java中BufferedImage
@Override protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { //如何让浏览器3秒自动刷新一次; resp.setHeader("refresh","3"); //在内存中创建一个图片 BufferedImage image = new BufferedImage(80,20,BufferedImage.TYPE_INT_RGB); //得到图片 Graphics2D g = (Graphics2D) image.getGraphics();//笔 //设置图片的背景颜色 g.setColor(Color.white); g.fillRect(0,0,80,20); //给图片写数据 g.setColor(Color.BLUE); g.setFont(new Font(null,Font.BOLD,20));// ?,字体,大小 g.drawString(makeNum(),0,20);//画一个字符串 //告诉浏览器,这个请求用图片的方式打开 resp.setContentType("image/jpg");//设置响应他的类型 //网站存在缓存,不让浏览器缓存 resp.setDateHeader("expires",-1);//把expires设置成-1网站就不会缓存了 resp.setHeader("Cache-Control","no-cache");//Cache-Control缓存控制 不缓存 resp.setHeader("Pragme","no-cache"); //把图片写给浏览器 ImageIO.write(image,"jpg",resp.getOutputStream()); } //生成随机数 private String makeNum(){ Random random = new Random();//Random创建随机类 String num = random.nextInt(999999)+""; StringBuffer sb = new StringBuffer();//Stringbuffer是动态字符串数组 for (int i = 0; i < 4-num.length() ; i++) { sb.append("0");//append()是往动态字符串数组添加 } num = sb.toString() + num; return num; }
去webapp下做一个映射
即可运行