java Web 请求servlet绘制验证码简单例子

主要用来了解java代码怎么绘制验证码图片,实际开发中不会这样用

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //生成画布
        int width = 120;
        int height = 40;
        BufferedImage bi = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
        //获取画笔
        Graphics g = bi.getGraphics();
        //填充背景色
        g.setColor(Color.white);//背景色
        g.fillRect(0, 0, width, height);//在画布的位置
        //绘制边框
        g.setColor(Color.green);//边框颜色
        g.drawRect(0, 0, width - 1, height - 1);//边框大小
        //生成4个随机字符 并放到code变量中
        String code = "";
        Random rd = new Random();
        String data = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz1234567890";
        for (int i = 0; i < 4; i++) {
            //设置字体
            g.setFont(new Font("微软雅黑", Font.BOLD, 30));
            //设置颜色
            g.setColor(new Color(rd.nextInt(255), rd.nextInt(255), rd.nextInt(255)));
            //绘制字符
            String str = data.charAt(rd.nextInt(data.length())) + "";
            g.drawString(str, 10 + i * 30, 30);
            code += str;
        }
        //绘制干扰线
        for (int i = 0; i < 5; i++) {
            //干扰线随机颜色
            g.setColor(new Color(rd.nextInt(255), rd.nextInt(255), rd.nextInt(255)));
            //绘制干扰线
            g.drawLine(rd.nextInt(width), rd.nextInt(height), rd.nextInt(width), rd.nextInt(height));
        }
        //输出到页面
        ImageIO.write(bi, "png", response.getOutputStream());
    }