服务器端生成的验证码技术(Java)
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2022-05-19 19:25:10
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准备工作
(1) 以Myeclipse 2017为例，创建Web Project并建包
(2) src源代码文件中创建一个Servlet**(注意：这里为other…->Web->Servlet)**
(3)删除不需要的代码并用doGet调用doPost函数（代码写在一个函数中）
import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class CheckCode extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doPost(request, response);
}
public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
}
}验证码的Servlet类
import java.awt.Color;
import java.awt.Graphics2D;
import java.awt.image.BufferedImage;
import java.io.IOException;
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 CheckCode extends HttpServlet {
//验证码图片大小
public final static int IMG_WIDTH = 50;
public final static int IMG_HEIGHT = 30;
//随机验证码集合
public final static String CHECK_STRING = "QWERTYUIOPASDFGHJKLZXCVBNMqwertyuiopasdfghjklzxcvbnm1234567890";
//验证码个数
public final static int CHECK_NUM = 4;
public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doPost(request, response);
}
public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//创建一个图片缓冲，图片类型为RGB
BufferedImage img = new BufferedImage(IMG_WIDTH, IMG_HEIGHT, BufferedImage.TYPE_INT_RGB);
//拿到图片的画笔
Graphics2D g2d = (Graphics2D)img.getGraphics();
//将缓冲图片默认的黑色改为白色
g2d.fillRect(0, 0, IMG_WIDTH, IMG_HEIGHT);
//画出验证码
for(int i=0; i<CHECK_NUM; i++){
int randomNum = new Random().nextInt(CHECK_STRING.length());
//根据随机数将字母强制转换为字符串
String randomChar = String.valueOf(CHECK_STRING.charAt(randomNum));
//随机颜色
RandomColor(g2d);
//画出一个验证码
g2d.drawString(randomChar, 5 + (15 * i), 15);
}
/**
* 对验证码增加干扰,可以是点也可以是线等
*/
for(int i=0; i<4; i++){
//随机产生划线坐标
int x1 = new Random().nextInt(IMG_WIDTH);
int y1 = new Random().nextInt(IMG_HEIGHT);
int x2 = new Random().nextInt(IMG_WIDTH);
int y2 = new Random().nextInt(IMG_WIDTH);
RandomColor(g2d);
g2d.drawLine(x1, y1, x2, y2);
}
//向客户端发送jpg图片
ImageIO.write(img, "jpg", response.getOutputStream());
}
/**
* 设置画笔颜色为随机颜色
* @param g2d
*/
public void RandomColor(Graphics2D g2d){
//RGB三色参数
int r = new Random().nextInt(255);
int g = new Random().nextInt(255);
int b = new Random().nextInt(255);
//设置颜色
g2d.setColor(new Color(r, g, b));
}
}
jsp页面
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<base href="<%=basePath%>">
<title>验证码</title>
<meta http-equiv="pragma" content="no-cache">
<meta http-equiv="cache-control" content="no-cache">
<meta http-equiv="expires" content="0">
<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
<meta http-equiv="description" content="验证码">
<link rel="stylesheet" type="text/css" href="styles.css">
</head>
<body>
<div style="color: red">没人要的登陆界面</div>
<form action="#" method="post">
账号 <input name="username" type="text" value=""/><br>
密码 <input name="password" type="text" value=""/><br>
验证码 <input name="checknum" type="text"><img src="servlet/CheckCode" onclick="this.src='servlet/CheckCode?' + Math.random();"> <br>
<input type="submit" value="确认"><input type="reset" value="重新输入">
</form>
</body>
</html>打开游览器输入路径>效果如下
路径格式http://localhost:8080/CheckCode/index.jsp
http+本机地址+tomcat默认端口号+工程文件名+ 页面名称（也可以为Servlet类路径）