017-Servlet动态生成验证码demo

验证码

1. 本质：图片
2. 目的：防止恶意表单注册

/**
 * 动态生成验证码
 */
@WebServlet("/checkCodeServlet")
public class CheckCodeServlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //定义验证码的宽高
        int width = 100;
        int height = 50;
        //创建一对象，在内存中图片(验证码图片对象)
        BufferedImage image = new BufferedImage(width,height,BufferedImage.TYPE_INT_RGB);
        //美化图片
        //填充背景色
        Graphics g = image.getGraphics();//画笔对象
        g.setColor(Color.PINK);//设置画笔颜色
        g.fillRect(0,0,width,height);//画背景
        //画边框
        g.setColor(Color.BLUE);
        g.drawRect(0,0,width - 1,height - 1);

        //动态生成验证码数据源
        String str = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghigklmnopqrstuvwxyz0123456789";
        //生成随机角标
        Random ran = new Random();
        for (int i = 1; i <= 4; i++) {//生成4位验证码
            int index = ran.nextInt(str.length());
            //获取字符
            char ch = str.charAt(index);//随机字符
            //写验证码到图片中
            g.drawString(ch+"",width/5*i,height/2);
        }
        //画干扰线10条
        g.setColor(Color.GREEN);
        //随机生成坐标点
        for (int i = 0; i < 10; i++) {
            int x1 = ran.nextInt(width);
            int x2 = ran.nextInt(width);
            int y1 = ran.nextInt(height);
            int y2 = ran.nextInt(height);
            g.drawLine(x1,y1,x2,y2);//划线
        }
        //将图片输出到页面展示，通过response对象写回给浏览器
        ImageIO.write(image,"jpg",response.getOutputStream());
    }
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        this.doPost(request,response);
    }
}