java动态实现验证码，供大家参考，具体内容如下
【实现效果】
验证码的功能： 防止恶意的表单注册
package com.iqqcode.servlet.checkcode;
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;
/**
* @Author: Mr.Q
* @Date: 2020-02-12 10:12
* @Description:验证码生成
*/
@WebServlet("/VerificationCode")
public class VerificationCode extends HttpServlet {
@Override
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
int width = 120;
int height = 50;
//1.创建对象,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();
Graphics2D g = (Graphics2D) image.getGraphics();//画笔对象,2D来旋转验证码字母
g.setColor(Color.WHITE);//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);
//2.3生成验证码
String str = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789";
//生成随机角标
Random random = new Random();
//改变字体
g.setFont(new Font("宋体",Font.BOLD,35));
//将验证码偏转并写到画布上
for (int i = 1; i <= 4; i++) {
int x = width/5 * i;
int y = height/2;
String msg = "";
int index = random.nextInt(str.length());
//获取字符
char ch = str.charAt(index);//随机字符
//获取正负30的角度
int angle = random.nextInt(60) - 30;
double radian = angle * Math.PI/180;
//设置验证码中的字体颜色
//g.setColor(Color.BLUE);
int red = 0; int green = 0; int blue = 0;
int codeY = 32;
// 得到随机产生的验证码数字
// 产生随机的颜色分量来构造颜色值,使输出的每位数字的颜色值都不同
red = random.nextInt(255);
green = random.nextInt(255);
blue = random.nextInt(255);
// 用随机产生的颜色将验证码绘制到图像中
g.setColor(new Color(red, green, blue));
//写验证码
g.rotate(radian, x, y);
//把字母画在画布上
//g.drawString(ch+"", x, y);
g.drawString(String.valueOf(ch)+"", x, codeY);
//把每次旋转的再旋转回来
g.rotate(-radian, x, y);
//每次向右移动20像素
x += 15;
msg += ch;
}
//2.4随机产生20条干扰线，使图象中的认证码不易被其它程序探测到
g.setColor(Color.MAGENTA);
//随机生成坐标点
for (int i = 0; i < 20; i++) {
int x1 = random.nextInt(width);
int x2 = random.nextInt(width);
int y1 = random.nextInt(height);
int y2 = random.nextInt(height);
g.drawLine(x1, x2, y1, y2);
}
//3.将图片输出到页面展示
//将图片对象写入流中
ImageIO.write(image, "jpg", response.getOutputStream());
}
@Override
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
this.doPost(request, response);
}
}
分析:
生成的图片先要缓存在本地,每次请求是不会修改，所以验证码图片不会切换;
将图片路径后添加时间戳,通过错误的路径来欺骗服务器重新请求
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
<title>验证码</title>
<script>
window.onload = function () {
//1.获取图片对象
var img = document.getElementById("checkCode");
//2.绑定图片单击事件
img.onclick = function () {
//加时间戳
var date = new Date().getTime();
//加时间戳，防止浏览器利用缓存
img.src = "/ServletResponse/VerificationCode?" + date;
}
//绑定链接点击事件
var ahref = document.getElementById("change");
ahref.onclick = function () {
var date = new Date().getTime();
img.src = "/ServletResponse/VerificationCode?" + date;
}
}
</script>
</head>
<body>
<h2>验证码动态实现</h2>
<img id="checkCode" src="/ServletResponse/VerificationCode">
<a id="change" href="">看不清?换一张</a>
</body>
</html>
