Hibernate QBC语言

节 8.01    基本查询
以下是HQL/QBC/Native SQL三种查询策略
HQL策略：

session.createQuery("FROM Category c where c.name like 'Laptop%'");

 

QBC策略：

session.createCriteria(Category.class).add(Restrictions.like("name", "Laptop%"));

 

Native SQL策略

session.createSQLQuery("select {c.*} from CATEGORY {c} where NAME like 'Laptop%'").
addEntity("c",Category.class);

 

节 8.02    分页查询

Criteria criteria = session.createCriteria(Category.class)
.add(Restrictions.like("name", "Laptop%"));
criteria.addOrder(Order.asc("name"));
criteria.setFirstResult();//初始行数
criteria.setMaxResults(20);//每页显示行数

 

节 8.03    数据过滤
方法                      说明    
Restrictions.eq         =   
Restrictions.allEq      利用Map来进行多个等于的限制    
Restrictions.gt         >    
Restrictions.ge         >=    
Restrictions.lt         <  
Restrictions.le         <=    
Restrictions.between    BETWEEN   
Restrictions.like       LIKE   
Restrictions.in         in   
Restrictions.and        and   
Restrictions.or         or   
Restrictions.sqlRestriction     用SQL限定查询
(a)    应用限制

Criterion emailEq = Restrictions.eq("email", "[email protected]");
Criteria criteria = session.createCriteria(User.class);
criteria.add(emailEq);
User user = (User)criteria.uniqueResult();

 

(b)    比较表达式

Restrictions.between("amount", new BigDecimal(100), new BigDecimal(200));
Restrictions.gt("amount", new BigDecimal(100));
Restrictions.in("email", emails);//注：emails为集合
Restrictions.isNull("email");
Restrictions.isNotNull("email");
Restrictions.isEmpty("bids");
Restrictions.sizeGe("bids", 3);//bids属性大小

 

(c)    字符串匹配

Restrictions.like("email", "G%");
Restrictions.like("email", "G%",MatchMode.START);
注：MatchMode分为START,END,ANYWHERE,EXACT四种模式
Restrictions.like("email", "G%").ignoreCase();

 

(d)    组合表达式和逻辑操作符

Restrictions.or(
                Restrictions.and(
                        Restrictions.like("firstname", "G%"),
                        Restrictions.like("lastname", "K%")),
                        Restrictions.in("email",emails));

 

(e)    SQL表达式

Restrictions.sqlRestriction("{alias}.name='tie' and {alias}.addr='dalian'");
Restrictions.sqlRestriction("{alias}.name=?",  "tie", Hibernate.STRING);//姓名为tie的对象
Restrictions.sqlRestriction("length({alias}.PASSWORD) < ?",5,Hibernate.INTEGER);
//密码小于5个字符对象
Restrictions.sqlRestriction("'100' >all( select b.AMOUNT FROM BID b " +
                " WHERE b.ITEM_ID = {alias}.ITEM_ID)");//返回出价不大于100

 

(f)    子查询

节 8.04    表关联
(a)    隐式关联
隐式关联有两种方法：
1、    Criteria接口的createCriteria()方法：

session.createCriteria(Item.class)
.add(Restrictions.like("description", "Foo",MatchMode.ANYWHERE))
.createCriteria("bids")
.add(Restrictions.gt("amount",new BigDecimal(100)));

session.createCriteria(Item.class)
            .createCriteria("seller")
            .add(Restrictions.like("email", "%@"));

 

2、    分配别名：

session.createCriteria(Item.class)
            .createAlias("bids","b")
            .add(Restrictions.like("description", "%Foo%"))
            .add(Restrictions.gt("b.amount", new BigDecimal(100)));

session.createCriteria(Item.class)
            .createAlias("seller", "s")
            .add(Restrictions.like("s.email","%@"));

 

(b)    抓取关联

session.createCriteria(Item.class)
            .setFetchMode("bids",FetchMode.JOIN)
            .add(Restrictions.like("description", "%Foo%"))

 

节 8.05    投影/报表查询
(a)    简单投影

session.createCriteria(Item.class)
        .add(Restrictions.gt("endDate", new Date()))
        .setProjection(Projections.id());//返回单一属性

session.createCriteria(Item.class).setProjection(
Projections.projectionList().add(Projections.id()).
add(Projections.property("description")));//返回一个Object[]

 

(b)    统计分组

session.createCriteria(Item.class)
.setProjection(Projections.rowCount());

session.createCriteria(Item.class)
            .setProjection(Projections.projectionList()
            .add(Projections.rowCount())
            .add(Projections.sum("sales"))
            .add(Projections.avg("score"))
            );

    session.createCriteria(Bid.class)
        .createAlias("bidder", "u")
        .setProjection(Projections.projectionList()
                .add(Property.forName("u.id").group())
                .add(Property.forName("u.username").group())
                .add(Property.forName("id").count())
                .add(Property.forName("amount").avg())
            );

 

(c)    SQL投影

String sqlFragment = "(select count(*) from Item i where i.item_id = item_id) "
                + " as numofitems";
        session.createCriteria(Bid.class).createAlias("bidder", "u")
                .setProjection(
                        Projections.projectionList().add(
                                Projections.groupProperty("u.id")).add(
                                Projections.groupProperty("u.username")).add(
                                Projections.count("id")).add(
                                Projections.avg("amount")).add(
                                Projections.sqlProjection(sqlFragment,
                                        new String[] { "numofitems" },
                                        new Type[] { Hibernate.LONG }))

                );