Java后台代码（CheckCodeServlet.java）
package web;
import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.io.OutputStream;
import java.io.PrintWriter;
import java.util.Random;
import javax.imageio.ImageIO;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class CheckCodeServlet extends HttpServlet {
/*
* 返回一张动态图片
*
*/
public void service(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
response.setContentType("text/jpeg");
//获取字节流
OutputStream os=response.getOutputStream();
//图片映射区，理解成画板就行，画验证码
// BufferedImage image=new BufferedImage(width,height,imageType);
BufferedImage image=new BufferedImage(80,40,BufferedImage.TYPE_INT_RGB);
//画笔
Graphics g=image.getGraphics();
//添加背景颜色（随机）
Random r=new Random();
g.setColor(new Color(r.nextInt(256),r.nextInt(256),r.nextInt(256)));//Color(red,green,blue);rgb格式的颜色设置
g.fillRect(0, 0, 80, 40);//画矩形区域
//画字符串
g.setColor(Color.black);//设置验证码的颜色
g.setFont(new Font(null,Font.BOLD,20));//设置验证码的字体 Font(字体,样式,大小)
String num=getNum(5);//调入验证码
g.drawString(num, 5, 30);//(字符串内容,X坐标,Y坐标)
//划线，干扰机器人识别验证码
for(int i=0;i<6;i++){
//画6条线
g.setColor(new Color(r.nextInt(256),r.nextInt(256),r.nextInt(256)));//设置线的颜色
g.drawLine(r.nextInt(80),r.nextInt(80),r.nextInt(80),r.nextInt(80));//g.drawLine(起点X坐标,起点Y坐标,终点X坐标,终点Y坐标);
}
//压缩 传输（画出的图片比较大，需要压缩，画出的是24位图）
ImageIO.write(image, "jpeg", os);
}
//返回正确的验证码
//length：验证码的长度
public String getNum(int length){
String str="ABCDEFGHIJKLMNOPQRSTUVWXYZ123456789";//常量，为了根据长度挑出随机的验证码
Random r=new Random();
StringBuffer sf=new StringBuffer();
for(int i=0;i<length;i++){
int index=r.nextInt(str.length());//取str的下标
char c=str.charAt(index);//根据下标取字符
sf.append(c);//字符放入字符串缓冲区
}
return sf.toString();//转换成字符串返回
}
}
web.xml配置文件
<servlet>
<servlet-name>CheckCodeServlet</servlet-name>
<servlet-class>web.CheckCodeServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>CheckCodeServlet</servlet-name>
<url-pattern>/checkCode</url-pattern>
</servlet-mapping>
text.jsp
<%@ page language="java" contentType="text/html; charset=utf-8"
pageEncoding="utf-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<title>Insert title here</title>
</head>
<body>
<input >
图片：<img id="num" src="checkCode"><a href="javascript:;" onclick="document.getElementById(‘num‘).src=‘checkCode?‘+new Date().getTime();">换一张</a>
</body>
</html>
原文地址：https://www.cnblogs.com/yingyigongzi/p/9167101.html
时间： 2024-11-01 13:51:12