Write operations are not allowed in read-only

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  

1. <?xml version="1.0" encoding="UTF-8"?>  
2. <!DOCTYPE beans PUBLIC "-//SPRING//DTD BEAN//EN" "http://www.springframework.org/dtd/spring-beans.dtd">  
3. <beans>  
4.     <!-- Transaction template for Managers, from:   
5.         http://blog.exis.com/colin/archives/2004/07/31/concise-transaction-definitions-spring-11/ -->  
6.     <bean id="txProxyTemplate" abstract="true"    
7.         class="org.springframework.transaction.interceptor.TransactionProxyFactoryBean">  
8.         <property name="transactionManager">  
9.             <!--org.springframework.orm.hibernate3.HibernateTransactionManager的Bean实例-->  
10.             <ref bean="gkgltransactionManager" />  
11.         </property>  
12.         <property name="transactionAttributes">  
13.             <props>  
14.                 <prop key="save*">PROPAGATION_REQUIRED</prop>  
15.                 <prop key="remove*">PROPAGATION_REQUIRED</prop>  
16.                 <prop key="do*">PROPAGATION_SUPPORTS</prop>    
17.                 <prop key="auto*">PROPAGATION_SUPPORTS</prop>  
18.                 <!--对于其它方法要求事务并且是只读的-->  
19.                 <prop key="*">PROPAGATION_SUPPORTS,readOnly</prop>  
20.             </props>  
21.         </property>  
22.     </bean>  
23.     <!-- Generic manager that can be used to do basic CRUD operations on any objects -->  
24.     <bean id="manager" parent="txProxyTemplate">  
25.         <property name="target">  
26.             <bean class="com.neuqsoft.base.service.impl.BaseManager">  
27.                 <property name="dao">  
28.                     <ref bean="gkgldao" />  
29.                 </property>  
30.             </bean>  
31.         </property>  
32.     </bean>  
33. </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  

1. protected void checkWriteOperationAllowed(Session session) throws InvalidDataAccessApiUsageException {   
2.         if (isCheckWriteOperations() && getFlushMode() != FLUSH_EAGER &&   
3.                 session.getFlushMode().lessThan(FlushMode.COMMIT)) {   
4.             throw new InvalidDataAccessApiUsageException(   
5.                     "Write operations are not allowed in read-only mode (FlushMode.NEVER/MANUAL): "+   
6.                     "Turn your Session into FlushMode.COMMIT/AUTO or remove 'readOnly' marker from transaction definition.");   
7.         }   
8.     }  

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  

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

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。