Struts2 的启动问题？
这是我做Struts2 的练习时。当启动Tomcat，报的错！ 不知道为什么？  


警告: Unable to load config class org.apache.struts2.interceptor.debugging.DebuggingInterceptor at interceptor - jar:file:/C:/Program%20Files/Apache%20Software%20Foundation/Tomcat%205.5/webapps/Struts2HelloWord/WEB-INF/lib/struts2-core-2.0.12.jar!/struts-default.xml:99:115 probably due to a missing jar, which might be fine if you never plan to use the debugging interceptor
2008-12-19 20:23:57 com.opensymphony.xwork2.config.providers.InterceptorBuilder constructInterceptorReference
严重: Actual exception
Caught Exception while registering Interceptor class org.apache.struts2.interceptor.debugging.DebuggingInterceptor - interceptor - jar:file:/C:/Program%20Files/Apache%20Software%20Foundation/Tomcat%205.5/webapps/Struts2HelloWord/WEB-INF/lib/struts2-core-2.0.12.jar!/struts-default.xml:99:115
at org.apache.struts2.impl.StrutsObjectFactory.buildInterceptor(StrutsObjectFactory.java:78)
at com.opensymphony.xwork2.config.providers.InterceptorBuilder.constructInterceptorReference(InterceptorBuilder.java:57)
at com.opensymphony.xwork2.config.providers.XmlConfigurationProvider.lookupInterceptorReference(XmlConfigurationProvider.java:905)
at com.opensymphony.xwork2.config.providers.XmlConfigurationProvider.loadInterceptorStack(XmlConfigurationProvider.java:743)
at com.opensymphony.xwork2.config.providers.XmlConfigurationProvider.loadInterceptorStacks(XmlConfigurationProvider.java:756)
at com.opensymphony.xwork2.config.providers.XmlConfigurationProvider.loadInterceptors(XmlConfigurationProvider.java:777)
at com.opensymphony.xwork2.config.providers.XmlConfigurationProvider.addPackage(XmlConfigurationProvider.java:410)
at com.opensymphony.xwork2.config.providers.XmlConfigurationProvider.loadPackages(XmlConfigurationProvider.java:239)
at org.apache.struts2.config.StrutsXmlConfigurationProvider.loadPackages(StrutsXmlConfigurationProvider.java:111)
at com.opensymphony.xwork2.config.impl.DefaultConfiguration.reload(DefaultConfiguration.java:152)
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:203)
at org.apache.catalina.core.ApplicationFilterConfig.getFilter(ApplicationFilterConfig.java:223)
at org.apache.catalina.core.ApplicationFilterConfig.setFilterDef(ApplicationFilterConfig.java:304)
at org.apache.catalina.core.ApplicationFilterConfig.<init>(ApplicationFilterConfig.java:77)
at org.apache.catalina.core.StandardContext.filterStart(StandardContext.java:3600)
at org.apache.catalina.core.StandardContext.start(StandardContext.java:4189)
at org.apache.catalina.core.ContainerBase.addChildInternal(ContainerBase.java:759)
at org.apache.catalina.core.ContainerBase.addChild(ContainerBase.java:739)
at org.apache.catalina.core.StandardHost.addChild(StandardHost.java:524)
at org.apache.catalina.startup.HostConfig.deployDirectory(HostConfig.java:904)
at org.apache.catalina.startup.HostConfig.deployDirectories(HostConfig.java:867)
at org.apache.catalina.startup.HostConfig.deployApps(HostConfig.java:474)
at org.apache.catalina.startup.HostConfig.start(HostConfig.java:1112)
at org.apache.catalina.startup.HostConfig.lifecycleEvent(HostConfig.java:310)
at org.apache.catalina.util.LifecycleSupport.fireLifecycleEvent(LifecycleSupport.java:119)
at org.apache.catalina.core.ContainerBase.start(ContainerBase.java:1021)
at org.apache.catalina.core.StandardHost.start(StandardHost.java:718)
at org.apache.catalina.core.ContainerBase