JPA2级缓存的配置

JPA2级缓存的配置

1.加入hibernate－memcached.jar及相关jar包（具体见http://code.google.com/p/hibernate-memcached/）

2.在applicationContext.xml中配置

............
     < bean  id ="entityManagerFactory"
        class ="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean" >
         < property  name ="dataSource"  ref ="dataSource"   />
         < property  name ="jpaVendorAdapter" >
             < bean
                 class ="org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter" >
                 < property  name ="showSql"  value ="${jpa.showSql}"   />
                 < property  name ="generateDdl"  value ="${jpa.generateDdl}"   />
                 < property  name ="database" >
                     < util:constant
                         static-field ="org.springframework.orm.jpa.vendor.Database.ORACLE"   />
                 </ property >
             </ bean >
         </ property >
         < property  name ="jpaProperties" >
             < props >
                 < prop  key ="hibernate.max_fetch_depth" > 3 </ prop >
                 < prop  key ="hibernate.cache.use_second_level_cache" >
                    true
                 </ prop >
                 < prop  key ="hibernate.cache.use_structured_entries" >
                    true
                 </ prop >
                 < prop  key ="hibernate.cache.use_query_cache" > true </ prop >
                 < prop  key ="hibernate.cache.provider_class" >
                    com.googlecode.hibernate.memcached.MemcachedCacheProvider
                 </ prop >
                 < prop  key ="hibernate.memcached.servers" >
                    10.1.19.132:33001 10.1.19.132:33002 10.1.19.132:33003
                 </ prop >
             </ props >
         </ property >
     </ bean >
............

3.在实体类上配置缓存策略
如@org.hibernate.annotations.Cache(usage = CacheConcurrencyStrategy.READ_WRITE)   

下面这几种情况就 不适合加载到二级缓存中:
  1.经常被修改的数据
  2.绝对不允许出现并发访问的数据
  3.与其他应用共享的数据
  下面这己种情况 合适加载到二级缓存中:
  1.数据更新频率低
  2.允许偶尔出现并发问题的非重要数据
  3.不会被并发访问的数据
  4.常量数据
  5.不会被第三方修改的数据