数据库文件下载

 @RequestMapping("/show")
 public void show(HttpServletRequest request, HttpServletResponse response) {
       Info info = (Info) request.getSession().getAttribute("info");
       String imgId = R.get("imgId");// 图片ID
       BLOB blob = super.wmsDao.findZp(imgId);
       if (blob != null) {
       // 得到java.sql.Blob对象后强制转换为oracle.sql.BLOB
              response.setContentType("image/jpeg");
              response.setHeader("Pragma", "No-cache");
              response.setHeader("Cache-Control", "no-cache");
              response.setDateHeader("Expires", 0);
              ServletOutputStream out;
              try {
                    out = response.getOutputStream();
                    out.write(blob.getBytes(1, (int) blob.length()));
                    out.flush();
                    out.close();
              } catch (Exception e) {
                     super.logDao.save(info, "失败！", "读取文件失败！");
                     e.printStackTrace();
              }
       }

 }