第一步：编写验证码的Action

package com;import java.awt.Color;import java.awt.Font;import java.awt.Graphics;import java.awt.image.BufferedImage;import java.util.Random;import javax.imageio.ImageIO;import javax.servlet.ServletOutputStream;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;import javax.servlet.http.HttpSession;import org.apache.commons.lang.RandomStringUtils;import org.apache.struts2.ServletActionContext;public class AuthCodeAction {	private HttpServletResponse response = ServletActionContext.getResponse();	private HttpServletRequest request = ServletActionContext.getRequest();	public String execute() {		try {			int width = 50;			int height = 18;			// 取得一个4位随机字母数字字符串			String s = RandomStringUtils.random(4, true, true);			// 保存入session,用于与用户的输入进行比较.			// 注意比较完之后清除session.			HttpSession session = request.getSession(true);			session.setAttribute("authCode", s);			response.setContentType("images/jpeg");			response.setHeader("Pragma", "No-cache");			response.setHeader("Cache-Control", "no-cache");			response.setDateHeader("Expires", 0);			ServletOutputStream out = response.getOutputStream();			BufferedImage image = new BufferedImage(width, height,					BufferedImage.TYPE_INT_RGB);			Graphics g = image.getGraphics();			// 设定背景色			g.setColor(getRandColor(200, 250));			g.fillRect(0, 0, width, height);			// 设定字体			Font mFont = new Font("Times New Roman", Font.BOLD, 18);// 设置字体			g.setFont(mFont);			// 画边框			// g.setColor(Color.BLACK);			// g.drawRect(0, 0, width - 1, height - 1);			// 随机产生干扰线，使图象中的认证码不易被其它程序探测到			g.setColor(getRandColor(160, 200));			// 生成随机类			Random random = new Random();			for (int i = 0; i < 155; i++) {				int x2 = random.nextInt(width);				int y2 = random.nextInt(height);				int x3 = random.nextInt(12);				int y3 = random.nextInt(12);				g.drawLine(x2, y2, x2 + x3, y2 + y3);			}			// 将认证码显示到图象中			g.setColor(new Color(20 + random.nextInt(110), 20 + random					.nextInt(110), 20 + random.nextInt(110)));			g.drawString(s, 2, 16);			// 图象生效			g.dispose();			// 输出图象到页面			ImageIO.write((BufferedImage) image, "JPEG", out);			out.close();		} catch (Exception e) {			e.printStackTrace();		}		return null;	}	private Color getRandColor(int fc, int bc) { // 给定范围获得随机颜色		Random random = new Random();		if (fc > 255)			fc = 255;		if (bc > 255)			bc = 255;		int r = fc + random.nextInt(bc - fc);		int g = fc + random.nextInt(bc - fc);		int b = fc + random.nextInt(bc - fc);		return new Color(r, g, b);	}}

第三步：编写jsp页面（采用jquery实现动态刷新）

<%@ page language="java" import="java.util.*" pageEncoding="GB18030"%><%String path = request.getContextPath();String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";%>          		        
      		 
     
  		 
        		
     看不清，换一张！