JsonAdapterAnnotationTypeAdapterFactory.java 文件源码

@SuppressWarnings({ "unchecked", "rawtypes" }) // Casts guarded by conditionals.
TypeAdapter<?> getTypeAdapter(ConstructorConstructor constructorConstructor, Gson gson,
    TypeToken<?> type, JsonAdapter annotation) {
  Object instance = constructorConstructor.get(TypeToken.get(annotation.value())).construct();

  TypeAdapter<?> typeAdapter;
  if (instance instanceof TypeAdapter) {
    typeAdapter = (TypeAdapter<?>) instance;
  } else if (instance instanceof TypeAdapterFactory) {
    typeAdapter = ((TypeAdapterFactory) instance).create(gson, type);
  } else if (instance instanceof JsonSerializer || instance instanceof JsonDeserializer) {
    JsonSerializer<?> serializer = instance instanceof JsonSerializer
        ? (JsonSerializer) instance
        : null;
    JsonDeserializer<?> deserializer = instance instanceof JsonDeserializer
        ? (JsonDeserializer) instance
        : null;
    typeAdapter = new TreeTypeAdapter(serializer, deserializer, gson, type, null);
  } else {
    throw new IllegalArgumentException(
        "@JsonAdapter value must be TypeAdapter, TypeAdapterFactory, "
            + "JsonSerializer or JsonDeserializer reference.");
  }

  if (typeAdapter != null && annotation.nullSafe()) {
    typeAdapter = typeAdapter.nullSafe();
  }

  return typeAdapter;
}