Hibernate学习笔记_查询

HQL vs EJBQL

1         NativeSQL >HQL.> EJBQL(JPQL 1.0) > QBC(Query By Criteria) > QBE(Query By Example)"

2         总结：QL应该和导航关系结合，共同为査询提供服务。

@Test
    public void testHQL_01() {
        Session session = sf.openSession();
        session.beginTransaction();
        Query q = session.createQuery("from Category");
        List<Category> categories = (List<Category>)q.list();
        for(Category c : categories) {
            System.out.println(c.getName());
        }
        session.getTransaction().commit();
        session.close();
        
    }
    
    @Test
    public void testHQL_02() {
        Session session = sf.openSession();
        session.beginTransaction();
        Query q = session.createQuery("from Category c where c.name > 'c5'");
        List<Category> categories = (List<Category>)q.list();
        for(Category c : categories) {
            System.out.println(c.getName());
        }
        session.getTransaction().commit();
        session.close();
        
    }
    
    @Test
    public void testHQL_03() {
        Session session = sf.openSession();
        session.beginTransaction();
        Query q = session.createQuery("from Category c order by c.name desc");
        List<Category> categories = (List<Category>)q.list();
        for(Category c : categories) {
            System.out.println(c.getName());
        }
        session.getTransaction().commit();
        session.close();
        
    }
    
    @Test
    public void testHQL_04() {
        Session session = sf.openSession();
        session.beginTransaction();
        Query q = session.createQuery("select distinct c from Category c order by c.name desc");
        List<Category> categories = (List<Category>)q.list();
        for(Category c : categories) {
            System.out.println(c.getName());
        }
        session.getTransaction().commit();
        session.close();
        
    }
    
    @Test
    public void testHQL_05() {
        Session session = sf.openSession();
        session.beginTransaction();
        /*Query q = session.createQuery("from Category c where c.id > :min and c.id < :max");
        //q.setParameter("min", 2);
        //q.setParameter("max", 8);
        q.setInteger("min", 2);
        q.setInteger("max", 8);*/
        
        Query q = session.createQuery("from Category c where c.id > :min and c.id < :max")
            .setInteger("min", 2)
            .setInteger("max", 8);
        List<Category> categories = (List<Category>)q.list();
        for(Category c : categories) {
            System.out.println(c.getId() + "-" + c.getName());
        }
        session.getTransaction().commit();
        session.close();
        
    }
    
    @Test
    public void testHQL_06() {
        Session session = sf.openSession();
        session.beginTransaction();
        Query q = session.createQuery("from Category c where c.id > ? and c.id < ?");
        q.setParameter(0, 2)
            .setParameter(1, 8);
//        q.setParameter(1, 8);
        List<Category> categories = (List<Category>)q.list();
        for(Category c : categories) {
            System.out.println(c.getId() + "-" + c.getName());
        }
        session.getTransaction().commit();
        session.close();
        
    }
    //分页
    @Test
    public void testHQL_07() {
        Session session = sf.openSession();
        session.beginTransaction();
        Query q = session.createQuery("from Category c order by c.name desc");
        q.setMaxResults(4);
        q.setFirstResult(2);
        List<Category> categories = (List<Category>)q.list();
        for(Category c : categories) {
            System.out.println(c.getId() + "-" + c.getName());
        }
        session.getTransaction().commit();
        session.close();
        
    }
    
    @Test
    public void testHQL_08() {
        Session session = sf.openSession();
        session.beginTransaction();
        Query q = session.createQuery("select c.id,  c.name from Category c order by c.name desc");
        List<Object[]> categories = (List<Object[]>)q.list();
        for(Object[] o : categories) {
            System.out.println(o[0] + "-" + o[1]);
        }
        session.getTransaction().commit();
        session.close();
        
    }
    
    //设定fetch type 为lazy后将不会有第二条sql语句
    @Test
    public void testHQL_09() {
        Session session = sf.openSession();
        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().getName());
        }
        session.getTransaction().commit();
        session.close();
        
    }
    
    //设定fetch type 为lazy后将不会有第二条sql语句
    @Test
    public void testHQL_10() {
        Session session = sf.openSession();
        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());
        }
        session.getTransaction().commit();
        session.close();
        
    }
    
    @Test
    public void testHQL_11() {
        Session session = sf.openSession();
        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(m.getCont());
        }
        session.getTransaction().commit();
        session.close();
        
    }
    //了解即可
    //VO Value Object
    //DTO data transfer object
    @Test
    public void testHQL_12() {
        Session session = sf.openSession();
        session.beginTransaction();
        Query q = session.createQuery("select new com.bjsxt.hibernate.MsgInfo(m.id, m.cont, m.topic.title, m.topic.category.name) from Msg");
        
        for(Object o : q.list()) {
            MsgInfo m = (MsgInfo)o;
            System.out.println(m.getCont());
        }
        session.getTransaction().commit();
        session.close();
        
    }
    
    //动手测试left right join
    //为什么不能直接写Category名，而必须写t.category
    //因为有可能存在多个成员变量（同一个类），需要指明用哪一个成员变量的连接条件来做连接
    @Test
    public void testHQL_13() {
        Session session = sf.openSession();
        session.beginTransaction();
        Query q = session.createQuery("select t.title, c.name from Topic t join t.category c "); //join Category c
        for(Object o : q.list()) {
            Object[] m = (Object[])o;
            System.out.println(m[0] + "-" + m[1]);
        }
        session.getTransaction().commit();
        session.close();
        
    }
    
    //学习使用uniqueResult
    @Test
    public void testHQL_14() {
        Session session = sf.openSession();
        session.beginTransaction();
        Query q = session.createQuery("from Msg m where m = :MsgToSearch "); //不重要
        Msg m = new Msg();
        m.setId(1);
        q.setParameter("MsgToSearch", m);
        
        Msg mResult = (Msg)q.uniqueResult();
        System.out.println(mResult.getCont());
        session.getTransaction().commit();
        session.close();
        
    }
    
    @Test
    public void testHQL_15() {
        Session session = sf.openSession();
        session.beginTransaction();
        Query q = session.createQuery("select count(*) from Msg m");
        
        long count = (Long)q.uniqueResult();
        System.out.println(count);
        session.getTransaction().commit();
        session.close();
        
    }
    
    @Test
    public void testHQL_16() {
        Session session = sf.openSession();
        session.beginTransaction();
        Query q = session.createQuery("select max(m.id), min(m.id), avg(m.id), sum(m.id) from Msg m");
        
        Object[] o = (Object[])q.uniqueResult();
        System.out.println(o[0] + "-" + o[1] + "-" + o[2] + "-" + o[3]);
        session.getTransaction().commit();
        session.close();
        
    }
    
    @Test
    public void testHQL_17() {
        Session session = sf.openSession();
        session.beginTransaction();
        Query q = session.createQuery("from Msg m where m.id between 3 and 5");
        
        for(Object o : q.list()) {
            Msg m = (Msg)o;
            System.out.println(m.getId() + "-" + m.getCont());
        }
        session.getTransaction().commit();
        session.close();
        
    }
    
    @Test
    public void testHQL_18() {
        Session session = sf.openSession();
        session.beginTransaction();
        Query q = session.createQuery("from Msg m where m.id in (3,4, 5)");
        
        for(Object o : q.list()) {
            Msg m = (Msg)o;
            System.out.println(m.getId() + "-" + m.getCont());
        }
        session.getTransaction().commit();
        session.close();
        
    }
    
    //is null 与 is not null
    @Test
    public void testHQL_19() {
        Session session = sf.openSession();
        session.beginTransaction();
        Query q = session.createQuery("from Msg m where m.cont is not null");
        
        for(Object o : q.list()) {
            Msg m = (Msg)o;
            System.out.println(m.getId() + "-" + m.getCont());
        }
        session.getTransaction().commit();
        session.close();
        
    }
    

/is empty and is not empty
    @Test
    public void testHQL_20() {
        Session session = sf.openSession();
        session.beginTransaction();
        Query q = session.createQuery("from Topic t where t.msgs is empty");
        
        for(Object o : q.list()) {
            Topic t = (Topic)o;
            System.out.println(t.getId() + "-" + t.getTitle());
        }
        session.getTransaction().commit();
        session.close();
        
    }
    
    @Test
    public void testHQL_21() {
        Session session = sf.openSession();
        session.beginTransaction();
        Query q = session.createQuery("from Topic t where t.title like '%5'");
        
        for(Object o : q.list()) {
            Topic t = (Topic)o;
            System.out.println(t.getId() + "-" + t.getTitle());
        }
        session.getTransaction().commit();
        session.close();
        
    }
    
    @Test
    public void testHQL_22() {
        Session session = sf.openSession();
        session.beginTransaction();
        Query q = session.createQuery("from Topic t where t.title like '_5'");
        
        for(Object o : q.list()) {
            Topic t = (Topic)o;
            System.out.println(t.getId() + "-" + t.getTitle());
        }
        session.getTransaction().commit();
        session.close();
        
    }
    //不重要
    @Test
    public void testHQL_23() {
        Session session = sf.openSession();
        session.beginTransaction();
        Query q = session.createQuery("select lower(t.title)," +
                                             "upper(t.title)," +
                                             "trim(t.title)," +
                                             "concat(t.title, '***')," +
                                             "length(t.title)" +
                                             " from Topic t ");
        
        for(Object o : q.list()) {
            Object[] arr = (Object[])o;
            System.out.println(arr[0] + "-" + arr[1] + "-" + arr[2] + "-" + arr[3] + "-" + arr[4] + "-");
        }
        session.getTransaction().commit();
        session.close();
        
    }
    
    @Test
    public void testHQL_24() {
        Session session = sf.openSession();
        session.beginTransaction();
        Query q = session.createQuery("select abs(t.id)," +
                                             "sqrt(t.id)," +
                                             "mod(t.id, 2)" +
                                             " from Topic t ");
        
        for(Object o : q.list()) {
            Object[] arr = (Object[])o;
            System.out.println(arr[0] + "-" + arr[1] + "-" + arr[2] );
        }
        session.getTransaction().commit();
        session.close();
        
    }
    
    @Test
    public void testHQL_25() {
        Session session = sf.openSession();
        session.beginTransaction();
        Query q = session.createQuery("select current_date, current_time, current_timestamp, t.id from Topic t");
        
        for(Object o : q.list()) {
            Object[] arr = (Object[])o;
            System.out.println(arr[0] + " | " + arr[1] + " | " + arr[2] + " | " + arr[3]);
        }
        session.getTransaction().commit();
        session.close();
        
    }
    
    @Test
    public void testHQL_26() {
        Session session = sf.openSession();
        session.beginTransaction();
        Query q = session.createQuery("from Topic t where t.createDate < :date");
        q.setParameter("date", new Date());
        for(Object o : q.list()) {
            Topic t = (Topic)o;
            System.out.println(t.getTitle());
        }
        session.getTransaction().commit();
        session.close();
        
    }
    
    @Test
    public void testHQL_27() {
        Session session = sf.openSession();
        session.beginTransaction();
        Query q = session.createQuery("select t.title, count(*) from Topic t group by t.title") ;
        for(Object o : q.list()) {
            Object[] arr = (Object[])o;
            System.out.println(arr[0] + "|" + arr[1]);
        }
        session.getTransaction().commit();
        session.close();
        
    }
    
    @Test
    public void testHQL_28() {
        Session session = sf.openSession();
        session.beginTransaction();
        Query q = session.createQuery("select t.title, count(*) from Topic t group by t.title having count(*) >= 1") ;
        for(Object o : q.list()) {
            Object[] arr = (Object[])o;
            System.out.println(arr[0] + "|" + arr[1]);
        }
        session.getTransaction().commit();
        session.close();
        
    }
    
    @Test
    public void testHQL_29() {
        Session session = sf.openSession();
        session.beginTransaction();
        Query q = session.createQuery("from Topic t where t.id < (select avg(t.id) from Topic t)") ;
        for(Object o : q.list()) {
            Topic t = (Topic)o;
            System.out.println(t.getTitle());
        }
        session.getTransaction().commit();
        session.close();
        
    }
    
    @Test
    public void testHQL_30() {
        Session session = sf.openSession();
        session.beginTransaction();
        Query q = session.createQuery("from Topic t where t.id < ALL (select t.id from Topic t where mod(t.id, 2)= 0) ") ;
        for(Object o : q.list()) {
            Topic t = (Topic)o;
            System.out.println(t.getTitle());
        }
        session.getTransaction().commit();
        session.close();
        
    }
    
    //用in 可以实现exists的功能
    //但是exists执行效率高
    @Test
    public void testHQL_31() {
        Session session = sf.openSession();
        session.beginTransaction();// t.id not in (1)
        Query q = session.createQuery("from Topic t where not exists (select m.id from Msg m where m.topic.id=t.id)") ;
//        Query q = session.createQuery("from Topic t where exists (select m.id from Msg m where m.topic.id=t.id)") ;
        for(Object o : q.list()) {
            Topic t = (Topic)o;
            System.out.println(t.getTitle());
        }
        session.getTransaction().commit();
        session.close();
        
    }
    
    //update and delete
    //规范并没有说明是不是要更新persistent object，所以如果要使用，建议在单独的trasaction中执行
    
    @Test
    public void testHQL_32() {
        Session session = sf.openSession();
        session.beginTransaction();
        Query q = session.createQuery("update Topic t set t.title = upper(t.title)") ;
        
        q.executeUpdate();
        q = session.createQuery("from Topic");
        for(Object o : q.list()) {
            Topic t = (Topic)o;
            System.out.println(t.getTitle());
        }
        session.createQuery("update Topic t set t.title = lower(t.title)")
            .executeUpdate();
        session.getTransaction().commit();
        session.close();
        
    }
    
    //不重要
    @Test
    public void testHQL_33() {
        Session session = sf.openSession();
        session.beginTransaction();
        Query q = session.getNamedQuery("topic.selectCertainTopic");
        q.setParameter("id", 5);
        Topic t = (Topic)q.uniqueResult();
        System.out.println(t.getTitle());
        session.getTransaction().commit();
        session.close();
        
    }
    
    //Native（了解）
    @Test
    public void testHQL_34() {
        Session session = sf.openSession();
        session.beginTransaction();
        SQLQuery q = session.createSQLQuery("select * from category limit 2,4").addEntity(Category.class);
        List<Category> categories = (List<Category>)q.list();
        for(Category c : categories) {
            System.out.println(c.getName());
        }
        session.getTransaction().commit();
        session.close();
        
    }
    

QBC

@Test
    public void testQBC() {
        Session session = sf.openSession();
        session.beginTransaction();
        //criterion 标准/准则/约束
        Criteria c = session.createCriteria(Topic.class) //from Topic
                     
                     .add(Restrictions.gt("id", 2)) //greater than = id > 2
                     .add(Restrictions.lt("id", 8)) //little than = id < 8
                     .add(Restrictions.like("title", "t_"))
                     .createCriteria("category")
                     .add(Restrictions.between("id", 3, 5)) //category.id >= 3 and category.id <=5
                     ;
        //DetachedCriterea
        for(Object o : c.list()) {
            Topic t = (Topic)o;
            System.out.println(t.getId() + "-" + t.getTitle());
        }
        session.getTransaction().commit();
        session.close();
        
    }
    

QBE

@Test
    public void testQBE() {
        Session session = sf.openSession();
        session.beginTransaction();
        Topic tExample = new Topic();
        tExample.setTitle("T_");
        
        Example e = Example.create(tExample)
                    .ignoreCase().enableLike();
        Criteria c = session.createCriteria(Topic.class)
                     .add(Restrictions.gt("id", 2))
                     .add(Restrictions.lt("id", 8))
                     .add(e)
                     ;
                     
        
        for(Object o : c.list()) {
            Topic t = (Topic)o;
            System.out.println(t.getId() + "-" + t.getTitle());
        }
        session.getTransaction().commit();
        session.close();
        
    }