TilesUtilImpl 错误给帮下忙，谢谢！
java.lang.ClassCastException:   org.apache.struts.tiles.TilesUtilImpl
org.apache.struts.tiles.TilesRequestProcessor.initDefinitionsMapping(TilesRequestProcessor.java:126)
org.apache.struts.tiles.TilesRequestProcessor.init(TilesRequestProcessor.java:116)
org.apache.struts.action.ActionServlet.getRequestProcessor(ActionServlet.java:872)
org.apache.struts.action.ActionServlet.process(ActionServlet.java:1482)
org.apache.struts.action.ActionServlet.doPost(ActionServlet.java:525)
javax.servlet.http.HttpServlet.service(HttpServlet.java:709)
javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
这是什么错误，大家给帮下忙？

------解决方案--------------------
ClassCastException,应该是类转换出错。你可能在class中遇到强行转换类的时候出错，譬如（String)null