简单的验证码

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简单的验证码

 

 

验证码

1. 本质：图片

2. 目的：防止恶意表单注册

 

创建CheckCodeServlet 并在其中写验证码

package wdnmd.web.servlet;

import javax.imageio.ImageIO;
import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.awt.*;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.util.Random;

@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，在内存中图片(验证码图片对象)
        BufferedImage image = new BufferedImage(width,height,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);//设置画笔颜色
        g.fillRect(0,0,width,height);

        //2.2画边框
        g.setColor(Color.BLUE);
        g.drawRect(0,0,width - 1,height - 1);

        String str = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghigklmnopqrstuvwxyz0123456789";
        //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
            //2.3写验证码
            g.drawString(ch+"",width/5*i,height/2);
        }


        //2.4画干扰线
        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);
        }


        //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);
    }
}

 

 

 html

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</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(){
        //1.获取图片对象
        var img = document.getElementById("checkCode");
        var cha = document.getElementById("change");
        //2.绑定单击图片事件
        img.onclick = function(){
            //加时间戳
            var date = new Date().getTime();
            img.src = "/checkCodeServlet?"+date;
        }
       //3.绑定点击超链接时间
         cha.onclick = function () {
                var date = new Date().getTime();
                img.src = "checkCodeServlet?"+date;
            }  
    }
    </script>

</head>
<body>

    <img id="checkCode" src="/checkCodeServlet" />
    <a id="change" href="">看不清换一张？</a>

</body>
</html>

 

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