JS异步请求，controller返回一个map集合，在js中获取

//js
function checkUser(cell){
//ajax请求后台
$.post("${pageContext.request.contextPath}/liuyan/check.action",{userName:cell.value},function(data){
var isSuccess=data["check"];
if(isSuccess==1){
$("#check").show();
}else{
$("#check").hide();
}
});
}
//controller
@RequestMapping("/check")
@ResponseBody
public Map<String,String> checkUser(String userName){
boolean isSuccess=service.checktUser(userName, null);
Map<String,String> map=new HashMap<String, String>();
String s="1";
if(isSuccess){
s="1";
}else{
s="0";
}
map.put("check", s);
return map;
}