session丢失造成的action不能实例化异常

org.springframework.beans.BeanInstantiationException: Could not instantiate bean class

项目中自定义拦截器对登录用户信息进行拦截,以及struts2的默认拦截器,当session丢失的时候,就会被拦截器拦截.不能进行实例化;

我所造成的原因是在action中使用全局变量,并动态获取值,当session丢失后,action不能实例化而类中的全局变量在赋值所引发的异常;

Unable to instantiate Action, classInfoAction,  defined for 'classInfo_teacherSet' in namespace '/'Error creating bean with name 'classInfoAction' defined in file [E:\Tomcat\pajx-pdm-tomcat-7.0.42\webapps\PAJX_DMP\WEB-INF\classes\com\kh\pajx\dmp\view\action\ClassInfoAction.class]: Instantiation of bean failed; nested exception is org.springframework.beans.BeanInstantiationException: Could not instantiate bean class [com.kh.pajx.dmp.view.action.ClassInfoAction]: Constructor threw exception; nested exception is java.lang.NullPointerException
 at com.opensymphony.xwork2.DefaultActionInvocation.createAction(DefaultActionInvocation.java:316)
 at com.opensymphony.xwork2.DefaultActionInvocation.init(DefaultActionInvocation.java:397)
 at com.opensymphony.xwork2.DefaultActionProxy.prepare(DefaultActionProxy.java:194)
 at org.apache.struts2.impl.StrutsActionProxy.prepare(StrutsActionProxy.java:63)
 at org.apache.struts2.impl.StrutsActionProxyFactory.createActionProxy(StrutsActionProxyFactory.java:37)
 at com.opensymphony.xwork2.DefaultActionProxyFactory.createActionProxy(DefaultActionProxyFactory.java:58)
 at org.apache.struts2.dispatcher.Dispatcher.serviceAction(Dispatcher.java:552)
 at org.apache.struts2.dispatcher.ng.ExecuteOperations.executeAction(ExecuteOperations.java:77)
 at org.apache.struts2.dispatcher.ng.filter.StrutsPrepareAndExecuteFilter.doFilter(StrutsPrepareAndExecuteFilter.java:99)
 at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:243)
 at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
 at org.springframework.orm.hibernate3.support.OpenSessionInViewFilter.doFilterInternal(OpenSessionInViewFilter.java:232)
 at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:106)
 at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:243)
 at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
 at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:222)
 at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:123)
 at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:502)
 at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:171)
 at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:99)
 at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:953)
 at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118)
 at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:408)
 at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1023)
 at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:589)
 at org.apache.tomcat.util.net.AprEndpoint$SocketProcessor.run(AprEndpoint.java:1852)
 at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
 at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
 at java.lang.Thread.run(Thread.java:744)
Caused by: org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'classInfoAction' defined in file [E:\Tomcat\pajx-pdm-tomcat-7.0.42\webapps\PAJX_DMP\WEB-INF\classes\com\kh\pajx\dmp\view\action\ClassInfoAction.class]: Instantiation of bean failed; nested exception is org.springframework.beans.BeanInstantiationException: Could not instantiate bean class [com.kh.pajx.dmp.view.action.ClassInfoAction]: Constructor threw exception; nested exception is java.lang.NullPointerException
 at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.instantiateBean(AbstractAutowireCapableBeanFactory.java:1037)
 at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBeanInstance(AbstractAutowireCapableBeanFactory.java:970)
 at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:487)
 at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:458)
 at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:315)
 at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:194)
 at org.springframework.context.support.AbstractApplicationContext.getBean(AbstractApplicationContext.java:1117)
 at com.opensymphony.xwork2.spring.SpringObjectFactory.buildBean(SpringObjectFactory.java:151)
 at com.opensymphony.xwork2.ObjectFactory.buildBean(ObjectFactory.java:171)
 at com.opensymphony.xwork2.factory.DefaultActionFactory.buildAction(DefaultActionFactory.java:22)
 at com.opensymphony.xwork2.ObjectFactory.buildAction(ObjectFactory.java:141)
 at com.opensymphony.xwork2.DefaultActionInvocation.createAction(DefaultActionInvocation.java:297)
 ... 28 more
Caused by: org.springframework.beans.BeanInstantiationException: Could not instantiate bean class [com.kh.pajx.dmp.view.action.ClassInfoAction]: Constructor threw exception; nested exception is java.lang.NullPointerException
 at org.springframework.beans.BeanUtils.instantiateClass(BeanUtils.java:163)
 at org.springframework.beans.factory.support.SimpleInstantiationStrategy.instantiate(SimpleInstantiationStrategy.java:87)
 at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.instantiateBean(AbstractAutowireCapableBeanFactory.java:1030)
 ... 39 more
Caused by: java.lang.NullPointerException
 at com.kh.pajx.dmp.view.action.ClassInfoAction.<init>(ClassInfoAction.java:48)
 at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
 at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:57)
 at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
 at java.lang.reflect.Constructor.newInstance(Constructor.java:526)
 at org.springframework.beans.BeanUtils.instantiateClass(BeanUtils.java:148)
 ... 41 more