Servlet和Image如何做出一个验证码程序的完整版的源码？

本文链接：https://blog.youkuaiyun.com/mark_to_win/article/details/84797752

本文介绍了一种基于Java Servlet的验证码生成方法，包括使用BufferedImage和Graphics类创建带有随机线条的验证码图片，以及通过Servlet实现验证码的刷新机制。读者可学习如何在网页中嵌入验证码并实现动态刷新。

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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。

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 οnclick="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);
        }