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=?