關於Struts2+Spring集成時報瞭如下錯誤，麻煩各位高手幫忙看下是什麼原因導致，多謝！！！！！！

log4j:WARN No appenders could be found for logger (com.opensymphony.xwork2.config.providers.XmlConfigurationProvider).
log4j:WARN Please initialize the log4j system properly.
2010-4-7 13:55:40 org.apache.catalina.core.StandardContext filterStart
嚴重: Exception starting filter struts2
java.lang.NoClassDefFoundError: Lcom/opensymphony/xwork2/util/logging/Logger;
 at java.lang.Class.getDeclaredFields0(Native Method)
 at java.lang.Class.privateGetDeclaredFields(Unknown Source)
 at java.lang.Class.getDeclaredFields(Unknown Source)
 at com.opensymphony.xwork2.inject.ContainerImpl.addInjectors(ContainerImpl.java:102)
 at com.opensymphony.xwork2.inject.ContainerImpl$1.create(ContainerImpl.java:84)
 at com.opensymphony.xwork2.inject.ContainerImpl$1.create(ContainerImpl.java:82)
 at com.opensymphony.xwork2.inject.util.ReferenceCache$CallableCreate.call(ReferenceCache.java:155)
 at java.util.concurrent.FutureTask$Sync.innerRun(Unknown Source)
 at java.util.concurrent.FutureTask.run(Unknown Source)
 at com.opensymphony.xwork2.inject.util.ReferenceCache.internalCreate(ReferenceCache.java:81)
 at com.opensymphony.xwork2.inject.util.ReferenceCache.get(ReferenceCache.java:121)
 at com.opensymphony.xwork2.inject.ContainerImpl$ConstructorInjector.<init>(ContainerImpl.java:329)
 at com.opensymphony.xwork2.inject.ContainerImpl$5.create(ContainerImpl.java:299)
 at com.opensymphony.xwork2.inject.ContainerImpl$5.create(ContainerImpl.java:298)
 at com.opensymphony.xwork2.inject.util.ReferenceCache$CallableCreate.call(ReferenceCache.java:155)
 at java.util.concurrent.FutureTask$Sync.innerRun(Unknown Source)
 at java.util.concurrent.FutureTask.run(Unknown Source)
 at com.opensymphony.xwork2.inject.util.ReferenceCache.internalCreate(ReferenceCache.java:81)
 at com.opensymphony.xwork2.inject.util.ReferenceCache.get(ReferenceCache.java:121)
 at com.opensymphony.xwork2.inject.ContainerImpl.getConstructor(ContainerImpl.java:562)
 at com.opensymphony.xwork2.inject.ContainerImpl.inject(ContainerImpl.java:460)
 at com.opensymphony.xwork2.inject.ContainerImpl$7.call(ContainerImpl.java:501)
 at com.opensymphony.xwork2.inject.ContainerImpl.callInContext(ContainerImpl.java:549)
 at com.opensymphony.xwork2.inject.ContainerImpl.inject(ContainerImpl.java:499)
 at com.opensymphony.xwork2.config.impl.LocatableFactory.create(LocatableFactory.java:32)
 at com.opensymphony.xwork2.inject.ContainerBuilder$4.create(ContainerBuilder.java:134)
 at com.opensymphony.xwork2.inject.Scope$2$1.create(Scope.java:49)
 at com.opensymphony.xwork2.inject.ContainerImpl$ParameterInjector.inject(ContainerImpl.java:431)
 at com.opensymphony.xwork2.inject.ContainerImpl.getParameters(ContainerImpl.java:446)
 at com.opensymphony.xwork2.inject.ContainerImpl.access$000(ContainerImpl.java:48)
 at com.opensymphony.xwork2.inject.ContainerImpl$MethodInjector.inject(ContainerImpl.java:288)
 at com.opensymphony.xwork2.inject.ContainerImpl$2.call(ContainerImpl.java:117)
 at com.opensymphony.xwork2.inject.ContainerImpl$2.call(ContainerImpl.java:115)
 at com.opensymphony.xwork2.inject.ContainerImpl.callInContext(ContainerImpl.java:542)
 at com.opensymphony.xwork2.inject.ContainerImpl.injectStatics(ContainerImpl.java:114)
 at com.opensymphony.xwork2.inject.ContainerBuilder.create(ContainerBuilder.java:494)
 at com.opensymphony.xwork2.config.impl.DefaultConfiguration.reload(DefaultConfiguration.java:145)
 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:205)
 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:3800)
 at org.apache.catalina.core.StandardContext.start(StandardContext.java:4450)
 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:526)
 at org.apache.catalina.startup.HostConfig.deployDirectory(HostConfig.java:987)
 at org.apache.catalina.startup.HostConfig.deployDirectories(HostConfig.java:909)
 at org.apache.catalina.startup.HostConfig.deployApps(HostConfig.java:495)
 at org.apache.catalina.startup.HostConfig.start(HostConfig.java:1206)
 at org.apache.catalina.startup.HostConfig.lifecycleEvent(HostConfig.java:314)
 at org.apache.catalina.util.LifecycleSupport.fireLifecycleEvent(LifecycleSupport.java:119)
 at org.apache.catalina.core.ContainerBase.start(ContainerBase.java:1053)
 at org.apache.catalina.core.StandardHost.start(StandardHost.java:722)
 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:583)
 at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
 at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
 at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
 at java.lang.reflect.Method.invoke(Unknown Source)
 at org.apache.catalina.startup.Bootstrap.start(Bootstrap.java:288)
 at org.apache.catalina.startup.Bootstrap.main(Bootstrap.java:413)
2010-4-7 13:55:40 org.apache.catalina.core.StandardContext start