mysql导出blob数据,数据库中blob类型怎么存取

一般情况下图片的保存在hdfs上，数据库只保存图片的路径，特殊情况采用这个方案。
数据库方面：

实体方面采用byte数组进行存取：

private byte[] img;

我在本地磁盘放了一张图片，现在进行读取：

public String save(){//创建实体DashboardBoard board = new DashboardBoard();byte[] inputStream2ByteArray; try { inputStream2ByteArray = InputStream2ByteArray("D:\ceshi.png"); } catch (IOException e) { e.printStackTrace(); } board.setImg(exportBoard); //调用保存方法 boardDao.save(board); //具体业务~略 } //主要的工具方法 public byte[] InputStream2ByteArray(String filePath) throws IOException { InputStream in = new FileInputStream(filePath); byte[] data = toByteArray(in); in.close(); return data; } public byte[] toByteArray(InputStream in) throws IOException { ByteArrayOutputStream out = new ByteArrayOutputStream(); byte[] buffer = new byte[1024 * 4]; int n = 0; while ((n = in.read(buffer)) != -1) { out.write(buffer, 0, n); } return out.toByteArray(); }

通过以上方式可以把图片以二进制的方式保存到数据库中，亲测，有效。

图片的显示：

前台页面使用img标签进行图片的显示 <img src="localhost:8080/xxx/getBoardDataImg.do?id=xx&width=150&height=150" />

后台代码：

@RequestMapping(value = "/getBoardDataImg") @ResponseBody public String ceshi(@RequestParam(name = "id") Long id ,@RequestParam(name = "width") int width,@RequestParam(name = "height") int height, HttpServletResponse response,HttpServletRequest request) throws IOException{ DashboardBoard board = boardDao.getBoard(id); byte[] data = board.getImg(); //获取缩略图 data = boardService.scaleImage(data, width, height); response.setContentType("image/jpeg"); response.setCharacterEncoding("UTF-8"); OutputStream outputSream = response.getOutputStream(); InputStream in = new ByteArrayInputStream(data); int len = 0; byte[] buf = new byte[1024]; while ((len = in.read(buf, 0, 1024)) != -1) { outputSream.write(buf, 0, len); } outputSream.close(); return null; }}/** * 获取缩略图 * @throws IOException */ public byte[] scaleImage(byte[] data, int width, int height) throws IOException { BufferedImage buffered_oldImage = ImageIO.read(new ByteArrayInputStream(data)); int imageOldWidth = buffered_oldImage.getWidth(); int imageOldHeight = buffered_oldImage.getHeight(); double scale_x = (double) width / imageOldWidth; double scale_y = (double) height / imageOldHeight; double scale_xy = Math.min(scale_x, scale_y); int imageNewWidth = (int) (imageOldWidth * scale_xy); int imageNewHeight = (int) (imageOldHeight * scale_xy); BufferedImage buffered_newImage = new BufferedImage(imageNewWidth, imageNewHeight, BufferedImage.TYPE_INT_RGB); buffered_newImage.getGraphics().drawImage( buffered_oldImage.getScaledInstance(imageNewWidth, imageNewHeight, BufferedImage.SCALE_SMOOTH), 0, 0, null); buffered_newImage.getGraphics().dispose(); ByteArrayOutputStream outPutStream = new ByteArrayOutputStream(); ImageIO.write(buffered_newImage, "jpeg", outPutStream); return outPutStream.toByteArray(); }}

使用流展示图片到前端，通过设置width和height进行缩略图的处理