protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
int width = 100;
int height = 50;
//1.创建一个对象，在内存中图片（验证码的图片对象）
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();
g.setColor(Color.PINK);
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 = "ABCDEFGHIGKLMNOPQRSTUVWXYZqwertyuiopasdfghjklzxcvbnm0123456789";
//生成随机角标
Random ran = new Random();
for (int i = 1; i <= 4; i++) {
int index = ran.nextInt(str.length());
//获取字符
char ch = str.charAt(index);//随机字符
//2.3写验证码
g.drawString(ch+"", width/5*i, height/2);
}
//2.4画干扰线
g.setColor(Color.GREEN);
//随机生成坐标点
for (int i = 0; i < 10; i++) {
int x1 = ran.nextInt(width);
int x2 = ran.nextInt(width);
int y1 = ran.nextInt(height);
int y2 = ran.nextInt(height);
g.drawLine(x1,y1,x2,y2);
}
//3.将图片输出到页面展示
ImageIO.write(image,"jpg",response.getOutputStream());
} 再绑定注册页面，实现单机图片即可换一张的功能。
register.html
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Title</title>
<script>
/*
分析：
点击超链接或者图片，需要换一张
1.给超链接和图片绑定单机时间
2.重新设置图片的src属性值
*/
window.onload = function (){
//1.获取图片对象
var img = document.getElementById("checkCode");
//2.绑定单击事件
img.onclick = function () {
//加时间戳
var date = new Date().getTime(); //获取毫秒值
img.src = "/day15_response_war_exploded/CheckCodeServlet?" + date;
}
}
</script>
</head>
<body>
<img id = "checkCode" src="/day15_response_war_exploded/CheckCodeServlet" />
<a id="change" href="">看不清换一张</a>
</body>
</html> ![Java小案例——随机数猜测随机数猜测[图]](data:image/gif;base64,R0lGODlhAQABAIAAAP///wAAACwAAAAAAQABAAACAkQBADs=)