JSP无刷新验证码

此实现共分三个文件，即：CreatImage.java 生成图像流的类，提供用于生成图片流的方法；images.jsp 图片包装，用于将图片加入到response输出流中；login.jsp 调用前面的jsp，显示验证码。
CreatImage.java 类：
3 import java.awt.Color;
 4 import java.awt.Font;
 5 import java.awt.Graphics;
 6 import java.awt.Image;
 7 import java.awt.image.BufferedImage;
 8 import java.util.Random;
 9
10 import javax.servlet.http.HttpServletRequest;
11 import javax.servlet.http.HttpServletResponse;
12 import javax.servlet.http.HttpSession;
13
14 public class CreatImage{
15   
16     private static final long serialVersionUID = 1L;
17     Image image = null;
18     HttpServletRequest request = null;
19     HttpServletResponse response = null;
20    
21     public CreatImage(HttpServletRequest request, HttpServletResponse response){
22         this.request = request;
23         this.response = response;
24     }
25    
26     public Color getRandColor(int fc,int bc){//给定范围获得随机颜色
27         Random random = new Random();
28         if(fc>255) fc=255;
29         if(bc>255) bc=255;
30         int r=fc random.nextInt(bc-fc);
31         int g=fc random.nextInt(bc-fc);
32         int b=fc random.nextInt(bc-fc);
33         return new Color(r,g,b);
34     }
35    
36     public BufferedImage creatImage(){
37