how processException() works in struts

Question

how processException works in struts. if (mapping instanceof _ActionMapping) { __ActionMapping ___Mapping = (ActionMapping)mapping; logException = !__Mapping.hasExceptionConfig(e.getClass());//it will check for the handler } // An unhandled exception has been thrown. We need to log // as much information as we can about this so that it can // be properly diagnosed. if (logException) { VersionInfo versionInfo = (VersionInfo) getServletContext().getAttribute(VersionInfo.class.getName()); UnhandledExceptionLogger.handleException(request,e, versionInfo); } return (processException(request, response, e, form, mapping)); how this line willwork and how control will move from here.

while calling hasExceptionConfig() application has decided the actionforward and all.

But it is still in dark how control gone over there.

Thanks a lot....