页面点击下载查询数据库数据写入到SXSSFWorkbook（工作簿）中的`Sheet sheet = xswb.createSheet();`（工作表）

1. 前端发送请求到servlet，把需要的参数传递到后台【我这里把response对象也封装到了(EiInfo inInfo)对象中】（此步骤省略...）

2. 接收参数，通过jdbc的方法(jdbc连接数据库步骤省略...)查询数据库数据，`getMetaData()`直接操作数据库便捷，但效率可能较低

3. 通过response对象获得输出流，将SXSSFWorkbook写入到浏览器

   	//jdbc方式保存到excel
   	public EiInfo downData(EiInfo inInfo) {
   		String sql = convertToSQL(date_PRC1, date_PRC2, type);
   		String sheetName = convertToSheetName(type);
   		HttpServletResponse response =(HttpServletResponse) inInfo.get("response");
   		SXSSFWorkbook xswb;
   		try {
   			// 创建xlsx
   			xswb = createXlsx(sql, sheetName);
   			
   			// 生成文件
   			response.setContentType("application/vnd.ms-excel");
   			response.setHeader("Content-Disposition", "attachment;filename=" + URLEncoder.encode(sheetName, "utf-8"));
   			OutputStream outputStream;
   			outputStream = response.getOutputStream();
   			xswb.write(outputStream);
   			outputStream.flush();
   			outputStream.close();
   		} catch (Exception e) {
   			e.printStackTrace();
   			inInfo.set("status", false);
   			inInfo.set("msg", "导出失败！");
   			return inInfo;
   		}
   		return inInfo;
   	}
   

   　　

/*
* 传入sql语句，和需要的命名
* 返回工作簿对象
*/
private SXSSFWorkbook createXlsx(String sql, String sheetName) throws Exception {
        SXSSFWorkbook xswb = null;
        Connection con = null;
        Statement st = null;
        ResultSet rs = null;
        try {
            con = JDBCUtils.getConnection();
            st = con.createStatement(ResultSet.TYPE_SCROLL_INSENSITIVE, ResultSet.CONCUR_READ_ONLY);

            xswb = new SXSSFWorkbook();
            // 创建工作表
            Sheet sheet = xswb.createSheet();
            xswb.setSheetName(0, sheetName);
            // 查询数据
            rs = st.executeQuery(sql);
            System.out.println(rs);
            ResultSetMetaData metaData = rs.getMetaData();
            int columnCount = metaData.getColumnCount();

            // 创建表头
            Row head = sheet.createRow(0);
            for (int i = 0; i < columnCount; i++) {
                Cell cell = head.createCell(i);
                cell.setCellValue(metaData.getColumnName(i + 1));
            }
            // 获取总行数
            rs.last();
            int rowCount = rs.getRow();
            rs.beforeFirst();

            // 创建标题
            for (int i = 1; i <= rowCount; i++) {
                rs.next();
                Row row = sheet.createRow(i);
                for (int j = 0; j < columnCount; j++) {
                    Cell cell = row.createCell(j);
                    cell.setCellValue(rs.getString(j + 1));
                }
            }
        } catch (Exception e) {
            throw new Exception(e);
        } finally {
            JDBCUtils.colseResource(con, st, rs);
        }
        return xswb;
    }