出现The server encountered an internal error () that prevented

出现The server encountered an internal error () that prevented it from fulfilling this request
type Exception report
message
description The server encountered an internal error () that prevented it from fulfilling this request.
exception
java.lang.ClassCastException:com.web.servlet.ChangeUserPassword
org.apache.catalina.servlets.InvokerServlet.serveRequest(InvokerServlet.java:370)
org.apache.catalina.servlets.InvokerServlet.doPost(InvokerServlet.java:170)
javax.servlet.http.HttpServlet.service(HttpServlet.java:710)
javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
note The full stack trace of the root cause is available in the Apache Tomcat/5.5.26 logs.
出现这种问题应该如何解决