解决EasyPoi导出excel文件后打开提示格式错误的问题

excel文件下载成功后打开文件遇到错误

 之前的下载代码：

private static void downLoadExcel(String fileName, HttpServletResponse response, Workbook workbook) {
        try {
            response.setCharacterEncoding("UTF-8");
            response.setHeader("content-Type", "application/vnd.ms-excel");
            response.setHeader("Content-Disposition", "attachment;filename=" + URLEncoder.encode(fileName, "UTF-8"));
            workbook.write(response.getOutputStream());
        } catch (IOException e) {
            try {
                throw new Exception(e.getMessage());
            } catch (Exception e1) {
                // TODO Auto-generated catch block
                e1.printStackTrace();
            }
        }
    }

改正后的下载代码：

private static void downLoadExcel(String fileName, HttpServletResponse response, Workbook workbook) {
        try (OutputStream out = response.getOutputStream())
        {
            response.setCharacterEncoding("UTF-8");
            response.setHeader("content-Type", "application/vnd.ms-excel");
            response.setHeader("Content-Disposition", "attachment;filename=" + URLEncoder.encode(fileName, "UTF-8"));
            ByteArrayOutputStream baos = new ByteArrayOutputStream();
            workbook.write(baos);
            response.setHeader("Content-Length", String.valueOf(baos.size()));
            out.write( baos.toByteArray() );
        } catch (IOException e) {
            try {
                throw new Exception(e.getMessage());
            } catch (Exception e1) {
                // TODO Auto-generated catch block
                e1.printStackTrace();
            }
        }
    }

原因：Debug发现请求头的Content-Length，在未设置的情况在是-1，下载时需重新定义Content-Length