Ajax异步从后台取Json数据

前台JSP页面：

function doCheck(roomId,userEname,status,i){
		$.post("${ctx}/admin/user/docheck",{roomId:roomId,userEname:userEname,status:status,i:i},function(data){
			var oTxt=jQuery.parseJSON(data);
			alert(oTxt.msg);
			if(oTxt.flag=="T")
				$("#check"+i).hide();
		});
	}

后台JAVA：

public @ResponseBody String approveUser(HttpServletRequest request,HttpServletResponse response,@RequestParam(value="id") String id,@RequestParam(value="roomId") String roomId){
		JSONObject json=new JSONObject();
		try{
			roomUserManager.modfiy(id,roomId);
			json.put("flag","T");
			json.put("msg","审核通过");
		}catch(Exception ex){
			json.put("flag","F");
			json.put("msg","操作异常");
		}
		showJson(json,response);
	}

protected String showJson(JSONObject jvo,HttpServletResponse response){
		try {
			response.setContentType("text/html;charset=UTF-8");
			PrintWriter out = response.getWriter();
			out.print(jvo.toString());
		} catch (Exception e) {
			e.printstacktrace();
		}
		return null;
	}