idea写验证码

本文链接： https://blog.csdn.net/qq_42177478/article/details/89891885

CheckCodeServlet.java

package cn.jk;
import javax.imageio.ImageIO;
import javax.servlet.annotation.WebServlet;
import java.awt.*;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.util.Random;
@WebServlet("/checkcode")
public class CheckcodeServlet extends javax.servlet.http.HttpServlet {
    protected void doPost(javax.servlet.http.HttpServletRequest request, javax.servlet.http.HttpServletResponse response) throws javax.servlet.ServletException, IOException {
doGet(request, response);

    }
    protected void doGet(javax.servlet.http.HttpServletRequest request, javax.servlet.http.HttpServletResponse response) throws javax.servlet.ServletException, IOException {
            //1.在内存生成一个图片
            int width = 120;
            int height = 30;
            BufferedImage img = new BufferedImage(width,height,BufferedImage.TYPE_INT_RGB);
            Graphics2D g =(Graphics2D) img.getGraphics();//获取画笔；
            g.setColor(Color.yellow);//设置颜色
            g.fillRect(0,0,width,height);//填充矩形；
            g.setColor(Color.BLUE);
            g.drawRect(0,0,width-1,height-1);//画边框
            String words = "ABCDEFGHIGKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz123456789";//给定数据；
            g.setFont(new Font("隶书",Font.BOLD,20));//设置字体
            Random random = new Random();//给定四个随机数；
            int x = 20,y = 20;
            for(int i = 0;i<4;i++){
                int jiaodu = random.nextInt(60)-30;
                double hudu = jiaodu*Math.PI/180;
                g.rotate(hudu,x,y);
                int index = random.nextInt(words.length());//随机xiabiao；
                char ch = words.charAt(index);
                g.rotate(-hudu,x,y);
                g.drawString(""+ch,x,y);
                x+=20;
            }
            //画四条线
            g.setColor(Color.red);
            int x1,x2,y1,y2;
            for(int i = 0;i<4;i++){
                x1 = random.nextInt(width);
                y1 = random.nextInt(height);
                x2 = random.nextInt(width);
                y2 = random.nextInt(height);
                g.drawLine(x1,y1,x2,y2);
            }

//显示到画布页面；
            ImageIO.write(img,"jpg",response.getOutputStream());
        }
    }

index.jsp

%--
  Created by IntelliJ IDEA.
  User: Administrator
  Date: 2019/4/30 0030
  Time: 下午 4:17
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
  <head>
    <title>$Title$</title>
  </head>
  <body>
  <form action=" " method = "post">
    <table>
      <tr>
        <td>输入姓名</td>
        <td><input type = "text" name = "username"></td>
      </tr>
      <tr>
        <td>输入密码</td>
        <td><input type = "password" name = "password"></td>
      </tr>
      <tr>
        <td>验证码</td>
        <td>
          <input type = "text" name = "check">
          <a href="#" onclick=run()><img id = "imgId" src = "checkcode"></a>
          <a href="#" onclick=run()>看不清换一张</a>
        </td>
      </tr>
    </table>
  </form>
  </body>
<script type="text/javascript">
  function run(){
    var image = document.getElementById("imgId");//获取表单元素 通过ID‘
    image.src = "checkcode?"+new Date().getTime();
  }
</script>
</html>

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