用开源组件jcaptcha做jsp彩色验证码

安装

Add jcaptcha-all.jar (provided in bin-distribution

)
and ehcache.jar (not provided see ehcache
site

)
to your application class path, ie in you WEB-INF/lib folder.

实例一个jcaptcha服务，注意，必须是单例模式的

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;

}

}

注:以上是默认的一个实现，下面是其他更多的实现

SimpleListSoundCaptchaEngine //还可以用声音，真爽哦
SpellerSoundCaptchaEngine
SpellerSoundCaptchaEngine
DefaultGimpyEngineCaptcha
BaffleListGimpyEngineCaptcha
BasicListGimpyEngineCaptcha
DeformedBaffleListGimpyEngineCaptcha
DoubleRandomListGimpyEngineCaptcha
SimpleListImageCaptchaEngineCaptcha
SimpleFishEyeEngineCaptcha

具体请参考官方说明

编写一个产生图片的servlet

import com.octo.captcha.service.CaptchaServiceException;

import com.sun.image.codec.jpeg.JPEGCodec;

import com.sun.image.codec.jpeg.JPEGImageEncoder;

import javax.servlet.ServletConfig;

import javax.servlet.ServletException;

import javax.servlet.ServletOutputStream;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

import java.awt.image.BufferedImage;

import java.io.ByteArrayOutputStream;

import java.io.IOException;

public class ImageCaptchaServlet extends HttpServlet {

public void init(ServletConfig servletConfig) throws ServletException {

super.init(servletConfig);

}

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

byte[] captchaChallengeAsJpeg = null;

// the output stream to render the captcha image as jpeg into

ByteArrayOutputStream jpegOutputStream = new ByteArrayOutputStream();

try {

// get the session id that will identify the generated captcha.

//the same id must be used to validate the response, the session id is a good candidate!

String captchaId = httpServletRequest.getSession().getId();

// call the ImageCaptchaService getChallenge method

BufferedImage challenge =

CaptchaServiceSingleton.getInstance().getImageChallengeForID(captchaId,

httpServletRequest.getLocale());

// a jpeg encoder

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();

// flush it in the response

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();

}

}

为servlet修改web.xml配置文件

<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>

编写你的客户端的展示

<img src="jcaptcha">

<input type='text' name='j_captcha_response' value=''>

上面的src="jcaptcha" 就是调用了上面的servlet,text里是用户填写的确认验证码

后台逻辑验证

Boolean isResponseCorrect =Boolean.FALSE;

//remenber that we need an id to validate!

String captchaId = httpServletRequest.getSession().getId();

//retrieve the response

String response = httpServletRequest.getParameter("j_captcha_response");

// Call the Service method

try {

isResponseCorrect = CaptchaServiceSingleton.getInstance().validateResponseForID(captchaId,

response);

} catch (CaptchaServiceException e) {

//should not happen, may be thrown if the id is not valid

}

OK,大功告成了.