This page demonstrates how to use jcaptcha in your application.
This tutorial uses the CaptchaService and sub components (see Architecture overview).
No release was published since Maven2 is working, but nightly build are available in Archiva : http://forge.octo.com/archiva/browse/com.octo.captcha/jcaptcha/1.0-SNAPSHOT In order to get the lastest version you have to add the following repository to your project POM :
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Add the following dependency to your project POM
<dependency> <groupId>com.octo.captcha</groupId> <artifactId>jcaptcha</artifactId> <version>1.0-SNAPSHOT</version> </dependency> |
Add jcaptcha-all.jar (provided in bin-distribution) and commons-collection-3.2 or greater (not provided see commons collection ) to your application class path, ie in you WEB-INF/lib folder.
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; } } |
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(); } } |
<servlet> <servlet-name>jcaptcha</servlet-name> <servlet-class>ImageCaptchaServlet</servlet-class> <load-on-startup>0</load-on-startup> </servlet> |
And
<servlet-mapping> <servlet-name>jcaptcha</servlet-name> <url-pattern>/jcaptcha</url-pattern> </servlet-mapping> |
Provide a form containing the captcha challenge (the image) and an input text for the response
<img src="/jcaptcha"> <input type='text' name='j_captcha_response' value=''> |
Handle the post (using a servlet, or whatever).
The validateCaptchaForId method will return true if the response is correct.
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 } //do something according to the result! |
Have a look to the modules provided to see how to integrate it with other frameworks : |
Please put some code showing integration with a new framework in a child page of the How To |