hibernate-HQL（query language）-16

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几种查询方式：
nativeSQL
缺点：不能跨平台
优点：需要存储过程、复杂查询的时候重要
HQL(hibernate query language)
把hql语言转换为方言
EJB QL(JP QL 1.0)
可以认为是hql的子集
QBC
QBE
public class HibernateORMappingTest {    public static SessionFactory sf = null;    @BeforeClass    public static void beforeClass(){        Configuration cfg = new AnnotationConfiguration();        sf = cfg.configure().buildSessionFactory();    }    @Test    public void testSave(){        Session session = sf.getCurrentSession();        session.beginTransaction();        for(int i=0; i<10; i++){            Category c = new Category();            c.setName("c"+i);            session.save(c);        }        for(int i=0; i<10; i++){            Category c = new Category();            c.setId(1);            Topic t = new Topic();            t.setCategory(c);            t.setTitle("t"+i);            t.setCreateDate(new Date());            session.save(t);        }        for(int i=0; i<10; i++){            Topic t = new Topic();            t.setId(1);            Msg m = new Msg();            m.setTopic(t);            m.setCont("m"+i);            session.save(m);        }        session.getTransaction().commit();    }    @Test    public void testHQL_01(){        Session session = sf.getCurrentSession();        session.beginTransaction();        Query q = session.createQuery(" from Category ");        List<Category> categorys = (List<Category>)q.list();        for(Category c:categorys){            System.out.println(c.getName());        }        session.getTransaction().commit();    }    @Test    public void testHQL_02(){        Session session = sf.getCurrentSession();        session.beginTransaction();        Query q = session.createQuery(" from Category c where c.name>'c5' ");        List<Category> categorys = (List<Category>)q.list();        for(Category c:categorys){            System.out.println(c.getName());        }        session.getTransaction().commit();    }    @Test    public void testHQL_03(){        Session session = sf.getCurrentSession();        session.beginTransaction();        Query q = session.createQuery(" from Category c order by c.name desc ");        List<Category> categorys = (List<Category>)q.list();        for(Category c:categorys){            System.out.println(c.getName());        }        session.getTransaction().commit();    }    @Test    public void testHQL_04(){        Session session = sf.getCurrentSession();        session.beginTransaction();        //  对象不重复  即主键不同        Query q = session.createQuery(" select distinct c from Category c order by c.name desc ");        List<Category> categorys = (List<Category>)q.list();        for(Category c:categorys){            System.out.println(c.getName());        }        session.getTransaction().commit();    }    @Test    public void testHQL_05(){        Session session = sf.getCurrentSession();        session.beginTransaction();        Query q = session.createQuery("  from Category c where c.id > :min and c.id < :max ");//        Query q = session.createQuery("  from Category c where c.id > :min and c.id < :max ")//                .setParameter("min",2)//                .setParameter("max",8);//        q.setParameter("min",2);//        q.setParameter("max",8);        q.setInteger("min",2);        q.setInteger("max",8);        List<Category> categorys = (List<Category>)q.list();        for(Category c:categorys){            System.out.println(c.getName());        }        session.getTransaction().commit();    }    //分页    @Test    public void testHQL_07(){        Session session = sf.getCurrentSession();        session.beginTransaction();        Query q = session.createQuery(" from Category c order by c.name desc ");        q.setMaxResults(4);// 每页4条        q.setFirstResult(2);// 从第二条开始        List<Category> categorys = (List<Category>)q.list();        for(Category c:categorys){            System.out.println(c.getName());        }        session.getTransaction().commit();    }    @Test    public void testHQL_08(){        Session session = sf.getCurrentSession();        session.beginTransaction();        Query q = session.createQuery(" select c.id,c.name from Category c order by c.name desc ");        List<Object[]> categorys = (List<Object[]>)q.list();        for(Object[] o:categorys){            System.out.println(o[1]);        }        session.getTransaction().commit();    }    // Topic中设定fetchtype为lazy   则不会有第二条sql语句    @Test    public void testHQL_09(){        Session session = sf.getCurrentSession();        session.beginTransaction();        Query q = session.createQuery("  from Topic t where t.category.id =1 ");        List<Topic> topics = (List<Topic>)q.list();        for(Topic t:topics){            System.out.println(t.getTitle());//            System.out.println(t.getCategory().getId());        }        session.getTransaction().commit();    }    @Test    public void testHQL_11(){        Session session = sf.getCurrentSession();        session.beginTransaction();        Query q = session.createQuery("  from Msg m where m.topic.category.id =1 ");        for(Object o:q.list()){            Msg m = (Msg)o;            System.out.println(((Msg) o).getCont());        }        session.getTransaction().commit();    }    // 为什么t.category不能写成 Category    // 因为可能有多个成员变量类型都是Category,需要指明是对哪个变量做连接操作    //     @Test    public void testHQL_13(){        Session session = sf.getCurrentSession();        session.beginTransaction();        Query q = session.createQuery(" select t.title,c.name from Topic t join t.category c ");        for(Object o:q.list()){            Object[] m = (Object[])o;            System.out.println(m[0]+"-"+m[1]);        }        session.getTransaction().commit();    }    @Test    public void testSchemaExport(){        //  true  是否将建表语句输出到控制台   true  是否在数据库中建表        new SchemaExport(new AnnotationConfiguration().configure()).create(true,true);    }    @AfterClass    public static void AfterClass(){        sf.close();    }}
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