axaj參數怎樣以json形式傳輸

前端頁面：     

data: JSON.stringify(obj_j),
contentType : "application/json;charset=utf-8",

後端接收

String jsonStr = "";
try {
      jsonStr = IOUtils.toString(request.getInputStream(),"utf-8");
} catch (IOException e) {
      e.printStackTrace();
}