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());

    }