使用 jcaptcha 產生圖片校正碼

安裝

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.

執行個體一個jcaptcha服務，注意，必須是單例模式的

1. import com.octo.captcha.service.image.ImageCaptchaService;
2. import com.octo.captcha.service.image.DefaultManageableImageCaptchaService;
4. public class CaptchaServiceSingleton {
5.     
6.     private static ImageCaptchaService instance = new DefaultManageableImageCaptchaService();
7.     
8.     public static ImageCaptchaService getInstance(){
9.         return instance;
10.     }
11. }

注:以上是預設的一個實現，下面是其他更多的實現

SimpleListSoundCaptchaEngine   //還可以用聲音，真爽哦
SpellerSoundCaptchaEngine
SpellerSoundCaptchaEngine
DefaultGimpyEngineCaptcha           
BaffleListGimpyEngineCaptcha           
BasicListGimpyEngineCaptcha           
DeformedBaffleListGimpyEngineCaptcha           
DoubleRandomListGimpyEngineCaptcha           
SimpleListImageCaptchaEngineCaptcha           
SimpleFishEyeEngineCaptcha
具體請參考官方說明

編寫一個產生圖片的servlet

1. import com.octo.captcha.service.CaptchaServiceException;
2. import com.sun.image.codec.jpeg.JPEGCodec;
3. import com.sun.image.codec.jpeg.JPEGImageEncoder;
5. import javax.servlet.ServletConfig;
6. import javax.servlet.ServletException;
7. import javax.servlet.ServletOutputStream;
8. import javax.servlet.http.HttpServlet;
9. import javax.servlet.http.HttpServletRequest;
10. import javax.servlet.http.HttpServletResponse;
11. import java.awt.image.BufferedImage;
12. import java.io.ByteArrayOutputStream;
13. import java.io.IOException;
16. public class ImageCaptchaServlet extends HttpServlet {
19.     public void init(ServletConfig servletConfig) throws ServletException {
21.         super.init(servletConfig);
23.     }
26.     protected void doGet(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse) throws ServletException, IOException {
27.         
28.        byte[] captchaChallengeAsJpeg = null;
29.        // the output stream to render the captcha image as jpeg into
30.         ByteArrayOutputStream jpegOutputStream = new ByteArrayOutputStream();
31.         try {
32.         // get the session id that will identify the generated captcha. 
33.         //the same id must be used to validate the response, the session id is a good candidate!
34.         String captchaId = httpServletRequest.getSession().getId();
35.         // call the ImageCaptchaService getChallenge method
36.             BufferedImage challenge =
37.                     CaptchaServiceSingleton.getInstance().getImageChallengeForID(captchaId,
38.                             httpServletRequest.getLocale());
39.             
40.             // a jpeg encoder
41.             JPEGImageEncoder jpegEncoder =
42.                     JPEGCodec.createJPEGEncoder(jpegOutputStream);
43.             jpegEncoder.encode(challenge);
44.         } catch (IllegalArgumentException e) {
45.             httpServletResponse.sendError(HttpServletResponse.SC_NOT_FOUND);
46.             return;
47.         } catch (CaptchaServiceException e) {
48.             httpServletResponse.sendError(HttpServletResponse.SC_INTERNAL_SERVER_ERROR);
49.             return;
50.         }
52.         captchaChallengeAsJpeg = jpegOutputStream.toByteArray();
54.         // flush it in the response
55.         httpServletResponse.setHeader("Cache-Control", "no-store");
56.         httpServletResponse.setHeader("Pragma", "no-cache");
57.         httpServletResponse.setDateHeader("Expires", 0);
58.         httpServletResponse.setContentType("image/jpeg");
59.         ServletOutputStream responseOutputStream =
60.                 httpServletResponse.getOutputStream();
61.         responseOutputStream.write(captchaChallengeAsJpeg);
62.         responseOutputStream.flush();
63.         responseOutputStream.close();
64.     }
65. }

為servlet修改web.xml設定檔

1. <servlet>
2.         <servlet-name>jcaptcha</servlet-name>
3.         <servlet-class>ImageCaptchaServlet</servlet-class>
4.         <load-on-startup>0</load-on-startup>
5.     </servlet>
8. <servlet-mapping>
9.         <servlet-name>jcaptcha</servlet-name>
10.         <url-pattern>/jcaptcha</url-pattern>
11. </servlet-mapping>

編寫你的用戶端的展示

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

 

上面的src="jcaptcha"  就是調用了上面的servlet,text裡是使用者填寫的確認驗證碼

或者把圖片串連那句換成下句

1. <img src="/jcaptcha" id="checkCodeImg" onclick="this.src='/jcaptcha?now=' + new Date().getTime()" alt="看不清，點擊換一張" >請輸入校正碼，大小寫不區分<br> 如看不清，請點擊圖片換一張 

後台邏輯驗證

1. Boolean isResponseCorrect =Boolean.FALSE;
2.            //remenber that we need an id to validate!
3.            String captchaId = httpServletRequest.getSession().getId();
4.            //retrieve the response
5.            String response = httpServletRequest.getParameter("j_captcha_response");
6.            // Call the Service method
7.             try {
8.                 isResponseCorrect = CaptchaServiceSingleton.getInstance().validateResponseForID(captchaId,
9.                         response);
10.             } catch (CaptchaServiceException e) {
11.                  //should not happen, may be thrown if the id is not valid 
12.             }

OK,大功告成了