最近项目需要用到memcached做hibernate的二级缓存，网上多是使用hibernate3配置，项目使用hibernate4，因配置上有所变化，记录配置过程备忘

测试系统环境为windows XP

1、下载memcached的windows安装版，我的是memcached-win32-1.4.4-14.zip，解压到某个目录，如：D:\mySoftware\memcached14414

在控制台输入D:\mySoftware\memcached14414\memcached.exe -d install 安装memcached

D:\mySoftware\memcached14414\memcached.exe -d start 启动memcached

2、导入依赖包：

commons-codec-1.10.jar

hibernate3-memcached-1.5.jar(hibernate3使用此包)

hibernate4-memcached-1.0.jar(hibernate4使用此包)

memcached-2.5.jar

slf4j-api-1.6.1.jar

spy-2.4.jar

资源下载地址：http://download.csdn.net/detail/zhanyingf15/8477973

3、修改配置文件

<property name="hibernateProperties">
<props>
<prop key="hibernate.dialect">cn.xxx.util.Dialet</prop>
<prop key="hibernate.show_sql">true</prop>
<prop key="hibernate.format_sql">true</prop> 
<!-- 缓存配置 -->
<prop key="hibernate.cache.use_query_cache">true</prop><!-- 开启缓存 -->
<prop key="hibernate.cache.use_second_level_cache">true</prop><!-- 开启二级缓存 -->
<!-- hibernate3 二级缓存提供类
<prop key="hibernate.cache.provider_class">
  com.googlecode.hibernate.memcached.MemcachedCacheProvider
</prop>
-->
<!-- hibernate4 二级缓存提供类-->
<prop key="hibernate.cache.region.factory_class">
  com.googlecode.hibernate.memcached.MemcachedRegionFactory
</prop>
<prop key="hibernate.cache.use_structured_entries">true</prop><!-- 结构化存储 -->
<prop key="hibernate.max_fetch_depth">3</prop>
<prop key="hibernate.memcached.servers">localhost:11211</prop><!-- 二级缓存服务器位置和端口 -->

<!-- 二级缓存前缀名称，很多文章都是ehcache，我测试改成 memcache也没问题-->
<prop key="hibernate.cache.region_prefix">quality.cache.ehcache</prop>
<prop key="hibernate.memcached.operationTimeout">5000</prop><!-- 操作超时时间，单位ms -->
<prop key="hibernate.memcached.cacheTimeSeconds">20</prop><!-- 缓存失效时间，单位秒 -->
</props>
</property>

4、修改实体映射文件

<hibernate-mapping package="cn.xxx.po">
 <class name="Game" table="game">
  <cache usage="read-write"/>  <!--可根据情况设为read-only等值-->
  <id column="GameID" name="gameID" type="integer">
  <generator class="native"/>
  </id> 
  <property column="GameIntroduce" name="gameIntroduce" type="string"/>
 </class>
</hibernate-mapping>

5、开启查询缓存

Query query  = getSession().createQuery(queryString);
query.setCacheable(true);

这样就可以使用memcached强大的缓存功能了

经测试启动正常，测试数据库mysql，数据量为150万，测试方法是使用模糊查询找出一个类型为text的字段中包含“12”字符的记录

不用memcached下使用hibernate hql和JDBC均耗时1100ms左右，使用memcached做hibernate二级缓存后初始查询耗时在1100ms左右

后续查询最低0ms，最高32ms，大多数维持在16ms左右。

在服务器程序运行过程中结束memcached服务再进行查询，myeclipse控制台持续打印出以下错误

2015-03-06 14:17:03.546 WARN net.spy.memcached.MemcachedConnection:  Closing, and reopening {QA sa=localhost/127.0.0.1:11211, #Rops=0, #Wops=3, #iq=0, topRop=null, topWop=net.spy.memcached.protocol.ascii.GetOperationImpl@18437e5, toWrite=0, interested=0}, attempt 2.
2015-03-06 14:17:11.562 INFO net.spy.memcached.MemcachedConnection:  Reconnecting {QA sa=localhost/127.0.0.1:11211, #Rops=0, #Wops=7, #iq=0, topRop=null, topWop=net.spy.memcached.protocol.ascii.GetOperationImpl@18437e5, toWrite=0, interested=0}
2015-03-06 14:17:12.484 INFO net.spy.memcached.MemcachedConnection:  Connection state changed for sun.nio.ch.SelectionKeyImpl@1e171e9
2015-03-06 14:17:12.484 INFO net.spy.memcached.MemcachedConnection:  Reconnecting due to failure to connect to {QA sa=localhost/127.0.0.1:11211, #Rops=0, #Wops=7, #iq=0, topRop=null, topWop=net.spy.memcached.protocol.ascii.GetOperationImpl@18437e5, toWrite=0, interested=0}
java.net.ConnectException: Connection refused: no further information
at sun.nio.ch.SocketChannelImpl.checkConnect(Native Method)
at sun.nio.ch.SocketChannelImpl.finishConnect(SocketChannelImpl.java:701)
at net.spy.memcached.MemcachedConnection.handleIO(MemcachedConnection.java:322)
at net.spy.memcached.MemcachedConnection.handleIO(MemcachedConnection.java:219)
at net.spy.memcached.MemcachedClient.run(MemcachedClient.java:1591)

查询过程陷入等待，耗时135047ms后查询到数据。

在安装memcached的服务器宕机后，二级缓存将不可用，查询过程慢到一个无法忍受的地步，时间大量耗费在重连memcached服务上，暂未找到解决办法

本文地址:http://www.cnblogs.com/wangjiajun/p/4332495.html 

参考文章http://blog.sina.com.cn/s/blog_67b9ad8d01011xsd.html