随机产生验证码

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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>