ImageServlet简单的图片验证码

package com.utils;

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

import javax.imageio.ImageIO;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
/**
* 创建验证码
* @author fengchen
*
*/
public class ImageServlet extends HttpServlet {
private static final long serialVersionUID = 1L;

public void doGet(HttpServletRequest request, HttpServletResponse response) throws IOException {
    BufferedImage bi = new BufferedImage(68, 22, BufferedImage.TYPE_INT_RGB);// 绘制一张内存中图片
    Graphics g = bi.getGraphics();// 得到画图对象 --- 画笔
    Color c = new Color(200, 150, 255);
    g.setColor(c);
    g.fillRect(0, 0, 68, 22);// 设置矩形区域
    char[] ch = "ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789".toCharArray();
    Random r = new Random();
    int len = ch.length, index;// 定义索引
    StringBuffer sb = new StringBuffer();
    for (int i = 0; i < 4; i++) {// 生成四位随机数
        index = r.nextInt(len);
        g.setColor(new Color(r.nextInt(88), r.nextInt(188), r.nextInt(255)));// 随机颜色
        g.drawString(ch[index] + "", (i * 15) + 3, 18);
        sb.append(ch[index]);
    }
    request.getSession().setAttribute("Client_yzm", sb.toString());
    ImageIO.write(bi, "jpg", response.getOutputStream());// 输出图片
}

}