servlet产生验证码的代码

package com.mapabc.servlet.login;import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.image.BufferedImage;
import java.io.OutputStream;
import java.util.Random;import javax.imageio.ImageIO;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;public class ImageGenerator extends HttpServlet { private static Color getRandColor(int fc, int bc) {
  Random random = new Random();
  if (fc > 255)
   fc = 255;
  if (bc > 255)
   bc = 255;
  int r = fc + random.nextInt(bc - fc);
  int g = fc + random.nextInt(bc - fc);
  int b = fc + random.nextInt(bc - fc);
  return new Color(r, g, b);
 } private static String charsLong = "23456789abcdefghjklmnpqrstuvwxyzABCDEFGHIJKLMNPQRSTUVWXYZ"; private static String charsShort = "0123456789"; private static String chars = charsLong; @Override
 public void service(HttpServletRequest request, HttpServletResponse response) {
  try {
   int charsLength = chars.length();   response.setHeader("Pragma", "No-cache");
   response.setHeader("Cache-Control", "no-cache");
   response.setDateHeader("Expires", 0);   int width = 70, height = 20;
   BufferedImage image = new BufferedImage(width, height,
     BufferedImage.TYPE_INT_RGB);   Graphics g = image.getGraphics();   Random random = new Random();   g.setColor(getRandColor(200, 250));
   g.fillRect(0, 0, width, height);   g.setFont(new Font("Times New Roman", Font.ITALIC, height));   /*g.setColor(getRandColor(160, 200));
   for (int i = 0; i < 35; i++) {
    int x = random.nextInt(width);
    int y = random.nextInt(height);
    int xl = random.nextInt(12);
    int yl = random.nextInt(12);
    g.drawLine(x, y, x + xl, y + yl);
   }*/   StringBuilder sRand = new StringBuilder();
   String[] fontNames = { "Times New Roman", "Arial", "Book antiqua",
     "" };   for (int i = 0; i < 4; i++) {
    g.setFont(new Font(fontNames[random.nextInt(3)], Font.ITALIC,
      height));
    char rand = chars.charAt(random.nextInt(charsLength));
    sRand.append(rand);    g.setColor(new Color(20 + random.nextInt(110), 20 + random
      .nextInt(110), 20 + random.nextInt(110)));
    g.drawString(String.valueOf(rand), 16 * i + random.nextInt(6)
      + 3, height - random.nextInt(4));
   }   /*g.setColor(getRandColor(160, 200));
   for (int i = 0; i < 30; i++) {
    int x = random.nextInt(width);
    int y = random.nextInt(height);
    int xl = random.nextInt(width);
    int yl = random.nextInt(width);
    g.drawLine(x, y, x + xl, y + yl);
   }*/   request.getSession().setAttribute("Login_Image_Code",
     sRand.toString());   g.dispose();   OutputStream os = response.getOutputStream();
   ImageIO.write(image, "JPEG", os);
   os.flush();
   os.close();
  } catch (Exception ex) {
   ex.printStackTrace();
   // TODO
  }
 }
}