JAVA文件下载，页面显示另存为效果

@RequestMapping("download")
    public void download(HttpServletRequest request,HttpServletResponse response){
        BufferedInputStream dis = null;
        BufferedOutputStream fos = null;

        String urlString = request.getParameter("urlString");
        String fileName = urlString.substring(urlString.lastIndexOf(‘/‘) + 1);

        try {

            URL url = new URL(urlString);
            //response.setContentType("application/x-msdownload;");
            response.setContentType("application/octet-stream");
            response.setHeader("Content-disposition", "attachment; filename=" + new String(fileName.getBytes("utf-8"), "ISO8859-1"));
            response.setHeader("Content-Length", String.valueOf(url.openConnection().getContentLength()));

            dis = new BufferedInputStream(url.openStream());
            fos = new BufferedOutputStream(response.getOutputStream());

            byte[] buff = new byte[2048];
            int bytesRead;
            while (-1 != (bytesRead = dis.read(buff, 0, buff.length))) {
                fos.write(buff, 0, bytesRead);
            }

        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            if (dis != null)
                try{
                    dis.close();
                }catch (Exception e){
                    e.printStackTrace();
                }
            if (fos != null)
                try{
                    fos.close();
                }catch (Exception e){
                    e.printStackTrace();
                }

        }
    }

<input type="button" onclick="downloadImage()" value="下载">



<script>
   function downloadImage(){
       var urlString = "http://pic32.nipic.com/20130829/12906030_124355855000_2.png";
       //跳转到后端控制器
       location.href="${ctx}/guest/download.do?urlString="+urlString;
   }
</script>