jsp实现图片验证码 -

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jsp实现图片验证码

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jsp 图片验证码

1、html页面：
<%@ page language="java" contentType="text/html; charset=gbk"
pageEncoding="gbk"%>
<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 name="loginForm" action="login" method="post">
<table border="1" align="center">
<tr>
<td>验证码：</td>
<td><input type="text" name="checode" /> <img
alt="code..." name="randImage" id="randImage" src="image.jsp"></td>
</tr>
<tr>
<td colspan="2" align="center"><a href="javascript:loadimage();"><font
class=pt95>看不清点我</font></a></td>
</tr>
<tr>
<td colspan="2">
<center><input type="submit" value="登录" />   <input
type="button" value="返回" onclick="location.href='/xkxt/index.jsp'" /></center>
</td>
</tr>
</table>
</form>
</body>
</html>
2、image.jsp
<%@ page contentType="image/jpeg" pageEncoding="gbk" 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 rand = request.getParameter("rand");
//rand = rand.substring(0,rand.indexOf("."));
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

    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();
%>
3、servlet中验证
String checode = request.getParameter("checode");
String rand = (String) request.getSession().getAttribute("rand");
if(checode.equals(rand)){
rd = request.getRequestDispatcher(success);
rd.forward(request, response);
} else {
PrintWriter out = response.getWriter();
out.println("<font size=4 color='red'>验证码不正确，请重新登录！</font>");
rd = request.getRequestDispatcher(failure);
rd.forward(request, response);
}

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