struts1与struts2的防止表单重复提交

public ActionForward entry(ActionMapping mapping, ActionForm form,  
           HttpServletRequestrequest, HttpServletResponse response)  
           throws Exception {  
       saveToken(request);  
       return mapping.findForward("showAll");  
    }  
    public ActionForward  update(ActionMapping mapping, ActionForm form,  
           HttpServletRequestrequest, HttpServletResponse response)  
           throws Exception {  
       if (isTokenValid(request, true)) {  
           UserForm actionForm=(UserForm)form;  
           .................
           return mapping.findForward("success");  
       }else{  
           saveToken(request);  
           return mapping.findForward("error");  
       }  
        
    }      

<%@ taglib uri="http://struts.apache.org/tags-html"  prefix="html" %>
<html:form action="User" method="post">
‘‘‘‘‘‘‘‘‘‘‘‘‘
</html:form>