jsp的验证码实现

package com.xunfang.demo;

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.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * @title://演示输出验证码
 * @author：阳阳
 * @date: 2015-5-13
 */
public class ServletResponsw1 extends HttpServlet {

    public void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        //创建图片
        int width =120;
        int height = 30;
        BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
        //拿到此图片的画笔
        Graphics g = image.getGraphics();
        
        //设定边框
        g.setColor(Color.blue);
        g.drawRect(0, 0, width, height);
        g.setColor(Color.gray);
        g.fillRect(1, 1, width-2, height-2);
        
        //增加干扰圆点
        Random r = new Random();
        g.setColor(Color.green);
        for (int i = 0; i < 100; i++) {
            g.drawOval(1, 1, r.nextInt(width),r.nextInt(height));
        }
        
        //设定中文
        g.setColor(Color.yellow);
        g.setFont(new Font("楷体", Font.BOLD, 1));
        String s = "增加分析验证码的难IHAVEmoney度可以加30条干扰线中国好声音深圳讯方通信技术有限公司刘德华成龙";
        //输出4个字符
        StringBuffer sb = new StringBuffer();
        for (int i = 0; i <4; i++) {
            char c = s.charAt(r.nextInt(s.length()));
            sb.append(c);
            g.drawString(c+"", 20+20*i+r.nextInt(5)*((i%2)==0?1:-1),20+r.nextInt(5)*((i%2)==0?1:-1));
        }
        request.getSession().setAttribute("code", sb.toString());
    
        ImageIO.write(image, "img", response.getOutputStream());
    }

    public void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        doGet(request, response);
    }

}