在同一日期字段列中查找min和max，并使用jpa实体管理器条件生成器进行计数

CriteriaBuilder cb = entityManager.getCriteriaBuilder();
CriteriaQuery<Entity> query = cb.createQuery(Entity.class);
Root<Entity> root = query.from(Entity.class);

// 查找最小值
query.select(root).orderBy(cb.asc(root.get("dateField")));
Entity minEntity = entityManager.createQuery(query).setMaxResults(1).getSingleResult();

// 查找最大值
query.select(root).orderBy(cb.desc(root.get("dateField")));
Entity maxEntity = entityManager.createQuery(query).setMaxResults(1).getSingleResult();

CriteriaBuilder cb = entityManager.getCriteriaBuilder();
CriteriaQuery<Long> query = cb.createQuery(Long.class);
Root<Entity> root = query.from(Entity.class);

// 计数
query.select(cb.count(root));

Long count = entityManager.createQuery(query).getSingleResult();