javaweb servlet 간단 한 인증 코드 생 성

package com.serv;

import java.awt.Color;
import java.awt.Graphics;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.util.Random;

import javax.imageio.ImageIO;
import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
@WebServlet(urlPatterns={"/Servyzm"})
public class Servyzm extends HttpServlet {
  
  @Override
  protected void doGet(HttpServletRequest req, HttpServletResponse resp)
      throws ServletException, IOException {
    // TODO          
    doPost(req, resp);
  }
  @Override
  protected void doPost(HttpServletRequest req, HttpServletResponse resp)
      throws ServletException, IOException {
    // TODO          
    Random r = new Random();
    //       
    BufferedImage buf = new BufferedImage(70, 25, BufferedImage.TYPE_INT_RGB);
    Graphics g = buf.getGraphics();//         
    g.fillRect(0, 0, 70,25);//      (0,0)        , 70, 25
    g.setColor(new Color(150,150,150));//            
    String str = r.nextInt(9000)+1000+"";
    g.drawString(str, 20, 20);// drawString(String str, int x, int y)str        ;x,y           
    for (int i = 0; i < 8; i++) {
      int startx = r.nextInt(120);
      int starty = r.nextInt(30);
      g.setColor(new Color(startx, 232, starty));
      g.drawLine(startx, starty, startx + 10, starty + 10);
    }
    ServletOutputStream out = resp.getOutputStream();//      
    ImageIO.write(buf, "jpg", out);
  }
//  public static int getString(){
//    
//  }
}