code: public static Class<?> getParameterRealGenericClass(Class<?> clazz, Type type, int index) {
          if (type instanceof ParameterizedType) {
              Type[] actualTypeArguments = ((ParameterizedType) type).getActualTypeArguments();
              return getRealGenericClass(clazz, actualTypeArguments[index]);
          }
          return Object.class;
      }
docs: 获取泛型类参数的实际类型.例如 Map<String, E>，获取E实际的类型.
  @param clazz 泛型基类.
  @param type 泛型基类中的某个type
  @return