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Posted on 2007-11-12 16:29 G_G 阅读(2067) 评论(3) 编辑 收藏 所属分类: hibernate
缓存问题：
/**
使用 Query.executeUpdate() 缓存中数据不同步 解决办法
* Table -> T1oo(id,name)
* Table -> T2oo(id,avg,aid)
* 外键 T1oo.id->T2oo.aid
* Session.createQuery("delete T1oo") -> Query.executeUpdate()
*/
public
void
testExecuteUpdate(){
System.out.println(
"
\r\n\r\n********************ExecuteUpdate************************
"
);
T1oo t1oo
=
new
T1oo();
t1oo.setName(
"
liukaiyi
"
);
HibernateSessionFactory.closeSession();
Session session
=
HibernateSessionFactory.currentSession();
Transaction tr1
=
session.beginTransaction();
//
t1 成为 持久状态 一级缓存中 加载
session.saveOrUpdate(t1oo);
//
直接一条语句删除T1oo，缓存无法同步
//
一级缓存中还有 t1
Query qu
=
session.createQuery(
"
delete T1oo
"
);
try
{
qu.executeUpdate();
}
catch
(Exception e) {
System.out.println(
"
//err: 有级联 单使用 delete T1oo 还要delete T2oo.aid = T1oo.id//
"
);
List list
=
session.createQuery(
"
from T1oo
"
).list();
for
(Iterator it
=
list.iterator();it.hasNext();){
Query t2qu
=
session.createQuery(
"
delete T2oo where aid=:id
"
);
t2qu.setInteger(
"
id
"
, ((T1oo)it.next()).getId().intValue());
t2qu.executeUpdate();
}
qu.executeUpdate();
}
tr1.commit();
Transaction tr2
=
session.beginTransaction();
//
这直接通过一级缓存中加载t2，但DB中以没有此条数据
t1oo
=
(T1oo)session.load(T1oo.
class
,t1oo.getId());
t1oo.setName(
"
google
"
);
try
{
tr2.commit();
}
catch
(Exception e) {
System.out.println(
"
//err: update(t1oo)->DB 中数据库中没有 t1oo //
"
);
}
System.out.println(
"
一级缓存清空前
"
+
session.get(T1oo.
class
,t1oo.getId()) );
session.evict(t1oo);
System.out.println(
"
一级缓存清空后
"
+
session.get(T1oo.
class
,t1oo.getId()) );
//
不把t1oo id 为空，否则当在saveOrUpdate时候就会以为是游离态 update了
t1oo.setId(
null
);
//
id=null insert 调用
session.saveOrUpdate(t1oo);
tr2.commit();
Transaction tr3
=
session.beginTransaction();
session.delete(t1oo);
tr3.commit();
session.close();
HibernateSessionFactory.closeSession();
}
结果是：
********************ExecuteUpdate************************
log4j:WARN No appenders could be found for logger (org.hibernate.cfg.Environment).
log4j:WARN Please initialize the log4j system properly.
Hibernate: insert into t1oo (name, id) values (?, ?)
Hibernate: delete from t1oo
//err: 有级联 单使用 delete T1oo 还要delete T2oo.aid = T1oo.id//
Hibernate: select t1oo0_.id as id, t1oo0_.name as name0_ from t1oo t1oo0_
Hibernate: delete from t2oo where aid=?
Hibernate: delete from t2oo where aid=?
Hibernate: delete from t2oo where aid=?
Hibernate: delete from t1oo
Hibernate: update t1oo set name=? where id=?
//err: update(t1oo)->DB 中数据库中没有 t1oo //
一级缓存清空前 hbn.bean.T1oo@287
Hibernate: select t1oo0_.id as id0_, t1oo0_.name as name0_0_ from t1oo t1oo0_ where t1oo0_.id=?
一级缓存清空后 null
Hibernate: insert into t1oo (name, id) values (?, ?)
Hibernate: delete from t1oo where id=?
Get Load 区别 ：
/** Get Load 区别 (在commit前要 session.flush())
* Table -> T1oo(id,name)
* 1.如果未能发现符合条件的记录，get方法返回null，而load方法会抛出异常
* 2.Load方法可返回实体的代理类实例，而get方法永远直接返回实体类。
* 3.load方法可以充分利用内部缓存和二级缓存中的现有数据，而get方法则仅仅在内部缓存中进行数据查找，
* 如没有发现对应数据，将越过二级缓存，直接调用SQL完成数据读取。
*/
public void testGetLoad() throws Exception {
System.out.println("\r\n\r\n********************Get<>Load************************");
Session session = HibernateSessionFactory.currentSession();
// 数据准备
T1oo t1oo = new T1oo();
t1oo.setName("liu");
Transaction t1 = session.beginTransaction();
session.saveOrUpdate(t1oo);
// 为什么这会错？
//session.evict(t1oo);
//session.flush();
t1.commit();
session.evict(t1oo);
Transaction t2 = session.beginTransaction();
System.out.println("一级缓存是否有t1oo(load)->"+session.contains(t1oo));
//这时候t1oo为 CGlib生成的代理类
t1oo = (T1oo)session.load(T1oo.class,t1oo.getId());
System.out.println(" 延迟加载出现：select.. t1oo0_.id=? 表的其他属性加载 ");
t1oo.setName("load list");
//后在 update
t2.commit();
session.evict(t1oo);
Transaction t3 = session.beginTransaction();
System.out.println("一级缓存是否有t1oo(get)->"+session.contains(t1oo));
//这时候t1oo为 CGlib生成的代理类
t1oo = (T1oo)session.get(T1oo.class,t1oo.getId());
System.out.println(" 没有延迟加载出现");
t1oo.setName("get list");
//后在 update
t3.commit();
session.evict(t1oo);
Transaction tr3 = session.beginTransaction();
session.delete(t1oo);
tr3.commit();
session.close();
HibernateSessionFactory.closeSession();
}
结果
********************Get<>Load************************
Hibernate: insert into t1oo (name, id) values (?, ?)
一级缓存是否有t1oo(load)->false
延迟加载出现：select.. t1oo0_.id=? 表的其他属性加载
Hibernate: select t1oo0_.id as id0_, t1oo0_.name as name0_0_ from t1oo t1oo0_ where t1oo0_.id=?
Hibernate: update t1oo set name=? where id=?
一级缓存是否有t1oo(get)->false
Hibernate: select t1oo0_.id as id0_, t1oo0_.name as name0_0_ from t1oo t1oo0_ where t1oo0_.id=?
没有延迟加载出现
Hibernate: update t1oo set name=? where id=?
Hibernate: select t2ooset0_.aid as aid1_, t2ooset0_.id as id1_, t2ooset0_.id as id0_, t2ooset0_.avg as avg1_0_, t2ooset0_.aid as aid1_0_ from t2oo t2ooset0_ where t2ooset0_.aid=?
Hibernate: delete from t1oo where id=?
Set 集合的识别：
/** Set 集合的识别
* Table -> T1oo(id,name)
* Table -> T2oo(id,avg,aid)
* 外键 T1oo.id->T2oo.aid
* T1oo <set name="t2ooSet" inverse="false" cascade = "all" >
* T2oo <many-to-one name="t1oo" column="aid" class="T1oo" />
* cascade='insert' 是一定要的
* 当 T1oo没有 inverse="true" 主动权的时候，要双项关联
* t1oo.getT2ooSet().add(t2oo1);
* t1oo.getT2ooSet().add(t2oo2);
* t2oo1.setT1oo(t1oo);
* t2oo2.setT1oo(t1oo);
* 要不后sql为：
* Hibernate: insert into t2oo (avg, aid, id) values (?, ?, ?)
* Hibernate: insert into t2oo (avg, aid, id) values (?, ?, ?)
* +----+-----+------+
* | id | avg | aid |
* +----+-----+------+
* | 1 | 24 | NULL |
* | 2 | 23 | NULL |
* +----+-----+------+
* 当 T1oo有 inverse="false"主动权的时候
* t1oo.getT2ooSet().add(t2oo1);
* t1oo.getT2ooSet().add(t2oo2);
* Sql语句为：
* Hibernate: insert into t1oo (name, id) values (?, ?)
* Hibernate: insert into t2oo (avg, aid, id) values (?, ?, ?)
* Hibernate: insert into t2oo (avg, aid, id) values (?, ?, ?)
* Hibernate: update t2oo set aid=? where id=?
* Hibernate: update t2oo set aid=? where id=?
* | 3 | 24 | 12 |
* | 4 | 23 | 12 |
* +----+-----+------+
*/
public void testSet(){
System.out.println("\r\n\r\n********************Set************************");
T1oo t1oo = new T1oo();
t1oo.setName("list");
T2oo t2oo1 = new T2oo(); t2oo1.setAvg(new Integer(23));
T2oo t2oo2 = new T2oo(); t2oo2.setAvg(new Integer(24));
Session session = HibernateSessionFactory.currentSession();
Transaction tr1 = session.beginTransaction();
session.save(t1oo);
t1oo = (T1oo) session.load(T1oo.class,t1oo.getId());
t1oo.setT2ooSet(new HashSet()) ;
t1oo.getT2ooSet().add(t2oo1);
t1oo.getT2ooSet().add(t2oo2);
System.out.println( t1oo.getT2ooSet().size()+"" );
tr1.commit();
System.out.println();
T2oo t2oo3 = new T2oo(); t2oo3.setAvg(new Integer(25));
T1oo t1oo2 = new T1oo(); t1oo2.setName("mz");
t2oo3.setT1oo(t1oo2);
Transaction tr2 = session.beginTransaction();
session.save(t2oo3);
try {
tr2.commit();
} catch (Exception e) {
System.out.println("//err: 没有主动权 cascade = 'all' 不可以级联save t1oo //");
}
session.close();
HibernateSessionFactory.closeSession();
}
结果是：
********************Set************************
2
Hibernate: insert into t1oo (name, id) values (?, ?)
Hibernate: insert into t2oo (avg, aid, id) values (?, ?, ?)
Hibernate: insert into t2oo (avg, aid, id) values (?, ?, ?)
Hibernate: update t2oo set aid=? where id=?
Hibernate: update t2oo set aid=? where id=?
//err: 没有主动权 cascade = 'all' 不可以级联save t1oo //
评论
# re: hibernate 部分问题总结——1 回复 更多评论
2007-11-19 20:04 by
不错，收藏
# re: hibernate 部分问题总结——1[未登录] 回复 更多评论
2009-02-14 11:23 by
session.close();
HibernateSessionFactory.closeSession();
为什么要调用两次
# re: hibernate 部分问题总结——1 回复 更多评论
2009-02-16 09:27 by
第一次 session.close(); 为本线程的session关闭
HibernateSessionFactory.closeSession(); 第二次为 全部连接断开
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