懒加载问题

 在进行OA系统中用户管理的相关部署，配置到服务器后发现访问报异常

异常情况如下:

org.apache.jasper.JasperException: org.hibernate.LazyInitializationException: failed to lazily initialize a collection of role: com.jxust.oa.domain.User.roles, no session or session was closed

    org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:556)
    org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:477)
    org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:395)
    org.apache.jasper.servlet.JspServlet.service(JspServlet.java:339)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:731)
    org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:303)
    org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
    org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
    org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
    org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
    org.apache.catalina.core.ApplicationDispatcher.invoke(ApplicationDispatcher.java:748)
    org.apache.catalina.core.ApplicationDispatcher.processRequest(ApplicationDispatcher.java:486)
    org.apache.catalina.core.ApplicationDispatcher.doForward(ApplicationDispatcher.java:411)
    org.apache.catalina.core.ApplicationDispatcher.forward(ApplicationDispatcher.java:338)
    org.apache.struts2.dispatcher.ServletDispatcherResult.doExecute(ServletDispatcherResult.java:164)
    org.apache.struts2.dispatcher.StrutsResultSupport.execute(StrutsResultSupport.java:191)
    com.opensymphony.xwork2.DefaultActionInvocation.executeResult(DefaultActionInvocation.java:369)
    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:273)
org.hibernate.LazyInitializationException: failed to lazily initialize a collection of role: com.jxust.oa.domain.User.roles, no session or session was closed

    org.hibernate.collection.AbstractPersistentCollection.throwLazyInitializationException(AbstractPersistentCollection.java:383)
    org.hibernate.collection.AbstractPersistentCollection.throwLazyInitializationExceptionIfNotConnected(AbstractPersistentCollection.java:375)
    org.hibernate.collection.AbstractPersistentCollection.initialize(AbstractPersistentCollection.java:368)
    org.hibernate.collection.AbstractPersistentCollection.read(AbstractPersistentCollection.java:111)
    org.hibernate.collection.PersistentSet.iterator(PersistentSet.java:186)
    org.apache.struts2.util.MakeIterator.convert(MakeIterator.java:82)
    org.apache.struts2.components.IteratorComponent.start(IteratorComponent.java:269)
    org.apache.struts2.views.jsp.ComponentTagSupport.doStartTag(ComponentTagSupport.java:54)
    org.apache.jsp.WEB_002dINF.jsp.userAction.list_jsp._jspx_meth_s_005fiterator_0

通过异常的描述和在网上查资料后发现这个是懒加载异常，就是在查询时没有加载关联表的对象，你读取这个关联对象的时候，hibernate的session已经关闭，所以无法获取对象。

解决办法是在web.xml中配置Spring的

<!-- 配置Spring的OpenSessionInViewFilter，以解决懒加载异常的问题 -->
	<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>

<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.5" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee 
	http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">

	<welcome-file-list>
		<welcome-file>index.jsp</welcome-file>
	</welcome-file-list>
	<!--在启动Web容器时，自动装配Spring applicationContext.xml的配置信息。自动的将其中的bean初始化 -->
	<!-- 容器初始化在这步完成 -->

	<!-- 配置spring的监听器用于初始化ApplicationContext对象 -->
	<listener>
		<listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
	</listener>
	<context-param>
		<param-name>contextConfigLocation</param-name>
		<param-value>classpath:applicationContext*.xml</param-value>
	</context-param>

	<!-- 配置Spring的OpenSessionInViewFilter，以解决懒加载异常的问题 -->
	<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>

	<!-- 配置struts2的主过滤器 -->
	<filter>
		<filter-name>struts2</filter-name>
		<filter-class>org.apache.struts2.dispatcher.ng.filter.StrutsPrepareAndExecuteFilter</filter-class>
	</filter>

	<filter-mapping>
		<filter-name>struts2</filter-name>
		<url-pattern>/*</url-pattern>
	</filter-mapping>

</web-app>

问题解决，成功得到预期效果