This page demonstrates how to use jcaptcha in your application.
This tutorial uses the CaptchaService and sub components (see Architecture overview).
Add the following dependency to your project POM
<dependency> <groupId>com.octo.captcha</groupId> <artifactId>jcaptcha</artifactId> <version>1.0</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 |