利用开源组件制作验证码

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Servlet C++C#C Web

jsp验证码制作

　　介绍两个功能强大的开源制作验证码组件SimpleCaptcha，JCAPTCHA。

　　一、SimpleCaptcha搜狐邮箱注册时就使用了该组件，主页:
http://simplecaptcha.sourceforge.net/index.html

example

1.配置
将下载的jar文件放置工程的lib目录下，打开工程的web.xml文件加上相应的配置
<servlet>
<servlet-name>Captcha</servlet-name>
<servlet-class>nl.captcha.servlet.CaptchaServlet</servlet-class>

<init-param>
<param-name>cap.border</param-name>
<param-value>yes</param-value>
</init-param>

<init-param>
<param-name>cap.border.c</param-name>
<param-value>green</param-value>
</init-param>

<init-param>
<param-name>cap.border.th</param-name>
<param-value>1</param-value>
</init-param>

<init-param>
<param-name>cap.cap.producer</param-name>
<param-value>
nl.captcha.obscurity.imp.DefaultCaptchaIml
</param-value>
</init-param>

<init-param>
<param-name>cap.text.producer</param-name>


<param-value>org.ChineseTextProducer</param-value>
</init-param>

<init-param>
<param-name>cap.char.arr</param-name>
<param-value>
2,3,4,6,7,8,9,a,b,c,d,e,f,g,h,j,k,l,m,n,o,p,q,r,s,t,u,v,x,y,z
</param-value>
</init-param>

<init-param>
<param-name>cap.char.arr.l</param-name>
<param-value>4</param-value>
</init-param>

<init-param>
<param-name>cap.font.arr</param-name>

<param-value>
Arial,Helvetica,Courier,TimesRoman,宋体,黑体
</param-value>
</init-param>

<init-param>
<param-name>cap.font.size</param-name>
<param-value>30</param-value>
</init-param>

<init-param>
<param-name>cap.font.color</param-name>
<param-value>white</param-value>
</init-param>



<init-param>
<param-name>cap.obscurificator</param-name>
<param-value>org.FishEyeGimpyImp</param-value>
</init-param>

<init-param>
<param-name>cap.border</param-name>
<param-value>no</param-value>
</init-param>

<init-param>
<param-name>cap.char.arr.l</param-name>
<param-value>6</param-value>
</init-param>

<init-param>
<param-name>cap.background.c.to</param-name>
<param-value>white</param-value>
</init-param>

<init-param>
<param-name>cap.background.c.from</param-name>
<param-value>white</param-value>
</init-param>

<init-param>
<param-name>cap.distortionImp</param-name>
<param-value />
</init-param>

<init-param>
<param-name>cap.backgroundImp</param-name>
<param-value />
</init-param>

<init-param>
<param-name>cap.background.c.to</param-name>
<param-value>black</param-value>
</init-param>

<init-param>
<param-name>cap.background.c.from</param-name>
<param-value>black</param-value>
</init-param>

<init-param>
<param-name>cap.noiseImp</param-name>
<param-value>nl.captcha.obscurity.imp.DefaultNoiseImp</param-value>
</init-param>

</servlet>
<servlet-mapping>
<servlet-name>Captcha</servlet-name>
<url-pattern>/Captcha.jpg</url-pattern>
</servlet-mapping>
以上配置可根据喜好设置。

2、调用显示

在要显示验证码的页面中加入<img src="Captcha.jpg">即可显示生成的验证码

3、后台验证
验证非常简单，通过session.getAttribute(nl.captcha.servlet.Constants.SIMPLE_CAPCHA_SESSION_KEY);即可得到组件生成
的验证码，然后与前台传递的用户填写的内容比较即可。

注：如果要自定义验证码的内容可以继承DefaultTextCreator类，覆写getText()方法即可，方法返回的是一个字符串。

　　二、JCAPTCHA，该组件功能非常强大，可以生成word、图片、声音等验证码。主页：
http://forge.octo.com/jcaptcha/confluence/display/general/Home
http://jcaptcha.sourceforge.net/

1、配置
下载JCAPTCHA后将jcaptcha.jar和commons-collections-2.1以上.jar(单独下载，地址：http://commons.apache.org/collections/ )放置工程lib目录下。

2、Implement a CaptchaService

import com.octo.captcha.service.image.ImageCaptchaService;
import com.octo.captcha.service.image.DefaultManageableImageCaptchaService;

public class CaptchaServiceSingleton {

private static ImageCaptchaService instance = new DefaultManageableImageCaptchaService();

public static ImageCaptchaService getInstance(){
return instance;
　　}
}

3、编写一个产生验证码的servlet

public class ImageCaptchaServlet extends HttpServlet {

protected void doGet(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse)
throws ServletException, IOException {

byte[] captchaChallengeAsJpeg = null;

ByteArrayOutputStream jpegOutputStream = new ByteArrayOutputStream();
try {
String captchaId = httpServletRequest.getSession().getId();

BufferedImage challenge =
CaptchaServiceSingleton.getInstance().getImageChallengeForID(captchaId,
httpServletRequest.getLocale());
JPEGImageEncoder jpegEncoder = JPEGCodec.createJPEGEncoder(jpegOutputStream);
jpegEncoder.encode(challenge);
} catch (IllegalArgumentException e) {
httpServletResponse.sendError(HttpServletResponse.SC_NOT_FOUND);
return;
} catch (CaptchaServiceException e) {
httpServletResponse.sendError(HttpServletResponse.SC_INTERNAL_SERVER_ERROR);
return;
}

captchaChallengeAsJpeg = jpegOutputStream.toByteArray();

httpServletResponse.setHeader("Cache-Control", "no-store");
httpServletResponse.setHeader("Pragma", "no-cache");
httpServletResponse.setDateHeader("Expires", 0);
httpServletResponse.setContentType("image/jpeg");
ServletOutputStream responseOutputStream =
httpServletResponse.getOutputStream();
responseOutputStream.write(captchaChallengeAsJpeg);
responseOutputStream.flush();
responseOutputStream.close();
}
}

4、将servlet添加到web.xml文件中
<servlet>
<servlet-name>jcaptcha</servlet-name>
<servlet-class>ImageCaptchaServlet</servlet-class>
<load-on-startup>0</load-on-startup>
</servlet>

<servlet-mapping>
<servlet-name>jcaptcha</servlet-name>
<url-pattern>/jcaptcha</url-pattern>
</servlet-mapping>

5、在页面中显示
<img src="jcaptcha">
<input type='text' name='captcha_code' value=''>

6、后台验证
Boolean isResponseCorrect =Boolean.FALSE;
String captchaId = httpServletRequest.getSession().getId();
String response = httpServletRequest.getParameter("captcha_code");
try {
isResponseCorrect = CaptchaServiceSingleton.getInstance().validateResponseForID(captchaId,response);
} catch (CaptchaServiceException e) {
//TODO
}
最简单的开发过程结束，试运行一下效果！

注：要实现自己的验证引擎可以继承ListImageCaptchaEngine实现抽象方法buildInitialFactories()。

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