public String excute() {
        
        String filePath = "D:\\a.txt";// 下载的文件路径
        getfileAddress(filePath);
        try {
            InputStream iso = new FileInputStream(filePath);
            HttpServletResponse response = ServletActionContext.getResponse();
            System.out.println("downloadForm******* "+response);
//            response.reset();//清除缓存
            response.setHeader("Content-Disposition","attachment;fileName="+filePath);
            response.setContentType("text/html;charset=UTF-8");
            ServletOutputStream out = response.getOutputStream();
            byte[] content = new byte[1024];
            int length =0;
            while((length = iso.read(content))!=-1){
                out.write(content,0,length);
            }
            out.write(content);
            out.flush();
            out.close();
        } catch (Exception e) {
            e.printStackTrace();
        }

        return SUCCESS;
    }
    

上面是我实现txt文件下载的一个方法，用struts2框架，重前台页面触发下载功能，提交Action，到实现方法，但是我现在不能下，报错提示说是
: Exception initializing page context
java.lang.IllegalStateException: Cannot create a session after the response has been committed
    at org.apache.catalina.connector.Request.doGetSession(Request.java:2675)
    上面这个报错，
HttpServletResponse response = ServletActionContext.getResponse();
这句话也报错，可能是获取不到response，response过期等信息，请问有谁做过前台的，帮忙看下，怎么解决

有具体代码么