Exception starting filter struts2 java.lang.NullPointerException 解决方法!!!!

<constant name="struts.devMode" value="true"/> 或者

<constant name="struts.configuration.xml.reload" value="true"/>

现在你的struts.xml里面看看,肯定有这样的代码....如果有就继续往下看吧.....

org.apache.catalina.core.StandardContext filterStart   
严重: Exception starting filter struts2   
java.lang.NullPointerException   
     at com.opensymphony.xwork2.util.FileManager$FileRevision.needsReloading(FileManager.java:209)   
     at com.opensymphony.xwork2.util.FileManager.fileNeedsReloading(FileManager.java:60)   
     at com.opensymphony.xwork2.config.providers.XmlConfigurationProvider.needsReload(XmlConfigurationProvider.java:325)   
     at org.apache.struts2.config.StrutsXmlConfigurationProvider.needsReload(StrutsXmlConfigurationProvider.java:168)   
     at com.opensymphony.xwork2.config.ConfigurationManager.conditionalReload(ConfigurationManager.java:220)   
     at com.opensymphony.xwork2.config.ConfigurationManager.getConfiguration(ConfigurationManager.java:61)   
     at org.apache.struts2.dispatcher.Dispatcher.getContainer(Dispatcher.java:774)   
     at org.apache.struts2.dispatcher.FilterDispatcher.init(FilterDispatcher.java:191)   
     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:4363)   
     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.deployDirectory(HostConfig.java:926)   
     at org.apache.catalina.startup.HostConfig.deployDirectories(HostConfig.java:889)   
     at org.apache.catalina.startup.HostConfig.deployApps(HostConfig.java:492)   
     at org.apache.catalina.startup.HostConfig.start(HostConfig.java:1149)   
     at org.apache.catalina.startup.HostConfig.lifecycleEvent(HostConfig.java:311)   
     at org.apache.catalina.util.LifecycleSupport.fireLifecycleEvent(LifecycleSupport.java:117)   
     at org.apache.catalina.core.ContainerBase.start(ContainerBase.java:1053)   
     at org.apache.catalina.core.StandardHost.start(StandardHost.java:719)   
     at org.apache.catalina.core.ContainerBase.start(ContainerBase.java:1045)   
     at org.apache.catalina.core.StandardEngine.start(StandardEngine.java:443)   
     at org.apache.catalina.core.StandardService.start(StandardService.java:516)   
     at org.apache.catalina.core.StandardServer.start(StandardServer.java:710)   
     at org.apache.catalina.startup.Catalina.start(Catalina.java:578)   
     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:597)   
     at org.apache.catalina.startup.Bootstrap.start(Bootstrap.java:288)   
     at org.apache.catalina.startup.Bootstrap.main(Bootstrap.java:413)   
2009-2-4 22:40:54 org.apache.catalina.core.StandardContext start   
严重: Error filterStart   
2009-2-4 22:40:54 org.apache.catalina.core.StandardContext start   
严重: Context [/Struts2Demo2] startup failed due to previous errors  

    devMode模式是开发模式，开启它则默认开启了i18n.reload、configuration.xml.reload。这个错误是由于configuration.xml.reload设置为true倒置的， 原因很简单，tomcat的安装路径包含空格

哈哈.....把tomcat安装目录里的 空格删了(比如tomcat 6.0改成tomcat6.0)就行了......试试吧...很简单的...