Gson忽略实例创建者

Question

我正在定义InstanceCreator并通过GsonBuilder注册，如下所示：

final GsonBuilder gsonBuilder = new GsonBuilder();
gsonBuilder.registerTypeAdapter(java.awt.Shape.class, new ShapeInstanceCreator<>());
final Gson gson = gsonBuilder.create();

但是，我仍然收到以下错误，并且在反序列化JSON时从未看到调用InstanceCreator：

Exception in thread "main" java.lang.RuntimeException: Unable to invoke no-args constructor for interface java.awt.Shape. Register an InstanceCreator with Gson for this type may fix this problem.

有什么理由可以忽略这一点吗？