java - 使用 gson 反序列化接口(interface)数据无法取回值？

Question

我正在下面运行一个简单的实验测试。

public class MyTest {

    @Test
    public void testing() {
        GsonBuilder builder = new GsonBuilder();
        builder.registerTypeAdapter(SubData.class, new SubDataImplInstanceCreator());
        Gson gson = builder.create();

        Dataclass data = new Dataclass();
        data.key1 = "abc";
        SubDataImpl subData = new SubDataImpl();
        subData.hello = "ttt";
        data.sub = subData;
        String jsonValue = gson.toJson(data);
        System.out.println(jsonValue);

        Dataclass data2 = gson.fromJson(jsonValue, Dataclass.class);
        System.out.println(gson.toJson(data2));

    }

    class Dataclass implements Serializable {
        String key1;
        SubData sub;
    }

    interface SubData {
        String getHello();
    }

    class SubDataImpl implements SubData, Serializable {

        String hello;

        @Override
        public String getHello() {
            return hello;
        }
    }


    public class SubDataImplInstanceCreator implements InstanceCreator<SubDataImpl> {
        @Override
        public SubDataImpl createInstance(Type type) {
            return new SubDataImpl();
        }
    }
}

我期待它回来

{"key1":"abc","sub":{"hello":"ttt"}}
{"key1":"abc","sub":{"hello":"ttt"}}

因为它们本质上是序列化和反序列化的相同数据。

但是，当我运行它时，我得到了

{"key1":"abc","sub":{"hello":"ttt"}}
{"key1":"abc","sub":{}}

为什么在反序列化 Json 字符串后我丢失了 SubData 值？我的代码中遗漏了什么吗？

Answer 1

看来你已经击中了这个bug ，建议的解决方案是为接口(interface)使用 TypeAdapter。

快速而肮脏的实现(用它代替SubDataImplInstanceTypeAdapter)

 public class SubDataImplInstanceTypeAdapter implements JsonDeserializer<SubDataImpl>, JsonSerializer<SubDataImpl> {


    @Override
    public SubDataImpl deserialize(JsonElement json, Type typeOfT, JsonDeserializationContext context) throws JsonParseException {
        SubDataImpl impl = new SubDataImpl();
        JsonObject object = json.getAsJsonObject();
        impl.setHello(object.get("hello").getAsString());
        return impl;

    }

    @Override
    public JsonElement serialize(SubDataImpl src, Type typeOfSrc, JsonSerializationContext context) {
        return context.serialize(src);
    }
}