public class Client
{
 public static void main(String[] args)
 {
  Session session = HibernateUtil.getSessionFactory().openSession();
  Transaction tx = null;
  try
  {
   /*開啟一個事務*/
   tx = session.beginTransaction();
   /*從數據庫中獲取id="402881e534fa5a440134fa5a45340002"的Customer對象*/
   Customer customer1 = (Customer)session.get(Customer.class, "402881e534fa5a440134fa5a45340002");
   System.out.println("customer.getUsername is"+customer1.getUsername());
   /*事務提交*/
   tx.commit();
   
   System.out.println("-------------------------------------");
   
   /*開啟一個新事務*/
   tx = session.beginTransaction();
   /*從數據庫中獲取id="402881e534fa5a440134fa5a45340002"的Customer對象*/
   Customer customer2 = (Customer)session.get(Customer.class, "402881e534fa5a440134fa5a45340002");
   System.out.println("customer2.getUsername is"+customer2.getUsername());
   /*事務提交*/
   tx.commit();
   
   System.out.println("-------------------------------------");
   
   /*比較兩個get()方法獲取的對象是否是同一個對象*/
   System.out.println("customer1 == customer2 result is "+(customer1==customer2));
  }
  catch (Exception e)
  {
   if(tx!=null)
   {
    tx.rollback();
   }
  }
  finally
  {
   session.close();
  }
 }
}

結果
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

<!-- EHCache的配置,hibernate.cfg.xml --> 
<hibernate-configuration>
 <session-factory>
  <!-- 設置二級緩存插件EHCache的Provider類-->
  <property name="hibernate.cache.provider_class">
   org.hibernate.cache.EhCacheProvider
  </property>
  <!-- 啟動"查詢緩存" -->
  <property name="hibernate.cache.use_query_cache">
   true
  </property>
 </session-factory>
 </hibernate-configuration>

<!-- ehcache.xml -->
<?xml version="1.0" encoding="UTF-8"?>
<ehcache>
 <!--
  緩存到硬盤的路徑
 -->
 <diskStore path="d:/ehcache"></diskStore>
 <!--
  默認設置
  maxElementsInMemory : 在內存中最大緩存的對象數量。
  eternal : 緩存的對象是否永遠不變。
  timeToIdleSeconds ：可以操作對象的時間。
  timeToLiveSeconds ：緩存中對象的生命周期，時間到后查詢數據會從數據庫中讀取。
  overflowToDisk ：內存滿了，是否要緩存到硬盤。
 -->
 <defaultCache maxElementsInMemory="200" eternal="false" 
  timeToIdleSeconds="50" timeToLiveSeconds="60" overflowToDisk="true"></defaultCache>
 <!--
  指定緩存的對象。
  下面出現的的屬性覆蓋上面出現的，沒出現的繼承上面的。
 -->
 <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>
  <!-- 設置該持久化類的二級緩存并發訪問策略 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">
   <!-- 主鍵設置 -->
   <id name="id" type="string">
    <column name="id"></column>
    <generator class="uuid"></generator>
   </id>
   <!-- 屬性設置 -->
   <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>