jquery-ajax、struts2、json数据问题

jquery代码：

$.ajax({
   url:url,
   type:'post',
   data:{"key1": "value1", "key2": "value2"},
   dataType:'json',
   error:function(){},
   success:function(result){
     $("#id").html(result.key1);
   }
 });

java代码：

public String testAjax(){
  
  response.setContentType("application/x-json");
  response.setCharacterEncoding("UTF-8");
  
  String value1 = request.getParameter("key1");
  String value2 = request.getParameter("key2");
  String value3 = request.getParameter("key3");
  
  Map<String, Object> map = new HashMap<String, Object>();
  map.put("key1", value1);
  map.put("key2", value2);
  map.put("key3", value3);

  PrintWriter out = null;
  try{
    out.response.getWriter();
    //将map转换成json格式，具体用法及所需jar包可以参考官方文档
    JSONObject result = JSONObject.fromObject(map);
    out.print(result);
    out.flush();
  }catch(IOException e){
    e.printStackTrace();
  }finally{
    if(out != null){
      out.close();
    }
  }
  return null;
}