首先给你个验证码模板，文件名为Num.jsp
<%@ page pageEncoding = "gbk" contentType="image/jpeg" import = "javax.imageio.*,java.util.*,java.awt.image.*,java.awt.*" %>
window.self.location.reload(true);
<%!
//在此处 获取并生成随机颜色
Color getRandColor(Random random, int ff, int cc) {
if (ff > 255)
ff = 255;
if (cc > 255)
cc = 255;
int r = ff + random.nextInt(cc - ff);
int g = ff + random.nextInt(cc - ff);
int b = ff + random.nextInt(cc - ff);
return new Color(r, g, b);
} %>
<%
response.setHeader("Pragma","No-cache");
response.setHeader("Cache-Control","no-cache");
response.setDateHeader("Expires", 0);
int width=60; //定义验证码图片的长度
int height=20; //定义验证码图片的宽度
BufferedImage image = new BufferedImage(width,height,BufferedImage.TYPE_INT_RGB);
Graphics g = image.getGraphics();
Random random = new Random();
g.setColor(getRandColor(random,200,250));
g.fillRect(0, 0, width, height);
g.setFont(new Font("Times New Roman",Font.PLAIN,18));
//定义字体形式
g.setColor(getRandColor(random,160,200));
for (int i=0;i<155;i++)
{
int i_x = random.nextInt(width);
int i_y = random.nextInt(height);
int i_xl = random.nextInt(12);
int i_yl = random.nextInt(12);
g.drawLine(i_x,i_y,i_x+i_xl,i_y+i_yl);
}
//用线条画背景
String s_Rand="";
for (int i=0;i<4;i++)
{
String rand=String.valueOf(random.nextInt(10));
s_Rand+=rand;
g.setColor(new Color(20+random.nextInt(110),20+random.nextInt(110),20+random.nextInt(110)));
g.drawString(rand,13*i+6,16);
}
//产生4位随机码
session.setAttribute("rand",s_Rand);
//将验证码存入Session中
g.dispose();
ImageIO.write(image, "JPEG", response.getOutputStream());
//输出验证图片
out.clear();
out = pageContext.pushBody();
%>
重要的是如何调用这个验证码，而且单击验证码让它自动换一张，看下面代码，文件名为test.jsp
<%@ page language="java" import="java.util.*" pageEncoding="gbk"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<base href="<%=basePath%>">
<title>My JSP 'index.jsp' starting page</title>
<meta http-equiv="pragma" content="no-cache">
<meta http-equiv="cache-control" content="no-cache">
<meta http-equiv="expires" content="0">
<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
<meta http-equiv="description" content="This is my page">
<script type="text/javascript">
function change()
{
var img=document.getElementById("code");
img.src="Num.jsp?date="+new Date();//此处很重要，不加后面的就不会变
}
</script>
</head>
<body>
<center>
<form id="dForm" method=post action="">
用户名:<input name="username"><br>
密 码:<input type="password" name="password"><br>
校验码:<input id="check" size="10">
<img id="code" border=0 src="Num.jsp" onclick="change()"/><br>
<input type="reset" value="重置">
<input type="submit" value="提交">
</form>
</center>
</body>
</html>