idea编写验证码并且实现点击更换验证码功能

checkcode.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" %>

  
    
  
  
  

    

      

        
输入姓名
        

      
      

        
输入密码
        

      
      

        
验证码
        

          
          
          看不清换一张