use of gson

Gson gson = new Gson ();
Sell sell = new sell();
Sell ​​sell1 = gson.fromJson(SellJson,Sell.class);//json string to object
String text = gson.toJson(sell);//Object to string map, list to string
// convert listJson string to list
Type type = new TypeToken<ArrayList<String>>() {  
}.getType();  
ArrayList<String> sList=gson.fromJson(listJsonStr, type);  

When parsing json data, if the data is an array, you can use TypeToKen to parse it.

public static OrderDTO convert(OrderForm orderForm) {
    List<OrderDetail> orderDetailList = new ArrayList<>();
    Gson gson = new Gson ();
    OrderDTO orderDTO = new OrderDTO();
try {
    orderDetailList = gson.fromJson(orderForm.getItems(),
    new TypeToken<List<OrderDetail>>(){}.getType());
}catch (Exception e){
    log.error("[Object conversion] error, string={}",orderForm.getItems());
    throw new SellException(ExceptionEnum.PARAM_ERROE);
}

    orderDTO.setOrderDetailList(orderDetailList);
    return orderDTO;
}