How to use jcaptcha image service in our application

How to use jcaptcha image service in our application

How to install it

For maven users, you need to add the following dependency in your pom file.

<dependency>

    <groupId>com.octo.captcha</groupId>

    <artifactId>jcaptcha</artifactId>

    <version>1.0</version>

</dependency>

For without maven2 users

Add jcaptcha-all.jar (provided in bin-distribution) and commons-collection-3.2 or greater  to your application class path, i.e. in your WEB-INF/lib.

Implement a CaptchaService, It must be a singleton

package com.jcaptcha.test;

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

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

public class CaptchaServiceSingleton {

private static ImageCaptchaService instance = new DefaultManageableImageCaptchaService();

    public static ImageCaptchaService getInstance(){

        return instance;

    }

}

Create a servlet for captcha image.

package com.jcaptcha.test;

import java.awt.image.BufferedImage;

import java.io.ByteArrayOutputStream;

import java.io.IOException;

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 com.octo.captcha.service.CaptchaServiceException;

import com.sun.image.codec.jpeg.JPEGCodec;

import com.sun.image.codec.jpeg.JPEGImageEncoder;

public class ImageCaptchaServlet extends HttpServlet {

       private static final long serialVersionUID = 1L;

       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();

    }

}

In web.xml  You can add this as

<?xml version="1.0" encoding="UTF-8"?>

<web-app version="2.5"

       xmlns="http://java.sun.com/xml/ns/javaee"

       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"

       xsi:schemaLocation="http://java.sun.com/xml/ns/javaee

       http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">

  <display-name></display-name>

  <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>    

  <welcome-file-list>

    <welcome-file>index.jsp</welcome-file>

  </welcome-file-list>

</web-app>

In the form you must add this to display captcha image and input text box for submitting

<%@ page language="java" import="java.util.*" pageEncoding="ISO-8859-1"%>

<%

//String path = request.getContextPath();

//String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";

%>

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">

<html>

  <head>

    <title>JCaptcha Index Page</title>

      <meta http-equiv="pragma" content="no-cache">

      <meta http-equiv="cache-control" content="no-cache">

      <meta http-equiv="expires" content="0">   

      <meta http-equiv="keywords" content="keyword1,keyword2,keyword3">

      <meta http-equiv="description" content="How to create Captcha Image Service">

    </head>

 

  <body>

     <img src="jcaptcha">

     <input type='text' name='j_captcha_response' value=''>

  </body>

</html>

For Validation You can Implement validation service as

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            }

The Output are as Below :