Java下载文件

public void downloadFile(){
        String filePath = request.getParameter("filepath");
        try {
            filePath = new String(filePath.getBytes("ISO-8859-1"),"UTF-8");
            String rootPath = request.getSession().getServletContext().getRealPath("/");
            File file = new File(rootPath+filePath);
            String downFileName = file.getName();
            
            InputStream fis = new BufferedInputStream(new FileInputStream(file));
            byte[] buffer = new byte[fis.available()];
            fis.read(buffer);
            fis.close();
            // 清空response
            response.reset();
            // 设置response的Header
            response.addHeader("Content-Disposition", "attachment;filename=" + new String(downFileName.getBytes()));
            response.addHeader("Content-Length", "" + file.length());
            OutputStream toClient = new BufferedOutputStream(response.getOutputStream());
            response.setContentType("application/octet-stream");
            toClient.write(buffer);
            toClient.close();
        } catch (Exception e) {
            log.errorLog("文件下载失败", e);
        }
    }