Second-level cache is not enabled for usage [hibernate.cache.use_second_level

本文链接：https://blog.youkuaiyun.com/navy0168/article/details/84264581

本文介绍如何在Hibernate3中配置并使用二级缓存，通过EhCacheProvider实现，并提供了具体的配置示例及测试代码。

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在hibernate3下面使用二级缓存的实例 
设置使用二级缓存 
方式1在hibernate.cfg文件中添加 
<property name="cache.provider_class">org.hibernate.cache.EhCacheProvider</property>
 <property name="hibernate.cache.use_second_level_cache">true</property> 
<property name="hibernate.cache.use_query_cache">true</property> 
说使用Configuration配置 
cfg.setProperty("hibernate.cache.provider_class","org.hibernate.cache.EhCacheProvider");
 cfg.setProperty("hibernate.cache.use_second_level_cache","true"); 
cfg.setProperty("hibernate.cache.use_query_cache","true"); 
然后在映射文件中使用二级缓存 
如单个实体的二级缓存 
<class name="Product" table="product" > 
<cache usage="read-write"/> 
<id name="id" type="java.lang.Integer"> 
<column name="id"/> 
<generator class="increment"/> 
</id> 
<property name="name" type="java.lang.String"/> 
<property name="pDesc" type="java.lang.String"/> 
<property name="orderId" type="java.lang.Integer"/> 
</class> 

最后测试 
Configuration cfg = new Configuration(); 
cfg.configure(); 
//cfg.setProperty("hibernate.cache.provider_class","org.hibernate.cache.EhCacheProvider");
 //cfg.setProperty("hibernate.cache.use_second_level_cache","true"); 
//cfg.setProperty("hibernate.cache.use_query_cache","true"); 

SessionFactory sessionFactory =  cfg.buildSessionFactory(); 
Session session = sessionFactory.getCurrentSession(); 
Transaction transaction = session.beginTransaction(); 
Product product = (Product)session.get(Product.class,1); 
transaction.commit(); 
System.out.println(product.getName()); 

Session session2 = sessionFactory.getCurrentSession(); 
Transaction trasaction2 = session2.beginTransaction(); 
Product product2 = (Product)session2.get(Product.class,1); 
trasaction2.commit(); 
System.out.println(product2.getName()); 

打印结果为： 
Hibernate: select product0_.id as id0_0_, product0_.name as name0_0_, product0_.pDesc as pDesc0_0_, product0_.orderId as orderId0_0_ from product product0_ where product0_.id=?
 oly 
oly 
可见只查询了一次数据库。