1.HQL简介:HQL是Hibernate Query Language(Hibernate 查询语言)的缩写,提供更加丰富灵活、更为强大的查询能力;HQL更接近SQL语句查询语法。Hibernate 查询语言(HQL)是一种面向对象的查询语言,类似于 SQL,但不是去对表和列进行操作,而是面向对象和它们的属性。 HQL 查询被 Hibernate 翻译为传统的 SQL 查询从而对数据库进行操作。
HQL的基本语法:
public class HQLTest {
@Test
/**
* HQL无条件查询
*/
public void select() {
Session session = HibernateUtils.getCurrentSession();
Transaction tx = session.beginTransaction();
List<Customer> list = session.createQuery(" from Customer").list();
list.forEach(System.out::println);
tx.commit();
}
@Test
/**
* HQL别名查询
*/
public void select2() {
Session session = HibernateUtils.getCurrentSession();
Transaction tx = session.beginTransaction();
List<Customer> list = session.createQuery("select c from Customer c").list();
list.forEach(System.out::println);
tx.commit();
}
@Test
/**
* HQL排序查询
*/
public void sort() {
Session session = HibernateUtils.getCurrentSession();
Transaction tx = session.beginTransaction();
List<LinkMan> list = session.createQuery(" from LinkMan order by lkm_id desc").list();
list.forEach(System.out::println);
tx.commit();
}
@Test
/**
* HQL 多条件查询
*/
public void conditionSelect() {
Session session = HibernateUtils.getCurrentSession();
Transaction tx = session.beginTransaction();
//按位置绑定
/*Query query = session.createQuery(" from LinkMan where lkm_id=? and lkm_phone=?");
query.setParameter(0,20L);
query.setParameter(1,"2");
List<LinkMan> list = query.list();*/
//按名称绑定
Query query = session.createQuery(" from LinkMan where lkm_id= :a and lkm_phone= :b");
query.setParameter("a", 20L);
query.setParameter("b", "2");
List<LinkMan> list = query.list();
list.forEach(System.out::println);
tx.commit();
}
@Test
/**
* HQL投影查询 查询部分字段
*/
public void select3() {
Session session = HibernateUtils.getCurrentSession();
Transaction tx = session.beginTransaction();
//查询一个字段
//List<Object> list = session.createQuery(" select l.lkm_id from LinkMan l").list();
//查询多个字段
//List<Object[]> list = session.createQuery(" select l.lkm_id,l.lkm_name from LinkMan l").list();
//查询多个属性,分装到对象中去 需要有参构造方法
List<LinkMan> list = session.createQuery(" select new LinkMan(lkm_id,lkm_name) from LinkMan").list();
list.forEach(System.out::println);
tx.commit();
}
@Test
/**
* HQL分页查询
*/
public void limiter() {
Session session = HibernateUtils.getCurrentSession();
Transaction tx = session.beginTransaction();
Query query = session.createQuery(" from LinkMan ");
query.setFirstResult(0);
query.setMaxResults(10);
List<LinkMan> list = query.list();
list.forEach(System.out::println);
tx.commit();
}
@Test
/**
* HQL分组统计查询
*/
public void count() {
//聚合函数的使用:count(),max(),avg(),,sum();
Session session = HibernateUtils.getCurrentSession();
Transaction tx = session.beginTransaction();
//统计查询
//Object uniqueResult = session.createQuery(" select count(*) from LinkMan ").uniqueResult();
//分组统计查询
List list = session.createQuery(" select lkm_name,count(*) from LinkMan group by lkm_phone having count(*)>=2").list();
list.forEach(System.out::println);
tx.commit();
}
}
HQL的多表查询
@Test
/**
* HQL的多表查询
*/
public void select4() {
Session session = HibernateUtils.getCurrentSession();
Transaction tx = session.beginTransaction();
//HQL:内连接 得到的是一个List<Obcect[]>
//List list = session.createQuery("from Customer c join c.linkMans").list();
//HQL:迫切内连接 得到的是一个List<Customer> 就是吧得到的两个表的数据分装到一个对象中去
List<Customer> list = session.createQuery("from Customer c join fetch c.linkMans").list();
list.forEach(System.out::println);
tx.commit();
}
2.QBC简介:QBC(Query By Criteria) API提供了检索对象的另一种方式,它主要由Criteria接口、Criterion接口和Expresson类组成,它支持在运行时动态生成查询语句。
1>调用Session的createCriteria()方法创建一个Criteria对象。
2>设定查询条件。Restrictions类提供了一系列用于设定查询条件的静态方法,
这些静态方法都返回Criterion实例,每个Criterion实例代表一个查询条件。
Criteria的add()方法用于加入查询条件。
3>调用Criteria的list()方法执行查询语句。该方法返回List类型的查询结果,在
List集合中存放了符合查询条件的持久化对象。
QBC的基本语法:
@Test
/**
* QBC查询所有
*/
public void selectAll() {
Session session = HibernateUtils.getCurrentSession();
Transaction tx = session.beginTransaction();
Criteria criteria = session.createCriteria(LinkMan.class);
List list = criteria.list();
list.forEach(System.out::println);
tx.commit();
}
@Test
/**
* QBC多条件查询
* = eq
* > gt
* >= ge
* < lt
* <= le
* <> ne
* like
* in
* and
* or
*/
public void select2() {
Session session = HibernateUtils.getCurrentSession();
Transaction tx = session.beginTransaction();
Criteria criteria = session.createCriteria(LinkMan.class);
criteria.add(Restrictions.eq("lkm_phone","1"));
criteria.add(Restrictions.like("lkm_name","%1"));
List list = criteria.list();
list.forEach(System.out::println);
tx.commit();
}
@Test
/**
* 离线条件查询
*/
public void detachedSelect() {
//在service层将多条件查询分装好 直接传入dao层进行查询
//service层
DetachedCriteria detachedCriteria = DetachedCriteria.forClass(LinkMan.class);
detachedCriteria.add(Restrictions.like("lkm_name","%1"));
//dao层
Session session = HibernateUtils.getCurrentSession();
Transaction tx = session.beginTransaction();
Criteria criteria = detachedCriteria.getExecutableCriteria(session);
List list = criteria.list();
list.forEach(System.out::println);
}
@Test
/**
* QBC分页查询
*/
public void pagingSelect() {
Session session = HibernateUtils.getCurrentSession();
Transaction tx = session.beginTransaction();
Criteria criteria = session.createCriteria(LinkMan.class);
criteria.setFirstResult(0);
criteria.setMaxResults(10);
List list = criteria.list();
list.forEach(System.out::println);
tx.commit();
}
@Test
/**
* QBC排序
*/
public void sort() {
Session session = HibernateUtils.getCurrentSession();
Transaction tx = session.beginTransaction();
Criteria criteria = session.createCriteria(LinkMan.class);
List list = criteria.addOrder(Order.desc("lkm_id")).list();
list.forEach(System.out::println);
tx.commit();
}
3.HQL查询
@Test
public void select() {
Session session = HibernateUtils.getCurrentSession();
Transaction tx = session.beginTransaction();
//addEntity()将查询到的数据分装到一个实体中去
List<Object> list = session.createSQLQuery("select * from cst_customer").addEntity(Customer.class).list();
list.forEach(System.out::println);
tx.commit();
}