转自：http://blog.51cto.com/alinazh/1276363
在启动tomcat的时候出现错误：
Line: 220 - com/opensymphony/xwork2/spring/SpringObjectFactory.java:220:-1 .
严重: Exception starting filter struts2
Class: com.opensymphony.xwork2.spring.SpringObjectFactory
File: SpringObjectFactory.java
Method: getClassInstance
Line: 220 - com/opensymphony/xwork2/spring/SpringObjectFactory.java:220:-1
at org.apache.struts2.dispatcher.Dispatcher.init(Dispatcher.java:437)
at org.apache.struts2.dispatcher.FilterDispatcher.init(FilterDispatcher.java:195)
at org.apache.catalina.core.ApplicationFilterConfig.getFilter(ApplicationFilterConfig.java:275)
at org.apache.catalina.core.ApplicationFilterConfig.setFilterDef(ApplicationFilterConfig.java:397)
at org.apache.catalina.core.ApplicationFilterConfig.<init>(ApplicationFilterConfig.java:108)
at org.apache.catalina.core.StandardContext.filterStart(StandardContext.java:3709)
at org.apache.catalina.core.StandardContext.start(StandardContext.java:4356)
at org.apache.catalina.core.ContainerBase.addChildInternal(ContainerBase.java:791)
at org.apache.catalina.core.ContainerBase.addChild(ContainerBase.java:771)
at org.apache.catalina.core.StandardHost.addChild(StandardHost.java:525)
at org.apache.catalina.startup.HostConfig.deployDescriptor(HostConfig.java:626)
at org.apache.catalina.startup.HostConfig.deployDescriptors(HostConfig.java:553)
at org.apache.catalina.startup.HostConfig.deployApps(HostConfig.java:488)
at org.apache.catalina.startup.HostConfig.check(HostConfig.java:1215)
at org.apache.catalina.startup.HostConfig.lifecycleEvent(HostConfig.java:293)
at org.apache.catalina.util.LifecycleSupport.fireLifecycleEvent(LifecycleSupport.java:117)
at org.apache.catalina.core.ContainerBase.backgroundProcess(ContainerBase.java:1337)
at org.apache.catalina.core.ContainerBase$ContainerBackgroundProcessor.processChildren(ContainerBase.java:1601)
at org.apache.catalina.core.ContainerBase$ContainerBackgroundProcessor.processChildren(ContainerBase.java:1610)
at org.apache.catalina.core.ContainerBase$ContainerBackgroundProcessor.run(ContainerBase.java:1590)
at java.lang.Thread.run(Unknown Source)
Caused by: java.lang.NullPointerException
at com.opensymphony.xwork2.spring.SpringObjectFactory.getClassInstance(SpringObjectFactory.java:220)
at com.opensymphony.xwork2.config.providers.XmlConfigurationProvider.verifyResultType(XmlConfigurationProvider.java:530)
at com.opensymphony.xwork2.config.providers.XmlConfigurationProvider.addResultTypes(XmlConfigurationProvider.java:501)
at com.opensymphony.xwork2.config.providers.XmlConfigurationProvider.addPackage(XmlConfigurationProvider.java:457)
at com.opensymphony.xwork2.config.providers.XmlConfigurationProvider.loadPackages(XmlConfigurationProvider.java:275)
at org.apache.struts2.config.StrutsXmlConfigurationProvider.loadPackages(StrutsXmlConfigurationProvider.java:111)
at com.opensymphony.xwork2.config.impl.DefaultConfiguration.reloadContainer(DefaultConfiguration.java:204)
at com.opensymphony.xwork2.config.ConfigurationManager.getConfiguration(ConfigurationManager.java:66)
at org.apache.struts2.dispatcher.Dispatcher.init_PreloadConfiguration(Dispatcher.java:380)
at org.apache.struts2.dispatcher.Dispatcher.init(Dispatcher.java:424)
... 20 more
原因及解决办法：
不要引入包:struts2-spring-plugin-2.2.3.jar.
就是这么简单。
需要注意的是，这里指的不要引入，是在web工程的WEBROOT/WEB-INF/lib中也不要有多余的包，之前我的问题是lib中的包有冲突，
只在工程的buildpath中不引入，这个是不能控制包的冲突的！！
类似的问题及解决
启动服务器时出现异常：
警告: Failed startup of context com.google.apphosting.utils.jetty.DevAppEngineWebAppContext@1242b11{/,E:workspaceuploadPhotowar}
Class: com.opensymphony.xwork2.spring.SpringObjectFactory
File: SpringObjectFactory.java
Method: getClassInstance
Line: 209 - com/opensymphony/xwork2/spring/SpringObjectFactory.java:209:-1
Caused
by: java.lang.NullPointerException at
com.opensymphony.xwork2.spring.SpringObjectFactory.getClassInstance(SpringObjectFactory.java:209)
原因两个：
1.lib中多导入包的大原因：去掉struts2-spring-plugin-2.1.8包即可，因为没有用到spring。
2.还有的原因是用spring了，却没加监听器，在web.xml里面加上
<listener>
<listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
</listener>