用java生成一个附加码。

好久没有写个东西了.最近好忙.希望大家能够用的上这个附加码.
/**
*@作者 pxjianke
*@目标 生成附加码，免得别人破解密码
*
*/

import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import javax.servlet.http.HttpServlet;
import java.io.IOException;
import javax.servlet.ServletOutputStream;
import com.sun.image.codec.jpeg.JPEGCodec;
import com.sun.image.codec.jpeg.JPEGImageEncoder;
import java.awt.Font;
import java.awt.image.BufferedImage;
import java.awt.Graphics;
import java.awt.Color;
import com.encrypts.StringEncrypt;

public class AuthImgServlet
extends HttpServlet {

private static final String CONTENT_TYPE = "text/html; charset=UTF-8";
private static char numbersAndLetters[] =
"0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ".toCharArray();
private Font mFont = new Font("Times New Roman", Font.BOLD, 14);
public AuthImgServlet() {
}

//Initialize global variables
public void init() throws ServletException {
}

public void doGet(HttpServletRequest request, HttpServletResponse response) throws
ServletException, IOException {
response.setContentType("image/jpeg");
ServletOutputStream out = response.getOutputStream();
BufferedImage image = new BufferedImage(70, 17, BufferedImage.TYPE_INT_RGB);
Graphics g = image.getGraphics();
g.setColor(Color.WHITE);
g.fillRect(0, 0, 70, 17);
g.setColor(Color.red);
g.setFont(mFont);
String temp=getStringCode(6);
HttpSession hs=request.getSession();
hs.setAttribute("createImage",(new StringEncrypt(temp.toLowerCase())).toString());
for(int i=0;i<6;i++){
g.drawString(temp.substring(i,i+1),i*11+2,14);
}
JPEGImageEncoder encoder = JPEGCodec.createJPEGEncoder(out);
encoder.encode(image);
out.close();
}

private String getStringCode(int len) {
StringBuffer strCode = new StringBuffer();
int nRand = (int) Math.round(Math.random() * 100D);
for (int i = 0; i < len; i++) {
nRand = (int) Math.round(Math.random() * 100D);
strCode.append(numbersAndLetters[nRand % (numbersAndLetters.length - 1)]);
}
return strCode.toString();
}

//Process the HTTP Post request
public void doPost(HttpServletRequest request, HttpServletResponse response) throws
ServletException, IOException {
doGet(request, response);
}

//Clean up resources
public void destroy() {
}
}