package com;

 import java.awt.Color;

 import java.awt.Font;

 import java.awt.Graphics2D;

 import java.awt.image.BufferedImage;

 import java.io.IOException;

 import java.util.Random;

 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.sun.image.codec.jpeg.JPEGCodec;

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

 public class IdentityServlet extends HttpServlet {

     public static final char[] CHARS = { '2', '3', '4', '5', '6', '7', '8',

             '9', '0', 'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K',

             'L', 'M', 'N', 'O', 'P', 'K', 'R', 'S', 'T', 'U', 'V', 'W', 'X',

             'Y', 'Z' };

     public static Random random = new Random();

     public static String getRandomString() {// 随机获取6位

         StringBuffer buffer = new StringBuffer();

         for (int i = 0; i < 6; i++) {

             buffer.append(CHARS[random.nextInt(CHARS.length)]);// 随机获取一个字符

         }

         return buffer.toString();

     }

     public static Color getRandomColor() {

         return new Color(random.nextInt(255), random.nextInt(255),

                 random.nextInt(255));

     }

     public static Color getReverseColor(Color c) {// 取反色

         return new Color(255 - c.getRed(), 255 - c.getGreen(),

                 255 - c.getBlue());

     }

     public void doGet(HttpServletRequest request, HttpServletResponse response)

             throws ServletException, IOException {

         response.setContentType("image/jpeg");

         String randomString = getRandomString();

         request.getSession(true).setAttribute("randomString", randomString);

         int width = 100;

         int height = 30;

         Color color = getRandomColor();

         Color reverseColor = getReverseColor(color);

         BufferedImage bImage = new BufferedImage(width, height,

                 BufferedImage.TYPE_INT_RGB);

         Graphics2D graphics2d = bImage.createGraphics();

         graphics2d.setFont(new Font(Font.SANS_SERIF, Font.BOLD, 16));

         graphics2d.setColor(color);

         graphics2d.fillRect(0, 0, width, height);

         graphics2d.setColor(reverseColor);

         graphics2d.drawString(randomString, 18, 20);

         for (int i = 0, n = random.nextInt(100); i < n; i++) {

             graphics2d.drawRect(random.nextInt(width), random.nextInt(height),

                     1, 1);

         }

         ServletOutputStream outputStream = response.getOutputStream();

         JPEGImageEncoder coder = JPEGCodec.createJPEGEncoder(outputStream);

         coder.encode(bImage);

         outputStream.flush();

     }

 }