严重: Exception starting filter struts2-----《轻量级java EE企业应用实战》例子错误

在看《轻量级Java EE企业应用实战》，想拿来光盘中的struts2Demo运行一下，结果出现以下错误

严重: Exception starting filter struts2
java.lang.NoClassDefFoundError: org/apache/commons/lang3/StringUtils
 at com.opensymphony.xwork2.config.providers.XmlConfigurationProvider.register(XmlConfigurationProvider.java:209)
 at org.apache.struts2.config.StrutsXmlConfigurationProvider.register(StrutsXmlConfigurationProvider.java:102)
 at com.opensymphony.xwork2.config.impl.DefaultConfiguration.reloadContainer(DefaultConfiguration.java:210)
 at com.opensymphony.xwork2.config.ConfigurationManager.getConfiguration(ConfigurationManager.java:66)
 at org.apache.struts2.dispatcher.Dispatcher.init_PreloadConfiguration(Dispatcher.java:390)
 at org.apache.struts2.dispatcher.Dispatcher.init(Dispatcher.java:437)
 at org.apache.struts2.dispatcher.ng.InitOperations.initDispatcher(InitOperations.java:74)
 at org.apache.struts2.dispatcher.ng.filter.StrutsPrepareAndExecuteFilter.init(StrutsPrepareAndExecuteFilter.java:51)
 at org.apache.catalina.core.ApplicationFilterConfig.initFilter(ApplicationFilterConfig.java:277)
 at org.apache.catalina.core.ApplicationFilterConfig.getFilter(ApplicationFilterConfig.java:258)
 at org.apache.catalina.core.ApplicationFilterConfig.setFilterDef(ApplicationFilterConfig.java:382)
 at org.apache.catalina.core.ApplicationFilterConfig.<init>(ApplicationFilterConfig.java:103)
 at org.apache.catalina.core.StandardContext.filterStart(StandardContext.java:4624)
 at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5281)
 at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
 at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1525)
 at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1515)
 at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:334)
 at java.util.concurrent.FutureTask.run(FutureTask.java:166)
 at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1110)
 at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:603)
 at java.lang.Thread.run(Thread.java:722)
Caused by: java.lang.ClassNotFoundException: org.apache.commons.lang3.StringUtils
 at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1688)
 at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1533)
 ... 22 more

十月 27, 2012 10:44:34 下午 org.apache.catalina.core.StandardContext startInternal
严重: Error filterStart
十月 27, 2012 10:44:34 下午 org.apache.catalina.core.StandardContext startInternal
严重: Context [/Struts2Demo] startup failed due to previous errors
十月 27, 2012 10:44:34 下午 org.apache.coyote.AbstractProtocol start
信息: Starting ProtocolHandler ["http-bio-80"]
十月 27, 2012 10:44:34 下午 org.apache.coyote.AbstractProtocol start
信息: Starting ProtocolHandler ["ajp-bio-8009"]
十月 27, 2012 10:44:34 下午 org.apache.catalina.startup.Catalina start
信息: Server startup in 1461 ms

原以为是配置文件错误，找了一个晚上也没发现，结果搜到“严重: Exception starting filter struts2 ”是jar包的错误，在例子程序原有引入的jar包基础上再引入commons-lang3-3.1.jar，问题解决。