Hibernate+ehcache二级缓存技术

1、首先设置EhCache，建立配置文件ehcache.xml，默认的位置在class-path，可以放到你的src目录下：

<?xml version="1.0" encoding="UTF-8"?> 
<ehcache>
    <diskStore path="java.io.tmpdir" />
    <defaultCache 
    maxElementsInMemory="10000" 
    eternal="false"
    timeToIdleSeconds="1" 
    timeToLiveSeconds="1" 
    overflowToDisk="true" />
    <cache name="com.prl.entity.SGpstraceinfo" 
        maxElementsInMemory="10000"
        eternal="false" 
        timeToIdleSeconds="300"
        timeToLiveSeconds="600"
        overflowToDisk="true" />
    <cache name="com.prl.entity.SLbstraceinfo" 
        maxElementsInMemory="10000"
        eternal="false" 
        timeToIdleSeconds="300"
        timeToLiveSeconds="600"
        overflowToDisk="true" />
    <cache name="org.hibernate.cache.UpdateTimestampsCache"
        maxElementsInMemory="5000"
        eternal="true"
        overflowToDisk="true"/>
    <cache name="org.hibernate.cache.StandardQueryCache"
        maxElementsInMemory="10000"
        eternal="false"
        timeToLiveSeconds="120"
        overflowToDisk="true"/>    
</ehcache>

(注意里面的cache name与*.hbm.xml里面的region相对应)

2、在applicationContext.xml 配置文件中加入一个bean：

    <bean id="hibernateTemplate"
            class="org.springframework.orm.hibernate3.HibernateTemplate">
            <property name="sessionFactory">
               <ref bean="sessionFactory" />
            </property>
            <property name="cacheQueries">
               <value>true</value>
            </property>
    </bean> 

        <property name="hibernateProperties">
            <props>
                <prop key="hibernate.dialect">
                    org.hibernate.dialect.Oracle9Dialect
                </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.show_sql">false</prop>
                <prop key="hibernate.cache.use_query_cache">true</prop>
                <prop key="hibernate.cache.provider_class">org.hibernate.cache.EhCacheProvider</prop>            
                
            </props>
        </property>

(说明一下：如果不设置“查询缓存”，那么hibernate只会缓存使用load()方法获得的单个持久化对象，如果想缓存使用findall()、list()、Iterator()、createCriteria()、createQuery()等方法获得的数据结果集的话，就需要设置
hibernate.cache.use_query_cache true 才行 )

3. 在你想设置缓存的pojo的dao中修改如下：(去掉sessionFactoty属性，加入hibernateTemplate属性)

    <bean id="SLbstraceinfoDAO"
        class="com.prl.entity.SLbstraceinfoDAO">
        <!--  
        <property name="sessionFactory">
            <ref bean="sessionFactory" />
        </property>
        -->
        <property name="hibernateTemplate">
                   <ref bean="hibernateTemplate" />
        </property>        
    </bean>

4.在SLbstraceinfo.hbm.xml里加入：(注意必须在class节点下加入)

    <class name="com.prl.entity.SLbstraceinfo" table="S_LBSTRACEINFO" schema="HTGIS">
    <cache usage="read-write" region="com.prl.entity.SLbstraceinfo"/> 

5.java代码里激活缓存：

    public Pagination findPageByCriteria(final DetachedCriteria detachedCriteria, final int pageSize,   
            final int pageNum) {   
        return (Pagination) getHibernateTemplate().execute(new HibernateCallback() {   
            public Object doInHibernate(Session session) throws HibernateException { 
                //PaginationSupport ps = new PaginationSupport(items, totalCount, pageSize, startIndex);
                Pagination<SLbstraceinfo> page;
                try {
                    Criteria criteria = detachedCriteria.getExecutableCriteria(session);  
                    criteria.setCacheable(true);
                    int totalCount = ((Integer) criteria.setProjection(Projections.rowCount()).uniqueResult()).intValue();   
                    criteria.setProjection(null);
                    System.out.println("firstResult="+((pageNum-1)*pageSize+1));
                    List items = criteria.setFirstResult( (pageNum-1)*pageSize+1 ).setMaxResults(pageSize).list();   
                    page = new ListPagination<SLbstraceinfo>(
                            items, pageNum, pageSize);
                    page.setTotalElements(totalCount);
                } catch (RuntimeException e) {                    
                    e.printStackTrace();
                    return null;
                }
                return page;   
            }   
        }, true);   
    }  

(注意这里的criteria.setCacheable(true);)