struts2中的web配置 初学者 求大神指教

<?xml version="1.0" encoding="GBK"?><web-app xmlns="http://java.sun.com/xml/ns/javaee"    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"    xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"    version="2.5">       <filter>        <filter-name>struts2</filter-name>        <filter-class>org.apache.Struts2.dispatcher.FilterDispatcher</filter-class>    </filter>       <filter-mapping>        <filter-name>struts2</filter-name>        <url-pattern>/*</url-pattern>    </filter-mapping>   </web-app>

严重: Exception starting filter struts2java.lang.ClassNotFoundException: org.apache.Struts2.dispatcher.FilterDispatcher    at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1680)    at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1526)    at org.apache.catalina.core.ApplicationFilterConfig.getFilter(ApplicationFilterConfig.java:269)    at org.apache.catalina.core.ApplicationFilterConfig.setFilterDef(ApplicationFilterConfig.java:422)    at org.apache.catalina.core.ApplicationFilterConfig.<init>(ApplicationFilterConfig.java:115)    at org.apache.catalina.core.StandardContext.filterStart(StandardContext.java:4072)    at org.apache.catalina.core.StandardContext.start(StandardContext.java:4726)    at org.apache.catalina.startup.HostConfig.checkResources(HostConfig.java:1284)    at org.apache.catalina.startup.HostConfig.check(HostConfig.java:1382)    at org.apache.catalina.startup.HostConfig.lifecycleEvent(HostConfig.java:306)    at org.apache.catalina.util.LifecycleSupport.fireLifecycleEvent(LifecycleSupport.java:142)    at org.apache.catalina.core.ContainerBase.backgroundProcess(ContainerBase.java:1389)    at org.apache.catalina.core.ContainerBase$ContainerBackgroundProcessor.processChildren(ContainerBase.java:1653)    at org.apache.catalina.core.ContainerBase$ContainerBackgroundProcessor.processChildren(ContainerBase.java:1662)    at org.apache.catalina.core.ContainerBase$ContainerBackgroundProcessor.run(ContainerBase.java:1642)    at java.lang.Thread.run(Unknown Source)2012-2-13 10:33:48 org.apache.catalina.core.StandardContext start严重: Error filterStart2012-2-13 10:33:48 org.apache.catalina.core.StandardContext start严重: Context [/struts2.2] startup failed due to previous errors