Exception starting filter struts2 java.lang.ClassNotFoundException: org.apache.struts2.dispatcher.ng.filter.StrutsPrepareAndExecuteFilter

[sandeep kotha]

In-spite of having *struts2-core-2.1.8.1.jar *under
/WebContent/WEB-INF/lib/struts-2.1.8.1/ . im getting the below error .

Exception starting filter struts2
*java.lang.ClassNotFoundException*:
org.apache.struts2.dispatcher.ng.filter.StrutsPrepareAndExecuteFilter

*
my web.xml*

<?xml version="1.0" encoding="UTF-8"?>
<web-app id="WebApp_ID" version="2.4" xmlns="http://java.sun.com/xml/ns/j2ee
" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"; xsi:schemaLocation="
http://java.sun.com/xml/ns/j2ee
http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd";>
<display-name>my_project</display-name>
  <welcome-file-list>
    <welcome-file>initial.jsp</welcome-file>
  </welcome-file-list>


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

     <filter-mapping>
        <filter-name>struts2</filter-name>
        <url-pattern>/*</url-pattern>
    </filter-mapping>

</web-app>

Any help is much appreciated.