验证码
本质：图片
目的：防止恶意表单注册
int width = 100;
int height = 50;
//1.创建验证码对象
BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_BGR);
//2.美化图片
//2.1填充背景色
Graphics g = image.getGraphics();//画笔对象
g.setColor(Color.PINK); //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);
String str = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789";
//生成随机角标
Random ran = new Random();
String yanzhengma = "";
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);
yanzhengma = yanzhengma + ch;
}
System.out.println(yanzhengma); //验证码的值
//2.4画干扰线
g.setColor(Color.GREEN);
for (int i = 0; i < 10; i++) {
//随机生成坐标点
int x1 = ran.nextInt(width);
int x2 = ran.nextInt(width);
int y1 = ran.nextInt(height);
int y2 = ran.nextInt(height);
g.drawLine(x1, x2, y1, y2);
}
//设置响应头通知浏览器以图片的形式打开
resp.setContentType("image/jpeg");
//设置响应头控制浏览器不要缓存
resp.setDateHeader("expries", -1);
resp.setHeader("Cache-Control", "no-cache");
resp.setHeader("Pragma", "no-cache");
//3.将图片输出到页面展示
ImageIO.write(image, "jpg", resp.getOutputStream());
点击切换
<!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，换一张图片
* 1.给超链接和图片绑定单击事件
* 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();
img.src = "/responseDemo01?" + date;
}
}
</script>
</head>
<body>
<img id="checkCode" src="/responseDemo01">
<a id="change" href="">看不清？点击换一张</a>
</body>
</html>
加上验证功能
- demo1
req.getSession().setAttribute("checkcode", yanzhengma); // 将验证码传到Demo02 用于验证
- demo2
String serverCheckcode = (String) req.getSession().getAttribute("checkcode");
String result = req.getParameter("yanzhengma");
if (serverCheckcode.equals(result)) {
System.out.println("yes");
} else {
System.out.println("no");
}
- html
<form action="/responseDemo02" method="post">
验证码:<input type="text" name="yanzhengma"> <br>
<input type="submit" value="提交">
</form>
