Hibernate（十五）：QBC检索、本地SQL检索和HQL删除

• QBC检索

QBC查询就是通过使用Hibernate提供的Query By Criteria API来查询对象，这种API封装了SQL语句的动态拼装，对查询提供了更加面向对象的功能接口。

1）通过Critera实现具有条件的查询

     @Test
     public void testCriteria00() {
         // 1、创建criteria对象
         Criteria criteria = session.createCriteria(Employee.class);
 
         // 2、添加过滤条件可以用Criterion表，Criterion可以通过Restrictions的静态方法返回。
         criteria.add(Restrictions.eq("email", "tommy10@dx.com"));
         criteria.add(Restrictions.gt("salary", 1000F));
 
         System.out.println(criteria.uniqueResult());
     }

执行sql及结果:

Hibernate:
    select
        this_.ID as ID1_1_0_,
        this_.NAME as NAME2_1_0_,
        this_.SALARY as SALARY3_1_0_,
        this_.EMAIL as EMAIL4_1_0_,
        this_.DEPARTMENT_ID as DEPARTME5_1_0_
    from
        DX_EMPLOYEE this_
    where
        this_.EMAIL=?
        and this_.SALARY>?
Employee [id=11, name=tommy10, salary=10000.0, email=tommy10@dx.com]

2）通过Critera实现具有AND OR条件的查询

 @Test
     public void testCriteraAndOr() {
         Criteria criteria = session.createCriteria(Employee.class);
 
         // AND :使用Conjunction表示，Conjunction本身就是一个Criterion对象，且其中还可以添加Criterion对象
         Conjunction conjunction = Restrictions.conjunction();
         conjunction.add(Restrictions.like("name", "2", MatchMode.ANYWHERE));
         Department depart = new Department();
         depart.setId(5);
         conjunction.add(Restrictions.eq("department", depart));
 
         // OR
         Disjunction disjunction = Restrictions.disjunction();
         disjunction.add(Restrictions.gt("salary", 10000F));
         disjunction.add(Restrictions.isNull("email"));
 
         criteria.add(disjunction);
         criteria.add(conjunction);
 
         List<Employee> items = (List<Employee>) criteria.list();
         System.out.println(items.size());
     }

执行sql及结果：

 Hibernate:
     select
         this_.ID as ID1_1_0_,
         this_.NAME as NAME2_1_0_,
         this_.SALARY as SALARY3_1_0_,
         this_.EMAIL as EMAIL4_1_0_,
         this_.DEPARTMENT_ID as DEPARTME5_1_0_
     from
         DX_EMPLOYEE this_
     where
         (
             this_.SALARY>?
             or this_.EMAIL is null
         )
         and (
             this_.NAME like ?
             and this_.DEPARTMENT_ID=?
         )
 2

3）通过Critera实现统计查询：使用Projection 来表示

     @Test
     public void testStatistics(){
         Criteria criteria=session.createCriteria(Employee.class);
 
         // 统计查询：使用Projection 来表示
         criteria.setProjection(Projections.max("salary"));
 
         System.out.println(criteria.uniqueResult());
     }

执行sql及结果：

 Hibernate:
     select
         max(this_.SALARY) as y0_
     from
         DX_EMPLOYEE this_
 79000.0

4）通过Critera实现排序、分页查询

     @Test
     public void testOrderByAndPager() {
         Criteria criteria = session.createCriteria(Employee.class);
 
         // 1) Order By
         criteria.addOrder(Order.desc("salary"));
         criteria.addOrder(Order.desc("name"));
 
         // 2) Pager
         int pageSize = 5;
         int pageNum = 2;
         List<Employee> employees = (List<Employee>) criteria.setFirstResult((pageNum - 1) * pageSize).setMaxResults(pageSize).list();
 
         System.out.println(employees.size());
     }

执行sql及结果：

 Hibernate:
     select
         this_.ID as ID1_1_0_,
         this_.NAME as NAME2_1_0_,
         this_.SALARY as SALARY3_1_0_,
         this_.EMAIL as EMAIL4_1_0_,
         this_.DEPARTMENT_ID as DEPARTME5_1_0_
     from
         DX_EMPLOYEE this_
     order by
         this_.SALARY desc,
         this_.NAME desc limit ?,
         ?
 5

更多关于QBC的使用方式需要参考Hibernate官网实例。

• 本地SQL查询

本地SQL查询来完善HQL不能涵盖所有的查询特性。

     @Test
     public void testNativeSqlInsert() {
         String sql = "insert into dx_department(id,name)values(?,?);";
 
         Query query = session.createSQLQuery(sql);
 
         query.setInteger(0, 7).setString(1, "移动部门").executeUpdate();
 
         Department departs = session.get(Department.class, 7);
         System.out.println(departs);
     }

执行sql及结果：

 Hibernate:
     insert
     into
         dx_department
         (id,name)
     values
         (?,?);
 Hibernate:
     select
         department0_.ID as ID1_0_0_,
         department0_.NAME as NAME2_0_0_
     from
         DX_DEPARTMENT department0_
     where
         department0_.ID=?
 Department [id=7, name=移动部门]

• HQL删除操作：

     @Test
     public void testDeleteWithHQL() {
         String hql = "DELETE FROM Department d WHERE d.id=:id";
         session.createQuery(hql).setInteger("id", 7).executeUpdate();
     }

执行sql及结果：

 Hibernate:
     delete
     from
         DX_DEPARTMENT
     where
         ID=?