验证码
1. 本质：图片
2. 目的：防止恶意表单注册
import javax.imageio.ImageIO;
import javax.servlet.ServletException;
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.BufferedInputStream;
import java.io.IOException;
import java.util.Random;
/**
* @author Lucky
* @Date 2020/6/18 19:32
*/
@WebServlet("/checkCodeServlet")
public class CheckCodeServlet extends HttpServlet {
@Override
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
int width = 100;
int height = 50;
// 1.创建一对象，在内存图中（验证码图片对象）
BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_3BYTE_BGR);
// 2.美化图片
// 2.1填充背景色
// 画笔对象
Graphics g = image.getGraphics();
// 设置画笔颜色
g.setColor(Color.PINK);
// 填充矩形
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 = "ABCDEFGHIGKLMNOPQRSTUVWXYZabcdefghigklmnopqrstuvwxyz1234567890";
// 生产随机角标
Random ran = new Random();
for (int i = 1; i <=4; i++) {
int index = ran.nextInt(str.length());
// 获取字符 随机字符
char ch = str.charAt(index);
//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(width);
int y2 = ran.nextInt(width);
g.drawLine(x1,y1,x2,y2);
}
// 3.将图片输出到页面展示
ImageIO.write(image,"jpg",response.getOutputStream());
}
@Override
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
this.doPost(request,response);
}
}
点击图片换验证码
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>验证码</title>
<script>
/*
分析：点击超链接或图片，需要换一张
1.给超链接和图片添加单击事件
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 () {
var date = new Date().getTime();
img.src = "/day15_response/checkCodeServlet?"+date;
}
}
</script>
</head>
<body>
<img id="checkCode" src = "/day15_response/checkCodeServlet" />
<a id="change" href="">看不清换一张？</a>
</body>
</html>