问使用GSON将JSON字符串的一部分映射到抽象类

EN

{
    "Items" : [
        {
            "id" : "ID1",
            "seller_id": 17, 
            "item_plan": {
                "action" : "Sell"
            }
        },
        {
            "id" : "ID2",
            "seller_id": 27, 
            "item_plan": {
                "action": "Remove",
            }
        }
    ]
}

public class RequestObject {

    @SerializedName("Items")
    @Expose
    private List<Item> items = null;

public class Item {
    @SerializedName("id")
    @Expose
    private String id;
   
    @SerializedName("seller_id")
    @Expose
    private Integer sellerID;

    @SerializedName("item_Plan")
    @Expose
    private ItemPlan item_plan;

public abstract class ItemPlan {
    @SerializedName("action")
    @Expose
    private String action;

    public abstract void executePlan()

RuntimeTypeAdapterFactory<ItemPlan> itemPlanRuntimeTypeAdapterFactory =
                RuntimeTypeAdapterFactory
                .of(ItemPlan.class, "action")
                .registerSubtype(SellPlan.class, "Sell")
                .registerSubtype(RemovePlan.class, "Remove");

Gson gson = new 
GsonBuilder().registerTypeAdapterFactory(itemPlanRuntimeTypeAdapterFactory).create();
        
RequestObject request = gson.fromJson(jsonString, RequestObject.class);