获取上当前访问路径问题 （struts2）

HttpServletRequest request =  ServletActionContext.getRequest();
String path_str = request.getServletPath();
String param_str=request.getQueryString();
if(request.getQueryString() != null){
path_str+= "?"+ param_str;
}
//URLEncoder.encode(param_str,"UTF-8")
ActionContext.getContext().put("last_url",URLEncoder.encode(path_str,"UTF-8"));

last_url = java.net.URLDecoder.decode(last_url, "UTF-8");