Hibernate的查询方式

Hibernate的查询方式有：

 

1.使用主键id加载对象(load(),get());

2.通过对象导航,比如通过stu.getTeam()得到team的实例;

3.使用hql;

4.使用qbc(query by criteria)

5.直接使用sql语句取得记录集;

一般都使用后面三种方式.

注意.hql是面向对象的查询.语法和sql是基本一样的.不区分大小写的,但是注意的是对与对象.必须遵循对象的大小写.因为hql是对像查询..同时我们必须清楚.hql只能取得对象,而不支持uid(update,insert.delete)

 

 

HQL功能最强大，适合各种情况，但是动态条件查询构造起来很不方便
Criteria最适合动态条件查询，不太适合统计查询，QBE还不够强大，只适合相当简单的查询
NativeSQL可以实现特定数据库的SQL，但是可移植性就牺牲了

Hibernate2的Criteria功能不够完善，所以Hibernate2上面可用的只有HQL和NativeSQL，Hibernate3的Criteria已经非常强大了。

针对web应用来说，大部分常规查询都是动态条件查询，所以首选使用Criteria，并且Hibernate3提供了DetachedCriteria，可以在web层构造好DetachedCriteria再进入session执行查询，非常方便实用的特性。

但是涉及到统计查询和非常复杂的关联查询，Criteria就无能为力了，这种情况下我选择使用HQL。

 

 

 

以下是HQL/QBC/Native SQL三种查询策略
HQL策略：

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

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

QBC策略：

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

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

Native SQL策略

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

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

节 8.02    分页查询

Java代码
Criteria criteria = session.createCriteria(Category.class)  
.add(Restrictions.like("name", "Laptop%"));  
criteria.addOrder(Order.asc("name"));  
criteria.setFirstResult(0);//初始行数  
criteria.setMaxResults(20);//每页显示行数 

Criteria criteria = session.createCriteria(Category.class)
.add(Restrictions.like("name", "Laptop%"));
criteria.addOrder(Order.asc("name"));
criteria.setFirstResult(0);//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

Java代码
Criterion emailEq = Restrictions.eq("email", "[e-mail]");  
Criteria criteria = session.createCriteria(User.class);  
criteria.add(emailEq);  
User user = (User)criteria.uniqueResult(); 

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

(b)    比较表达式

Java代码
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 

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

Java代码
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(); 

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

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

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

(e)    SQL表达式

Java代码
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 

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：

Java代码
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", "%@")); 

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：

Java代码
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","%@")); 

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

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

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

Java代码
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[] 

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

Java代码
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())  
            ); 

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

Java代码
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 }))  
 
                ); 

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2 楼 Leisurez 2014-02-10  

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1 楼 Leisurez 2014-02-10  

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