mongodb中获取图片文件<标记>

    @RequestMapping(value="/downLoadFileFormMongo.do",method=RequestMethod.GET)
    @ResponseBody
    public  void downLoadFileFormMongo(HttpServletRequest request,HttpServletResponse response ) throws Exception {
        String filename=request.getParameter("fileId");
        GridFSDBFile file = fileService.retrieveFileOne("fs", filename);
        InputStream in = file.getInputStream();
        filename=(String) file.get("aliases");
        filename=filename.replace(" ", "");
        String fileName = new String(filename.getBytes("GB2312"), "ISO_8859_1");
        filename = fileName;
        //response.setCharacterEncoding("UTF-8");
        response.setContentType(file.getContentType());
        response.setHeader("Content-Disposition", "attachment;filename=" + filename);
        OutputStream out = response.getOutputStream();
        byte[] buffer = new byte[2048];
        int i = -1;
        while ((i = in.read(buffer)) != -1) {
            out.write(buffer, 0, i);
        }       
        in.close();
        out.flush();
        out.close();
    }