无法选择参数化类型

Question

我想创建一个休息来在服务器和客户端之间进行通信.

下面给出的构造函数:

public class RestHelper<I, R> {
    public RestHelper(String url, I input, Class<R> output){
        ResponseEntity<R> responseEntity = restTemplate.exchange(url, HttpMethod.POST, requestEntity, output );
    }
}

对于普通类型,我可以这样做:

RestHelper<User, Result> helper = new RestHelper<>(url, user, Result.class);

我如何传递泛型类型,如:

ResultContainData<Boolean>

以下代码无效:

    ResultContainData<Boolean> result = new ResultContainData<>();
    RestHelper<User, ResultContainData<Boolean>> helper = new RestHelper<>(url, user, (Class<ResultContainData<Boolean>>) ((ParameterizedType) result.getClass().getGenericSuperclass()).getActualTypeArguments()[0]);

我收到了运行时错误:无法转换为ParameterizedType.

Answer 1

我得到了解决方案.

ResultContainData<Boolean> result = new ResultContainData<>();
RestHelper<User, ResultContainData<Boolean>> helper = new RestHelper<>(url, user, (Class<ResultContainData<Boolean>>)result.getClass());

它对我有用.我仍在寻找更好的解决方案.

Answer 2

您只能通过在子类定义中捕获它们来学习I和R的值 - 否则它们将在运行时被擦除.例如:

class MyStringRestHelper extends RestHelper<String, String> {

然后使用类似TypeTools的东西,你可以解析I和R的值:

Class<?>[] typeArgs = TypeResolver.resolveRawArguments(RestHelper.class, MyStringRestHelper.class);
Class<?> i = typeArgs[0];
Class<?> r = typeArgs[1];
assert i == r == String.class;