用开源组件jcaptcha做jsp彩色验证码

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

public class CaptchaServiceSingleton{

private static ImageCaptchaServiceinstance = new DefaultManageableImageCaptchaService();

public static ImageCaptchaServicegetInstance(){
return instance;
}
}

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(ServletConfigservletConfig) throws ServletException{

super .init(servletConfig);

}


protected void doGet(HttpServletRequesthttpServletRequest,HttpServletResponsehttpServletResponse) throws ServletException,IOException{

byte []captchaChallengeAsJpeg = null ;
// theoutputstreamtorenderthecaptchaimageasjpeginto
ByteArrayOutputStreamjpegOutputStream = new ByteArrayOutputStream();
try {
// getthesessionidthatwillidentifythegeneratedcaptcha.
// thesameidmustbeusedtovalidatetheresponse,thesessionidisagoodcandidate!
StringcaptchaId = httpServletRequest.getSession().getId();
// calltheImageCaptchaServicegetChallengemethod
BufferedImagechallenge =
CaptchaServiceSingleton.getInstance().getImageChallengeForID(captchaId,
httpServletRequest.getLocale());

// ajpegencoder
JPEGImageEncoderjpegEncoder =
JPEGCodec.createJPEGEncoder(jpegOutputStream);
jpegEncoder.encode(challenge);
} catch (IllegalArgumentExceptione){
httpServletResponse.sendError(HttpServletResponse.SC_NOT_FOUND);
return ;
} catch (CaptchaServiceExceptione){
httpServletResponse.sendError(HttpServletResponse.SC_INTERNAL_SERVER_ERROR);
return ;
}

captchaChallengeAsJpeg = jpegOutputStream.toByteArray();

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

< 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 >

< img src ="jcaptcha" >
< input type ='text' name ='j_captcha_response' value ='' >