java.awt.image.*,java.util.*,javax.imageio.*" pageEncoding="GBK"%>
<%!
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=0i<155i++)
{
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=0i<4i++){
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("rand",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()
%>
登录页面login.jsp示例代码：<%@ page language="java" import="java.util.*" pageEncoding="utf-8"%>
<%
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 'login.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">
<!--
<link rel="stylesheet" type="text/css" href="styles.css">
-->
</head>
<%
String incode = (String)request.getParameter("code")
String rightcode = (String)session.getAttribute("rCode")
if(incode != null &&rightcode != null){
if(incode.equals(rightcode)){
out.println("验证码输入正确！")
}else{
out.println("验证码输入不正确，请重新输入！")
}
}
%>
<body>
<form action="login.jsp" method="post">
用户名：
<input type="text" name="username"/><br/>
密码：
<input type="password" name="password"/><br/>
验证码：
<img src="number.jsp"/>
<input type="text" name="code"/>
<input type="submit" value="登录"/>
</form>
</body>
</html>
验证码页面number.jsp代码：
<%@ page contentType="image/jpeg" language="java" import="java.util.*,java.awt.*,java.awt.image.*,javax.imageio.*" pageEncoding="utf-8"%>
<%!
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)
}
%>
<%
//设置页面不缓存
response.setHeader("Pragma","no-cache")
response.setHeader("Cache-Control","no-catch")
response.setDateHeader("Expires",0)
//在内存中创建图象
int width = 60
int height = 20
BufferedImage image = new BufferedImage(width,height,BufferedImage.TYPE_INT_RGB)
//创建图象
Graphics g = image.getGraphics()
//生成随机对象
Random random = new Random()
//设置背景色
g.setColor(getRandColor(200,250))
g.fillRect(0,0,width,height)
//设置字体
g.setFont(new Font("Tines Nev Roman",Font.PLAIN,18))
//随机产生干扰线
g.setColor(getRandColor(160,200))
for(int i = 0i <255i++){
int x = random.nextInt(width)
int y = random.nextInt(height)
int xl = random.nextInt(12)
int yl = random.nextInt(12)
}
//随机产生认证码,4位数字
String sRand = ""
for(int i = 0i <4i++){
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)))
g.drawString(rand,13*i+6,16)
}
session.setAttribute("rCode",sRand)
//图像生效
g.dispose()
//输出图像到页面
ImageIO.write(image,"JPEG",response.getOutputStream())
out.clear()
out = pageContext.pushBody()
%>
