新手上路，第一个struts2实例启动老是出错
如标题，按照struts教程的实例发布一个struts2项目，但是调试了N久，还是报这个同样的错误，网上搜了好多，可是都不能解决我的问题，请各位高手帮我看看：（Myeclipse 6.0 + struts 2.1.6 + tomcat 6.0）

错误信息：
  2011-8-30 11:56:56 org.apache.catalina.core.AprLifecycleListener init
信息: The APR based Apache Tomcat Native library which allows optimal performance in production environments was not found on the java.library.path: C:\jdk1.6.0_10\bin;D:\apache-tomcat-6.0.29\bin
2011-8-30 11:56:56 org.apache.coyote.http11.Http11Protocol init
信息: Initializing Coyote HTTP/1.1 on http-8080
2011-8-30 11:56:56 org.apache.catalina.startup.Catalina load
信息: Initialization processed in 270 ms
2011-8-30 11:56:56 org.apache.catalina.core.StandardService start
信息: Starting service Catalina
2011-8-30 11:56:56 org.apache.catalina.core.StandardEngine start
信息: Starting Servlet Engine: Apache Tomcat/6.0.29
2011-8-30 11:56:56 org.apache.catalina.startup.HostConfig deployDescriptor
信息: Deploying configuration descriptor host-manager.xml
2011-8-30 11:56:56 org.apache.catalina.startup.HostConfig deployDescriptor
信息: Deploying configuration descriptor manager.xml
2011-8-30 11:56:56 org.apache.catalina.startup.HostConfig deployWAR
信息: Deploying web application archive struts2-blank-2.1.6.war
2011-8-30 11:56:56 com.opensymphony.xwork2.util.logging.commons.CommonsLogger info
信息: Parsing configuration file [struts-default.xml]
2011-8-30 11:56:57 com.opensymphony.xwork2.util.logging.commons.CommonsLogger info
信息: Unable to locate configuration files of the name struts-plugin.xml, skipping
2011-8-30 11:56:57 com.opensymphony.xwork2.util.logging.commons.CommonsLogger info
信息: Parsing configuration file [struts-plugin.xml]
2011-8-30 11:56:57 com.opensymphony.xwork2.util.logging.commons.CommonsLogger info
信息: Parsing configuration file [struts.xml]
2011-8-30 11:56:57 org.apache.catalina.startup.HostConfig deployDirectory
信息: Deploying web application directory demo
2011-8-30 11:56:57 org.apache.catalina.startup.HostConfig deployDirectory
信息: Deploying web application directory docs
2011-8-30 11:56:57 org.apache.catalina.startup.HostConfig deployDirectory
信息: Deploying web application directory examples
2011-8-30 11:56:57 org.apache.catalina.core.ApplicationContext log
信息: ContextListener: contextInitialized()
2011-8-30 11:56:57 org.apache.catalina.core.ApplicationContext log
信息: SessionListener: contextInitialized()
2011-8-30 11:56:57 org.apache.catalina.startup.HostConfig deployDirectory
信息: Deploying web application directory ROOT
2011-8-30 11:56:57 org.apache.catalina.startup.HostConfig deployDirectory
信息: Deploying web application directory strut2
2011-8-30 11:56:57 com.opensymphony.xwork2.util.logging.commons.CommonsLogger info
信息: Parsing configuration file [struts-default.xml]
2011-8-30 11:56:58 com.opensymphony.xwork2.util.logging.commons.CommonsLogger info
信息: Parsing configuration file [struts-plugin.xml]
2011-8-30 11:56:58 com.opensymphony.xwork2.util.logging.commons.CommonsLogger info
信息: Parsing configuration file [struts.xml]
2011-8-30 11:56:58 org.apache.catalina.core.StandardContext filterStart
严重: Exception starting filter struts2
java.lang.NoClassDefFoundError: Lorg/codehaus/plexus/PlexusContainer;
at java.lang.Class.getDeclaredFields0(Native Method)
at java.lang.Class.privateGetDeclaredFields(Class.java:2291)
at java.lang.Class.getDeclaredFields(Class.java:1743)
at com.opensymphony.xwork2.inject.ContainerImpl.addInjectors(ContainerImpl.java:89)
at com.opensymphony.xwork2.inject.ContainerImpl$1.create(ContainerImpl.java:71)
at com.opensymphony.xwork2.inject.ContainerImpl$1.create(ContainerImpl.java:69)
at com.opensymphony.xwork2.inject.util.ReferenceCache$CallableCreate.call(ReferenceCache.java:150)
at