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: selectcustomer0_.id as id0_0_,customer0_.username as username0_0_,customer0_.balance as balance0_0_ fromcustomer customer0_ wherecustomer0_.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>

<hibernate-mapping><class name="com.suxiaolei.hibernate.pojos.Customer" table="customer"><!-- 主键设置 --><id name="id" type="string"><column name="id"></column><generator class="uuid"></generator></id><!-- 属性设置 --><property name="username" column="username" type="string"></property><property name="balance" column="balance" type="integer"></property><set name="orders" inverse="true" cascade="all" lazy="false" fetch="join"><cache usage="read-only"/><key column="customer_id" ></key><one-to-many class="com.suxiaolei.hibernate.pojos.Order"/></set></class></hibernate-mapping>