动态验证码生成

现在网上有很多在用户登陆或注册的时候为了防止程序攻击，加入了动态验证的技术，一般是让用户输入随即生成的验证码来实现。下面是一个用Servlet生成动态验证码的一个实例，可以根据实际需要进行修改。

 

1，生成动态验证码的Servlet。

package com.xcu.web;

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;

import com.xcu.comm.CM;
import com.xcu.exception.ApplicationException;

public class ValidateCodeServlet extends HttpServlet {

	/**
	 * 序列化版本UID编号
	 */
	private static final long serialVersionUID = -7080388860058814634L;

	/** 验证码图片的宽度 */
	private int width = 60;
	/** 验证码图片的高度 */
	private int height = 25;
	/** 验证码字符个数 */
	private int codeCount = 4;
	// 字符间距
	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");
		System.out.println("--------验证码宽度："+strWidth);
		// 高度
		String strHeight = this.getInitParameter("height");
		System.out.println("--------验证码宽度："+strHeight);
		// 字符个数
		String strCodeCount = this.getInitParameter("codeCount");
		System.out.println("--------验证码宽度："+strCodeCount);

		// 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) {
			// e.printStackTrace();
			throw new ApplicationException("web.xml中配置的验证码生成参数有误,请检查！", e);
		}

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

	}

	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("Fixedsys", Font.PLAIN | Font.BOLD, fontHeight);
		// 设置字体。
		g.setFont(font);

		// 画边框。
		g.setColor(Color.BLACK);
		g.drawRect(0, 0, 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.pink);
		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));
			g.drawString(strRand, (i + 1) * x - 6, 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(CM.VALIDATE_KEY, randomCode.toString());

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

		// 设置响应的类型格式为图片格式
		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();
	}
}

 

2，用户登录验证的Servlet

package com.xcu.web;

import java.io.IOException;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import com.xcu.comm.CM;
import com.xcu.dao.UserDao;
import com.xcu.domain.Users;


public class LoginCheckServlet extends HttpServlet {

	private static final long serialVersionUID = 4621074605453201722L;
	
	public void doGet(HttpServletRequest request, HttpServletResponse response)
	throws ServletException, IOException {
		response.sendRedirect("noright.jsp");
	}
	public void doPost(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {

		request.setCharacterEncoding("utf-8");
		
		String userName = request.getParameter("userName");
		String userPSD = request.getParameter("password");
		String validateCode = request.getParameter("validateCode");
		
		Users user = new Users();
		
		if(userName != null && userName.length()>0 ){
			user.setName(userName);
		}
		if(userPSD != null && userPSD.length()>0 ){
			user.setPsd(userPSD);
		}

		String validateCodeInSession = (String) request.getSession()
				.getAttribute(CM.VALIDATE_KEY);

		request.getSession().removeAttribute(CM.VALIDATE_KEY);
		
		if (validateCodeInSession == null || validateCode == null
				|| !validateCode.equalsIgnoreCase(validateCodeInSession)) {
			request.getSession().setAttribute(CM.ERR_MSG, "验证码错误");
			request.getSession().setAttribute("userName", userName);
			response.sendRedirect("login.jsp");
		} else {
			// 调用后台业务层的方法进行用户名和密码的校验！
			UserDao ud = new UserDao();
			if (ud.validateUser(user)) {
				user = ud.find(user);
				request.getSession().setAttribute("user", user);
				response.sendRedirect("main.jsp");
			} else {
				request.getSession().setAttribute(CM.ERR_MSG, "用户名或者密码错误");
				request.getSession().setAttribute("userName", userName);
				response.sendRedirect("login.jsp");
			}
		}
	}

}

 

 3，实用验证码的的JSP 页面。

<form method="post" action="login.do" name="form1">
															<TABLE cellSpacing=0 cellPadding=0 width=318 border=0>
																<TBODY>
																	<TR>
																		<TD align=left>
																			<font face="黑体"><span class="content_black_bold">用户名</span> 
																			<input type="text" id="userName" name="userName" value="${userName }" style="WIDTH: 200px" maxLength="20" />
																			</font>
																		</TD>
																	</TR>
																	<TR>
																		<TD height=3>
																			<font face="黑体"><img width="1" height="5" border="0" alt="" src="images/spacer.gif"></font>
																		</TD>
																	</TR>
																	<TR>
																		<TD align=left>
																			<font face="黑体"><span class="content_black_bold">密&nbsp;&nbsp;&nbsp;&nbsp;码</span>
																			<INPUT  style="WIDTH: 200px" type="password" maxLength=32 id="password" name="password" minlength="6" />
																			</font>
																		</TD>
																	</TR>
																	<TR>
																		<TD height=3>
																			<font face="黑体"><img width="1" height="5" border="0" alt="" src="images/spacer.gif"></font>
																		</TD>
																	</TR>
																	<TR>
																		<TD align=left valign="middle">
																			<font face="黑体"><span class="content_black_bold">验证码</span>
																			<INPUT  style="WIDTH: 80px" type="text" maxLength=32 id="validateCode" name="validateCode" minlength="6" />
																			</font><img src="validatecode.jpg" name="validateCode"> <a href="javascript:newCode();">看不清？</a>
																		</TD>
																	</TR>
																	<TR>
																		<TD height=3>
																			<font face="黑体"><img width="1" height="5" border="0" alt="" src="images/spacer.gif"></font>
																		</TD>
																	</TR>
																	<TR>
																		<TD height=3>
																			<font face="黑体"><img width="1" height="5" border="0" alt="" src="images/spacer.gif"></font>
																		</TD>
																	</TR>
																	<TR>
																		<TD noWrap align=right>
																			<font face="黑体"><span style="padding-right: 20px;"><input type="submit" value="登  录" onclick="return check();"></span></font>
																		</TD>
																	</TR>
																</TBODY>
															</TABLE>
														</form>

 

4，Web.xml中对生成验证码Servlet的配置映射。

 <servlet>
  <servlet-name>ValidateCodeServlet</servlet-name>
  <servlet-class>com.xcu.web.ValidateCodeServlet</servlet-class>
  <init-param>
   <param-name>width</param-name>
   <param-value>60</param-value>
  </init-param>
  <init-param>
   <param-name>height</param-name>
   <param-value>20</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>/validatecode.jpg</url-pattern>
 </servlet-mapping>

 

 

评论

1 楼 cnyangqi 2010-03-24  

楼主辛苦，确实有用。