验证码

验证servlet：

 package edu.yale.its.tp.cas.servlet;

import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics2D;
import java.awt.image.BufferedImage;
import java.util.Random;

import javax.imageio.ImageIO;
import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

/**
 * 生成随机验证码
 * 
 * @author wulihai
 * 
 */
public class ValidateCodeServlet extends HttpServlet {

	private static final long serialVersionUID = 1L;

	// 验证码图片的宽度。
	private int width = 100;
	// 验证码图片的高度。
	private int height = 30;
	// 验证码字符个数
	private int codeCount = 5;
   
	private int x = 0;
	// 字体高度
	private int fontHeight;
	private int codeY;

	char[] codeSequence = { 'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J',
			'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W',
			'X', 'Y', 'Z', '0', '1', '2', '3', '4', '5', '6', '7', '8', '9' };

	/**
	 * 初始化验证图片属性
	 */
	public void init() throws ServletException {
		// 从web.xml中获取初始信息
		// 宽度
		String strWidth = this.getInitParameter("width");
		// 高度
		String strHeight = this.getInitParameter("height");
		// 字符个数
		String strCodeCount = this.getInitParameter("codeCount");

		// 将配置的信息转换成数值
		try {
			if (strWidth != null && strWidth.length() != 0) {
				width = Integer.parseInt(strWidth);
			}
			if (strHeight != null && strHeight.length() != 0) {
				height = Integer.parseInt(strHeight);
			}
			if (strCodeCount != null && strCodeCount.length() != 0) {
				codeCount = Integer.parseInt(strCodeCount);
			}
		} catch (NumberFormatException e) {
		}

		x = width / (codeCount+1);
		fontHeight = height - 2;
		codeY = height - 4;

	}
	
	/**
	 * 背景颜色的设置
	 * @param fc
	 * @param bc
	 * @return
	 */
	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);
	}

	/**
	 * 服务类
	 */
	protected void service(HttpServletRequest req, HttpServletResponse resp)
			throws ServletException, java.io.IOException {

		// 定义图像buffer
		BufferedImage buffImg = new BufferedImage(width, height,
				BufferedImage.TYPE_INT_RGB);
		Graphics2D g = buffImg.createGraphics();

		// 创建一个随机数生成器类
		Random random = new Random();

		// 将图像填充为白色
		g.setColor(Color.WHITE);
		g.fillRect(0, 0, width, height);

		
		//===============创建字体,字体的大小应该根据图片的高度来定=============//
		Font font = new Font("Tahoma, Arial", Font.BOLD, fontHeight);
		// 设置字体。
		g.setFont(font);

		
		//设置边框颜色
		g.setColor(Color.BLACK);
		g.drawRect(-1, -1, width+1, height+1 );

		// 随机产生160条干扰线，使图象中的认证码不易被其它程序探测到。
		g.setColor(Color.WHITE);
		//g.setColor(getRandColor(175, 255));
		for (int i = 0; i < 160; 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);
		}

		// randomCode用于保存随机产生的验证码，以便用户登录后进行验证。
		StringBuffer randomCode = new StringBuffer();
		int red = 0, green = 0, blue = 0;

		// 随机产生codeCount数字的验证码。
		for (int i = 0; i < codeCount; i++) {
			// 得到随机产生的验证码数字。
			String strRand = String.valueOf(codeSequence[random.nextInt(36)]);
			// 产生随机的颜色分量来构造颜色值，这样输出的每位数字的颜色值都将不同。
			red = random.nextInt(255);
			green = random.nextInt(255);
			blue = random.nextInt(255);

			// 用随机产生的颜色将验证码绘制到图像中。
			g.setColor(new Color(red, green, blue));
			//指定位置输出每个验证码
			g.drawString(strRand, i*x+i+3, codeY);
			// 将产生的四个随机数组合在一起。
			randomCode.append(strRand);
		}
		
		// 将四位数字的验证码保存到Session中。
		HttpSession session = req.getSession();
		session.setAttribute("validateCode", randomCode.toString());

		// 禁止图像缓存。
		resp.setHeader("Pragma", "no-cache");
		resp.setHeader("Cache-Control", "no-cache");
		resp.setDateHeader("Expires", 0);

		resp.setContentType("image/jpeg");

		// 将图像输出到Servlet输出流中。
		ServletOutputStream sos = resp.getOutputStream();
		ImageIO.write(buffImg, "jpeg", sos);
		sos.close();
	}

}

 

index.jsp

<%@ page contentType="text/html;charset=gb2312"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<%
 String command=request.getParameter("command");
 String rand=request.getParameter("rand");
 String rand2=(String)session.getAttribute("validateCode");
 if(!"".equals(command) && "check".equals(command)){
   if(!rand.equals(rand2)){
    out.print("验证码错误！");
   }else{
    
    //===调用业务逻辑类，查询该用户名密码等是否正确===//
     
    //===将用户信息放到session中====//
	//session.setAttribute("user", user);
     response.sendRedirect("success.jsp");
   }
   
 }


 %>
<html>
	<head>
		<title>认证码输入页面</title>
		<meta http-equiv="Content-Type" content="text/html; charset=gb2312">
		<META HTTP-EQUIV="Pragma" CONTENT="no-cache">
		<META HTTP-EQUIV="Cache-Control" CONTENT="no-cache">
		<META HTTP-EQUIV="Expires" CONTENT="0">
	</head>
	<body>
		<form method=post action="index.jsp">
		<input name="command" value="check" type="hidden"/>
			<table>
				<tr>
					<td align=left>
						系统产生的认证码：
					</td>
					<td>
						<img border=0 src="validateCodeServlet">
					</td>
				</tr>
				<tr>
					<td align=left>
						输入上面的认证码：
					</td>
					<td>
						<input type=text name=rand maxlength=10 value="">
					</td>
				</tr>
				<tr>
					<td colspan=2 align=center>
						<input type=submit value="提交检测">
					</td>
				</tr>
			</table>
		</form>
	</body>
</html>

success.jsp

<%@ page contentType="text/html; charset=gb2312" language="java"
	import="java.sql.*" errorPage=""%>
<html>
	<head>
		<title>认证码验证页面</title>
		<meta http-equiv="Content-Type" content="text/html; charset=gb2312">
		<META HTTP-EQUIV="Pragma" CONTENT="no-cache">
		<META HTTP-EQUIV="Cache-Control" CONTENT="no-cache">
		<META HTTP-EQUIV="Expires" CONTENT="0">
	</head>

	<body>
	验证成功！
	</body>
</html>

web.xml

     <!--add by wulihai on 2009-07-06-->
   <servlet>
		<servlet-name>ValidateCodeServlet</servlet-name>
		<servlet-class>edu.yale.its.tp.cas.servlet.ValidateCodeServlet</servlet-class>
     <init-param>
			<param-name>width</param-name>
			<param-value>55</param-value>
		</init-param>
		<init-param>
			<param-name>height</param-name>
			<param-value>17</param-value>
		</init-param>
		<init-param>
			<param-name>codeCount</param-name>
			<param-value>4</param-value>
		</init-param>
	 </servlet>

	<servlet-mapping>
		<servlet-name>ValidateCodeServlet</servlet-name>
		<url-pattern>/validateCodeServlet</url-pattern>
	</servlet-mapping>