Ajax向后台传输json格式数据出现错误应如何处理

function saveUser(){
var uuId = document.getElementById("uuid").value;
var idCard = document.getElementById("idCard").value;
alert(uuId+idCard);
// var result = new Object();
// result.uuId = uuId;
// result.idCard = idCard;
// var saveData = JSON.stringify(result);
// alert(saveData);
$.ajax({
url : "xdds/saveUser.do?random=" + Math.random(),
type : "post",
data : {"uuid" : uuId,"idCard" : idCard},
// data:saveData,
dataType : 'json',
// contentType : "application/json",
success:function(data){
}
});
}

@RequestMapping(value = "/saveUser.do", method = { RequestMethod.POST })
@ResponseBody
public Map<String, Object> saveUser (@RequestBody MapUser user){
Map<String, Object> map = new HashMap<String, Object>();
System.out.println(user.getUuid()+user.getIdCard());
map.put("result", "fda");
return map ;
}

var saveData = JSON.stringify(result)<br>这个函数可以转化成真确的json格式。<br><br>ps：小白一个，有不对的地方请大神指正；有大神知道具