struts2配置常见错误——（一）不能处理错误Struts has detected an unhandled exception:

Messages:
1.cn.itcast.action.CustomerAction
2.Unable to instantiate Action, cn.itcast.action.CustomerAction, defined for 'CustomerAction' in 
    namespace '/'cn.itcast.action.CustomerAction
File:
org/apache/catalina/loader/WebappClassLoader.java
Line number:
1,718

Stacktraces
Unable to instantiate Action, cn.itcast.action.CustomerAction, 
    defined for 'CustomerAction' in namespace '/'cn.itcast.action.CustomerAction - 
    action - file:/D:/develop/apache-tomcat-7.0.52/apache-tomcat-7.0.52/webapps/crm_ssh/WEB-INF/classes/struts.xml:12:88Messages:
1.cn.itcast.action.CustomerAction
2.U