Captcha image validation in jsp/servlet

Post date: Jul 21, 2011 3:53:51 AM

Hi i plan to create my own image for doing manual captcha verification. I know it is some what difficult, but when you required security it must to implement our own program.

• Following code able create the captcha image which have 5 character with it. if you required you can change it.

• Once you call this servlet it will create a image of 5 character, then you need to store this captchas text into session for next request verification.

package com.boobalan.training.servlet;

import javax.servlet.*;

import javax.servlet.http.*;

import java.io.*;

import java.awt.image.*;

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

import java.awt.*;

public class ImageServlet extends HttpServlet{

 public void doGet(HttpServletRequest req, HttpServletResponse res)

throws ServletException, IOException{

        //

      res.setContentType("image/jpeg"); //MIME

      //PrintWriter out = res.getWriter(); // writer output

      ServletOutputStream out = res.getOutputStream();

      String str = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ01234567890";

     String captchaText = "";

       // Capture the text have 5 character     

      for(int i=0; i<5 ;i++){

            int rno =(int)(Math.random()*str.length());

            captchaText +=str.charAt(rno);

            }

       //AWT classes. Learn java2D for more efforts Show the Image to user

       BufferedImage image = new BufferedImage(150, 75, BufferedImage.TYPE_INT_RGB);// draw image in memory

      Graphics g = image.getGraphics();//pen

      g.setColor(Color.ORANGE);

      g.fillRect(0,0,150,75);

      g.setColor(Color.BLUE);

      g.setFont(new Font("French Script MT", Font.BOLD, 24));

      g.drawString(captchaText, 70,30);

       JPEGImageEncoder encoder = JPEGCodec.createJPEGEncoder(out);

      encoder.encode(image);

      out.close();

      }

 }