把本地的坐标数据转换成json格式，加载客户端的FeatureLayer到地图服务上，老是报错？

//js代码客户端的点要素加载到FeatureLayer上，然后再加载到地图服务上。但是
var myGraphic= Graphic.fromJSON(jsons); 老是报错：
JSON object is already hydrated，请教大神
 
 
//FeatureLayer中有5个字段var fields = [
{ name: "ObjectID", alias: "ObjectID", type: "oid" }, 
{ name: "CarNumber", alias: "CarNumber", type: "string" },
{ name: "Date_Time", alias: "Date_Time", type: "Date" },
{ name: "Longitude", alias: "Longitude", type: "double" }, 
{ name: "Latitude", alias: "Latitude", type: "double" }
]; 
 
//新建点要素
var point=new Point({ x: 113, y: 28, spatialReference:4326 });
 
 
//点要素的属性值
var pp={ 
           "ObjectID": 1, 
          "CarNumber":"aaaaa", 
         "Date_Time": "2013/5/5 8:30:30", 
         "Longitude":113, 
         "Latitude":28 
}; 
 
 
var jsons={
         "geometry": point, 
         "attributes": pp, 
          "popupTemplate": carTemplate, 
         "symbol":mySymbol 
}; 
 
var myGraphic= Graphic.fromJSON(jsons);    //报错：JSON object is already hydrated
 
var myFeatureLayer=new FeatureLayer({ 
         source: [myGraphic],
         fields: fields, 
         objectIdField: "ObjectID", 
         geometryType: "point", 
        spatialReference: { wkid: 4326 }, 
        popupTemplate: carTemplate, 
        renderer: myRenderer 
});

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