Map<String,dynamic> str={'cart':cartList};
      cartitem = jsonEncode(str);

{
    {"cart":[
    {
    "cartid":2,
    "pid":"342702",
    "merchantId":"MER-07156",
    "hashkey":"7087fea71afc963d6dc3fa04944008ec",
    "productname":"Scheduling Product - Edit Please",
    "product_image":"Scheduling Product - Edit Please",
    "shipping_price":"0.00",
    "state_tax_rate":"0.0",
    "taxamt":"0.00",
    "discountamt":"0.0",
    "price":"10.00",
    "pricewithattr":"17.00",
    "quantity":"18",
    "totalamount":"306.00",
    "taxvalue":"0.0",
    "attribute_array":"[{"attributeid":"20796","attributename":"Black","groupname":"Color","groupid":"3012"},{"attributeid":"20798","attributename":"Silk","groupname":"Cloth","groupid":"3013"},{"attributeid":"20800","attributename":"small","groupname":"Size","groupid":"3014"}]",
    "is_free":"0",
    "is_payable_later":"0",
    "isattrpresent":"1"
    }
    ]
    }}