解决session 关闭问题 WARN - unclosed connection, forgot to call close() on your session?
2011-03-02 17:12
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的SSH项目之旅(6.session问题解决) - [java]2008-08-07Tag:java spring hibernate struts session 版权声明:转载时请以超链接形式标明文章原始出处和作者信息及本声明 http://fantlam.blogbus.com/logs/27339525.html 2008-07-20 22:25:27,531 INFO [org.springframework.beans.factory.xml.XmlBeanDefinitionReader] - Loading XML bean definitions from class path resource [org/springframework/jdbc/support/sql-error-codes.xml] 2008-07-20 22:25:27,609 INFO [org.springframework.jdbc.support.SQLErrorCodesFact ory] - SQLErrorCodes loaded: [DB2, HSQL, MS-SQL, MySQL, Oracle, Informix, PostgreSQL, Sybase] 2008-07-20 22:26:48,437 WARN [org.hibernate.jdbc.ConnectionManager] - finalizingwith closed connection 2008-07-20 22:26:48,437 WARN [org.hibernate.jdbc.ConnectionManager] - unclosed connection, forgot to call close() on your session? Hibernate: select item0_.itemid as itemid, item0_.itemname as itemname1_, item0_.itemcode as itemcode1_ from item item0_ 2008-07-22 20:54:56,375 WARN [org.hibernate.jdbc.ConnectionManager] – finalizing with closed connection 2008-07-22 20:56:32,812 WARN [org.hibernate.util.JDBCExceptionReporter] - SQL Error: 0, SQLState: null 2008-07-22 20:56:32,812 ERROR [org.hibernate.util.JDBCExceptionReporter] - Cannot get a connection, pool error Timeout waiting for idle object 2008-07-22 20:56:32,828 WARN [org.hibernate.util.JDBCExceptionReporter] - SQL Error: 0, SQLState: null 2008-07-22 20:56:32,828 ERROR [org.hibernate.util.JDBCExceptionReporter] - Cannot get a connection, pool error Timeout waiting for idle object org.hibernate.exception.GenericJDBCException: Cannot open connection 终于找到解决办法了 ,我们来看下面的内容吧 ItemDAOImpl.java public class ItemDAOImpl extends HibernateDaoSupport implements ItemDAO { public List queryAll() throws Exception { // TODO Auto-generated method stub Session session=super.getSession(true); String hql="from Item as i"; List l=super.getSession().createQuery(hql).list(); return l; } }/ 其实上面的代码隐藏了一个问题,数据库连接并没有被关闭,所以一直出现以上的问题。 我这里提供三个解决方案 方案一: 用此种方法,虽然没有手动关闭数据库连接,但spring已经帮我们关闭了 return super.getHibernateTemplate().find(hql); 方案二:(经测试,此方案比较有效) 设定HibernateTemplate的AllowCreate为True 在spring API 的HibernateDaoSupport中 protected net.sf.hibernate.Session getSession(boolean allowCreate) Get a Hibernate Session, either from the current transaction or a new one. public class ItemDAOImpl extends HibernateDaoSupport implements ItemDAO { public List queryAll() throws Exception { // TODO Auto-generated method stub Session session=super.getSession(true); String hql="from Item as i"; List l=session.createQuery(hql).list(); try{ return l; }finally{ session.close(); } } } 方案三: Spring API: geSession()是org.springframework.orm.hibernate3.support.HibernateDaoSupport 中的一个方法, 它可以从当前事务或者一个新的事务获得一个hibernate session. 通常使用releaseSession(org.hibernate.Session)方法与getSession()配合。 如果没有绑定线程,releaseSession关闭由这个DAO的SessionFactory创建的Hibernate Session。 修改后的代码如下: public class ItemDAOImpl extends HibernateDaoSupport implements ItemDAO { public List queryAll() throws Exception { // TODO Auto-generated method stub Session session = super.getSession(); String hql = "from Item as i"; List l = session.createQuery(hql).list(); releaseSession(session); } } 困扰了几天的问题终于解决了,项目搁浅了好几天了,就是对spring对session的管理不清楚。 org.hibernate.LazyInitializationException: failed to lazily initialize a collection of role: dj.fantlam.myssh.vo.Item.subitems - no session or session was closed 这是一个关于延迟加载的问题 在applicationContext.xml加入 <bean id="hibernateInterceptor" class="org.springframework.orm.hibernate3.HibernateInterceptor"> <property name="sessionFactory"> <ref bean="sessionFactory" /> </property> </bean> 在业务逻辑层中使用延迟加载 即使在视图外面,Spring框架也通过使用AOP 拦截器 HibernateInterceptor来使得延迟加载变得很容易实现。这个Hibernate 拦截器透明地将调用配置在Spring应用程序上下文中的业务对象中方法的请求拦截下来,在调用方法之前打开一个Hibernate会话,然后在方法执行完之后将会话关闭。 以及 Item.hbm.xml <set name="subitems" inverse="true" cascade="all” talbe=”subitem” 表示一对多 lazy="false" order-by="subcode"> <key> <column name="itemid" /> </key> <one-to-many class="dj.fantlam.myssh.vo.Subitem" /> </set> 问题得以解决 上网查了一些资料 hibernate一对多session关闭问题 <filter> <filter-name>opensession</filter-name> <filter-class> org.springframework.orm.hibernate3.support.OpenSessionInViewFilter </filter-class> </filter> <filter-mapping> <filter-name>opensession</filter-name> <url-pattern>*.do</url-pattern> </filter-mapping> openSessionInView的意思就是延长session的生命周期,到了jsp层,session依然有效,所以就可以正确读取一对多的多方的属性值了 2008-07-25 21:47:31,031 ERROR [org.apache.catalina.core.ContainerBase.[Catalina] .[localhost].[/myssh].[jsp]] - Servlet.service() for servlet jsp threw exception java.lang.IllegalStateException: getOutputStream() has already been called for this response 原因是image.jsp的问题 由于jsp container在处理完成请求后会调用releasePageContet方法释放所用的PageContext object,并且同时调用getWriter方法,由于getWriter方法与在jsp页面中使用流相关的getOutputStream方法冲突,所以会造成这种异常, 解决方法 在最后加上 out.clear(); out = pageContext.pushBody(); Question.hbm.xml <set name="answers" inverse="true" table="answer"> <key> <column name="qid" /> </key> <one-to-many class="dj.fantlam.myssh.vo.Answer" /> </set> 刚刚在http://localhost:8888/myssh/jsp/show.do?qid=6&status=selectid这块出现了延迟加载的问题,也就是question_show.jsp <logic:iterate id="ans" name="question" property="answers"> </logic:iterate>读 answers的时候没读到 然后我在Question.hbm.xml加上lazy="false"就行了 <set name="answers" inverse="true" table="answer" lazy="false"> <key> <column name="qid" /> </key> <one-to-many class="dj.fantlam.myssh.vo.Answer" /> </set> 今天我又发现了一个问题,原来之前的解决方案是多余的。我就是觉得很奇怪,前段日子就是怎么测都是session关闭了,真的很莫名其妙。实际上OpenSessionInViewFilter这个配置就是解决在web层session的问题,而之前我配了之后不起作用,现在想想原因应该是tomcat里的项目之间的干扰吧,因为如今我把一些别的项目去掉了,问题就没了(不过当时我是有在虚拟机做测试的,一个新的tomcat也同样出问题,百思不得其解,再测试一下再说吧,以后有问题再补充)。害得我走了冤枉路,还到论坛里问了许久。总结一下,就是利用hibernateTemplate或者是直接利用hibernateDAOSupport类来取得session 这两种方法都可以自动处理session的,前一种是spring机制,而后一种是hibernate机制。 2008-08-06 17:15:13,272 INFO [org.springframework.orm.hibernate3.support.OpenSessionInViewFilter] - Initializing filter 'opensession' 2008-08-06 17:15:13,444 INFO [org.springframework.core.CollectionFactory] - JDK 1.4+ collections available 2008-08-06 17:15:13,475 INFO [org.springframework.core.CollectionFactory] - Commons Collections 3.x available 2008-08-06 17:15:13,490 INFO [org.springframework.orm.hibernate3.support.OpenSessionInViewFilter] - Filter 'opensession' configured successfully 经过测试 不配置OpenSessionInViewFilter的话在网页读取的时候就会发生session问题 网上有这么一种说法 --------------------------------------------------------------------------------------------------- struts跟spring的整合是在struts-config.xml里加了个plugin <plug-in className="org.springframework.web.struts.ContextLoaderPlugIn"> <set-property property="contextConfigLocation" value="/WEB-INF/classes/applicationContext.xml" /> </plug-in> 这一段必须去掉 在web.xml加上 <listener> <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class> </listener> 保证openSessionInView的正常使用 经过我的测试,此方法有道理。我们先来看看spring整合struts的方法吧。两者整合的一种通用配置:在web.xml中加入一下任意一种 1、 <listener> <listener-class> org.springframework.web.context.ContextLoaderListener </listener-class> </listener> 2、 <servlet> <servlet-name>context</servlet-name> <servlet-class> org.springframework.web.context.ContextLoaderServlet </servlet-class> <load-on-startup>1</load-on-startup> </servlet> 为了让spring ApplicationContext实例化,作为IOC容器,必须优先加载,一种常见的做法是在web.xml加载spring容器。所以以上2种方法都是一样的,ContextLoaderListener和ContextLoaderServlet底层都依赖ContextLoader,因此两者效果几乎没有什么区别。在Servlet2.3标准中才出现ContextLoaderListener,它比ContextLoaderServlet会优先加载。 现在我得出的结论是之前是OpenSessionInViewFilter不起作用,如果我不把plugin 去掉的话问题依旧。经过测试,我不加plugin问题就没了。(若以后有相关问题再继续讨论)
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