随笔- 446 文章- 0 评论- 0 阅读- 42534

Response验证码和验证码点击切换

Response验证码

验证码：

　　1.本质：就是一张图片

　　2.目的：防止恶意表单注册

分析：>创建一对象，在内存中图片(验证码图片对象)

>美化图片

>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;
        //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
        //1.填充背景色
        Graphics g = image.getGraphics();
        g.setColor(Color.blue);
        g.fillRect(0,0,width,height);
        //2.画边框
        g.setColor(Color.CYAN);
        g.drawRect(0,0,width-1,height-1);
        //写验证码
        //页面的页码数字
        String str = "ABCDEFGHIGKLMNOPQRSTUVWXYZabcdefghigklmnopqrstuvwxyz0123456789";
        //生成随机角标
        Random ran = new Random();
        for (int i = 1; i <=4; i++) {
            int index = ran.nextInt(str.length());
            //获取字符
            char ch = str.charAt(index);//随机字符
            g.drawString(ch+"",width/5*i,height/2);
        }
        //画干扰线
        g.setColor(Color.green);
        //随机生成坐标点
        for (int i = 1; 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);
        }

        //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);
    }
}

刷新页面会进行变化

Response验证码点击切换

创建一个html页面

编写img绑定事件：

如果不获取事件戳，会加载缓存中的图片从而不进行变换，加一个用不重复的值欺骗服务器说图片发生了变化

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <script>
        window.onload = function () {
            //获取图片对象
            var img = document.getElementById("checkCode");
            //绑定单击事件
            img.onclick = function () {
                //加时间戳
                var date = new Date().getTime();
                img.src = "/checkCodeServlet?"+date;
            }
        }
    </script>
</head>
<body>
<img id="checkCode" src="/checkCodeServlet"/>
</body>
</html>