随机生成验证码

news2024/12/27 3:32:13

1.servlet代码
/**
* 随机生成验证码
* 1.获取Image对象
* 2.1填充背景色 2.2画边框生成随机角标 2.3写验证吗 2.4 画干扰线
*3.将图片输出到页面
*/

package cn.itcast.web.servlet;

import javax.imageio.ImageIO;
import javax.servlet.*;
import javax.servlet.http.*;
import javax.servlet.annotation.*;
import java.awt.*;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.util.Random;

@WebServlet("/CheckCodeServlet")
public class CheckCodeServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        /**
         * 随机生成验证码
         * 1.获取Image对象
         * 2.1填充背景色 2.2画边框 生成随机角标 2.3写验证吗 2.4 画干扰线
         *3.将图片输出到页面
         */
        int width = 100;
        int heigth = 50;

        //1.在内存中创建对象
        BufferedImage image = new BufferedImage(width,heigth,BufferedImage.TYPE_INT_RGB);
        //2.美化图片
        //2.1 填充背景色
        Graphics g = image.getGraphics();//画笔对象
        g.setColor(Color.PINK);
        g.fillRect(0,0,width,heigth);
        //2.2画边框
        g.setColor(Color.BLUE);
        g.drawRect(0,0,width-1,heigth-1);
        //生成随机角标
        String str = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghigklmnopqrstuvwxyz0123456789";
        Random r = new Random();
        for (int i = 1; i <= 4; i++) {
            //获取字符位置
            int index =  r.nextInt(str.length());
            //获取字符
            char ch = str.charAt(index);
            g.drawString(ch+"",width/5*i, heigth / 2);
        }

        //生成干扰线
        for (int i = 0; i < 5; i++) {
            int x1 = r.nextInt(width);
            int x2 = r.nextInt(width);
            int y1 = r.nextInt(heigth);
            int y2 = r.nextInt(heigth);
            g.drawLine(x1,x2,y1,y2);
        }

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

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

效果
在这里插入图片描述
在前端展示验证码切换
2.HTML代码
分析：
点击超链接或者图片，需要换一张
1.给超链接和图片绑定单击事件

            2.重新设置图片的src属性值

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>切换验证码</title>
    <script>
        /*
            分析：
                点击超链接或者图片，需要换一张
                1.给超链接和图片绑定单击事件

                2.重新设置图片的src属性值

         */
        window.onload = function (){
            var img = window.document.getElementById("checkcode");
            img.onclick = function () {
                var date = new Date().getTime();
                img.src = "/day14/CheckCodeServlet?" + date;

            }
        }
    </script>

</head>
<body>
<img id="checkcode" src="/day14/CheckCodeServlet">
<a id="change" href="#">看不清换一张?</a>
</body>
</html>