/**
     * 支持在线打开和下载
   *
     * @param filePath
     * @param response
     * @param isOnLine
     * @param fname
     * @throws IOException
     */
    public void download(String filePath, HttpServletResponse response,
            boolean isOnLine, String fname) throws IOException {
        System.out.println("filePath:" + filePath);
        File f = new File(filePath);
        if (!f.exists()) {
            response.sendError(404, "File not found!");
            return;
        }
        BufferedInputStream br = new BufferedInputStream(new FileInputStream(f));
        byte[] bs = new byte[1024];
        int len = 0;
        response.reset(); // 非常重要
        if (isOnLine) { // 在线打开方式
            URL u = new URL("https://cdn047.yun-img.com/static/upload/bigam/download/20210324153848_66420.pdf" + filePath);
            String contentType = u.openConnection().getContentType();
            response.setContentType(contentType);
            response.setHeader("Content-Disposition", "inline;filename="
                    + fname);
            // 文件名应该编码成utf-8，注意：使用时，我们可忽略这句
        } else {
            // 纯下载方式
            response.setContentType("application/x-msdownload");
            response.setHeader("Content-Disposition", "attachment;filename="
                    + fname);
        }
        OutputStream out = response.getOutputStream();
        while ((len = br.read(bs)) > 0) {
            out.write(bs, 0, len);
        }
        out.flush();
        out.close();
        br.close();