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。

 <script type="text/javascript">
     function reloadCode(){
         var time = new Date();
         // 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
         document.getElementById('safecode').src = '<%=request.getContextPath()%>/servlet/ImageServlet?d=' + time;
     }
 </script>    

 <form action="<%=request.getContextPath()%>/servlet/ValidateImageServlet"method="post">
         验证码：<img src="<%=request.getContextPath()%>/servlet/ImageServlet" alt="验证码" id="safecode">
     <input type="text" id="verifyCode" name="verifyCode" size="6" />
     <a href="javascript:reloadCode();">看不清楚</a><br>
     <input type="submit" value="登录" />
 </form>

　　我们用ImageServlet实时生成图片。生成图片所需要的步骤如下：

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

　　检验验证码是否正确：ValidateImageServlet：

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

　　验证的流程如下：

　　生成验证码的ImageServlet：

 private static Random r = new Random();
     private static char[] chs = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789".toCharArray();
     private static final int NUMBER_OF_CHS = 4;
     private static final int IMG_WIDTH = 65;
     private static final int IMG_HEIGHT = 25;

     public void doGet(HttpServletRequest request, HttpServletResponse response)
             throws ServletException, IOException {

             BufferedImage image = new BufferedImage(IMG_WIDTH, IMG_HEIGHT, BufferedImage.TYPE_INT_RGB);    // 实例化BufferedImage
             Graphics g = image.getGraphics();
             Color c = new Color(200, 200, 255);                                             // 验证码图片的背景颜色
             g.setColor(c);
             g.fillRect(0, 0, IMG_WIDTH, IMG_HEIGHT);                                        // 图片的边框

             StringBuffer sb = new StringBuffer();                                           // 用于保存验证码字符串
             int index;                                                                      // 数组的下标
             for (int i = 0; i < NUMBER_OF_CHS; i++) {
                 index = r.nextInt(chs.length);                                              // 随机一个下标
                 g.setColor(new Color(r.nextInt(88), r.nextInt(210), r.nextInt(150)));       // 随机一个颜色
                 g.drawString(chs[index] + "", 15 * i + 3, 18);                              // 画出字符
                 sb.append(chs[index]);                                                      // 验证码字符串
             }

             request.getSession().setAttribute("piccode", sb.toString());                    // 将验证码字符串保存到session中
             ImageIO.write(image, "jpg", response.getOutputStream());                        // 向页面输出图像
     }

     public void doPost(HttpServletRequest request, HttpServletResponse response)
             throws ServletException, IOException {
         doGet(request, response);
     }

 }

　　进行验证码图片验证的Servlet：

 public class ValidateImageServlet extends HttpServlet {

     public void doGet(HttpServletRequest request, HttpServletResponse response)
             throws ServletException, IOException {

         doPost(request, response);
     }

     public void doPost(HttpServletRequest request, HttpServletResponse response)
             throws ServletException, IOException {

         response.setContentType("text/html;charset=utf-8");
         String picString = (String) request.getSession().getAttribute("piccode");
         String checkCode = request.getParameter("verifyCode");
         PrintWriter out = response.getWriter();
         if (picString.toUpperCase().equals(checkCode.toUpperCase()))
             out.println("验证码正确");
         else
             out.print("验证码错误！");

         out.flush();
         out.close();
     }

 }

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：

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

　　web.xml的配置如下：

 <servlet>
     <servlet-name>jcaptcha</servlet-name>
     <servlet-class>com.octo.captcha.module.servlet.image.SimpleImageCaptchaServlet</servlet-class>
 </servlet>
 <!-- 处理表单提交的Servlet -->
 <servlet>
     <servlet-name>submit</servlet-name>
     <servlet-class>org.gpf.servlet.SubmitActionServlet</servlet-class>
 </servlet>
 <servlet-mapping>
     <servlet-name>jcaptcha</servlet-name>
     <url-pattern>/jcaptcha.jpg</url-pattern>
 </servlet-mapping>
 <servlet-mapping>
     <servlet-name>submit</servlet-name>
     <url-pattern>/submit.action</url-pattern>
 </servlet-mapping>

　　表单提交的Servlet：

 package org.gpf.servlet;

 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.octo.captcha.module.servlet.image.SimpleImageCaptchaServlet;
 /**
  * 图片验证码的captcha实现
  * @author gaopengfei
  * @date 2015-5-20 下午9:58:20
  */
 public class SubmitActionServlet extends HttpServlet {

     private static final long serialVersionUID = 1L;

     protected void doPost(HttpServletRequest request,
             HttpServletResponse response) throws ServletException, IOException {

         String userCaptchaResponse = request.getParameter("japtcha");
         boolean captchaPassed = SimpleImageCaptchaServlet.validateResponse(request, userCaptchaResponse);

         response.setContentType("text/html;charset=utf-8");
         if (captchaPassed)
             response.getWriter().write("验证通过！");
         else {
             response.getWriter().write("验证失败！");
         }
         response.getWriter().write("<br/><a href='auth_code_captcha.jsp'>重新验证</a>");
     }
 }

　　

　　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

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

　　用于验证验证码的check.jsp

 <%@ page import="com.google.code.kaptcha.Constants" %>
 <%@ page language="java" import="java.util.*" contentType="text/html; charset=utf-8"%>
 <%
     String myImageText = request.getParameter("imageText");
     String key = (String)request.getSession().getAttribute(com.google.code.kaptcha.Constants.KAPTCHA_SESSION_KEY);

     if(!myImageText.isEmpty() && myImageText.equals(key))
         out.print("验证通过！<br />");
     else
         out.print("验证失败！<br />");
     out.print("你输入的字符：" + myImageText + ",验证码字符：" + key);
  %>

　　配置图片显示的Servlet：

 <servlet>
     <servlet-name>Kcaptcha</servlet-name>
     <servlet-class>com.google.code.kaptcha.servlet.KaptchaServlet</servlet-class>
 </servlet>
 <servlet-mapping>
     <servlet-name>Kcaptcha</servlet-name>
     <url-pattern>/random.jpg</url-pattern>
 </servlet-mapping>

　　

Kaptcha的详细配置

 <servlet>
     <servlet-name>Kcaptcha</servlet-name>
     <servlet-class>com.google.code.kaptcha.servlet.KaptchaServlet</servlet-class>

     <!-- 边框 -->
     <init-param>
         <description>图片边框，yes（默认值）或者no</description>
         <param-name>kaptcha.border</param-name>
         <param-value>yes</param-value>
     </init-param>
     <init-param>
         <description>边框颜色，white、black（默认）、blue等</description>
         <param-name>kaptcha.border.color</param-name>
         <param-value>green</param-value>
     </init-param>
     <init-param>
         <description>边框厚度大于0</description>
         <param-name>kaptcha.border.thickness</param-name>
         <param-value>10</param-value>
     </init-param>

     <!-- 图片宽高 -->
     <init-param>
         <description>图片宽度</description>
         <param-name>kaptcha.image.width</param-name>
         <param-value>200</param-value>
     </init-param>
     <init-param>
         <description>图片高度</description>
         <param-name>kaptcha.image.height</param-name>
         <param-value>60</param-value>
     </init-param>

     <!-- 图片样式 -->
     <init-param>
         <description>图片样式：水纹(WaterRipple)、鱼眼(FishEyeGimpy)、阴影(ShadowGimpy)</description>
         <param-name>kaptcha.obscurificator.impl</param-name>
         <param-value>com.google.code.kaptcha.impl.ShadowGimpy</param-value>
     </init-param>

     <!-- 背景 -->
     <init-param>
         <description>背景实现类</description>
         <param-name>kaptcha.background.impl</param-name>
         <param-value>com.google.code.kaptcha.impl.DefaultBackground</param-value>
     </init-param>
     <init-param>
         <description>背景颜色渐变，指定开始颜色</description>
         <param-name>kaptcha.background.clear.from</param-name>
         <param-value>yellow</param-value>
     </init-param>
     <init-param>
         <description>背景颜色渐变，指定结束颜色</description>
         <param-name>kaptcha.background.clear.to</param-name>
         <param-value>red</param-value>
     </init-param>

     <!-- 文本 -->
     <init-param>
         <description>文本集合，验证码文字从此集合中获取</description>
         <param-name>kaptcha.textproducer.char.string</param-name>
         <param-value>0123456789</param-value>
     </init-param>
     <init-param>
         <description>验证码长度</description>
         <param-name>kaptcha.textproducer.char.length</param-name>
         <param-value>6</param-value>
     </init-param>
     <init-param>
         <description>文字间隔</description>
         <param-name>kaptcha.textproducer.char.space</param-name>
         <param-value>2</param-value>
     </init-param>
     <!-- 字体 -->
     <init-param>
         <description>字体Arial，Courier</description>
         <param-name>kaptcha.textproducer.font.names</param-name>
         <param-value>Arial,Courier</param-value>
     </init-param>
     <init-param>
         <description>字体大小</description>
         <param-name>kaptcha.textproducer.font.size</param-name>
         <param-value>40</param-value>
     </init-param>
     <init-param>
         <description>字体颜色，white、black（默认）、blue等</description>
         <param-name>kaptcha.textproducer.font.color</param-name>
         <param-value>pink</param-value>
     </init-param>

     <init-param>
         <description>文字渲染器</description>
         <param-name>kaptcha.word.impl</param-name>
         <param-value>com.google.code.kaptcha.text.impl.DefaultWordRenderer</param-value>
     </init-param>

     <!-- 图片和文本的实现类 -->
     <init-param>
         <description>图片实现类,可以重写这个类实现我们自己的图片</description>
         <param-name>kaptcha.producer.impl</param-name>
         <param-value>com.google.code.kaptcha.impl.DefaultKaptcha</param-value>
     </init-param>
     <init-param>
         <description>文本实现类</description>
         <param-name>kaptcha.textproducer.impl</param-name>
         <param-value>com.google.code.kaptcha.text.impl.DefaultTextCreator</param-value>
     </init-param>

     <!-- 干扰 -->
     <init-param>
         <description>干扰实现类</description>
         <param-name>kaptcha.noise.impl</param-name>
         <param-value>com.google.code.kaptcha.impl.DefaultNoise</param-value>
     </init-param>
     <init-param>
         <description>干扰颜色,合法值r,g,b或者white、black、blue</description>
         <param-name>kaptcha.noise.color</param-name>
         <param-value>255,0,0</param-value>
     </init-param>

     <init-param>
         <description>session中存放验证码的key键</description>
         <param-name>kaptcha.session.key</param-name>
         <param-value>KAPTCHA_SESSION_KEY</param-value>
     </init-param>
 </servlet>
 <servlet-mapping>
     <servlet-name>Kcaptcha</servlet-name>
     <url-pattern>/random.jpg</url-pattern>
 </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：

 /**
  * 中文验证码的实现类
  */
 public class ChineseTextCreator extends Configurable implements TextProducer {

     @Override
     public String getText() {

         int length = getConfig().getTextProducerCharLength();
         String finalWord = "", firstWord = "";
         int tempInt = 0;
         String[] array = { "0", "1", "2", "3", "4", "5", "6", "7", "8", "9",
                 "a", "b", "c", "d", "e", "f" };

         Random rand = new Random();

         for (int i = 0; i < length; i++) {
             switch (rand.nextInt(array.length)) {
             case 1:
                 tempInt = rand.nextInt(26) + 65;
                 firstWord = String.valueOf((char) tempInt);
                 break;
             case 2:
                 int r1,
                 r2,
                 r3,
                 r4;
                 String strH,
                 strL;// high&low
                 r1 = rand.nextInt(3) + 11; // 前闭后开[11,14)
                 if (r1 == 13) {
                     r2 = rand.nextInt(7);
                 } else {
                     r2 = rand.nextInt(16);
                 }

                 r3 = rand.nextInt(6) + 10;
                 if (r3 == 10) {
                     r4 = rand.nextInt(15) + 1;
                 } else if (r3 == 15) {
                     r4 = rand.nextInt(15);
                 } else {
                     r4 = rand.nextInt(16);
                 }

                 strH = array[r1] + array[r2];
                 strL = array[r3] + array[r4];

                 byte[] bytes = new byte[2];
                 bytes[0] = (byte) (Integer.parseInt(strH, 16));
                 bytes[1] = (byte) (Integer.parseInt(strL, 16));

                 firstWord = new String(bytes);
                 break;
             default:
                 tempInt = rand.nextInt(10) + 48;
                 firstWord = String.valueOf((char) tempInt);
                 break;
             }
             finalWord += firstWord;
         }
         return finalWord;
     }
 }

　　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：

 <init-param>
     <description>文本实现类</description>
     <param-name>kaptcha.textproducer.impl</param-name>
     <param-value>ChineseTextCreator</param-value>
 </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。

 public class MyKaptchaServlet extends HttpServlet implements Servlet{

     private Properties props;
     private Producer kaptchaProducer;
     private String sessionKeyValue;

     public MyKaptchaServlet() {
          props = new Properties();
          kaptchaProducer = null;
          sessionKeyValue = null;
     }

     public void init(ServletConfig conf) throws ServletException {
         super.init(conf);

         ImageIO.setUseCache(false);

         Enumeration initParams = conf.getInitParameterNames();
         while (initParams.hasMoreElements()) {
             String key = (String) initParams.nextElement();
             String value = conf.getInitParameter(key);
             this.props.put(key, value);
         }

         Config config = new Config(this.props);
         this.kaptchaProducer = config.getProducerImpl();
         this.sessionKeyValue = config.getSessionKey();
     }

     public void doGet(HttpServletRequest req, HttpServletResponse resp)
             throws ServletException, IOException {
         resp.setDateHeader("Expires", 0L);

         resp.setHeader("Cache-Control", "no-store, no-cache, must-revalidate");

         resp.addHeader("Cache-Control", "post-check=0, pre-check=0");

         resp.setHeader("Pragma", "no-cache");

         resp.setContentType("image/jpeg");

         String capText = this.kaptchaProducer.createText();
         String s1 = capText.substring(0, 1);    // 获取随机生成的第一个数字
         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
         int r = Integer.parseInt(s1) + Integer.parseInt(s2);

         req.getSession().setAttribute(this.sessionKeyValue, String.valueOf(r));    // 将结果存入session

         BufferedImage bi = this.kaptchaProducer.createImage(s1 + " + " + s2 + " = ?"); // 产生图片

         ServletOutputStream out = resp.getOutputStream();

         ImageIO.write(bi, "jpg", out);
         try {
             out.flush();
         } finally {
             out.close();
         }
     }

 }

　　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）。

 <servlet-name>Kcaptcha</servlet-name>
     <servlet-class>MyKaptchaServlet</servlet-class>
 <init-param>
         <description>文本集合</description>
         <param-name>kaptcha.textproducer.char.string</param-name>
         <param-value>0123456789</param-value>
     </init-param>
     <init-param>
     <description>验证码长度</description>
     <param-name>kaptcha.textproducer.char.length</param-name>
     <param-value>8</param-value>
 </init-param>