public ActionForward execute(ActionMapping mapping,
    ActionForm form,
    HttpServletRequest request,
    HttpServletResponse response) throws Exception 
{
            
        // Identify the request parameter containing the method name
        // If none defined, use "def"
        String parameter = mapping.getParameter();
        if (parameter == null) {
            parameter = "def";
        }
        // Identify the method name to be dispatched to
        String name = request.getParameter(parameter);
        if (name == null) {
            log.error("Can't get parameter '" + parameter + "'.");        
            return mapping.findForward("error");
        }
        // Try to dispatch to requested definition
        try {
            // Read definition from factory, but we can create it here.
            ComponentDefinition definition =
                TilesUtil.getDefinition(
                    name,
                    request,
                    getServlet().getServletContext());
            if (log.isDebugEnabled()) {
                log.debug("Get Definition " + definition);
            }
            DefinitionsUtil.setActionDefinition(request, definition);
        } catch (FactoryNotFoundException e) {
            log.error("Can't get definition factory.", e);
            return mapping.findForward("error");
        } catch (NoSuchDefinitionException e) {
            log.error("Can't get definition '" + name + "'.", e);
            return mapping.findForward("error");
        } catch (DefinitionsFactoryException e) {
            log.error("General Factory error '" + e.getMessage() + "'.", e);
            return mapping.findForward("error");
        } catch (Exception e) {
            log.error("General error '" + e.getMessage() + "'.", e);
            return mapping.findForward("error");
        }
        return mapping.findForward("success");
}

Process the specified HTTP request, and create the corresponding HTTP response (or forward to another web component that will create it), with provision for handling exceptions thrown by the business logic.

 protected  void printError(HttpServletResponse response,
    String msg) throws IOException 
{
        response.setContentType("text/plain");
        PrintWriter writer = response.getWriter();
        writer.println(msg);
        writer.flush();
        writer.close();
}