spring date jpa 查询列最大值

@Resource
private EntityManagerFactory entityManagerFactory;
public Date getMaxCreatetime(){
EntityManager em = entityManagerFactory.createEntityManager();
CriteriaBuilder cb = em.getCriteriaBuilder();
CriteriaQuery<Date> cq = cb.createQuery(Date.class); //查询结果

//在哪个表查
Root<SysLog> root = cq.from(SysLog.class);
cq.select(cb.greatest((Path)root.get("createtime")));

//结果
TypedQuery<Date> typedQuery = em.createQuery(cq);
return typedQuery.getSingleResult();

}