Jsp生成頁面驗證碼的方法[附代碼]

%@ page contentType="image/jpeg" import="java.awt.*,
java.awt.image.*,java.util.*,javax.imageio.*" %>
%!
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);
}
%>
%
out.clear();//這句針對resin服務器，如果是tomacat可以不要這句
response.setHeader("Pragma","No-cache");
response.setHeader("Cache-Control","no-cache");
response.setDateHeader("Expires", 0);
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;i155;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;i4;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)));
g.drawString(rand,13*i+6,16);
}
// 將認證碼存入SESSION
session.setAttribute("rand",sRand);
g.dispose();
ImageIO.write(image, "JPEG", response.getOutputStream());
%>

%@ page contentType="text/html;charset=gbk" %>
%@ page language="java" import="java.sql.*" errorPage="" %>
html>
head>
meta http-equiv="Content-Type" content="text/html; charset=gb2312">
title>用戶登錄/title>
script language="javascript">
function loadimage(){
document.getElementById("randImage").src = "image.jsp?"+Math.random();
}
/script>
/head>
body>
table width="256" border="0" cellpadding="0" cellspacing="0">
!--DWLayoutTable-->
form action="validate.jsp" method="post" name="loginForm">
tr>
td width="118" height="22" valign="middle" align="center">input type="text" name="rand" size="15">/td>
td width="138" valign="middle" align="center">img alt="code..." name="randImage" id="randImage" src="image.jsp" width="60" height="20" border="1" align="absmiddle">/td>
/tr>
tr>
td height="36" colspan="2" align="center" valign="middle">a href="javascript:loadimage();">font class=pt95>看不清點我/font>/a>/td>
/tr>
tr>
td height="36" colspan="2" align="center" valign="middle">input type="submit" name="login" value="提交">/td>
/tr>
/form>
/table>
/body>
/html>

%@ page contentType="text/html; charset=gb2312" language="java" import="java.sql.*" errorPage="" %>
%
String rand = (String)session.getAttribute("rand");
String input = request.getParameter("rand");
if(rand.equals(input)){
out.print("script>alert('驗證通過！');/script>");
} else{
out.print("script>alert('請輸入正確的驗證碼！');location.href='login.jsp';/script>");
}
%>