验证码 一篇通

1.思路:

页面上的验证码图片是servlet,采用jquery实现异步校验信息

 

2.所用到的文件

VerifyCodeServlet.java   --用于生成图片的servlet

ResultServlet.java          --用于校验验证码正确性的servlet

verifyCode.js                  --校验的js文件

jquery.js                         --jquery包里的源文件

verifyCode.jsp                --页面

 

3.代码

VerifyCodeServlet.java

 

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;

public class VerifyCodeServlet extends HttpServlet {

	// 验证码图片的宽度。
	private int width = 60;

	// 验证码图片的高度。
	private int height = 20;

	// 验证码字符个数
	private int codeCount = 4;

	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;

	}

	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, 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.BLACK);
		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, 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();
	}

}

 

 

ResultServlet.java

 

import java.io.IOException;
import java.io.PrintWriter;

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

public class ResultServlet extends HttpServlet {

	/**
	 * The doGet method of the servlet. <br>
	 *
	 * This method is called when a form has its tag value method equals to get.
	 * 
	 * @param request the request send by the client to the server
	 * @param response the response send by the server to the client
	 * @throws ServletException if an error occurred
	 * @throws IOException if an error occurred
	 */
	public void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {

		doPost(request, response);
	}

	/**
	 * The doPost method of the servlet. <br>
	 *
	 * This method is called when a form has its tag value method equals to post.
	 * 
	 * @param request the request send by the client to the server
	 * @param response the response send by the server to the client
	 * @throws ServletException if an error occurred
	 * @throws IOException if an error occurred
	 */
	public void doPost(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {

		response.setContentType("text/html;charset=utf-8");
		String validateC = (String) request.getSession().getAttribute("validateCode");
		String veryCode = request.getParameter("c");
		PrintWriter out = response.getWriter();
		if(veryCode==null||"".equals(veryCode)){
			out.println("验证码为空");
		}else{
			if(validateC.equals(veryCode)){
				out.println("验证码正确");
			}else{
				out.println("验证码错误");
			}
		}
		out.flush();
		out.close();
	}

}

 

 

verifyCode.js

 

function changeImg(){
	var imgSrc = $("#imgObj");
	var src = imgSrc.attr("src");
	imgSrc.attr("src",chgUrl(src));
}
//时间戳
//为了使每次生成图片不一致，即不让浏览器读缓存，所以需要加上时间戳
function chgUrl(url){
	var timestamp = (new Date()).valueOf();
	url = url.substring(0,17);
	if((url.indexOf("&")>=0)){
		url = url + "×tamp=" + timestamp;
	}else{
		url = url + "?timestamp=" + timestamp;
	}
	return url;
}

function isRightCode(){
	var code = $("#veryCode").attr("value");
	code = "c=" + code;
	$.ajax({
		type:"POST",
		url:"resultServlet",
		data:code,
		success:callback
	});
}

function callback(data){
	$("#info").html(data);
}

 

 

verifyCode.jsp

 

<%@ page language="java" contentType="text/html; charset=UTF-8"
	pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
	<head>
		<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
		<script type="text/javascript" src="js/verifyCode.js"></script>
		<script type="text/javascript" src="js/jquery.js"></script>
		<title>test verify code</title>
	</head>
	<body>
		<input id="veryCode" name="veryCode" type="text"/>
		<img id="imgObj" alt="" src="verifyCodeServlet"/>
		<a href="#" onclick="changeImg()">换一张</a>
		<input type="button" value="验证" onclick="isRightCode()"/>
		<div id="info"></div>
	</body>
</html>

 

 

 

 

关键点有个错误。

ResultServlet.java 的第44行：
     if(veryCode==null||"".equals(veryCode)){ 

这种直接读取session，然后用equals方法判断的方式不能真正避免Robot的轰炸式提交。因为你的veryCode直接暴露在session里了，好的Robot一样可以读到。

值得称赞的是 VerifyCodeServlet.java的代码注释写的非常不错。简洁明了。

 

servlet不用在web.xml中配置吗

 

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