JavaWeb10-Servlet实现随机产生图片验证码

YanZhengMaServlet

public class YanZhengMaServlet extends HttpServlet {
    // 生成随机数 4位
    public String makeRan(){
        String randnum = new Random().nextInt(9999) + "";
        StringBuffer sb = new StringBuffer();
        for (int i = 0; i < 4 - randnum.length(); i++) {
            sb.append("0");
        }
        randnum = sb.toString() + randnum;
        return randnum;
    }
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

        // 生成图片
        BufferedImage bufferedImage = new BufferedImage(80, 30, BufferedImage.TYPE_INT_RGB);
        // 生成一个笔
        Graphics2D graphics2D = (Graphics2D)bufferedImage.getGraphics();
        /*
            设置背景颜色
        */

        // 设置画笔颜色
        graphics2D.setColor(Color.white);
        // 填充颜色
        graphics2D.fillRect(0 ,0, 80, 30);
        // 将随机数写入图片
        graphics2D.setColor(Color.BLUE);
        graphics2D.setFont(new Font(null, Font.BOLD, 30));
        graphics2D.drawString(makeRan(), 5, 25);
        // 告诉浏览器文件类型
        resp.setContentType("image/jpeg");
        // 网站存在缓存， 设置为无缓存
        resp.setDateHeader("expires", -1);
        resp.setHeader("cache-Control" , "no-cache");
        // 把图片写出去 写给浏览器
        ImageIO.write(bufferedImage, "jpeg", resp.getOutputStream());
    }
    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doGet(req, resp);
    }
}