随机产生验证码

最新推荐文章于 2025-08-11 19:52:03 发布

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最新推荐文章于 2025-08-11 19:52:03 发布

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分类专栏： JavaEE 文章标签： random string input image javascript servlet

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本文介绍了一个简单的验证码生成和验证过程，包括使用Java Servlet创建动态验证码图片，并通过客户端表单进行输入验证。

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1、servlet

import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.util.Random;
import javax.imageio.ImageIO;
import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

public class AuthImg extends HttpServlet {
    protected void processRequest(HttpServletRequest request, HttpServletResponse response)
    throws ServletException, IOException {

        response.setContentType("image/jpeg");
        response.setHeader("Pragma","No-cache");
        response.setHeader("Cache-Control","no-cache");
        response.setDateHeader("Expires", 0);      
        HttpSession session=request.getSession();
        int width=60, height=20;
        BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);

        Graphics g = image.getGraphics();

        Random random = new Random();

        g.setColor(getRandColor(200,250));
        g.fillRect(0, 0, width, height);
        g.setFont(new Font("Times New Roman",Font.PLAIN,18));
        g.setColor(getRandColor(160,200));
        for (int i=0;i<155;i++) {
            int x = random.nextInt(width);
            int y = random.nextInt(height);
            int xl = random.nextInt(12);
            int yl = random.nextInt(12);
            g.drawLine(x,y,x+xl,y+yl);
        }

        String sRand="";
        for (int i=0;i<4;i++){
            String rand=String.valueOf(random.nextInt(10));
            sRand+=rand;
            g.setColor(new Color(20+random.nextInt(110),20+random.nextInt(110),20+random.nextInt(110)));
//���ú����4����ɫ��ͬ����������Ϊ����̫�ӽ�����ֻ��ֱ�����
            g.drawString(rand,13*i+6,16);
        }
        session.setAttribute("rand",sRand);
        g.dispose();
        ServletOutputStream responseOutputStream =response.getOutputStream();

        ImageIO.write(image, "JPEG", responseOutputStream);
        responseOutputStream.flush();
        responseOutputStream.close();
    }
    Color getRandColor(int fc,int bc){
        Random random = new Random();
        if(fc>255) fc=255;
        if(bc>255) bc=255;
        int r=fc+random.nextInt(bc-fc);
        int g=fc+random.nextInt(bc-fc);
        int b=fc+random.nextInt(bc-fc);
        return new Color(r,g,b);
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response)

    throws ServletException, IOException {

        processRequest(request, response);

    }

    protected void doPost(HttpServletRequest request, HttpServletResponse response)

    throws ServletException, IOException {

        processRequest(request, response);

    }

    public String getServletInfo() {

        return "Short description";

    }

}

2、web.xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.4" 
	xmlns="http://java.sun.com/xml/ns/j2ee" 
	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
	xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee 
	http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd">
   <servlet>
        <servlet-name>img</servlet-name>
        <servlet-class>AuthImg</servlet-class>
    </servlet>

    <servlet-mapping>
       <servlet-name>img</servlet-name>
       <url-pattern>/authImg</url-pattern>
    </servlet-mapping>

  <welcome-file-list>
    <welcome-file>index.jsp</welcome-file>
  </welcome-file-list>
</web-app>

3、a.jsp

<%@ page contentType="text/html;charset=UTF-8"%>

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">

<html>
 <head>
  <title>认证码输入页面</title>
  <meta http-equiv="Content-Type" content="text/html; charset=gb2312">
  <META HTTP-EQUIV="Pragma" CONTENT="no-cache">
  <META HTTP-EQUIV="Cache-Control" CONTENT="no-cache">
  <META HTTP-EQUIV="Expires" CONTENT="0">
  <script language="JavaScript">
          function myrefresh()
          {
            window.location.reload();
          }
  </script>
 </head>
 <body>
  <form method=post action="b.jsp">
   <table>
    <tr>
     <td align=left>
      系统产生的认证码：
     </td>
     <td>
      <img border=0 src="authImg">  <input type="button" value="看不清，在换一张" onclick="myrefresh()">
     </td>
    </tr>
    <tr>
     <td align=left>
      输入上面的认证码：
     </td>
     <td>
      <input type=text name=rand maxlength=4 value="">
     </td>
    </tr>
    <tr>
     <td colspan=2 align=center>
      <input type=submit value="提交检测">
     </td>
    </tr>
    </table>

   </form>

 </body>

4、 b.jsp

<%@ page contentType="text/html; charset=gb2312" language="java" import="java.sql.*" errorPage="" %>
<html>
<head>
<title>认证码验证页面</title>
<meta http-equiv="Content-Type" content="text/html; charset=gb2312">
<META HTTP-EQUIV="Pragma" CONTENT="no-cache">
<META HTTP-EQUIV="Cache-Control" CONTENT="no-cache">
<META HTTP-EQUIV="Expires" CONTENT="0">
</head>
<body>
<%
String rand = (String)session.getAttribute("rand");
String input = request.getParameter("rand");
%>
系统产生的认证码为： <%= rand %><br>
您输入的认证码为： <%= input %><br>
<br>
<%
  if (rand.equals(input)) {
%>
<font color=green>输入相同，认证成功！</font>
<%
  } else {
%>
<font color=red>输入不同，认证失败！</font>
<%
  }
%>
</body>
</html>