Captcha Java JSP - J2EE

JSP que genera el codigo Captcha, que le he puesto el nombre "cap3.jsp"

no olvidar importar

@ page import="java.util.*"
@ page import="java.io.*"
@ page import="javax.servlet.*"
@ page import="javax.servlet.http.*"
@ page import="java.awt.*"
@ page import="java.awt.image.*"
@ page import="javax.imageio.*"
@ page import="java.awt.geom.*"

Codigo jsp

response.setContentType("image/jpg");

 try {
   
   Color backgroundColor = Color.orange;
   Color borderColor = Color.red;
   Color textColor = Color.white;
   Color circleColor = new Color(160,160,160);
   Font textFont = new Font("Arial", Font.PLAIN, 24);
   int charsToPrint = 6;
   int width = request.getParameter("width") != null ? Integer.parseInt(request.getParameter("width")) : 150;
   int height = request.getParameter("height") != null ? Integer.parseInt(request.getParameter("height")) : 40;
   int circlesToDraw = 4;
   float horizMargin = 20.0f;
   float imageQuality = 0.95f; // max is 1.0 (this is for jpeg)
   double rotationRange = 0.7; // this is radians
   BufferedImage bufferedImage = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);

   Graphics2D g = (Graphics2D) bufferedImage.getGraphics();

   //Draw an oval
   g.setColor(Color.gray);
   g.fillRect(0, 0, width, height);

   // lets make some noisey circles
   g.setColor(circleColor);
   for ( int i = 0; i < circlesToDraw; i++ ) {
     int circleRadius = (int) (Math.random() * height / 2.0);
     int circleX = (int) (Math.random() * width - circleRadius);
     int circleY = (int) (Math.random() * height - circleRadius);
     g.drawOval(circleX, circleY, circleRadius * 2, circleRadius * 2);
   }

   g.setColor(textColor);
   g.setFont(textFont);

   FontMetrics fontMetrics = g.getFontMetrics();
   int maxAdvance = fontMetrics.getMaxAdvance();
   int fontHeight = fontMetrics.getHeight();

   // i removed 1 and l and i because there are confusing to users...
   // Z, z, and N also get confusing when rotated
   // 0, O, and o are also confusing...
   // lowercase G looks a lot like a 9 so i killed it
   // this should ideally be done for every language...
   // i like controlling the characters though because it helps prevent confusion
   String elegibleChars = "ABCDEFGHJKLMPQRSTUVWXYabcdefhjkmnpqrstuvwxy23456789";
   char[] chars = elegibleChars.toCharArray();

   float spaceForLetters = -horizMargin * 2 + width;
   float spacePerChar = spaceForLetters / (charsToPrint - 1.0f);

   AffineTransform transform = g.getTransform();

   StringBuffer finalString = new StringBuffer();

   for ( int i = 0; i < charsToPrint; i++ ) {
     double randomValue = Math.random();
     int randomIndex = (int) Math.round(randomValue * (chars.length - 1));
     char characterToShow = chars[randomIndex];
     finalString.append(characterToShow);

     // this is a separate canvas used for the character so that
     // we can rotate it independently
     int charImageWidth = maxAdvance * 2;
     int charImageHeight = fontHeight * 2;
     int charWidth = fontMetrics.charWidth(characterToShow);
     int charDim = Math.max(maxAdvance, fontHeight);
     int halfCharDim = (int) (charDim / 2);

     BufferedImage charImage = new BufferedImage(charDim, charDim, BufferedImage.TYPE_INT_ARGB);
     Graphics2D charGraphics = charImage.createGraphics();
     charGraphics.translate(halfCharDim, halfCharDim);
     double angle = (Math.random() - 0.5) * rotationRange;
     charGraphics.transform(AffineTransform.getRotateInstance(angle));
     charGraphics.translate(-halfCharDim,-halfCharDim);
     charGraphics.setColor(textColor);
     charGraphics.setFont(textFont);

     int charX = (int) (0.5 * charDim - 0.5 * charWidth);
     charGraphics.drawString("" + characterToShow, charX, 
                            (int) ((charDim - fontMetrics.getAscent()) 
                                   / 2 + fontMetrics.getAscent()));

     float x = horizMargin + spacePerChar * (i) - charDim / 2.0f;
     int y = (int) ((height - charDim) / 2);
//System.out.println("x=" + x + " height=" + height + " charDim=" + charDim + " y=" + y + " advance=" + maxAdvance + " fontHeight=" + fontHeight + " ascent=" + fontMetrics.getAscent());
     g.drawImage(charImage, (int) x, y, charDim, charDim, null, null);

     charGraphics.dispose();
   }

   //Write the image as a jpg
   Iterator iter = ImageIO.getImageWritersByFormatName("JPG");
   if( iter.hasNext() ) {
     ImageWriter writer = (ImageWriter)iter.next();
     ImageWriteParam iwp = writer.getDefaultWriteParam();
     iwp.setCompressionMode(ImageWriteParam.MODE_EXPLICIT);
     iwp.setCompressionQuality(imageQuality);
     writer.setOutput(ImageIO.createImageOutputStream(response.getOutputStream()));
     IIOImage imageIO = new IIOImage(bufferedImage, null, null);
     writer.write(null, imageIO, iwp);
   } else {
     throw new RuntimeException("no encoder found for jsp");
   }

   // let's stick the final string in the session
   System.out.println("finalString.toString() :"+finalString.toString());
   request.getSession().setAttribute("captcha", finalString.toString());

   g.dispose();
 } catch (IOException ioe) {
   throw new RuntimeException("Unable to build image" , ioe);
 }

Ahora vamos a mostrar la imagen generada en otro JSP llamado "index.jsp" para validar el valor de la imagen con el que ha sido ingresado en el caja de texto implementamos un scriptlet en el JSP (index.jsp) algo como esto.

< %

String msg="";
String secHash ="";
String originalHash="";
String seccode = request.getParameter ("seccode");
System.out.println("Valor caja texto : "+seccode);
if(!(seccode == null || seccode.equals("null"))){
  originalHash=(String)session.getAttribute("captcha"); 
  System.out.println("Valor de captcha sesion : "+originalHash);
  secHash = seccode;
 
 if(originalHash.equals(secHash)){
  msg="Correcto ";
 }else{
  msg="Error ";
 }
}
% >

Agregamos un form con la caja de texto y una etiqueta img

 
 
   <%=msg%>

Probando el Captcha
Resultado que se muestra en el JSP "index.jsp"