Response验证码案例的分析和代码实现

Response验证码案例的分析

本质：是一张图片

目的：防止恶意表单注册

步骤：

　　1、创建一对象，在内存中画图（验证码图片对象）

　　2、美化图片

　　3、将图片输出到页面展示

 

@WebServlet("/checkCodeServlet")
public class CheckCodeServlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        int width = 100;
        int height = 50;
        //1、创建一对象，在内存中画图（验证码图片对象）
        BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
        //2、美化图片
        //填充背景色
        Graphics g = image.getGraphics();
        g.setColor(Color.PINK);
        g.fillRect(0,0,width,height);
        //画边框
        g.setColor(Color.BLUE);
        g.drawRect(0,0,width-1,height-1);
        //写验证码
        String str = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghigklmnopqrstuvwxyz0123456789";
        //生成随机角标
        Random ra = new Random();

        for (int i = 1; i <= 4; i++) {
            int index = ra.nextInt(str.length());
            //获取字符
            char c = str.charAt(index);
            //写验证码
            g.drawString(c+"",width/5*i,height/2);
        }

        //画干扰线
        g.setColor(Color.GREEN);
        //随机生成坐标点
        for (int i = 0; i < 10; i++) {
            int x1 = ra.nextInt(width);
            int x2 = ra.nextInt(width);

            int y1 = ra.nextInt(height);
            int y2 = ra.nextInt(height);
            g.drawLine(x1,y1,x2,y2);
        }

        //3、将图片输出到页面展示
        ImageIO.write(image,"jpg",response.getOutputStream());
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        this.doPost(request, response);
    }
}