hibernate缓存

一级缓存：

Hibernate一级缓存是强制的，它是Session级缓存。如果会话关闭，所有缓存的对象都将丢失。

二级缓存配置步骤：

1.在指定hibernate.cfg.xml配置文件中配置缓存提供程序（这里选择EHCache作为第二级缓存提供程序）：

<?xml version="1.0" encoding="utf-8"?><!DOCTYPE hibernate-configuration SYSTEM "http://www.hibernate.org/dtd/hibernate-configuration-3.0.dtd"><hibernate-configuration>   <session-factory>   <property name="hibernate.dialect">      org.hibernate.dialect.MySQLDialect   </property>   <property name="hibernate.connection.driver_class">      com.mysql.jdbc.Driver   </property>   <!-- Assume students is the database name -->   <property name="hibernate.connection.url">      jdbc:mysql://localhost/test   </property>   <property name="hibernate.connection.username">      root   </property>   <property name="hibernate.connection.password">      root123   </property>   <property name="hibernate.cache.provider_class">      org.hibernate.cache.EhCacheProvider   </property>   <!-- List of XML mapping files -->   <mapping resource="Employee.hbm.xml"/></session-factory></hibernate-configuration>

注：有4种缓存提供程序，兼容矩阵如下：

Strategy/ProviderRead-onlyNonstrictread-writeRead-writeTransactionalEHCacheXXX OSCacheXXX SwarmCacheXX  JBoss CacheX  X

2.指定缓存设置属性（EHCache都有自己的配置文件ehcache.xml）：

<diskStore path="java.io.tmpdir"/><defaultCachemaxElementsInMemory="1000"eternal="false"timeToIdleSeconds="120"timeToLiveSeconds="120"overflowToDisk="true"/><cache name="Employee"maxElementsInMemory="500"eternal="true"timeToIdleSeconds="0"timeToLiveSeconds="0"overflowToDisk="false"/>

3.应用二级缓存（4种并发策略：Transactional、Read-write、Nonstrict-read-write、Read-only）：

<?xml version="1.0" encoding="utf-8"?><!DOCTYPE hibernate-mapping PUBLIC  "-//Hibernate/Hibernate Mapping DTD//EN" "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd"> <hibernate-mapping>   <class name="Employee" table="EMPLOYEE">      <meta attribute="class-description">         This class contains the employee detail.       </meta>      <cache usage="read-write"/>      <id name="id" type="int" column="id">         <generator class="native"/>      </id>      <property name="firstName" column="first_name" type="string"/>      <property name="lastName" column="last_name" type="string"/>      <property name="salary" column="salary" type="int"/>   </class></hibernate-mapping>

查询级别缓存：

必须先使用 hibernate.cache.use_query_cache="true"属性在配置文件中激活它。

Session session = SessionFactory.openSession();Query query = session.createQuery("FROM EMPLOYEE");query.setCacheable(true);List users = query.list();SessionFactory.closeSession();

Hibernate支持缓存区域的概念。缓存区是给定的一个缓存名称，Hibernate可以通过该名称查找相应缓存。

Session session = SessionFactory.openSession();Query query = session.createQuery("FROM EMPLOYEE");query.setCacheable(true);query.setCacheRegion("employee");List users = query.list();SessionFactory.closeSession();