Servlet和Image如何做出一个验证码程序的完整版的源码？

马克-to-win： 根据上面程序，我做了一个验证码程序的大概。所有的技术点都已经涵盖了。有兴趣的同学可以自己把完整版的验证码程序做出来。
马克- to-win：马克 java社区：防盗版实名手机尾号： 73203。

例：4.4.4



<%@ page contentType="text/html; charset=GBK"%>
    <script  type="text/javascript">
        function flushcode(){
            var fName=document.getElementById("code").alt;
   //         alert(fName);
            document.getElementById("code").src="MarkToWinServlet"+"?Name="+fName+Math.random();
        }
    </script>
<img id="code" src="MarkToWinServlet" alt="马克-to-win"/>
<button onclick="flushcode()">刷新</button>




package com;
import java.io.IOException;
import java.io.UnsupportedEncodingException;
import java.util.Random;
import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import javax.imageio.ImageIO;
import java.awt.image.BufferedImage;
import java.awt.Graphics;
import java.awt.Color;
import java.awt.Font;
public class ServletHello1 extends HttpServlet {
    public void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        BufferedImage image = new BufferedImage(350, 30,
                BufferedImage.TYPE_INT_RGB);
        Graphics g = image.getGraphics();
        g.setColor(Color.white);
        g.fillRect(0, 0, 350, 30);
        Random r = new Random();
        g.setColor(Color.red);
        for (int i = 0; i < 200; i++) {
            /* @param n the bound on the random number to be returned. Must be
             * positive.
             */
            int x = r.nextInt(350);
            int y = r.nextInt(30);
            /* the following draw a point instead of a line. */
            g.drawLine(x, y, x, y);
        }

       
        String fNameGBK=null;
        String fNameiso = request.getParameter("Name");
        if(fNameiso==null) fNameGBK="马克-to-win初始";
        System.out.println("fNameiso is" + fNameiso);
        if (fNameiso != null) {
            try {
                fNameGBK = new String(fNameiso.getBytes("iso8859-1"), "GBK");
                System.out.println(fNameiso + "" + fNameGBK);
            } catch (UnsupportedEncodingException e) {
                e.printStackTrace();
            }
        }

        // String code="1234";
        HttpSession session = request.getSession();
        session.setAttribute("code", fNameGBK);
        System.out.println("session.getAttribute(code) is"
                + session.getAttribute("code"));
       
       
        g.setColor(Color.black);
        Font font = new Font("黑体", Font.BOLD + Font.ITALIC, 20);
        g.setFont(font);
        g.drawString(fNameGBK, 0, 20);
        ServletOutputStream out = response.getOutputStream();
        ImageIO.write(image, "jpeg", out);
    }
}