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Hibernate（十五）：QBC检索和本地SQL检索
- 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
1 @Test 2 public void testCriteria00() { 3 // 1、创建criteria对象 4 Criteria criteria = session.createCriteria(Employee.class); 5 6 // 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。 7 criteria.add(Restrictions.eq("email", "tommy10@dx.com")); 8 criteria.add(Restrictions.gt("salary", 1000F)); 9 10 System.out.println(criteria.uniqueResult());11 }
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
1 @Test 2 public void testCriteraAndOr() { 3 Criteria criteria = session.createCriteria(Employee.class); 4 5 // 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 6 Conjunction conjunction = Restrictions.conjunction(); 7 conjunction.add(Restrictions.like("name", "2", MatchMode.ANYWHERE)); 8 Department depart = new Department(); 9 depart.setId(5);10 conjunction.add(Restrictions.eq("department", depart));11 12 // OR13 Disjunction disjunction = Restrictions.disjunction();14 disjunction.add(Restrictions.gt("salary", 10000F));15 disjunction.add(Restrictions.isNull("email"));16 17 criteria.add(disjunction);18 criteria.add(conjunction);19 20 List<Employee> items = (List<Employee>) criteria.list();21 System.out.println(items.size());22 }
执行sql及结果：
1 Hibernate: 2 select 3 this_.ID as ID1_1_0_, 4 this_.NAME as NAME2_1_0_, 5 this_.SALARY as SALARY3_1_0_, 6 this_.EMAIL as EMAIL4_1_0_, 7 this_.DEPARTMENT_ID as DEPARTME5_1_0_ 8 from 9 DX_EMPLOYEE this_ 10 where11 (12 this_.SALARY>? 13 or this_.EMAIL is null14 ) 15 and (16 this_.NAME like ? 17 and this_.DEPARTMENT_ID=?18 )19 2
3）通过Critera实现统计查询：使用Projection 来表示
1 @Test2 public void testStatistics(){3 Criteria criteria=session.createCriteria(Employee.class);4 5 // 统计查询：使用Projection 来表示6 criteria.setProjection(Projections.max("salary"));7 8 System.out.println(criteria.uniqueResult()); 9 }
执行sql及结果：
1 Hibernate: 2 select3 max(this_.SALARY) as y0_ 4 from5 DX_EMPLOYEE this_6 79000.0
4）通过Critera实现排序、分页查询
1 @Test 2 public void testOrderByAndPager() { 3 Criteria criteria = session.createCriteria(Employee.class); 4 5 // 1) Order By 6 criteria.addOrder(Order.desc("salary")); 7 criteria.addOrder(Order.desc("name")); 8 9 // 2) Pager10 int pageSize = 5;11 int pageNum = 2;12 List<Employee> employees = (List<Employee>) criteria.setFirstResult((pageNum - 1) * pageSize).setMaxResults(pageSize).list();13 14 System.out.println(employees.size());15 }
执行sql及结果：
1 Hibernate: 2 select 3 this_.ID as ID1_1_0_, 4 this_.NAME as NAME2_1_0_, 5 this_.SALARY as SALARY3_1_0_, 6 this_.EMAIL as EMAIL4_1_0_, 7 this_.DEPARTMENT_ID as DEPARTME5_1_0_ 8 from 9 DX_EMPLOYEE this_ 10 order by11 this_.SALARY desc,12 this_.NAME desc limit ?,13 ?14 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。
Hibernate（十五）：QBC检索和本地SQL检索
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