web新手求助！！这是什么错误！！
exception 

javax.servlet.ServletException: Filter execution threw an exception


root cause 

java.lang.NoClassDefFoundError: Could not initialize class com.yxq.action.IndexAction
sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:57)
sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
java.lang.reflect.Constructor.newInstance(Constructor.java:525)
java.lang.Class.newInstance0(Class.java:372)
java.lang.Class.newInstance(Class.java:325)
com.opensymphony.xwork2.ObjectFactory.buildBean(ObjectFactory.java:123)
com.opensymphony.xwork2.ObjectFactory.buildBean(ObjectFactory.java:154)
com.opensymphony.xwork2.ObjectFactory.buildBean(ObjectFactory.java:143)
com.opensymphony.xwork2.ObjectFactory.buildAction(ObjectFactory.java:113)
com.opensymphony.xwork2.DefaultActionInvocation.createAction(DefaultActionInvocation.java:275)
com.opensymphony.xwork2.DefaultActionInvocation.init(DefaultActionInvocation.java:365)
com.opensymphony.xwork2.DefaultActionInvocation.access$000(DefaultActionInvocation.java:38)
com.opensymphony.xwork2.DefaultActionInvocation$1.doProfiling(DefaultActionInvocation.java:83)
com.opensymphony.xwork2.util.profiling.UtilTimerStack.profile(UtilTimerStack.java:455)
com.opensymphony.xwork2.DefaultActionInvocation.<init>(DefaultActionInvocation.java:74)
com.opensymphony.xwork2.DefaultActionProxy.prepare(DefaultActionProxy.java:189)
org.apache.struts2.impl.StrutsActionProxyFactory.createActionProxy(StrutsActionProxyFactory.java:41)
org.apache.struts2.dispatcher.Dispatcher.serviceAction(Dispatcher.java:494)
org.apache.struts2.dispatcher.FilterDispatcher.doFilter(FilterDispatcher.java:419)


note The full stack trace of the root cause is available in the Apache Tomcat/7.0.6 logs.


------解决方案--------------------
没找到IndexAction，或者你配置有问题
------解决方案--------------------
应该是WEB.XML文件配置问题
------解决方案--------------------
IndexAction
这个action你有没有配置？ 
或者配置了 名字对应错误！
------解决方案--------------------
看一下 IndexAction 的配置吧