第一种:随机图片
第二种;代码生成
java代码：
@WebServlet("/checkCodeServlet")
public class checkCodeServlet extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
}
protected void doGet(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
Graphics g = image.getGraphics();//创建画笔对象
g.setColor(Color.pink);//设置画笔的颜色
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 = "ABCDEFGHKIJMNOPQRSTUWXYZabcdefghijklmnopqrstuwxyz0123456789";
//生成随机角标
Random random = new Random();
for (int i = 1; i<=4;i++) {
int index = random.nextInt(str.length());
//获取字符
char ch = str.charAt(index);
//写验证码
g.drawString(ch+"",width/5*i,height/2);
}
//画干扰线
g.setColor(Color.green);
for (int i = 0; i < 10; i++) {
int x1 = random.nextInt(width);
int x2 = random.nextInt(width);
int y1 = random.nextInt(width);
int y2 = random.nextInt(width);
g.drawLine(x1,x2,y1,y2);
}
//3.将图片输出到页面
ImageIO.write(image,"jpg",response.getOutputStream());
}
}
html页面;
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Title</title>
<script>
/*
* 分析：
* 点击图片或者超链接，需要换一张图片
* 1.给超链接和图片添加点击事件
* 2.重新设置图片的src属性值*/
window.onload = function () {
//获取图片对象
var image = document.getElementById("checkCode");
image.onclick = function () {
//加时间戳
var date = new Date().getTime();
image.src="/day17_tomact_war_exploded/checkCodeServlet?"+date;
}
}
</script>
</head>
<body>
<img src="/day17_tomact_war_exploded/checkCodeServlet" id="checkCode">
<a id="change" href="javascript:void(0)">看不清换一张图片？</a>
</body>
</html>
原文：https://www.cnblogs.com/naigai/p/11809196.html