js + java文件下载

js请求：

// 下载图片
    function oDownLoad(url, filename) {
        var url = '${pageContext.request.contextPath}/file/downFile.do?url=' + url + '&filename=' + encodeURI(filename);
        window.location.href = url;
    }

java后端：

@RequestMapping(value = "/downFile.do", method = RequestMethod.GET)
    public void downPicture(HttpServletRequest request, HttpServletResponse response) throws Exception {
        InputStream in = null;
        String url = request.getParameter("url");
        String filename = request.getParameter("filename");
        //filename = java.net.URLDecoder.decode(filename, "UTF-8");
        filename = new String(filename.getBytes("GB2312"),"iso-8859-1");
        try {
            URL httpUrl = new URL(url);
            HttpURLConnection conn = (HttpURLConnection)httpUrl.openConnection();
            conn.setRequestMethod("GET");
            conn.setConnectTimeout(100000);// 连接超时单位毫秒 //
            conn.setReadTimeout(200000);// 读取超时 单位毫秒
            conn.setDoInput(true);
            conn.setDoOutput(true);
            conn.setUseCaches(false);
            conn.connect();

            in = conn.getInputStream();

            byte[] bs = new byte[1024];
            int len = 0;
            response.reset();

            response.setHeader("Pragma", "no-cache");
            response.setHeader("Cache-Control", "no-cache");

            response.setContentType("application/octet-stream");
            response.setHeader("Content-disposition", "attachment;filename=" + filename);

            ServletOutputStream out = response.getOutputStream();
            while ((len = in.read(bs))!= -1){
                out.write(bs,0,len);
            }

            out.flush();
            //关流
            out.close();
        }catch (Exception e){
            throw new RuntimeException(url + "下载失败");
        }finally {
            try{
                in.close();
            }catch (Exception e){
            }
        }
        
    }