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.