package cn.com.lough.struts.action;

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.struts.action.Action;
import org.apache.struts.action.ActionForm;
import org.apache.struts.action.ActionForward;
import org.apache.struts.action.ActionMapping;
import org.apache.commons.lang.RandomStringUtils;

/**
* MyEclipse Struts Creation date: 01-11-2007
*
* XDoclet definition:
*
* @struts.action validate="true"
*/
public class ValidatecodeAction extends Action {
 /*
  * Generated Methods
  */

 /**
  * Method execute
  *
  * @param mapping
  * @param form
  * @param request
  * @param response
  * @return ActionForward
  */
 public ActionForward execute(ActionMapping mapping, ActionForm form,
     HttpServletRequest request, HttpServletResponse response) {
   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("validateCode", 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);
 }
}



jsp页面的调用
<html:img page="/validatecode.do" border="0" onclick="this.src='/validatecode.do'" alt="请输入此验证码，如看不清请点击刷新。" style="cursor:pointer" />