Samuel Learning

public ActionForward execute(

        ActionMapping mapping,

        ActionForm form,

        HttpServletRequest request,

        HttpServletResponse response)

        throws Exception {

        // Generate a unique token that will be

        // check when the form is submitted

        saveToken(request);

        // Forward to the form

        return mapping.findForward("success");

}

public ActionForward execute(

        ActionMapping mapping,

        ActionForm form,

        HttpServletRequest request,

        HttpServletResponse response)

        throws Exception {

        // If user pressed 'Cancel' button,

        // return to home page

        if (isCancelled(request)) {

            return mapping.findForward("home");

        }

        ActionErrors errors = new ActionErrors();

        // Prevent unintentional duplication submissions by checking

        // that we have not received this token previously

        if (!isTokenValid(request)) {

            errors.add(

                ActionMessages.GLOBAL_MESSAGE,

                new ActionMessage("errors.token"));

        }

        resetToken(request);

        // Report any errors we have discovered back to the original form

        if (!errors.isEmpty()) {

            saveErrors(request, errors);

            saveToken(request);

            //這里返回到輸入頁面，完全避免重復提交最好跳轉到其他警告頁面

            return (mapping.getInputForward());

        }

        // Forward to result page

        return mapping.findForward("success");

}