我要评论代码如下：
复制代码 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());
%>
logic.jsp--------------------------------登陆页面，在这里提供输入验证码然后提交并验证
代码如下：
复制代码 代码如下:
<%@ 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：
复制代码 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>");
}
%>
以上三个jsp页面放在和web-inf同级目录下，如果你放在不同的文件夹下，那么里面相关页面的路径自己稍作更改就可以了。
友情提示：tomcat5以下版本会出现异常
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