image.jsp是生成的随机数
test.jsp是调用image.jsp文件
image.jsp
<%@ page contentType="image/jpeg" import="java.awt.*,java.awt.image.*,java.util.*,javax.imageio.*" %>
<%!
Color getRandColor(int fc,int bc){//给定范围获得随机颜色
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);
}
%>
<%
//设置页面不缓存
response.setHeader("Pragma","No-cache");
response.setHeader("Cache-Control","no-cache");
response.setDateHeader("Expires", 0);
// 在内存中创建图象
int width=60, height=20;
BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
// 获取图形上下文
Graphics g = image.getGraphics();
//生成随机类
Random random = new Random();
// 设定背景色
g.setColor(getRandColor(200,250));
g.fillRect(0, 0, width, height);
//设定字体
g.setFont(new Font("Times New Roman",Font.PLAIN,18));
//画边框
//g.setColor(new Color());
//g.drawRect(0,0,width-1,height-1);
// 随机产生155条干扰线，使图象中的认证码不易被其它程序探测到
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);
}
// 取随机产生的认证码(4位数字)
String sRand="";
for (int i=0;i<4;i++){
String rand=String.valueOf(random.nextInt(10));
sRand+=rand;
// 将认证码显示到图象中
g.setColor(new Color(20+random.nextInt(110),20+random.nextInt(110),20+random.nextInt(110)));//调用函数出来的颜色相同，可能是因为种子太接近，所以只能直接生成
g.drawString(rand,13*i+6,16);
}
// 将认证码存入SESSION
session.setAttribute("numrand",sRand);
// 图象生效
g.dispose();
// 输出图象到页面
ImageIO.write(image, "JPEG", response.getOutputStream());
out.clear();
out = pageContext.pushBody();
%>
test.jsp
<%@ page language="java" contentType="text/html; charset=utf-8"
pageEncoding="utf-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<meta http-equiv="Pragma" content="no-cache"/>
<meta http-equiv="Cache-Control" content="no-cache, must-revalidate"/>
<meta http-equiv="Expires" content="0"/>
<title>test</title>
<script type="text/javascript">
function check(){
}
//验证码刷新
function reLoadImage(){document.getElementById("valimg").src="image.jsp?r="+ Math.random();}
//注意后面的随机数,去掉则不能刷新
</script>
</head>
<body>
<div>添加后台管理员</div>
<form name="manager" action="bbsmanageradd" method="post" οnsubmit="return check();">
<div>用户名:<input type="text" name="username"></div>
<div>密码:<input type="password" name="password"></div>
<div>
</div>
<div>
</div>
<div>验证码:<input type="text" name="validation"> <img src="image.jsp" title="点击刷新" name="valimg" id="valimg" οnclick="reLoadImage();"> <a href="JavaScript:reLoadImage();" target="_blank" rel="external nofollow" >看不清</a> </div>
<div><input type="submit" value="提交"> <input type="reset" value="重置"> <input type="button" value="返回" οnclick="javascript:window.location.href='bbsmanagershow'"></div>
</form>
</body>
</html>
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