动态生成验证码

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CodeServlet 类

package com.dml.a_response.c_download;import java.awt.Color;import java.awt.Font;import java.awt.Graphics;import java.awt.Graphics2D;import java.awt.image.BufferedImage;import java.io.IOException;import java.util.Random;import javax.imageio.ImageIO;import javax.servlet.ServletException;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;public class CodeServlet extends HttpServlet {        public void doGet(HttpServletRequest request, HttpServletResponse response)                throws ServletException, IOException {            // 使用java图形界面技术绘制一张图片            int charNum = 4;            int width = 30 * 4;            int height = 30;            // 1. 创建一张内存图片            BufferedImage bufferedImage = new BufferedImage(width, height,                    BufferedImage.TYPE_INT_RGB);            // 2.获得绘图对象            Graphics graphics = bufferedImage.getGraphics();            // 3、绘制背景颜色            graphics.setColor(Color.YELLOW);            graphics.fillRect(0, 0, width, height);            // 4、绘制图片边框            graphics.setColor(Color.BLUE);            graphics.drawRect(0, 0, width - 1, height - 1);            // 5、输出验证码内容            graphics.setColor(Color.RED);            graphics.setFont(new Font("宋体", Font.BOLD, 20));            // 随机输出4个字符            Graphics2D graphics2d = (Graphics2D) graphics;             String s = "ABCDEFGHGKLMNPQRSTUVWXYZ23456789";            Random random = new Random();            //session中要用到            String msg="";            int x = 5;            for (int i = 0; i < 4; i++) {                int index = random.nextInt(32);                String content = String.valueOf(s.charAt(index));                msg+=content;                double theta = random.nextInt(45) * Math.PI / 180;                //让字体扭曲                graphics2d.rotate(theta, x, 18);                graphics2d.drawString(content, x, 18);                graphics2d.rotate(-theta, x, 18);                x += 30;            }            // 6、绘制干扰线            graphics.setColor(Color.GRAY);            for (int i = 0; i < 5; i++) {                int x1 = random.nextInt(width);                int x2 = random.nextInt(width);                int y1 = random.nextInt(height);                int y2 = random.nextInt(height);                graphics.drawLine(x1, y1, x2, y2);            }            // 释放资源            graphics.dispose();            // 图片输出 ImageIO            ImageIO.write(bufferedImage, "jpg", response.getOutputStream());        }    public void doPost(HttpServletRequest request, HttpServletResponse response)            throws ServletException, IOException {    }}

code.html

<!DOCTYPE html><html><head><meta charset="UTF-8"><title>Insert title here</title></head><body>    <img alt="验证码" src="/day10/code" title="看不清楚换一张" onclick="changeImg(this)"></body><script type="text/javascript">    function changeImg(obj){        //操作src属性        obj.src="/day10/code?i="+Math.random();//可以改变请求否则会取缓存的数据    }    </script></html>

效果图

这里写图片描述

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