capacha

Hi All ,
I am trying to implement capatcha in jsp application , using jcapatcha : i have the following

web.xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" id="WebApp_ID" version="2.5">
  <display-name>jcapachaExample</display-name>
  <welcome-file-list>
    <welcome-file>index.html</welcome-file>
    <welcome-file>index.htm</welcome-file>
    <welcome-file>index.jsp</welcome-file>
    <welcome-file>default.html</welcome-file>
    <welcome-file>default.htm</welcome-file>
    <welcome-file>default.jsp</welcome-file>
  </welcome-file-list>
  
  <servlet>
        <servlet-name>jcaptcha</servlet-name>
        <servlet-class>capacha.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>
</web-app>

index.jsp

CaptchaServiceSingleton.java

ImageCaptchaServlet.java

package capacha;
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();
    }
}

when calling servlet jcapacha , i am getting null pointer

any suggestion how to implement it .

So which object is null? And in which line of code does the exception happen?

Thansk for your reply,

exeception happened in this line :

Ulf Dittmer wrote:So which object is null?

challenge or jpegEncoder? Once you know which one it is, check the javadocs of all methods you're calling to create these objects to learn under which circumstances they might return null.

I am just gussing but it looks like challenge is null which is returned by the method you created.

Hi Thanks All for the replies

After long search and checking , I have found the exact Problem .

By the way i was using openjdk I was getting the the null pointer exception (jpegEncoder was null) but i have tested the same code using sun jkd and it works fine .

the got the tip from :

OpenJDK does not have a native JPEG encoder, try using Sun's JDK, or using a library (such as JAI

AFAIK, regarding the "pinkish tint", Java saves the JPEG as ARGB (still with transparency information). Most viewers, when opening, assume the four channels must correspond to a CMYK (not ARGB) as thus the red tint.

If you import the image back to Java, the transparency is still there, though.

from the link

my question now is How to implement that using jai so that i could run it using openjdk

If you're just trying to read or write a JPEG image, use the ImageIO class - it is available on all JDKs. That's much preferable to using JAI. If you're doing something else, tell us in more detail what that is.

Thanks Ulf Dittmer ,

I am creating image for the capacha purpose , by the way I have already post the related code in my first post.

Any suggestion