一下web.xml里面加入struts2的filter就出错。 急啊！！
我一在web.xml里面加入struts2的filter就出错，我弄来弄出都不知道为什么，但是我把整个project拿回到公司运行，结果一点错误都没，很奇怪。。 希望你能帮我解决一下。。

严重: Exception starting filter struts2 
Error loading configuration file struts-default.xml - Class: com.opensymphony.xwork2.config.providers.XmlConfigurationProvider 
File: XmlConfigurationProvider.java 
Method: loadConfigurationFiles 
Line: 850 - com/opensymphony/xwork2/config/providers/XmlConfigurationProvider.java:850:-1 
at com.opensymphony.xwork2.config.providers.XmlConfigurationProvider.loadDocuments(XmlConfigurationProvider.java:135) 
at com.opensymphony.xwork2.config.providers.XmlConfigurationProvider.init(XmlConfigurationProvider.java:100) 
at com.opensymphony.xwork2.config.impl.DefaultConfiguration.reload(DefaultConfiguration.java:130) 
at com.opensymphony.xwork2.config.ConfigurationManager.getConfiguration(ConfigurationManager.java:52) 
at org.apache.struts2.dispatcher.Dispatcher.init_PreloadConfiguration(Dispatcher.java:395) 
at org.apache.struts2.dispatcher.Dispatcher.init(Dispatcher.java:452) 
at org.apache.struts2.dispatcher.FilterDispatcher.init(FilterDispatcher.java:201) 
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:3693) 
at org.apache.catalina.core.StandardContext.start(StandardContext.java:4342) 
at org.apache.catalina.core.ContainerBase.addChildInternal(ContainerBase.java:761) 
at org.apache.catalina.core.ContainerBase.addChild(ContainerBase.java:741) 
at org.apache.catalina.core.StandardHost.addChild(StandardHost.java:525) 
at org.apache.catalina.startup.HostConfig.deployDirectory(HostConfig.java:920) 
at org.apache.catalina.startup.HostConfig.deployDirectories(HostConfig.java:883) 
at org.apache.catalina.startup.HostConfig.deployApps(HostConfig.java:492) 
at org.apache.catalina.startup.HostConfig.start(HostConfig.java:1138) 
at org.apache.catalina.startup.HostConfig.lifecycleEvent(HostConfig.java:311) 
at org.apache.catalina.util.LifecycleSupport.fireLifecycleEvent(LifecycleSupport.java:120) 
at org.apache.catalina.core.ContainerBase.start(ContainerBase.java:1023) 
at org.apache.catalina.core.StandardHost.start(StandardHost.java:719) 
at org.apache.catalina.core.ContainerBase.start(ContainerBase.java:1015) 
at org.apache.catalina.core.StandardEngine.start(StandardEngine.java:443) 
at org.apache.catalina.core.StandardService.start(StandardService.java:448) 
at org.apache.catalina.core.StandardServer.start(StandardServer.java:710) 
at org.apache.catalina.startup.Catalina.start(Catalina.java:552) 
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) 
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39) 
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) 
at java.lang.reflect.Method.invoke(Method.java:582) 
at org.apache.catalina.startup.Bootstrap.start(Bootstrap.java:288) 
at org.apache.catalina.startup.Bootstrap.main(Bootstrap.java:413) 
Caused by: java.lang.NullPoin