Servlet生成图片验证码

package com.credit.search.util; 
import java.awt.Color; 
import java.awt.Font; 
import java.awt.Graphics2D; 
import java.awt.image.BufferedImage; 
import java.io.IOException; 
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 com.sun.image.codec.jpeg.JPEGCodec; 
import com.sun.image.codec.jpeg.JPEGImageEncoder; 
/**
* 验证码图片生成Servlet类，直接调用该Servlet即可使用
* 取值的时候调用session.getAttribute("code")得到生成的值
* @author 张龙
* @time 2011-6-26 上午11:21:04
*
*/ 
public class ImageServlet extends HttpServlet { 
        private static final long serialVersionUID = 1L; 
        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 (fc < 0) 
                        fc = 0; 
                if (bc > 255) 
                        bc = 255; 
                if (bc < 0) 
                        bc = 0; 
                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); 
        } 
        @Override 
        protected void service(HttpServletRequest request, 
                        HttpServletResponse response) throws ServletException, IOException { 
                // 设置输出 
                response.setContentType("image/jpeg"); 
                int width = 60; 
                int height = 20; 
                // 产生随机数 
                Random r = new Random(); 
                // 把随机数绘制成图像 
                BufferedImage imgbuf = new BufferedImage(width, height, 
                                BufferedImage.TYPE_INT_RGB);// 产生缓冲图像,40宽20高 
                Graphics2D g = imgbuf.createGraphics();// 取得缓冲的绘制环境 
                // 开始绘制 
                g.setColor(getRandColor(200, 250));// 设定背景色 
                g.fillRect(0, 0, width, height); 
                // 随机产生155条干扰线，使图象中的认证码不易被其它程序探测到 
                g.setColor(getRandColor(160, 200)); 
                for (int i = 0; i < 155; i++) { 
                        int x = r.nextInt(width); 
                        int y = r.nextInt(height); 
                        int xl = r.nextInt(12); 
                        int yl = r.nextInt(12); 
                        g.drawLine(x, y, x + xl, y + yl); 
                } 
                // 随机产生100个干扰点，使图像中的验证码不易被其他分析程序探测到 
                g.setColor(getRandColor(120, 240)); 
                for (int i = 0; i < 100; i++) { 
                        int x = r.nextInt(width); 
                        int y = r.nextInt(height); 
                        g.drawOval(x, y, 0, 0); 
                } 
                g.setFont(new Font("Times New Roman", Font.PLAIN, 18)); 
                String scode = ""; 
                for (int i = 0; i < 4; i++) { 
                        String rand = String.valueOf(r.nextInt(10)); 
                        scode += rand; 
                        g.setColor(new Color(20 + r.nextInt(110), 20 + r.nextInt(110), 
                                        20 + r.nextInt(110))); 
                        // 调用函数出来的颜色相同，可能是因为种子太接近，所以只能直接生成 
                        g.drawString(rand, 13 * i + 6, 16); 
                } 
                request.getSession().setAttribute("code", scode); 
                System.out.println("code------->"+scode); 
                // 输出图像 
                ServletOutputStream out = response.getOutputStream();// 得到HTTP的流 
                // JPEGCodec.createJPEGEncoder(out);转码 
                JPEGImageEncoder encoder = JPEGCodec.createJPEGEncoder(out);// 产生JPEG的图像加码器 
                encoder.encode(imgbuf); 
                out.flush(); 
        } 
} 
Xhtml代码
<img alt="验证码" id="safeCodeImg" src="${ctx}/servlet/ImageServlet" mce_src="${ctx}/servlet/ImageServlet" width="50" height="16"> 
                                <a href="javascript:reloadVerifyCode();" mce_href="javascript:reloadVerifyCode();">看不清楚</a> 
<mce:script type="text/javascript"><!-- 
        // 重载验证码 
        function reloadVerifyCode(){ 
           var timenow = new Date().getTime() ;                        
           document.getElementById("safeCodeImg").src="${ctx}/servlet/ImageServlet?d="+timenow ; 
        } 
     
// --></mce:script> 
Java代码
//1、检测登录信息 
        Object obj = getSession().getAttribute(MyConstants.LOGIN_COMPANY) ;  
        if(obj==null){ 
            return "toCompanyLoginJsp"; 
        } else { 
            companyLogin = (CompanyLogin) obj ; 
            return "loginSuccess" ; 
        }