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>.jarmemcached-2.1.jarspy-2.4.jarcommons-codec 1.3slf4j-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 queue2008-08-28 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  }

Ok,现在配置已经完成。

 

 

Hibernate的JPA实现:

 

<?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/persistencehttp://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 queue2008-08-28 17:10:08.750 INFO net.spy.memcached.MemcachedConnection: Connection state changed for sun.nio.ch.SelectionKeyImpl@16e59da表示已经配置成功了