Hibernate 3.2 学习笔记 查询和检索

Hibernate的检索策略
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检索策略的作用域 可用策略 默认 运行时受影响的方法

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类级别 立即检索 立即 load()
延时检索

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关联级别 立即检索 多对一和一对一 load() get() 等
延时检索 为外连接检索
迫切左外连接检索 -------------
一对多和多对多
为立即检索
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立即检索 类级别的立即加载关联对象 关联级别的立即加载指定对象的关联对象 可以设定批量检索数量

延时检索 类级别的延时加载关联对象 关联级别的延时加载指定对象的关联对象 可以设定批量检索数量
迫切左外连接检索 类级别不适用 关联级别通过左外连接加载与检索方法指定对象关联的对象

涉及到的元素属性
<class>和<set>的lazy 默认是true 表示延时检索
<many-to-one><one-to-one><set> 的 outer-join <many-to-one><one-to-one>默认auto <set> 默认 false
<class>和<set> 的batch-size 默认1 指定批量检索的数量

' 延时检索时会产生代理类
' 但是仅仅初始化了OID 其他都为null
' 只有当访问除ID外的属性 或者修改时才会加载数据库的数据
' 有可能在你关闭session后仍没有初始化对象 也就没有完整的游离对象
' 只有在session范围内才能被初始化
' get()方法加载的对象时实际相关数据 不是代理类

一对多和多对多的检索策略
<set> 的lazy和out-join
都为false 立即检索
lazy为false out-join为true是迫切左外连接检索(当有多个<set>只允许一个用)
相反时 用延时检索策略

Hibernate的检索方式

HQL检索方式：
1 通过Session的createQuery()方法创建一个Query对象 包含一HQL查询语句
2 可以动态绑定参数
3 可以调用list()方法返回List类型的结果
exp :
List result = session.createQuery(".......").setString("name",name).setInteger("age", 21).list();

QBC检索方式：
1 用session的才createCriteria()方法创建一个Criteria对象
2 可以设定查询的条件 用Expression的一些静态方法 如Expression.like("name", "T%")
Expression.eq("age", new Integer(21)
3 可以使用方法链 也可以调用list()方法返回List类型的结果
exp :
List result = session.createCriteria(Customer.class).add(Restrictions.like("name", "T%")).add(Restrictions.eq("age", new Integer(21)).list();
4 还可以使用QBE模板检索方式
exp :
Customer exp = new Customer();
exp.setName("tom");

List result =session.createCriteria(Customer.class).add(Example.create(exp)).list();

SQL检索方式：

Query query=session.createSQLQuery("..............");

由于检索和HQL比较杂乱分别举例说明

' 最简单的查询

HQL


Session session=sessionFactory.openSession();


Transaction tx=null;


try




...{


tx=session.beginTransaction();




List result=session.createQuery("from Customer ").list();


for(Iterator it=result.iterator(); it.hasNext();)




...{


Customer c =(Customer)it.next();


System.out.println("Customer's name :" + c.getName());


System.out.println("Customer's age :" + c.getAge());


}


tx.commit();


}


catch(Exception e)




...{


if(tx!=null)




...{


tx.rollback();


}


throw e;


}

BQC


...


List result=session.createCriteria(Customer.class).list();


...

' 指定查询和命名别名

HQL


...


List result=session.createQuery("from Customer as c where name=:name").setString("name", "Tom").list();


...

BQC


...


List result=session.createCriteria(Customer.class).add(Restrictions.eq("name", "Tom")).list();


...

' 对查询结果排序

desc是降序

HQL


...


List result=session.createQuery("from Customer as c order by c.name").list();


List result=session.createQuery("from Customer as c order by c.name asc, c.age desc").list();


...

BQC


...


List result=session.createCriteria(Customer.class).addOrder(Order.asc("name")).addOrder(Order.desc("age")).list();


...

' 在指定时间范围内查询结果


...


tx=session.beginTransaction();


Date beginDate=java.sql.Date.valueOf("2006-8-1");


Date endDate=java.sql.Date.valueOf("2006-9-1");


List result=session.createQuery("from Customer c where c.retime <:endTime and c.retime >=:beginTime").setTimestamp("endTime", endDate).setTimestamp("beginTime", beginDate).list();


...

' 分页查询

HQL


...


List result=session.createQuery("from Customer c Order by c.name asc").setFirstResult(0).setMaxResults(3).list();


...

BQC


...


List result=session.createCriteria(Customer.class).addOrder(Order.asc("name")).setFirstResult(0).setMaxResults(3).list();


...

' 检索单个对象

uniqueResult() 方法
如果不确定返回的时单个对象先用Query和Criteria的serMaxResult(1)方法 设定只返回一个对象

如果确定只返回一个对象 比如from Customer c where c.id＝1

' HQL的两种绑定查询

1


session.createQuery("from Customer c where c.name=:name and c.age=:age").setString("name", "tom").setInteger("age", 20)

2


session.createQuery("from Customer c where c.name=? and c.age=?").setString(0, "tom").setInteger(1, 20)

' 特殊绑定方法

1
setEntity() 可以绑定实体对象


session.createQuery("from Order o where o.customer=:customer").setEntity("customer", customer)

2
setParameter 绑定任意类型的参数


Query query=session.createQuery("from Order o where o.customer=:customer and o.orderNumber like: orderNumber ");


query.setParameter("customer", customer, Hibernate.entity(Customer.class));


query.setParameter("orderNumber", orderNumber, Hibernate.STRING)；

3
setProperties() 与一个对象的属性绑定


Customer customer = new Customer();


customer.setName("Tom");


customer.setAge(21);


List result=session.createQuery("from Customer c where c.name=:name and c.age=:age").setProperties(customer).list();

' 设定查询条件

' 比较运算 大于某个条件
HQL


...


List result=session.createQuery("from Customer c where c.age>23").list();


...

BQC


...


List result=session.createCriteria(Customer.class).add(Restrictions.gt("age", new Integer(23))).list();


...

' 比较运算 不等于某个条件

HQL


...


List result=session.createQuery("from Customer c where c.age<>24").list();


...

BQC


...


List result=session.createCriteria(Customer.class).add(Restrictions.not(Restrictions.eq("age", new Integer(23)))).list();


...

' 比较运算 条件为null的某个对象

HQL


...


List result=session.createQuery("from Order o where o.customer is null").list();


...

BQC


...


List result=session.createCriteria(Order.class)


.add(Restrictions.isNull("customer")).list();


...

' 范围运算 检索在某个范围内String

HQL


...


List result=session.createQuery("from Customer c where c.name in('Tom','Mike','Jack')").list();


...

BQC


...




String[] names=...{"Tom", "Mike", "Jack"};


List result=session.createCriteria(Customer.class)


.add(Restrictions.in("name", names)).list();


...

' 范围运算 检索在某个范围内Integer

HQL




...


List result=session.createQuery("from Customer c where c.age between 24 and 30").list();


...



BQC


...


List result=session.createCriteria(Customer.class)


.add(Restrictions.between("age", new Integer(24), new Integer(30))).list();


...

不在某个范围内

HQL


...


List result=session.createQuery("from Customer c where c.age not between 24 and 30").list();


...

BQC


...


List result=session.createCriteria(Customer.class)


.add(Restrictions.not(Restrictions.between("age", new Integer(24), new Integer(30)))).list();


...

' 范围运算 字符串通配符

以 T 开头
HQL like 'T%'
BQC add(Restrictions.like("name","T%"))

以 T 结尾
HQL like '%T'
BQC add(Restrictions.like("name","%T"))

包含 T
HQL like '%T%'
BQC add(Restrictions.like("name","%T%"))

控制长度为3
HQL like 'T_ _'
BQC add(Restrictions.like("name","T_ _"))

另外
Restrictions 还有这样的方法like(java.lang.String propertyName, java.lang.String value, MatchMode matchMode)
有一些定义好的field 具体查看API

' 逻辑运算 检索 复杂条件

条件结合
HQL


...


List result=session.createQuery("from Customer c where c.name like 'T%' and c.name like '%m'").list();


...

BQC


...


List result=session.createCriteria(Customer.class)


.add(Restrictions.like("name", "T%")).add(Restrictions.like("name", "%m")).list();


...

逻辑与
Restriction有如下方法
or(Criterion lhs, Criterion rhs)
and(Criterion lhs, Criterion rhs

HQL


...


List result=session.createQuery("from Customer c where (c.name like 'T%' and c.name like '%m') or (c.age not between 20 and 25)").list();


...

BQC


...


List result=session.createCriteria(Customer.class).add(Restrictions.or(Restrictions.and(Restrictions.like("name", "T%"), Restrictions.like("name", "%m")), Restrictions.not(Restrictions.between("age", new Integer(20), new Integer(25))))).list();


...

' 报表查询

from 关键字是必须 select group by having 用于报表查询

投影查询 只检索出需要的字段

HQL


...


List result=session.createQuery("select c.id, c.name, o.orderNumber from Customer c join c.orders o where o.orderNumber like 'T%'").list();


Iterator it=result.iterator();


while(it.hasNext())




...{


Object[] row=(Object[])it.next();


Long id=(Long)row[0];


String name=(String)row[1];


String orderNumber=(String)row[2];


System.out.println(id+" "+name+" "+orderNumber);


}


...

这个list返回的结果是集合 存放的是关系数据
也可以建立一个javabean来让结果更清晰


...


select new ergal.CustomerRow(c.id, c.name, o.orderNumber) from Customer c join c.orders o where o.orderNumber like 'T%'


...




while(it.hasNest())




...{


CustomerRow cr=(CustomerRow)it.next();


Long id=(Long)cr.getId();


......


}

' 分组查询

查询相同姓名的的记录


...


List result=session.createQuery("select c.name, count(c) from Customer c group by c.name").list();


Iterator it=result.iterator();


while(it.hasNext())




...{


Object[] row=(Object[])it.next();


String name=(String)row[0];


Long id=(Long)row[1];


System.out.println(id+" "+name);


}


...

统计订单数目


...


List result=session.createQuery("select c.id, c.name, count(o) from Customer c join c.orders o group by c.id").list();


Iterator it=result.iterator();


while(it.hasNext())




...{


Object[] row=(Object[])it.next();


Long id=(Long)row[0];


String name=(String)row[1];


Long num=(Long)row[2];


System.out.println(num+" "+name+" "+id);


}


...

统计每个客户的订单总价-右外连接


...


List result=session.createQuery("select c.id, c.name, sum(o.price) from Customer c right outer join c.orders o group by c.id").list();


Iterator it=result.iterator();


while(it.hasNext())




...{


Object[] row=(Object[])it.next();


Long id=(Long)row[0];


String name=(String)row[1];


Double num=(Double)row[2];


System.out.println(num+" "+name+" "+id);


}


...

统计每个客户的订单总价-加条件 订单大于一的


...


List result=session.createQuery("select c.id, c.name, sum(o.price) from Customer c join c.orders o group by c.id having(count(o)>1)").list();


Iterator it=result.iterator();


while(it.hasNext())




...{


Object[] row=(Object[])it.next();


Long id=(Long)row[0];


String name=(String)row[1];


Double num=(Double)row[2];


System.out.println(num+" "+name+" "+id);


}


...

查询时间段


tx=session.beginTransaction();


Date beginDate=java.sql.Date.valueOf("2006-8-1");


Date endDate=java.sql.Date.valueOf("2006-9-1");


List result=session.createQuery("from Customer c where c.retime <:endTime and c.retime >=:beginTime").setTimestamp("endTime", endDate).setTimestamp("beginTime", beginDate).list();


for(Iterator it=result.iterator(); it.hasNext();)




...{


Customer c =(Customer)it.next();


System.out.println("Customer's name :" + c.getName());


System.out.println("Customer's regiestertime :" + c.getRetime());


}

总的来说就是将显示时间 和 数据库的时间都进行转化 然后进行比较

还有别的方式