不能做二级缓存

Question

在我的applicationcontext.xml中

<bean id="annotatedsessionFactory" class="org.springframework.orm.hibernate3.annotation.AnnotationSessionFactoryBean">
<property name="packagesToScan" value="testonly.package.model" />
<property name="hibernateProperties">
    <props>
        <prop key="hibernate.dialect">org.hibernate.dialect.Oracle9Dialect</prop>
        <prop key="hibernate.show_sql">true</prop>
        <prop key="hibernate.format_sql">true</prop>
        <prop key="hibernate.use_sql_comments">true</prop>
        <prop key="hibernate.cglib.use_reflection_optimizer">true</prop>
        <prop key="hibernate.hbm2ddl.auto">update</prop>
        <prop key="hibernate.c3p0.min_size">5</prop>
        <prop key="hibernate.c3p0.max_size">20</prop>
        <prop key="hibernate.c3p0.timeout">1800</prop>
        <prop key="hibernate.c3p0.max_statements">50</prop>
        <prop key="hibernate.cache.provider_class">
                org.hibernate.cache.EhCacheProvider
        </prop>
        <prop key="hibernate.cache.use_second_level_cache">true</prop>
        <prop key="hibernate.cache.use_query_cache">true</prop>
    </props>
</property>
<property name="dataSource">
    <ref bean="dataSource" />
</property>

在我的实体中

@Entity
@Cache(usage=CacheConcurrencyStrategy.NONSTRICT_READ_WRITE)

@Table(name = "TestPOJOCATEGORY")
@NamedQueries({
 @NamedQuery(name = "TestPOJOcategory.findAll", query = "SELECT h FROM TestPOJOcategory h"),
 @NamedQuery(name = "TestPOJOcategory.findById", query = "SELECT h FROM TestPOJOcategory h WHERE h.id = :id"),
 @NamedQuery(name = "TestPOJOcategory.findByCategoryname", query = "SELECT h FROM TestPOJOcategory h WHERE h.categoryname = :categoryname")})
public class TestPOJOcategory implements Serializable {

在我的道

public List<TestPOJOcategory> getAllCategory(final String keyword, final int nFirst,
        final int nPageSize,
        final String sortColumnId,
        final boolean bSortOrder) {

  List<TestPOJOcategory> result = (List<TestPOJOcategory>) getHibernateTemplate().execute(new HibernateCallback() {
    public Object doInHibernate(Session session) {
      Criteria crit = session.createCriteria(TestPOJOcategory.class, "TestPOJOcategory")
       .add(Restrictions.ilike("categoryname", keyword))
       .addOrder(bSortOrder ? Order.asc(sortColumnId) : Order.desc(sortColumnId))
       .setFirstResult(nFirst).setMaxResults(nPageSize);
      System.out.println("why still call from DB? suppose to call from cache");
      return crit.list();
    }
  });
  return result;
}

echcache.xml

 <cache name="testonly.package.model.TestPOJOcategory"
        maxElementsInMemory="200"
        eternal="true"
        overflowToDisk="false"
        timeToIdleSeconds="300"
        timeToLiveSeconds="600"
    />

每次我调用dao时,它仍会从DB调用.为什么？

Answer 1

首先,System.out.println()无论是否访问二级缓存,您的语句都会被执行,因为这种访问是在list()方法内进行的.

其次,标准-很像查询-并不会自动使用2级高速缓存; 您指定的配置属性仅允许使用它.您仍然需要通过调用setCacheable(true)以下方法将每个Query/Criteria实例明确标记为可缓存:

Criteria crit = ...;
crit.setCacheable(true);
return crit.list();

在旁注,因为你正在使用HibernateTemplate你也可以正确使用它:-)并摆脱手动doInHibernate包装:

public List<TestPOJOcategory> getAllCategory(final String keyword, final int nFirst,
    final int nPageSize,
    final String sortColumnId,
    final boolean bSortOrder) {

  DetachedCriteria crit = DetachedCriteria.forClass(TestPOJOcategory.class);
  crit.add(Restrictions.ilike("categoryname", keyword))
   .addOrder(bSortOrder ? Order.asc(sortColumnId) : Order.desc(sortColumnId));
  getHibernateTemplate().setCacheQueries(true); // works on both queries and criteria
  return (List<TestPOJOcategory>) getHibernateTemplate()
   .findByCriteria(crit, nFirst, nPageSize);
}

Answer 2

好吧,使用二级缓存并不意味着您可以根据任意HQL(或Criteria)查询在缓存中找到对象.第二个缓存仅在通过其键访问对象或导航对象图时使用.

所以,在这里,你需要使用查询缓存(是的,有3个缓存:第一级缓存,第二级缓存和查询缓存).这需要:

session.createQuery("query").setCacheable(true); 

或者,使用时Criteria:

session.createCriteria(...).add(...).setCacheable(true);

并设置了hibernate属性(你有):

hibernate.cache.use_second_level_cache=true
hibernate.cache.use_query_cache=true 

实际上,如果你想更好地理解Hibernate使用的各种缓存机制以及Hibernate完全缓存的内容(即"脱水"实体),我会热烈建议检查以下资源:

• Hibernate:真正理解二级和查询缓存
• 使用二级缓存加速您的Hibernate应用程序
• Hibernate缓存

这两篇文章有点陈旧但仍然适用.后者是最近的.所有这些都是很好的读数IMO.