java验证码

 package cn.edu.pdsu.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.commons.lang.RandomStringUtils;
 import org.apache.struts2.ServletActionContext;

 /**
  * 类说明：验证码类（将验证码信息写入到session中 属性“authCode”）
  *
  * @author 作者: LiuJunGuang
  * @version 创建时间：2011-7-17 下午03:26:21
  */
 public class AuthCodeAction {
     private HttpServletResponse response = ServletActionContext.getResponse();
     private HttpServletRequest request = ServletActionContext.getRequest();

     public String execute() {
         try {
             int width = 50;
             int height = 20;
             // 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");//告知浏览器内容的类型
             response.setHeader("Pragma", "No-cache");//HTTP 1.0版 不要缓存
             response.setHeader("Cache-Control", "no-cache"); //HTTP 1.1  不要缓存
             response.setDateHeader("Expires", 0);//设置存活时间

             ServletOutputStream out = response.getOutputStream();//得到响应输出流
             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 < 125; 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);
             }
             // 绘制一些长的干扰线
             for (int i = 0; i < 5; i++) {
                 int y1 = random.nextInt(15) + 3;
                 g.drawLine(0, y1, width, y1);
                 g.setColor(getRandColor(10, 160));
             }

             // 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);//将图片以JPEG格式输出到out输出流中
             out.close();
         } catch (Exception e) {
             e.printStackTrace();
         }
         return null;
     }

     //获得某一范围的随机颜色
     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);
     }
 }