訪問tomcat中項目老是出現HTTP 404錯誤，錯誤如下：
嚴重: 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.ng.InitOperations.initStaticContentLoader(InitOperations.java:77)
at org.apache.struts2.dispatcher.ng.filter.StrutsPrepareAndExecuteFilter.init(StrutsPrepareAndExecuteFilter.java:49)
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:3696)
at org.apache.catalina.core.StandardContext.start(StandardContext.java:4343)
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: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: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:566)
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)
能訪問http://localhost:8080/,說明tomcat是啓動成功了，但是訪問項目的頁面就報錯，後來在網上找了找，說是tomcat的安裝路徑中多了一個空格，然後重新安裝了tomcat，果真是這個錯誤，能正常訪問頁面了，之前做開發時安裝tomcat都刪掉了空格，這次太疏忽了，切記！