spring hibernate 事务管理

HibernateDaoSupport的子类在保存实体时抛出InvalidDataAccessApiUsageException异常，异常堆栈如下：
org.springframework.dao.InvalidDataAccessApiUsageException: Write operations are not allowed in read-only mode (FlushMode.NEVER/MANUAL): Turn your Session into FlushMode.COMMIT/AUTO or remove 'readOnly' marker from transaction definition.
at org.springframework.orm.hibernate3.HibernateTemplate.checkWriteOperationAllowed(HibernateTemplate.java:1090)
at org.springframework.orm.hibernate3.HibernateTemplate$12.doInHibernate(HibernateTemplate.java:629)
at org.springframework.orm.hibernate3.HibernateTemplate.execute(HibernateTemplate.java:367)
at org.springframework.orm.hibernate3.HibernateTemplate.save(HibernateTemplate.java:627)
在网上搜了一下，其中大多数文章又是提OpenSessionInViewFilter又是提OpenSessionInViewInterceptor的，大多云山雾罩、不知所云。
其实这个异常的提示还是很明确的：在只读模式下(FlushMode.NEVER/MANUAL)写操作不被允许：把你的Session改成FlushMode.COMMIT/AUTO或者清除事务定义中的readOnly标记。
首先看一下我Spring的配置文件，为了减少篇幅，仅将与事务有关的一部分贴在下面：

Xml代码

<?xml version="1.0" encoding="UTF-8"?>

<!DOCTYPE beans PUBLIC "-//SPRING//DTD BEAN//EN" "http://www.springframework.org/dtd/spring-beans.dtd">

<beans>

<!-- Transaction template for Managers, from:
http://blog.exis.com/colin/archives/2004/07/31/concise-transaction-definitions-spring-11/ -->

<bean id="txProxyTemplate" abstract="true"

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

<property name="transactionManager">

<!--org.springframework.orm.hibernate3.HibernateTransactionManager的Bean实例-->

<ref bean="gkgltransactionManager" />

</property>

<property name="transactionAttributes">

<props>

<prop key="save*">PROPAGATION_REQUIRED</prop>

<prop key="remove*">PROPAGATION_REQUIRED</prop>

<prop key="do*">PROPAGATION_SUPPORTS</prop>

<prop key="auto*">PROPAGATION_SUPPORTS</prop>

<!--对于其它方法要求事务并且是只读的-->

<prop key="*">PROPAGATION_SUPPORTS,readOnly</prop>

</props>

</property>

</bean>

<!-- Generic manager that can be used to do basic CRUD operations on any objects -->

<bean id="manager" parent="txProxyTemplate">

<property name="target">

<bean class="com.neuqsoft.base.service.impl.BaseManager">

<property name="dao">

<ref bean="gkgldao" />

</property>

</bean>

</property>

</bean>

</beans>

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE beans PUBLIC "-//SPRING//DTD BEAN//EN" "http://www.springframework.org/dtd/spring-beans.dtd">
<beans>
<!-- Transaction template for Managers, from: http://blog.exis.com/colin/archives/2004/07/31/concise-transaction-definitions-spring-11/ -->
<bean id="txProxyTemplate" abstract="true"
class="org.springframework.transaction.interceptor.TransactionProxyFactoryBean">
<property name="transactionManager">
<!--org.springframework.orm.hibernate3.HibernateTransactionManager的Bean实例-->
<ref bean="gkgltransactionManager" />
</property>
<property name="transactionAttributes">
<props>
<prop key="save*">PROPAGATION_REQUIRED</prop>
<prop key="remove*">PROPAGATION_REQUIRED</prop>
<prop key="do*">PROPAGATION_SUPPORTS</prop>
<prop key="auto*">PROPAGATION_SUPPORTS</prop>
<!--对于其它方法要求事务并且是只读的-->
<prop key="*">PROPAGATION_SUPPORTS,readOnly</prop>
</props>
</property>
</bean>
<!-- Generic manager that can be used to do basic CRUD operations on any objects -->
<bean id="manager" parent="txProxyTemplate">
<property name="target">
<bean class="com.neuqsoft.base.service.impl.BaseManager">
<property name="dao">
<ref bean="gkgldao" />
</property>
</bean>
</property>
</bean>
</beans>

对于清除readOnly标记是很简单的，只需把上述配置文件中txProxyTemplate Bean定义中的<prop key="*">PROPAGATION_SUPPORTS,readOnly</prop>中的readOnly及其前面的逗号去掉即可。
接下来我们讨论把Session改成FlushMode.COMMIT/AUTO，下面是HibernateTemplate中checkWriteOperationAllowed方法的源码：

Java代码

protected void checkWriteOperationAllowed(Session session) throws InvalidDataAccessApiUsageException {

if (isCheckWriteOperations() && getFlushMode() != FLUSH_EAGER &&

session.getFlushMode().lessThan(FlushMode.COMMIT)) {

throw new InvalidDataAccessApiUsageException(

"Write operations are not allowed in read-only mode (FlushMode.NEVER/MANUAL): "+

"Turn your Session into FlushMode.COMMIT/AUTO or remove 'readOnly' marker from transaction definition.");

}

}

protected void checkWriteOperationAllowed(Session session) throws InvalidDataAccessApiUsageException {
if (isCheckWriteOperations() && getFlushMode() != FLUSH_EAGER &&
session.getFlushMode().lessThan(FlushMode.COMMIT)) {
throw new InvalidDataAccessApiUsageException(
"Write operations are not allowed in read-only mode (FlushMode.NEVER/MANUAL): "+
"Turn your Session into FlushMode.COMMIT/AUTO or remove 'readOnly' marker from transaction definition.");
}
}

通过阅读这段代码我们不难看出，在Java代码中调用HibernateTemplate的save或者saveOrUpdate等涉及到写操作的方法之前需要把Session的刷新模式设置为FlushMode.COMMIT或更高的级别，或者把HibernateTemplate的刷新模式设置为FLUSH_EAGER，由于我们的Dao继承自HibernateDaoSupport，所以设置Session刷新模式的语句如下：getSession().setFlushMode(FlushMode.COMMIT);
而设置HibernateTemplate刷新模式的语句如下：

Java代码

HibernateTemplate tmp=getHibernateTemplate();

tmp.setFlushMode(HibernateTemplate.FLUSH_EAGER);