实现功能：

  1. 后台将信息从从数据库查询出来
  2. 将查询到的信息写入excel表，将其输出供前端下载

提示

  1. 使用Apache POI 提供的HSSFWorkbook类实现对excel的操作

代码实现，只po出controller层（规范代码应将具体功能实现写在service层，controller直接接受前端参数调用方法即可），直接用浏览器访问或者postman测试即可以下载，

@RequestMapping("excelDownloads")
    public void downloadAllClassmate(HttpServletResponse response,Patent patent1) throws IOException {
        HSSFWorkbook workbook = new HSSFWorkbook();
        HSSFSheet sheet = workbook.createSheet("信息表");

        List<Patent> patentExcle = patentService.selectTest();

        String fileName = "patentExcel"  + ".xls";//设置要导出的文件的名字
        //新增数据行，并且设置单元格数据

        int rowNum = 1;

        String[] headers = { "专利ID", "批次", "案例文号", "申请号", "申请时间", "技术联系人", "申请人", "创建人", "专利名", "审核状态", "专利状态", "发明类型", "发明人", "撰写人", "备注", "状态", "创建人名称", "撰写人名称"};
        //headers表示excel表中第一行的表头

        HSSFRow row = sheet.createRow(0);
        //在excel表中添加表头

        for(int i=0;i<headers.length;i++){
            HSSFCell cell = row.createCell(i);
            HSSFRichTextString text = new HSSFRichTextString(headers[i]);
            cell.setCellValue(text);
        }

        //在表中存放查询到的数据放入对应的列
        for (Patent patent : patentExcle) {
            HSSFRow row1 = sheet.createRow(rowNum);
            row1.createCell(0).setCellValue(patent.getPatentId());
            row1.createCell(1).setCellValue(patent.getPatentBatch());
            row1.createCell(2).setCellValue(patent.getPatentCaseNum());
            row1.createCell(3).setCellValue(patent.getPatentApplyNum());
            row1.createCell(4).setCellValue(patent.getPatentApplyTime());
            row1.createCell(5).setCellValue(patent.getPatentTechnicalContact());
            row1.createCell(6).setCellValue(patent.getPatentApplyPerson());
            row1.createCell(7).setCellValue(patent.getPatentCreatePerson());
            row1.createCell(8).setCellValue(patent.getPatentName());
            row1.createCell(9).setCellValue(patent.getPatentSign());
            row1.createCell(10).setCellValue(patent.getPatentStatusId());
            row1.createCell(11).setCellValue(patent.getPatentType());
            row1.createCell(12).setCellValue(patent.getPatentInventor());
            row1.createCell(13).setCellValue(patent.getPatentWriter());
            row1.createCell(14).setCellValue(patent.getPatentRemarks());
            row1.createCell(15).setCellValue(patent.getStatusName());
            row1.createCell(16).setCellValue(patent.getCreatePersonName());
            row1.createCell(17).setCellValue(patent.getWriterName());
            rowNum++;
        }
        response.setContentType("application/x-xls;charset=utf-8");
        //response.setContentType("application/octet-stream");//设置发送到客户端的响应的内容类型，application/octet-stream（ 二进制流，不知道下载文件类型）
        response.setHeader("Content-Disposition","attachment;filename="+ URLEncoder.encode(fileName,"utf-8"));//这样写文件名中文不会乱码

        response.flushBuffer();
        ServletOutputStream out = response.getOutputStream();//输出流

        workbook.write(out); //输出文件

        out.close(); //关闭流，不主动关闭也能下载，不过会报错
    }