以前积攒的一个用Java程序生成验证码的代码

package com.abc.ufo.util;

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

import javax.imageio.ImageIO;



public class ImageMaker{
    private char map[]={'a','b','c','d','e','f','g','h','i','j','k','l','m','n','o','p','q','r','s','t','u','v','w','x','y','z','1','2','3','4','5','6','7','8','9'};

    public String getImage(int width,int height,OutputStream os){
        BufferedImage image=new BufferedImage(width,height,BufferedImage.TYPE_INT_RGB);
        
        Graphics g=image.getGraphics();
        g.setColor(new Color(0xDCDCDC));
        g.fillRect(0, 0, width, height);
        
        
        
        StringBuilder sb=new StringBuilder();
        for(int i=0;i<4;i++){
            sb.append(map[(int)(map.length*Math.random())]);
        }
        String text=sb.toString();
        
        g.setColor(Color.black);
        g.setFont(new Font("Arial",Font.PLAIN,36));
        
        g.setColor(Color.red);
        String str=text.substring(0,1);
        g.drawString(str, 18, 32);
        
        g.setColor(Color.blue);
        str=text.substring(1,2);
        g.drawString(str, 60, 32);
        
        g.setColor(Color.red);
        str=text.substring(2,3);
        g.drawString(str, 95, 32);
        
        g.setColor(Color.blue);
        str=text.substring(3,4);
        g.drawString(str, 125, 32);
        
        g.setColor(Color.gray);
        Random rand=new Random();
        for(int i=0;i<20;i++){
            int x=rand.nextInt(width);
            int y=rand.nextInt(height);
            g.drawOval(x, y, width, height);
        }
        
        g.setColor(Color.black);
        g.drawRect(0, 0, width-1, height-1);
        //g.drawLine(width-2, 0, width-2, height);
        
        g.dispose();
        
        try{
            ImageIO.write(image, "JPEG", os);
        }catch(Exception e){
            //e.printStackTrace();
        }
        
        return text;
    }
}

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%@ page contentType="image/jpeg" %>
<jsp:useBean id="image" scope="page" class="com.abc.ufo.util.ImageMaker"/>

<%
    String str=image.getImage(160,40,response.getOutputStream());
    session.setAttribute("verifyCode",str);
    out.clear();  
    out = pageContext.pushBody(); 
%>

<div class="page-container">
            <logic:present name="error">
                 <h2><bean:write name="error"/></h2>
            </logic:present>
                        
            <h1>Login</h1>
            <form action="login.html" method="post">
                <input type="text" id="usernameTxt" name="username" class="username" placeholder="Username">
                <input type="password" id="passwordTxt" name="password" class="password" placeholder="Password">
                <input type="text" id="verifyCodeTxt" name="verifyCode" class="verifyCode" placeholder="Verification code">
                <p><br/>No Zero in the verification code</p>
                <img src="pages/user/login/image.jsp"/> <!-- 这个路径就是前面jsp的路径 -->
                <button id="submitBtn">Sign me in</button>
                <div class="error"><span>+</span></div>
            </form>
            <div class="connect" style="display:none">
                <p>Or connect with:</p>
                <p>
                    <a class="facebook" href=""></a>
                    <a class="twitter" href=""></a>
                </p>
            </div>
        </div>