Try this:
@Around("@annotation(MyAnnotation)")
public Object advice(ProceedingJoinPoint pjp) throws Throwable {
Method method = ((MethodSignature) pjp.getSignature()).getMethod();
Type[] genericParamsClass = method.getGenericParameterTypes();
logger.info(((ParameterizedType) genericParamsClass[0]).getActualTypeArguments()[0]);
...
}