public class Client

{

    public static void main(String[] args)

    {

        Session session = HibernateUtil.getSessionFactory().openSession();

        Transaction tx = null;

        try

        {

            /*开启一个事务*/

            tx = session.beginTransaction();

            /*从数据库中获取id="402881e534fa5a440134fa5a45340002"的Customer对象*/

            Customer customer1 = (Customer)session.get(Customer.class, "402881e534fa5a440134fa5a45340002");

            System.out.println("customer.getUsername is"+customer1.getUsername());

            /*事务提交*/

            tx.commit();

            System.out.println("-------------------------------------");

            /*开启一个新事务*/

            tx = session.beginTransaction();

            /*从数据库中获取id="402881e534fa5a440134fa5a45340002"的Customer对象*/

            Customer customer2 = (Customer)session.get(Customer.class, "402881e534fa5a440134fa5a45340002");

            System.out.println("customer2.getUsername is"+customer2.getUsername());

            /*事务提交*/

            tx.commit();

            System.out.println("-------------------------------------");

            /*比较两个get()方法获取的对象是否是同一个对象*/

            System.out.println("customer1 == customer2 result is "+(customer1==customer2));

        }

        catch (Exception e)

        {

            if(tx!=null)

            {

                tx.rollback();

            }

        }

        finally

        {

            session.close();

        }

    }

}

结果

Hibernate:

    select

        customer0_.id as id0_0_,

        customer0_.username as username0_0_,

        customer0_.balance as balance0_0_

    from

        customer customer0_

    where

        customer0_.id=?

customer.getUsername islisi

-------------------------------------

customer2.getUsername islisi

-------------------------------------

customer1 == customer2 result is true

sessionFactory.evict(Customer.class, new Integer(1));  

sessionFactory.evict(Customer.class);  

sessionFactory.evictCollection("Customer.orders");  

<!-- EHCache的配置,hibernate.cfg.xml -->

<hibernate-configuration>

    <session-factory>

       <!-- 设置二级缓存插件EHCache的Provider类-->

       <property name="hibernate.cache.provider_class">

          org.hibernate.cache.EhCacheProvider

       </property>

       <!-- 启动"查询缓存" -->

       <property name="hibernate.cache.use_query_cache">

          true

       </property>

    </session-factory>

  </hibernate-configuration>

<!-- ehcache.xml -->

<?xml version="1.0" encoding="UTF-8"?>
<ehcache>
    <!--
        缓存到硬盘的路径
    -->
    <diskStore path="d:/ehcache"></diskStore>
    <!--
        默认设置
        maxElementsInMemory : 在內存中最大緩存的对象数量。
        eternal : 缓存的对象是否永远不变。
        timeToIdleSeconds ：可以操作对象的时间。
        timeToLiveSeconds ：缓存中对象的生命周期，时间到后查询数据会从数据库中读取。
        overflowToDisk ：内存满了，是否要缓存到硬盘。
    -->
    <defaultCache maxElementsInMemory="200" eternal="false" 
        timeToIdleSeconds="50" timeToLiveSeconds="60" overflowToDisk="true"></defaultCache>
    <!--
        指定缓存的对象。
        下面出现的的属性覆盖上面出现的，没出现的继承上面的。
    -->
    <cache name="com.suxiaolei.hibernate.pojos.Order" maxElementsInMemory="200" eternal="false" 
        timeToIdleSeconds="50" timeToLiveSeconds="60" overflowToDisk="true"></cache>
</ehcache>

<!-- *.hbm.xml -->

<?xml version="1.0" encoding='UTF-8'?>

<!DOCTYPE hibernate-mapping PUBLIC

 "-//Hibernate/Hibernate Mapping DTD 3.0//EN"

 "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd" >

<hibernate-mapping>

   <class>

       <!-- 设置该持久化类的二级缓存并发访问策略 read-only read-write nonstrict-read-write transactional-->

       <cache usage="read-write"/>

   </class>

</hibernate-mapping>