp = new XMLHttpRequest();
            xmlHttp.open( "post", url, false );
            xmlHttp.setRequestHeader("Content-Type","application/json");
            xmlHttp.send(jsonString);
            alert(xmlHttp.responseText);

`