login部分的Random验证码代码，还不够完善...

package mypack.login;

import javax.servlet.*;
import javax.servlet.http.*;
import java.io.*;
import java.awt.*;
import java.awt.image.*;
import java.util.*;
import javax.imageio.*;


public class AuthImg extends HttpServlet {

private static final String CONTENT_TYPE = "text/html; charset=gb2312";
private Font mFont = new Font("Times New Roman", Font.PLAIN, 17);
public void init() throws ServletException {
super.init();
}

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);
}

public void service(HttpServletRequest request,
HttpServletResponse response) throws ServletException,
IOException {
response.setHeader("Pragma", "No-cache");
response.setHeader("Cache-Control", "no-cache");
response.setDateHeader("Expires", 0);
response.setContentType("image/jpeg");

int width = 100, height = 18;
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(1, 1, width - 1, height - 1);
g.setColor(new Color(102, 102, 102));
g.drawRect(0, 0, width - 1, height - 1);
g.setFont(mFont);

g.setColor(getRandColor(160, 200));
for (int i = 0; i < 155; i++) {
int x = random.nextInt(width - 1);
int y = random.nextInt(height - 1);
int xl = random.nextInt(6) + 1;
int yl = random.nextInt(12) + 1;
g.drawLine(x, y, x + xl, y + yl);
}
for (int i = 0; i < 70; i++) {
int x = random.nextInt(width - 1);
int y = random.nextInt(height - 1);
int xl = random.nextInt(12) + 1;
int yl = random.nextInt(6) + 1;
g.drawLine(x, y, x - xl, y - yl);
}

String sRand = "";
for (int i = 0; i < 6; i++) {
int itmp = random.nextInt(26) + 65;
char ctmp = (char) itmp;
sRand += String.valueOf(ctmp);
g.setColor(new Color(20 + random.nextInt(110),
20 + random.nextInt(110),
20 + random.nextInt(110)));
g.drawString(String.valueOf(ctmp), 15 * i + 10, 16);
}

HttpSession session = request.getSession(true);
session.setAttribute("rand", sRand);
g.dispose();
ImageIO.write(image, "JPEG", response.getOutputStream());
}

public void destroy() {
}
}