JSP ile özel dogrulama kodu implementasyon örneği ve değerleri

import java.awt.Color; 
import java.awt.Font; 
import java.awt.FontMetrics; 
import java.awt.Graphics2D; 
import java.awt.geom.AffineTransform;
 import java.awt.image.BufferedImage;
 import java.io.IOException;
 import java.util.Iterator;
 import java.util.logging.Level;
 import java.util.logging.Logger; 
import javax.imageio.IIOImage;
 import javax.imageio.ImageIO;
 import javax.imageio.ImageWriteParam;
 import javax.imageio.ImageWriter;
 import javax.servlet.http.HttpServletRequest;
 import javax.servlet.http.HttpServletResponse; 
 /* * To change this template, choose Tools | Templates * and open the template in the editor.
 */ 
/** 
* * [MENTION=21475]AuthoR[/MENTION] turgay 
*/   

 public class MyReCaptcha {
  public MyReCaptcha(HttpServletRequest request, HttpServletResponse response) {  
 String imageFormat = "jpg"; 
response.setContentType("image/" + imageFormat); 
 try {
 // Imaj Ozellikleri  
Color backgroundColor = Color.BLUE; 
//Arka Plan rengi 
Color borderColor = Color.black; 
//Kenarlık Rengi Color textColor = Color.white; 
// Yazi rengi 
Font textFont = new Font("Arial", Font.PLAIN, paramInt(request, "fontSize", 20)); 
//Yazi tipi
 int charsToPrint = 6; 
//Yazi boyutu
 int width = paramInt(request, "width", 100);
 //imaj genisliği
 int height = paramInt(request, "height", 30);
 //imaj yüksekliği 
float horizMargin = 20.0f; 
//yatak bosluk
 float imageQuality = 0.95f;
 // Imaj kalitesi(Maksimum deger 1.0)
 double rotationRange = 0.7; 
// Yazılarin ekrandaki durusu (Donus deger aralıgı)  
BufferedImage bufferedImage = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB); 
 Graphics2D g = (Graphics2D) bufferedImage.getGraphics();  g.setColor(backgroundColor);
 g.fillRect(0, 0, width, height); 
 g.setColor(textColor);
 g.setFont(textFont); 
 FontMetrics fontMetrics = g.getFontMetrics();
 int maxAdvance = fontMetrics.getMaxAdvance();
 int fontHeight = fontMetrics.getHeight();  
String elegibleChars = "ABCDEFGHJKLMPQRSTUVWXYabcdefhjkmnpqrstuvwxy234567 89";
 char[] chars = elegibleChars.toCharArray(); 
 float spaceForLetters = -horizMargin * 2 + width; 
float spacePerChar = spaceForLetters / (charsToPrint - 1.0f); 
 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); 
 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.getRotateIn stance(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);
 g.drawImage(charImage, (int) x, y, charDim, charDim, null, null); 
 charGraphics.dispose();
 } 
 g.setColor(borderColor);
g.drawRect(0, 0, width - 1, height - 1); 
 Iterator iter = ImageIO.getImageWritersByFormatName(imageFormat);
 if (iter.hasNext()) { 
try
 { 
ImageWriter writer = (ImageWriter) iter.next(); 
ImageWriteParam iwp = writer.getDefaultWriteParam();
 if (imageFormat.equalsIgnoreCase("jpg") || imageFormat.equalsIgnoreCase("jpeg")) { 
iwp.setCompressionMode(ImageWriteParam.MODE_EXPLIC IT); 
iwp.setCompressionQuality(imageQuality); 
}
 writer.setOutput(ImageIO.createImageOutputStream(r esponse.getOutputStream()));
 IIOImage imageIO = new IIOImage(bufferedImage, null, null);
 writer.write(null, imageIO, iwp); 
} catch (IOException ex) { 
Logger.getLogger(MyReCaptcha.class.getName()).log( Level.SEVERE, null, ex);
 } 
} else {
 throw new RuntimeException("no encoder found for jsp"); 
} 
 request.getSession().setAttribute("captcha", finalString.toString()); 
 // Dogrulama kodunun dogrulugunu test icin session ataması  g.dispose(); } catch (Exception ioe) { 
throw new RuntimeException("Unable to build image", ioe);
 } 
 } 
 public static String paramString(HttpServletRequest request, String paramName,  String defaultString) {
 return request.getParameter(paramName) != null ?  request.getParameter(paramName) : defaultString;
 }  
public static int paramInt(HttpServletRequest request, String paramName,  int defaultInt) {
 return request.getParameter(paramName) != null ?  Integer.parseInt(request.getParameter(paramName)) : defaultInt; 
} 
}