错误

The value of the 'Access-Control-Allow-Origin' header in the response must not be the wildcard '*' when the request's credentials mode is 'include'.

可能原因一

没有设置全局跨域，检查代码，加上全局跨域

可能原因二

public static void downloadFile(HttpServletResponse resp, String name, String downloadPath) throws IOException {
        String filePath = null;
        try {

            filePath= URLDecoder.decode(downloadPath,"UTF-8");
        } catch (UnsupportedEncodingException e) {
            e.printStackTrace();
        }
        //String realPath = "D:" + File.separator + "apache-tomcat-8.5.15" + File.separator + "files";
        String realPath=filePath;//项目路径下你存放文件的地方
        String path = realPath + File.separator + name;//加上文件名称
        File file = new File(path);
        if(!file.exists()){
            throw new IOException("文件不存在");
        }
        name = new String(name.getBytes("GBK"), "ISO-8859-1");
        resp.reset();
/*
        * 跨域配置
        * */
        resp.addHeader("Access-Control-Allow-Origin", "*");
        resp.addHeader("Access-Control-Allow-Methods", "GET, POST, PUT, DELETE");
        resp.addHeader("Access-Control-Allow-Headers", "Content-Type");

        resp.setContentType("application/octet-stream");
        resp.setCharacterEncoding("utf-8");
        resp.setContentLength((int) file.length());
        resp.setHeader("Content-Disposition", "attachment;filename=" + name);
        byte[] buff = new byte[1024];
        BufferedInputStream bis = null;
        OutputStream os = null;
        try {
            os = resp.getOutputStream();
            bis = new BufferedInputStream(new FileInputStream(file));
            int i = 0;
            while ((i = bis.read(buff)) != -1) {
                os.write(buff, 0, i);
                os.flush();
            }
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            try {
                bis.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }

关键代码

        resp.reset();
	/*
        * 跨域配置
        * */
        resp.addHeader("Access-Control-Allow-Origin", "*");
        resp.addHeader("Access-Control-Allow-Methods", "GET, POST, PUT, DELETE");
        resp.addHeader("Access-Control-Allow-Headers", "Content-Type");

启发

response.reset()调用以后，全局设置的跨域header就丢了，因此重新设置的。