jsp验证码——数字

<%@ page language="java" import="java.util.*" pageEncoding="gb2312"%>
<%@ page contentType="image/jpeg" import="java.awt.*,java.awt.image.*,java.util.*,javax.imageio.*" %> 
<%! 
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(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); 
        } 
%> 
<% 
//设置页面不缓存 
response.setHeader("Pragma","No-cache"); 
response.setHeader("Cache-Control","no-cache"); 
response.setDateHeader("Expires", 0); 

// 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