Java实现验证码的制作

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：

1. 验证码文本只能是0~9这10个数字；
2. 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>