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 ) {
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>jcaptchaservlet-name>
3 <servlet-class>com.octo.captcha.module.servlet.image.SimpleImageCaptchaServletservlet-class>
4 servlet>
5
6 <servlet>
7 <servlet-name>submitservlet-name>
8 <servlet-class>org.gpf.servlet.SubmitActionServletservlet-class>
9 servlet>
10 <servlet-mapping>
11 <servlet-name>jcaptchaservlet-name>
12 <url-pattern>/jcaptcha.jpgurl-pattern>
13 servlet-mapping>
14 <servlet-mapping>
15 <servlet-name>submitservlet-name>
16 <url-pattern>/submit.actionurl-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("
重新验证");
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！
");
9 else
10 out.print("验证失败！
");
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>Kcaptchaservlet-name>
3 <servlet-class>com.google.code.kaptcha.servlet.KaptchaServletservlet-class>
4 servlet>
5 <servlet-mapping>
6 <servlet-name>Kcaptchaservlet-name>
7 <url-pattern>/random.jpgurl-pattern>
8 servlet-mapping>
Kaptcha的详细配置
1 <servlet>
2 <servlet-name>Kcaptchaservlet-name>
3 <servlet-class>com.google.code.kaptcha.servlet.KaptchaServletservlet-class>
4
5
6 <init-param>
7 <description>图片边框，yes（默认值）或者nodescription>
8 <param-name>kaptcha.borderparam-name>
9 <param-value>yesparam-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.colorparam-name>
14 <param-value>greenparam-value>
15 init-param>
16 <init-param>
17 <description>边框厚度大于0description>
18 <param-name>kaptcha.border.thicknessparam-name>
19 <param-value>10param-value>
20 init-param>
21
22
23 <init-param>
24 <description>图片宽度description>
25 <param-name>kaptcha.image.widthparam-name>
26 <param-value>200param-value>
27 init-param>
28 <init-param>
29 <description>图片高度description>
30 <param-name>kaptcha.image.heightparam-name>
31 <param-value>60param-value>
32 init-param>
33
34
35 <init-param>
36 <description>图片样式：水纹(WaterRipple)、鱼眼(FishEyeGimpy)、阴影(ShadowGimpy)description>
37 <param-name>kaptcha.obscurificator.implparam-name>
38 <param-value>com.google.code.kaptcha.impl.ShadowGimpyparam-value>
39 init-param>
40
41
42 <init-param>
43 <description>背景实现类description>
44 <param-name>kaptcha.background.implparam-name>
45 <param-value>com.google.code.kaptcha.impl.DefaultBackgroundparam-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.fromparam-name>
50 <param-value>yellowparam-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.toparam-name>
55 <param-value>redparam-value>
56 init-param>
57
58
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.stringparam-name>
62 <param-value>0123456789param-value>
63 init-param>
64 <init-param>
65 <description>验证码长度description>
66 <param-name>kaptcha.textproducer.char.lengthparam-name>
67 <param-value>6param-value>
68 init-param>
69 <init-param>
70 <description>文字间隔description>
71 <param-name>kaptcha.textproducer.char.spaceparam-name>
72 <param-value>2param-value>
73 init-param>
74
75 <init-param>
76 <description>字体Arial，Courierdescription>
77 <param-name>kaptcha.textproducer.font.namesparam-name>
78 <param-value>Arial,Courierparam-value>
79 init-param>
80 <init-param>
81 <description>字体大小description>
82 <param-name>kaptcha.textproducer.font.sizeparam-name>
83 <param-value>40param-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.colorparam-name>
88 <param-value>pinkparam-value>
89 init-param>
90
91 <init-param>
92 <description>文字渲染器description>
93 <param-name>kaptcha.word.implparam-name>
94 <param-value>com.google.code.kaptcha.text.impl.DefaultWordRendererparam-value>
95 init-param>
96
97
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.implparam-name>
101 <param-value>com.google.code.kaptcha.impl.DefaultKaptchaparam-value>
102 init-param>
103 <init-param>
104 <description>文本实现类description>
105 <param-name>kaptcha.textproducer.implparam-name>
106 <param-value>com.google.code.kaptcha.text.impl.DefaultTextCreatorparam-value>
107 init-param>
108
109
110 <init-param>
111 <description>干扰实现类description>
112 <param-name>kaptcha.noise.implparam-name>
113 <param-value>com.google.code.kaptcha.impl.DefaultNoiseparam-value>
114 init-param>
115 <init-param>
116 <description>干扰颜色,合法值r,g,b或者white、black、bluedescription>
117 <param-name>kaptcha.noise.colorparam-name>
118 <param-value>255,0,0param-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.keyparam-name>
124 <param-value>KAPTCHA_SESSION_KEYparam-value>
125 init-param>
126 servlet>
127 <servlet-mapping>
128 <servlet-name>Kcaptchaservlet-name>
129 <url-pattern>/random.jpgurl-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 ) {
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.implparam-name>
4 <param-value>ChineseTextCreatorparam-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>Kcaptchaservlet-name>
2 <servlet-class>MyKaptchaServletservlet-class>
3 <init-param>
4 <description>文本集合description>
5 <param-name>kaptcha.textproducer.char.stringparam-name>
6 <param-value>0123456789param-value>
7 init-param>
8 <init-param>
9 <description>验证码长度description>
10 <param-name>kaptcha.textproducer.char.lengthparam-name>
11 <param-value>8param-value>
12 init-param>
Java实现验证码的制作
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