hibernate-memcached--在Hibernate中使用Memcached作为一个二级分布式缓存

hibernate-memcached--在Hibernate中使用Memcached作为一个二级分布式缓存今天在网上看到一个用Memcached作为Hibernate二级分布式缓存，感觉挺有兴趣，就是尝试用了，感觉还不错，就推荐给大家看一下。

官方网址:?http://code.google.com/p/hibernate-memcached/
目前最新版本为1.0, 支持Hibernate3.3.

下面是具体的使用方法:
hibernate-memcached需要支持的类库如下:

• hibernate-memcached-<version>.jar
• memcached-2.1.jar
• spy-2.4.jar
• commons-codec 1.3
• slf4j-1.5.0.jar 如果你的项目使用的是Log4j,可以用?slf4j-log4j12-1.5.0.jar
  配置方法如下：
  
  配置Hibernate使用cache提供类
  
  hibernate.cache.provider_classcom.googlecode.hibernate.memcached.MemcachedCacheProvider
  

  设置查询缓存开启

  hibernate.cache.use_query_cachetrue
  其它一些参数设置说明:PropertyDefaultDescriptionhibernate.memcached.serverslocalhost:11211memcached 服务地址，多个用空格分隔
  格式host:port?
  hibernate.memcached.cacheTimeSeconds300缓存失效时间,单位秒hibernate.memcached.keyStrategyHashCodeKeyStrategy缓存Key生成存储HashCode算法hibernate.memcached.readBufferSizeDefaultConnectionFactory.DEFAULT_READ_BUFFER_SIZE从服务器读取数据缓存区大小
  hibernate.memcached.operationQueueLengthDefaultConnectionFactory.DEFAULT_OP_QUEUE_LENMaximum length of the operation queue returned by this connection factoryhibernate.memcached.operationTimeoutDefaultConnectionFactory.DEFAULT_OPERATION_TIMEOUT操作超时时间设置hibernate.memcached.hashAlgorithmHashAlgorithm.KETAMA_HASH新增缓存数据到服务器时使用的Hash散列算法。 当 hibernate-memcached 设置成 KETAMA_HASH算法时,注意:默认客户端API使用的是 HashAlgorithm.NATIVE_HASHhibernate.memcached.clearSupportedfalse支持MemcachedCache.clear()方法清空缓存。
  建议不要开启。
  
  配置示例(本文以Hibernate3.3-entitymanager为例)
  配置 persistence.xml文件
  <?xml?version="1.0"?encoding="UTF-8"?>
  <persistence?xmlns="http://java.sun.com/xml/ns/persistence""?target="_new">http://java.sun.com/xml/ns/persistence"?xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"?xsi:schemaLocation="http://java.sun.com/xml/ns/persistence?http://java.sun.com/xml/ns/persistence/persistence_1_0.xsd"?version="1.0">
  
  <persistence-unit?name="entityManager"?transaction-type="RESOURCE_LOCAL">
  <provider>org.hibernate.ejb.HibernatePersistence</provider>
  <jta-data-source>java:comp/env/jdbc/qualitydb</jta-data-source>
  
  <properties>
  <property?name="hibernate.dialect"?value="org.hibernate.dialect.PostgreSQLDialect"?/>
  <property?name="hibernate.max_fetch_depth"?value="3"?/>
  <property?name="hibernate.show_sql"?value="true"?/>
  
  
  <property?name="hibernate.cache.region_prefix"?value="quality.cache.ehcache"/>
  <property?name="hibernate.cache.use_second_level_cache"?value="true"/>
  <property?name="hibernate.cache.use_structured_entries"?value="true"/>
  <property?name="hibernate.cache.use_query_cache"?value="true"/>
  <property?name="hibernate.cache.provider_class"?value="com.googlecode.hibernate.memcached.MemcachedCacheProvider"/>
  <property?name="hibernate.memcached.servers"?value="localhost:11211"/>
  
  </properties>
  
  </persistence-unit>
  
  </persistence>
  
  启动后，提示如下：
  2008-08-28 17:10:08,312 JCLLoggerAdapter.java265 INFO -- Starting MemcachedClient...
  2008-08-28 17:10:08.718 INFO net.spy.memcached.MemcachedConnection: Added {QA sa=localhost/127.0.0.1:11211, #Rops=0, #Wops=0, #iq=0, topRop=null, topWop=null, toWrite=0, interested=0} to connect queue
  2008-08-28 17:10:08.750 INFO net.spy.memcached.MemcachedConnection: Connection state changed for sun.nio.ch.SelectionKeyImpl@16e59da
  
  表示我们第一步配置已经成功了，接下来，对需要进行缓存的Entity进行配置
  ?1?@Entity
  ?2?@Cache(usage?=?CacheConcurrencyStrategy.READ_WRITE)//设置要求缓存
  ?3?public?class?Student?{
  ?4?
  ?5???@Id
  ?6???@Column(length=32)
  ?7?????private?String?id;
  ?8?????
  ?9?????@Column(length=20)
  10?????private?string?name;
  11?????
  12?????@OneToMany
  13?????@Cache(usage?=?CacheConcurrencyStrategy.READ_WRITE)
  14?????private?Set<Book>?books;
  15?
  16?}