中文汉字的验证码

import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.Random;
 
import javax.imageio.ImageIO;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
 
 
public class ChineseCheckCode extends HttpServlet {
 
     
     
    public void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
 
        this.doPost(request, response);
    }
 
     
    public void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        request.setCharacterEncoding("utf-8");
        response.setContentType("text/html;charset=utf-8");
 
        response.setContentType("image/jpeg");
        response.setDateHeader("expries", -1);
        response.setHeader("Cache-Control", "no-cache");
        response.setHeader("Pragma", "no-cache");
        int width=166;
        int height = 80;
        BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_BGR);
        Graphics g=image.getGraphics();
        Random randome = new Random();
        Font myFont = new Font("宋体",Font.ITALIC,26);
        g.fillRect(0, 0, width, height);
        g.setFont(myFont);
        String sRand = "";
        String ctmp = "";
        String itmp = "";
        for(int i=0;i<4;i++){
             
            String[] rBase={"0","1","2","3","4","5","6","7","8","9","a","b","c","d","e","f"};
            int r1=randome.nextInt(3)+11;
            String str_r1=rBase[r1];
            int r2;
            if(r1==13){
                r2=randome.nextInt(7);
            }else{
                r2=randome.nextInt(16);
            }
            String str_r2=rBase[r2];
            int r3=randome.nextInt(6)+10;
            String str_r3=rBase[r3];
            int r4;
            if(r3==10){
                r4=randome.nextInt(15)+1;
            }else if(r3==15){
                r4=randome.nextInt(15);
            }else{
                r4=randome.nextInt(16);
            }
            String str_r4=rBase[r4];
            byte[] bytes = new byte[2];
            String r12=str_r1+str_r2;
            int tempLow=Integer.parseInt(r12, 16);
            bytes[0]=(byte) tempLow;
            String r34=str_r3+str_r4;
            int tempHeigh=Integer.parseInt(r34, 16);
            bytes[1]=(byte) tempHeigh;
            ctmp=new String(bytes);
            sRand+=ctmp;
            Color color = new Color(20+randome.nextInt(110));
            g.setColor(color);
            g.drawString(ctmp, width/6*i+23, height/3);
             
        }
        HttpSession session=request.getSession(true);
        session.setAttribute("randCheckCode", sRand);
        g.dispose();
        ImageIO.write(image, "JPEG", response.getOutputStream());
    }
 
     
     
 
}