验证码概述

为什么使用验证码？

　　验证码（CAPTCHA）是一种全自动程序。主要是为了区分“进行操作的是不是人”。如果没有验证码机制，将会导致以下的问题:

对特定网站不断进行登录，破解密码；对某个网站创建账户；对某个网站提交垃圾数据（灌水贴）；对某个网站进行刷票。

 

使用Servlet实现验证码

　　一个验证码包含两个部分：图片和输入框。

1 <script type="text/javascript"> 2 function reloadCode(){ 3 var time = new Date(); 4 // 给URL传递参数可以清空浏览器的缓存，让浏览器认为这是一个新的请求 5 document.getElementById('safecode').src = '<%=request.getContextPath()%>/servlet/ImageServlet?d=' + time; 6 } 7 </script> 8 9 <form action="<%=request.getContextPath()%>/servlet/ValidateImageServlet"method="post"> 10 验证码：<img src="<%=request.getContextPath()%>/servlet/ImageServlet" alt="验证码" id="safecode"> 11 <input type="text" id="verifyCode" name="verifyCode" size="6" /> 12 <a href="javascript:reloadCode();">看不清楚</a><br> 13 <input type="submit" value="登录" /> 14 </form>

　　我们用ImageServlet实时生成图片。生成图片所需要的步骤如下：

1 定义BufferedImage对象 2 获得Graphics对象 3 听过Random类产生随机验证码信息 4 使用Graphics绘制图片 5 记录验证码信息到session中 6 使用ImageIO输出图片

　　检验验证码是否正确：ValidateImageServlet：

1 获取页面的验证码 2 获取session中保存的验证码 3 比较验证码 4 返回校验结果

　　验证的流程如下：

　　生成验证码的ImageServlet：

1 private static Random r = new Random(); 2 private static char[] chs = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789".toCharArray(); 3 private static final int NUMBER_OF_CHS = 4; 4 private static final int IMG_WIDTH = 65; 5 private static final int IMG_HEIGHT = 25; 6 7 8 public void doGet(HttpServletRequest request, HttpServletResponse response) 9 throws ServletException, IOException { 10 11 BufferedImage image = new BufferedImage(IMG_WIDTH, IMG_HEIGHT, BufferedImage.TYPE_INT_RGB); // 实例化BufferedImage 12 Graphics g = image.getGraphics(); 13 Color c = new Color(200, 200, 255); // 验证码图片的背景颜色 14 g.setColor(c); 15 g.fillRect(0, 0, IMG_WIDTH, IMG_HEIGHT); // 图片的边框 16 17 StringBuffer sb = new StringBuffer(); // 用于保存验证码字符串 18 int index; // 数组的下标 19 for (int i = 0; i < NUMBER_OF_CHS; i++) { 20 index = r.nextInt(chs.length); // 随机一个下标 21 g.setColor(new Color(r.nextInt(88), r.nextInt(210), r.nextInt(150))); // 随机一个颜色 22 g.drawString(chs[index] + "", 15 * i + 3, 18); // 画出字符 23 sb.append(chs[index]); // 验证码字符串 24 } 25 26 request.getSession().setAttribute("piccode", sb.toString()); // 将验证码字符串保存到session中 27 ImageIO.write(image, "jpg", response.getOutputStream()); // 向页面输出图像 28 } 29 30 public void doPost(HttpServletRequest request, HttpServletResponse response) 31 throws ServletException, IOException { 32 doGet(request, response); 33 } 34 35 }

　　进行验证码图片验证的Servlet：

1 public class ValidateImageServlet extends HttpServlet { 2 3 public void doGet(HttpServletRequest request, HttpServletResponse response) 4 throws ServletException, IOException { 5 6 doPost(request, response); 7 } 8 9 public void doPost(HttpServletRequest request, HttpServletResponse response) 10 throws ServletException, IOException { 11 12 response.setContentType("text/html;charset=utf-8"); 13 String picString = (String) request.getSession().getAttribute("piccode"); 14 String checkCode = request.getParameter("verifyCode"); 15 PrintWriter out = response.getWriter(); 16 if (picString.toUpperCase().equals(checkCode.toUpperCase())) 17 out.println("验证码正确"); 18 else 19 out.print("验证码错误！"); 20 21 out.flush(); 22 out.close(); 23 } 24 25 }

 开源组件实现验证码

　　Jcaptcha：

　　一个用来生成图形验证码的开源组件，可以产生多种形式的验证码。可以与Spring组合使用。需要导入的jar包如下：

　　用于展示验证码的auth_code_captcha.jsp如下：

1 <form action="submit.action" method="post"> 2 <img src="jcaptcha.jpg" /> <input type="text" name="japtcha" value="" /> 3 <input type="submit"/> 4 </form>

　　web.xml的配置如下：

1 <servlet> 2 <servlet-name>jcaptcha</servlet-name> 3 <servlet-class>com.octo.captcha.module.servlet.image.SimpleImageCaptchaServlet</servlet-class> 4 </servlet> 5 <!-- 处理表单提交的Servlet --> 6 <servlet> 7 <servlet-name>submit</servlet-name> 8 <servlet-class>org.gpf.servlet.SubmitActionServlet</servlet-class> 9 </servlet> 10 <servlet-mapping> 11 <servlet-name>jcaptcha</servlet-name> 12 <url-pattern>/jcaptcha.jpg</url-pattern> 13 </servlet-mapping> 14 <servlet-mapping> 15 <servlet-name>submit</servlet-name> 16 <url-pattern>/submit.action</url-pattern> 17 </servlet-mapping>

　　表单提交的Servlet：

1 package org.gpf.servlet; 2 3 import java.io.IOException; 4 5 import javax.servlet.ServletException; 6 import javax.servlet.http.HttpServlet; 7 import javax.servlet.http.HttpServletRequest; 8 import javax.servlet.http.HttpServletResponse; 9 10 import com.octo.captcha.module.servlet.image.SimpleImageCaptchaServlet; 11 /** 12 * 图片验证码的captcha实现 13 * @author gaopengfei 14 * @date 2015-5-20 下午9:58:20 15 */ 16 public class SubmitActionServlet extends HttpServlet { 17 18 private static final long serialVersionUID = 1L; 19 20 protected void doPost(HttpServletRequest request, 21 HttpServletResponse response) throws ServletException, IOException { 22 23 String userCaptchaResponse = request.getParameter("japtcha"); 24 boolean captchaPassed = SimpleImageCaptchaServlet.validateResponse(request, userCaptchaResponse); 25 26 response.setContentType("text/html;charset=utf-8"); 27 if (captchaPassed) 28 response.getWriter().write("验证通过！"); 29 else { 30 response.getWriter().write("验证失败！"); 31 } 32 response.getWriter().write("<br/><a href='auth_code_captcha.jsp'>重新验证</a>"); 33 } 34 }

　　

　　kaptcha：

　　它是可以配置的，也可以生成各种样式的验证码。如下是其简单应用：用于显示验证码的index.jsp

1 <img alt="验证码图片" src="random.jpg"> 2 <form action="check.jsp" method="post"> 3 <input type="text" name="imageText"> 4 <input type="submit" value="验证"> 5 </form>

　　用于验证验证码的check.jsp

1 <%@ page import="com.google.code.kaptcha.Constants" %> 2 <%@ page language="java" import="java.util.*" contentType="text/html; charset=utf-8"%> 3 <% 4 String myImageText = request.getParameter("imageText"); 5 String key = (String)request.getSession().getAttribute(com.google.code.kaptcha.Constants.KAPTCHA_SESSION_KEY); 6 7 if(!myImageText.isEmpty() && myImageText.equals(key)) 8 out.print("验证通过！<br />"); 9 else 10 out.print("验证失败！<br />"); 11 out.print("你输入的字符：" + myImageText + ",验证码字符：" + key); 12 %>

　　配置图片显示的Servlet：

1 <servlet> 2 <servlet-name>Kcaptcha</servlet-name> 3 <servlet-class>com.google.code.kaptcha.servlet.KaptchaServlet</servlet-class> 4 </servlet> 5 <servlet-mapping> 6 <servlet-name>Kcaptcha</servlet-name> 7 <url-pattern>/random.jpg</url-pattern> 8 </servlet-mapping>

　　

Kaptcha的详细配置

1 <servlet> 2 <servlet-name>Kcaptcha</servlet-name> 3 <servlet-class>com.google.code.kaptcha.servlet.KaptchaServlet</servlet-class> 4 5 <!-- 边框 --> 6 <init-param> 7 <description>图片边框，yes（默认值）或者no</description> 8 <param-name>kaptcha.border</param-name> 9 <param-value>yes</param-value> 10 </init-param> 11 <init-param> 12 <description>边框颜色，white、black（默认）、blue等</description> 13 <param-name>kaptcha.border.color</param-name> 14 <param-value>green</param-value> 15 </init-param> 16 <init-param> 17 <description>边框厚度大于0</description> 18 <param-name>kaptcha.border.thickness</param-name> 19 <param-value>10</param-value> 20 </init-param> 21 22 <!-- 图片宽高 --> 23 <init-param> 24 <description>图片宽度</description> 25 <param-name>kaptcha.image.width</param-name> 26 <param-value>200</param-value> 27 </init-param> 28 <init-param> 29 <description>图片高度</description> 30 <param-name>kaptcha.image.height</param-name> 31 <param-value>60</param-value> 32 </init-param> 33 34 <!-- 图片样式 --> 35 <init-param> 36 <description>图片样式：水纹(WaterRipple)、鱼眼(FishEyeGimpy)、阴影(ShadowGimpy)</description> 37 <param-name>kaptcha.obscurificator.impl</param-name> 38 <param-value>com.google.code.kaptcha.impl.ShadowGimpy</param-value> 39 </init-param> 40 41 <!-- 背景 --> 42 <init-param> 43 <description>背景实现类</description> 44 <param-name>kaptcha.background.impl</param-name> 45 <param-value>com.google.code.kaptcha.impl.DefaultBackground</param-value> 46 </init-param> 47 <init-param> 48 <description>背景颜色渐变，指定开始颜色</description> 49 <param-name>kaptcha.background.clear.from</param-name> 50 <param-value>yellow</param-value> 51 </init-param> 52 <init-param> 53 <description>背景颜色渐变，指定结束颜色</description> 54 <param-name>kaptcha.background.clear.to</param-name> 55 <param-value>red</param-value> 56 </init-param> 57 58 <!-- 文本 --> 59 <init-param> 60 <description>文本集合，验证码文字从此集合中获取</description> 61 <param-name>kaptcha.textproducer.char.string</param-name> 62 <param-value>0123456789</param-value> 63 </init-param> 64 <init-param> 65 <description>验证码长度</description> 66 <param-name>kaptcha.textproducer.char.length</param-name> 67 <param-value>6</param-value> 68 </init-param> 69 <init-param> 70 <description>文字间隔</description> 71 <param-name>kaptcha.textproducer.char.space</param-name> 72 <param-value>2</param-value> 73 </init-param> 74 <!-- 字体 --> 75 <init-param> 76 <description>字体Arial，Courier</description> 77 <param-name>kaptcha.textproducer.font.names</param-name> 78 <param-value>Arial,Courier</param-value> 79 </init-param> 80 <init-param> 81 <description>字体大小</description> 82 <param-name>kaptcha.textproducer.font.size</param-name> 83 <param-value>40</param-value> 84 </init-param> 85 <init-param> 86 <description>字体颜色，white、black（默认）、blue等</description> 87 <param-name>kaptcha.textproducer.font.color</param-name> 88 <param-value>pink</param-value> 89 </init-param> 90 91 <init-param> 92 <description>文字渲染器</description> 93 <param-name>kaptcha.word.impl</param-name> 94 <param-value>com.google.code.kaptcha.text.impl.DefaultWordRenderer</param-value> 95 </init-param> 96 97 <!-- 图片和文本的实现类 --> 98 <init-param> 99 <description>图片实现类,可以重写这个类实现我们自己的图片</description> 100 <param-name>kaptcha.producer.impl</param-name> 101 <param-value>com.google.code.kaptcha.impl.DefaultKaptcha</param-value> 102 </init-param> 103 <init-param> 104 <description>文本实现类</description> 105 <param-name>kaptcha.textproducer.impl</param-name> 106 <param-value>com.google.code.kaptcha.text.impl.DefaultTextCreator</param-value> 107 </init-param> 108 109 <!-- 干扰 --> 110 <init-param> 111 <description>干扰实现类</description> 112 <param-name>kaptcha.noise.impl</param-name> 113 <param-value>com.google.code.kaptcha.impl.DefaultNoise</param-value> 114 </init-param> 115 <init-param> 116 <description>干扰颜色,合法值r,g,b或者white、black、blue</description> 117 <param-name>kaptcha.noise.color</param-name> 118 <param-value>255,0,0</param-value> 119 </init-param> 120 121 <init-param> 122 <description>session中存放验证码的key键</description> 123 <param-name>kaptcha.session.key</param-name> 124 <param-value>KAPTCHA_SESSION_KEY</param-value> 125 </init-param> 126 </servlet> 127 <servlet-mapping> 128 <servlet-name>Kcaptcha</servlet-name> 129 <url-pattern>/random.jpg</url-pattern> 130 </servlet-mapping>

　　中文验证码

　　查看前面的配置发现验证码字符的生成主要依靠的是kaptcha.textproducer.impl这个文本实现类，查看com.google.code.kaptcha.text.impl.DefaultTextCreator的源码，发现了它继承自 Configurable并实现了TextProducer接口。我们可以仿照它自定义我们自己的验证码中的文本生成器：

1 /** 2 * 中文验证码的实现类 3 */ 4 public class ChineseTextCreator extends Configurable implements TextProducer { 5 6 @Override 7 public String getText() { 8 9 int length = getConfig().getTextProducerCharLength(); 10 String finalWord = "", firstWord = ""; 11 int tempInt = 0; 12 String[] array = { "0", "1", "2", "3", "4", "5", "6", "7", "8", "9", 13 "a", "b", "c", "d", "e", "f" }; 14 15 Random rand = new Random(); 16 17 for (int i = 0; i < length; i++) { 18 switch (rand.nextInt(array.length)) { 19 case 1: 20 tempInt = rand.nextInt(26) + 65; 21 firstWord = String.valueOf((char) tempInt); 22 break; 23 case 2: 24 int r1, 25 r2, 26 r3, 27 r4; 28 String strH, 29 strL;// high&low 30 r1 = rand.nextInt(3) + 11; // 前闭后开[11,14) 31 if (r1 == 13) { 32 r2 = rand.nextInt(7); 33 } else { 34 r2 = rand.nextInt(16); 35 } 36 37 r3 = rand.nextInt(6) + 10; 38 if (r3 == 10) { 39 r4 = rand.nextInt(15) + 1; 40 } else if (r3 == 15) { 41 r4 = rand.nextInt(15); 42 } else { 43 r4 = rand.nextInt(16); 44 } 45 46 strH = array[r1] + array[r2]; 47 strL = array[r3] + array[r4]; 48 49 byte[] bytes = new byte[2]; 50 bytes[0] = (byte) (Integer.parseInt(strH, 16)); 51 bytes[1] = (byte) (Integer.parseInt(strL, 16)); 52 53 firstWord = new String(bytes); 54 break; 55 default: 56 tempInt = rand.nextInt(10) + 48; 57 firstWord = String.valueOf((char) tempInt); 58 break; 59 } 60 finalWord += firstWord; 61 } 62 return finalWord; 63 } 64 }

　　只需要在web.xml中将初始化参数由默认的文本实现类改成我们自己的实现类：

1 <init-param> 2 <description>文本实现类</description> 3 <param-name>kaptcha.textproducer.impl</param-name> 4 <param-value>ChineseTextCreator</param-value> 5 </init-param>

　　算式验证码

实现步骤如下：

获取随机的数值将结果相加将计算公式写入到验证码图片将相加的结果放入到session中

因此，我们需要重写KaptchaServlet这个用于生成验证码的Servlet。

1 public class MyKaptchaServlet extends HttpServlet implements Servlet{ 2 3 private Properties props; 4 private Producer kaptchaProducer; 5 private String sessionKeyValue; 6 7 public MyKaptchaServlet() { 8 props = new Properties(); 9 kaptchaProducer = null; 10 sessionKeyValue = null; 11 } 12 13 public void init(ServletConfig conf) throws ServletException { 14 super.init(conf); 15 16 ImageIO.setUseCache(false); 17 18 Enumeration initParams = conf.getInitParameterNames(); 19 while (initParams.hasMoreElements()) { 20 String key = (String) initParams.nextElement(); 21 String value = conf.getInitParameter(key); 22 this.props.put(key, value); 23 } 24 25 Config config = new Config(this.props); 26 this.kaptchaProducer = config.getProducerImpl(); 27 this.sessionKeyValue = config.getSessionKey(); 28 } 29 30 public void doGet(HttpServletRequest req, HttpServletResponse resp) 31 throws ServletException, IOException { 32 resp.setDateHeader("Expires", 0L); 33 34 resp.setHeader("Cache-Control", "no-store, no-cache, must-revalidate"); 35 36 resp.addHeader("Cache-Control", "post-check=0, pre-check=0"); 37 38 resp.setHeader("Pragma", "no-cache"); 39 40 resp.setContentType("image/jpeg"); 41 42 String capText = this.kaptchaProducer.createText(); 43 String s1 = capText.substring(0, 1); // 获取随机生成的第一个数字 44 String s2 = capText.substring(1, 2); // 由于web.xml中配置的验证码字符都是数字，不会发生数字格式化异常 45 int r = Integer.parseInt(s1) + Integer.parseInt(s2); 46 47 req.getSession().setAttribute(this.sessionKeyValue, String.valueOf(r)); // 将结果存入session 48 49 BufferedImage bi = this.kaptchaProducer.createImage(s1 + " + " + s2 + " = ?"); // 产生图片 50 51 ServletOutputStream out = resp.getOutputStream(); 52 53 ImageIO.write(bi, "jpg", out); 54 try { 55 out.flush(); 56 } finally { 57 out.close(); 58 } 59 } 60 61 }

　　在web.xml中有2点需要注意：

验证码文本只能是0~9这10个数字；验证码的长度是2（写多了也只会取出前2个随机数，写少了会抛出数字格式化异常）。 1 <servlet-name>Kcaptcha</servlet-name> 2 <servlet-class>MyKaptchaServlet</servlet-class> 3 <init-param> 4 <description>文本集合</description> 5 <param-name>kaptcha.textproducer.char.string</param-name> 6 <param-value>0123456789</param-value> 7 </init-param> 8 <init-param> 9 <description>验证码长度</description> 10 <param-name>kaptcha.textproducer.char.length</param-name> 11 <param-value>8</param-value> 12 </init-param>