简易案例：后台生成验证码
作用
1. 防止恶意注册
2. 避免重复提交
代码
前端代码
<%--
Created by IntelliJ IDEA.
User: yllch
Date: 2020/10/20
Time: 10:15
To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
<title>用户注册页面</title>
</head>
<body>
<form action="" method="get">
<center>
用户名：<input type="text" name="username" placeholder="请输入用户名">
<br> <br>
密 码：<input type="password" name="password" placeholder="请输入密码">
<br> <br>
验证码：<input type="text" name="yan" placeholder="请输入验证码">
</center>
<br>
<center><img id="san" src="http://localhost:8080/ReqiestResponse_war_exploded/yan" alt="" height="50px" width="180px">
<button onclick="change()">刷新</button>
</center>
<br>
<center><input type="submit" value="提交"></center>
</form>
</body>
</html>
<script>
function change() {
document.getElementById("san").src("http://localhost:8080/ReqiestResponse_war_exploded/yan" + new Date().getTime());
}
</script>
后端代码
@WebServlet(name
= "ServletYan", value
= "/yan")
public class ServletYan extends HttpServlet {
protected void doPost(HttpServletRequest request
, HttpServletResponse response
) throws ServletException
, IOException
{
int width
=200;
int height
=100;
BufferedImage bufferedImage
= new BufferedImage(width
, height
, BufferedImage
.TYPE_INT_BGR
);
Graphics graphics
= bufferedImage
.getGraphics();
graphics
.setColor(Color
.PINK
);
graphics
.fillRect(0,0,width
,height
);
graphics
.setColor(Color
.LIGHT_GRAY
);
graphics
.drawRect(0,0,width
-1,height
- 1);
graphics
.setFont(new Font("楷体",Font
.PLAIN
,44));
graphics
.setColor(Color
.gray
);
Random random
= new Random();
String s
="abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
for (int i
= 1; i
<= 4; i
++) {
int nextInt
= random
.nextInt(s
.length());
char c
= s
.charAt(nextInt
);
graphics
.drawString(String
.valueOf(c
),width
/5*i
,height
/ 5*3);
}
graphics
.setColor(Color
.BLACK
);
for (int i
= 0; i
< 10; i
++) {
int w
= random
.nextInt(width
);
int h
= random
.nextInt(height
);
int w1
= random
.nextInt(width
);
int h1
= random
.nextInt(height
);
graphics
.drawLine(w
,h
,w1
,h1
);
}
ImageIO
.write(bufferedImage
,"png",response
.getOutputStream());
}
protected void doGet(HttpServletRequest request
, HttpServletResponse response
) throws ServletException
, IOException
{
this.doPost(request
, response
);
}
}
运行结果
好看一点的验证码
主体代码
@WebServlet(name
= "ServletZheng", value
= "/yan1")
public class ServletZheng extends HttpServlet {
protected void doPost(HttpServletRequest request
, HttpServletResponse response
) throws ServletException
, IOException
{
int width
= 200;
int height
= 69;
BufferedImage verifyImg
= new BufferedImage(width
, height
, BufferedImage
.TYPE_INT_RGB
);
String randomText
= VerifyCode
.drawRandomText(width
, height
, verifyImg
);
request
.getSession().setAttribute("verifyCode", randomText
);
response
.setContentType("image/png");
OutputStream os
= response
.getOutputStream();
ImageIO
.write(verifyImg
, "png", os
);
os
.flush();
os
.close();
}
protected void doGet(HttpServletRequest request
, HttpServletResponse response
) throws ServletException
, IOException
{
this.doPost(request
, response
);
}
}
工具类代码
package SanWa.YanZheng;
import java.awt.*;
import java.awt.image.BufferedImage;
import java.util.Random;
public class VerifyCode {
public static String drawRandomText(int width, int height, BufferedImage verifyImg) {
Graphics2D graphics = (Graphics2D) verifyImg.getGraphics();
graphics.setColor(Color.gray);//设置画笔颜色-验证码背景色
graphics.fillRect(0, 0, width, height);//填充背景
graphics.setFont(new Font("微软雅黑", Font.BOLD, 40));
//数字和字母的组合
String baseNumLetter = "123456789abcdefghijklmnopqrstuvwxyzABCDEFGHJKLMNPQRSTUVWXYZ";
StringBuffer sBuffer = new StringBuffer();
int x = 10; //旋转原点的 x 坐标
String ch = "";
Random random = new Random();
for (int i = 0; i < 4; i++) {
graphics.setColor(getRandomColor());
//设置字体旋转角度
int degree = random.nextInt() % 30; //角度小于30度
int dot = random.nextInt(baseNumLetter.length());
ch = baseNumLetter.charAt(dot) + "";
sBuffer.append(ch);
//正向旋转
graphics.rotate(degree * Math.PI / 180, x, 45);
graphics.drawString(ch, x, 45);
//反向旋转
graphics.rotate(-degree * Math.PI / 180, x, 45);
x += 48;
}
//画干扰线
for (int i = 0; i < 6; i++) {
// 设置随机颜色
graphics.setColor(getRandomColor());
// 随机画线
graphics.drawLine(random.nextInt(width), random.nextInt(height),
random.nextInt(width), random.nextInt(height));
}
//添加噪点
for (int i = 0; i < 30; i++) {
int x1 = random.nextInt(width);
int y1 = random.nextInt(height);
graphics.setColor(getRandomColor());
graphics.fillRect(x1, y1, 2, 2);
}
return sBuffer.toString();
}
/**
* 随机取色
*/
private static Color getRandomColor() {
Random ran = new Random();
Color color = new Color(ran.nextInt(256),
ran.nextInt(256), ran.nextInt(256));
return color;
}
}
运行结果
