java - GSON将json值反序列化为Java对象

Question

我有以下 json 对象:

{
    "aSize": 1,
    "aPrice": 1,
    "aName": "Ticket",
    "aDescription": "Tickets are required to unlock the story"
}

和 Java 对象:

public class Item
{
    private String   aId;  
    private int      aSize;  
    private Currency aPrice;   
    private String   aName; 
    private String   aDescription;
}

public class Currency
{
    private int aPrice;
}

当我尝试反序列化 Item 对象时，出现此错误:

com.google.gson.JsonSyntaxException: java.lang.IllegalStateException: Not a JSON Object: 1

我不想将 aPrice 更改为 Json 对象。

问题是 - 我可以以某种方式告诉 GSON 从 Json 值构造货币对象，而不是为整个 Item 类创建反序列化器吗？

Answer 1

首先，您应该创建一个实现 JsonDeserializer 接口(interface)的 ItemDeserializer 类。

import com.google.gson.*;

import java.lang.reflect.Type;

public class ItemDeserializer implements JsonDeserializer<Item> {

    public Item deserialize(JsonElement jsonElement, Type type, JsonDeserializationContext jsonDeserializationContext) throws JsonParseException 
    {  
        JsonObject jsonObject = jsonElement.getAsJsonObject();
        Item item = new Item();
        item.setaName(jsonObject.get("aName").getAsString());
        item.setaSize(jsonObject.get("aSize").getAsInt());
        item.setaPrice(new Currency(jsonObject.get("aPrice").getAsInt()));
        item.setaDescription(jsonObject.get("aDescription").getAsString());
        return item;
    }
}

你可以这样调用它:

public static void main(String args[]) {
        String json = "{ \"aSize\": 1, \"aPrice\": 1, \"aName\": " +
                "\"Ticket\", \"aDescription\": \"Tickets are required to unlock the story\" }";
        GsonBuilder gsonBuilder = new GsonBuilder();
        ItemDeserializer itemDeserializer = new ItemDeserializer();
        gsonBuilder.registerTypeAdapter(Item.class, itemDeserializer);
        Gson customGson = gsonBuilder.create();
        Item item = customGson.fromJson(json, Item.class);
        System.out.println(item);
 }