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3聲明式管理Hibernate分布式事務

通過Spring，還可以很方便地切換至另一種事務管理策略。比如需要提供分布式事務管理策略時，只要替換一下配置即可，如代碼10.29所示。

<beans>

<bean id="transactionManager"

class="org.springframework.transaction.jta.JtaTransactionManager">

??? <property name="sessionFactory" >

????? <ref bean="sessionFactory" />

??? </property>

</bean>

<bean id="myDataSource1"

class="org.springframework.jndi.JndiObjectFactoryBean">

????? <property name="jndiName">

????????? <value>java:comp/env/jdbc/myds1</value>

????? </property>

</bean>

<bean id="myDataSource2"

class="org.springframework.jndi.JndiObjectFactoryBean">

????? <property name="jndiName">

????????? <value>java:comp/env/jdbc/myds2</value>

????? </property>

</bean>

<bean id="sessionFactory1"

class="org.springframework.orm.hibernate3.LocalSessionFactoryBean">

??? <property name="dataSource" ref="myDataSource1"/>

??? <property name="configLocations">

????? <value>hibernate.cfg1.xml</value>

??? </property>

</bean>

<bean id="sessionFactory2"

class="org.springframework.orm.hibernate3.LocalSessionFactoryBean">

??? <property name="dataSource" ref="myDataSource2"/>

??? <property name="configLocations">

????? <value>hibernate.cfg2.xml</value>

??? </property>

</bean>

<bean id="dao1"

class="daopackage1.DaoImpl">

??? <property name="sessionFactory" ref="sessionFactory"/>

</bean>

<bean id="dao2"

class="daopackage2.DaoImp2">

??? <property name="sessionFactory" ref="sessionFactory"/>

</bean>

</beans>

<bean id="business" class="businesspackage.BusinessFacadeImpl">

??? <property name="dao1">

????? <ref bean="dao1"/>

??? </property>

??? <property name="dao2">

????? <ref bean="dao2"/>

??? </property>

</bean>

<bean id="businessProxy"

class="org.springframework.transaction.interceptor.TransactionProxyFactoryBean">

??? <property name="transactionManager">

????? <ref bean="transactionManager" />

??? </property>

??? <property name="target">

????? <ref bean="business" />

??? </property>

??? <property name="transactionAttributes">

????? <props>

??????? <prop key="business*">PROPAGATION_REQUIRED</prop>

??????? <prop key="someOtherBusiness*">PROPAGATION_MANDATORY</prop>

????? </props>

??? </property>

</bean>

</beans>

可以看到，對于橫跨多個Hibernate SessionFacotry的分布式事務，只需簡單地將JtaTransactionManager和LocalSessionFactoryBean的定義結合起來就可以了，其中每個DAO通過bean屬性得到各自的SessionFactory引用。

說明：如果所有底層數據源都是支持事務的容器，那么只需要對一個業務對象應用JtaTransactionManager策略，該對象就可以橫跨多個DAO和多個Session Factory來劃分事務了。使用Spring的最大好處就是，可通過配置來聲明式地管理事務，無需對應用代碼作任何改動。