Hibernate二级缓存示例

Question

我正在开发hibernate+ ehcache程序。

@Entity
@Table(name = "pizza")
public class Pizza implements Serializable{
    @Id
    @GeneratedValue
    private Integer id;
    private String name;
    private double price;

    public long getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public double getPrice() {
        return price;
    }

    public void setPrice(double price) {
        this.price = price;
    }

}

ehcache.xml

  <cache name="com.abp.osp.domain.Pizza"   
maxElementsInMemory="100"   
eternal="false"   
timeToIdleSeconds="5"   
timeToLiveSeconds="200" /> 
</ehcache>

我在bean.xml中提到了ehcache

   <prop key="hibernate.cache.provider_configuration_file_resource_path">ehcache.xml</prop>
        <prop key="hibernate.cache.use_second_level_cache">true</prop>
        <prop key="hibernate.cache.use_query_cache">true</prop>
        <prop key="hibernate.cache.region.factory_class">net.sf.ehcache.hibernate.EhCacheRegionFactory</prop>
         <prop key="hibernate.cache.provider_class">net.sf.ehcache.hibernate.EhCacheProvider</prop>

我在dao类中的调用方法是

 Session session1=sessionFactory.openSession();

          Pizza pizza2=(Pizza)session1.load(Pizza.class, 2);
          System.out.println("pizza2--"+pizza2.getName());  
          session1.close();

 Session session2=sessionFactory.openSession();

          Pizza pizza4=(Pizza)session2.load(Pizza.class, 2);
          System.out.println("pizza4--"+pizza4.getName());  
          session2.close();

输出为：

Hibernate: select pizza0_.id as id0_0_, pizza0_.name as name0_0_, pizza0_.price as price0_0_ from pizza pizza0_ where pizza0_.id=?
pizza2--Thin Crust
Hibernate: select pizza0_.id as id0_0_, pizza0_.name as name0_0_, pizza0_.price as price0_0_ from pizza pizza0_ where pizza0_.id=?
pizza4--Thin Crust

但是它在数据库中命中了两次。我在代码中没有发现任何错误。请向我建议为什么它在数据库中命中了两次。

Answer 1

我已经解决了我的问题。我需要添加

@Cache(usage=CacheConcurrencyStrategy.READ_ONLY,region="pizza")

在域类中。

@Entity
@Cache(usage=CacheConcurrencyStrategy.READ_ONLY,region="pizza")
@Table(name = "pizza")
public class Pizza implements Serializable{