Get json data server side in java web application

i have trying to make ajax call with json and below is my code discription

$(document).ajaxStart(function () {

    $("#innerpanel").html("<img class='test' src='Image/ajax-loader_clock.gif' alt='loading...' />");});

    /* $("#loader").ajaxStop(function () {
        $(this).hide();
    }); */

    $('#btn').click(function(){
        testService();
     });

    function  testService(){  
        name=$("#name").val();
        password=$("#password").val();
        var testData={name : name,password : password}; 

        $.ajax({
            type: "post",
            url: "login.do",
             data:testData,
             contentType: "application/json; charset=utf-8",
            dataType: "json", 
            success: function(msg) {
                alert("madhav");
                $("#innerpanel").html("<p1>Welcome</p1> </br>"+"<p1>"+msg.name+"</p1></br><p1> and Your password is "+msg.password+"</p1>");
                /* document.writeln("Book id: " +  msg.name); */
            }
        });
    }
});

and sever side code is

String userName=request.getParameter("name");
String password=request.getParameter("password");
PrintWriter writer = response.getWriter();
JSONObject obj=new JSONObject();

obj.put("name", userName);
obj.put("password",password);
writer.print(obj);
writer.flush();

But i get null value for both username and password .please help me with example how can I get name and password server side.

if i remove code from request

    contentType: "application/json; charset=utf-8",
    dataType: "json", 

i get name and password value with above server side code. but how can i do it without removing

    contentType: "application/json; charset=utf-8",
    dataType: "json",