springmvc怎么接收json对象 springmvc接收json对象的方式

function fAddObj() {
  var obj = {};
  obj['objname'] = "obj";
  obj['pid'] = 1 ;
  $.ajax({
    url: 'admin/Obj/addObj.do',
    method: 'post',
    contentType: 'application/json', // 这句不加出现415错误:Unsupported Media Type
    data: JSON.stringify(obj), // 以json字符串方式传递
    success: function(data) {
      console.log("success...");
    },
    error: function(data) {
      console.log("error...");
    }
  });
}

@Controller
@RequestMapping("/admin/Obj")
public class ObjAction {
  // 注入操作类
  @Autowired
  private ObjService objService ;
  @RequestMapping(value = "/addObj")
  @ResponseBody
  public String addObj(@RequestBody Obj obj) {
    this.objService.insertObj(cate);
    return "success";
  }
}

@Controller
@RequestMapping("/admin/Obj")
public class ObjAction {
  /**
   * 前端操作与上面相同
   * @return
   */
  @RequestMapping(value = "/updateAttr")
  @ResponseBody
  public String updateAttr(@RequestBody Map map) {
    if(map.containsKey("id"){
      Integer id = Integer.parseInt(map.get("id"));
    }
    if(map.containsKey("objname"){
      String objname = map.get("objname").toString();
    }
    if(map.containsKey("pid"){
      Integer pid = Integer.parseInt(map.get("pid"));
    }
    // 操作 ...
    return "success";
  }
}