下面分享的是我曾经开发中遇到的问题：将上传的图片或程序生成的图片转换成二进制存入数据库，数据库中保存该图片的字段类型为blob

//这里是将自动生成的图片转换成二进制
BufferedImage image= new BufferedImage(100,100, BufferedImage.TYPE_INT_RGB);
Graphics2D g = image.createGraphics();
g.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
g.clearRect(0, 0, 100, 100);//创建一个100*100的画布
Color c=new Color(45,204,112);//背景色
g.setColor(c);
g.fillRect(0, 0, 100, 100);
g.setColor(new Color(255,255,255));//字体颜色
Font font = new Font("宋体", Font.BOLD, 25);//字体、加粗、大小
g.setFont(font);

String name= "张三";
//根据name长度自动调整名字在画布中的左右文字
int nameLeng=name.getBytes().length;//名称字节长度
float x_f=(float) (100-(nameLeng*13.5))/2;//X轴偏移量
int x=Math.round(x_f);//偏移量取整
g.drawString(name, x, 60);

//重点来了
ByteArrayOutputStream bs =new ByteArrayOutputStream();
ImageOutputStream imOut =ImageIO.createImageOutputStream(bs);

ImageIO.write(image,"jpg",imOut); //
byte[] b=bs.toByteArray();
Session sessions = getSessionFactory().openSession();
LobHelper lobHelper = sessions.getLobHelper();
Blob blob = lobHelper.createBlob(b);

//此方法用于将上传的图片转换成Blob
public Blob SetImageToByteArray(String zplj){
        FileInputStream is = null;
        Blob blob = null;
        Session session = getSessionFactory().openSession();
        try {
            File file = new File(zplj);
            is = new FileInputStream(file);
            int streamLength = (int)file.length();
            byte[] image = new byte[streamLength];
            is.read(image, 0, streamLength);//将字节流转换为byte数组
            LobHelper lobHelper = session.getLobHelper();
            blob = lobHelper.createBlob(image);
        } catch (IOException e) { e.printStackTrace(); } finally{ try { //关闭输出流
            is.close();
        } catch (IOException e) {
            e.printStackTrace();
        }finally {
            session.close(); }
        }
        return blob;
}

//本页面为getImg.jsp

//这里是将二进制转换成图片
Blob blob = ？？;//这里的？是从数据库获取的二进制图片
BufferedInputStream inputimage = new BufferedInputStream(blob.getBinaryStream());
try{
    BufferedImage image = ImageIO.read(inputimage);
    OutputStream sos = response.getOutputStream();
    JPEGImageEncoder encoder = JPEGCodec.createJPEGEncoder(sos);
    encoder.encode(image);
    inputimage.close();
    out.clear();
    out = pageContext.pushBody();
}catch(IOException e){
    System.out.println(e);
}

//前台页面使用方法
$("#exit_div").empty().append("<img src='getImg.jsp?ran="+Math.random()+"' />");