申明式事务和OpenSessionInView

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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.

今天在做事务测试的时候,控制台输出了以上的错误信息,在网上找了一下,原来是我在web.xml
文件中设置了OpenSessionInView .将设置去掉就可以了.
<!-- OpenSessionInView -->
<filter>
<filter-name>OpenSessionInViewFilter</filter-name>
<filter-class>org.springframework.orm.hibernate3.support.OpenSessionInViewFilter</filter-class>
</filter>
<filter-mapping>
<filter-name>OpenSessionInViewFilter</filter-name>
<url-pattern>*.action</url-pattern>
</filter-mapping>
或者加上事务设置

<?xml version="1.0" encoding="UTF-8"?>
<beans
xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:aop="http://www.springframework.org/schema/aop"
xmlns:tx="http://www.springframework.org/schema/tx"
xsi:schemaLocation="
http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans-2.0.xsd
http://www.springframework.org/schema/tx
http://www.springframework.org/schema/tx/spring-tx-2.0.xsd
http://www.springframework.org/schema/aop
http://www.springframework.org/schema/aop/spring-aop-2.0.xsd"
>
<bean id="transactionManager" class="org.springframework.orm.hibernate3.HibernateTransactionManager">
<property name="sessionFactory" ref="sessionFactory"></property>
</bean>

<tx:advice id="txAdvice" transaction-manager="transactionManager">
<tx:attributes>
<tx:method name="create*" propagation="REQUIRED"/>
<tx:method name="update*" propagation="REQUIRED"/>
<tx:method name="delete*" propagation="REQUIRED"/>
<tx:method name="find*" propagation="REQUIRED" read-only="true"/>
<tx:method name="*" read-only="true"/>
</tx:attributes>
</tx:advice>

<aop:config>
<aop:pointcut id="daoOperation" expression="execution(* dgut.ke.dao.*.*(..))"/>
<aop:advisor advice-ref="txAdvice" pointcut-ref="daoOperation"/>
</aop:config>

</beans>

网上又说
尽管Open Session In View看起来还不错，其实副作用不少。看回上面OpenSessionInViewFilter的doFilterInternal方法代码，这个方法实际上是被父类的doFilter调用的，因此，我们可以大约了解的OpenSessionInViewFilter调用流程: request(请求)->open session并开始transaction->controller->View(Jsp)->结束transaction并close session.

一切看起来很正确，尤其是在本地开发测试的时候没出现问题，但试想下如果流程中的某一步被阻塞的话，那在这期间connection就一直被占用而不释放。最有可能被阻塞的就是在写Jsp这步，一方面可能是页面内容大，response.write的时间长，另一方面可能是网速慢，服务器与用户间传输时间久。当大量这样的情况出现时，就有连接池连接不足，造成页面假死现象。

Open Session In View是个双刃剑，放在公网上内容多流量大的网站请慎用。