hibernate的查询方法以及返回的值类型
操作方法
- 01
多对多关系 一定要有一边需要配置inverse 如果两个对象都没有保存，有两种方式进行保存 1、cascade="save-update" 2、save 两次 一对一关系 eg. 用户 用户详情 Hibernate的查询分几种 HQL,QBC(QBE),SQL HQL查询 HQL是基于面向对象的，里面没有表，也没有列，有类和属性 直接以from开头，表示全部选择 从Hibernate3.1可以执行修改和删除 from Emp eg1. 带?参数查询 Session session = HibernateSessionFactory.getSession(); String hql="from Emp e where e.ename like ?"; Query query=session.createQuery(hql); query.setString(0, "%"+"a"+"%"); List list=query.list(); System.out.println(list.size()); HibernateSessionFactory.closeSession(); eg.2 带：命名参数 Session session = HibernateSessionFactory.getSession(); String hql="from Emp e where e.ename like :name"; Query query=session.createQuery(hql); query.setString("name", "%a%"); List list=query.list(); System.out.println(list.size()); HibernateSessionFactory.closeSession(); eg3.in查询 Session session = HibernateSessionFactory.getSession(); String hql="from Emp e where e.empno in (:list)"; Query query=session.createQuery(hql); query.setParameterList("list", new Long[]{1L,3L,5L}); List list=query.list(); System.out.println(list.size()); HibernateSessionFactory.closeSession(); eg4.连接查询 Session session = HibernateSessionFactory.getSession(); String hql = "from Emp e where e.dept.dname like ?"; Query query = session.createQuery(hql); query.setString(0, "%RE%"); List list = query.list(); System.out.println(list.size()); HibernateSessionFactory.closeSession(); eg5. 笛卡尔积 Session session = HibernateSessionFactory.getSession(); String hql = "select e from Emp e,Dept"; Query query = session.createQuery(hql); List list = query.list(); System.out.println(list.size()); HibernateSessionFactory.closeSession(); eg6. 带条件 Session session = HibernateSessionFactory.getSession(); String hql = "select e from Emp e,Dept d where e.dept=d"; Query query = session.createQuery(hql); List list = query.list(); System.out.println(list.size()); HibernateSessionFactory.closeSession(); eg7. select 多个对象，会形成 List里面放Object数组，数组里面放对象 Session session = HibernateSessionFactory.getSession(); String hql = "select e,d from Emp e,Dept d where e.dept=d"; Query query = session.createQuery(hql); List list = query.list(); System.out.println(list.size()); HibernateSessionFactory.closeSession(); eg8. select 一列，就会形成这一列类型的集合，不会生成Object数组 Session session = HibernateSessionFactory.getSession(); String hql = "select e.empno from Emp e,Dept d where e.dept=d"; Query query = session.createQuery(hql); List list = query.list(); System.out.println(list.size()); HibernateSessionFactory.closeSession(); eg9. select多个值，会形成Object[] Session session = HibernateSessionFactory.getSession(); String hql = "select e.empno,e.ename from Emp e,Dept d where e.dept=d"; Query query = session.createQuery(hql); List list = query.list(); System.out.println(list.size()); HibernateSessionFactory.closeSession(); eg10.查询生成List里面放HashMap,key由as后面的字符串决定 Session session = HibernateSessionFactory.getSession(); String hql = "select new map(e.empno as id,e.ename as name) from Emp e"; Query query = session.createQuery(hql); List list = query.list(); System.out.println(list.size()); HibernateSessionFactory.closeSession(); eg11.迫切左连接查询 Session session = HibernateSessionFactory.getSession(); String hql = "from Emp e left join fetch e.dept"; Query query = session.createQuery(hql); List list = query.list(); System.out.println(list.size()); HibernateSessionFactory.closeSession(); eg12.分页查询 Session session = HibernateSessionFactory.getSession(); String hql = "from Emp "; Query query = session.createQuery(hql); query.setFirstResult(10);//从第几条开始,初始是0 (page-1)*pageSize; query.setMaxResults(5);//取几条 List list = query.list(); System.out.println(list.size()); HibernateSessionFactory.closeSession();