初次搭建struts2环境，求解
2013-10-13 14:29:06 org.apache.struts2.dispatcher.Dispatcher error
严重: Dispatcher initialization failed
java.lang.RuntimeException: java.lang.reflect.InvocationTargetException

Caused by: java.lang.reflect.InvocationTargetException

Caused by: java.lang.ClassNotFoundException: javassist.ClassPool

2013-10-13 14:29:06 org.apache.catalina.core.StandardContext filterStart
严重: Exception starting filter struts2
java.lang.reflect.InvocationTargetException - Class: com.opensymphony.xwork2.inject.ContainerImpl$MethodInjector
File: ContainerImpl.java
Method: inject

Caused by: java.lang.RuntimeException: java.lang.reflect.InvocationTargetException

Caused by: java.lang.reflect.InvocationTargetException

Caused by: java.lang.IllegalArgumentException: Javassist library is missing in classpath! Please add missed dependency!

Caused by: java.lang.ClassNotFoundException: javassist.ClassPool

2013-10-13 14:29:06 org.apache.catalina.core.StandardContext start
严重: Error filterStart
2013-10-13 14:29:06 org.apache.catalina.core.StandardContext start
严重: Context [/struts2] startup failed due to previous errors

-------------------------------------------------------------------------

strust.xml
<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE struts PUBLIC
"-//Apache Software Foundation//DTD Struts Configuration 2.3//EN"
"http://struts.apache.org/dtds/struts-2.3.dtd">

<struts>

</struts>

------------------------------------------------------------------------------------

web.xml

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

<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>

<welcome-file-list>
<welcome-file>index.jsp</welcome-file>
</welcome-file-list>
</web-app>