java.lang.ClassNotFoundException: org.apache.struts2.dispatcher.ng.filter.Struts
严重: Exception starting filter struts2
java.lang.ClassNotFoundException: org.apache.struts2.dispatcher.ng.filter.StrutsPrepareAndExecuteFilter
at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1666)
at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1511)
at org.apache.catalina.core.DefaultInstanceManager.loadClass(DefaultInstanceManager.java:406)
at org.apache.catalina.core.DefaultInstanceManager.loadClassMaybePrivileged(DefaultInstanceManager.java:388)
at org.apache.catalina.core.DefaultInstanceManager.newInstance(DefaultInstanceManager.java:117)
at org.apache.catalina.core.ApplicationFilterConfig.getFilter(ApplicationFilterConfig.java:248)
at org.apache.catalina.core.ApplicationFilterConfig.setFilterDef(ApplicationFilterConfig.java:368)
at org.apache.catalina.core.ApplicationFilterConfig.<init>(ApplicationFilterConfig.java:98)
at org.apache.catalina.core.StandardContext.filterStart(StandardContext.java:4193)
at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:4801)
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:139)
at org.apache.catalina.core.ContainerBase.startInternal(ContainerBase.java:988)
at org.apache.catalina.core.StandardHost.startInternal(StandardHost.java:771)
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:139)
at org.apache.catalina.core.ContainerBase.startInternal(ContainerBase.java:988)
at org.apache.catalina.core.StandardEngine.startInternal(StandardEngine.java:275)
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:139)
at org.apache.catalina.core.StandardService.startInternal(StandardService.java:427)
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:139)
at org.apache.catalina.core.StandardServer.startInternal(StandardServer.java:649)
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:139)
at org.apache.catalina.startup.Catalina.start(Catalina.java:585)
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:415)
我用的是strut2.3.3,导入的包有：
commons-fileupload-1.2.2.jar
commons-io-2.0.1.jar
commons-lang-2.5.jar
freemarker-2.3.16.jar
ognl-3.0.1.jar
struts2-core-2.2.3.jar
xwork-core-2.2.3.jar
javassist-3.11.0.GA.jar

struts.xml放在src目录下，代码如下：

<?xml version="1.0" encoding="UTF-8" ?>

<!DOCTYPE struts PUBLIC

    "-//Apache Software Foundation//DTD Struts Configuration 2.0//EN"

    "http://struts.apache.org/dtds/struts-2.0.dtd">



<struts>

    <constant name="struts.devMode" value="true" />

    <package name="default"  namespace="/"&