Hibernate框架中的缓存技术详解

package com.xqh.util;
import org.hibernate.Session;
import com.xqh.model.User;
public class Test {
public static void main(String[] args) {
Session session = null;
try {
session = HibernateUtil.getSession(); // 获取session
session.beginTransaction(); //开启事务
System.out.println("第一次查询：");
User user = (User)session.get(User.class, new Integer(1));
System.out.println("用户名：" + user.getName());
System.out.println("第二次查询：");
User user1 = (User)session.get(User.class, 1);
System.out.println("用户名：" + user1.getName());
session.getTransaction().commit();
} catch (Exception e) {
e.printStackTrace();
// 出错将回滚事务
session.getTransaction().rollback();
} finally {
// 关闭Session对象
HibernateUtil.closeSession(session);
}
}
}

第一次查询：
Hibernate: 
select
user0_.id as id0_0_,
user0_.name as name0_0_,
user0_.sex as sex0_0_ 
from
tb_user_info user0_ 
where
user0_.id=?
用户名：xqh
第二次查询：
用户名：xqh

<ehcache>
<!-- Sets the path to the directory where cache .data files are created.
If the path is a Java System Property it is replaced by
its value in the running VM.
The following properties are translated:
user.home - User's home directory
user.dir - User's current working directory
java.io.tmpdir - Default temp file path -->
<diskStore path="java.io.tmpdir"/>
<!--Default Cache configuration. These will applied to caches programmatically created through
the CacheManager.
The following attributes are required for defaultCache:
maxInMemory - Sets the maximum number of objects that will be created in memory
eternal - Sets whether elements are eternal. If eternal, timeouts are ignored and the element
is never expired.
timeToIdleSeconds - Sets the time to idle for an element before it expires. Is only used
if the element is not eternal. Idle time is now - last accessed time
timeToLiveSeconds - Sets the time to live for an element before it expires. Is only used
if the element is not eternal. TTL is now - creation time
overflowToDisk - Sets whether elements can overflow to disk when the in-memory cache
has reached the maxInMemory limit.
-->
<defaultCache
maxElementsInMemory="10000"
eternal="false"
timeToIdleSeconds="120"
timeToLiveSeconds="120"
overflowToDisk="true"
/>
<!--Predefined caches. Add your cache configuration settings here.
If you do not have a configuration for your cache a WARNING will be issued when the
CacheManager starts
The following attributes are required for defaultCache:
name - Sets the name of the cache. This is used to identify the cache. It must be unique.
maxInMemory - Sets the maximum number of objects that will be created in memory
eternal - Sets whether elements are eternal. If eternal, timeouts are ignored and the element
is never expired.
timeToIdleSeconds - Sets the time to idle for an element before it expires. Is only used
if the element is not eternal. Idle time is now - last accessed time
timeToLiveSeconds - Sets the time to live for an element before it expires. Is only used
if the element is not eternal. TTL is now - creation time
overflowToDisk - Sets whether elements can overflow to disk when the in-memory cache
has reached the maxInMemory limit.
-->
<!-- Sample cache named sampleCache1
This cache contains a maximum in memory of 10000 elements, and will expire
an element if it is idle for more than 5 minutes and lives for more than
10 minutes.
If there are more than 10000 elements it will overflow to the
disk cache, which in this configuration will go to wherever java.io.tmp is
defined on your system. On a standard Linux system this will be /tmp"
-->
<cache name="sampleCache1"
maxElementsInMemory="10000"
eternal="false"
timeToIdleSeconds="300"
timeToLiveSeconds="600"
overflowToDisk="true"
/>
<!-- Sample cache named sampleCache2
This cache contains 1000 elements. Elements will always be held in memory.
They are not expired. -->
<cache name="sampleCache2"
maxElementsInMemory="1000"
eternal="true"
timeToIdleSeconds="0"
timeToLiveSeconds="0"
overflowToDisk="false"
/> -->
<!-- Place configuration for your caches following -->
</ehcache>

<!-- 开启二级缓存 -->
<property name="hibernate.cache.use_second_level_cache">true</property>
<!-- 指定缓存产品提供商 -->
<property name="hibernate.cache.provider_class">org.hibernate.cache.EhCacheProvider</property>
<!-- 指定二级缓存应用到的实体对象 -->
<class-cache class="com.xqh.model.User" usage="read-only"></class-cache>

package com.xqh.util;
import org.hibernate.Session;
import com.xqh.model.User;
public class Test {
public static void main(String[] args) {
Session session = null; // 第一个Session
try {
session = HibernateUtil.getSession();
session.beginTransaction();
System.out.println("第一次查询:");
User user = (User)session.get(User.class, 1);
System.out.println("用户名：" + user.getName());
session.getTransaction().commit();
} catch (Exception e) {
e.printStackTrace();
// 出错将回滚事务
session.getTransaction().rollback();
} finally {
// 关闭Session对象
HibernateUtil.closeSession(session);
}
try {
session = HibernateUtil.getSession(); // 开启第二个缓存
session.beginTransaction();
System.out.println("第二次查询:");
User user = (User)session.get(User.class, 1);
System.out.println("用户名：" + user.getName());
session.getTransaction().commit();
} catch (Exception e) {
e.printStackTrace();
// 出错将回滚事务
session.getTransaction().rollback();
} finally {
// 关闭Session对象
HibernateUtil.closeSession(session);
}
}
}

第一次查询:
Hibernate: 
select
user0_.id as id0_0_,
user0_.name as name0_0_,
user0_.sex as sex0_0_ 
from
tb_user_info user0_ 
where
user0_.id=?
用户名：xqh
第二次查询:
用户名：xqh