JSP生成验证码

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image.jsp

<%@
page
language="java"
import="java.util.*"
pageEncoding="gb2312"%>

<%@
page
contentType="image/jpeg"
import="java.awt.*,

java.awt.image.*,java.util.*,javax.imageio.*"
%>

<%!

//
随机颜色

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();

//
设置页面不缓存

response.setHeader("Pragma","No-cache");

response.setHeader("Cache-Control","no-cache");

response.setDateHeader("Expires",
0);

//
定义图片的长度和高度

int
width=60,
height=20;

//
在内存中创建图像

BufferedImage
image
=
new
BufferedImage(width,
height,
BufferedImage.TYPE_INT_RGB);

Graphics
g
=
image.getGraphics();

//
随机类

Random
random
=
new
Random();

//
设置背景

g.setColor(getRandColor(200,250));

g.fillRect(0,
0,
width,
height);

//
字体定义

g.setFont(new
Font("Times
 New Roman",Font.PLAIN,18));

g.setColor(getRandColor(160,200));

//
用线条画背景

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);

}

//
生成验证码随机数

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("code",sRand);

g.dispose();

//
输出图像

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

%>

login.jsp

XHTML

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<%@
page
contentType="text/html;
 charset=gb2312"
language="java"
import="java.sql.*"
errorPage=""
%>

<html>

<head>

<title>登录页面</title>

<script
language="javascript">

function
loadimage(){

document.getElementById("randImage").src
=
"image.jsp?"+Math.random();

}

</script>

</head>

<body>

<form
action="check.jsp"
method="post"
name="loginForm">

<td
width="118"
height="22"valign="middle"
align="center"><input
type="text"
name="code"
size="15"></td>

<td
width="138"
align="center"><a
href="javascript:loadimage();"><img
name="randImage"
id="randImage"
src="image.jsp"
width="60"
height="20"valign="middle"
border="1"></a>点击图片刷新

<input
type="submit"
name="login"
value="提交"></td>

</form>

</body>

</html>

check.jsp

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<%@
page
contentType="text/html;
 charset=gb2312"
language="java"
%>

<%

String
rand
=
(String)session.getAttribute("code");

String
input
=
request.getParameter("code");

if(rand.equals(input)){

out.print("<script>alert('验证成功');</script>");

}
else{

out.print("<script>alert('验证失败');location.href='login.jsp';</script>");

}

%>