JSP图片验证码

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2011-12 ( 4)
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<%@ page contentType="text/html;charset=UTF-8" pageEncoding="UTF-8"%>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>用户登录</title>
<script type="text/javascript">
	function loadimage() {
		document.getElementById("randImage").src = "image.jsp?" + Math.random();
	}
</script>
</head>
<body>
	<table>
		<form action="validate.jsp" method="post" name="loginForm">
			<tr>
				<td><input type="text" name="rand" size="15"></td>
				<td><img name="randImage" id="randImage" src="image.jsp"
					width="60" height="20" border="1" align="absmiddle"></td>
			</tr>
			<tr>
				<td><a href="javascript:loadimage();">看不清点我</a></td>
			</tr>
			<tr>
				<td><input type="submit" name="login" value="提交"></td>
			</tr>
		</form>
	</table>
</body>
</html>

图片生成页

<%@ page contentType="image/jpeg"
	import="java.io.*,java.awt.*,java.awt.image.*,java.util.*,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);
	}%>
<%
	//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();
	OutputStream os = response.getOutputStream();
	ImageIO.write(image, "JPEG", os);
	os.flush();
	os.close();
	os=null;
	response.flushBuffer();
	out.clear();
	out = pageContext.pushBody();
%>

校验页：

<%@ page language="java" contentType="text/html; charset=UTF-8"
	pageEncoding="UTF-8"%>
<%
	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>");
	}
%>

参考：http://blog.csdn.net/iron_wang/article/details/4204672

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