About struts2 for help ah ! ! !

严重: Exception starting filter struts2
  java.lang.ClassNotFoundException: org.apache.struts2.dispatcher.ng.filter.StrutsPrepareAndExecuteFilter.class
  	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:424)
  	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.core.ContainerBase.addChildInternal(ContainerBase.java:799)
  	at org.apache.catalina.core.ContainerBase.addChild(ContainerBase.java:779)
  	at org.apache.catalina.core.StandardHost.addChild(StandardHost.java:601)
  	at org.apache.catalina.startup.HostConfig.deployDirectory(HostConfig.java:1079)
  	at org.apache.catalina.startup.HostConfig.deployDirectories(HostConfig.java:1002)
  	at org.apache.catalina.startup.HostConfig.deployApps(HostConfig.java:506)
  	at org.apache.catalina.startup.HostConfig.start(HostConfig.java:1317)
  	at org.apache.catalina.startup.HostConfig.lifecycleEvent(HostConfig.java:324)
  	at org.apache.catalina.util.LifecycleSupport.fireLifecycleEvent(LifecycleSupport.java:142)
  	at org.apache.catalina.core.ContainerBase.start(ContainerBase.java:1065)
  	at org.apache.catalina.core.StandardHost.start(StandardHost.java:840)
  	at org.apache.catalina.core.ContainerBase.start(ContainerBase.java:1057)
  	at org.apache.catalina.core.StandardEngine.start(StandardEngine.java:463)
  	at org.apache.catalina.core.StandardService.start(StandardService.java:525)
  	at org.apache.catalina.core.StandardServer.start(StandardServer.java:754)
  	at org.apache.catalina.startup.Catalina.start(Catalina.java:595)
  	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
  	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
  	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
  	at java.lang.reflect.Method.invoke(Method.java:597)
  	at org.apache.catalina.startup.Bootstrap.start(Bootstrap.java:289)
  	at org.apache.catalina.startup.Bootstrap.main(Bootstrap.java:414)
  2013-11-22 21:27:01 org.apache.catalina.core.StandardContext start
  严重: Error filterStart

This is what in the end what is wrong ah ? ? , Toss a long time. . . Help ah
------ Solution -------------------------------------- ------
look web.xml in this code there is no mistake , struts 2.x core controller then wrote :

<filter>
  		<filter-name>struts2</filter-name>
  		<filter-class>org.apache.struts2.dispatcher.ng.filter.StrutsPrepareAndExecuteFilter</filter-class>
  	</filter>

------ Solution ------------------------------------- -------
version of the problem may be
If the previous version is 2.1.3 , with org.apache.struts2.dispatcher.FilterDispatcher,
version after the configuration org.apache.struts2.dispatcher.ng.filter.StrutsPrepareAndExecuteFilter
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when I started to learn struts2 have this error , and later replaced installed version of tomcat like, also due I do not know
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less JAR package. . . . . .
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I'm not using the installed version of tomcat web wrote there is a method used to filter the third floor , the second floor is missing what package ? ? ?
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a one exclude others from another project to try
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<?xml version="1.0" encoding="UTF-8"?>
  <web-app version="2.5" 
  	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">
      <filter>
        <filter-name>struts2</filter-name>
        <filter-class>org.apache.struts2.dispatcher.ng.filter.StrutsPrepareAndExecuteFilter.class</filter-class>
      </filter>
      <filter-mapping>
        <filter-name>struts2</filter-name>
        <url-pattern>/*</url-pattern>
      </filter-mapping>
  </web-app>

The above is the configuration file there I was : struts-2.3.15.3 This configuration should be good ah
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sample document in accordance with the official investigation ...... you step by step the line drops
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pack wrong configuration error on these two
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more a core controller . class extension