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最新评论
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coconut_zhang:
这个demo 非常完整了,是指下面说的那个html 模版,模版 ...
flying sauser, thymeleaf实现PDF文件下载 -
a93456:
你好,你有完整的demo吗? String template这 ...
flying sauser, thymeleaf实现PDF文件下载 -
yujiaao:
fn 函数循环是没有必要的啊,可以改成
protecte ...
Java 笛卡尔积算法的简单实现 -
安静听歌:
设置了.setUseTemporaryFileDuringWr ...
使用jxl导出大数据量EXCEL时内存溢出的解决办法 -
q280499693:
写的很详细,但是我现在想知道他们是怎么定位log4j.prop ...
关于SLF4J结合Log4j使用时日志输出与指定的log4j.properties不同
Spring Write operations are not allowed in read-only mode 错误
使用Spring提供的Open Session In View而引起Write operations are not allowed in read-only mode (FlushMode.NEVER) 错误解决:
在没有使用Spring提供的Open Session In View情况下,因需要在service(or Dao)层里把session关闭,所以lazy loading 为true的话,要在应用层内把关系集合都初始化,如 company.getEmployees(),否则Hibernate抛session already closed Exception; Open Session In View提供了一种简便的方法,较好地解决了lazy loading问题.
它有两种配置方式OpenSessionInViewInterceptor和OpenSessionInViewFilter(具体参看SpringSide),功能相同,只是一个在web.xml配置,另一个在application.xml配置而已。
Open Session In View在request把session绑定到当前thread期间一直保持hibernate session在open状态,使session在request的整个期间都可以使用,如在View层里PO也可以lazy loading数据,如 ${ company.employees }。当View 层逻辑完成后,才会通过Filter的doFilter方法或Interceptor的postHandle方法自动关闭session。
OpenSessionInViewInterceptor配置
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<beans>
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<bean name="openSessionInViewInterceptor"
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class="org.springframework.orm.hibernate3.support.OpenSessionInViewInterceptor">
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<property name="sessionFactory">
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<ref bean="sessionFactory"/>
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</property>
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</bean>
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<bean id="urlMapping"
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class="org.springframework.web.servlet.handler.SimpleUrlHandlerMapping">
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<property name="interceptors">
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<list>
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<ref bean="openSessionInViewInterceptor"/>
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</list>
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</property>
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<property name="mappings">
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...
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</property>
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</bean>
-
...
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</beans>
OpenSessionInViewFilter配置
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<web-app>
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...
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<filter>
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<filter-name>hibernateFilter</filter-name>
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<filter-class>
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org.springframework.orm.hibernate3.support.OpenSessionInViewFilter
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</filter-class>
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<!-- singleSession默认为true,若设为false则等于没用OpenSessionInView -->
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<init-param>
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<param-name>singleSession</param-name>
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<param-value>true</param-value>
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</init-param>
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</filter>
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...
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<filter-mapping>
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<filter-name>hibernateFilter</filter-name>
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<url-pattern>*.do</url-pattern>
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</filter-mapping>
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...
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</web-app>
很多人在使用OpenSessionInView过程中提及一个错误:
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org.springframework.dao.InvalidDataAccessApiUsageException: Write operations
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are not allowed in read-only mode (FlushMode.NEVER) - turn your Session into
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FlushMode.AUTO or remove 'readOnly' marker from transaction definition
看看OpenSessionInViewFilter里的几个方法
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protected void doFilterInternal(HttpServletRequest request,
HttpServletResponse response,FilterChain filterChain)
throws ServletException, IOException {
SessionFactory sessionFactory = lookupSessionFactory();
logger.debug("Opening Hibernate Session in OpenSessionInViewFilter");
Session session = getSession(sessionFactory);
TransactionSynchronizationManager.bindResource(
sessionFactory, new SessionHolder(session));
try {
filterChain.doFilter(request, response);
}
finally {
TransactionSynchronizationManager.unbindResource(sessionFactory);
logger.debug("Closing Hibernate Session in OpenSessionInViewFilter");
closeSession(session, sessionFactory);
}
}
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protected Session getSession(SessionFactory sessionFactory)
throws DataAccessResourceFailureException {
Session session = SessionFactoryUtils.getSession(sessionFactory, true);
session.setFlushMode(FlushMode.NEVER);
return session;
}
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protected void closeSession(Session session, SessionFactory sessionFactory)
throws CleanupFailureDataAccessException {
SessionFactoryUtils.closeSessionIfNecessary(session, sessionFactory);
}
可以看到OpenSessionInViewFilter在getSession的时候,会把获取回来的session的flush mode 设为FlushMode.NEVER。然后把该sessionFactory绑定到 TransactionSynchronizationManager,使request的整个过程都使用同一个session,在请求过后再接除该 sessionFactory的绑定,最后closeSessionIfNecessary根据该 session是否已和transaction绑定来决定是否关闭session。在这个过程中,若HibernateTemplate 发现自当前session有不是readOnly的transaction,就会获取到FlushMode.AUTO Session,使方法拥有写权限。
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public static void closeSessionIfNecessary(Session session, SessionFactory sessionFactory)
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throws CleanupFailureDataAccessException {
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if (session == null ||
TransactionSynchronizationManager.hasResource(sessionFactory)) {
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return;
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}
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logger.debug("Closing Hibernate session");
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try {
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session.close();
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}
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catch (JDBCException ex) {
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// SQLException underneath
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throw new CleanupFailureDataAccessException("Could not close Hibernate session", ex.getSQLException());
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}
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catch (HibernateException ex) {
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throw new CleanupFailureDataAccessException("Could not close Hibernate session", ex);
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}
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}
也即是,如果有不是readOnly的transaction就可以由Flush.NEVER转为Flush.AUTO,拥有 insert,update,delete操作权限,如果没有transaction,并且没有另外人为地设flush model的话,则doFilter的整个过程都是Flush.NEVER。所以受transaction保护的方法有写权限,没受保护的则没有。
采用spring的事务声明,使方法受transaction控制
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<bean id="baseTransaction"
class="org.springframework.transaction.interceptor.TransactionProxyFactoryBean"
abstract="true">
<property name="transactionManager" ref="transactionManager"/>
<property name="proxyTargetClass" value="true"/>
<property name="transactionAttributes">
<props>
<prop key="get*">PROPAGATION_REQUIRED,readOnly</prop>
<prop key="find*">PROPAGATION_REQUIRED,readOnly</prop>
<prop key="load*">PROPAGATION_REQUIRED,readOnly</prop>
<prop key="save*">PROPAGATION_REQUIRED</prop>
<prop key="add*">PROPAGATION_REQUIRED</prop>
<prop key="update*">PROPAGATION_REQUIRED</prop>
<prop key="remove*">PROPAGATION_REQUIRED</prop>
</props>
</property>
</bean>
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<bean id="userService" parent="baseTransaction">
<property name="target">
<bean class="com.phopesoft.security.service.impl.UserServiceImpl"/>
</property>
</bean>
对于上例,则以save,add,update,remove开头的方法拥有可写的事务,如果当前有某个方法,如命名为importExcel(),则因没有transaction而没有写权限,这时若方法内有insert,update,delete操作的话,则需要手动设置flush model为Flush.AUTO,如
-
session.setFlushMode(FlushMode.AUTO);
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session.save(user);
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session.flush();
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。
发表评论
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Spring Data JPA框架系列(三)-自定义Repository接口详解
2022-05-08 09:03 0前面讲了Spring Boot 整合Spring Boot ... -
flying sauser, thymeleaf实现PDF文件下载
2016-06-17 14:58 5118thymeleaf 的资料比较少,资料大部分都是和spri ... -
thymeleaf与spring整合
2016-06-15 10:08 11911、使用的是Spring EL而不是Ognl。2、访问上下文 ... -
SpringMVC 400 Bad Request 问题
2016-06-15 09:11 1912在提交表单时,发生400错误,并未进入save方法。 ... -
eclipse插件Maven添加依赖查询无结果的解决方法(Select Dependency doesn't work)
2016-04-22 08:33 701在eclipse中用过maven的可能都遇到过这种情况,我 ... -
Freemarker网站静态化的实现(转载)
2012-06-20 13:39 1376做程序也做了将近4年时间了,从来没有发过什么技术性的文章,今 ... -
SpringSecurity 3配置文件
2012-06-10 12:58 1273最近查找了一些Spring security3的资料,感觉网上 ... -
Struts2标签库
2012-05-19 21:19 1502Struts2标签库概述使用标 ... -
struts2的validate错误跳转与chain配合使用的要点
2012-05-18 16:30 1397本文基于struts2.1.8.1 按照struts2的官方文 ... -
OGNL表达式struts2标签“%,#,$”
2012-05-18 15:32 1084一、什么是OGNL,有什么特点? ... -
如何自定义Struts2表单验证后的错误信息显示格式/样式
2011-11-17 10:43 2805环境 Struts 2.1.8.1 + Myeclipse ... -
Struts2验证总结
2011-11-17 10:41 1249在Struts2应用中提供验证的方式有两种——编程式和声明式。 ... -
strtus2.0实现上传
2011-10-31 10:44 1291Struts 2是通过Commons FileUpload文件 ... -
input中disabled,readonly解决办法及区别
2011-05-27 10:35 6323input的字段当为diabled时时无法获取数值得,所以最 ... -
getCurrentSession 与 openSession() 的区别
2011-05-26 11:00 10891 getCurrentSession创建的session会和 ... -
Struts2拦截器执行顺序
2010-11-15 11:25 2686在之前的文章中,我们 ... -
struts2默认拦截器详细说明
2010-11-15 11:23 19581. 理解拦截器 1.1. 什么是拦截器: 拦 ... -
Struts2向JasperReport传参数配置
2010-10-26 10:11 1627Recently I spent a whole day se ... -
struts2与jasperreport整合不能显示图片imgags/px
2010-09-08 13:37 2499终结解决方案:Struts2整 ... -
hibernate配置参数
2009-04-03 23:55 1300Hibernate输出SQL语句以便更加深入调试程序----参 ...
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