### Question:
UserDao { public List<UserDO> findAllById(List<Integer> ids) { return mongoTemplate.find(new Query(Criteria.where("_id").in(ids)), UserDO.class); }  void insert(UserDO entity); void updateById(UserDO entity); void deleteById(Integer id); UserDO findById(Integer id); UserDO findByUsername(String username); List<UserDO> findAllById(List<Integer> ids);  }### Answer:
@Test public void testSelectByIds() { List<UserDO> users = userDao.findAllById(Arrays.asList(1, 4)); users.forEach(System.out::println); }