servlet 验证码

package com.vnvmall.goldfish.util;

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

import javax.imageio.ImageIO;
import javax.servlet.ServletConfig;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

public class ValidateImage extends HttpServlet
{
        public void init(ServletConfig conf) throws ServletException
        {
                super.init(conf);
        }
       
        public void doGet(HttpServletRequest req,HttpServletResponse res) throws ServletException, IOException
        {       
                res.setContentType("image/jpeg");
                res.setHeader("Pragma","No-cache");
                res.setHeader("Cache-Control","no-cache");
                res.setDateHeader("Expires", 0);
                HttpSession session = req.getSession();
               
                // 在内存中创建图象
                int width=60, height=20;
                BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
               
                // 获取图形上下文
                Graphics g = image.getGraphics();
               
                // 生成随机类
                Random random = new Random();
               
                // 设定背景色
                g.setColor(getRandColor(200,250));
                g.fillRect(0, 0, width, height);
               
                // 设定字体
                g.setFont(new Font("Times New Roman",Font.PLAIN,18));
               
                // 画边框
                //g.setColor(new Color());
                //g.drawRect(0,0,width-1,height-1);
               
                // 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 = random.nextInt(width);
                        int y = random.nextInt(height);
                        int xl = random.nextInt(12);
                        int yl = random.nextInt(12);
                        g.drawLine(x,y,x+xl,y+yl);
                }
               
                // 取随机产生的认证码(4位数字)
                String sRand="";
                for (int i=0;i<4;i++)
                {
                    String rand=String.valueOf(random.nextInt(10));
                    sRand+=rand;
                    // 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)));
                        // 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);
                }
               
                // 将认证码存入SESSION
                session.setAttribute("VerifyCode",sRand);
               
                // 图象生效
                g.dispose();
               
                // 输出图象到页面
                ImageIO.write(image, "JPEG", res.getOutputStream());
                //JPEGImageEncoder encoder = JPEGCodec.createJPEGEncoder(res.getOutputStream());
                //encoder.encode(image);
        }
       
        public void doPost(HttpServletRequest req,HttpServletResponse res) throws ServletException, IOException
        {
                doGet(req,res);
        }
       
        //给定范围获得随机颜色
        private Color getRandColor(int fc,int bc)
        {
                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);
    }
}

评论

1 楼 liyanboss 2007-01-22  

最近在看验证码的问题,很有帮助呀,谢谢呀!!!