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Write operations are not allowed in read-only

程序员文章站 2022-06-06 11:29:13
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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 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:

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:

HibernateTemplate tmp=getHibernateTemplate();   
tmp.setFlushMode(HibernateTemplate.FLUSH_EAGER);  

 只要在调用HibernateTemplate涉及到写操作的方法之前正确设置了HibernateTemplate或者Session的刷新模式,则上述异常不会再抛出。