生成随机验证码图片的jsp页面

 代码如下：
<%@ 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();//这句针对resin服务器，如果是tomacat可以不要这句
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;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)));
g.drawString(rand,13*i+6,16);
}

// 将认证码存入SESSION
session.setAttribute("rand",sRand);

g.dispose();

ImageIO.write(image, "JPEG", response.getOutputStream());
%>

login.jsp--------------------登录页面，在这里我是提供输入验证码然后提交进行验证
代码如下：
<%@ page language="java" import="java.sql.*" errorPage="" %>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=gb2312">
<title>用户登录</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>看不清点我</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>

validate.jsp-------------用来验证输入的验证码是否正确
代码如下：
<%@ 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('验证通过！');</script>");
} else{
out.print("<script>alert('请输入正确的验证码！');location.href='login.jsp';</script>");
}
%>

以上这三个jsp页面放在和WEB-INF相同的目录下，如果你放在不同的文件夹下，那么里面相关页面的路径你就要自己改了。
以上代码测试成功，如有问题请及时和我联系。
我的MSN是 congbailing_914@hotmail.com